Experimental and numerical investigations of bi-injection moulding of PA66/LSR peel test specimens

Bi-injection moulding is a widely used process to manufacture engineering products and consumer goods. Typically, a thermoplastic is combined with rubber or another thermoplastic to create colour differences or hard and soft areas, respectively. The aim of this study was to optimise the injection parameters and processing conditions for the moulding of two-component standard peel test specimens with suitable functional properties. In this work, all parameters of thermo-rheo-kinetic behaviour were identified to predict the entire filling stage and the effect of a liquid silicone rubber cross-linking reaction during the injection moulding process. The models of Carreau-Yasuda and Isayev-Deng regarding the thermal dependence assumed by Arrhenius’ law were used. In our study, over-injection moulding is simulated and examined using finite element software (Cadmould 3D) to investigate the thermo-rheo-kinetic behaviour and the adhesion of liquid silicone rubber during the filling mould process in over-moulding. Numerical simulation results were then compared with the experimental results, and good agreement was obtained.     

Relaxation processes in the glassy state: Molecular aspects

Molecular relaxations in the glassy state of amorphous polymers are discussed, and related to the energy requirements of the various possible molecular motions involved under two broad headings: those occurring in groups pendant to the main chain and those occurring in the main chain units themselves. A variety of motions can result in relaxations in polymers with alkane side chains, whereas only rotation (or partial rotation) is possible for pendant phenyl rings. Relaxations in polymers with cycloalkane rings in the side chain can originate within the ring itself or from motion of the ring as a unit. Restricted movements of various types of backbone chain are discussed, and possible alternatives to the postulated crank-shaft motions in polymethylene chains are presented.     

对甲苯磺酸催化合成乙酸正丁酯

用对甲苯磺酸作冰乙酸和正丁醇的酯化催化剂，成功地合成了乙酸正丁酯，考察了影响反应的因素，探讨并找到了较好的反应条件：乙酸l00mmol，n(冰乙酸)：n(正丁醇)：n(催化剂)=1：3：0．006，反应时间1．5h，不另加带水剂，产率达99．14％。     

The Use of Thermogravimetry in the Study of Rubber Devulcanization

Thermogravimetry was employed to study the changes occurring in rubber vulcanizates during devulcanization carried out by microwave treatment, a new promising method of recycling rubber waste. The thermogravimetric parameters T _i , T ₅ and T _p and the compositions of devulcanizates in comparison with vulcanizates were determined. The results obtained allowed estimation of the degree of destruction of the polymer chains in response to microwave treatment and permitted establishment of the most advantageous conditions of devulcanization in order to obtain the best properties of rubber devulcanizates for reuse in rubber processing. The results demonstrated that thermogravimetry is a very useful method for investigation and control of the microwave devulcanization process. This revised version was published online in August 2006 with corrections to the Cover Date.     

亲水性聚硅氧烷改性天然乳胶的性能

以亲水性聚硅氧烷KGF-903共混改性天然乳胶,通过拉力试验、老化试验、接触角测量和扫描电子显微镜等研究了聚硅氧烷的添加量对天然乳胶力学性能、抗老化性能、亲水性能和表面形貌的影响。结果表明,KGF-903含量在1.5%时拉伸强度有最佳的改性效果;KGF-903添加量约为3%时断裂伸长率达到最大,老化前后的断裂伸长率比改性前分别提高57%和50%。随着KGF-903含量的增加,改性天然乳胶片的水接触角逐渐减小;扫描电子显微镜观察的结果表明,添加聚硅氧烷能改变乳胶的分散状态。利用小试的最佳配方(即KGF-903的添加量为1.5%)生产了2批次医用导尿管,其表面光洁度、导尿管球囊的成品率、管身硬度、连接器与导尿管排泄锥形接口所承受的拉力和充气漏斗与引流漏斗连接处所承受的拉力等均有显著的提高,有效改善了产品的质量。     

Microbial desulfurization of waste latex rubber with Alicyclobacillus sp.

