OTC: TSEOF

We have manufacturing and production operations around the world, which allow us to serve our global customer base. As of December 31, 2025, our production facilities included manufacturing plants and one recycling facility at sites across the globe, including the Company’s joint venture, Americas Styrenics LLC. Additionally, as of December 31, 2025, we operated 11 research and development (“R&D”) facilities globally, including technology and innovation development centers, which we believe are critical to our global presence and innovation capabilities. Our global operations also provide diversity in the end markets for our products.

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Our Strategy

In 2025, we continued to focus our efforts and investments on specialty materials and sustainable solutions product offerings which are less cyclical and offer higher growth and margin potential. We have invested in differentiated and sustainable product offerings serving the applications within our compounding business segments, as well as coatings, adhesives, sealants, and elastomers (“CASE”) applications within the Latex Binders business segment, while closing underperforming or unprofitable product lines to focus on improving cash flow.

We have capabilities to convert post-consumer and post-industrial waste for use in a wide range of high-end applications. We have a polycarbonate (“PC”) dissolution pilot facility in our Terneuzen, the Netherlands plant, a polymethyl methacrylates (“PMMA”) depolymerization plant in Rho, Italy and an acrylonitrile butadiene styrene (“ABS”) dissolution pilot facility in Terneuzen, the Netherlands. These facilities demonstrate our commitment to sustainability and progress toward our sustainable product portfolio goals.

In the face of ongoing challenges affecting the chemical industry and the end markets which we serve, including historically low demand, geopolitical turmoil, and pricing volatility, we have implemented multiple restructuring initiatives including product line shutdowns and workforce reductions which are designed to reduce costs, streamline commercial and operational activities, improve profitability and cash flow generation. We have also taken steps to further reduce our exposure to cyclical markets and strengthen our competitive position through the closure of certain underperforming or uncompetitive plants and product lines and exit from underperforming assets. These steps included the closure of our global styrene manufacturing operations and closure of our virgin polycarbonate manufacturing and polycarbonate plant at our Stade, Germany facility, the closure of our methyl methacrylate (MMA) production operations in Rho, Italy and the related acetone cyanohydrin (ACH) production operations in Porto Marghera, Italy, and polystyrene (“PS”) production operations in Schkopau, Germany. Following these actions, our downstream styrene, polycarbonate, and MMA needs will be purchased from external suppliers. We also have right sized the workforce as a result of the combination of management and supporting functions of our Engineered Materials, Plastics Solutions and Polystyrene businesses.

The Company continues to seek organic growth through expansion into key markets or strategic capital investments targeting technologies and solutions that meet the evolving needs of our customers, and to continue to provide innovative products to our customers who seek our technological and development capabilities to create specialty grades, new and sustainable products, and technologically-differentiated formulations. The Company will continue to focus on growing margins and reducing earnings volatility through such organic investments.

We continue to evaluate strategic alternatives to divest all or a portion of our styrenics businesses, which includes our polystyrene business and our interest in Americas Styrenics LP. In 2024, we announced our interest to sell our share in Americas Styrenics pursuant to an ownership exit provision in the joint venture agreement. The styrenics business separation remains an integral part of our long-term strategy, and we continue to evaluate actions to transform the Company into a higher growth, higher margin and less cyclical specialty and sustainable materials provider.

For more information regarding our strategic highlights see Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations – 2025 Highlights.

Business Segments

The Company operates under four reportable segments: Engineered Materials, Latex Binders, Polymer Solutions, and Americas Styrenics. Our reportable segments reflect the model under which the business is being managed and results are being reviewed by the Chief Executive Officer, who is the Company’s chief operating decision maker.

For additional information regarding business segment results, refer to Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations and Note 23 in the consolidated financial statements.

Engineered Materials Segment

Overview

Our Engineered Materials segment consists of rigid thermoplastic compounds and blends products sold into high growth and high value applications in markets such as consumer electronics, medical and automotive, as well as soft thermoplastic elastomers (“TPEs”) products which are sold into markets such as footwear and automotive. The

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Engineered Materials segment also includes polymethyl methacrylates (“PMMA”) and activated methyl methacrylates (“MMA”) products, which are sold into a variety of applications including automotive, building and construction, medical, consumer electronics, and wellness, among others. During fourth quarter 2025 we ceased MMA production operations in Rho, Italy and ACH production operations in Porto Marghera, Italy. Going forward, all MMA will be purchased from third parties through a combination of long-term supply contracts and spot market purchases.

In 2025, approximately 34% of total Engineered Materials net sales were generated in Europe, approximately 45% were generated in the United States, and approximately 14% were generated in Asia.

Products and End Uses

Products in the Engineered Materials segment are split into rigid compounds, soft plastic compounds, and PMMA resins and sheets. Rigid compounds include PC compounds, ABS compounds, and PC blends, mostly PC/ABS, and support primarily the automotive, consumer electronics and medical markets for equipment housing applications. Thermoplastic elastomer (“TPE”) soft plastic compounds are focused on supporting footwear shoe sole applications, personal care, consumer electronics, and automotive high-end applications such as overmolds, sealings, tubing, and films. PMMA products can be sold as resin compounds or sheets produced through continuous-cast, extrusion, and cell-cast processes. PMMA products are sold primarily into building & construction, automotive, medical and consumer goods applications.

