Effect of thermal treatment on structure and properties of polyester tire cords

Polyester and nylon are the mostly used reinforcing textile fibers in many industrial rubber applications. Now‐a‐days body ply of a passenger car radial is mostly made up of polyester fiber. Because of its thermoplastic nature, it undergoes some kind of thermal shrinkage during processing and vulcanization, which lead to many problems related to shape, dimension, and dimensional stability. To avoid this, polyester is subjected to thermal treatment at higher temperature. Hence, thermomechanical properties of polyester tire cords become very important. During the thermal treatment, there is not only change in shrinkage, shrinkage force, and mechanical properties but also it affects structural and morphological properties. In this work, the changes in thermomechanical properties due to heat setting have been correlated to structural and morphological changes like crystallinity, crystal size, orientation, crystal perfection, etc. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polymeric curing agent reinforced silicone rubber composites with low viscosity and low volume shrinkage

A new type of polymeric curing agent (PCA) was synthesized to improve processing property, increase mechanical properties, and decrease volume shrinkage of silicone rubber. The PCA was prepared by co‐hydrolysis condensation of dimethyldiethoxysilane (DDS) and polyethoxysiloxane, then modified by hexamethylcyclotrisilazane (D₃^N). Commercial silica and tetraethoxysilane (TEOS) were used as controls simultaneously. The properties of polydimethylsiloxane (PDMS) composites were characterized by shear viscosity measurements, room temperature mass loss, linear volume shrinkage, stress‐strain tests, swelling behaviors and thermogravimetric analysis (TGA). PDMS composites using PCA show lower shear viscosity than those using commercial silica. Compared with the traditional PDMS/TEOS curing systems, PDMS/PCA curing systems behave relatively lower volume shrinkage, better reinforcement and thermal properties. In short, PCA acts as a good compromise in providing the best balance of processing property, volume shrinkage, mechanical properties and thermal stability in silicone rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Vulcanization shrinkage of rubber articles with rigid armoring parts

This paper discusses the shrinkage characteristics of armored (reinforced) rubber articles for two types of boundary conditions: (a) cases where the armoring material is neither flexible nor thermoexpansive, and (b) cases where the armoring material has a finite thermal expansion between room and vulcanization temperature. A quantiative analysis of shrinkage strains and stresses is developed for the two boundary conditions.     

Morphological aspects of rubber fracture and wear

Morphology of carbon black (CB)‐filled rubber was studied with AFM and SEM and the classification of filler agglomerates, based on their internal structure and filler–matrix interactions, has been proposed. It varies according to the activity of CB and the kind of rubber. It has been shown that fracture of rubber starts either inside filler agglomerates (de‐cohesion) or in a filler–matrix interphase (de‐adhesion) initiating wear of the material. Microscopic observations correlate well with TGA and EPR data of wear debris collected during friction of rubber. The increase of thermal stability of CB and the appearance of additional spin signals, respectively, for elongated samples or debris, are proposed to be associated with de‐cohesion or de‐adhesion of the agglomerates. New approach to the fracture of rubber called “fatal agglomerate concept” is presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

4种网格结构模具用硅橡胶性能研究

分析了网格结构模具用4种不同的室温硫化硅橡胶的性能结果表明,该4种硅橡胶均具有较小的线收缩率及较长的凝胶时间,但加成型室温硫化硅橡胶较缩合型硅橡胶具有突出的室温力学性能、热稳定性及热线胀性能,完全满足用于制作网格模具的硅橡胶要求.     

热收缩聚酯薄膜的研制

在聚酯中添加改性单体后,分子链空间位阻增大,共聚酯的结晶能力下降,热收缩性得以提高。并研究了以此共聚酯为原料,采用间歇干燥、单向拉伸、常温冷却、松弛定型的成膜工艺。     

废橡胶胶粉在砂浆混凝土中应用的研究进展

综述了国内外利用废旧橡胶胶粉对砂浆混凝土改性的研究进展和研究前景.研究表明,在水泥砂浆混凝土中掺加废橡胶胶粉可以有效改善混凝土的收缩性能,提高其韧性、抗冲击性能、抗疲劳性能、抗冻性能,但同时混凝土的强度和弹性模量也会显著下降;而通过对胶粉进行表面改性后,可以有效改善其对强度的影响.该研究将有望应用到公路路面混凝土材料上.     

