Impact fracture mechanisms investigation of MICA-filled polyurethane/urea rim composites
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The impact fracture behavior of commercially available reaction injection molding (RIM) polyurethane/urea (PUR) systems was investigated using a novel double-notch four-point-bend charpy impact (DN-4PB-CI) test, followed by microscopy investigations. It is found that the PUU matrix is capable of large scale plastic deformation under mode-I DN-4PB-CI fracture. However, when mica filler is added, the PUU matrix begins to fail in a brittle manner. No sign of matrix plastic flow is observed. Furthermore, since mica filler is flake-like in shape, the orientation of mica, which can be strongly influenced by the processing condition as well as processing direction, appears to affect the Charpy impact fracture toughness of the mica-filled PUU system. The present work intends to give the first investigation of its kind on fracture mechanisms study of the PUU-RIM systmes under impact conditions. Approaches for making impact damage-tolerant PUU-RIM systems are discussed. © 1995 Polymer Society.
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