In this study, we investigated the effects of short shot size, lubricant, and cotton fibers on the foaming and mechanical properties of poly(lactic acid) (PLA). The short shot filling capacity influenced the expansion ratio and void fraction of PLA and PLA/cotton-fiber dramatically, a set shot size of 45 cm³ (80%) filled part presented a relatively uniform cell morphology and the improved impact strength, while 38 cm³ (70%) filled ones exhibited an inferior cell structure, low tensile strength, and impact strength. Because of the microsize and the difficult dispersion of the cotton fiber, the tensile properties of all fiber filled solid and foamed samples decreased. Compared to the solid injection molded neat PLA, an impact strength of 52 cm³ (100%) fully filled and 45 cm³ filled foaming neat PLA climbed from 32.48 to 42.36 and 47.40 J/m, respectively. Moreover, at the 45 cm³ filled level, the impact strength of 10 wt % cotton fiber added composite is 31.24 J/m, a 3.8% slight decrease was calculated compared with the solid neat PLA. The composite with a higher fiber filling content of 20 wt % resulted in a severe cell deformation and obvious less cell asymmetry, and a less impact strength of 28.65 J/m was obtained. The filling of the cotton fiber could slightly change the crystallization behavior of PLA through the injection foaming process, and the increasing of crystallinity was limited.

中文翻译：

---

注射成型的聚丙交酯/棉纤维复合材料的起泡行为和力学性能

在这项研究中，我们调查了短射径，润滑剂和棉纤维对聚乳酸（PLA）发泡和机械性能的影响。短弹填充量极大地影响了PLA和PLA /棉纤维的膨胀率和空隙率，填充量为45 cm ³（80％）的填充部分设定了相对均匀的泡孔形态和改善的冲击强度，而38 cm ³（70％）的填充材料显示出较差的泡孔结构，低拉伸强度和冲击强度。由于棉纤维的尺寸很小且难以分散，因此所有填充纤维的固体和泡沫样品的拉伸性能都会下降。与固体注射成型纯PLA相比，冲击强度为52 cm ³（100％）完全填充和45 cm ³填充的发泡纯PLA分别从32.48升至42.36和47.40 J / m。此外，在填充量为45 cm ^{3的情况下}，添加10 wt％棉纤维的复合材料的冲击强度为31.24 J / m，与纯净PLA相比，计算得出的下降幅度为3.8％。具有20wt％的较高纤维填充含量的复合物导致严重的泡孔变形和明显的泡孔不对称性，并且获得了较小的冲击强度28.65J / m。棉纤维的填充可以通过注入发泡过程稍微改变PLA的结晶行为，并且结晶度的增加受到限制。