Influence of rheological properties of adhesive polymer on strain energy release rate of mode II and adhesive shear strength

It is well known that adhesive strength shows temperature and rate dependencies reflecting viscoelastic properties of an adhesive used. Specifically, a mechanical relaxation mechanism around the glass transition temperature (T_g) has a strong effect on the adhesive strength, which involves deformation of the adhesive layer. In addition, it is very interesting to know how viscoelastic properties of the adhesive affect the value of strain energy release rate since deformation and failure of the adhesive occur at the measurement of strain energy release rate for adhesive joints. In this study, adhesive tensile strength and strain energy release rate (G_IIC) in plain-shearing mode were measured under a constant experimental condition using adhesives consisting of two types of epoxy resins; the influence of viscoelastic properties on these two values was investigated, and we discuss the relationship between the adhesive shear strength and G_IIC. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 525–536, 1997     

快干型玉米面粉粘合剂

主要介绍冷制快干型玉米面粉粘合剂的配方、制备工艺。此工艺无需烘干设备、产品的自然干燥速度比淀粉粘合剂提高一倍以上,而且其初粘力和稳定性均优于玉米淀粉粘台剂,成本却下降了20％以上,故有利于在纸箱、纸袋、纸筒、商标等行业中广泛使用。     

Effect of high loading rate and low temperature on mode I fracture toughness of ductile polyurethane adhesive

The mode I fracture toughness of an adhesive at low temperatures under high loading rates are studied experimentally. Typical R-curves of the polyurethane adhesive under different loading rates (0.5?mm/min, 50?mm/min, 500?mm/min) at different temperatures (room temperature, ?20?°C, ?40?°C) respectively are obtained. From the experimental results, the mode I fracture toughness of this adhesive is extremely sensitive to the high loading rates and low temperatures. With the increase of the loading rate and decrease of temperature, the mode I fracture toughness of this adhesive decreases significantly. Under the loading rate of 500?mm/min at ?40?°C, the mode I fracture toughness of adhesive is 15% of the value at room temperature (RT) under quasi-static conditions. Through the experiment, the relationship between mode I fracture toughness of this adhesive, nominal strain rate and temperature is obtained.     

Evaluation of the Constrained Blister Test for Measuring Adhesion

The constrained blister test (CBT) was evaluated as a method for measuring adhesion using a model system, electrical tape bonded to polystyrene. Pressure is applied through a circular inlet hole in the substrate, causing the adhesive to “blister” up and peel radially away from the substrate. A glass constraint, placed some distance above the adhesive, limits deformation of the adhesive in the vertical direction and promotes radial peel. By operating at low spacer height (the distance of the constraint above the adhesive) and very low growth rates, the energy spent for deformation of the adhesive and viscoelastic dissipation is minimized. Blister radial growth was linear with time, and growth rate increased linearly with the second power of the energy input. An intrinsic, rate-independent adhesion energy was obtained by extrapolation to zero crack growth rate. The CBT was compared with two peel tests. The dependence of the growth rate on energy input was different, but the extrapolation to zero growth rate gave the same value of the intrinsic adhesion energy.     

Investigation of a Critical Irradiance Criterion for Minimizing the Cure Time of a PAW Joint

Photo-activated Adhesive Workholding (PAW) technology is used to hold workpieces for manufacturing processes. This paper proposes a critical irradiance criterion that can be used to determine whether a curing light system is capable of curing a PAW adhesive joint at its maximum rate. It describes a series of experiments that were conducted to investigate the plausibility of this criterion for adhesive joints comprised of a commercially available adhesive mixed with various concentrations of carbon black and at varying thicknesses. Lastly, it provides experimental evidence that indicates that the addition of small concentrations of carbon black to a modified acrylic adhesive does not change its asymptotic, maximum strength. Furthermore, adhesive joints that are exposed to radiation that satisfies the critical irradiance criterion cure at a maximum rate.     

Viscoelastic analysis on peel adhesion of adhesive tape by matrix method

Analysis by means of matrix method is presented on the phenomenon of peel adhesion for 90° peeling of adhesive tape. A model of framed structure was assumed to duplicate the viscoelastic behavior of the tape: The adhesive layer is composed of a network structure made by elastic members for lattice elements and viscous members for diagonal elements. Calculated force distribution near the bond boundary showed good agreement with the experimental results of Kaelble. It was also found that the curve of peel rate versus peel force for the cohesive failure occurred in the adhesive layer was S-shaped; the change of peel force was affected severely by particular range of peel rate. For the interfacial failure at the bound boundary, on the other hand, the peel force possessed a maximum value for medium peel rate. Predicted failure mode for the adhesive tape changed from cohesive failure to interfacial failure with increasing rate of separation. Analytical results for the dependences of thickness of flexible members and adhesive layers on peel forces showed qualitative correlation with the experimental results.     

Prediction of Failure Times for Some Adhesive Bonded Joints

Data are given for shear and tensile testing of adhesive bonds under conditions of a constant rate of loading. A rate equation is then used to predict lifetime from the mechanical data. The correlations appear to be satisfactory providing that the failure is cohesive within the adhesive.     

