Adhesion of continuously manufactured fusion bonded multi-material structures consisting of steel and carbon fibre reinforced Polyamide 6

In regard to e-mobility and the correlating additional battery storage weight as well as the demand for the reduction of exhaust emissions in the automotive industry the development of lightweight solutions is required. Load-adapted tailored hybrid structures manufactured within a continuous production process offer a high potential for the automotive industry. With focus on high production rates and a high degree of automation, roll forming of multi-material structures is a promising approach. In order to improve strength and stiffness in relation to density, roll formed parts consisting of steel sheets reinforced by carbon fibre reinforced thermoplastic tapes (CFR-TP) are investigated. The evaluation of the adhesion between both materials joined in a continuous manufacturing process still is an important challenge, because the adhesion between both adherends is mandatory to transfer loads between both materials, and thus considered within the present work.To minimize the amount of process steps for a large-scale production of hybrid structures, the steel sheets and the thermoplastic tape are joined by fusion bonding while the surface of the thermoplastic matrix is melted and thus joined to the steel surface. Therefore a defined heating of both materials is required and consequently the effects of various temperatures on the adhesion have to be considered. With focus on achieving sufficiently high joint strength of multi-materials structures, various pre-treatments of steel as well as of CFR-TP were investigated.Hence, the present work focuses on the one hand on the evaluation of the adhesion between steel and CFR-TP dependent on various steel as well as CFR-TP temperatures within continuous manufacturing processes. On the other hand, effects of different surface conditions of both materials, due to surface pre-treatments of steel and CFR-TP, on the adhesion are examined. The continuously manufactured specimens are destructively tested by roller peel testing. In addition, evaluation of fracture patterns was carried out for the destructively tested hybrid joints. The examinations show the improvement of adhesion with increasing steel as well as CFR-TP temperature. Furthermore, additional pre-treatment results in an improved adhesion.     

Study on benzoxazine-based film adhesive and its adhesion properties with CFPR composites

In this paper, a benzoxazine-based (BZ) adhesive with high temperature resistant was developed by blending benzoxazine monomer and tetrafonctional epoxy monomer as matrix modifier and polyetherimide as toughening agent. The results show that benzoxazine-based film adhesive could be cured at 190 °C, and the cured film adhesive exhibited high temperature resistance and a high glass transition temperature of 224 °C. The 5% weight loss temperature in air was 400 °C and the char yield in nitrogen at 800 °C was 48%. The cured film adhesive has good ablation resistance. The fabricated benzoxazine-based film adhesive has high adhesion reliability, with single-lap shear strength of 23.20, 28.36 and 20.04 MPa at room temperature, 140 and 175 °C respectively. The curing process of the film adhesive matches well with that of carbon fiber reinforced BZ prepreg and the film adhesive has stable adhesion properties. Its biggest advantage is that, during storage and transportation, there is no need of refrigeration. After 60 days of storage for benzoxazine-based film adhesive at room temperature, its process performance and adhesion properties remain unchanged. It is expected that the benzoxazine-based film adhesive can be used in aerospace, high-speed rail and other applications.     

聚醚型聚氨酯热熔胶膜的研制

以PTMG、BDO和MD I等为原料合成聚氨酯预聚物,分别考查了预聚反应的时间、温度等因素,确定了合适的反应条件为(80~90)℃/(2.5~3)h。采用流延法制备聚氨酯热熔胶膜,对影响聚氨酯热熔胶膜的拉伸强度、断裂伸长率、硬度的几个因素:聚醚多元醇类型、扩链剂用量和聚醚多元醇的分子质量等进行了研究。结果表明,选用相对分子质量为1 500的聚醚,BDO质量分数为6.1%~8.2%,制备的胶膜性能最佳。     

