Mode of crosslinking of degradable poly(vinylpyridine N-oxide) gels

The degradation mechanism of gels from poly(vinylpyridine N-oxide) was investigated by differential scanning calorimetry, C, H, N analysis, infra-red spectroscopy and degradability tests. It was found that poly(2-vinyl pyridine N-oxide) gels, regardless of the persulphate initiator used, were weaker than poly(4-vinyl pyridine N-oxide) gels. C, H, N analysis and infra-red spectroscopy indicated that the initiator becomes an integral part of the gels. A mechanism for the formation of the gels is proposed.     

Influence of carbohydrate source on ruminal fermentation characteristics, performance, and microbial protein synthesis in dairy cows

Eight multiparous Holstein cows (676 ± 57 kg of body weight; 121 ± 17 d-in-milk) were used in a replicated 4 × 4 Latin square design to determine the effects of 4 sources of carbohydrate on milk yield and composition, ruminal fermentation, and microbial N flow to the duodenum. Four cows in one of the Latin squares were fitted with permanent ruminal cannulae. Diets contained (DM basis) 50% forage in combinations of alfalfa hay and barley silage, and 50% concentrate. The concentrate portion of the diets contained barley, corn, wheat, or oats grain as the primary source of carbohydrate. Intake of DM ranged from 24.0 to 26.2 kg/d, and it tended to be lower in cows fed the wheat-based diet compared with those fed the barley-based diet; consequently, milk yield tended to be lower in cows fed the wheat-based diet compared with those fed the barley-based diet. Cows fed the barley- or wheat-based diets had a lower milk fat content compared with those fed the corn-based diet. Ruminal fermentation characteristics were largely unaffected by the source of dietary carbohydrate, with similar ruminal pH and volatile fatty acid and ammonia concentrations for the first 6 h after the morning feeding. Dietary treatment did not affect total tract apparent digestibility of DM, organic matter, and neutral detergent fiber; however, total tract apparent digestibility of starch in cows fed the oats-based diet was higher compared with those fed the corn-and wheat-based diets. Nitrogen that was used for productive purposes (i.e., N secreted in milk + N apparently retained by the cow) tended to be lower in cows fed the wheat-based diet compared with cows fed the barley-, corn-, or oats-based diets. Urinary purine derivative (PD) excretion was similar in cows fed the barley-, corn-, and wheat-based diets; however, purine derivative excretion was higher in cows fed the barley-based diet compared with those fed the oats-based diet. Consequently, estimated microbial N flow to the duodenum was 49 g/d higher in cows fed the barley-based diet compared with those fed the oats-based diet. Improved production performance with corn and barley diets appeared to be due to greater nutrient absorption than in cows fed oats and wheat diets, rather than improved nutrient utilization efficiency.     

植物纤维地膜的研究现状与发展趋势

文章对可降解地膜,特别是以天然的植物纤维为基质的生物降解地膜的研究现状进行了较为全面的概述,包括植物纤维材料的特点,地膜的加工工艺,以及成品的性能和应用等。同时分析阐述了可降解地膜在发展过程中存在的主要问题及其发展前景,为可降解、绿色环保材料的发展提供了理论参考。     

丙烯酸接枝壳寡糖生物可降解交联剂的合成与表征

在1-乙基-3-(3-二甲氨丙基)碳化二亚胺盐酸盐(EDC)和N-羟基琥珀酰亚胺(NHS)催化作用下,采用水溶性的壳寡糖(CSO)与丙烯酸(AA)发生N-酰化反应,制备出一种新型水溶性可降解水凝胶交联剂——丙烯酸接枝壳寡糖(CSO-g-AA).用CSO-g-AA与丙烯酰胺单体共聚制备了聚丙烯酰胺水凝胶.该水凝胶可在蜗牛酶作用下降解为水溶性直链聚丙烯酰胺.采用1H-NMR、红外吸收光谱法对CSO-g-AA结构进行表征,用溴酸钾-溴化钾滴定法定量分析了CSO-g-AA中不饱和双键的含量.结果表明:该交联剂中不饱和双键的接枝率约为4％,在适当的温度、pH值和酶浓度下水凝胶经72 h完全降解.     

