木粉填充聚乙烯复合材料的研究

采用木粉对聚乙烯(PE)进行改性，研究了树脂牌号、引发剂、接枝单体对相容剂性能的影响以及木粉的粒径、水含量及相容剂用量等因素对聚乙烯／木粉复合材料性能的影响，通过SEM(扫描电镜)对材料结构进行了表征。结果表明：复合材料的弯曲性能随木粉用量的增加而大幅度提高，耐热性能也有明显改善，而冲击性能则迅速下降；木粉的粒径对复合材料弯曲性能的改善不大，木粉水含量对复合材料的弯曲性能则有较大影响；相容剂用量在10％以上，可提高复合材料的弯曲性能，对冲击性能影响不大。     

High-pressure catalytic and thermal cracking of polyethylene

The thermal cracking and catalytic cracking processes of low-density polyethylene were studied in a closed autoclave. The compositions of gaseous and liquid products were analysed by means of GC/FID and GS/MS chromatographic methods. The fractional composition of liquid products was found by distillation. Increased temperature of PE depolymerisation process increases the production of gaseous products and low-boiling liquid compounds; more aromatic hydrocarbons are formed instead of alkenes. When a lower temperature and longer time are adopted for the process to reach the assumed conversion, more straight chained hydrocarbons are produced. The acidic aluminosilicate catalyst yields more low-boiling liquid fractions, more isoalkanes and more aromatics. The neutral alumina is favourable for the production of alkenes and vacuum gas oil fraction in comparison to a non-catalytic process. The Ni–Mo/Al₂O₃ catalyst is efficient in hydrogenation of depolymerisation products. The reaction products contain only saturated compounds then and no aromatics are formed.     

低雾化低挥发性汽车用新型聚氨酯泡沫塑料助剂

康普顿公司开发了一系列适用于消除或减少汽车内饰件中胺扩散或雾化的添加剂，其中包括快速、有效的生产用零扩散催化剂和低雾化表面活性剂。该系列添加剂能大大降低泡沫制品中的胺扩散，与异氰酸酯和多元醇原料能组成最佳组合，以保持良好的泡沫物理性能。     

螺旋藻泡载分离法采收的实验室研究

在一种斜臂泡沫分离装置上，较为详细地研究了泡沫塔构造、起泡剂Tween 20浓度、载气流率、pH值和乙醇浓度等因素对螺旋藻泡载采收性能的影响. 结果表明，斜臂泡沫塔可明显改善藻细胞的泡载性能, 当Tween 20浓度为100 mg/L、载气流率为30 L/h及pH=11、乙醇浓度为1%(j)时，泡载采收过程的分离因子R和浓缩倍数a可分别达到5.04~6.52和2.74~4.31.     

酚醛泡沫夹芯板甲醛释放与检测初步探讨

对酚醛泡沫夹芯板中甲醛的来源、释放的影响因素以及控制方法进行了初步探讨。介绍了国内外关于人造板甲醛释放量的相关规定。根据材料的特点及甲醛释放情况,采用40L干燥器法进行了甲醛检测,并进行了讨论。结果表明:与仲裁检测法———1m3气候箱法相比较,该检测方法的结果偏差很小,当取置信水平为0.95时,检测结果的变异系数均小于10%,重现性好。     

Physical gelation of crystallizing metallocene and Ziegler-Natta ethylene-hexene copolymers

The effect of molecular architecture on the evolution of viscoelastic properties during crystallization was investigated using ethylene-hexene copolymers manufactured via metallocene (M-LLDPE) and Ziegler-Natta (ZN-LLDPE) processes. Differences in branching distribution were shown to have a drastic effect on the viscoelastic properties near the gel point. It is shown that the branching distribution rather than branch content is the determining parameter for the evolution of the rheological properties during isothermal and non-isothermal crystallization, and for the width of the solidification interval. We developed a partial melting technique for the preparation of stable critical gels of LLDPE whose viscoelastic properties correspond to the intermediate state between melt and solid. Local molecular conformation and crystallinity in these gels were characterized by Raman spectroscopy, which shows that the transition from melt-like to solid-like rheological behavior (physical gelation) in LLDPE occurs at a very low overall crystallinity of less than 5%.     

复合材料在军用舟桥装备中的应用

本文分析了舟桥装备用复合材料的优点,重点阐述了玻璃钢和泡沫塑料的特点,详细介绍了若干应用实例.     

Rate mechanisms of plasticity in semi-crystalline polyethylene

Based on our experiments on polyethylene where we have observed a constant level of plastic resistance, independent of lamella thickness exceeding 40 nm, we have fundamentally re-considered the rate controlling mechanisms of crystal plasticity in semi-crystalline polymers. In this we have not only re-examined and made modifications to the widely accepted mechanism of Young (Young RJ. Mater Forum 1988;11:210.) of monolithic nucleation of screw dislocations from edges of crystalline lamellae predicting an increase in plastic resistance with increasing lamella thickness, but we are proposing here two new modes of nucleation of both edge and screw dislocation half loops from lamella faces that are independent of lamella thickness. These two new modes of dislocation nucleation explain well the observed transition from a plastic resistance increasing with lamella thickness to one of constant resistance above a lamella thickness of ca. 35 nm in polyethylene. They also provide a more satisfactory framework to explain the temperature and strain rate dependence of the plastic resistance of polyethylene and predict the observed levels of activation volumes determined by us.     

Numerical analysis on reaction injection molding of polyurethane foam by using a finite volume method

Foam reaction injection molding (FRIM) is one of the most popular and useful processes for producing polyurethane foam with a complex geometry. A theoretical model which includes chemical reactions, foaming, and mold filling was developed to analyze FRIM. Energy balance equation was derived by considering polyurethane reaction, water-isocyanate reaction, and evaporation of physical blowing agents. Density and viscosity model was proposed for the bubble suspension, which was assumed to be a homogeneous phase. Based on the theoretical model, three-dimensional numerical simulation for mold filling of the polyurethane foam was carried out to predict flow field, flow front advancement, and density distribution during mold filling. Mold filling of a refrigerator cavity was investigated numerically. The density and thermal conductivity of the foam in the flow front was higher than those in the initially filled region.     

Penetration behavior and subsurface grafting of dansyl cadaverine and polyethylene glycol (PEG) derivatives in poly(ethylene-co-acrylic acid) (EAA) film

Dansyl cadaverine and polyethylene glycol (PEG) derivatives were grafted on the surface of EAA film and in its subsurface region through formation of amides and esters, respectively. A two-step reaction was conducted. First, EAA film was activated with PCl₅ at room temperature. Second, the acid chloride was reacted with dansyl cadaverine or a PEG derivative to form a modified film. ATR-FTIR spectroscopy and fluorometry were employed to analyze the modified films after each step. It was found that dichloromethane yielded the highest grafting efficiency, with the dansyl cadaverine penetrating throughout the ATR-FTIR analysis region (∼400 nm) in a few minutes. As the grafting depth increased with time, so did the amount of fluorescence intensity of grafted dansyl cadaverine. ATR-FTIR spectra for PEG grafting indicated that the acid chloride peak decreased with time, while the ester peak increased. However, hydrolysis occurred at later times, consuming the acid chloride groups within the film. A marked decrease of static water contact angle was observed for EAA grafted with PEG99 (PEG that contains 99 ethylene glycol repeat units), almost 40° lower than that of neat EAA (∼99°). For other PEG-grafted films, the surface hydrophilicity was also improved.