Process variable effect on the strength of autoclave-bonded film adhesive joints

This study investigates the effect of five independently-controlled process variables and variable combinations on the shear strength of autoclave-bonded film adhesive joints. Studied variables include the cure temperature, cure pressure and their respective ramp rates, as well as the duration of cure time. A full factorial design of experiment (DoE) at two levels for each variable is conducted with 3 replicas of each test. Test coupons are made of two layers of polycarbonate lexan that are autoclave-bonded using aliphatic polyether film adhesive (Huntsman PE399). Two set of test joints are used for generating test data on shear strength and failure mode. Bonded joints in the first set are tested prior to any environmental cycling, in order to generate baseline data on joint shear strength and failure mode. However, samples from the second set of autoclave-bonded joints were heat-cycled, in an environmental chamber at high relative humidity, prior to testing for shear strength. Test data on shear strength and failure mode is statistically analyzed using ANOVA.     

多层复合PVC胶粘膜的性能改进

针对普通PVC胶粘膜在使用过程中存在的问题,开发了无残胶、不脱漆、耐候性能和阻燃性能优良的多层复合PVC胶粘膜.     

汽车工业生产用热熔胶膜的研制

介绍了汽车工业生产内装饰复合材料用热熔胶膜的性能及其研制状况。这种热熔胶膜具有使用便捷,高效,生产、使用过程中没有污染的具有热熔胶膜的特长。     

光学透明胶膜CEF0807的性能研究

光学透明胶膜(CEF0807)是一种用于粘接光学透明元件的特种PSA(压敏胶),其对被粘基材的力学性能、透光性能、雾度、色彩失真度和可靠性等影响很大。研究结果表明:CEF0807是一种粘接性能优异的压敏胶,其对玻璃、聚碳酸酯(PC)、聚甲基丙烯酸甲酯(PMMA)和聚对苯二甲酸乙二醇酯(PET)等基材的180°剥离强度分别为141、117、108、103 N/100 mm;CEF0807具有优异的光学性能,其透光率为94.3%,而雾度和色差(ΔE)仅分别为0.80%和1.48;CEF0807经环境可靠性测试后性能优异,非常适合于光学元件、光学视窗等材料的粘接。     

Fabrication and evaluation of structural film adhesive using oxazolidinone modified novolac epoxy resin

Epoxy film adhesives are of prime importance for the fabrication of lightweight honeycomb structures for aerospace industries. This work involves the synthesis of oxazolidinone modified epoxy novolac resin (EPN-OXA) via the reaction of EPN and toluene diisocyanate. EPN-OXA was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and epoxy equivalent weight. EPN-OXA was blended with solid epoxy resin, polyethersulfone (PES) toughened liquid epoxy resin, dicyandiamide, and aluminum powder to fabricate a film adhesive curing at 170–180 °C. Effect of additives and curative on the adhesive property was studied to optimize the composition. Effect of PES on the optimized composition was studied in detail. The best composition exhibited lap shear strength of 370 ± 10 kgf cm⁻² at 25 °C and the strength was retained to 75% at −196 °C and 52% at 120 °C. PES significantly enhanced the interfacial strength at different temperatures (~1.6-fold at −196 and 25 °C and ~1.8-fold at 120 °C). It also improved tensile strength and fracture toughness by 1.4- and 2-fold, respectively. The toughening effect of PES was further confirmed by scanning electron microscopy images. PES marginally reduced the glass-transition temperature and it exhibited no effect on thermal stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47520.     

热熔型纸塑复合预涂膜的研制

以EVA弹性体为主体材料,配以适宜的增粘树脂及其他助剂,制成热熔胶粘剂并涂于BOPP或聚酯膜上,用于纸塑复合。讨论了各种基料对热熔胶软化点、熔融粘度的影响。该预涂膜性能优良,无毒无污染,复合工艺简单,可提高生产效率。     

Improvement in the adhesion of polyimide/epoxy joints using various curing agents

