ISSN:
0730-6679
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The phase morphology of injection molded blends of polypropylene and ethylene vinyl alcohol copolymer (EVOH) changes dramatically throughout the sample and especially across the sample thickness. The development of laminar structure was evaluated by image analysis of scanning electron micrographs. The results indicate that laminar morphology is most likely to develop in the shear zone, as maxima in particle size and aspect ratio are observed in directions parallel and transverse to flow in this region of the sample. The laminar structure is more pronounced at high concentrations of the EVOH minor phase, and at low maleation levels of the matrix resin, as well as for low molding thickness. The influence of processing conditions such as injection speed and mold and melt temperatures appears to be small. Intensive preblending of the components in a twin screw extruder hinders the development of the laminar structure. Toluene permeability measurements show that the presence of laminar phase morphology in injection molded samples produces substantial improvements of the barrier characteristics in the materials. However, impact tests indicate that there is need to optimize the conditions employed in producing the laminar morphology, in order to avoid deterioration of mechanical properties. © 1996 John Wiley & Sons, Inc.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