新型防漏涂料的制备与性能研究

一种以树脂、橡胶为基料,以膨润土为功能材料的新型涂料,遇水自行膨胀,可作为优良的防漏材料,亦可在一定场合发挥其特有的吸水膨胀功能。     

Thermal diffusivity of rubber compounds

Abstract

During the vulcanisation process, rubber compounds are heated to temperatures of ～200°C and then cooled. An increase in temperature occurs in rubber tyres during use as a result of heat produced by repeated deformation. This temperature increase can be so high that it can cause tyre destruction. From this point of view, knowledge of thermal diffusivity data of rubber compounds and reinforced rubber is very important. Despite thermal diffusivity being a crucial value, which determines the rate of heating or cooling of solid bodies, only limited data of this kind are available in the literature for elastomers. A new method, developed especially for determining the thermal diffusivity of thick fibre composite materials and reinforced rubber, has been used to measure the thermal diffusivity of rubber compounds. Both the content and the type of rubber and carbon black determine the thermal diffusivity. The content of other components, however, has a very limited influence on this parameter.     

Damping characteristics of chlorobutyl rubber/poly(ethyl acrylate)/piezoelectric ceramic/carbon black composites

In this study, a new kind of damping composite consisting of chlorobutyl rubber, poly(ethyl acrylate), piezoelectric ceramic (PZT), and carbon black (CB) was prepared, and some efforts were made to characterize the damping behavior and explore the damping mechanism. The damping behaviors of the composites were mainly decided by the contents of CB and PZT. When an external vibration was exerted on the composites, the mechanical energy of vibration was transformed into electric energy by PZT; if the resistance was adjusted to a suitable range by the variation of the CB content, the composites could behave as semiconductors: the electric energy could not be transferred to the surface of the material but rather was dissipated as thermal energy. For this system, when the contents of CB and PZT were between 10 and 30 vol %, respectively, the volume resistivity was between 10⁵ and 10^9.5 Ω cm, and a good damping performance could be achieved. On the basis of the results, a theoretical model is proposed to explain the damping performance of the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

耐热EPDM汽车多楔带产品的研制

以三元乙丙橡胶（EPDM）为主胶品种,骨架材料选用EPDM浸胶处理的高模量低收缩聚酯线绳,表面织物选用涤棉布,在压缩层胶料配合中加入预处理短纤维,研制出一种新型耐热EPDM汽车多楔带产品。所研制的EPDM多楔带采用四轮疲劳试验机进行动态疲劳寿命测试,运行450h停止试验,检查皮带完好,未出现任何裂纹、掉楔、起球和断裂等失效现象,并且聚酯线绳界面粘合良好,完全满足现代汽车对传动带的要求。     

Anisotropic aspects of the environmental stress cracking of acrylonitrile-butadiene-styrene and styrene acrylonitrile copolymers in methanol

Critical strains causing environmental stress cracking of injection-molded poly(acrylonitrile-butadiene-styrene) (ABS) and poly(styrene-acrylonitrile) (SAN) plaques were determined upon exposure to methanol. Measurements were obtained for samples strained either parallel or perpendicular to the melt flow direction and for samples located at various distances from the mold gate. Critical strains were significantly higher in the direction parallel to the melt flow compared to the transverse direction. The degree of anisotropy increased with increasing rubber content. For ABS containing 46 percent rubber, the critical strain at one point was determined to be 2.99 percent in the direction of melt flow, but only 0.47 percent in the orthogonal direction. For this material, critical strains determined parallel to the melt flow decreased with distance from the gate; whereas, critical strains for SAN and ABS containing 30 percent rubber remained essentially constant. Orientation of the plaques was assessed using shrinkage determinations and a thermal conductivity technique. Though a straightforward correlation of orientation with critical strain is observed for ABS, a similar relationship is not observed for SAN. These results suggest that although stress cracking occurs in the glassy matrix of ABS, it is the dispersed rubbery phase which controls the magnitude of strain required to initiate cracking.     

A study on the effect of cross-linkers on pervaporation performance of room temperature vulcanised silicone rubber membranes for butanol recovery

As a rising membrane separation technology, pervaporation (PV) has been regarded as one of the most promising separation technology applied in separation of azeotropic mixtures due to its high selectivity and low energy consumption. In a PV process, separation process mainly occurs in the PV membrane, so it is of significance to develop a membrane with high performance. Room temperature vulcanised (RTV) silicone rubber is a kind of membrane material possessing good hydrophobicity and low glass transition temperature. It is widely used in the recovery of organic compounds from their dilute aqueous solutions. In this paper, RTV silicone rubber membranes were fabricated by a typical one-pot method and characterised by Fourier transform infrared spectroscopy, thermal gravimetric analysis, water contacting angle, differential scanning calorimetry, scanning electron microscopy and swelling experiment. The membranes were used in PV recovery of n-butanol from its dilute aqueous solution (about 1?wt-%). The influences of temperature and cross-linkers on the performance of PV were discussed at the same time. In conclusion, RTV silicone rubber membrane cross-linked by vinyltrimethoxysilane (WD-21), which obtained membrane selectivity of 82.9 with butanol permeability of 1.1_?×_?10⁶ Barrer at 50°C, got the best performance.     

