Sulfur Versus Non-Sulfur Containing Polyimide Adhesives for Bonding Steel

Due to their superior thermal and chemical stability, polyimides are often used as adhesives in harsh environments. This study examines the effect on bond strength of thioether sulfur in the polyimide backbone. Bonds were made using steel that was believed to catalyze the oxidation of sulfur. In addition, non-sulfur containing polyimides with similar T_g were also studied for comparison. The polymer/metal interface was studied using both the T-peel and wedge tests. No apparent effect was observed in the T-peel test with steel where the T-peel strengths of non-sulfur and sulfur containing polyimides were similar. In the wedge test, however, the sulfur-containing BDSDA/ODA bonded to steel had the smallest initial crack length of 34 mm. However, the BTDA/APB bonds tested in a dry environment had the smallest crack growth. The sulfur-containing BTDA/ASD performed best of the bonds tested in a wet environment. Metal-catalyzed oxidation of sulfur was observed to take place in the steel case, but not to an extent to have a noticeable effect on peel strength.     

凝胶过滤色谱法研究酶解过程中木聚糖分子结构的变化

采用凝胶过滤色谱法研究了木聚糖在酶解过程中分子量分布的变化。结果表明,木聚糖酶对高分子量组分的木聚糖的降解能力较差,而主要降解分子量介于15000～3000之间组分的木聚糖,使得这部分木聚糖变为分子量更低的木聚糖组分。随着酶解时间的延长,酶解得率上升,酶解产物中低聚木糖含量增多,未被酶解的木聚糖的平均聚合度上升,当酶解时间超过4h时,这种变化趋势缓慢。随着酶解轮次的增加,酶解产物中可溶性木聚糖的含量越来越少,木聚糖被降解的难度越来越大。在实际生产中,用来作为低聚木糖生产的木聚糖其聚合度应在20～100之间,酶解时间以4h为宜,重复利用未水解木聚糖的轮次以2轮为宜。     

货架喷塑前处理工艺的选择与应用

介绍了CZ99-03(7)常温锌系磷化剂在货架上的应用,根据货架构件的特点,优化货架喷塑前处理工艺,讨论了影响磷化质量的工艺因素,提出了提高磷化效果的措施以及进一步改进磷化工艺的工艺设计。     

葡萄糖-6-磷酸和果糖-6-磷酸的酶法测定

在血液、发酵液或组织液中加入磷酸葡萄糖异构酶（ＰＧＩ，ＥＣ．５．３．１．９）、６－磷酸葡萄糖脱氢酶（ＧＤＨ，ＥＣ．１．１．１．４．９）及还原型辅酶Ⅱ（β－ＮＡＤＰ），利用快速、准确的酶法检测Ｄ－６－磷酸葡萄糖和Ｄ－６－磷酸果糖浓度。对该法的专一性、精确性、准确性以及误差来源及消除方法作了讨论。对其它物质的分析作了探讨     

Enzymatic syntheses of N-lauroyl-β-alanine homologs in organic media

Enyzmatic amidation of the primary amines β-alanine ethyl ester and 3-aminopropionitrile with methyl laurate by means of immobilized lipase (Candida antarctica lipase, CAL) resulted in the formation in good yield of N-lauroyl-β-alanine ethyl ester and 3-(N-lauroylamino)-propionitrile, respectively. When 3-amino-propionitrile was used as substrate, diisopropyl ether was a suitable solvent. Changing the reaction temperature (12–80°C) did not affect the yields, and room temperature was a suitable temperature for this reaction. In the investigation of reaction conditions, the use of equimolar amounts (5 mmol) of substrate and ester, along with 0.5 g of CAL, in diisopropyl ether gave the best yield (99.3%) after 24 h of incubation at 24°C. The enzyme activity in the amidation reaction did not decrease even after six uses. With β-alanine ethyl ester hydrochloride as substrate, diisopropyl ether was unsuited as a solvent owing to the low solubility of the substrate in this solvent. In this reaction, the best yield (82.0%) was attained by using dioxane as solvent. CAL achieved higher extents of amide synthesis with long-chain than with short-chain ester substrates. The enzyme accepted only nonbulky primary amines as substrates.     

蒙脱石预处理对制备柱撑蒙脱石的促进作用研究

在制备柱撑蒙脱石的过程中，首次提出了蒙脱石的预处理工艺，并以莱西钙基膨润土为原料，研究了预处理方法、预处理时间、料浆浓度、分散剂种类及用量对蒙脱石分散程度的影响，将钙基蒙脱石颗粒分散达到0.964 μm。经过预处理后，用钙基蒙脱石直接制备柱撑蒙脱石，并用SEM、XRD、DTA-TG和SRF等进行了表征。经300 ℃焙烧2 h后，其层间距为1.262 nm，热稳定性达588 ℃，此法省去了蒙脱石的钠化改性，简化了制备工艺。     

生物转化植物纤维产酒精的研究进展

植物纤维是潜在的可再生资源，利用微生物对其进行降解、转化以实现工业化低成本生产，已成为研究的热点。从生物方法角度对植物纤维为原料产酒精的3个阶段：原料预处理、纤维素酶糖化和发酵进行全面的阐述，包括微生物及其作用机理和处理工艺等方面的内容。     

响应面法优化鸡脂酶解工艺

通过单因素实验考察了脂肪酶、乳化剂、反应温度、pH值、反应时间、酶添加量及摇床转速等影响鸡脂脂肪酶水解的因素.采用响应面分析法对反应温度、酶添加量、pH值和反应时间等工艺参数进行了优化研究.结果表明,二次多项式模型符合实验数据.反应获得较优酸值时反应参数条件为：温度46.6℃,加酶量0.5%,pH值6.4,反应时间4.33 h.     

基于LS-SVM棉针织物前处理工艺指标软测量

该文针对棉针织物前处理过程工艺指标吸水性和白度难以实现在线连续检测,且与前处理过程温度、时间、液碱浓度、双氧水浓度等影响因素具有较强非线性,难以建立精确数学模型。在分析了棉针织物前处理过程质量指标相关影响因素的基础上,采用最小二乘支持向量机建立了前处理过程工艺技术指标软测量模型,并通过实验验证了软测量模型的有效性。     

碱性蛋白酶水解豌豆蛋白的条件优化

采用碱性蛋白酶对豌豆蛋白进行水解,通过单因素试验,分析了温度、pH、酶与底物浓度比、底物浓度、水解时间对水解度影响,并在单因素试验的基础上,利用响应面分析法,优化确定的豌豆蛋白酶水解最佳条件为:温度54.5℃,pH7.9,酶与底物浓度比1.5%,底物浓度2.9%,水解时间3.0 h,最佳酶水解条件下的水解度为13.42%.