Aggregation, fracture initiation, and strength of PP/CaCO3composites
作者:
E. Fekete,
Sz. Molnár,
G.-M. Kim,
G.H. Michler,
B. Pukánszky,
期刊:
Journal of Macromolecular Science, Part B
(Taylor Available online 1999)
卷期:
Volume 38,
issue 5-6
页码: 885-899
ISSN:0022-2348
年代: 1999
DOI:10.1080/00222349908248146
出版商: Taylor & Francis Group
关键词: Aggregation;CaCO3filler;Debonding;Impact resistance;Micro-mechanical deformations;PP composites;Strength.
数据来源: Taylor
摘要:
Polypropylene/CaCO3composites were homogenized in a twin-screw compounder and then injection molded into tensile bars. Six different fillers were used in a wide range of average particle sizes between 0.08 and 12 μm. Tensile and flexural properties were measured by standard techniques, while impact resistance was determined by instrumented impact testing. Structure was characterized by light and electron microscopy, while failure initiation and propagation was studied with in situ high-voltage electron microscopy. The results showed that aggregation of particulate fillers occurs when their particle size is smaller than a critical value. This critical size depends on component properties and processing conditions. Strength and impact resistance usually decrease with increasing number of aggregates. The presence of aggregation can be detected by the use of a simple semiempirical model. Comparison of samples prepared by two different technologies showed that twin-screw extrusion and injection molding leads to relatively homogeneous composites, which was indicated by smaller deviations of the properties from theoretical predictions. In spite of the acceptable dispersion, impact resistance showed a large standard deviation, probably determined by the local variation of structure. In composites containing relatively large particles, the dominating micromechanical deformation process is debonding, while in the presence of extensive aggregation of small particles, cracks are initiated inside and propagate through aggregates. Mixed-mode failure may also occur at certain intermediate panicle sizes.
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