The Effect of Modification of an Epoxy Resin Adhesive with ATBN on Peel Strength

The effects of rubber content, rate of peel and temperature on peel strength of ATBN modified DGEBA based epoxy resin adhesives have been investigated. The fracture surfaces of peel test specimens and the distribution of rubber particles in cured bulk epoxy resin have been observed with SEM and TEM, respectively. The mechanical properties of bulk rubber modified epoxy resin have been also measured. The peel strengths increased with increasing rubber content, peel rate, and decreasing temperature. The peel strengths were superposed as a function of rate and temperature. Plots of the shift factors against temperature gave two straight lines, which followed an Arrhenius relationship. The region of temperature below the intersection of the two straight lines, temperature somewhat lower than T_g of epoxy adhesive, gave markedly high peel strengths and a stick-slip failure due to plastic deformation of the adhesive, and a number of micro holes produced by the rupture of rubber micro particles on the fracture surface. The region of temperature above the intersection gave lower peel strengths and an apparent interfacial failure with ductile fracture of the adhesive, and larger, shallow holes or no holes. From these results, the marked increase of peel strength was concluded to be mainly attributed to the plastic or viscoelastic deformation of epoxy matrix, the strong bond at the interface between rubber particles and epoxy matrix, and the dilation and rupture of a number of rubber particles.     

Peel stress relaxation of aluminium-aluminium joints bonded by chlorobutyl rubber-carboxylated nitrile rubber blend

The authors have introduced the concept of peel stress relaxation during 180° peel testing of an aluminium-adhesive-aluminium joint in order to explore the correlation, if any, between relaxation phenomenon and performance of the adhesive joint. The adhesive is based on a self-vulcanizable rubber blend of chlorobutyl rubber and carboxylated nitrile rubber. Peel stress relaxation depends on moulding time, silica filler loading, test temperature and peel rate. Peel stress relaxation mechanism varies depending on whether the adhesive joint failure is cohesive or interfacial.     

Effect of silica filler on aluminum-aluminum bonding by a self-vulcanizable blend based on chlorobutyl rubber and carboxylated nitrile rubber

Silica filler improves the aluminum-aluminum bonding by a self-vulcanizable rubber blend based on chlorobutyl rubber and carboxylated nitrile rubber. The joint peel strength depends on the filler loading, the state of cure, the molding temperature, and the adhesive film thickness. The higher peel strength in the filled adhesive system is due to filler reinforcement resulting in tear path deviation and the formation of Si—O—Al linkage at the aluminum-adhesive interface. Maximum peel strength was obtained at 10 phr filler loading, when the molding temperature was 180°C and the molding pressure was 0.35 MPa.     

Reactive bonding of natural rubber to metal by a nitrile–phenolic adhesive

The mechanism of adhesive bonding of rubber to metal using an interlayer of bonding agent (adhesive) is discussed with respect to various physical and chemical events such as adsorption at the metal surface, chemical crosslinking within the adhesive, interdiffusion, and formation of interpenetrating networks at the rubber–adhesive interface. An investigation on the peel strength of a natural rubber (NR)–adhesive–metal joint, made by vulcanization bonding using nitrile–phenolic adhesive containing various concentrations of toluene diisocyanate–nitrosophenol (TDI–NOP) adduct, is presented. A single‐coat adhesive, consisting of a p‐cresol phenol formaldehyde resin, nitrile rubber (NBR), and vulcanizing agents in methyl ethyl ketone solvent, was selected for the study. Considerable improvement in the peel strength was obtained by the incorporation of TDI–NOP adduct into the nitrile–phenolic adhesive. The peel strength increases as the concentration of TDI–NOP adduct in the adhesive composition increases, then levels off with a transition from interfacial failure to cohesive tearing of rubber. The peel strength improvement is believed to be attributed to the interfacial reactions between the bonding agent and natural rubber, when TDI–NOP adduct is incorporated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2597–2608, 2001     

Bonding of Natural Rubber to Steel: Surface Roughness and Interlayer Structure

This paper is concerned with two aspects of the adhesion produced by the vulcanisation bonding of a simple natural rubber (N.R.) compound to mild steel. Adhesion was measured using a 45° peel test.

