Peel Adhesion of Natural Rubber Bonded to Polyethylene Terephthalate: Effect of Crosslinking on Rate/Temperature Response

Laminates consisting of natural rubber (NR) sandwiched between cloth fabric and polyester film were pulled apart at various rates and temperatures in a T-peel geometry. Peel energies for joints containing uncrosslinked or lightly-crosslinked NR did not obey simple time-temperature superposition. This behavior is attributed to strain-induced crystallization during peeling. However, when the rubber was highly crosslinked, strain crystallization seems to be absent, as peel energies now can be WLF shifted to form a mastercurve.     

Adhesion Property of Benzoyl-Peroxide-Cured Epoxidized Natural Rubber/Acrylonitrile-Butadiene Rubber Blend Adhesives to Polyethylene Terephthalate Film

The loop tack, peel strength and shear strength of cross-linked epoxidized natural rubber (ENR-50)/acrylonitrile-butadiene rubber (NBR) blend adhesives were studied in the presence of coumarone-indene resin. Benzoyl peroxide was used as the cross-linking agent with dosage ranging from 1 to 5 parts per hundred rubber by weight (phr). Toluene was used as the solvent throughout the investigation. A SHEEN hand coater was used to coat the adhesive on a polyethylene terephthalate substrate at 60 and 120 μm coating thickness. The adhesive was cured at 80°C for 30 min prior to testing on a Lloyd adhesion tester operating at various testing rates from 10 to 60 cm min^?1. Results show that loop tack and peel strength of the ENR-50/NBR adhesives pass through a maximum value at 4 phr of benzoyl peroxide dosage. This observation is attributed to the increase in cohesive strength which culminates at 4 phr benzoyl peroxide loading. However, shear strength increases steadily with dosage of benzoyl peroxide due to the continuous increase in the cohesive strength as crosslinking of the rubber blend proceeds. In all cases, the adhesion properties increase with increasing coating thickness and testing rates.     

Studies on Adhesion Between Natural Rubber and Polyethylene and the Role of Adhesion Promoters

Studies on adhesion between natural rubber (NR) and polyethylene (PE) with different levels of interaction (physical and chemical) have been carried out. Ethylene propylene diene rubber (EPDM) and chlorinated polyethylene (CPE) were used as physical promoters and epoxidised natural rubber/modified polyethylene (ENR/PEm) and sulfonated ethylene propylene diene rubber/modified polyethylene (S-EPDM/PEm) were used as chemical adhesion promoters. The failure surfaces were examined with the help of scanning electron microscopy (SEM), optical photography and electron spectroscopy for chemical analysis (ESCA) techniques.

The peel strength between natural rubber and polyethylene as measured in this study is 140 J/m². With the incorporation of physical promoters such as EPDM, the peel strength increases twenty fold because of structural similarity of EPDM with PE and the rubbery nature of EPDM. Similarly, the other promoters show significant improvement in peel strength. At high temperature and low rate of peeling, the nature of failure is mainly “stick-slip” for joints with interaction promoters. The average peel strength increases with increase in test rate and decrease in test temperature for most of the joints. All the data could be shifted onto a master curve indicating that the increase in strength is a result of viscoelastic dissipation. NR/EPDM/PE and NR/CPE/PE systems, however, behave in a different way probably because they alter the nature of crack propagation at or near the interface. ESCA results of the peeled PE surface show a chemical shift of C_1S peak. SEM photographs also indicate interaction at the interface when modifiers are used. An increase in crystallinity of PE from 30% to 64% and modulus increase the peel strength of NR/PE joints by a factor of four. The results of peel strength measurement at 90° are lower than those at 180°. Lap shear results are in line with peel strength.     

Dependence of Peel Adhesion on Molecular Weight of Epoxidized Natural Rubber

The effect of molecular weight of two grades of epoxidized natural rubber (ENR)—i.e., ENR 25 and ENR 50—on the peel strength of an adhesive is studied using coumarone-indene resin, gum rosin, and petro resin as tackifiers. Toluene and polyethylene terephthalate (PET) film acted as the solvent and substrate, respectively. A SHEEN hand coater was used to coat the adhesive on the substrate to give coating thicknesses of 30, 60, 90, and 120 µm. The peel strength of adhesive was determined using a Lloyd Adhesion Tester operating at 30 cm/min. Results show that peel strength has a maximum value at a molecular weight of 6.8 × 10⁴ and 3.9 × 10⁴ for ENR 25 and ENR 50, respectively, an observation which is attributed to the combined effects of wettability and mechanical strength of the rubber at the respective optimum molecular weight of ENR. Peel strength increases with coating thickness for all the tackifiers investigated, with a gum rosin-based adhesive exhibiting the highest peel strength.     