Fracture toughness of adhesive joints. III. Temperature and rate dependencies of mode II fracture toughness and adhesive shear strength

Adhesive strength shows temperature and rate dependencies that reflect viscoelastic properties of an adhesive. Similarly, a critical strain energy release rate is expected to show temperature and rate dependencies because deformation and fracture of the adhesive occur at the time of the measurement of the strain energy release rate, which is a kind of fracture mechanical parameter for adhesive joints. In this study, the critical strain energy release rate (G_IIC) of a plane-shear mode was measured over a wide range of temperatures and rates, and then a master curve was obtained by applying the temperature-rate superposition principle to the obtained data. The relation between G_IIC and adhesive shear strength was also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 835–841, 1997.     

Analytical modelling of the automated dispensing of adhesive materials

The integrity of joints is a critical issue in structural bonding and the shape of adhesive beads needs to be consistent. The right amount of adhesive must be dispensed and to ensure this, the dispensing process must be automated. To have a fully automated dispensing cell, the use of a knowledge-based expert system for set-up and diagnosis is appropriate. To achieve this, the modelling of dispensing flow of adhesive material is essential to ensure that the correct sized bead is dispensed at a variety of robot speeds. For a given adhesive, it is often necessary to perform many ad hoc adjustments and tests to produce optimal adhesive beads at different operational and environmental conditions. To avoid this, the rheological behaviour of the adhesives is analysed, to find a constitutive equation for representing an adhesive model which best describes the way that different types of adhesives flow under a variety of conditions. Modelling the material properties provides an initial approximation of the flow rate for dispensing the adhesive. The automated dispensing cell can then adapt to the operational conditions where the model also provides for its initial set-up and diagnosis. This modelling method can also be applied to similar adhesives with known rheological data and nozzle flow rate.     

Determination of Traction Separation Law for Interfacial Failure in Adhesive Joints at Different Loading Rates

Cohesive zone modeling (CZM) has been extensively used in recent years to simulate failure in adhesive joints. Accurate determination of the traction–separation law (TSL) (or parameters of the CZM) is very crucial to the success of this approach. Recent experimental investigations have indicated that loading rate influences the TSL/CZM parameters. In this work we have attempted to measure the TSL using two different approaches for an adherend/adhesive system which always fails by interfacial failure. In the first approach, the TSL is obtained by differentiating the experimentally measured J integral by the opening displacement. The second, an inverse approach, involves a finite element (FE) analysis in which the adhesive layer is also modeled and cohesive elements are used to model the interfacial failure. The TSL is then obtained iteratively by matching the numerical load–displacement data to that obtained in experiments. We show that the first approach yielded TSLs which are dependent on both adhesive layer thickness and the loading rate, whereas the second approach yielded a TSL which is independent of the adhesive layer thickness and the loading rate. Therefore, the TSL obtained from the second approach is intrinsic to the adhesive/adherend pair and in that sense is unique.     

Fracture toughness of adhesive joints. II. Temperature and rate dependencies of mode I fracture toughness and adhesive tensile strength

It has been known that adhesive strength shows temperature and rate dependencies reflecting visoelastic properties of an adhesive. Similarly, a critical strain energy release rate is expected to show temperature and time dependencies deformation and fracture of the adhesive occurs at the time of measurement of the critical strain energy release rate, which is a kind of fracture mechanical parameter for adhesive joints. The term “critical strain energy release rate” has usually been called “fracture toughness.” In this study, the critical strain energy release rate (G_IC) of the opening mode was called mode I fracture toughness. G_IC was measured over a wide range of temperatures and rates, and then a master curve was obtained by applying the temperature–rate superposition principle to the obtained data. Also, on the relation between G_IC and adhesive tensile strength is discussed. © 1995 John Wiley & Sons, Inc.     

高性能乳液型丙烯酸酯压敏胶合成工艺研究

研究了高性能乳液型丙烯酸酯压敏胶的合成工艺，讨论了乳化剂、引发剂、单体配比以及反应温度、搅拌速率等对压敏胶性能的影响，确定了乳液型压敏胶的最佳合成工艺条件。     

Shear testing of thick adhesive layers using the ENF-specimen

An existing experimental method to determine cohesive laws for adhesive layers loaded in shear is further developed. The method is based on differentiation of the energy release rate (ERR) with respect to the adhesive shear deformation at the crack tip. The test geometry used is an ENF-specimen for which the adherends are assumed to deform linearly elastic. The original method is expanded to account for situations where the thickness of the adhesive layer is not negligible as compared to the adherend thickness. To this end, a novel mathematical expression for the energy release rate (ERR) is derived. No assumptions on the form of the cohesive law are made; it is implicitly included in the derivation. The expression for the ERR contains the applied load and the shear deformation of the adhesive layer at the initial position of the crack tip, in addition to geometrical properties and the elastic modulus of the adherend material. Numerical simulations are performed to verify the accuracy of the mathematical expression for the ERR. Preliminary results from experiments performed on an epoxy adhesive are presented. The cohesive law of the adhesive layer is extracted by using a blunted crack tip. Verifying simulations confirm that the local pre-fracture behavior is accurately captured.     