An improvement in the adhesion strength of polyimide/epoxy joints was obtained by (1) introducing a functional group on the polyimide surface, (2) improving the mechanical properties of the epoxy adhesive, (3) increasing the curing temperature, and (4) using polyamic acid as an adhesion‐promoting layer. The functional group on polyimide was introduced via treatment with aqueous KOH. An adhesion‐promoting layer was formed by spin coating polyamic acid onto a modified polyimide surface. The maximum adhesion strength of the polyimide/epoxy joint was obtained using polyamic acid as both the adhesion‐promoting layer and as the curing agent. The surface energy of the modified polyimide was examined using contact angle measurements and Fourier transform infrared spectroscopy, and the peel strength was determined by the T‐peel method. The peeled surfaces were analyzed using scanning electron microscopy and X‐ray photoelectron spectroscopy.© 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 812–820, 2002     

压敏保护膜及其在现代工业中的应用

对压敏保护膜的原理、构成、制造方法以及在现代工业中的应用进行了研究分析。     

干式复合包装膜复合强度的影响因素分析

简述了干式复合包装膜复合强度的主要影响因素,从粘接剂的选择与应用、复合基材的性能、复合工艺控制等作了具体的分析,并提出了解决办法。     

四元共聚丙烯酸酯热熔压敏胶膜的合成研究

以丙烯酸-2-乙基己酯(2-EHA)、甲基丙烯酸甲酯(MMA)、丙烯腈(AN)和丙烯酰胺(AM)为共聚单体,采用预乳化法制备聚丙烯酸酯热熔胶,研究了单体用量配比,乳化剂用量、配比及乳化方式,引发剂用量,温度和滴加速度对反应及性能的影响。结果表明：2-EHA/MMA 1/0．6,AN 5％,AM 5％,复合乳化剂3．0％,引发剂过硫酸钾0．3％,80～85℃,反应4h,丙烯酸酯橡胶分子量在10万以上时,制得的热熔压敏胶膜综合性能良好。     

Functionally graded adhesive joints by graded mixing of nanoparticles

The main objective of the present study was to use a functionally modified adhesive in order to have an adhesive with properties that vary gradually along the overlap, allowing a uniform stress distribution along the overlap. This allows for a stronger and more efficient adhesive joint. It is possible to work with much smaller areas, reducing considerably the weight of the structure and obtaining more reliable joints. The adhesive stiffness would vary along the overlap, being maximum in the middle and minimum at the ends of the overlap. The processes tested in this work were dielectric heating using a domestic microwave oven and conventional oven heating. Different amounts of carbon black were used and functionally dispersed along the bondline length in order to obtain a functionally graded joint. The functionally graded joints were found to have a higher joint strength compared to the cases where the carbon black was dispersed uniformly along the overlap or where the adhesive was used without carbon black. An analytical model was used to assist with the prediction and the assessment of the possible effectiveness of a graded joint concept.     

低成本E_2级人造板用脲醛树脂胶的制备及其应用

采用碱-酸-碱工艺,控制酸性阶段的pH值为4.0～4.3,n(F)/n(U)=1.15～1.23,研制出可用于胶合板和中密度板(MDF)生产的脲醛(UF)树脂胶。该胶制备工艺简单、游离甲醛含量低、制胶时间短、再现性好、成本低且贮存期达30 d以上。以NH4Cl为固化剂压制的胶合板,其胶合强度符合Ⅱ类板的国家标准,甲醛释放量<3.0 mg/L;不加固化剂直接压制的MDF,其强度和甲醛释放量达到E2级标准。     

环氧改性醇溶性丙烯酸酯干式复膜胶的研制

介绍了一种新型环氧改性醇溶性丙烯酸酯干式复膜胶的制备方法和性能。首先以环氧树脂E-44和丙烯酸(AA)为原料,合成了一种丙烯酸环氧单酯(EA);再以乙醇为溶剂,采用半连续加料法合成了醋酸乙烯酯(VAc)、丙烯酸丁酯(BA)、丙烯酸2-乙基己酯(2-EHA)和EA四元共聚物。该复膜胶合成的适宜条件为:m(VAc)∶m(BA)∶m(2-EHA)∶m(EA)=40∶25∶20∶15,w(引发剂)=1.0%,反应温度为73℃,反应时间为7h。实验结果表明,该复膜胶可用于制备塑料复合薄膜,具有环保、无毒、剥离强度高和快速固化等特点,适用于快速干式复合薄膜的生产线。     

