Reduced susceptibility to stress whitening during tensile deformation of calcium carbonate-reinforced high density polyethylene composites

The micromechanism of plastic deformation and susceptibility to stress whitening during tensile straining of 20% calcium carbonate-reinforced polyethylene micrometric composites is investigated and compared with the un-reinforced polyethylene under identical conditions of processing. The adoption of calcium carbonate in polyethylene has two mutually opposite effects: the reinforcement and the nucleating effect. The reinforcement effect increases the bulk crystallinity and modulus, while the nucleating effect decreases the spherulite size and has a negative influence on yield stress, neutralizing the positive influence of increase in percentage crystallinity. The effective reinforcement of polyethylene by calcium carbonate reduces the susceptibility to stress whitening, and is characterized by lower change in gray level in the plastically deformed stress whitened zone in comparison to neat polyethylene. Also, the reinforcement of polyethylene alters the primary micromechanism of plastic deformation and stress whitening from predominantly crazing–tearing in neat polyethylene to wedge/ridge tearing and fibrillation in calcium carbonate-reinforced polyethylene composites. This is related to the cumulative contribution of small spherulite size and the amorphous nature of the interface.