Strengthening of the adhesive bond using a mixture of adhesives between dissimilar adherends in a single lap joint

Abstract

Adhesive bonding is the best alternative to riveting in aircraft structures but the strength of the adhesive bonded joint is low and is limited by strength of adhesive. Strengthening of adhesive bonding is an important requirement. In this work, an attempt has been made to strengthen the adhesive bonding by mixing different quantities of brittle adhesive in the ductile adhesive and vice-versa. Two different adhesives, one brittle (AV138) and another ductile (Araldite-2015) adhesive have been considered. Initially single lap joint has been constructed between the CFRP and aluminium with individual adhesives, then the mixture of adhesives have been used in the bonded region in varied proportions. The X-ray radiography and ultrasonic testing have been performed to check the quality of bonding. Uniaxial tensile tests have been conducted on the lap joints along with Digital Image Correlations (DIC) to obtain the individual and mixed adhesive bond strength. The failure patterns have been identified using optical and scanning electron microscope. These studies indicate that strengthening of the adhesive bonding achieved by mixing of two adhesives and highest bond strength obtained when the mixture of AV138 and Araldite-2015 adhesives are used in equal proportions.     

室温固化耐600℃高温有机硅树脂耐热棉毡用胶黏剂

合成了苯梯树脂及耐热黏料树脂,二者以适当的比例配合再添加填料、促进剂、催干剂等来制备一种胶黏剂,并对胶黏剂与钛合金、隔热材料的胶接进行了探索性研究,该胶黏剂是可以室温固化的有机硅树脂胶黏剂,胶黏剂对钛合金与耐热棉毡均有较好的粘接性能,并且制得的胶黏剂在较高温度（650℃）有着较小的热失重,符合了钛合金与隔热材料实际粘接的需求。     

Reversible Bonding of Aromatic Thermosetting Copolyesters for In‐Space Assembly

Reversible bonding is an attractive option for assembly and disassembly of reconfigurable space structures due to the simplicity of the fastening concept. Interchain transesterifications reaction [ITR—a type of dynamic covalent exchange reactions afforded by aromatic thermosetting copolyesters (ATSP)] between two ATSP coatings can successfully be used as a reversible bonding concept, provided that the mode of debonding is completely cohesive (rather than adhesive or delaminatory from metal substrate). An optimization study is carried out on the ITR bonding for which ATSP coating is applied on 7075 aluminum substrates and bond/debond experiments are carried out using a custom‐built tool kit. The toolkit enables precise control over bonding pressure, temperature, and contact time. Bonding conditions are optimized to produce complete cohesive failure with maximized bonding strength. Optimized bonding parameters are successfully implemented to realize 50 cycles of bond/debond process without compromising adhesive strength. Experiments show a debonding strength of 28.7 MPa for the 51st cycle at room temperature—significantly in excess of prior highest reversible bonding strength results found in the literature. These results, in addition to the high thermal stability and glass transition temperature of the base polymer, indicate viability of this reversible bonding concept for in‐space assembly.     

带油、带水表面粘接技术研究

研制了一种新型快固丙烯酸酯胶粘剂,讨论了被粘表面存在的油、水以及水和油混合物对于粘接强度的影响。结果表明,油面抗剪切强度最高可达32.6MPa,比非油面提高4%～9%。此外,还对水中粘接堵漏进行了探讨。     

异氰酸酯改性VAE胶粘剂的研究

本文介绍了二异氰酸酯改性VAE胶粘剂的方法，通过对VAE水解程度及加入异氰酸酯进行交联反应的研究，给出了产品的制备工艺和配方，讨论了反应温度、时间、二异氰酸酯用量、填料等对胶粘剂性能的影响。改性后的VAE胶粘剂的粘结性能、胶膜耐热性、耐水性等有了很大提高。改性后的胶粘剂可用于木材、纸张、织物同塑料等的粘接。     