The benefit of Trinseo’s portfolio in our Engineered Materials segment is the high level of customization for high-end applications at selected premium brand owners and clear orientation to sustainable solutions. Our current portfolio includes sustainable solutions, such as high-content post-consumer recycled (“PCR”) polycarbonate and bio-based raw materials. We continue to develop solutions to expand our sustainable offering using PCR ABS, PCR TPE, PCR PMMA and recycled MMA (“R-MMA”) which is chemically recycled. Sustainable products represented 5% of Engineered Materials segment volume in 2025 and are a core growth area.

Compounding. Our compounding products consist of PC/ABS compounds, PC blends, and PC and polypropylene compounds. In 2025, compounding products represented approximately 29% of total segment net sales.

We have a significant position in PC/ABS blends, which combine the heat resistance and impact strength of PC with the easy-to-process qualities and resilience of our ABS. We have also developed compounds containing PCR content in their products.

We sell our compounds products mainly under the EMERGE brand for consumer electronics, and under the CALIBRE brand for medical markets. For the automotive industry, we manufacture PC/ABS blends under the PULSE brand, and we innovate collaboratively with our customers to develop performance solutions to meet industry needs, such as reducing the weight of vehicles or providing products using recycled or sustainable content. We sell our PMMA products primarily under PLEXIGLAS in the United States and ALTUGLAS in Europe and Asia. As a result, we are a key supplier of these products to leading automotive companies in North America and Europe, who tend to specify these products on a per car platform basis, making it difficult to be displaced as a supplier once selected and providing us with relatively stable and predictable cash flows for several years during the production lifecycle. We have an established position in China and are working to further increase our presence in Asia.

We foresee growth in applications of building & construction, consumer goods, and automotive as well as continued initiatives toward light-weighting, paint replacement and digitization. Supported by current macro trends, we believe that we have additional growth opportunities in existing consumer electronics applications, including tablets, notebooks, smart phones and other handheld devices, as well as new voice control systems, home entertainment and delivery equipment. We also foresee growth in medical wearables, home equipment, and drug delivery devices. In serving these markets, we leverage our polymer and compound technologies to meet increasingly stringent performance requirements along with our customers’ aesthetic and color-matching requirements, which are crucial characteristics for the products involved.

We sell our PMMA sheet products primarily under the trade names ALTUGLAS, PLEXIGLAS, ACRYSPA, AVONITE and STUDIO. We foresee growth in wellness applications such as hot tubs and swim spas as well as sanitary applications like bathtubs. More specifically, we are able to effectively serve these markets through our specialized continuous cast sheet production capabilities that allow us to provide large scale PMMA sheet with specific color

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requirements. We have also expanded our product offerings into transportation applications and continue to provide customer solutions in architectural applications such as signage and countertops.

We manufacture our TPE soft plastic compounds principally under the trade names MEGOL, APILON, APIGO, and APINAT. Growth in footwear is supported by bio thermoplastic polyurethane solutions in both luxury and sport premium markets, while automotive growth is orientated to hygienic interiors and both robust and smart surfaces.

Competition and Customers

Our main competitors are Sabic, Covestro, Styrolution, Shanghai Pret Composites Co. Ltd., LG Chem, Lotte Chemical Corporation, and Kingfa for compound technologies, Kraiburg, Celanese, Avient, Hexpol and BASF for TPEs, and Roehm, Plaskolite, Mitsubishi Chemicals and Schweiter Technologies for PMMA resins and sheets.

We compete in the Engineered Materials segment primarily based on our ability to offer differentiated, sustainable and reliable products, high quality customer service, and deep relationships with prioritized customers. We believe that growth in this segment will stem from the continued high demand for engineered and sustainable product solutions serving the consumer electronics, automotive, building & construction, wellness, footwear, medical and lighting application markets. We believe our track record of innovation and our focus on differentiated products enhances our growth prospects in this segment. We also believe that our global organization and facilities are a competitive advantage that allows us to provide customers with consistent grades across different regions and positions us to strategically serve emerging markets.

Seasonality

Due to the steady demand state of a portfolio of applications in many markets, such as consumer electronics, medical devices, footwear, rigid compounds and soft TPE products do not experience significant seasonality. PMMA and compound applications geared towards automotive, building and construction and wellness markets do experience some seasonality.

Latex Binders Segment

Overview

In 2025, approximately 41% of our Latex Binders segment’s sales were generated in Europe, 35% were generated in the United States, and the majority of the remaining net sales were generated in Asia. Additionally, this segment includes the results of our styrene-acrylate latex (“SA latex”) and all-acrylic latex (“AA latex”) production facilities and related infrastructure in the United States, Europe and Asia. The Company’s key area of focus in the Latex Binders segment is to grow our product offerings serving CASE and battery applications, as these offer significantly higher growth and margin potential.

Products and End Uses

SB latex is widely used as a binder for mineral pigments as it allows high coating speeds, improved smoothness, higher gloss level, opacity and water resistance that is valued in the product’s end use in advertising, magazines, and packaging board coatings.

We offer a diverse range of latex binders products to the carpet and artificial turf market for use in residential and commercial applications. We produce SB latex, SA latex, vinylidene chloride, and butadiene-methacrylate latex products for the commercial and niche carpet markets. SB latex is also used in flooring as an adhesive for carpet and artificial turf fibers. We continue to implement new chemistries for paper coating and carpet backing applications.