A microbe with desulfurizing capability, Alicyclobacillus sp., was selected to recycle waste latex rubber (WLR). The growth characteristics of the microorganism and the technical conditions in the co-culture desulfurization process were studied. The desulfurization effect of Alicyclobacillus sp. on the WLR was characterized, and the mechanism for the microbial desulfurization of WLR was tentatively explored. The results showed that adding 5% (w/v) WLR into medium had little effect on the growth of Alicyclobacillus sp. The surfactant polysorbate 80 (Tween 80) had a toxic effect on Alicyclobacillus sp., but the growth of the microbe was vigorous if the proper technique was used: the mixing of WLR with Tween 80, followed by the addition of the mixture into the culture media. With the increase of desulfurization time, the swelling value of desulfurizated waste latex rubber (DWLR) increased, but the crosslink density decreased. After co-culture desulfurization for 8–10 days, a DWLR with good desulfurization effect was obtained. The mechanical properties of natural rubber (NR)/DWLR composite improved significantly over those of NR/WLR composite. XPS and FTIR results revealed that Alicyclobacillus sp. could break the crosslinked sulfur bonds and oxidize them to sulfones groups. The increase of O element content on the surface of DWLR was confirmed by water contact angle measurements. The relationship between the crosslink density and sol fraction of DWLR with different desulfurization times agreed with the Horikx equation, an indication that the microorganisms could break the crosslinked sulfur bonds on the surface of WLR, but leaving the main chains intact.     

Understanding the effect of filler shape induced immobilized rubber on the interfacial and mechanical strength of rubber composites

Styrene butadiene rubber (SBR) composites with silica, halloysite nanotubes (HNTs) and montmorillonite (MMT) were prepared and the interfacial and mechanical properties were compared to understand the reinforcing behaviours of these fillers based on the results of SEM, DSC, DMA, etc. Due to the formation of interparticle domain, HNTs immobilized more rubber approaching their surface than silica and MMT. Interestingly, only tightly immobilized rubber chains made contribution to the enhancement of interfacial and mechanical strength of SBR composites. This was because the tightly immobilized rubber acted as a bridge in the filler-rubber interface and induced the formation of stretched rubber chains linked filler network when the composites were loaded in tension, while loosely immobilized rubber were easy to slip off from filler surface, causing the separation between filler and bulk rubber. Therefore, silica with more tightly immobilized rubber approaching its surface showed better reinforcing effect on rubber than HNTs and MMT.     

Modeling of Anionic Polymerization of Isoprene in an Industrial Reactor

One of the most important reasons for modeling polymerization processes is to provide a tool for estimating the risks of runaway reactions in polymer industry. This is especially important for batch processes, such as anionic polymerization of isoprene or butadiene. This work presents a theoretical and experimental research of the anionic polymerization of isoprene using cyclohexane as solvent and n‐butyllithium as initiator. In the first part, a phenomenological kinetic expression is obtained that describes the anionic polymerization of isoprene initiated by n‐butyllithium in cyclohexane. In the second, the mass and energy balance equations are solved to model the anionic polymerization of isoprene in a quasi‐adiabatic batch reactor. Adjustment of reactor parameters is made using the data obtained from a laboratory reactor. The proposed model predicts adequately the obtained temperature, pressure, and conversion profiles from this set of experiments. Finally, a mathematical model is developed to predict the behavior for the anionic polymerization of isoprene in an industrial reactor.     

Preparation and properties of water‐absorbent composites of chloroprene rubber,starch, and sodium acrylate

The effects of the amounts of starch, sodium acrylate (NaAA) and dicumyl peroxide (DCP) on the properties of chloroprene rubber (CR)/starch/NaAA composites prepared by melting method were investigated. The results showed that the addition of starch improved the mechanical properties, but decreased the water‐absorbing capacity of the composite, most likely due to the decrease in the local concentration of the main water‐absorbing material sodium polyacrylate and the increase in crosslinking density of the composite resulting from the reaction between starch and CR. This reaction was verified by the vulcanized curves, DSC curves, and the cut surface morphology. The as‐prepared composite demonstrated higher water‐absorbing capacity, resulting from the incorporation of NaAA. The mechanical properties decreased with increasing the DCP loading, and the water‐absorbing ratio is the maximum at 1.0 phr DCP. The tensile strength of the composite decreased significantly after water immersion, due to the absorbed water acting as a plasticizer. The extracted component from composites after water immersion is mainly sodium polyacrylate according to Fourier transform infrared (FT‐IR) spectroscopy analysis. The morphology of the composites before and after water immersion was observed by optical transmission microscopy (OTM). The results indicated that the starch exhibits a good dispersion state, and the water‐absorbing capacity results primarily from sodium polyacrylate. Copyright © 2010 John Wiley & Sons, Ltd.     

Mechanistic aspects of the Wolff-Kishner reaction. V. The cation effect on the reaction of benzophenone hydrazone in butyl carbitol and decyl alcohol

The rate of the Wolff-Kishner reaction of benzophenone hydrazone in butyl carbitol increases as the cation of the alkoxide base is varied in the order K>Na>Li>Mg. The replacement of butyl carbitol by 1-decanol also accelerates the reaction, and an additional increase is caused by the presence of crown ether. On the basis of changes in the activation parameters, it is concluded that the reactivity of the hydrazone anion increases as the contact ion pair becomes more fully solvated and dissociated.