均苯四甲酸酐固化聚丁二烯环氧树脂胶粘剂的研究

采用均苯四甲酸酐(PMDA)固化聚丁二烯环氧树脂(ELPB),制备了ELPB/PMDA耐高温胶粘剂,并使用傅里叶红外光谱仪(FT-IR)、热重分析仪(TGA)、拉力机和数码显微镜对固化产物的性能进行了表征。实验结果表明,在200℃固化2h的条件下,PMDA可以对ELPB成功地固化;固化后的胶粘剂具有良好的耐热性能,其失重3%时的分解温度为300℃;该胶粘剂对铝/铝合金的粘接强度达到15MPa;剪切破坏是以内聚破坏为主的混合破坏,表明该胶粘剂对金属有较好的粘接性能。     

Amine-cured epoxy resins: Adhesion loss due to reaction with air

The variability in adhesive bond strength and extent of cure of room-temperature, amine-cured epoxy resins has limited their applications. This paper reports the observation of microscopic crystal formation at the interface of the resin with air, resulting in a variably lower resin curing rate, extent of cure, and up to ten times lower adhesive bond strength. These crystals were identified as an amine bicarbonate salt, resulting from the reaction of the amine at the surface of the curing mixture with air. The bicarbonate formation seems to be general for the types of hardeners used in room-temperature curing. The amine-bicarbonate compound can be decomposed back to the amine by heating above 80°C. Otherwise, exposure of room-temperature systems to air before bonding is undesirable.     

Effect of heat treatment temperature and surface roughness to the PDMS-FR4 adhesive bonding

The current work investigates the use of liquid polydimethylsiloxane (PDMS), with a 10:1 ratio of prepolymer:curing agent?=?10:1 as the intermediate layer for adhesive bonding with Flame Retardant 4 (FR4). The spin coating of liquid PDMS on FR4 allows irreversible adhesive bonding with the solid PDMS. The strength of the proposed adhesive bonding technique has been investigated under different treatment temperatures: oven-heated at 60?°C, 70?°C, and 80?°C, cooled down in the room temperature of 25?°C, and exposed to direct sunlight at 35?°C. All the samples were left for 6?h. Investigations were conducted to analyze the effect of FR4 surface roughness on the strength and quality of the adhesive bonding. The standard procedure of American Standard Test Measurement (ASTM) D1002 was followed to verify the strength of PDMS-FR4 adhesive bonding. Strongest adhesive bonding, free from air bubbles, was obtained from a sample with smooth surface of FR4 that has undergone a cooling down treatment in the room temperature of 25?°C. FR4 was coated by solder mask to obtain smooth surface. The techniques reported in this paper are simple, straightforward, and effective to be implemented with FR4 as a base material for adhesive bonding with PDMS, thus eliminating expensive and complicated operating equipment as widely used in the oxygen plasma-assisted bonding treatment. Another benefit from this adhesive bonding technique is the fact that it avoids the use of expensive oven or hot plate.     

氯丁橡胶与金属热硫化型胶膜的研究

采用机械共混法和胶料成膜技术制备出一种酚醛树脂(PF)-橡胶型膜状胶粘剂(胶膜)。结果表明:当n(37%甲醛)∶n(苯酚)∶n(氢氧化钠)=1.8∶1∶0.1、反应温度为70℃和反应时间为2.5 h时,合成的甲阶PF具有较高的羟甲基含量(28.3%),满足PF-橡胶型胶膜的制备要求;当m(氯丁橡胶)∶m(氯化天然橡胶)∶m(PF)∶m(炭黑)=100∶(5～10)∶(70～80)∶40、m(PF)∶m(硼酚醛树脂)=4∶1时,胶膜的剪切强度超过5.0 MPa、180°剥离强度超过4.0 kN/m且胶接件的破坏形式多为橡胶内聚破坏;该胶膜具有较好的热稳定性(热失重温度为300℃左右),满足氯化橡胶生胶片与金属之间的热硫化胶接要求;该胶膜与适宜底胶配合而成的双涂型胶接体系,可实现氯化橡胶生胶片与树脂基复合材料之间的热硫化胶接。     

