干挂石材用胶粘剂耐久性分析测试研究

采用80℃热老化、湿热老化和80℃水浴老化等三种老化方式对干挂石材系统用的两种胶粘剂(包括干挂胶和云石胶)进行实验室加速老化试验,通过对不同老化程度的试件进行力学性能测试,确定了胶粘剂的剪切强度和弯曲强度在不同老化条件下随时间的变化趋势.借助动态热机械分析仪(DMA)研究了胶粘剂的热稳定性,表征了胶粘剂各老化阶段的储能...     

CFRP/铝合金粘接接头在低温环境中的老化机理研究

采用胶粘剂哑铃试件,结合SEM(扫描电镜)分析,研究了胶粘剂、CFRP和CFRP/铝合金粘接接头在长期低温(-40℃)作用下的老化失效机理。研究结果表明:低温老化对胶粘剂的力学性能和CFRP表面粘接性能影响不大,但是热应力会降低胶粘剂和CFRP纤维/基体界面力学性能;CFRP/铝合金剪切接头失效强度的下降主要是由胶粘剂的性能下降引起,对接接头失效强度的下降主要是由胶粘剂和CFRP性能共同下降引起,随着老化时间的增加,CFRP的影响减小。因此,在复合材料粘接结构老化研究时需要考虑胶粘剂、复合材料的老化以及受力形式的影响。     

改性双马来酰亚胺胶粘剂的研究

本文报导了一种环氧和橡胶改性的双马来酰亚胺型胶粘剂。研究了胶粘剂的组份对性能的影响,筛选出胶粘剂的配方,并对胶粘剂的固化反应、常温和高温粘接强度、热老化、湿热老化等进行了研究。结果表明,该胶粘剂可在比双马来酰亚胺较低的温度下固化,在150～200℃下具有高的强度保持率,特别是具有优良的湿热稳定性。     

环氧-聚酰胺胶粘剂的热老化行为研究

研究了不同热老化温度下环氧-聚酰胺胶粘剂的性能变化规律。采用SEM观察表现形貌,以XFT-IR分析微观结构,通过TGA分析等技术研究了热对胶粘剂性能的影响及老化机理。结果表明,在热环境下随着老化时间的延长,粘接强度显著下降;老化温度越高,下降幅度也越大。胶粘剂性能下降的主要原因是高分子链节发生热氧老化而断裂降解。     

原料对塑胶跑道用单组分聚氨酯胶粘剂性能的影响

研究了塑胶跑道用单组分聚氨酯胶粘剂各个组分对其性能影响。综合分析表明,当聚醚多元醇N-340G的相对分子质量在4000~5000、特种助剂E的使用量在10%左右时,合成的胶粘剂机械性能和性价比最值;老化实验结果表明,同等条件下,用胶粘剂6制得的样品老化后仍比其它品种胶粘剂的机械性能高。     

高分子材料的老化研究进展

介绍了有关高分子材料在环境因素作用下老化研究的历史,综述了橡胶、塑料及胶粘剂的环境老化行为、国内外研究的发展及现状,展望了高分子材料老化的研究动向和发展趋势.     

热-力耦合环境下结构胶粘剂强度退化试验研究

本研究设计了Araldite~?2015型结构胶粘剂热-力耦合环境下的老化试验及试验所需的加载夹具。通过测量胶粘剂老化过程中的蠕变伸长量,获得了该胶粘剂试件的蠕变特性参数,为建立蠕变有限元模型提供试验依据。另对老化后的胶粘剂试件进行准静态拉伸试验,获得了胶粘剂试件的失效强度随老化时间的增加出现先稍微升高然后迅速降低的强度退化趋势。     

复合材料胶接接头温度-湿度-载荷老化机理研究概述

概述了单一影响因素(温度、湿度、载荷)分别对胶粘剂、复合材料和复合材料胶接接头的影响机理,总结了多因素耦合作用下的老化机理。研究结果表明:复合材料胶接接头中的胶粘剂、复合材料以及胶接界面在温度、湿度、载荷的作用下都会发生变化,对接头的性能都有影响。在未来研究复合材料胶接结构老化机理中,在定性分析的基础上进行定量分析,并且需要考虑复合材料老化对胶接接头性能的影响。     