Peel Strength of Aluminium-Aluminium Joints Bonded by Adhesive Based on Carboxylated Nitrile Rubber-Chlorobutyl Rubber Blend

The peel strength of aluminium-aluminium joints bonded by an adhesive based on carboxylated nitrile rubber and chlorobutyl rubber was found to depend on surface topography and use of a silane primer. Anodization causes a marginal increase in bond strength while the silane primer improves the adhesive joint strength remarkably.

The peel strength was also found to be dependent on test conditions (test rate and temperature). The threshold peel strength value obtained by measurements at low peel rate and high test temperature was found to depend on the type of failure during peeling (cohesive or interfacial) which, in turn, is controlled by the presence of silica filler in the adhesive. Two different threshold values of peel strength were obtained: 60 N/m for interfacial failure (in silica-filled adhesive), 140 N/m for cohesive failure (in unfilled adhesive).     

The Effect of Silica on the Peel Adhesion of Epoxidized Natural Rubber-Based Adhesive Containing Coumarone-Indene Resin

The peel strength of silica filled on two grades of epoxidized natural rubber (ENR), i.e., ENR 25 and ENR 50 adhesive were investigated using coumarone-indene as the tackifying resin. Toluene was used as the solvent throughout the study. Result shows that peel strength increases with increase in silica loading due to the concentration effect of the filler. Peel strength, however, shows maximum value at 40 phr silica for both ENR 25 and ENR 50 an observation that is attributed to the maximum wettability and compatibility of adhesive on the substrate.     

Studies on the Physicochemical Properties of Natural Rubber/Polyethylene Blends and the Impact of Radiation on Their Properties

NR and Polyethylene (PE) were blended at different compositions of PE, like 00, 35, 50, 65, 85 and 100% by extrusion method and then the blend films were made by hot press. The blends, NR and PE films were irradiated and their mechanical properties were investigated before and after leaching. Blend compositions were optimized and found that the 50–65% PE blends give the best quality. It is also found that 5–8 kGy radiation doses are optimal for improved properties of blends. Leaching enhances mechanical properties and lower radiation doses give more enhanced mechanical properties compared to unleached one.     

低温硫化NR/BR并用胶的硫化特性及其力学性能研究

采用异丙基黄原酸钠SIP、N-乙基-N-苯基二硫代氨基甲酸PX的复合促进剂体系(用量分别为1.5phhr和0.5phhr)可使天然橡胶/顺丁橡胶并用胶(并用比为70∶30)在90℃~95℃内快速硫化,硫化特性符合缓冲胶工艺的要求,但其性能与HG/T 4124-2009《预硫化缓冲胶》存在一定的差距。     

钴盐用量对橡胶与钢丝帘线粘合性能的影响

对硼酰化钴ＭＣ２３（钴质量分数为２３％）用量（０６～１６份）对橡胶与钢丝帘线粘合性能的影响进行研究。采用的基本配方为：ＮＲ１０００；炭黑Ｎ３２６６２０；芳烃油８０；氧化锌９０；硬脂酸０５；防老剂４０２０２０；不溶性硫黄ＩＳ７０２０６０；促进剂ＤＺ１０；粘合剂ＲＳ３５；粘合剂Ａ２３；沉淀法白炭黑５０。结果表明，随着钴盐用量的增大，在未老化、热空气老化及盐水老化条件下，胶料与钢丝的粘合强度有所提高；在湿热老化条件下，粘合强度由于热量和湿气的交互作用而发生较大幅度的下降，但钴盐用量在１０份时粘合强度的下降为最小。综合胶料初始和老化后的应力应变性能和粘合强度，以１０份钴盐用量为最佳。     

The Effect of Filler Loading and Epoxidation on Paper-Sludge-Filled Natural Rubber Composites

