Studies of cyclic and linear poly(dimethyl siloxanes): 8. Light scattering measurements in good and poor solvents

Weight average molar masses (M_w) and second virial coefficients (A₂) have been measured for linear and cyclic poly(dimethyl siloxane) (PDMS) fractions in toluene at 298K and for linear PDMS in bromocyclohexane at 301K. The values of M_w are compared with those deduced previously using gel permeation chromatography, broadly confirming the values already assigned to the fractions. The values of A₂ for linear PDMS in toluene are shown to be consistent with previously published values for oligomeric linear PDMS. The values of A₂ for cyclic PDMS approach those of linear PDMS for M_w<～1000 g mol^?1 and decrease more rapidly as M_w increases in approximate agreement with theoretical predictions. In addition, the conventional relations between A₂ and the expansion factor α_s are shown to be inapplicable at low molar mass.     

Formation,structure and properties of polymer networks: theory and modelling

The application of a Monte-Carlo (MC) algorithm to account fully for loop formation in RA₂ + R′B₃ and RA₂ + R′B₄ polymerisations is described. The resulting interpretation of experimental elastic moduli of hexamethylene diisocyanate(HDI)-based polyurethane networks prepared at different dilutions shows it is essential to account for elastic losses in loop structures of all sizes. An important parameter, x, is introduced, namely the average fractional loss of elasticity per larger loop structure relative to the loss per smallest loop structure. Values of x vary between 0.50–0.60, depending on junction point functionality, reactant or network chain stiffness and number of skeletal bonds per smallest loop structure. Application of the MC calculations to the formation and resulting structure of diphenylmethane diisocyanate(MDI)-based polyurethane networks and poly(dimethyl siloxane) (PDMS) networks again predicts significant reductions in modulus due to loop structures. However, comparison with experimental modulus data shows that the reductions in modulus due to loops are outweighed by increases due to chain interactions and to topological entanglements. Electronic Publication     

Si-C型聚醚改性硅油的制备

研究了以烯丙基聚乙二醇甲基醚和低含氢硅油为原料,甲苯为溶剂,自制的催化剂,制备Si-C型聚醚改性聚硅氧烷,较适宜的合成条件为:选择相对分子量为1 000的聚醚,n(硅氢键)∶n(聚醚)=1∶1.2,反应温度90℃,催化剂用量为30×10-6,甲苯用量为总反应体系质量的25%。合成的聚醚改性硅油透明,性能优越,使用范围较广。     

用于紫禁城清代建筑琉璃瓦保护的桥式硅氧烷的制备及性能研究

紫禁城清代建筑琉璃瓦是我国琉璃技艺的精华, 但是部分现存的琉璃瓦却出现了变色、污染、开裂、风化、剥釉等损坏。本工作针对剥釉损坏, 以异佛尔酮二异氰酸酯和3-氨基丙基三乙氧基硅烷为反应原料, 设计合成了具有桥联结构的硅氧烷(BSQ), 一种新型有机无机杂化材料, 并将其用于琉璃瓦的保护。测试了保护后琉璃瓦的吸水率、接触角、色差、透气性、抗压强度等参数; 并对保护后的琉璃瓦进行了耐化学侵蚀、耐冻融实验。结果表明, 保护后的琉璃瓦具有较好的憎水性, 强度得到提高, 釉面剥落现象得到明显的抑制。     

含氢聚硅氧烷/醋酸乙烯酯/N-羟甲基丙烯酰胺三元共聚乳液的研究

采用含氢聚硅氧烷（PHMS），醋酸乙烯酯（VAc)及N－羟甲基丙烯酰胺（NMA）进行三元乳液共聚反应，得到了PHMS／VAc/NMA共聚乳液，讨论了PHMS用量对单体转化率，乳液稳定性，流变性的影响。结果表明：随着PHMS用量的增加，单体转化率下降，体系粘度增加，机械稳定性和冻融稳定性增加，电解质稳定性下降；该其聚物乳液为假塑性流体，具有良好的成膜性，机械稳定性和耐冻融稳定性。     

聚二甲基硅氧烷涂层材料的研究

采用一定粘度的聚二甲基硅氧烷为基体,加入适量填料和助剂,成功制备了室温硫化硅橡胶涂层。研究了气相法SiO2和交联剂对涂层材料的影响,并进行了TG和SEM测试。研究结果表明：填料的添加明显改善了涂层的力学性能和耐高温性能,拉伸强度迭1．42MPa,可耐温288℃;并且该涂层有较好的耐水和耐酸、盐性能,耐碱性能有待进一步改善。     

建筑防水涂料用硅丙乳液的制备与性能

介绍了有机无机复合建筑防水涂料用硅丙乳液的研制背景、制备方法及主要性能。所制备的硅丙乳液有机硅含量达12％，其与水泥和细砂集料混合均匀后形成的有机无机复合防水涂料对常用建筑材料粘接力强，形成的弹性胶膜吸水率低、防水性好、耐老化性高、产品性能稳定。     

亲水性聚醚/氨基硅烷乳液成膜形貌及应用

利用透射电子显微镜(TEM)、纳米粒度仪、扫描电镜(SEM)仪等仪器,对亲水性聚醚氨基硅(HPEAS)乳液的粒径及其分布、在纤维表面的成膜形态进行了表征.结果表明:亲水性聚醚氨基硅乳液的平均粒径为30 nm,Zeta电位为+25.5 mV,其在纤维表面包裹有一层树脂膜,能导致纤维表面的条纹状沟壑消失,使纤维表面相对光滑.当硅乳用量为4~5 g/L时,经整理的织物弯曲刚度明显降低,白度基本不变,静态吸水时间仅为2.16 s,保持纤维原有的风格.     

有机硅氧烷改性VAE乳液的研究

在醋酸乙烯-乙烯共聚乳液（vAE乳液）聚合过程中添加有机硅氧烷单体制备改性VAE乳液。对比分析了不同种类、不同用量的有机硅氧烷对改性vAE乳液性能的影响。确定了有机硅氧烷单体在vAE乳液聚合过程中的最佳添加方式,筛选了聚合引发体系。研究表明,在反应过程中以H2O2--ZFS作为氧化-还原引发体系,选用长链的含水解阻碍官能团的硅氧烷,有机硅氧烷采用后添加的方式,能够合理而有效地控制反应节奏。制备出性能优异的改性VAE乳液。     

耐水的硅酸盐膨胀型防火涂料的研制

优选出防火性能优良的以水玻璃为基料的膨胀型防火涂料的配方,并找到添加硅氧烷酯以改进耐水性的方法。