Thermal and mechanical properties of epoxy composites reinforced by a natural hydrophobic sand

If a low weight percentage of crude fine fillers can improve properties of polymer materials directly without complicated chemical treatment process involved, it will be significant for many industrial applications. Our previous study indicated that a kind of Cancun natural sand could be an effective filler material for polymer composites. In this current work, the epoxy composites reinforced by this kind of natural sand particles were prepared and thermal and mechanical properties of the composites containing up to 5 wt % of the sand particles were characterized. Results showed that the highest flexural strength appears in the epoxy composite containing 1 wt % sand particles. A damage model was used to interpret the flexural properties, which showed an acceptable agreement with the experimental results. The glass transition temperature, high temperature storage modulus, and dimensional stability of the sand/epoxy composites monotonically increased with the addition of the sand particles. The sand particle/epoxy composites also displayed a noticeable enhancement in thermal conductivity. Theoretical analysis showed that in addition to conduction, other heat transport mechanisms played roles in the improved heat transmission through the composites. As a natural porous micron-scale material, Cancun sand has the potential for applications in cost-effective composites with enhanced mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Potentiometric studies of oxidation–reduction reactions with redox copolymers

Polymeric oxidants in the bead form that were macroporous styrene/divinylbenzene copolymers containing N‐chlorosulfonamide functional groups (in sodium or hydrogen form) or N‐bromosulfonamide groups (in sodium form) were synthesized and investigated to determine their oxidizing powers. The redox potentials of the N‐chlorosulfonamide/sulfonamide and N‐bromosulfonamide/sulfonamide systems were determined by potentiometric studies at different pH values with aqueous solutions of Na₂SO₃, KCN, and KSCN as reducers. The formal redox potentials of the N‐chlorosulfonamide copolymers were 0.79, 0.44, and ?0.12 V at pH's of 1.8, 8.45, and 13.6, respectively. The formal redox potential of the N‐bromosulfonamide copolymer was about 100 mV higher in comparable conditions and in solutions over pH = 5 (e.g., 0.56 V at pH = 8.56). The comparatively higher oxidizing power of the N‐bromosulfonamide copolymer was particularly evident in a strong alkaline medium (in which the N‐chlorosulfonamide copolymer was not reactive). In contrast, the N‐chlorosulfonamide copolymer showed strong oxidative properties in acidic media (in which the N‐bromosulfonamide copolymer decomposed itself). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Time and temperature effect on the linear–nonlinear viscoelastic transition threshold of a polymeric system

In the present study, the transition of a polymeric material from the linear to the nonlinear viscoelastic behavior and the determination of the nonlinearity stress threshold variation with time and temperature are investigated. For this purpose a systematic experimental program consisted of thermal and mechanical characterization of certain polymeric material followed by isothermal creep tests at different stress levels and temperatures was conducted. Through isochronal curves that occurred from creep tests, the nonlinearity threshold dependence on both time and temperature is presented. The reported results provide information that is critical for the design and development of polymer structures and components. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

氯氧镁水泥对不饱和树脂的阻燃性能与阻燃机理研究

采用极限氧指数法、热重分析和烟密度测试法研究了氯氧镁水泥在不饱和树脂（UP）中的阻燃作用和阻燃机理。研究表明经偶联剂处理后的氯氧镁水泥对UP具有良好的阻燃抑烟效果，并通过增加UP在高温下的热稳定性和降低热失重速率等机理发挥阻燃作用：氯氧镁水泥含量在40％内对UP的力学性能影响较小，是一种新型的无机添加型阻燃剂。     

叶子花红色素提取工艺的优化

本文研究了用树脂吸附和分离叶子花红色素，比较了4种树脂对叶子花红色素的吸附，在叶子花红色素提取过程中用AB－8树脂吸附，洗脱剂用40％的乙醇，洗脱效果好，且AB－8树脂使用20次后吸附性能仍稳定。     

混合C=9制备壬基酚的研究

研究了以强酸性阳离子交换树脂为催化剂，以混合C9^=为原料制备壬基酚的工艺条件及树脂的再生方法，并考察了催化剂及再生剂的使用寿命。结果表明，混合C9^=可用于制备壬基酚，在110℃、苯酚与C9^=物质的量比为2．5、催化剂与C9^=质量比为30％的条件下连续反应64h，C9^=平均转化率达到85．9％，催化剂可反复多次再生使用，并具有较长的使用寿命。     

中温固化3251树脂体系的研究

３２５１系促进剂Ｄ／取代双氰胺／ＣＴＢＮ－双酚Ａ环氧树脂体系，树脂体系各组份互溶性好且溶于丙酮。可制备优质均匀的预浸料，该体系能满足中温固化成型工艺要求，用Ｅ玻璃布增强的复合材料具有良好的力学性能及湿热老化性能。     

以三氧六环为交联剂的COPNA树脂的合成与性能研究

以三氧六环为交联剂，萘、萘酚、蒽及其混合物为单体，可在对甲苯磺酸或三氯乙醚催化下，在８０～１６０℃下反应得到未交联的缩合多核芳香烃树脂。对聚合反应机理作了一定的研究，并提出了聚合机理。以萘酚或萘为单体的树脂的交联较为困难，而在萘中加入蒽，不但可大大提高反应速率，也可使所得树脂的交联变得容易。交联后树脂在氮气中的热降解起始温度在４００℃左右。     

常温生产微粒状PVB树脂的研究

介绍了用常温法生产微粒状 PVB 树脂的新工艺,从而简化了传统法低温生产 PVB 树脂的工艺和设备,减少了设备投资,节省了动力和能源消耗,降低了生产成本。     

环境湿度对贮存树脂的影响EI

通过对中温固化环氧树脂ＤＳＣ、扭辫分析、凝胶时间、粘度、力学性能的测定，固化反应活化能的计算，研究了在贮存树脂的过程中环境湿度对树脂的固化反应和性能的影响。