CompositesWorld

AUG 2016

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AUGUST 2016 30 CompositesWorld FEATURE / GLASS FIBER SIZINGS A real sizings "hot spot" — figuratively and literally — is auto- motive underhood applications, where high temperatures and corrosive liquids, such as ethylene glycol (in anti-freeze), and other hot fluids "bring stringent requirements to the design of fiberglass," says PPG's Watson. "e sizing design can result in orders of magnitude improvement in performance, particu- larly for high temperature and hydrolysis." e best resins for this extreme environment are typi- cally thermoplastic. e workhorses here are nylon (polyamide), PP and thermoplastic varieties of polyester, with limited volume in the poly- etheretherketone (PEEK), polyphenylene sulfide (PPS) and polyaryletherketone (PAEK) resins. Emerging technologies also will demand customized and improved sizings for best interface functions, Bassetti adds. For example, new ways to use continuous fiber or higher aspect ratios to build additional strength into the composite — processes that require thermoplastic prepregs or organo sheets (strong, light- weight continuous fiber-reinforced thermoplastic structural components) and thermoplastic resin transfer molding (RTM) — are creating new opportunities to optimize the sizing and fiber/ matrix interface, Bassetti says. Michelman is actively working on sizing upgrades to fulfill the requirements of these advancements (see, for example, Fig. 4, p. 28). The latest in sizing technology Silanes and other sizing components, such as dispersants and emulsifiers, are provided by several divisions at chemical manu- facturer Evonik (Essen, Germany). Evonik dedicates a portion of its research to new sizing systems and ingredients. e compo- nents that most distinguish one fiber manufacturer's product from comparable fibers produced by another, sizings are highly proprie- tary (see Learn More). "Fiber sizing is one of the big secrets of fiber manufacturers," says Stephan Sprenger, the senior market develop- ment manager for composites and lightweight construction with Evonik's Business Line Interface & Performance group. So it was a notable exception when Sprenger revealed to CW that his team is working on the improvements possible when nanosilica (SiO 2 ) particles are added to sizing in quantities of <1 wt/%. "When cyclic forces are applied to a fiber-reinforced composite or a sudden impact occurs, microcracks can form within the resin matrix, and over time, the crack propagates through the matrix and along the fiber," Sprenger says. Testing concluded Read this article online | short.compositesworld.com/FiberSizin Read more online about "The making of glass fiber" | short.compositesworld.com/GlassFiber Read CW's online sidebar to this feature article, title "Sizing for carbon fibers" | short.compositesworld.com/CFSizing Read more about sizing components in Glass Fibre Sizing: A review of size formulation patents, Prof. James L. Thomason's analysis of glass fiber sizings based on a review of patents on the technology. University of Strathclyde (Glasgow, Scotland, UK), 2015.

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