Kaczor Daniel, Fiedurek Kacper, Bajer Krzysztof, Raszkowska-Kaczor Aneta, Domek Grzegorz, Macko Marek, Madajski Piotr, Szroeder Pawel
Faculty of Mechatronics, Kazimierz Wielki University, Kopernika 1, 85-074 Bydgoszcz, Poland.
Łukasiewicz Research Network-Institute for Engineering of Polymer Materials and Dyes, Marii Skłodowskiej-Curie 55, 87-100 Toruń, Poland.
Materials (Basel). 2021 Sep 16;14(18):5346. doi: 10.3390/ma14185346.
To assess the impact of graphite fillers on the thermal processing of graphite/poly(lactic acid) (PLA) composites, a series of the composite samples with different graphite of industrial grade as fillers was prepared by melt mixing. The average size of the graphite grains ranged between 100 µm and 6 µm. For comparative purposes, one of the carbon fillers was expandable graphite. Composites were examined by SEM, FTIR, and Raman spectroscopy. As revealed by thermogravimetric (TG) analyses, graphite filler slightly lowered the temperature of thermal decomposition of the PLA matrix. Differential scanning calorimetry (DSC) tests showed that the room temperature crystallinity of the polymer matrix is strongly affected by the graphite filler. The crystallinity of the composites determined from the second heating cycle reached values close to 50%, while these values are close to zero for the neat polymer. The addition of graphite to PLA caused a slight reduction in the oxidation induction time (OIT). The melt flow rate (MFR) of the graphite/PLA composites was lower than the original PLA due to an increase in flow resistance associated with the high crystallinity of the polymer matrix. Expandable graphite did not cause changes in the structure of the polymer matrix during thermal treatment. The crystallinity of the composite with this filler did not increase after first heating and was close to the neat PLA MFR value, which was extremely high due to the low crystallinity of the PLA matrix and delamination of the filler at elevated temperature.
为评估石墨填料对石墨/聚乳酸（PLA）复合材料热加工的影响，通过熔融共混制备了一系列以不同工业级石墨为填料的复合样品。石墨颗粒的平均尺寸在100 µm至6 µm之间。为作比较，其中一种碳填料是可膨胀石墨。采用扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）和拉曼光谱对复合材料进行了检测。热重（TG）分析表明，石墨填料略微降低了PLA基体的热分解温度。差示扫描量热法（DSC）测试显示，聚合物基体的室温结晶度受石墨填料的影响很大。由第二次加热循环测定的复合材料结晶度接近50%，而纯聚合物的这些值接近零。向PLA中添加石墨导致氧化诱导时间（OIT）略有缩短。由于与聚合物基体的高结晶度相关的流动阻力增加，石墨/PLA复合材料的熔体流动速率（MFR）低于原始PLA。在热处理过程中，可膨胀石墨未引起聚合物基体结构的变化。含有这种填料的复合材料在第一次加热后结晶度没有增加，且接近纯PLA的MFR值，由于PLA基体的低结晶度以及填料在高温下的分层，该值极高。
