A polyamide-silica composite prepared by the sol-gel process

Summary A new kind of organic-inorganic hybrid composite was prepared by means of the sol-gel process. The polymer employed was a mixed-isomer aromatic polyamide having good solubility and thermal stability. The silica constituting the inorganic phase was produced by the hydrolysis and condensation of tetramethoxysilane. The bonding between the phases involved aminophenyl-trimethoxysilane, in which the amino group can react with the phthaloyl chloride end-capped polymer, and the methoxysilane groups undergo hydrolysis. The composition of these composites was varied by changing the linear polymer chain length and relative amount of tetramethoxysilane. The gelation time was found to range from a few minutes to several days. Thermogravimetric analyses showed that decomposition starts at approximately 450 °C. Thin films cast from materials having a relatively high silica content were opaque and rigid, but those with low silica content were flexible and transparent.     

油田用延时性高黏凝胶制备方法研究

基于改性淀粉凝胶于调剖堵水、封堵、钻完井等方面优异的使用性能及应用前景。以淀粉、丙烯酰胺(AM)为原料,偶氮二异丁腈(AIBN)为引发剂,利用淀粉同烯类单体进行接枝共聚,通过交联剂来实现共价键交联,在实验室条件下合成一种适用于中、高温油藏,成胶时间延时至2 h内可控的高强度的改性淀粉凝胶。研究了引发剂的用量、交联剂的用量、反应温度、p H值对胶体成胶性能(体系黏度和成胶时间)的影响。结果表明:在引发剂质量分数介于0.04%~0.06%,交联剂质量分数在5.1%左右,反应温度为80℃,体系p H为10时所制得的聚合物胶体性能最佳,其体系黏度对应为1 950×103 m Pa·s。     

Gelation of poly(vinyl alcohol)/water/dimethylformamide solutions and properties of dried films

The properties of solutions for syndiotacticity-rich poly(vinyl alcohol) (s-PVA)/dimethylformamide (DMF)/water systems, the gelation of the s-PVA solutions, and the properties of the dried s-PVA gel films were examined. From the results of the dissolution temperature of the polymer, the gelation temperature of the solutions, the melting temperature of the gels, and the compressive modulus of the gels, the solubility of the polymer was the highest at DMF contents of 10–20 vol %. The maximum dynamic tensile modulus of the drawn (×18) films obtained from the dried gel films with a DMF content of 10 vol % was 54.9 GPa at 20°C. The orientation of the polymer chains in the amorphous regions was higher than that in the crystalline regions. The orientation of the polymer chains in the amorphous regions for the drawn films with a DMF content of 10 vol % was higher than that for the drawn films with a DMF content of 60 vol %. The orientation of the polymer chains in the amorphous regions was considered to play an important role in the properties of high strength and high modulus. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1661–1667, 1998     

超声波湿法混炼炭黑/天然橡胶复合材料的性能研究

利用超声波的乳化均质作用,将经水湿润的炭黑与稀释的天然胶乳混合均匀,然后采用蒸发成膜法和胶凝成膜法制备胶膜(炭黑/天然橡胶复合材料),探究制膜方法及超声波处理时间和功率对胶膜性能的影响。结果表明:蒸发成膜法成膜时间过长,打开的炭黑二次结构重新团聚,胶膜中炭黑分散性差,胶膜的拉伸强度较小,而胶凝成膜法稳定性更高,胶膜中炭黑分散性好;超声波处理时间为90 s、功率为840~960 W时,超声波的乳化均质效果最好,炭黑二次结构打开程度更高,此时采用胶凝成膜法制备胶膜,成膜速度快,炭黑来不及团聚,胶膜中炭黑分散性较好和结合橡胶较多,胶膜的拉伸强度较大。     

