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based FDM (Fused Deposition Modeling) technology. It offers 0.1-mil resolution, finer than that of thermoplastics. The LSR material can be used to produce prototype parts in less than a day and customized parts with high strength. Moreover, Wolf sees potential for its use in mass production through additive manu- facturing of parts with "endless design freedom." Dow Corning also developed a low-temperature-cure (LTC) LSR for coinjection with lower-melting-point thermoplastics such as PE and PP. The new LSR cures at 100-120 C (212-248 F), which enables incorporation of heat-sensitive active ingredients for healthcare applications, as well as encapsulation of sensitive components for electronics. Also new, is an ultra-high-durometer (90 Shore D) LSR, Silastic LC 8800-90, with higher-temperature stability, for hard-soft LSR-on-LSR overmolding. The ultra-hard LSR is poised to replace thermoplastics in such hard-soft combinations and reportedly offers unique combinations of rigidity and elasticity. Using LSR for both hard and soft components could improve dimensional integrity, interfacial bond strength, and long-term stability in hot/ humid conditions. Meanwhile, automotive electri- fication has led to the development of a self-lubricating LSR from Dow Corning with excel- lent processing and low compression set. High-temperature stabilizer technology is said to provide better compression set and other mechanical properties for LSR. For baby products, Dow Corning developed a new low-vola- tility LSR that needs no post-cure. And for challenging lighting applications, the company now offers flexible optical LSRs. Huiping Zhang, a chemist with Momentive, Waterford, N.Y. (momentive.com), discussed new LSR developments for medical and consumer markets. Notable among them is a self-bonding Silopren LSR that forms chemical bonds with substrates such as PC, PBT, copolyesters, and glass, but without no sticking to common mold materials. It has low viscosity and enables low- temperature cure. Zhang also noted that Momentive's unique UV-curable Silopren LSR line, now five years old, offers another means of co-molding LSR with low-temperature thermoplastics such as PP. It reportedly cures even thick sections quickly at room temperature. NEW DEVELOPMENTS IN TPES Liang Xu, technology manager for product development at PolyOne, Avon Lake, Ohio.(polyone.com), discussed a new portfolio of low- VOC and low-fogging TPEs (35 to 65 Shore A) for automotive inte- riors. Not only do these TPEs show significantly lower emissions than existing TPEs, but they also reduce manufacturing steps, as they do not require post-curing to drive off VOCs and odors. These OnFlex LO injection grades are well suited for overmolding onto PP substrates, Xu said. PolyOne can provide grades with gravimetric fogging of <0.5 mg. Xu cited the case of a Tier 2 manu- facturer of HVAC flaps that wanted to eliminate post-treatment of parts to achieve a required odor level of <3 VDA 270 with the lowest VOC/ fog level (VDA 278) at the same compression set as the previous LSR. OnFlex LO reportedly achieved the required odor level with added benefits of fewer processing steps and lower energy costs. Meanwhile, novel high-heat thermoplastic copolyesters (TPCs) capable of contin- uous-use temperatures 40-50° C (72-90° F) higher than similar TPEs were discussed by Paul Moruzi, business manager for DSM Engineering Plastics, Troy, Mich. (dsm.com). He showed that DSM's new Arnitel C and Arnitel HT PBT-based TPCs are succeeding in high-temperature automotive TPE applications. Arnitel C is getting play in Class D high-temperature wire and cable. These non-haloge- nated flame-retardant systems are engineered for low outgassing. Moruzi also sees these new TPCs as suited to vacuum-brake tubing, replacing thermoset rubber. In the 2015 Chevy Silverado, Arnitel HT cut weight by half vs. thermoset rubber and reduced cost. Blow molded turbo hot-charge ducts made of Arnitel HT TPC also show major weight reduction vs. rubber hoses. The material has also been validated in cold-charge ducts. Key growth sectors for TPEs are medical/ pharma, packaging, and automotive—including autonomous/semi- autonomous vehicles. OnFlex LO TPEs for auto interiors show significant VOC/fog reduction over existing TPEs and also do not require post-heating. For challenging lighting applications, Dow Corning now offers optical moldable, flexible LSRs. 18 SEPTEMBER 2017 Plastics Technology PTonline.com M AT E R I A L S Close -Up On Technolog y