气膜包覆法制备Si69改性淀粉/天然橡胶复合材料的性能

Properties of Si 69 modified starch/natural rubber composites by gas membrane coating reaction

采用气膜包覆法制得双(3-三乙氧基硅烷丙基)四硫化物(简称Si 69)改性淀粉,然后与天然橡胶(NR)共混制得Si 69改性淀粉/NR复合材料,研究了Si 69改性淀粉的疏水性,考察了Si 69用量对复合材料硫化特性、物理机械性能、加工性能及动态性能的影响,并表征了复合材料的相态结构。结果表明,经气流粉碎后淀粉的平均粒径减小,粒径分布变窄,且小粒径颗粒增加;淀粉未经Si 69改性前为完全亲水性,改性后疏水性增强,当Si 69质量分数为5.0%时表面接触角最大;随着Si 69用量的增加,混炼胶的焦烧时间和正硫化时间延长,经一次硫化的改性淀粉/NR复合材料的拉伸强度和撕裂强度均逐步提高,邵尔A硬度略有增加,扯断伸长率和永久变形有所降低,经70℃×24 h的二次硫化后复合材料的物理机械性能得到改善,但经100℃×24 h的二次硫化后,复合材料的物理机械性能下降;随着Si 69用量的增加,复合材料的Payne效应减弱,分散性和加工性能明显改善,在60℃附近的损耗因子减小,滚动阻力降低,改善了复合材料的压缩疲劳生热性能;经Si 69气相包覆处理后的淀粉颗粒在NR中分散比较均匀,界面结合增强。

Bis[3（triethoxy）silylpropyl]tetrasulfide（Si 69） modified starch was prepared by gas membrane coating reaction and mixed with natural rubber（NR） to obtain starch/NR composites.The surface hydrophobicity of Si 69 modified starch and the influence of Si 69 content on the curing characteristics,mechanical properties,processability,and dynamic properties of the composites were investigated.The morphological structure of the composites was characterized.The results showed that after pulverized by airflow pulverizer,the average particle size of starch decreased,the size distribution became narrow and the small particles increased.After modified with Si 69,hydrophilic starch became hydrophobic,and the value of contact angle reached maximum when the mass fraction of Si 69 was 5.0%.With increasing the amount of Si 69,the scorch time and optimum cure time of rubber compound increased,tensile strength,tear strength,and Shore A hardness of modified starch/NR composite increased,but elongation at break and permanent set decreased after first vulcanization.The mechanical properties of the composites were improved after post vulcanization at 70℃ for 24 h,but deteriorated at 100℃ for 24 h.With increasing the amount of Si 69,Payne effect of composites decreased,dispersibility of filler and processability of composite were improved.The value of loss factor at 60 ？栤ecreased,so that rolling resistance decreased,and compression fatigue property of composites ere improved.The dispersion of Si 69 modified starch in natural rubber was improved,and the interfacial bond between starch and NR was strengthened.