Microstructural construction of polymers with improved mechanical properties

Abstract

Mechanical properties of materials are based on structure or morphology and on the micromechanical processes of deformation and fracture, i.e. on the “micromechanics”. Developments mainly in electron microscopy and scanning force microscopy opened up a wide range of experiments previously impossible, including the in situ study of micromechanical processes. Direct microscopic techniques on the basis of scanning, transmission, and high-voltage electron microscopy are used to study micromechanical properties of different polymer blends of amorphous and semicrystalline polymers. Of particular interest are polymer blends with improved toughness. Blends with styrene–acrylonitrile as matrix polymer and different types of modifier particles, with their diameters ranging between about 100 nm and 1 μm, have been investigated. Examples of blends with a semicrystalline matrix are polypropylene (PP) blends with different amounts of various rubber and modifier particles. New micromechanical mechanisms have been found, which can change the toughness of some acrylonitrile–butadiene–styrene grades or improve low-temperature toughness of PP. The examples show that detailed knowledge of the morphology and micromechanical mechanisms helps to define criteria of improved properties. This “microstructural” analysis and construction of polymeric systems provides a new basis of polymer modification. © 1998 John Wiley & Sons, Ltd.