The effect of filler loading and epoxidation on curing characteristics, dynamic properties, tensile properties, morphology, and rubber-filler interactions of paper-sludge-filled natural rubber compounds have been studied. Two different types of natural rubber, SMR L and ENR 50, having 0% and 50% of epoxidation and conventional vulcanization were used. Paper sludge was used as a filler and the loading range was from 0 to 40 phr. Compounding was carried out using a laboratory-sized two-roll mill. The scorch time for both rubber compounds decreased with filler loading. The cure time was found to decrease with increasing filler content for SMR L vulcanizates, whereas for ENR 50, the cure time seemed to be independent of the filler loading. Dynamic properties, i.e., maximum elastic torque, viscous torque, and tan delta, increase with filler loading in both grades of natural rubber. Results also indicate that both rubbers show increment in tensile modulus but inverse trend for elongation at break and tensile strength. However, for a fixed filler loading, ENR 50 compounds consistently exhibit higher maximum torque, modulus at 100% elongation, and modulus at 300% elongation, but lower elongation at break than SMR L compounds. In the case of tensile strength, ENR 50 possesses higher tensile strength than SMR L at 10 to 20 phr, but the difference is quite small at 30 and 40 phr. These findings might be associated with better rubber-filler interaction between the polar hydroxyl group of cellulose fiber and the epoxy group of ENR 50.     

Effects of Rice Husk Filler on the Mechanical and Thermal Properties of Liquid Natural Rubber Compatibilized High-Density Polyethylene/Natural Rubber Blends

Natural rubber/high-density polyethylene (NR/HDPE) blend with rice husk (RH) filler and liquid natural rubber (LNR) as the compatibilizer was prepared using an internal mixer at 140°C and 50 rpm. The reinforcing effect and compatibilizing performance of the added reagents in the composites were evaluated from the mechanical and thermal properties, and blend homogeneity. The tensile and impact strength decreased with RH loadings in the matrix, while the tensile modulus and hardness showed an opposite trend. The weak filler–matrix interaction, resulting in poor filler dispersion and large agglomerated particle size, caused those properties to decrease. However, the mechanical properties of the composites improved with the addition of NR or LNR into the matrix. The dissolution effect caused interactions between the phases, leading to an improvement in the compatibility in the blend. Changes in morphology resulted in the shift of T _g of the amorphous part of NR to higher temperatures, as observed in differential mechanical analysis (DMA) thermograms. Scanning electron microscopy (SEM) micrographs of the fractured surface had also revealed the good RH–matrix interaction and, thus, the dispersion of particles in samples with added LNR.     

硼酰化钴对橡胶与镀黄铜钢丝粘合性能的促进作用

研究了硼酰化钴对橡胶与镀黄铜钢丝粘合性能的促进作用。试验结果表明,加入硼酰化钴ＲＣＢ１６和ＲＣＢ２３ 能大大提高橡胶与镀黄铜钢丝的粘合性能,在耐盐水老化和湿热老化等方面的效果尤为显著,并分别与Ｍａｎｏｂｏｎｄ Ｃ１６ 和Ｍａｎｏｂｏｎｄ ６８０Ｃ 水平相当。     

温度对橡胶中液体透过性测量的影响

通过理论分析和典型试验，证明了温度对液体在橡胶中透过性测量的显著影响和保持试验环境温度恒定的必要性。     

纳米氧化物作为成核剂对PET结晶速率的影响

研究了成核剂纳米氧化镁和纳米氧化硅对聚对苯二甲酸乙二醇酯(PET)结晶速率的影响。通过等温结晶差热分析(DSC)研究了纳米氧化镁在不同含量、不同温度下对PET等温结晶行为的影响。用纳米氧化镁和纳米氧化硅填充PET体系的非等温结晶DSC,由所得冷结晶峰温度值和热结晶峰温度值的对比,探索纳米成核剂对PET结晶速率的影响及其规律。研究结果表明:纳米成核剂均能明显提高PET的结晶速率,而纳米氧化镁比纳米氧化硅对促进PET的结晶效果更好;添加不同含量的纳米氧化镁对PET在不同温度下的等温结晶影响不同,在所研究的范围内,1.0%的添加量较有利于PET的结晶。     