Adhesive bonding of polyethylene

The treatment of polyethylene film with aqueous ammonium peroxydisulfate solutions prior to adhesive bonding to aluminum has been studied. Such pretreatments resulted in the formation of adhesive joints of high strengths when bonded with a conventional epoxy adhesive. The effect on the tensile shear strength of adhesive joints of variations in the treatment time and temperature and the peroxydisulfate concentration has been examined. The use of certain catalysts for the reaction has also been studied. Tensile shear strengths at least as high as with other pretreatment methods have been obtained.     

稀释剂对有机玻璃粘接用UV固化胶黏剂的影响

活性稀释剂对uv固化反应过程有重要的影响。为了考察稀释剂对有机玻璃粘接用uV固化胶的影响,采用复配法重点考察了稀释剂的种类、含量配比、表面张力等对有机玻璃粘接用uV胶黏剂的粘接性能的影响。结果表明,采用单官能团稀释剂IBOA和双官能团稀释剂TPGDA进行复配,其混合比例控制在（1：1）,总量控制在胶黏剂的50％一55％对有机玻璃的粘接效果最佳。     

Preparation and performance of ceramizable heat-resistant organic adhesive for joining Al2O3 ceramics

Ceramizable heat-resistant organic adhesive (CHA) was prepared by using preceramic polymer polysiloxane as matrix, TiB₂ ceramic powder and low melting point glass powder as additives. The curing mechanism, thermal stability properties, phase composition after pyrolysis, structural evolution of bonding layer and bonding mechanism of the adhesive were investigated by FTIR, TGA-DSC, XRD, SEM, FESEM and bonding strength tests. Results of bonding tests showed the maximum shear strength of the joints was 21 MPa when heat treatment at 1200 °C for 2 h in air. Polysiloxane resin acted as crosslinking adhesive at low temperatures and tended to convert to ceramic bonding layer at high temperatures, resulting from ceramization reaction with active fillers. The formation and growth of ceramic phase after heat treatment enhanced the thermal stability and bonding performance of the adhesive at high temperature.     

淀粉IPN型环保胶粘剂的合成

采用淀粉改性的聚醋酸乙烯酯(PVAc)乳液与聚氨酯(PU)预聚体交联制成了具有IPN(互穿网络聚合物)结构的胶粘剂。探讨了各原料的用量及反应温度等因素对该胶粘剂的制备及性能的影响。实验结果表明,制备该胶粘剂的适宜工艺条件为:氧化淀粉10.0g,水40.0g,聚乙烯醇(PVA)15.0g,PVAc25.0g,PU预聚体5.0g,乳化剂2mL,引发剂0.8g,扩链剂2mL,无机物填料5.0g,反应温度为65～85℃;由此制得的淀粉IPN型环保胶粘剂具有耐低温性好、耐水性佳、粘接强度高及无甲醛等优点,可用于层压板与纸塑、木塑复合材料的粘接。     

氯丁橡胶与甲基丙烯酸甲酯接枝聚合胶粘剂的研制

叙述了氯丁橡胶与甲基丙烯酸甲酯接枝聚合的反应原理，胶粘剂溶液的配方以及制造工艺操作过程。并阐明对胶粘剂粘着力产生影响的一些因素。     

中温固化的金导电胶的研究

一种金导电胶,由改性的酚类树脂（NF）、片状金粉与球状金粉的混合粉末、少量锑粉和醇类为主的溶剂组成,固化温度范围150－300℃,体积电阻率5×10(-4)Ω．cm,存放或可达半年以上,该导电胶可应用在二、三极管及组合电路中。     