We also offer a broad range of performance latex binders products, including SB latex, SA latex, and vinylidene chloride latex for CASE applications. Net sales to CASE applications made up approximately 17% of total Latex Binders net sales in 2025.

Competition and Customers

Our principal competitors in our Latex Binders segment include BASF Group and Synthomer plc. In this segment, we compete primarily based on our ability to offer differentiated and reliable products, the quality of our customer

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service, and the length and depth of our relationships. This industry has seen capacity reduction and consolidation which we believe could positively impact our competitive standing.

We believe our Latex Binders segment is able to differentiate itself by offering customers value-added formulations and product development expertise. Our R&D team and Technical Services and Development (“TS&D”) team are able to use our pilot coating facility, paper fabrication and testing labs, carpet technology centers located near carpet producers, and product development and process research centers to assist customers in designing new products and enhancing their manufacturing processes. Many of our major customers rely on our dedicated R&D and TS&D teams to complement their limited in-house resources for formulation and reformulation tests and trials. We believe that this capability allows us to capture new business, strengthen our existing customer relationships and broaden our technological expertise.

Additionally, our global manufacturing footprint is key in allowing us to serve our customers in a cost-effective manner, as latex binders products are costly to ship over long distances due to their high water content. We believe that our global network of service and manufacturing facilities is highly valued by our customers. We seek to capture the value of our R&D and TS&D services and manufacturing capabilities through our pricing strategy.

Seasonality

Reporting periods impacted by the winter season and unfavorable weather conditions that typically affect the construction and building materials end markets may result in seasonally lower performance, particularly in the CASE applications of our Latex Binders segment.

Polymer Solutions Segment

Overview

Our Polymer Solutions segment consists of a variety of polymers, the majority of which are for building and construction applications. The segment includes our mass acrylonitrile butadiene styrene (“ABS”), styrene-acrylonitrile (“SAN”), and polystyrene businesses, as well as our polycarbonate technology. The Polymer Solutions segment also includes the results of converting post-consumer and post-industrial PMMA, PC, ABS, polystyrene, and other thermoplastic waste for use in a wide range of high-end applications. In 2025, approximately 62% of net sales from our Polymer Solutions segment were generated in Europe, 15% were generated in North America, and the majority of the remaining net sales were generated in Asia.

Products and End Uses

Copolymers. Our copolymers products consist of ABS and SAN. In 2025, copolymers represented approximately 44% of total segment net sales.

We produce mass ABS (“mABS”), a variation of ABS that has lower conversion and capital costs compared to the more common emulsion ABS (“eABS”) process, marketed under our MAGNUM brand. mABS has similar properties to eABS but has greater colorability, thermal stability and lower gloss. mABS products can be manufactured to stricter specifications because they are produced in a continuous process as opposed to the batch process used in eABS. mABS also has environmental benefits such as waste reduction and higher yields. In addition to our own mABS production capacity, we have licensed our proprietary mABS technology to other producers.

Primary end uses for our ABS products include automotive and construction sheet applications. We maintain a significant share of ABS sales into these markets, which we believe is due to the differentiating attributes of our mABS products, our reputation as a knowledgeable and reliable supplier, our broad product mix, and our customer collaboration, including design capabilities.

SAN is composed of styrene and acrylonitrile, which together provide clarity, stiffness, an enhanced ability to be processed, mechanical strength, barrier properties, chemical resistance and heat resistance. Our SAN products are manufactured in Terneuzen, The Netherlands and are used mainly in appliances, consumer goods and construction sheets, due to their low cost, clarity and chemical resistance properties.

Polycarbonate (PC). In December 2024, following the decommissioning of the Stade, Germany polycarbonate plant, the Company no longer manufactures virgin PC and sources its PC needs from external suppliers. However, the

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Company continues to leverage its know-how and IP regarding our proprietary PC technology in the form of licensing agreements, as well as innovation in recycled PC technology.

PC has high levels of clarity, impact resistance and temperature resistance. PC can be used in its neat form (prior to any compounding or blending) for markets such as construction sheets and profiles, medical and lighting. Additionally, PC can be compounded or blended with other polymers, such as ABS, which imparts specific performance attributes tailored to the product’s end use.

Our products for glazing and construction sheets are marketed under the CALIBRE brand name and offer customers a combination of clarity, heat resistance and impact performance.

Polystyrene. We produce polystyrene with a focus on sales to injection molding and thermoforming customers. Our product offerings include a variety of general purpose polystyrenes (“GPPS”) and high impact polystyrene (“HIPS”). HIPS is polystyrene that has been modified with polybutadiene rubber to increase its impact resistant properties. These products provide customers with performance and aesthetics at a relatively low cost across applications, including appliances, packaging, including food packaging and food service disposables, consumer electronics and building and construction materials. We view recycled polystyrene products as important not only for the benefit of the environment but also as a way to better serve our customers by addressing their need for sustainable solutions.

The STYRON™ brand is widely recognized in the global marketplace and we believe our R&D capabilities provide valuable, differentiated solutions for our customers, making us well-positioned to address the sustainability, weight reduction, and safety needs.

In 2025, we closed our PS production operations in Schkopau, Germany with consolidation of remaining PS operations in Tessenderlo, Belgium.

