MATERIALS | REINFORCING FIBRES
Right: Thermo- Flow 641 is intended for use in polypropylene compounds
performance of the composite over and above E glass solutions in similar applications,” Montgom- ery says. “S-2 Glass fibres often compete with carbon fibres, as they both have very similar tensile strengths; however, the S-2 Glass fibre-based products have the same electrical and thermal insulation properties as other glass fibres.” AGY has worked with selected compounders to
compare thermoplastic compounds produced with S-2 Glass fibres with alternatives using E glass (sourced from both AGY and another supplier). Figure 1 shows the results of tests with compounds based on PEEK. The S-2 Glass compounds achieved an improvement of greater than 20% in tensile strength and modulus, and an improvement over 40% in unnotched impact strength. Montgomery says the superior properties of the S-2 Glass make it possible for compounders to reduce reinforcement levels to obtain the required mechanical properties with a lower compound density, enabling a reduction in final product weight. He also highlights the lower coloration in compounds containing S-2 Glass fibre compared with E glass.
“E glass has considerable coloration caused by the inclusion of small amounts of tramp oxides in the raw materials and an interaction of the molten E glass with the furnace materials when the glass is manufactured,” he says. Raw materials for S-2 Glass fibre are much purer and there are no interactions in the molten state that affect colour. “The use of S-2 Glass fibres in transparent applications is possible, if the resin has a refractive index close to that of S-2 Glass fibres,” Montgomery says. Johns Manville has introduced two new chopped strand grades of glass fibre for thermo-
plastic polyester and polypropylene (PP) com- pounds. It says ThermoFlow 600+ for PBT/PET provides improved flow performance for complex shapes used in electronic components. “Thermo- Flow 600+ has excellent colour matching and colour retention performance after aging as well as exceptional strand integrity and easy feeding in compounding processes,” says Karin Demez, Global Marketing and Portfolio Leader in Engi- neered Products – Global Fibres. ThermoFlow 641, meanwhile, is said to deliver
“exceptional” mechanical properties in polypropyl- ene and is designed to perform in detergent resistant applications such as washing tubs in appliances. “The improved colour performance and low yellowness enables compounders to further increase the use of polypropylene in general purpose consumer applications,” Demez says. The improved flow also yields more consistent properties, the company claims. Johns Manville attributes the property improve- ment in the ThermoFlow 641 grade to the use of novel and advanced sizing chemistry and optimisa- tion of the manufacturing process. It says better composite performance can be achieved at the same level of coupling agent, or cost can be cut by reducing coupling agent by up to 75% without a loss in performance relative to standard fibre (Figure 2). Demez also points to StarRov 853 roving, designed for reinforcement in structural engi- neered thermoplastics, such as tapes and LFT (Long-Fibre Thermoplastics), where high heat performance is required. Owens Corning Global Product Manager
Figure 2: Comparison of tensile strength of a PP compound using ThermoFlow TF641 glass against a standard grade Source: Johns Manville
42 COMPOUNDING WORLD | October 2017
Geoffrey Gendebien has been discussing compos- ite product solutions for transport applications at some recent public meetings. Most recently, at the Automotive Plastic Summit in Berlin in Germany in May, he highlighted Hydrostrand 258, which helps
www.compoundingworld.com
PHOTO: JOHNS MANVILLE
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