对降解塑料研究中若干问题的分析与探讨

对降解塑料研究中存在的若干问题进行了分析 ,并提出了解决问题的建议。     

交联透明质酸的降解及其释药性能

用己二酸二酰肼（ADH）对透明质酸（HA）进行化学修饰,制备交联透明质酸（HA-ADH）薄膜。粘度法测试表明HA-ADH是一种可降解的生物材料,并且与HA相比,HA．ADH的降解速率减慢。在此基础上,研究了以疏水性的替硝唑（TDZ）和亲水性的头孢唑啉钠（CEZ）为模拟药物的HA-ADH药物载体薄膜的释药性能。紫外-可见（UV-Vis）吸收光谱检测表明,HA-ADH是一种疏水性药物TDZ的优良缓释制荆,这是由于TDZ的疏水性和HA-ADH薄膜的缓慢溶胀和降解性能的结合而得到的,药物的释放主要受扩散机制控制。     

聚己二酸丁二醇酯-共对苯二甲酸酯基可降解塑料改性研究进展

随着人们环保意识的提高,可生物降解塑料逐步取代部分不可降解塑料,将成为一个趋势。目前,聚己二酸丁二醇酯-共对苯二甲酸酯（PBAT）,作为最具商业潜力的可生物降解塑料,具有与低密度聚乙烯相当的延展性和柔韧性,被普遍认为是当代绿色材料制造中最有前途和最受欢迎的可持续材料之一。但PBAT在力学性能、热性能、阻隔性能及生产成本等方面存在不足,其应用范围受到限制。本文旨在系统性地简述近年来PBAT基复合材料的制备方法、回顾国内外研究人员在PBAT力学性能和阻隔性能等提升方面所做的工作、并详细介绍和讨论PBAT的降解原理和降解所带来的环境风险。开发低成本综合性能优异,兼顾良好降解性、抑菌性和耐久性能的PBAT基复合材料,应当予以重视和进一步研究。     

基于煤层气水平井的可降解聚合物钻井液研制与应用

为解决清水钻进带来的煤层井壁严重失稳问题,开发出可降解聚合物钻井液,其组成为：清水+0.1%纯碱+0.5%可降解聚合物DPA+1.0%润滑剂WLA。性能测试结果表明,可降解聚合物钻井液较清水具有强的防膨性,侵入煤层深度浅,对煤岩强度影响小,稳定井壁能力强;对煤层有污染,但通过氧化型破胶液可以有效解除可降解聚合物钻井液造成的煤层污染,达到保护煤层的目的。6口煤层气U型水平井应用结果表明,可降解聚合物钻井液稳定井壁能力强,配合后期破胶液技术,综合煤层保护效果好。     

储层改造可降解暂堵剂的制备及表征

采用水溶液聚合法,以丙烯酰胺(AM)、丙烯酸钠为聚合单体,膨润土为填充剂,聚乙二醇二丙烯酸酯(PEGDA)为交联剂、过硫酸钾与亚硫酸钠为氧化还原引发剂制备了一种暂堵剂。考察了膨润土质量分数、交联剂质量分数、引发剂质量分数、丙烯酸中和度对暂堵剂性能的影响,采用FTIR和SEM对聚合物进行了表征。结果表明:当反应温度50℃、PEGDA质量分数0.02%(以单体质量为基准,下同)、引发剂质量分数0.6%(以单体质量为基准,下同)、膨润土质量分数5%(以总质量为基准,下同)、丙烯酸中和度80%时,合成的暂堵剂性能最好,吸水倍率达184 g/g,80℃水浴下,21 h完全降解。另外,2-丙烯酰胺-2-甲基丙磺酸(AMPS)和磺化沥青的引入提高了暂堵剂耐盐性及降解速度,岩心封堵实验表明封堵效果好。