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Comparative study on the selective laser sintering of polypropylene homopolymer and copolymer: processability, crystallization kinetics, crystal phases and mechanical properties
Additive Manufacturing ( IF 10.3 ) Pub Date : 2020-09-21 , DOI: 10.1016/j.addma.2020.101610
Lisa Jiaying Tan , Wei Zhu , Kaushal Sagar , Kun Zhou

Isotactic polypropylene homopolymer (iPP) and copolymer (CoPP) were comparatively investigated for selective laser sintering (SLS). The processability of the polymer powders was evaluated in terms of powder morphology, powder flowability, melting behavior, and crystallization kinetics. An isothermal differential scanning calorimetry (DSC) testing protocol was employed as an effective and efficient method to facilitate the determination of suitable powder bed temperature. The results showed that the sintering window of iPP (26.3 ℃) was similar to that of polyamide 12 (PA12) (25.8 ℃), while CoPP had a narrower sintering window (2.2 ℃), making it much less tolerant to temperature deviations that occur during printing, and thus more prone to warping. The crystallization activation energies of iPP and CoPP were ∼60% that of PA12, suggesting that both of the PP materials were less sensitive to temperature fluctuations close to their crystallization temperatures. At optimal processing parameters, the ultimate tensile strength and elongation at break of the printed iPP and CoPP specimens were found to be 14.9 MPa and 1%, and 19.5 MPa and 207%, respectively. Importantly, it was established that for PP with high regio- and stereo-irregularities such as CoPP, SLS serves as a viable alternative manufacturing technique for producing PP parts comprising γ-phase crystals that are difficult to manufacture by conventional injection moulding processes.



中文翻译:

聚丙烯均聚物和共聚物的选择性激光烧结的比较研究:可加工性,结晶动力学,晶相和机械性能

对全同立构聚丙烯均聚物(i PP)和共聚物(CoPP)进行了选择性激光烧结(SLS)的比较研究。根据粉末形态,粉末流动性,熔融行为和结晶动力学评估了聚合物粉末的可加工性。等温差示扫描量热法(DSC)测试规程被用作一种有效的方法来促进确定合适的粉末床温度。结果表明,i的烧结窗口PP(26.3℃)与聚酰胺12(PA12)(25.8℃)相似,而CoPP的烧结窗口更窄(2.2℃),使其对印刷过程中出现的温度偏差的耐受性更差,因此更容易翘曲。i PP和CoPP的结晶活化能约为PA12的60%,这表明这两种PP材料对接近其结晶温度的温度波动均较不敏感。在最佳处理参数,最终拉伸强度和伸长率在印刷的断裂PP和CoPP试样分别为14.9 MPa和1%,以及19.5 MPa和207%。重要的是,已经确定对于具有高区域和立体不规则性的PP(例如CoPP),SLS是一种可行的替代制造技术,用于生产包含γ相晶体的PP零件,这些零件很难通过常规注塑成型工艺制造。

更新日期:2020-09-21
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