Effect of UV exposure on the microstructure and mechanical properties of long fiber thermoplastic (LFT) composites
Effect of UV exposure on the microstructure and mechanical properties of long fiber thermoplastic (LFT) composites
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DOI：
10.1007/s10853-007-2444-6
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发表时间：
2008-07-01
影响因子：
4.5
通讯作者：
Dean, D. R.
中科院分区：
文献类型：
--
作者：
Goel, A.;Chawla, K. K.;Dean, D. R.
在这项工作中，研究了紫外线 (UV) 暴露对聚丙烯 (PP)/21 vol.% E-glass LFT 和纯 PP 的微观结构和动态杨氏模量的影响。显微镜观察表明，对于长纤维热塑性塑料 (LFT)，紫外线造成的损坏仅限于表面区域，仅以表面开裂和纤维暴露在表面的形式存在，而对于纯聚丙烯，则以表面开裂的形式存在。傅里叶变换红外光谱表明，随着暴露时间的延长，受损层中聚丙烯的结晶度增加，无论是纯聚丙烯还是 LFT。这是由于化学结晶，涉及将无定形断裂的聚合物链重排成结晶形式。与纯PP相比，LFT中受损层中PP的结晶度以更高的速率增加。纳米压痕结果表明，随着紫外光照射时间的延长，损伤层中PP的杨氏模量增加； LFT 的模量增加率高于纯 PP。尽管降解层的局部杨氏模量增加，但整个复合材料的动态杨氏模量随着紫外线暴露时间的延长而降低。
In this work, the effect of ultraviolet (UV) exposure on the microstructure and dynamic Young's modulus of polypropylene (PP)/21 vol.% E-glass LFT and neat PP was investigated. Microscopic observations revealed that the damage due to UV was confined to the surface region only in the form of surface cracking and exposure of fibers to the surface in the case of long fiber thermoplastic (LFT) and surface cracking in the case of neat PP. Fourier transform infrared spectroscopy showed that the crystallinity of PP in the damaged layer increased, both in neat PP as well as in LFT, with exposure time. This is due to chemicrystallization, which involves rearrangement of amorphous broken polymer chains into crystalline form. Crystallinity of PP in the damaged layer in LFT increased at a higher rate as compared to that in neat PP. Results of nanoindentation showed that the Young's modulus of the PP in the damaged layer increased, with UV exposure time; the rate of modulus increase being higher in the case of LFT than in neat PP. Although the local Young's modulus of the degraded layer increased, the dynamic Young's modulus of the overall composite showed a decrease with UV exposure time.