TiO2-TDI粒子改性聚氨酯胶粘剂的市场性价比研究

采用TiO₂粒子和二氧化钛-甲苯二异氰酸酯(TiO₂-TDI)粒子对聚氨酯胶粘剂进行了改性处理,研究了不同添加量的改性粒子对聚氨酯胶粘剂硬度、羟基指数、拉伸剪切强度和表面形貌的影响。结果表明,改性聚氨酯胶粘剂的邵氏硬度随着二氧化钛粒子添加量的增加而逐渐增大,而老化1 000 h后,改性聚氨酯胶粘剂的邵氏硬度会随着TiO₂粒子添加量的增加而逐渐减小。随着老化时间从0增加至1 000 h,聚氨酯胶粘剂和改性聚氨酯胶粘剂的羟基指数(CI)都会随着老化时间的延长而逐渐增大,且相同老化时间下,PU+0.4%TiO₂-TDI的CI指数更小、拉伸剪切强度最大,其次为0.4%TiO₂改性聚氨酯胶粘剂。     

基于灰色关联分析的胶粘剂老化与环境因子研究

胶粘剂越来越多地应用于武器系统中,其贮存过程中的老化现象是影响武器系统可靠性的重要因素。为研究自然贮存环境中胶粘剂的老化现象,通过使用灰色关联分析法,量化分析复杂灰色系统中不同环境因子与胶粘剂老化现象的关联程度。利用自然贮存试验中胶粘剂老化现象数据,计算各贮存周期内胶粘剂老化速度数据,再结合相应贮存周期内环境因子的统计数据进行灰色关联分析。研究结果表明:试验中四种环境因子对胶粘剂老化速度影响程度从高到低依次为温度、日照时长、湿度和降雨量,与理论定性分析的结果相符。该方法能很好地反映环境因子对胶粘剂性能退化的影响,可为今后进行胶粘剂环境试验提供理论依据。     

AGING CHARACTERIZATION OF ADVANCED POLYMER SYSTEMS

Aging of three advanced polymer systems used as adhesives in the aerospace industry is characterized by Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR-FTIR), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS).Since significant changes in mechanical properties were observed for AF191, FM®73, and FM®5 bonded joints, the purpose of this work was to identify whether there is any chemical and physical degradation for the adhesives used in these joints. Each of the adhesives has been evaluated after exposing to Hot/Wet and Hot/Dry environments for 5000 h. They were also thermally cycled in conditions that represent subsonic and supersonic cruise. Hot/wet exposures demonstrated a greater amount of possible degradation than hot/dry or thermally cycled exposures. The hot/wet aging condition resulted in more pronounced O-H, C-H, and N-H infrared absorptions, reduced glass transition temperature of adhesives, and reduced tensile and fracture properties of corresponding bonded systems. Overall, these adhesives were chemically very stable under the environments to which they were exposed, even though some of the joints showed reduced fracture toughness due to the exposure. Additional work is needed to understand the mechanism causing the change in joint properties when exposed to these environments.     

A method for screening adhesive materials for small displacements during environmental aging

This paper discusses the use of etalons fabricated from prepared glass slides to quantify the dimensional stability of two adhesive materials in damp environments. This technique facilitated the screening of adhesives for a kinematically demanding application. In addition to describing the etalon technique, additional data are provided on the performance of the device with the selected adhesives. One of the adhesives is simply identified as a cationic cured adhesive, while the other adhesive was Loctite 3615. A range of adhesive bond gaps from 50 to 500 μm was examined for the adhesive that showed the least displacement resulting from environmental aging. The results of this testing were applied to a kinematically sensitive device for verification of the adhesives use in this geometry.     

