双向拉伸聚酯薄膜的热机械分析

应用热机械分析考察双向拉伸聚酯薄膜的热膨胀—收缩行为 ,表明其与成膜工艺 ,尤其是与热定型工艺之间有一定的相关性     

A method for continuous monitoring of bond formation between rubber and reinforced wire

The integrity of a high performance, steel-belted tire is heavily dependent on the adhesion of steel reinforcement to rubber. A bronze coating, having a nominal composition of 98.5% Cu (the balance being Sn), is plated on tire bead wire to promote adhesion of the steel reinforcement to rubber.

Pull-out force is the current standard for evaluating adhesion as recommended by ASTM. This paper describes an in-situ, continuous monitoring system designed to detect the rate of adhesive bond formation between rubber and steel reinforcement during the vulcanization process. Parameters such as oxide chemical structure and thickness were investigated to assess the rate of bond formation during vulcanization and their effect on adhesion.

Results proved that this monitoring technique is an efficient, reproducible, and reliable technique for studying the interfacial interactions occurring between steel reinforcement and rubber during vulcanization.     

Are chemical alarm cues conserved within salmonid fishes?

A wide diversity of fishes possess chemical alarm signalling systems. However, it is not known whether the specific chemicals that act as alarm signals are conserved within most taxonomic groups. In this study we tested whether cross-species responses to chemical alarm signals occurred within salmonid fishes. In separate laboratory experiments, we exposed brook charr (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) to chemical alarm signals from each of the three salmonid species and from swordtails (Xiphophorus helleri). In each case, the test species responded with appropriate antipredator behavior to all three salmonids alarm cues, but did not react to swordtail cues. These data suggest that chemical alarm cues are partially conserved within the Family Salmonidae. For each species tested, the intensity of the response was stronger to conspecific alarm cues, than to heterospecific alarm cues, indicating that salmonids could distinguish between chemical cues of conspecifics versus heterospecifics. These results suggest that the chemical(s) that act as the alarm cues may be: 1) identical and that there may be other chemical(s) that allow the test fish to distinguish between conspecifics and heterospecifics, or 2) that the cues that act as signals are not identical, but are similar enough to be recognized.     

Response of the Ladybird Parasitoid Dinocampus coccinellae to Toxic Alkaloids from the Seven-spot Ladybird, Coccinella septempunctata

Electrophysiological and behavioral responses of the ladybird parasitoid Dinocampus coccinellae to volatiles from the seven-spot ladybird, Coccinella septempunctata, were investigated to identify semiochemicals involved in host location. Coupled gas chromatography–electroantennography (GC-EAG) with D. coccinellae located a small peak of prominent activity in an extract of volatiles from adult C. septempunctata. The active compound was identified by coupled GC-mass spectrometry and by comparison with an authentic sample as the free-base alkaloid precoccinelline, which forms part of the toxic defense of this ladybird. Behavioral studies in an olfactometer showed that D. coccinellae was significantly attracted to the volatile extract and also to the alkaloid. Myrrhine, a stereoisomer of precoccinelline found in low amounts in C. septempunctata and in other ladybird species, was shown to be electrophysiologically active and significantly attractive. Perception of ladybird alkaloids by D. coccinellae is a rare example of toxicants acting as aerially transmitted cues for interactions between the third and fourth trophic levels.     

温敏性两亲嵌段共聚物相行为的耗散粒子动力学模拟

采用耗散粒子动力学模拟研究了由温敏性聚N-异丙基丙烯酰胺(PNIPAM)与聚己内酯(PCL)构成的两亲嵌段共聚物(PCL-PNIPAM-PCL)在水溶液中自组装的动力学过程及微相分离现象,考察了溶液浓度及温度对其相行为的影响。模拟发现不同体积分数的嵌段共聚物在水溶液中呈现出不同的自组装形貌,如球状胶束、柱状胶束、层状胶束等。温度对其在水溶液中的形貌及相变行为有着显著的影响。当温度较低时,PCL-PNIPAM-PCL于稀溶液中可形成稳定的以PCL为核,PNIPAM为壳的球形核壳胶束;而当温度升高到某一值时,在低温时所形成的球形核壳胶束将因温度的升高而转变为表面由PCL组成的多个不连续微区的多隔段胶束。这种温敏现象在耗散粒子动力学模拟中尚属首次被发现。另外,模拟中所得到的该体系的低临界溶解温度与实验测得的值也符合良好。对这一温敏现象作了较深入和细致的解释。本文工作表明耗散粒子动力学能用来研究温度对温敏性两亲嵌段共聚物相行为的影响并揭示其中的机制和一般规律。     

