Effect of molecular weight of epoxidized natural rubber on shear strength of adhesives

The dependence of shear strength of epoxidized natural rubber (ENR)‐based adhesives on molecular weight of the rubber is studied using coumarone–indene resin, gum rosin, and petro resin as tackifiers. The adhesive was coated on polyethylene terephthalate (PET) film substrate using a SHEEN hand coater at various coating thickness. The shear strength of adhesives was determined by a Texture Analyzer. Results show a maximum at 6.63 × 10⁴ and 4.14 × 10⁴ for ENR 25 and ENR 50, respectively, after which the shear strength decreases with further increases in molecular weight for all the coating thickness. This observation is attributed to varying degree of cohesiveness which culminates at the respective optimum molecular weight of ENR. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

测量低噪声放大器的噪声系数

本文介绍了用噪声系数分析仪测量低噪声放大器的噪声系数的方法和原理。以Agilent N8975A噪声系数分析仪的使用为例,分析了Y系数法测量噪声系数的原理,和低噪声放大器测量的步骤与特殊性。     

2005年度国际市场最大200家设计公司市场分析

介绍了美国<工程新闻记录>周刊所做的2005年度200家最大设计公司的排名情况,并对这一排名进行了分析和对比.2005年度200强设计公司的国际市场营业额与去年相比增长了8.9%.中国设计公司进入200强的依然维持在2004年的13家,营业额比去年也有了很大的增长,但相对于国际市场的快速增长,中国的份额仍有待提高.     

Processing,Tensile, and Thermal Studies of Poly(Vinyl Chloride)/Epoxidized Natural Rubber/Kenaf Core Powder Composites with Benzoyl Chloride Treatment

The kenaf core powder (KCP) has been treated with benzoyl chloride (BC) in poly(vinyl chloride)(PVC)/epoxidized natural rubber (ENR)/KCP composites. The presence of BC grafted on KCP was evident by infrared analysis. PVC/ENR/KCP samples were prepared using Haake Polydrive with the temperature of 140°C and KCP loading of 5, 10, 15, and 20?phr. The processing, tensile and thermal properties of the composites were investigated. The enhancement of tensile properties showed that the treatment improved the interfacial adhesion between KCP with PVC/ENR matrix. Higher glass transition temperature and higher thermal stability after treatment with BC support the enhancement of the composites’ tensile properties.     

几种配合剂对环氧化天然橡胶性能的影响

研究了氢氧化镁、氧化锌及硬脂酸对环氧化天然橡胶（ＥＮＲ）硫化特性、硫化胶的力学性能及老化性能的影响。结果表明：加入２份氢氧化镁可有效地提高ＥＮＲ的硫化速度、拉伸强度和抗热氧老化性能；氧化锌和硬脂酸对硫化胶网络的完善是不可缺少的。用差示扫描量热法（ＤＳＣ）比较了几种防老剂（防老剂Ｄ，Ｈ．ＷＳＰ，ＭＢ．４０１０，ＳＰ）在ＥＮＲ中的防护效果。结果表明防老剂Ｄ的效果最好。以防老剂Ｄ与防老剂ＭＢ并用，加入２份氢氧化镁、２份硬脂酸和５份氧化锌，不仅可缩短硫化时间，而且可大幅度提高硫化胶的拉伸强度、扯断伸长率和老化系数。     

环氧化天然橡胶与聚丙烯共混的研究

对环氧化天然橡胶ＥＮＲ－５０与聚丙烯共混制备热塑性弹性体进行了研究。试验结果表明，选用硫黄给予体硫化体系、采用“母炼胶”二段混炼工艺，加入适量的相容剂及白炭黑，可制得力学性能较好（拉伸强度１５ＭＰａ、扯断伸长率５００％、撕裂强度８３ｋＮ·ｍ－１）、中等耐油的热塑性弹性体。透射电镜观察表明，加入相容剂及白炭黑能有效地改善共混物的界面状况，从而提高共混物的力学性能。     

EPDM/NR并用胶的复合交联

采用硫黄硫化体系和过氧化物（硫化剂DCP）硫化体系对EPDM／NR并用胶实施复合交联，研究并用比和复合交联体系对胶料的硫化特性、物理性能和耐热老化性能的影响。结果表明，在大部分并用比下，复合交联可以改善胶料的硫化特性；在硫化剂DCP和助交联剂TAIC的用量均为2份、EPDM／NR／ENR并用比为30／68．5／1．5时，并用胶的物理性能优良；以NR为主的并用胶在复合交联时硫化剂DCP和助交联剂TAIC的用量宜取1～2份。     

国际工程设计市场十年盘点:1997-2006

根据美国<工程新闻纪录>(ENR)周刊历年来关于国际市场200家最大设计商的统计情况,从市场集中度、行业和地区结构、各国设计商的市场占有状况及变化趋势对国际工程设计市场进行了分析,在此基础上重点介绍了入围200强的中国设计商在国际工程设计市场的现状及发展.     

炭黑并用对NR／ENR共混胶力学性能及减震性能的影响

对比N660研究了N330／N660、N660／N990炭黑填充体系对天然橡胶（NR）／环氧化天然橡胶（ENR）共混胶力学性能、压缩疲劳生热性能及减震性能的影响,并采用橡胶加工分析仪（RPA）对其加工性能进行了分析。结果表明：N660／N330和N660／N990两种填充体系硫化胶的力学性能,基本上是单用一种炭黑所得硫化胶力学性能的加权平均;不同粒径炭黑并用均能使共混胶的贮能模量E′下降,并且有利于拓宽NR／ENR减震材料的减震范围;不同粒径炭黑并用有利于改善NR／ENR共混胶料的加工性能。     

Enhancement of PVC/ENR blend properties by poly(methyl acrylate) grafted oil palm empty fruit bunch fiber

Effect of oil palm empty fruit bunch (OPEFB) fiber and poly(methyl acrylate) grafted OPEFB on several mechanical properties of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends were studied. The composites were prepared by mixing the fiber and the PVC/ENR blends using HAKEE Rheomixer at the rotor speed of 50 rpm, mixing temperature 150°C, and mixing period of 20 min. The fiber loadings were varied from 0 to 30% and the effect of fiber content in the composites on their ultimate tensile strength (UTS), Young's modulus, elongation at break, flexural modulus, hardness, and impact strength were determined. An increasing trend was observed in the Young's modulus, flexural modulus, and hardness with the addition of grafted and ungrafted fiber to the PVC/ENR blends. However the impact strength, UTS, and elongation at break of the composites were found to decrease with the increase in fiber loading. An increase in elongation at break and UTS and decrease in the flexural and Young's modulus was observed with the addition of PMA‐g‐OPEFB fiber compared to ungrafted fiber. This observation indicates that grafting of PMA onto OPEFB impart some flexibility to the blend. The morphology of cryogenically fractured and tensile fracture surfaces of the composites, examined by a scanning electron microscope shows that the adhesion between the fiber and the matrix is improved upon grafting of the OPEFB fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008