EFFECT OF SKIN-CORE MORPHOLOGY ON IMPACT FRACTURE OF POLY(BUTYLENE TEREPHTHALATE)
EFFECT OF SKIN-CORE MORPHOLOGY ON IMPACT FRACTURE OF POLY(BUTYLENE TEREPHTHALATE)
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DOI：
10.1002/app.1975.070190621
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发表时间：
1975-01-01
影响因子：
3
通讯作者：
PRATT, CF
中科院分区：
文献类型：
--
作者：
HOBBS, SY;PRATT, CF
通过光学显微镜、x射线衍射和密度测量，研究了注塑成型聚对苯二甲酸丁二酯样品皮芯形貌的变化。在模具温度从70°F到250°F的范围内，从450°F和510°F的熔体成型的样品被发现具有非球晶皮肤，其厚度与加工温度成反比。在模塑棒的表皮或核心区域观察到很少的方向。给出了密度分布图。在有凹口的棒材上获得的冲击数据表明，随着蒙皮厚度的增加，冲击强度显著增加，尽管最大蒙皮厚度仍小于几百微米。这种行为持续到以~ 50°C为中心的韧脆转变。给出了断口显微图和高速应力应变曲线，并利用它们对断裂过程进行了定性描述。在室温下，试样出现弹性变形，直至断裂点，而在较高温度下，观察到广泛的剪切变形。在每种情况下，破坏最终都是通过疯狂-破裂机制发生的。
Variations in the skin‐core morphologies of injection‐molded poly(butylene terephthalate) samples have been characterized as a function of molding conditions by optical microscopy, x‐ray diffraction, and density measurments. Samples molded from 450 and 510°F melts at mold temperatures ranging from 70 to 250°F were found to have nonspherulitic skins whose thicknesses varied inversely with processing temperature. Very little orientation was observed in the skin or core regions of the molded bars. Density profiles are presented.Impact data obtained on bars with molded‐in notches demonstrate that significant increases in impact strength are observed with increasing skin thickness, although the maximum skin thickness remains less than a few hundred microns. This behavior persists through the ductile brittle transition which is centered at ∼50°C.Fracture surface micrographs and high‐speed stress‐strain curves are presented and used to give a qualitative description of the fracture process. At room temperature the samples appear to deform elastically up to the point of fracture, while at higher temperatures extensive shear deformation is observed. In each case failure ultimately occurs via a craze–crack mechanism.