When the N.R. was bonded, using a proprietary bonding agent (Chemlok 205/220), to 'smooth' steel (acid etched) or to 'rough' steel (phosphated) high values of peel energy (≥ 4.5 kJm^-2), and good environmental resistance to water were obtained, with failure cohesive largely within the rubber. The highest values of peel energy (≈ 7.5 kJm^-2) were associated with a phosphated surface which consisted of plate-like crystals which directed the stresses away from the substrate in a way which produced a failure surface within the rubber which showed extensive tearing and cracking.

The nature of the layer formed in the interfacial region by interaction between bonding system and rubber was investigated using a chlorinated rubber as a 'model compound' representing the adhesive and uncompounded N.R. to represent the rubber. When a blend of the two was heated in air at 150°C, evidence was found of a solid state chemical reaction in which carbonyl groups were incorporated into the blend which became visually homogeneous. Further evidence points to the relevance of this change to adhesion in rubber-to-metal bonding.     

端氨基丁腈橡胶增韧环氧-聚酰胺胶粘剂的研究

通过DSC,扫描电镜分析及剪切和剥离强度性能测试研究了端氨基液体丁腈橡胶(ATBN)改性环氧-聚酰胺体系的固化动力学,粘接性能及增韧相态。结果表明,根据Ellerstein法和峰值法计算得到的固化反应活化能分别为为73.6 kJ/mol和65.7 kJ/mol,体系最佳固化温度为41～97℃。固化体系中橡胶相粒径大小对胶粘剂性能有较大影响,60℃和室温固化体系分散相粒子平均粒径分别为1～2μm,0.5μm。粒径1～2μm时体系的增韧效果最佳,粘接性能优异。     

Adhesion and Failure Mechanisms of a Model Hot Melt Adhesive Bonded to Polypropylene

A model hot melt adhesive (HMA) based on an ethylene/vinyl acetate copolymer (EVA), an Escorez® hydrocarbon tackifier, and a wax has been used to bond together polypropylene (PP) films to give equilibrium bonding. Peel strengths were determined over a broad range of peel rates and test temperatures. Contrary to the peel behavior of joints with simple rubbery adhesives [1], peel strengths with this semi-crystalline adhesive are not rate-temperature superposable, and multiple transitions in failure locus occur. The semi-crystalline structure of the HMA also prevents rate-temperature superposition of its dynamic moduli.

At different test temperatures, the dependence of peel strength on peel rate shows some resemblance to the dependence of the loss tangent of the bulk adhesive on frequency. This is consistent with a previous result [2] that the HMA debonding term. D, varies with the loss tangent of a HMA at the T-peel debonding frequency.

This model HMA, similar to block copolymer/tackifier blends [3], consists of two phases: an EVA-rich and a tackifier-rich phase, in its amorphous region. At a low peel rate of 8.33 × 10^-5 m/s, the peel strength shows a maximum at a temperature that corresponds to the transition temperature of the tackifier-rich phase (T₁). At a higher peel rate of 8.33 × 10^-3 m/s, the peel strength rises with increasing test temperature, but becomes essentially constant at temperature T₁'. It is believed that, to optimize the peel strength of a HMA at ambient temperature, it is advantageous to formulate the EVA polymer (or other semi-crystalline polyolefins) with a compatible tackifier that yields a tackifier-rich phase with a transition temperature (T₁') in the vicinity of room temperature.     

Peel and shear strength of pressure‐sensitive adhesives prepared from epoxidized natural rubber

Peel and shear strength of two grades of epoxidized natural rubber (ENR 25 and ENR 50)‐based pressure‐sensitive adhesive was studied. Coumarone‐indene resin was used as the tackifier, whereas toluene was chosen as the solvent throughout the experiment. The tackifier loading was varied from 0 to 80 parts per hundred parts of rubber (phr). A SHEEN hand coater was used to coat the adhesive on substrate to give a coating thickness of 30, 60, 90, and 120 μm. Peel strength and shear strength of the adhesive were determined by using a Lloyd adhesion tester and Texture analyzer, respectively. Results show that maximum peel strength occurs at 40 phr of coumarone‐indene resin for both ENRs studied an observation, which is attributed to the maximum wettability of the substrate. However, the shear strength shows a gradual decrease with increasing tackifier loading because of the decrease in cohesive strength of adhesive. ENR 25 consistently indicates higher peel strength and shear strength than ENR 50. Generally, peel and shear strength increases with coating thickness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.     