PCL/PVME共混物的结晶行为

采用溶液共混法制备了聚ε-己内酯(PCL)/ 聚乙烯基甲基醚(PVME)共混物,采用差示扫描量热法（DSC）研究了共混物的相容性,通过广角X射线衍射及偏光显微镜研究了共混物中PVME含量对PCL晶体结构及结晶形态的影响。结果表明,共混物的DSC曲线只出现了一个玻璃化转变温度,说明共混物为相容体系,共混物中PVME 的存在没有改变PCL 的晶体结构。     

纳米铜粉/PP复合材料的流变性能及动态力学性能研究

将纳米铜粉经硅烷偶联剂KH550处理后,按不同的配比与聚丙烯(PP)混合,经螺杆挤压制得纳米铜粉/PP复合材料,研究了纳米铜粉在PP复合材料中的分散性以及PP复合材料的流变性能和动态力学性能。结果表明:经改性后的纳米铜粉均匀分散在PP中;纳米铜粉/PP复合材料为非牛顿假塑性流体;在低剪切速率下,复合材料熔体的黏度高于纯PP的,随着纳米铜粉的含量增加,复合材料体系的表观黏度增大,高剪切速率时,纳米铜粉的添加量对复合材料的流动性能影响较小;当复合材料体系中纳米铜粉的质量分数小于或等于0.5%时,其熔体流动性能提高,储能模量小于纯PP的,当纳米铜粉质量分数大于0.5%时,其储能模量提高并高于纯PP的。     

PMMA/SMA共混体系流变行为与温度依赖性的研究

研究了甲基丙烯酸甲酯/苯乙烯马来酸酐共聚物(PMMA/SMA)体系的流变行为,探讨了SMA中马来酸酐(MA)含量对于共混体系时温叠加和温度依赖性的影响。结果表明,MA含量为12%(质量分数,下同)的PMMA/SMA12体系符合时温叠加原理,在低温下松弛时间与组分的关系存在正偏差,随温度上升浓度涨落加剧而有负偏差的情况出现;MA含量为28%的PMMA/SMA28体系时温叠加原理由于动力学不对称性而失效,在低温区域松弛时间与组分符合对数线性关系,高温区域则出现正偏差;与PMMA/SMA12相比,PMMA/SMA28具有更强的温度依赖性。     

Synthesis of polylactide‐based thermoset resin and its curing kinetics

A new class of biobased thermoset resins, methacrylated four‐armed star‐shaped polylactides (M4sPLAs), was prepared. The effect of star architecture, e.g. varying arm length, on the properties of the cured products was examined. Based on differential scanning calorimetry, the non‐isothermal and isothermal curing behaviors of these M4sPLAs were investigated. Various curing kinetic parameters were obtained and elucidated using autocatalytic reaction models. Experimental results indicate that the oligomers can be crosslinked into a rigid network within a curing time varying from several minutes to more than an hour upon thermal initiation. The curing processes of M4sPLAs with varying arm length are different and complex, as indicated by the change of various kinetic parameters, reaction orders and evolutions of activation energy under the test reaction conditions. High crosslinking density is especially effective for improving the thermal stability of polylactide, but also leads to slower degradation rate and deterioration of its impact properties. Copyright © 2012 Society of Chemical Industry     

The water state in crosslinked poly(vinyl alcohol)–collagen hydrogel and its swelling behavior

Poly vinyl alcohol (PVA) with pendent carboxyl group was synthesized and verified. The collagen was chemical crosslinked with the produced PVA under the help of crosslinker. Then, the PVA–collagen hydrogels were prepared through the repeated freezing–thawing. Since the water states in hydrogels play an important role in the performance of the product, thermogravimetric (TG) analysis and differential scanning calorimeter (DSC) were conducted to study the different states of water. The results indicated that the weight ratio of nonfreezable water to dry gel in PVA–collagen hydrogels was about 25%. Meanwhile, the swelling behaviors in distilled water and 0.9% saline were studied. The one‐phase exponential associate equation can fit the process very well. Calculated from the simulation equation, the swelling ratios at equilibrium in distilled water and saline were 14.353 g/g dry gel and 14.205 g/g dry gel, respectively. The results illustrated that the ions in solution would decrease the swelling ratio of the hydrogel. At the same time, the lyophilization might have slighter influence to the microstructure of hydrogels and should be more suitable for the swelling research than heat drying. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012