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Effect of compounding on the properties of short fiber reinforced injection moldable thermoplastic composites
Author(s) -
Bigg D. M.
Publication year - 1985
Publication title -
polymer composites
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.577
H-Index - 82
eISSN - 1548-0569
pISSN - 0272-8397
DOI - 10.1002/pc.750060105
Subject(s) - materials science , composite material , compounding , ultimate tensile strength , fiber , polymer , glass fiber , thermoplastic , izod impact strength test , extrusion , molding (decorative)
The mechanical properties of short‐fiber‐reinforced thermoplastic composites depend on the degree of interfacial bond strength between the fibers and polymer matrix. This interfacial bond strength can be increased by appropriate coupling agents. This study shows, for example, that an amino silane coupling agent improves the bond strength of nylon‐aluminum fiber composites, but not polycarbonate‐aluminum fiber composites. For cases where appropriate coupling agents are not available it is important to maintain as high a fiber aspect ratio as possible in a molded part. This study shows that a single screw compounder does less damage to glass or carbon fibers than a twin screw compounder under similar processing conditions when the polymer is in the form of pellets. When the polymer is supplied as a powder, satisfactory dry blends can be produced and the twin screw compounder does less damage to the fibers. In both cases, however, fibers initially 6 mm long are reduced to an average length less than 0.5 mm. The greatest degree of fiber size retention was observed when extrusion coated fiber pellets were used in the injection molding machine. The relationship between a fiber's tensile strength and the interfacial shear strength between a fiber and matrix yields a critical fiber aspect ratio below which the maximum reinforcing capability of the fibers are not being utilized. For the polymers investigated in this program, the critical aspect ratio for carbon fibers was found to be between 16 and 25 to 1. The polymers investigated include flame‐retardant grades of acrylonitrile‐butadiene‐styrene (ABS) and poly(phenylene oxide)/polystyrene blend, nylon 6/6 and poly(phenylene sulfide).