金属橡胶热硫化型底胶的研制

研制了一种酚醛一橡胶型底胶,探讨了主要组分对底胶性能的影响。实验结果表明,以n甲醛：n苯酚：n氮氧化钾=2．25：1：0．1,在65℃／3h合成的甲阶酚醛树脂具有高羟基含量,能满足底胶主体树脂要求;当该酚醛树脂100质量份、氯化橡胶60~80份、硅烷偶联剂10-15份、钛白粉30~35份时底胶具有较高强度,扯离强度40MPa以上,剥离强度3．0kN／m以上,且试件破坏形式主要为橡胶内聚破坏。该底胶作为单涂层胶粘剂可实现极性橡胶与金属的热硫化粘接,与相适应的面胶配合构成的双涂层胶接体系还可实现非极性橡胶与金属或复合材料的热硫化粘接,目前已在金属橡胶粘接领域获得了应用。     

Bonding of Natural Rubber to Steel: Surface Roughness and Interlayer Structure

This paper is concerned with two aspects of the adhesion produced by the vulcanisation bonding of a simple natural rubber (N.R.) compound to mild steel. Adhesion was measured using a 45° peel test.

When the N.R. was bonded, using a proprietary bonding agent (Chemlok 205/220), to ‘smooth’ steel (acid etched) or to ‘rough’ steel (phosphated) high values of peel energy (≥ 4.5 kJm^?2), and good environmental resistance to water were obtained, with failure cohesive largely within the rubber. The highest values of peel energy (≈ 7.5 kJm^?2) were associated with a phosphated surface which consisted of plate-like crystals which directed the stresses away from the substrate in a way which produced a failure surface within the rubber which showed extensive tearing and cracking.

The nature of the layer formed in the interfacial region by interaction between bonding system and rubber was investigated using a chlorinated rubber as a ‘model compound’ representing the adhesive and uncompounded N.R. to represent the rubber. When a blend of the two was heated in air at 150°C, evidence was found of a solid state chemical reaction in which carbonyl groups were incorporated into the blend which became visually homogeneous. Further evidence points to the relevance of this change to adhesion in rubber-to-metal bonding.     

高耐温性钢塑管材用热熔胶黏剂的制备及性能研究

以神华均聚聚丙烯（PP）为基体树脂,通过与聚烯烃弹性体（POE）共混反应挤出制备了高耐温性钢塑管材用热熔胶黏剂。研究了引发剂含量、接枝单体含量和PP/POE配比对热熔胶性能的影响,考察了自制热熔胶在实际应用中的耐温性能。结果表明,反应挤出制备的聚丙烯接枝马来酸酐(PP?g?MAH)基热熔胶综合性能优异,其剥离强度和100 %拉伸弹性回复率分别可达131.4 N/25 mm和65.5 %;高低温循环（-40~130 ℃）800次后自制热熔胶的剥离强度依然可以维持在122.2 N/25 mm,剥离失效率只有7.0 %,其耐温性明显优于选取的两个商业化牌号热熔胶。     

Study of rubber‐filled cementitious composites

A possible method for recycling automobile and truck tires is to comminute them and incorporate the rubber particles in to cementitious mixtures for nonstructural applications. It was found that addition of rubber granules led to a decrease in compressive and flexural strengths of the mortar. The fracture behavior of cementitious paste containing untreated rubber particles showed particulate pull out characteristics and weak interface. The interfacial strength of rubber‐cementitious composite can be improved upon chemical treatment of rubber by gamma mercapto trimethoxy silane coupling agent (GMPTS). The extent of interfacial bonding of rubber and cement was measured by peel strength analysis. The increased interfacial strength of the composite was found to play an important role in the ability of the composite to withstand postpeak loading and postpeak displacement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 934–942, 2000     

Scanning Electron Microscopic Studies on the Failure of Rubber-to-Metal Bonded Composites

Scanning electron microscopic studies were conducted to evaluate the failure mechanism of rubber-to-metal bonded composites in the 90° peel test (ASTM D 429-B). It was found that when cohesive failure in rubber takes place, the composites, failing by stick-slip mode, show high peel strength. Moreover, in such cases, there exists a linear correlation between the peel strength and the crosslink density of the rubber vulcanizate.     

