Chen Shia-Chung, Jien Ming-Yuan, Hsu Chi-Chuan, Hwang Shyh-Shin, Feng Ching-Te
R&D Center for Smart Manufacturing, Chung Yuan Christian University, Taoyuan 32023, Taiwan.
R&D Center for Semiconductor Carrier, Chung Yuan Christian University, Taoyuan 32023, Taiwan.
Polymers (Basel). 2022 Aug 10;14(16):3251. doi: 10.3390/polym14163251.
Polymers reinforced with conducting fibers to achieve electrical conductivity have attracted remarkable attention in several engineering applications, and injection molding provides a cost-effective way for mass production. However, the electrical performance usually varies with the molding conditions. Moreover, high added content of conducting fibers usually results in molding difficulties. In this study, we propose using microcellular (MuCell) injection molding for polypropylene (PP)/carbon fiber (CF, 20, and 30 wt%) composites and hope that the MuCell injection molding process can improve both electrical and mechanical performance as compared with conventional injection molded (CIM) parts under the same CF content. Both molding techniques were also employed with and without gas counter pressure (GCP), and the overall fiber orientation, through-plane electrical conductivity (TPEC), and tensile strength (TS) of the composites were characterized. Based on the various processing technologies, the results can be described in four aspects: (1) Compared with CIM, microcellular foaming significantly influenced the fiber orientation, and the TPECs of the samples with 20 and 30 wt% CF were 18-78 and 5-8 times higher than those of the corresponding samples molded by CIM, respectively; (2) when GCP was employed in the CIM process, the TPEC of the samples with 20 and 30 wt% CF increased by 3 and 2 times, respectively. Similar results were obtained in the case of microcellular injection molding-the TPEC of the 20 and 30 wt% composites increased by 7-74 and 18-32 times, respectively; (3) although microcellular injection molding alone (i.e., without GCP) showed the greatest influence on the randomness of the fiber orientation and the TPEC, the TS of the samples was the lowest due to the uncontrollable foaming cell size and cell size uniformity; (4) in contrast, when GCP was employed in the microcellular foaming process, high TS was obtained, and the TPEC was significantly enhanced. The high foaming quality owing to the GCP implementation improved the randomness of fiber orientation, as well as the electrical and mechanical properties of the composites. Generally speaking, microcellular injection combined with gas counter pressure does provide a promising way to achieve high electrical and mechanical performance for carbon-fiber-added polypropylene composites.
用导电纤维增强聚合物以实现导电性在多个工程应用中引起了显著关注，而注塑成型为大规模生产提供了一种经济高效的方法。然而，电性能通常会随成型条件而变化。此外，导电纤维的高添加量通常会导致成型困难。在本研究中，我们提议对聚丙烯（PP）/碳纤维（CF，20%和30%重量比）复合材料采用微孔（MuCell）注塑成型，并希望与相同CF含量下的传统注塑成型（CIM）部件相比，MuCell注塑成型工艺能够同时提高电性能和机械性能。两种成型技术都在有和没有气体反压（GCP）的情况下使用，并且对复合材料的整体纤维取向、平面内电导率（TPEC）和拉伸强度（TS）进行了表征。基于各种加工技术，结果可从四个方面进行描述：（1）与CIM相比，微孔发泡对纤维取向有显著影响，含20%和30%重量比CF的样品的TPEC分别比通过CIM成型的相应样品高18 - 78倍和5 - 8倍；（2）当在CIM工艺中采用GCP时，含20%和30%重量比CF的样品的TPEC分别提高了3倍和2倍。在微孔注塑成型的情况下也获得了类似的结果——20%和30%重量比复合材料的TPEC分别提高了7 - 74倍和18 - 32倍；（3）尽管单独的微孔注塑成型（即没有GCP）对纤维取向的随机性和TPEC影响最大，但由于不可控的发泡泡孔尺寸和泡孔尺寸均匀性，样品的TS最低；（4）相比之下，当在微孔发泡工艺中采用GCP时，获得了高TS，并且TPEC显著提高。由于实施GCP而具有的高发泡质量改善了纤维取向的随机性以及复合材料的电性能和机械性能。一般来说，结合气体反压的微孔注塑成型确实为实现添加碳纤维的聚丙烯复合材料的高电性能和机械性能提供了一种有前景的方法。
