Micromechanical behavior of branched polystyrene as revealed by in situ transmission electron microscopy and microhardness

The internal structure and failure of crazes in linear and long-chain branc hed poly(styrene) (PS) were investigated by means of in situ transmission e lectron microscopy (TEM). It was found that long-chain branched PS presents more finely fibrillated up to homogeneous crazes at room temperature inste ad of the typical fibrillated ones for linear PS. The failure of homogeneou s crazes in long-chain branched PS indicates a more ductile behavior than t he fibrillated ones. The microhardness of these materials was measured, and it was seen that the hardness value increased with increasing amount of lo ng branches in the PS. In addition, the rate of creep under the indenter (c reep constant) for these materials was investigated. The lowest value for t he creep constant corresponded to the PS sample with the largest amount of long branches.