New adhesives: Bismaleimide liquid crystals containing polymethylene flexible groups and aramide–arylate mesogen groups

Four adhesives (one adhesive BEA 811 and three adhesives BENDA 811) containing new bismaleimide (BMI: B 8 and B 11) with aramide/arylate and polymethylene as mesogen and flexible groups, respectively were studied. Starting from the BMIs, eutectic mixture BE 811 was developed. It presents low melting temperatures (153.4 °C) and crosslinks giving liquid crystal ordered state. The new adhesives have been prepared by mixing the original BMIs (eutectic mixture of B 8 and B 11: BE 811) with other compounds usually used in the formulations of composite materials and structural adhesives. Adhesive formulations of BEA 811, mixture BE 811 and DABA, and BENDA 811, mixture BE 811, DABA and NOVOLAC, crosslink generating an ordered state as well. The relation between structure, thermal properties and breaking force was investigated. Subsequently, these mixtures were tested as iron–iron adhesives. Finally, aging tests were achieved, in both laboratory and in-situ environments (in Vietnam and Morocco). The high performances of thermoset adhesives (BENDA 811 and BEA 811), compared to industrial polyimide adhesive (MATRIMIDE 5292), were attributed to molecular structures and their crosslinking ability in the liquid crystal state.     

Behavior of amine-modified urea–formaldehyde-bonded wood joints at low formaldehyde/urea molar ratios

Urea–formaldehyde-bonded wood products are limited to interior nonstructural applications because of their poor durability under cyclic moisture or humid environments. The stability of solid-wood joints and particleboards can be enhanced by bonding with urea–formaldehyde adhesives modified with di- and trifunctional amines at an effective resin formaldehyde-to-urea mol ratio (F/U) of 1.6; however, particleboard formaldehyde emissions were not improved over those from boards made with unmodified adhesives and were unacceptably high. The relative effectiveness of selected modifications was investigated at resin form aldehyde-to-urea (F/U) molar ratios of 1.4 and 1.2 Solid-wood joints and particleboards made with modified adhesives, an unmodified adhesive, and a phenol formaldehyde (PF) resin were subjected to cyclic soak-dry (cyclic stress) treatments and moist-heat aging. Formaldehyde emissions from particleboards were also determined. At F/U 1.4, the resistance of solid-wood joints made with modified adhesives to cyclic stress and moist-heat aging was equal to that of PF-bonded joints and superior to that of joints bonded with unmodified adhesive. The resistance of particleboards made with modified adhesives was greater than that of boards made with unmodified adhesive but less than that of PF-bonded board. Solid-wood joints and particleboards made with F/U 1.4 resins performed better than did those made with F/U 1.2 resins. Particleboards made with F/U 1.2 resins had formaldehyde emissions well below the standard, and room temperature aging or bonding at high temperature reduced emissions substantially. © 1994 John Wiley & Sons, Inc. 1

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Moisture durability of four moisture cure urethane adhesives

Moisture durability of four low modulus adhesives was examined. The four low modulus adhesives all had the same basic moisture cure polymer but contained different fillers and additives. Hot-dipped galvanized steel was bonded to random fiber-reinforced unsaturated polyester and aged in two moisture environments for various durations. Adherend surface wipes included acetone, isopropyl alcohol and a typical surface contamination for galvanized steel (an organic lubricant). Diffusion coefficients, moisture uptake and modulus changes due to moisture environment were determined for the adhesives and the fiber-reinforced plastic (FRP). The moisture cure adhesive with clay and poly(vinyl chloride) (PVC) as fillers (adhesive 252) had the highest retained lap joint strengths. Initially, adhesive 252 had single lap joint strengths of 1.47 ± 0.08 MPa for acetone-wiped joints and 1.39 ± 0.33 MPa for organic lubricant-wiped joints. After accelerated aging in a cataplasma environment for 9 weeks, lap joint strengths fell to 0.61 ± 0.08 MPa for acetone-wiped joints and to 0.65 ± 0.11 MPa for organic lubricant-wiped joints. Environmental scanning electron microscopy (ESEM) and energy-dispersive spectrometry (EDS) showed that the actual failure locus was through a corroded zinc layer and between the adhesive and the zinc surface after aging. Dynamic mechanical analysis (DMA) showed that the modulus for adhesive 252 dropped from 21.7 to 13.9 MPa after cataplasma aging. From finite element analysis (FEA), this modulus drop corresponded to a drop in normal stress concentration from 0.75 to 0.57, and a drop in shear stress concentration from 1.41 to 1.36 at a point 0.5 mm from the end of the single lap joint overlap.     

