CompositesWorld

AUG 2016

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AUGUST 2016 28 CompositesWorld FEATURE / GLASS FIBER SIZINGS says, for example, that Aliancys is working on sizings for excel- lent wettability and compatibility with newer styrene-free resins. "Often," he explains, "sizing chemistries for styrene-containing thermosets do not perform well when used with new styrene-free resin that is based on methacrylate solvents and derivatives." Second, says Bassetti, is the intended process, which includes whether the sizing is for chopped or continuous fiber and the forming method, such as compression molded sheet molding compound (SMC) or filament winding. PPG's Watson says, "An important trend in the past 5 or 10 years has been a great broadening in different kinds of glass composi- tions, in addition to traditional E-glass, to more corrosion-resistant ECR glass and to high-modulus glasses." Sizing products, there- fore, also are increasingly driven by changes in glass composition and accompanying changes in the fiber surface to make sizing compatible with corrosion-resis- tant, low-boron or boron-free glass, for example, or high-modulus glasses for wind turbine blades, he says. Aliancys, says Pellegrini, is developing sizings for specific inline wetting processes, such as pultrusion and filament winding, aimed at reducing part production time and process energy consumption. Last but not least, the chemist must consider part performance and the environment where the part will be installed — an automo- tive interior, underhood or fuel-system component, an electronic laptop component, a wind blade or one of myriad other market applications. at includes the challenge to sizing chemists of part size. Aliancys' Pellegrini says that sizings based on low-molecular- weight epoxy chemistry have been successfully used for years in wind turbine blades and other direct roving applications. Wind blades are getting longer, however, to increase wind turbine power output, emphasizing the need for durability, stiffness and fatigue resistance in fiberglass blades. Skinner notes that blade manufacturers invest an "incredible amount of money in tooling" for, say, a 75m long blade. And then "they put more than 40 tons of glass into a mold and infuse it with resin." With so much capital in fixed assets, the ability to make parts quickly is critical. "So the ability of sizing chemistry to respond to the increasing scale of applications is a key factor in sizing innovations," says Skinner. Here the fiber/resin bond is key. "So we're driving inter- facial science to drive up the perfor- mance of our products." e industry is asking for fiber performance improvements that will demand specific sizings, tailored, customized and optimized in a way appropriate to the end-use application, Bassetti explains, noting that for Michelman's line of sizing products, including its registered flagship product, Hydrosize, the fiber interface is becoming more critical as advances in resin and fiber technology reach maturity. "Today's research is targeted at specific applica- tions," Bassetti points out, offering as examples, a polypropylene supplier that might be looking for low VOCs in automotive inte- riors (see Fig. 3, p. 27), or a nylon supplier that might need greater hydrolytic resistance or better glycol resistance. Bassetti sums up the trend in a single word: Specialization. Competition + regulation Pellegrini frames the specialization trend in terms of global market pressures. Demand for glass fiber will continue to be high, but strong price competition from fiber suppliers in Asia has been a factor in challenging established glass fiber producers to focus on reducing costs by improving their efficiency and productivity. Fig. 4 Optimizing sizings for fiber- reinforced thermoplastics This automotive front-end module, for housing a car's radiator and other components, is made using LFT processing, from fiberglass with Michelman's (Cincinnati, OH, US) Hydrosize sizing customized for a polypropylene matrix. Source | Michelman Fig. 5 Experimenting with SiO 2 as an additive Tests conducted by researchers at Evonik (Essen, Germany) indicate that the performance of wind turbine blades could be significantly increased by adding nanosilica to the glass fiber sizing formula. Source | Evonik Industries

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