Catering to Customers

Customer demand drives innovation within epoxy technology. A. Schulman is an international supplier of high-performance plastic compounds, composites and resins. The vast majority of the company’s thermoset products utilize polyester and vinyl ester resins. “We offer epoxies when specific applications demand that an epoxy be used, whether for aerospace or a hot-wet environment where an epoxy will hold up better than a polyester or vinyl,” says Tim Langschwager, product manager for A. Schulman’s sheet molding compound (SMC), thick molding compound (TMC) and Quantum Composites® product lines.

An automotive OEM approached the company several years ago to replace its vinyl ester SMC. “The objective was to create an epoxy compound that could exceed the performance of their current SMC, while offering lower VOCs and higher mechanical performance,” says Langschwager. “They had specific targets around thermal performance for glass transition temperatures, tensile strength, compressive strength, surface finish, room temperature stability, and flow and fill of the material.”

The company developed a product line that relies on several different epoxy resin systems – combined in different ratios to maximize performance – rather than a single, standard resin. The sheet molding compounds use standard BPA, bisphenol-F, multifunctional and novalac epoxies with a variety of amine, anhydride and boron triflouride hardeners, reactive diluents and accelerators. Officially launched at CAMX 2017, the LYTEXSF series of sheet molding compounds includes three different resin systems for carbon fiber, glass fiber and continuous fibers.

Langschwager says it’s all about dialing in to customers’ specific needs. “If they are concerned about storage and need longer room temperature stability, out life and pot life, then you can modify the curative and additives. If they need a tougher system, there are a lot of epoxy reactive diluents to help viscosities and add toughness,” he says. “Epoxy suppliers today are more willing to work on a full solution as opposed to saying, ‘Here’s our resin. Figure out how to use it.’”

Olin-pressure-vessel

This Type IV pressure vessel for compressed natural gas storage features an epoxy anhydride system for high glass transition values and enhanced fracture toughness. Photo Credit: Olin Corporation

Olin’s approach to product development is similar. It introduced the LITESTONE portfolio of epoxy systems, which has more than a dozen products with tailored processing and performance characteristics. LITESTONE 2130/2142, for example, is designed for the filament winding process. The low viscosity epoxy anhydride system has a minimum pot life of 12 hours, which allows for long working times – a key requirement for filament winding. “The unique aspect of the 2130/2142 system is the enhanced fracture toughness, which is achieved without any compromise to its temperature or mechanical properties,” says Guillaume. The system has been used in Type IV pressure vessels for compressed natural gas (CNG) storage.