MATERIALS: SABIC Innovative Plastics’ Lexan XHT clear, high-temperature polycarbonate (PC) copolymers are an innovative family of advanced PC resins features new polymer chemistry with an optimal balance of high heat resistance and high flow, enabling it to offer greatly expanded design options for molding thin-wall parts such as medical devices and electrical fuses. Lexan XHT copolymers also offer excellent clarity and colorability, making them top choices for applications like consumer and industrial lighting and heat shields. They are part of SABIC Innovative Plastics’ growing Lexan copolymers portfolio built on the technology foundation laid by Lexan PC resin’s 50-year track record.
Lexan XHT copolymers address the need for PC-based materials with end-use temperatures in the range of 140 to 195C. They deliver an industry-leading relative thermal index (RTI) Underwriters Laboratories (UL) rating of 150C, surpassing polyarylate (PAR), polymethyl methacrylimide (PMMI) and other high-heat polycarbonates (HHPC). This exceptional high-temperature performance is achieved through proprietary chemistry that alters the polymer backbone by incorporating specialized monomers. Copolymers offer higher performance than compounds, blends and additives, which are not chemically integrated.
Lexan XHT copolymers surpass competitive high-heat materials in other key areas:
- Lower color shift on ultraviolet (UV) weathering vs. PAR
- Better color stability under heat aging vs. HHPC
- Improved tensile and impact strength retention after heat aging vs. HHPC
- Better resistance to cracks and haze after metallization than HHPC
- Improved flame retardancy vs. PC, PMMI and HHPC. Compliance with eco protocols and UL94 capability down to V0 at 1mm and 5VA at 3mm in clear and opaque colors
- Electrical properties suitable for high-heat film applications
Lexan XHT copolymers minimize color shift and retain clarity over a long lifespan. The high-heat color stability and clarity of Lexan XHT copolymers make them an excellent candidate for applications including aesthetic and functional enclosures for industrial and commercial lighting, consumer products such as heat resistant helmets and heat shields, electrical components such as fuses, and non-biocompatible healthcare devices that must undergo autoclaving.
These materials have already been proven in automotive applications including bezels, reflectors and lens covers where they enable direct metallization, which eliminates the costs and environmental impact from pre-coating the part with paint or lacquer. When vacuum-metalized, parts made from Lexan XHT copolymers can withstand temperatures of up to 175C without blistering, hazing, delaminating or losing their brilliant luster.
To help designers reduce size, mass and weight, and create thinner-walled flame-retardant parts such as housings for consumer electronics, Lexan XHT copolymer grades offer improved flow characteristics for injection molding. These materials deliver a 30 percent longer flow length and better mold release than competitive high-heat materials, which help decrease melt temperatures and cooling requirements and cut cycle times by as much as 25 percent. In a heat-critical thin wall battery cover application, Lexan XHT resin was able to fill a part with 0.7mm nominal wall thickness.
Further, Lexan XHT copolymers can be recycled, allowing scrap to be reused in molding to raise yield and lower net costs. For example, because these materials can be direct-metalized without lacquering, scrap can be reused in the molding process. These properties can significantly reduce system costs, enabling a competitive advantage for customers.
-Edited by Kelsey Anderson