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).     

基于十字交叉法的陶瓷胶粘剂剪切蠕变性能研究

本研究设计了“十字交叉法”陶瓷胶粘剂剪切蠕变试验装置,选取刚性环氧树脂及柔性硅酮结构胶进行剪切蠕变试验,研究了环境温度、剪切应力、粘结面积等因素对胶粘剂剪切蠕变的影响,通过模型拟合对胶粘剂的剪切蠕变行为进行了分析和预测,探究了两种胶粘剂的蠕变破坏模式。结果表明:采用十字交叉法能够准确便捷地测试陶瓷胶粘剂的蠕变性能。增大胶粘层柔性、提高环境温度、增大剪切应力都会加速蠕变的发展,但粘结面积对蠕变速率无明显影响。刚性环氧树脂胶粘剂试样的蠕变失效形式为粘结层内聚破坏及界面脱粘,符合时间硬化模型;柔性硅酮结构胶试样失效形式为粘结层内聚破坏,符合Burgers模型。     

Assessments for impact of adhesive properties: modeling strength of metallic single lap joints

Adhesively bonded joints are widely used in a variety of industrial and engineering activities. Their overall strength is dependent on the properties of the adhesives. In the present research, assessments of adhesive properties were performed systematically through defining both strength mixity and energy rate mixity and using them to characterize the overall strength of metallic single lap joints. By means of the cohesive zone model, the adhesive strength mixity was defined as the ratio of the shear and tensile separation strength, and the energy rate mixity was defined as the ratio of the area below the shear cohesive curve and the area below the tensile cohesive curve. For each specified group of mixity parameters, corresponding to the properties of a specified adhesive, the overall strengths and the critical displacements of bonded joints were characterized. A series of strength and energy rate mixities were taken into account in the present calculations. A comparison of the present calculations with some existing experiments was carried out for both brittle and ductile adhesives. Finally, in the calculations presented here, damage initiation and evolution of the adhesive layer were also undertaken. The results showed that the overall strength of the joints was significantly depended on the adhesive properties, which were characterized by the strength and energy rate mixities of the adhesive. Furthermore, the shear adhesive stress components played a dominate role in both the damage initiation and evolution in the adhesives, which were also affected by the overlap length of the joints.     

Visco-elasto-plastic constitutive model of adhesives under uniaxial compression in a range of strain rates

Determining the constitutive model of adhesives enables the prediction of the mechanical response of hybrid structures in which the adhesive is used. In this study, the stress–strain behavior of a two-component structural adhesive was first measured in uniaxial compression experiments at the strain rates ranging from 0.001 to 2600 s⁻¹ for developing a constitutive model. It was found that the compressive response, including elastic modulus, yield strength, and plastic flow stress, is substantially influenced by the strain rate. In plastic deformation, the strain rate sensitivity is not constant but varies with the rate; moreover, strain softening and hardening dominate the plastic deformation at low and high strains, respectively. A visco-elasto-plastic constitutive model was then proposed for the adhesive, integrating the strain rate sensitivity that was quantified by empirical equations. The model which was validated can reliably represent the strain rate dependent compressive behavior of the adhesive. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48962.     

Time Dependent Crack Growth and Loading Rate Effects on Interfacial and Cohesive Fracture of Adhesive Joints

Double cantilever beam fracture specimens were used to investigate rate dependent failures of model epoxy/steel adhesively bonded systems. Quasi-static tests exhibited time dependent crack growth and the maximum fracture energies consistently decreased with debond length for constant crosshead rate loading. It was also possible to cause debonding to switch between interfacial and cohesive failure modes by simply altering the loading rate. These rate dependent observations were characterized using the concepts of fracture mechanics. The time rate of change of the strain energy release rate, dG/dt, is introduced to model and predict failure properties of different adhesive systems over a range of testing rates. An emphasis is placed on the interfacial failure process and how rate dependent interfacial properties can lead to cohesive failures in the same adhesive system. Specific applications of the resulting model are presented and found to be in good agreement when compared with the experimental data. Finally, a failure envelope is identified which may be useful in predicting whether failures will be interfacial or cohesive depending on the rate of testing for the model adhesive systems.     

FHX-2高速卷烟胶粘剂的制备

通过醋酸乙烯与丙烯酸酯类的共聚制备卷烟接嘴用FHX -2高速卷烟胶粘剂 ,该胶具有初粘力大、干燥速度快、粘接强度高、胶质细腻流动性好 ,废品率低 ,不含有害添加剂 ,可以满足接嘴车速 70 0 0～ 80 0 0支 分钟的要求     

LLDPE拉伸缠绕膜的自粘性研究

研究了线型低密度聚乙烯(LLDPE)拉伸缠绕膜的粘性松驰,讨论了粘性母料加入量、制膜冷却速率、粘性添加剂分子量、贮存温度及不同的制膜工艺方法对缠绕膜自粘性的影响。