影响塑料模压制件内应力的因素分析

主要讨论了造成塑料模压制件内应力的主要因素,包括制件造型设计不合理、模具设计不合理、成型工艺条件不正确等,并针对不同情况给出了相应的解决办法     

Recent Applications of X-ray Scattering Methods to Fibers and Plastics

Abstract

X-ray methods are potent and versatile tools for the structural characterization of matter. For our studies on semicrystalline plastics and on parts produced therefrom, we have developed special X-ray scattering techniques which are capable to deliver a wealth of structural information without the necessity to use very expensive equipment or laborious preparations of specimens. Some of the techniques utilizing linear position-sensitive detectors have been applied in the structural characterization of fibers as well. The wideangle techniques are described and their applications to selected examples, cellulose fibers and cross-sections of moldings from graphite-filled polypropylene, are illustrated.     

高性能聚酰亚胺的进展

本篇综述主要介绍聚酰亚胺的市场动态及其薄膜、模塑料和复合材料的进展。     

SMC模压工艺参数对固化收缩率影响的实验研究

应用回归与方差分析理论,通过SMC模压工艺参数对其固化收缩率影响的实验分析表明,优化模压工艺参数,特别是本文提出的两段式压制制度对降低SMC固化收缩率是有益的。SMC模压试件的固化收缩率随第二阶段模压压力降低和第一阶段保压时间的增长而减小。     

Crack propagation behavior and toughness of V‐notched polyethylene terephthalate injection moldings

The role of the skin and core regions in controlling the effects of V‐notches, on the fracture behavior of PET injection‐moldings, was correlated with their tensile and impact properties. Investigations revealed that there were three distinct fracture behaviors: ductile, semiductile, and brittle fracture transitions. The notch sensitivity factor for strength (K_S) in the ductile and semiductile transitions indicates that the fracture strength was not sensitive to ≤1.5 mm deep notches, which is considered the skin region. The introduction of core‐deep notches (>1.5 mm) resulted in a rapid increase in K_S. On the other hand, the notch sensitivity factor for energy (K_T) shows that the fracture energy was not sensitive at ≤0.5 mm deep notches. However, K_T increased drastically when notches >0.5 mm deep were introduced. The development of an anisotropic skin‐core structure in injection moldings is well acknowledged. This is revealed in a constant fracture behavior between 0.6 and 1.0 mm deep notches. Notably, there was a drastic change in the fracture pattern from ductile to semiductile at a critical 0.6 mm deep notch. The specimens experienced a mixed fracture behavior at 1.5 mm deep notch, which marks a transitional fracture pattern at the interface between the skin and core regions. Lastly, a constant fracture behavior was observed at notch depths ≥1.5 mm. Results show that crack opening, in the samples that had semiductile fracture, was a postnecking phenomenon. Before shear yielding, two shear lines that intersected at 45° were seen to originate from the crack root when a 1.2 kN load was applied. Conversely, crack opening and failure occurred simultaneously in brittle fractures. It is obvious that V‐notches provided a gradual transition in fracture behavior from the skin to the core regions, which confirms that the fracture behavior of PET injection moldings can be dependent on the skin and core structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010