航空器用单组分RTV硅橡胶胶粘剂性能研究

研究了单组分室温硫化(RTV)硅橡胶胶粘剂ND-704及GD-913的室温粘合性能、耐油性能及高低温循环性能。结果表明,经过耐油试验及高低温循环试验后,2种胶粘剂室温粘合性能均下降;胶粘剂耐润滑油性能最好、液压油次之、燃油最差,其中ND-704不耐燃油。试样破坏形式为由内聚破坏转变为粘附破坏;经过高低温循环试验后,2种胶的剥离强度均有所降低,破坏形式为混合破坏。在各种状态下,GD-913胶粘剂试样剥离强度均高于ND-704,可用于航空领域。     

Effect of bonding temperature on the joint strength of polyolefln/butyl rubber and polyolefin/ethylene-vinylacetate copolymer

The effect of bonding temperature on the peel strength of adhesive joints, polyolefin/butyl rubber and polyolefin/ethylene-vinylacetate copolymer, has been investigated. The peel strength, measured at room temperature, undergoes a sharp transition from its low values to higher values as the bonding temperature is changed from below to above, the melting point of the substrate. This increase in peel strength is accompanied by changes in failure mode from the apparent interfacial failure to cohesive failure through the adhesives. Investigation of the interface using Fourier Transform Infrared Internal Reflection spectroscopy and interference microscopy indicates that the sharp increase in the peel strength at the melting temperature of substrate is associated with the presence of an interdiffused layer at the interface.     

Effect of Coumarone-Indene Resin on Adhesion Property of SMR 20-Based Pressure-Sensitive Adhesives

The viscosity, tack, and peel strength of a natural rubber (SMR 20)–based pressure-sensitive adhesive (PSA) was studied using coumarone-indene resin as the tackifier. The resin loading was varied from 0–80 parts per hundred parts of rubber (phr). Toluene was used as the solvent throughout the experiment. The viscosity of PSA was measured using a Haake Rotary Viscometer whereas loop tack and peel strength were determined using a Lloyd Adhesion Tester. PSA was coated onto the substrates using a SHEEN hand coater to give a coating thickness of 60 μm and 120 μm. Results show that the viscosity and tack of the adhesive increases with resin content due to the concentration effect of tackifier resin. However, for the peel strength, it increases up to 40 phr of resin for both coating thickness, an observation that is attributed to the wettability of substrates.     

Adhesion properties of pressure-sensitive adhesives prepared from SMR 10/ENR 25, SMR 10/ENR 50, and ENR 25/ENR 50 blends

The adhesion properties, i.e. viscosity, tack, and peel strength of pressure-sensitive adhesives prepared from natural rubber/epoxidized natural rubber blends were investigated using coumarone-indene resin and toluene as the tackifier and solvent respectively. One grade of natural rubber (SMR 10) and two grades of epoxidized natural rubbers (ENR 25 and ENR 50) were used to prepare the rubber blends with blend ratio ranging from 0 to 100%. Coumarone-indene resin content was fixed at 40 parts per hundred parts of rubber (phr) in the adhesive formulation. The viscosity of adhesive was measured by a HAAKE Rotary Viscometer whereas loop tack and peel strength was determined using a Lloyd Adhesion Tester operating at 30 cm/min. Results show that the viscosity of the adhesive passes through a minimum value at 20% blend ratio. For loop tack and peel strength, it indicates a maximum at 60% blend ratio for SMR 10/ENR 25 and SMR 10/ENR 50 systems. However, for ENR 25/ENR 50 blend, maximum value is observed at 80% blend ratio. SMR 10/ENR 25 blend consistently exhibits the best adhesion property in this study, an observation which is attributed to the optimum compatibility between rubbers and wettability of adhesive on the substrate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of zinc oxide on the viscosity,tack, and peel strength of ENR 25‐based pressure‐sensitive adhesives