机箱托架导轨胶膜粘接新工艺技术

对机箱托架导轨的材料选用聚四氟乙烯软带,粘接采用胶膜粘接工艺进行了全面研究,确定了胶膜粘接热压工艺参数:热压温度130~140℃,时间15~20min,压力3~4kg/cm2。对胶膜粘接工艺(新工艺)和胶黏剂粘接工艺(老工艺)进行了比较,结果表明:选用的胶膜粘接工艺参数合理,在最佳工艺参数条件下,胶膜粘接的剥离强度是胶黏剂粘接强度的1.5倍以上,工艺周期同胶黏剂粘接周期相比,缩短了70%以上,满足机箱托架导轨粘接要求,因此胶膜粘接工艺是托架导轨粘接首选。     

水相中合成木质素环氧树脂及其在木材胶黏剂中的应用

以木质素为原料,在水相中合成一种适用于木材胶黏剂的木质素环氧树脂。为了考察木质素环氧化反应条件对木质素环氧树脂的羟基和环氧基的影响,以及对胶合板的胶合强度的影响,采用FT-IR和31PNMR对木质素环氧树脂结构进行表征,并用TG和DTG对木质素环氧树脂的热稳定性进行分析。结果表明,环氧化反应主要发生在酚羟基上,在反应过程中,相比环氧氯丙烷,NaOH的加入量对木质素环氧树脂结构和胶合板的胶合强度影响更大。随NaOH加入量增加,木质素环氧树脂中环氧基团逐渐增多,胶合板的胶合强度呈现先升高、后降低的趋势。当木质素的羟基与NaOH摩尔比为1:1时,由木质素环氧树脂制得的胶合板胶合强度达到最大,湿强度达1.61 MPa,超过国家标准II类板的要求(≥0.7 MPa)。采用扫描电镜研究了黏接机理,发现环氧化程度提高时,固化后的木质素环氧树脂的结构更加稳定且致密,导致胶合板的胶合强度也提高。但过高的环氧化程度会增大胶黏剂的粒径,导致胶黏剂与木板不能形成更好的机械互锁结构,从而降低胶合板的胶合强度。还进一步简化了木质素环氧树脂木材胶黏剂的合成工艺,使环氧化反应后的体系无需处理即可直接应用于木材胶黏剂,减少了胶合板生产工艺流程。此外,经过30天的储存期,胶黏剂黏合强度没有明显下降。通过与商业脲醛树脂木材胶黏剂对比,其黏接强度可以达到商业脲醛树脂的水平。     

Adhesive bonding of RIM urethane

Two techniques for bonding reaction injection moulded urethane to itself and to other substrates are described. For in-mould bonding, details of substrate preparation, choice of adhesive and processing conditions are given. Where the geometry of the parts is complex, the structural bonding of individually moulded components has to be carried out: the development and properties of a two-part urethane adhesive designed for this purpose are detailed.     

结构胶粘带的应用性能研究

采用无基材或以玻璃纤维布为基材,制备了具有良好压敏性的结构胶粘带。对其应用性能的研究结果表明,该结构胶粘带在固化前有较高的剥离强度和良好的贮存稳定性,而固化后可获得>20MPa的常温剪切强度,且耐热和耐水性能较好。文章还研究了结构胶粘带的固化工艺。     

Bonding properties of epoxy resins containing two mesogenic groups

Liquid‐crystalline epoxy resins, with introduced aliphatic chains between two mesogenic groups, were synthesized and their adhesive bonding properties were compared to those of the bisphenol‐A–type epoxy resin and the liquid‐crystalline epoxy resin, previously reported. The bonding strength of the former resin system was higher than that of the two later systems. We suggest that the high bonding strength of the twin mesogenic epoxy resins, cured with an aromatic amine, was attributable to the large plastic deformation of the adhesive layer in the fracturing process. We also investigated the effects of the aliphatic chain length in the twin mesogenic epoxy resin on their dynamic mechanical and bonding properties. The bonding strength of the cured twin mesogenic epoxy resins increased with an increase in the aliphatic chain length. We suggest that the high bonding strength of the system introduced by the long aliphatic chain was attributable to the large plastic deformation of the adhesive layer because of the higher network mobility. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3721–3729, 2004