Competition and Customers

Our principal competitors in our Polymer Solutions segment are Covestro AG, Saudi Basic Industries Corporation, INEOS Styrolution, Versalis S.p.A., Shanghai Kumho Sunny Plastics Co., Ltd., LG Chem, Lotte Chemical Corporation, Total S.p.A., Sinopec Corp., Formosa Chemicals & Fibre Corp., and Chi Mei Corporation.

In our Polymer Solutions segment, we compete primarily based on our ability to offer innovative, differentiated, sustainable and reliable products, the quality of our customer service, operational reliability and the length and depth of our customer relationships.

We believe potential growth in the Polymer Solutions segment will be impacted by a number of factors, including consumer preference for lighter-weight and impact-resistant products. Additionally, we believe growth prospects are bolstered by sustainability trends such as electric vehicles and potential government mandates, such as the substitution of lighter-weight plastics for metal in automobiles. Our innovation has contributed to long-standing relationships with customers who are recognized leaders in their respective end markets.

Our customer-centric model focuses on understanding customers’ needs and developing tailored relationships that add value beyond the value of the actual product performance. For durable applications, we focus our efforts on product design engineering initiatives for developing and specifying plastics in the next generation of construction applications and appliances. In non-durable applications, we focus on innovative products that provide clear cost advantages to our customers, serving customers with our cost-advantaged technology and operating excellence. We are also able to offer various sustainable product innovations in our non-durable applications, especially packaging.

Seasonality

Reporting periods impacted by the winter season and unfavorable weather conditions that typically affect the construction and building materials end markets may result in seasonally lower performance in our Polymer Solutions segment. Additionally, sales volumes may fluctuate from quarter-to-quarter as customers may adjust their purchasing patterns based on their expectations of polystyrene price changes caused by underlying raw material cost changes.

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Americas Styrenics Segment

Overview

This segment consists solely of the operations of our 50%-owned joint venture with Chevron Phillips Chemical Company, Americas Styrenics LLC (“Americas Styrenics”), which continues to be a leading producer in North America of both styrene and polystyrene. In 2025, Americas Styrenics supplied 18% of the styrene monomer capacity in North America. We received a total of $12.5 million in cash dividends from Americas Styrenics during 2025.

Products and End Uses

Styrene monomer is a basic building block of plastics and a key input to many of the Company’s products. Styrene monomer is a key raw material for the production of polystyrene, and in 2025 approximately 59% of the styrene monomer produced by Americas Styrenics was consumed in its own production of polystyrene. The remainder of Americas Styrenics’ product is sold as a key raw material to other manufacturers of polystyrene, expandable polystyrene, SB latex, ABS resins, unsaturated polyethylene resins, and styrene-butadiene rubber.

Americas Styrenics also produces GPPS, high heat, high impact resin, and STYRON A-TECH™ polystyrene products. Major applications for these polystyrene products include appliances, food packaging, food service disposables, consumer electronics, and building and construction materials.

Competition and Customers

Americas Styrenics’ principal competitors are INEOS Styrolution, Total S.p.A., and LyondellBasell. In our Americas Styrenics segment, we compete primarily based on our ability to offer reliable products as well as the quality of our customer service and the length and depth of our relationships.

As a leading styrenics producer in North America, this segment is well-positioned to benefit from consolidation dynamics in the styrene and polystyrene industries within the region. Effective operating rates can, from time to time, be impacted by planned and unplanned outages, leading to periods of elevated margins.

Seasonality

Reporting periods impacted by the winter season and unfavorable weather conditions that typically affect the construction and building materials end markets may result in seasonally lower performance in our Americas Styrenics segment.

Our Relationship with Dow

Following the Dow Separation, we entered into certain long-term agreements with Dow to provide services. We maintain a significant relationship with Dow for certain site services, utilities and certain raw materials purchases. The failure of Dow to perform their obligations, or the termination of these agreements, could adversely affect our operations. See Item 1A—Risk Factors for more information.

We are party to various site services agreements (“SAR SSAs”) for Dow to provide site services to the Company at Dow-owned sites. Conversely, we entered into similar agreements with Dow, where, at Company-owned sites, we provide such services to Dow. These agreements cover general services that are provided at certain facilities co-located with Dow, including utilities, site administration, environmental health and safety, site maintenance and supply chain. These agreements generally have 25-year terms and include options to renew. These agreements may be terminated at any time by agreement of the parties, or, by either party, for cause or under certain circumstances for a material breach. In addition, we may terminate with 12-months’ prior notice to Dow any services identified in any SAR SSA as “terminable.” Highly integrated services, such as electricity and steam, generally cannot be terminated prior to the termination date unless we experience a permanent production unit shut down for which we provide Dow with 15-months’ prior notice, or upon payment of a shutdown fee. Upon expiration or termination, we would be obligated to pay a monthly fee to Dow for a period of 45 to 60 months following the expiration or termination of such SAR SSA. The agreements under which Dow receives services from us may be terminated under the same circumstances and conditions.

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Additionally, we are party to several agreements with Dow for the provision of certain raw materials, including butadiene, and other products, services and other operational arrangements. We are also party to a Capacity Reservation Contract which is an evergreen contract that provides guaranteed access to a certain portion of MMA capacity at a Dow-owned manufacturing facility in North America, which was assumed in connection with our acquisition of the PMMA business from Arkema S.A. (the “PMMA Acquisition”). See Sources and Availability of Raw Materials for more information. Under the Amended and Restated MOD5 Computerized Process Control Software, Licenses and Services Agreement, with Rofan Services (“AR MOD5 Agreement”), Dow provided worldwide process control technology, including hardware, software licenses and support services, and related enterprise resource planning services. We have converted all plant locations from the MOD5 process control technology and do not expect to incur any significant costs going forward.