室温硫化水性硅橡胶粘接性研究

为了使水性硅橡胶具有实用价值,本文采用定性测试的方法,较系统地对有机锡催化体系室温硫化(RTV)水性硅橡胶粘接性进行了研究。结果表明,水性硅橡胶的粘接性随体系pH值的升高而提高;在一定范围内,水性硅橡胶的粘接性随催化剂用量或交联剂用量的减少而得到改善;加入适当的增黏剂、羟基稳定剂、或使用潜伏性活性基团的底涂剂都有助于改善水性硅橡胶的粘接性。     

温度对乳聚丁腈橡胶聚合的影响

采用中国石油兰州石化公司生产的丁腈橡胶N41乳液聚合配方,考察了不同聚合温度对反应时间的影响,测定了橡胶链化学结构组成、胶乳粒径、乳液机械稳定性和生胶门尼黏度等性能。结果表明:随着聚合温度的升高,反应时间缩短,丁腈橡胶链结构组成变化不明显。反应后期聚合温度的升高,导致胶乳粒径增大,机械稳定性降低,生胶门尼黏度升高。     

底涂液对恒压燃速测试用发射药与硅橡胶包覆剂粘接性能的影响

选用的3种底涂液可使硅橡胶包覆剂与发射药牢固地粘接在一起,其粘接剪切强度均大于2．0MPa,并且底涂液可保持较长露置时间而不降低其粘接特性。粘接包覆的发射药恒压燃速测试表明：硅橡胶包覆剂与发射药粘结强度满足高温、高压燃烧情况下对燃速测试的要求。     

The Effect of Carbon Black/Multiwall Carbon Nanotube Hybrid Fillers on the Properties of Natural Rubber Nanocomposites

The properties of hybrid multiwall carbon nanotube (MWCNT) and carbon black (CB) in natural rubber nanocomposites were studied. The results show that the scorch and cure time decreased as the MWCNT loading increased in CB/MWCNT hybrid loading ratio but for the maximum torque, the result shown otherwise. As the MWCNT loading increased in CB/MWCNT hybrid loading ratio, the tensile strength, elongation at break and fatigue life are decrease, however the tensile modulus and rubber filler-interaction (Q_f/Q_g) value increased. The SEM results show a dispersion of CB and MWCNT in natural rubber matrix. Furthermore, the thermal stability for the hybrid nanocomposites is enhanced.     

The Effect of Epoxidized Natural Rubber (ENR-50) or Polyethylene Acrylic Acid (PEA) as Compatibilizer on Properties of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L) Blends

The effect of epoxidized natural rubber (ENR) or polyethylene acrylic acid (PEA) as a compatibilizer on properties of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends was studied. 5 wt.% of compatibilizer was employed in EVA/SMR L blend and the effect of compatibilizer on tensile properties, thermal properties, swelling resistance, and morphological properties were investigated. Blends were prepared by using a laboratory scale of internal mixer at 120°C with 50 rpm of rotor speed. Tensile properties, thermal properties, thermo-oxidative aging resistance, and oil swell resistance were determined according to related ASTM standards. The compatibility of EVA/SMR L blends with 5 wt.% of compatibilizer addition or without compatibilizing agent was compared. The EVA/SMR L blend with compatibilizer shows substantially improvement in tensile properties compared to the EVA/SMR L blend without compatibilizer. Compatibilization had reduced interfacial tension and domain size of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends.     

温拌胶粉改性沥青低温性能及其与集料黏附性分析

通过弯曲梁流变(BBR)试验、接触角测量及原子力显微镜(AFM)测试等方法,从宏观和微观角度对老化前后温拌胶粉改性沥青(WCR)低温抗裂性及其与集料黏附性的变化规律进行研究,并以热拌胶粉改性沥青(HCR)作为对比。结果表明:随着老化程度的加深,HCR、WCR的蠕变速率(m)和弯曲蠕变劲度(S)的比值(m/S)减小,低温抗裂性能变差,WCR的低温抗裂、抗老化性能均优于HCR;老化前后HCR、WCR与三种集料的黏附性能大小依次为石灰岩＞玄武岩＞花岗岩,WCR与集料的黏附性均优于HCR;老化前后两种沥青的微观Derjaguin-Muller-Toporov(DMT)模量与低温流变参数(m/S)呈良好线性关系,且基于Johnson-Kendall-Roberts(JKR)力学模型得到的微观表面能、黏附功分别与基于表面能理论得到的宏观表面能、黏附功呈较强相关性。