Viscosity, loop tack, and peel strength of epoxidized natural rubber (ENR 25 grade)‐based pressure‐sensitive adhesive was studied in the presence of zinc oxide. The zinc oxide concentration was varied from 10–50 parts per hundred parts of rubber (phr). Coumarone–indene resin with loading from 20 to 100 phr was chosen as the tackifier resin. Toluene was used as the solvent throughout the experiment. The adhesive was coated on the substrate using a SHEEN hand coater to give a coating thickness of 60 μm. Viscosity of the adhesive was determined by a HAAKE Rotary Viscometer whereas the loop tack and peel strength were measured by a Llyod Adhesion Tester operating at 30 cm/min. Results show that viscosity and loop tack of adhesive increases with increasing zinc oxide concentration. For the peel strength, it increases with zinc oxide concentration up to 30–40 phr and drops after the maximum value. This observation is associated with the effect of varying degree of wettability of the adhesive on the substrate. However, for a fixed zinc oxide concentration, loop tack and peel strength exhibit maximum value at 80 phr resin loading after which both properties decrease with further addition of resin, an observation which is attributed to phase inversion. From this study, the optimum adhesion property is achieved by using 40 phr zinc oxide and 80 phr coumarone–indene resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and application of dual-curable PVB based adhesive formulations for cord/rubber applications

In this research, formaldehyde-free dual-curable adhesive formulations containing polyvinyl butyral (PVB) were prepared with the reaction of 2,4-toluene diisocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA) and then applied on cord fabrics upon adhere onto the rubber surfaces. The effects of PVB ratio on peel strength value between the cord and rubber were studied. The structure of the oligomer was characterized by FTIR and ¹H NMR spectroscopy. Thermal properties of coated and UV-cured fabrics were investigated by TGA and DSC. Surface wettability properties of the fabrics after coating were observed with contact angle measurement. The peel strength between cord/rubber surfaces was determined by T-peel test after thermal curing stage under heat and pressure. Results showed that peel strength value increases with increasing PVB amount in the formulation. The highest peel strength of 94.7 N/cm was observed when 5% PVB was included in the formulation. This study leads to a new type of promising adhesives with superior peel strength for cord/rubber applications as it is being a totally formaldehyde-free process.     

Strength degradation in γ-aminopropyl triethoxy silane primed α-Al2O3/nylon 6 peel joints in a wet environment

Unprimed sapphire/nylon 6 peel joints (2.13 ± 0.27 Kg/cm) are found to be stronger than sapphire/polyethylene joints (0.06 ± 0.02 Kg/cm). Priming the sapphire with γ-aminopropyl triethoxy silane (γ-APS) improves the strength significantly resulting in adherend failure in the nylon. The rate and extent of degradation is lower with priming. The optimal silane thickness is about 1900 Å, obtained with a 0.3 percent γ-APS solution, for a five day exposure to water at 25°C. Peel joints made with 0.3 percent γ-APS film, both dried at 25°C (standard conditions) and dehydrated at 110°C under vacuum, fail cohesively when exposed at 25°C. Increasing the exposure to 55°C in a second step results in strength degradation only with dehydrated films. Lower joint strengths are obtained with five days exposure as compared to one day exposure. However, if the temperature is raised to 65°C the joints primed with standard dried films now begin to degrade and lose 90 percent of their strength in five days. Further, the nylon 6 peel joints made with a 0.3 percent γ-APS film, dehydrated for three days prior to lamination, show 10 times greater wet strengths than the corresponding PE joints. Failure surface analyses by ESCA and SEM suggest that failure locus due to water degradation is within the γ-APS layer and the failure mode is cohesive. Failure mechanics during testing the wet peel joints may also cause a partial interfacial failure mode. The effects of the silane film thickness, dehydration condition, time, and temperature dependence of the peel strength degradation indicates that the structure of the γ-APS layer plays an important role in the promotion and retention of adhesion with a thermoplastic polymer system capable of limited primary interactions through possible interdiffusion with the silane layer.