The Second Amended and Restated Master Outsourcing Services Agreement (“SAR MOSA”) provides for ongoing worldwide services, substantially all of which were no longer provided by Dow. The Company continues to incur certain costs related to the SAR MOSA in 2025, which are expected to decrease in future years based on anticipated site shutdowns and demolition.

For the years ended December 31, 2025, 2024, and 2023, we incurred a total of $37.5 million, $54.5 million, and $140.5 million, respectively, in expenses under the SAR MOSA, AR MOD5 Agreement, and SAR SSAs (including utilities) including $37.5 million, $53.5 million, and $138.5 million, respectively, for both the variable and fixed cost components of the site services agreements and $1.0 million and $2.0 million, for the years ended December 31, 2024 and 2023, respectively, covering all other agreements.

For the years ended December 31, 2025, 2024, and 2023, purchases and other charges from Dow (excluding the SAR MOSA, AR MOD5 Agreement, and SAR SSAs) were approximately $185.3 million, $202.7 million, and $570.5 million, respectively. These purchases and other charges primarily relate to the purchase of raw materials for manufacturing our products. Additionally, for the years ended December 31, 2025, 2024, and 2023, sales to Dow were approximately $11.2 million, $65.4 million, and $95.1 million, respectively principally related to manufacturing of Dow’s products.

Sources and Availability of Raw Materials

The prices of our key raw materials are volatile and can fluctuate significantly over time. While the predominant reason for this volatility is the impact of market imbalances in supply and demand from time to time, energy prices, transportation costs and supplier force majeures have impacted and may continue to impact the volatility of some of our raw materials. The table below shows our key raw materials by reportable segment.

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Latex

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Engineered

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Polymer

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Americas

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Binders

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Materials

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Solutions

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Styrenics

Acetone

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X

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Benzene

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X

Bisphenol A

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X

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X

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Butadiene

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X

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X

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X

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Ethylene

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X

Methyl Methacrylate (MMA)

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X

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X

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Polycarbonate

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X

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X

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Styrenic resins

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X

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X

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Styrene

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X

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X

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X

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X

We have supply contracts in place to help maintain our supply of raw materials at competitive market prices and seek to implement the most efficient and reliable raw material strategy for each of our segments, including utilizing multiple sources where feasible and maintaining a balance between contracted and spot purchases of raw materials. We also produce raw materials for use by our businesses, and we purchase PCR materials for use in products such as our PC compounds. PMMA products use MMA as the key raw material, which is sourced through supply agreements. During 2025, Dow has supplied us with an aggregate 59% of the MMA used in our PMMA production, both in the United States

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through various supply agreements. In 2025, we obtained approximately 9% of our raw materials from Dow (based on aggregate purchase price).

Following our decision to cease production of styrene, PC, and MMA, these materials are purchased through strategic contracts and/or spot market purchases.

Technology

Our “One Trinseo R&D” operating model refers to our customer-focused R&D and TS&D activities, which are streamlined across our Engineered Materials, Polymer Solutions and Latex Binders business segments. As part of our customer-centric approach, our R&D and TS&D teams interface with our sales and marketing teams, and directly with customers, to determine their product requirements. These teams then consider material scientific factors, as well as industry and market segment trends in order to select, execute and commercialize new sustainable material solutions that are value-enhancing for both our customers and the Company.

Our global network of R&D Centers of Excellence (CoEs) and Technical Centers support our technological and R&D/TS&D capabilities, where our cross-functional teams work and engage with customers on technology and innovation development. We have three R&D CoE locations bringing innovation excellence across the globe in Rheinmünster, Germany, Terneuzen, The Netherlands and Exton Pennsylvania. In addition, our R&D/TS&D efforts are supported by certain “mini-plants” used to make samples of experimental products for testing, which we believe is a critical step in our new product development process. We also operate a plastics research center, which integrates two existing technical support centers and research lab operations in a single location at our Terneuzen R&D CoE location. Further, we operate pilot plants to facilitate new production technology. Finally, our network of global R&D CoEs in Europe and the United States, are responsible for knowledge sharing, synergies and best-practice standardization and talent development across our business segments.

R&D and TS&D costs are included in expenses as incurred. Our R&D and TS&D costs were $63.6 million, $63.5 million, and $57.6 million for the years ended December 31, 2025, 2024, and 2023, respectively.

Sales and Marketing

We have a customer-centric business model that has helped us to develop strong relationships with many customers. Our sales and marketing professionals are primarily located at our facilities or at virtual offices within their respective geographies. We have approximately 180 professionals working in sales and marketing around the world, along with approximately 90 customer service professionals, and we sell our products to customers in approximately 80 countries. We primarily market our products through our direct sales force. We also leverage various channel management partners, distributors, and agents in the sale of our products. Typically, our direct sales are made by our employees in the regions closest to the given customer.

