Haze, Glass and Surface Roughness

Spherulitic superstructures were formed at low shear strains and an oriented, row-nucleated stacked lamellar texture developed with increasing shear strain. At higher recoverable shear strain values, a fine surface roughness developed due to high melt elastic instabilities. 

The bulk haze contribution was measured by applying a very thin layer of silicone oil to the film surface prior to measurement. The predominant contribution to the haze was from the surface, and was the result of surface roughness. The surface haze of metallocene-catalysed PE films was increased by the development of spherulitic-like snrface features, which increased the surface roughness. However, Ziegler-Natta catalysed PE, exhibited relatively low total and surface haze values, which were attributed to the relatively smooth surface texture. 

Kuboky and co-workers [40] used transmission electron microscopy (TEM) to study block and white crazes in high impact polystyrene (PS). They examined the mechanism of block craze formation and found that the rubber molecules were not necessarily diffused into the entire crazes. The length of the block crazes varied before they turned to white and in some cases only white crazes were generated from the rubber particles. TEM should thus be used with caution in examining stained rubber-toughened polymers to ensure that all crazes, including the white crazes, were considered for evaluation of the extent of the deformation behaviour [41]. 

Woods and Pocius [42] prepared commercial polyolefin plastomer films, containing slip and antiblock, were blown with and without the addition of commercial polymer processing additives, at levels of 600,1,200, or 2,000 ppm. Possible detrimental affects on the films were evaluated by determination of surface tension, gloss, haze, clarity, transmittance, hot tack, heat seal, coefficient of friction and block, and the surface 

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