Erdmann Rafael, Kabasci Stephan, Heim Hans-Peter
Institute for Biopolymers and Sustainability (ibp), University of Applied Science Hof, Alfons-Goppel-Platz 1, 95028 Hof, Germany.
Institute of Materials Engineering, University of Kassel, Mönchebergstraße 3, 34125 Kassel, Germany.
Polymers (Basel). 2021 Apr 21;13(9):1356. doi: 10.3390/polym13091356.
Cellulose acetate (CA), an organic ester, is a biobased polymer which exhibits good mechanical properties (e.g., high Young's modulus and tensile strength). In recent decades, there has been significant work done to verify the thermal and thermomechanical behaviors of raw and plasticized cellulose acetate. In this study, the thermomechanical properties of plasticized cellulose acetate-especially its ββ-relaxation and activation energy-were investigated. The general thermal behavior was analyzed and compared with theoretical models. The study's findings could be of special interest, due to the known ββ-relaxation dependency of some polymers regarding mechanical properties-which could also be the case for cellulose acetate. However, this would require further investigation. The concentration of the plasticizers-glycerol triacetate (GTA) and triethyl citrate (TEC)-used in CA ranged from 15 to 40 wt%. DMTA measurements at varying frequencies were performed, and the activation energies of each relaxation were assessed. Increasing plasticizer content first led to a shift in ββ-relaxation temperature to highervalues, then reached a maximum before declining again at higher concentrations. Furthermore, the activation energy of the ββ-relaxation constantly rose with increases in plasticizer content. The trend in the ββ-relaxation temperature of the plasticized CA could be interpreted as a change in the predominant phase of the overlapping ββ-relaxation of the CA itself and the αα'-relaxation of the plasticizer-which appears in the same temperature range. The plasticizer used (GTA) demonstrated a higher plasticization efficiency than TEC. The efficiencies of both plasticizers declined with increasing plasticizer content. Additionally, both plasticizers hit the saturation point (in CA) at the lowest studied concentration (15 wt%).
醋酸纤维素（CA）是一种有机酯，是一种生物基聚合物，具有良好的机械性能（如高杨氏模量和拉伸强度）。近几十年来，人们开展了大量工作来验证未增塑和增塑醋酸纤维素的热性能和热机械性能。在本研究中，对增塑醋酸纤维素的热机械性能，特别是其ββ弛豫和活化能进行了研究。分析了其一般热行为并与理论模型进行了比较。由于已知一些聚合物的ββ弛豫与机械性能有关，醋酸纤维素可能也是如此，因此该研究结果可能特别引人关注。然而，这需要进一步研究。用于CA的增塑剂三醋酸甘油酯（GTA）和柠檬酸三乙酯（TEC）的浓度范围为15至40 wt%。进行了不同频率下的动态热机械分析（DMTA）测量，并评估了每次弛豫的活化能。增塑剂含量增加首先导致ββ弛豫温度向更高值移动，然后达到最大值，在更高浓度时又再次下降。此外，ββ弛豫的活化能随着增塑剂含量的增加而不断上升。增塑CA的ββ弛豫温度趋势可以解释为CA本身重叠的ββ弛豫和增塑剂的αα'弛豫（出现在相同温度范围内）的主要相的变化。所用增塑剂（GTA）的增塑效率高于TEC。两种增塑剂的效率均随增塑剂含量的增加而下降。此外，两种增塑剂在研究的最低浓度（15 wt%）时（在CA中）都达到了饱和点。