Intellectual Property

We evaluate on a case-by-case basis how best to utilize patents, trademarks, copyrights, trade secrets and other intellectual property to protect our products and our critical investments in research and development, manufacturing and marketing. We focus on securing and maintaining patents for certain inventions, while maintaining other inventions as trade secrets, derived from our customer-centric business model, to maximize the value of our product portfolio and manufacturing capabilities. Our policy is to seek appropriate protection for significant product and process developments in the major markets where the relevant products are manufactured or sold. Patents may cover products, processes, intermediate products and product uses. Patents extend for varying periods in accordance with the date of patent application filing and the legal life of patents in the various countries. The protection afforded, which may also vary from country to country, depends upon the type of subject matter covered by the patent and the scope of the claims of the patent. The intellectual property that we have created or acquired since our formation covers areas such as material formulations, material process technologies and various end-use industrial applications.

In most industrial countries, patent protection may be available for new substances and formulations, as well as for unique applications and production processes. However, given the geographical scope of our business and our continued growth strategy, there are regions of the world in which we do business or may do business in the future where

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intellectual property protection may be limited and difficult to enforce. We maintain strict information security policies and procedures wherever we do business. These information security policies and procedures include data encryption, controls over the disclosure and safekeeping of confidential information, as well as employee awareness training. Moreover, we monitor our competitors’ products and, if circumstances were to dictate that we do so, we would vigorously challenge the actions of others that conflict with our patents, trademarks and other intellectual property rights.

The technologies we utilize in some of our businesses have been in use for many years (e.g., SB latex, polystyrene, PMMA and ABS) and a number of our patents relating to such technologies have expired or will expire in the future. As patents expire, or are allowed to lapse, the products and processes described and claimed in those patents become generally available for use by the public. We believe that the expiration of any single patent or family of patents that is scheduled to expire would not materially adversely affect our business or financial results. We believe that our trade secrets relating to manufacturing and other processes used in connection with products to which expiring patents relate will continue to provide us with a competitive advantage after the expiration of these patents.

We use trademarks as a means of differentiating our products. We protect our trademarks against infringement where we deem appropriate. We have successfully registered the TRINSEO™ trademark in 130 countries, and also own the Plexiglas®, Altuglas®, Solarkote® and Oroglas® marks as well as other trademarks acquired from Arkema S.A.

Dow has either transferred to us or granted perpetual, royalty-free licenses to us to use Dow’s intellectual property that was used by Dow to operate the acquired business (the “Dow Acquired Business”) prior to the Dow Separation. This intellectual property includes certain processes, compositions and apparatus used in the manufacture of certain of our legacy products. In addition to our license rights to use Dow’s intellectual property related to the Dow Acquired Business, we have obtained licenses to use Dow’s intellectual property to the extent necessary to perform our obligations under the contracts transferred to us in the Dow Separation and to use such intellectual property (other than patents) for products outside of the Dow Acquired Business as it was conducted by Dow prior to the Dow Separation, subject to certain limitations. While we believe our license rights with respect to Dow’s intellectual property are sufficient to allow us to operate our current business, growth opportunities, involving new products may fall outside of our license rights with Dow. Therefore, our ability to develop new products may be impacted by intellectual property rights that have not been licensed to us by Dow. We have the right, with Dow’s cooperation, to directly enforce the patents that are exclusively licensed to us by Dow where infringement is primarily within the scope of our business; but nothing obligates Dow to enforce against third parties the intellectual property rights of Dow that are licensed to us on a non-exclusive basis or where the infringement is primarily outside the scope of our business.

Environmental, Health, Safety and Product Stewardship

Obtaining, producing and distributing many of our products involve the use, storage, transportation and disposal of toxic and hazardous materials. We are subject to extensive, evolving and increasingly stringent environmental and safety laws and regulations, which address, among other things:

●emissions to the air;

●discharges to soils and surface and subsurface waters;

●other releases into the environment;

●prevention, remediation or abatement of releases of hazardous materials into the indoor or outdoor environment;

●generation, handling, storage, transportation, treatment and disposal of waste materials;

●climate change impacts;

●process and maintenance of safe conditions in the workplace;

●registration and evaluation of chemicals;

●production, handling, labeling or use of chemicals used or produced by us;

●stewardship of products after manufacture; and

●circular solutions, for polystyrene, PMMA, PC, ABS and other products.

We monitor compliance with applicable local, national, and international environmental, health and safety requirements and maintain policies and procedures to monitor and control environmental, health and safety risks, which

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may in some circumstances exceed the requirements imposed by applicable law. We have an environmental, health and safety organization with a staff of professionals who are responsible for environmental, health, personal safety, process safety, and product regulatory compliance and stewardship, in addition to comprehensive standards and tools. We supplement our programs with our participation in trade associations which monitor developments in legislation impacting our businesses. Additionally, our Supplier Code of Conduct includes our expectations for our suppliers to comply with applicable laws and regulations and encourages them to adhere to the highest principles of environmental responsibility.

We follow the American Chemistry Council Responsible Care® Guiding Principles for our global facilities and products and have received third party certification of our Responsible Care® Management System. Many of our facilities have been certified to ISO 14001 and other ISO management systems. We have a mature corporate environmental, health and safety audit program for our facilities. We conduct regular emergency preparedness and crisis planning and drills, at both the facility and corporate level. We expect that stringent environmental regulations will continue to be imposed on us and our industry in general.

