Maleic resins are a type of unsaturated resins based on Maleic anhydride as sole acid component in combination with different types of glycols (e.g. monopropylene glycol, monoethylene glycol, dipropylene glycol). In the resin manufacturing process at Aliancys, these ingredients are combined into an unsaturated polyester chain through a poly-condensation reaction, and then diluted with a reactive monomer (in most cases styrene) and other ingredients to make a finished resin.

Our customers combine the resin with reinforcements (glass, carbon), fillers and additives into SMC and BMC compounds. When moulding these compounds at elevated temperatures (140-150 °C) a chemical reaction is initiated between resin backbone and the styrene, transforming the liquid into a hard and durable material.

In Pultrusion processes similar mixtures are used to manufacture profiles and parts with high dimensional accuracy and enhanced surface appearance. Resin formulations can be both with and without fillers.

The Maleic resins offered by Aliancys can be easily used in combination with additives like low shrink-additives (LS), low profile-additives (LP) or Class A – additives, providing an excellent functionality in the final application (including low shrinkage effect, dimensional accuracy, surface smoothness and Class A, good pigmentability). 

Through tight process controls in our resin production a high batch-to-batch consistency is guaranteed, ensuring identical thickening of the resins when processed into SMC compounds. This translates in a smoothly running SMC molding operation with high level of automatization for the manufacturing of high quality molded parts.

Maleic resins find their way in many applications in Transportation (exterior panels, structural components, and headlamp reflectors), and in Building & Infrastructure (electrical circuit breakers, enclosures, pultruded profiles). Maleic resins are very reactive, have great heat resistance (Tg around 185°C), are the resins of choice for Class A surfaces in SMC and BMC. Class A SMC components based on Maleic resin can resist the temperatures of cataphoresis, and therefore can be in-line coated in automobile manufacturing.



Aliancys is supplying many resins based on pure Maleic chemistry under its Palapreg® brand. These resins have set the industry standard in SMC and BMC already for many years. In order to find the best product for your application, please check out the Product Selector on this web site. You can contact an Aliancys Technical Service representative for helping you in this process (



For an overview of our key products, please consult the Product Selector on this web site, or download the Aliancys Product Selector Guide.

Please read Blogs on SMC Design, Carbon composites, news on SMC BMC Design Award, and case study Mercedes Roadster (describing close collaboration Daimler, Menzolit and Aliancys).

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    AOC Aliancys

    AOC Aliancys

    AOC Aliancys is the leading global supplier of polyester and vinyl ester resins, gelcoats and specialty materials used for the composites industry. With strong capabilities around the world in manufacturing and science, we deliver unrivaled quality, service and reliability for today, and are creating innovative solutions for tomorrow. Together with our customers, we are shaping the future of composites with new technology and applications. Visit our websites below to learn more about how AOC Aliancys can help your business be more successful.