Elastomer modification of epoxy based film adhesives: adhesive and mechanical properties

Three approaches were employed to improve the flow and sandwich bonding properties of a nylon-carrier supported film adhesive based on carboxyl terminated butadiene acrylonitrile (CTBN)-modified novolac epoxy resin. These included the addition of a commercial acrylate flow modifier, replacement of novolac epoxy partly with solid diglycidyl ether of bisphenol A (DGEBA) resins, and replacement of CTBN partly with an epoxy functional acrylate terpolymer (EPOBAN). Adhesive properties such as lap shear strength (LSS), T-peel strength (TPS) and flatwise tensile strength (FTS) on honeycomb core bonded sandwich specimens were evaluated using aluminium adherends. The addition of the flow modifier in low concentrations enhanced the flexibility of the system and resulted in a marginal increase in LSS, TPS and FTS. Replacing novolac epoxy partly with solid DGEBA resulted in a less brittle system with enhanced LSS and TPS, but with reduced FTS due to the decreased flow characteristics. A substantial increase in FTS was observed when CTBN was partly replaced with EPOBAN. The introduction of EPOBAN resulted in good flow and fillet properties and the optimum FTS was obtained for the composition based on 25/75 CTBN/EPOBAN ratio. Mechanical properties of selected systems were also studied in addition to adhesive properties.     

热塑性聚酰亚胺微电子薄膜的制备

以微电子业所急需的聚酰亚胺薄膜为背景,采用一种热塑性聚酰亚胺树脂(TPI),实验测定了聚合物溶液特性、干燥工艺及热拉伸性能。在化学环化过程中聚合物溶液粘度随时间逐步增大;15 h后粘度和重均相对分子质量及分布趋于稳定。薄膜溶剂含量在干燥初期急剧下降,干燥速率随干燥温度升高而增大。TPI树脂表现出良好的热塑拉伸性能,当温度高于其玻璃化温度时,最大拉伸比随升温速率降低而增大,而随拉伸载荷增加呈现出先增后降。TPI薄膜经拉伸处理后其力学性能得到明显提高,综合性能与日本钟渊TP E薄膜相当。     

Study of the singular term in mixed adhesive joints

In the numerical modelling of mixed adhesive joints, where different materials are disposed along the bond-lines, trimaterial singularities may arise at the adhesive bands transition points, resulting in mesh-dependent models. This work is focused on the study, characterization and treatment of these type of singularities. Firstly, the selection of an intermediate adhesive material for generating a tailored transition between bands is addressed, using analytical solutions and then corroborating by means of a novel technique for determining the influence distance of the singularity with the finite element method as calculation tool. Furthermore, it is proved how a continuum material field transition between bands produces a convergent finite element solution applying the considerations of this framework (analytical asymptotic solutions). Finally, in order to achieve the best numerical convergence rate in the models, the optimum material transition function is obtained and checked through FEM.     

Analysis of mixed adhesive joints considering the compaction process

Incorporating a material properties variation along the bondlines has proved to be a useful method for improving adhesive joints performance. In this work, the potential of the technique is analysed for a single lap joint using the mixing adhesives approach. In order to include the compaction process effect in the structural analysis during the joint assembly, a computational fluid-dynamic model capable of integrating different resins along the bondline has been developed. Then, the results obtained from this model are mapped into a finite element model through an application developed for this purpose. Several parametric studies have been carried out comparing different configurations in terms of maximum load capacity of the joints. Finally, one of these joints configurations has been manufactured using a special device developed for assembling these mixed adhesive joints and tested. This banded configuration have shown both numerically and experimentally an ultimate load improvement of over 70%.