Sustainability and Climate Change

We recognize that climate change has had and will continue to have significant impacts on our environment, particularly as it relates to extreme weather conditions and rising sea levels, and which has prompted regulations limiting, among other things, the emission of greenhouse gases. In the countries in which we operate, particularly in the EU, we are required to comply with increasingly extensive regulations to address climate change impacts and resource conservation requirements. We also monitor legislative actions and their potential impacts on the end markets we serve.

We track and publicly report our greenhouse gas emissions, water usage, waste, and energy consumptions and our facilities continue to target reductions and improvements in these areas. Our annual Sustainability and Corporate Social Responsibility Report (the “Sustainability Report”), which is available on our website, provides our most recent sustainability highlights for our products, performance and operations. The report highlights sustainability goals and other initiatives to improve our sustainability performance.

Sustainability is a key focus area of our long-term strategy. As part of this strategy, we have successfully opened a PMMA depolymerization pilot facility in Rho, Italy, which uses a continuous process to produce high-purity regenerated MMA from pre- and post-consumer acrylic solutions. This technology returns material to its monomer form and allows additives and contaminants to be removed, which previously could not be done through mechanical recycling. We also operate a polycarbonate dissolution pilot facility and an ABS dissolution technology recycling pilot plant in our Terneuzen, the Netherlands site. These sites, along with our Heathland B.V. recycling operations, represent important steps in realizing our sustainability goals.

We continue to publish an annual Sustainability & Corporate Responsibility Report with reference to the Global Reporting Initiative (“GRI”) framework, the Sustainability Accounting Standards Board (“SASB”) framework and strive to set a high standard for safety and Employee Health & Safety (“EH&S”) goals. We expect the costs of administering our sustainability program and complying with evolving disclosure regulations to increase as we continue to focus and improve our sustainability initiatives and reporting.

Environmental Remediation

Environmental laws and regulations require mitigation or remediation of the effects of the disposal or release of chemical substances. Under some of these regulations, as the current owner or operator of a property, we could be held liable for the costs of removal or remediation of hazardous substances on or under the property, without regard to whether we knew of or caused the contamination, and regardless of whether the practices that resulted in the contamination were permitted at the time they occurred. Many of our production sites have an extended history of industrial use, and it is impossible to predict precisely what effect these laws and regulations will have on us in the future. In March 2023, we reported an accidental release of acrylic latex emulsion which occurred at our Bristol, Pennsylvania site, which a portion of this material ultimately flowed into a local waterway, and certain environmental claims related to this release, some of which are still ongoing. In the past, soil and groundwater contamination occurred at some of the sites and might occur or be discovered at other sites. Subject to certain limitations, Dow is obligated to indemnify and hold us harmless with respect to releases of hazardous material that existed at our sites prior to the Dow Separation, however, the period for new claims at these sites has expired. Any active remedial projects on our properties

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which were part of the Dow Separation are being performed by Dow pursuant to its indemnification obligations. We cannot be certain that Dow will continue to fully honor their existing indemnity obligations or that the indemnity will be sufficient to satisfy all claims that we may incur. Sites acquired after the Dow Separation are subject to different limitations or may not be covered by an indemnity. We conduct comprehensive environmental due diligence for potential acquisitions to mitigate the risk of assuming obligations to conduct material levels of environmental remediation. For a more detailed description of the risks related to environmental remediation, see Item 1A—Risk Factors.

Board Oversight

The Environmental, Health, Safety, Sustainability and Public Policy Committee (the “EHSS&PP Committee”) of the Company’s Board of Directors assists the Board with oversight of Company programs, policies and initiatives that support the environment, health and safety, sustainability, corporate social responsibility and climate change. The EHSS&PP Committee is responsible for supporting alignment between the Company and the Board on the Company’s sustainability, social, and public policy goals; guiding the Company and overseeing management of risks arising from our sustainability programs, policies, partnerships, activities and goals; reviewing external public policy/governmental affairs issues and trends and recommending Company response to these issues. The EHSS&PP Committee also reviews the Company’s annual Sustainability Report for Board approval and publication on the Company’s website.

Government Regulation

In addition to environmental, health, and safety laws and regulations, our operations subject us to numerous federal, state, and local laws and regulations in the countries in which we operate. International trade laws and trade agreements, tariffs, and export and customs controls can limit the countries in which we can do business or add significant cost to the import or export of our products or raw materials. Changes or violations of these regulations could impact the costs of our goods or cause delay in shipments. Our products are also used in a variety of end-uses that have specific regulatory or consumer safety requirements such as those relating to food packaging or medical devices. Changes in these requirements could result in increased compliance costs, product recalls, or fines, which could prevent or inhibit the development and sale of our products. These and other laws and regulations impact the manner in which the Company conducts its business, and changes in legislation or government regulations can affect the Company’s global operations, both favorably and unfavorably. For a more detailed description of the various laws and regulations that affect the Company’s business, see Item 1A—Risk Factors.

Security

We recognize the importance of security and safety to our employees and the community. Physical security measures have been combined with process safety measures (including the use of technology) and emergency response preparedness into integrated security plans. We have conducted information security assessments at our operating facilities worldwide and, on an ongoing basis, we work to implement appropriate measures to protect these facilities from physical and cyber-attacks. Effort and resources in assessing security requirements at our manufacturing facilities will continue, as required by U.S. Department of Homeland Security and other requirements.