鱼肉蛋白的热变性研究进展

为探究盐浓度对欧洲鳗肌原纤维蛋白热诱导凝胶形成性能的影响,测定了蛋白的浊度、表面疏水性和活性巯基的变化,考察了0.1、0.3、0.5 mol/L的NaCl浓度下的肌原纤维蛋白热诱导凝胶的性质。结果表明,欧洲鳗肌原纤维蛋白的浊度、表面疏水性和活性巯基分别在30、35和40 ℃开始增加。随着NaCl浓度的增加,肌原纤维蛋白的热吸收峰温度降低,而储能模量和损耗模量增加。0.5 mol/L NaCl溶解的欧洲鳗肌原纤维蛋白热诱导凝胶破断强度为98.81 g,高于低浓度NaCl溶解的蛋白热诱导凝胶。电泳结果表明,增加NaCl浓度会促进肌球蛋白重链和肌动蛋白的相互作用。根据傅里叶变换红外光谱和扫描电镜结果,发现0.5 mol/L NaCl溶解的肌原纤维蛋白热诱导凝胶具有最高的酰胺II/酰胺I强度比和最致密的网络结构。研究结果表明欧洲鳗肌原纤维蛋白在35 ℃时开始变性,提高NaCl浓度可以增强热诱导蛋白凝胶的强度和网络结构致密度,将为利用盐浓度和温度调控鳗鱼加热调理产品提供理论指导。     

黑米花色苷微胶囊的制备及其稳定性评价

以海藻酸钙为壁材,利用乳化凝胶化法制备黑米花色苷微胶囊,研究包被后黑米花色苷在高温、光照、p H条件下的稳定性,及其在模拟胃肠液中的释放性能。在海藻酸钠浓度为15 g/L,水油体积比为1∶3,壁芯比M(NaAlg)∶M(C3G)为1∶2,溶液p H值为4.5的工艺参数条件下制备的黑米花色苷微胶囊,在不同pH、温度、光照条件下的稳定性均显著高于未包被游离黑米花色苷,且在模拟胃液中能保持4h,在模拟肠液中壁材缓慢降解,释放出花色苷。基于乳化凝胶化原理的微胶囊包被技术,能提高花色苷的稳定性,实现其在体内的肠道递送和缓释。     

茶多酚对羊肉肌原纤维蛋白凝胶特性的影响

研究茶多酚对羊肉肌原纤维蛋白凝胶特性的影响,将不同添加量（0.00%、0.01%、0.05%、0.10%、0.50%、1.00%）的茶多酚加入到羊肉肌原纤维蛋白中,测定肌原纤维蛋白表面疏水性、乳化性能、保水性、质构特性,观察羊肉肌原纤维蛋白凝胶微观结构。结果表明,与对照组相比,茶多酚添加量为0.10%时,羊肉肌原纤维蛋白的表面疏水性最小,疏水基团暴露程度最轻,乳化活性指数达到最大（4.88 m2/g）,乳化稳定性指数（86.54%）和保水性（95.22%）均达到最佳;随着茶多酚添加量的增加,羊肉肌原纤维蛋白凝胶的硬度、咀嚼度、胶着度均显著上升（P＜0.05）,弹性、内聚性、回复性整体呈下降趋势（P＜0.05）。结论：添加适量茶多酚可以显著改善羊肉肌原纤维蛋白的凝胶特性,并且凝胶的微观结构更加致密、空隙更小、形状规则且分布均匀;茶多酚与肌原纤维蛋白的非共价结合和共价结合可能会影响蛋白质的功能特性,并且这种作用强度随着茶多酚添加量的变化而变化。     

加热温度对猪肉肌原纤维蛋白凝胶特性的影响

本实验研究在不同温度(50～90℃)条件下加热对猪肉肌原纤维蛋白凝胶特性的影响。结果显示：温度为70、80℃制备的凝胶保水性较好;50℃和60℃形成的凝胶颜色较深;70～90℃形成凝胶的白度基本相同,无显著差异(P＞0.05);凝胶硬度和咀嚼性随温度的升高先升高后降低,在温度为70～80℃时达最大值;浊度随着温度的升高而总体呈升高趋势,但达到70℃以上时,升高趋势变缓。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)研究发现,在45～65kD之间,在温度升高到70℃以上时,逐渐出现了明显的条带,表明部分蛋白发生了分解。表明肌原纤维蛋白在70～80℃所制得凝胶产品的功能特性较好。     

相转化法制备聚砜膜研究进展

系统概述了相转化法制备聚矾膜时聚矾含量、添加剂、凝固浴及铸膜液在空气中的蒸发时间对其结构和性能的影响。随着聚矾含量的增加,膜结构从疏松向致密转变;在铸膜液中添加适合的添加剂可制备适当结构和渗透性能的聚矾膜;在凝固浴中添加适量的溶剂,可有效抑制膜内大孔结构的形成;空气中蒸发时间的增大时,膜表面趋于疏松,当增加到一定程度后基本趋于稳定。还综述了相转化法制备聚矾膜时聚矾含量、添加剂、凝固浴及铸膜液在空气中的蒸发时间对其结构和性能的影响。