热塑性弹性体在包覆成型方面的应用

热塑性弹性体是一种兼具橡胶和热塑性塑料特性,在常温显示橡胶高弹性,高温下又能塑化成型的高分子材料。也是继天然橡胶、合成橡胶之后的所谓第三代橡胶。通过包覆成型技术,热塑性弹性体使得制品具有更好的手感和外观,增加了制品功能性和附加值。随着人们对生活质量提出越来越高的要求,热塑性弹性体在包覆成型方面的应用越来越广泛,概述了包覆成型工艺、粘接机理及目前应用情况。     

舒适性改性涤纶树脂的研制

主要论述了将改性剂ＳＩＰＧ、ＰＥＧ与ＢＨＥＴ进行共缩聚制备舒适性改性涤纶。探讨了改善ＰＥＧ热稳定性的途径，以及共聚酯的制备和热性能．结果表明改性共聚酯能在常规聚酯生产装置上制备，所制得的共聚酯的Ｔｇ、Ｔｃ、Ｔｍ、Ｔｄ（起始）均略低于常规ＰＥＴ；但可纺性良好．由该切片制得的纤维有良好的吸湿性和抗静电性，是一种开发高仿真丝绸纺织产品的优良原料．     

半干硬混凝土外方内圆偏心约束收缩试验

采用外方内圆偏心约束试验方法对半干硬高掺量橡胶集料混凝土及未掺橡胶的半干硬普通混凝土进行约束收缩试验,并用静态电阻应变仪采集钢环内表面0°区、90°区、180°区在120 h内的环向应变值.试验结果表明:6组外方内圆偏心试件开裂截面均处在试件最窄处(0°区);半干硬橡胶混凝土早期收缩量及收缩率小于半干硬普通混凝土;半干硬橡胶混凝土试件开裂时间晚于半干硬普通混凝土,其前者裂缝宽度小于后者;所测应变值也首次验证了:0°区>90°区>180°区这一规律.计算0°区/90°区和0°区/180°区应变相对值,发现这两个值随时间变化趋于稳定.这表明,用静态线弹性有限元模拟外方内圆偏心约束收缩试验有其合理性.     

碱磷渣-绿色胶凝材料干缩性的研究

本文主要以工业废渣—磷渣（钢渣作为细集料）为主要原料,通过球磨机将磷渣细磨至一定细度作为胶凝材料原料粉,添加固体或液状化学激发剂而制备出的一类绿色胶凝材料。针对此类胶凝材料干缩率较大的缺点,通过掺加自制的膨胀剂AG、SG、CaO等有效地降低了碱磷渣胶凝材料的干缩性; 另外,随着MgO系膨胀剂掺量的增加,有一定的补偿干缩效果,但其补偿干缩效果相对于钙矾石系的膨胀剂较差; 减缩剂-A对于碱磷渣胶凝材料的干缩有一定的效果,但相对于钙矾石系的膨胀剂产生的补偿效果较差。     

SHRINKAGE OF POROUS MATERIALS DURING MICROWAVE DRYING

The dissipation of electromagnetic energy inside a material creates a thermal imbalance state producing some reactions different from those observed through slow classic drying processes. Important drying rates obtained by microwave application can be understood by taking into account induced pressure gradients which greatly accelerate the thermomigration mechanism and thereby modify the physical properties of the product. The shrinkage of porous materials during the drying stage is very sensitive to the internal vapour pressure.The quality of such products depends on the shrinkage behaviour, and it is therefore interesting to study this phenomenon in order to control the characteristics of the product. This study is an experimental approach leading to a theoretical model describing the shrinkage mechanism. This model is developed from results obtained by a computer controlled measurement system allowing to regulate the drying kinetics.     

车用甲醇汽油的溶胀性研究

采用浸泡法,对汽车上常用的几种橡胶材料分别进行汽油和甲醇的溶胀性试验,最后找出可用于甲醇汽油中的抗溶胀性较好的橡胶材料。试验结果表明:甲醇对某些橡胶材料具有很大的溶胀危害,必须选用抗溶胀性较好的橡胶材料制作甲醇汽油的燃油供给系统的配件。