The Company has implemented information security solutions, resources, policies, programs, and monitoring alerts to respond to potential information security events and to maintain compliance with the increasing amount of data privacy laws and regulation. Our Board of Directors provides oversight of security risks, measures and incidents, with input from members of management and our information security team. For a more information on the Company’s cyber risk management program, see Item 1C—Cybersecurity.

Human Capital Resources and Objectives

As of December 31, 2025, we had approximately 2,800 employees worldwide, with the majority (approximately 55%) located in the EMEA region (Europe, Middle East and Africa), approximately 30% in the Americas, and the remainder in Asia Pacific. Approximately 97% of our workforce is full-time.

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Nearly 70% of our personnel are located at the various manufacturing sites, research and development, and technology centers. The remaining employees are located at operating centers, virtual locations or geographically dispersed marketing and sales locations. Our facilities in Midland, Michigan, Bristol, Pennsylvania, as well as Louisville and Florence, Kentucky have union representation, while employees at certain of our other locations are represented by work councils. We believe we maintain good relations with our personnel and various labor organizations. There have been no labor strikes or work stoppages in these locations in recent history.

People Strategy

We strive to retain a talented and inclusive workforce and understand that our success requires ongoing investment in our employees. Our approach to attracting and retaining talent is our commitment to our core values of Responsible Care®, Innovation, Respect & Integrity, Accountability & Value Creation, and Commitment to Customers. As applied to our employees, these values prioritize health and safety, accountability and rewards for achievement, and treatment of all persons in our organization with respect, honesty, and dignity.

Our core values are reflected in the goals of our “People Strategy,” which is designed to support employees through Organizational Development, Talent Management, Equity & Inclusion and Recognition & Rewards. Organizational Development focuses on the design of organization models to achieve our business strategies, assess employee engagement, shape our culture and facilitate open communication. Talent Management measures our ability to attract and select the right talent for the right roles, onboard new employees to improve integration, build critical capabilities, and develop leaders of the future, with a culture of collaboration among high-performing and diverse teams. Equity & Inclusion challenges us to create and maintain an environment that welcomes a broad range of diverse talent and facilitates and fosters a culture of inclusion. Recognition & Rewards means our efforts to manage, measure, and pay for performance; differentiate and recognize job growth with base salary increases, promotions, new assignments, annual performance awards and recognition of outstanding contributions from employees.

Employee Health & Safety

Focus on the safety of our employees is a critical aspect of our operations. We strive towards achieving zero injuries, spills, or process safety incidents in our facilities every year. Our EH&S management system promotes a culture of rigorous investigation, corrective action, and continuous improvement applied over many years and has delivered a world-class set of internal safety policies, processes, and procedures. This system is designed to meet our objectives to continually reduce safety and environmental incidents and risks, maintain full regulatory compliance, satisfy stakeholder expectations, optimize resources, and continuously improve. We have developed a set of leading indicators and training programs to help highlight and drive improvement in Operational Safety, Process Safety, and Product Safety across the company, with effectiveness assessed on a regular basis and modified as needed to drive improvement.

Equity & Inclusion

We are committed to maintaining an inclusive workforce that offers a broad range of perspectives, backgrounds and experience, and creating an environment in which all Trinseo employees have an equal opportunity to reach their potential and contribute fully to the success of the Company. Trinseo provides an equal employment opportunity, with a policy to recruit, hire, develop, and promote qualified applicants or employees without regard to race, color, religion, sex, pregnancy, gender identity, sexual orientation, veteran status, national origin, age, disability, or genetic information. We believe our commitment to equity and inclusion, and attracting the best candidates, is reflected in our Board and executive leadership team. Fifty-five percent of our Board and thirty-three percent of our executive leadership team are women, and three of our Board members self-identify as a member of an underrepresented minority group. Our executive leadership team also represents broad citizenship and geographic diversity.

Talent Management and Employee Development

We provide opportunities for career development through a combination of training, coaching, and on-the-job experiences. We believe this approach to development provides our employees with the right balance of learning options. Further, we believe that early investment in our employees ensures that our future leaders have the skills they will need to be successful within a complex and ever-changing business environment. Our annual succession planning process identifies successors for some of our most critical roles and recommends tangible developmental actions for incorporation into their long-term personal development plans. We also utilize a goal setting scorecard that enables

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employees to document and align their goals within a leadership team and across functions, which goals are set against annual Company priorities. Employees are evaluated on their performance versus individual goals and on the Company’s performance versus corporate goals (which includes financial and safety metrics). Part of the annual performance review process includes personal assessment goals which are tracked and reviewed throughout the year.

Compensation Policies

Our process for determination of remuneration consists of two main components: base pay and an annual variable program, and we are committed to ensuring equitable compensation among our employees. As stated above, equal opportunity and diversity are important at Trinseo. We conduct internal reviews to assess fair treatment to determine if our pay practices are being implemented appropriately in all jurisdictions where we operate. In the United States, we also conduct internal reviews with new hires as well as an annual exam to determine the impact of ethnicity on pay decisions.

Available Information

Our annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, are available free of charge through the Investor Relations section of our website, www.trinseo.com, as soon as reasonably practicable after the reports are electronically filed or furnished with the U.S. Securities and Exchange Commission (“SEC”). Copies of our board committee charters, code of conduct, corporate governance guidelines and other corporate governance information are also available on our website. See Part III–Item 10–Code of Ethics. We provide this website and the information contained in or connected to it for informational purposes only. This information is not included in, or incorporated by reference to, this Annual Report.