纸标签压敏胶钙离子老化的研究

考察了不同老化条件下铜版纸对两种类型压敏胶性能的影响.结果表明,老化后,压敏胶的初粘强度和剥离强度下降,而剪切强度呈上升趋势.钙离子交联是影响压敏胶性能的主要因素,而湿度则会加速该老化进程.     

Aging effect in the adhesion of a PC/CPVC arrangement for application in thermo-solar collectors

This work studies the aging of materials in a polycarbonate/chlorinated polyvinyl chloride (PC/CPVC) arrangement, used in a flat plate thermo-solar collector. Typically, PC is used as an absorbing surface and CPVC in entrance and exit heads of the flow, which in this case is water. In this study, two types of methacrylate adhesives were used to bond both plastics, denominated MP and SK. The experiment comprised a study of adhesion behavior between these polymers and the adhesives, in contact with distilled water at different temperatures and different time intervals, simulating the corresponding operating conditions of a thermo-solar collector. Results showed that the SK adhesive did not fail under these conditions, while the MP adhesive underwent evident aging and adhesive failure. In addition, the PC presented a reduction in its mechanical strength when it was subjected to higher temperatures and periods of hygrothermal exposure, probably due to physicochemical deterioration caused by hydrolysis.     

A study on durability of joints bonded with pressure-sensitive adhesives

The use of adhesive bonding as fastener presents very high usage potential, especially for different environments. However, the designers do not have enough data yet to address the changes in the mechanical properties of adhesives in the course of time. In this study, the ageing of film-type adhesives, Structural Bonding Tapes (SBT) 9244 and 9245, which are different in thickness and possess pressure-sensitive and visco-elastic properties, was investigated. First, the bulk adhesive specimens were prepared and exposed to two different environmental conditions until saturated. In the same time, single lap joints with two different adhesive layer thicknesses, consisting of AA2024-T3 as the adherend, were exposed to the same environmental conditions for exposure times of 90 days. The immersion environments were 100% relative humidity (RH) and 3.5% NaCl solution. At the end of exposure time, the failure surfaces were examined by Scanning Electron Microscopy (SEM) after the strength of joints was determined with the lap shear test. Both SBT adhesives absorb more water from 100% RH than from 3.5% NaCl solution and, therefore, they deteriorate rapidly in 100% RH. In addition, as the thickness of adhesive layer increases, the loss in the strength increased.     

Adhesives in demanding applications

Structural adhesives are nowadays employed extensively in structural engineering applications where advantage is made of many outstanding attributes, most notably their ability to confer reduced weight, improved fatigue performance together with reduced production and life cycle costs. Increasingly in recent years, attempts have been made to employ bonded structures in harsh environments. In this article an attempt is made to consider the demanding environments which bonded joints are frequently required to resist, focusing principally on hot/wet and high temperature conditions. With the former, the ways in which water can adversely affect joint behaviour are highlighted and the factors, such as nature of adhesive and surface treatment, crucial to optimum joint performance are discussed. Adhesive joints in high temperature environments are discussed in terms of early high temperature adhesives, designed with little thought to processability, together with more recent developments in high temperature adhesives where processability has been ‘engineered’ into the polymer structure.     

SBS胶黏剂热老化性能的研究

胶黏剂的性能不仅和胶黏剂本身的化学结构、合成方式有关,而且使用条件对其性能影响很大.采用SBS弹性体、增黏树脂、接枝剂及按一定比例配合而成的混合溶剂制备了一种价廉物美的新型环保型胶黏剂.考查了热老化行为对SBS装饰胶黏剂性能的影响,通过热分析仪考查了300h内胶黏剂的玻璃化温度、剥离强度的变化.并通过扫描电子显微镜(SEM法)和X射线能谱(EDX法)考查了SBS装饰胶表面形貌和表面碳元素组成在50h、,100h、200h和300h热老化的微观变化情况,结果表明此种胶黏剂热老化性能良好.