Fig. 4 shows that the loss modulus at low temperature decreased with increasing temperature and increased with the addition of cellulose in the starch–gelatin polymer matrix as reported previously for starch-based composites reinforced with lignocellulosic reinforcements [14], as well as for bacterial polyester (polyhydroxybutyrate-covalerate, PHBV) reinforced with maple fibers [46]. The authors also reported that loss modulus increases with fiber content.
Loss modulus represents the viscous response of the material. But for the starch–gelatin polymer matrix, the loss modulus increased between 90 and 110 °C indicating an increased in viscosity due the presence of starch which has not pre-viously been observed [54]. Biliaderis et al. [55] determined the gelatinization temperature of starches of different types between 82 and 99 °C, being higher for of high amylose corn starch. Other studies showed that around 90 °C the behavior of starch is like a gel [56].
To understand this behavior, the values of tan delta are presented in Fig. 5 where two clear transitions can be observed. The first one between 45 and 75 °C was associated to the gelatin relaxation as reported by Farris [54] in gelatin–pectin films.
Authors related the transition with amino acids (proline and hydroxyproline) contained in gelatin as rigid blocks [57]. The second transition at 95 °C was related to the starch in the polymer matrix as reported by some authors (85–90 °C) for injection molded starch [15]. Since the gelatinization temperature was found to be around 70 °C under shear conditions
[22], the authors reported an increase in gelatinization temperature with increasing heating rate. There are two behavior related with viscosity in the polymer matrix corresponding to starch. The first one is viscosity increase due to water disso- lution (moisture content), subsequently the polymer matrix acting like a gel.
Finally, adding cellulose as reinforcement in the polymer matrix, the tan delta behavior exhibited a transition around 67 °C, which was related to cellulose–gelatin interactions, similar as in thermogravimetric curves where a peak at 65 °C
was observed. Also, it is clear that the addition of cellulose increased the elasticity of the polymer matrix (lower tan delta), reducing also its viscosity. That can explains why the thermal stability of the parison matrix reinforced with cellulose remained unlike parison matrix without reinforcement. Lower tan delta in starch composites can be associated with a reduc- tion in mobile units, as observed in thermoplastics [14], and also an interfacial effect due hydrogen bonds interaction between polar components [43].
Based on the DMA results, addition of cellulose in starch–gelatin polymer matrix allows the matrix to be processed at temperatures over 90 °C. Temperatures selected were thus 60–95–90 °C with 26 rpm to limit shear and temperature
degradation of the material.
摘要
本文研究了使用水解玉米淀粉-明胶作为基质和纤维素作为增强剂的可能性，通过挤出吹塑成型生产容器。先通过动态力学分析（DMA）和热重分析（TGA）来表征化合物，以确定它们的粘弹性和热稳定性。 结果表明，最合适的加工温度应小于120℃，以避免降解。 此外，纤维素的添加降低了淀粉-明胶聚合物基质的粘度，允许化合物在低至100℃的温度下进行加工。再通过挤压吹塑获得型坯，并呈现出适合的加工特性。 总的来说，添加纤维素后，表明优质容器在切断时比未添加纤维素的容器具有更高44％的能量和更好的尺寸稳定性。
关键词：挤出吹塑；淀粉-明胶；纤维素；加工；尺寸稳定性；天然聚合物 纤维素增强的淀粉-明胶聚合物基体的挤出吹塑英文文献和中文翻译(4):http://www.youerw.com/fanyi/lunwen_204652.html