紫外光固化银包铜导电胶的制备及性能研究

以银包铜粉为导电填料,环氧丙烯酸树脂为基体树脂制备紫外光固化导电胶,采用1-羟基环己基苯基甲酮和二苯甲酮作为复合光引发体系实现导电胶的完全固化。利用金相显微镜、四探针电阻测试仪和差示扫描量热仪对固化后的试样微观结构和性能进行表征。结果表明:当银包铜粉含量为70%,固化时间为120~180s,光引发剂含量为4%时,导电胶固化完全,制得的导电胶电阻率最低,为1.122×10~(-3)Ω·cm,且固化后的导电胶具有良好的热稳定性。     

固化过程对导电胶体积电阻率的影响

采用三种不同固化收缩率的树脂配制了三种导电胶。通过实验研究了等温固化过程中树脂基体的固化收缩率对导电胶体积电阻率的影响。研究结果表明,树脂基体的固化收缩率越大,对应导电胶的体积电阻率越小。导电胶的体积电阻率与固化时间呈指数关系。导电胶在未固化时体积电阻率极大,其导电性的建立发生在树脂基体的凝胶化阶段,且在这一阶段中导电胶的电阻率急剧下降,凝胶化阶段完成后的导电胶电阻率变化较小。     

紫外光固化墨水应用研究新进展

UV喷墨墨水中包含着预聚物、单体、光引发剂、颜料、助剂等组分,其中预聚物是构成UV喷墨墨水组分的基本骨架,其性能对固化过程和固化膜的性质起决定作用;单体作为活性稀释剂影响墨水体系的黏度和固化速度;光引发剂的作用是吸收紫外光能量,同时产生游离基,促使油墨发生聚合反应,是光固化体系的关键组分。介绍了常见UV喷墨墨水中预聚物、单体和光引发剂的组成、特性以及最新应用研究动向。     

UV固化喷墨中光引发体系的研究

本文选择了6种光引发剂和5种颜料，测试了光引发剂和颜料的吸收谱图。研究了不同颜料体系的光引发剂与UV喷墨固化时间的关系，其中涉及单引发体系与复合引发体系对固化时间的影响。     

紫外光固化聚氨酯丙烯酸酯粘结剂的优化设计

采用红外光谱对聚氨酯丙烯酸酯(PUA)涂料的紫外固化过程进行定量分析;测试了不同配方和固化条件下涂膜的摆杆硬度、柔韧性和抗冲击性;考察了γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)对粘结剂附着力的影响,并对其作用机制进行了分析。结果表明,固化过程中C=C双键发生聚合,其转化率反映了涂膜的固化程度;增大光强、减少稀释剂用量和延长固化时间均有利于提高双键转化率和摆杆硬度;随着光引发剂浓度的增加,双键转化率先增后减;增大二官能PUA比例能够提高涂膜柔韧性和抗冲击性;KH570能够改善涂膜附着力,加入量越大改善效果越明显,且静置对附着力有很大影响;其作用机制是KH570分子中的双键与丙烯酸双键发生聚合,羟基与基底间形成氢键作用。     

光固化快速成型中光敏树脂固化机理研究

合成了一种适于光固化快速成型的环氧丙烯酸光敏树脂,探讨了该光敏树脂的紫外光固化机理,用SEM表征了树脂体系固化后的微观结构,用红外光谱(FTIR)对树脂体系固化过程进行了分析。研究结果表明:光敏树脂经紫外光固化后,呈交联的、不规则体型网络结构;树脂在光固化过程中,光引发剂的含量在一定数值范围内与光敏树脂中C=C双键的转化率成正比。     

紫外光固化聚氨酯丙烯酸酯粘结剂的优化设计EI北大核心CSCD

采用红外光谱对聚氨酯丙烯酸酯(PUA)涂料的紫外固化过程进行定量分析;测试了不同配方和固化条件下涂膜的摆杆硬度、柔韧性和抗冲击性;考察了γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)对粘结剂附着力的影响,并对其作用机制进行了分析。结果表明,固化过程中C=C双键发生聚合,其转化率反映了涂膜的固化程度;增大光强、减少稀释剂用量和延长固化时间均有利于提高双键转化率和摆杆硬度;随着光引发剂浓度的增加,双键转化率先增后减;增大二官能PUA比例能够提高涂膜柔韧性和抗冲击性;KH570能够改善涂膜附着力,加入量越大改善效果越明显,且静置对附着力有很大影响;其作用机制是KH570分子中的双键与丙烯酸双键发生聚合,羟基与基底间形成氢键作用。     

UV-LED磁性油墨固化时间影响因素研究

目的应用UV-LED固化技术来降低磁性防伪油墨的固化时间。方法选用环氧丙烯酸酯和二丙二醇二丙烯酸酯,通过改变两者的质量比来配制连接料,选用TPO和819为光引发剂,改变光引发剂的质量分数,固定其他组分,配制UV-LED磁性防伪油墨,打样并使用波长为395 nm的UV-LED光源照射,测定油墨的固化时间。结果数据结果表明,当连接料中环氧丙烯酸酯和二丙二醇二丙烯酸酯的质量比为1∶0.8,光引发剂选用819(质量分数为6%)时,磁性防伪油墨固化时间最快可达0.6 s,双键转化率最高可达96%。结论 UV-LED磁性防伪油墨固化时间的主要影响因素有预聚物与单体的质量比,光引发剂的种类与质量分数。在合理的粘度范围内,预聚物与单体的质量比值越大,固化时间越短;单一光引发剂所释放的自由基越多,固化速率越高,光引发剂质量分数越高,固化时间越短。     

SBS/丙烯酸酯紫外光固化压敏胶带的制备与性能

将SBS/丙烯酸酯胶液经UV固化制成压敏胶带,分析了胶液组成、光引发剂的种类与用量、UV辐照时间等对压敏胶性能的影响,并将SBS/丙烯酸酯胶液应用于保护膜胶带,对其性能进行了测试.结果表明,以HCP为光引发剂,UV辐照25s时胶液可固化完全,并获得较好的粘接性能.SBS/丙烯酸酯胶液还可用于制备具有良好性能的保护膜胶带.     

光敏聚氨酯丙烯酸酯固化收缩应力的影响因素

光敏聚氨酯丙烯酸酯体系的光固化速度快,然而快速的聚合动力学会导致树脂在光聚合过程中内应力释放受到阻碍,出现严重的聚合收缩现象,使体系双键转化率降低,光固化材料性能较差。为了了解性能与聚合过程之间的关系,文中采用中红外光谱仪和光流变仪相结合的技术来监测光敏聚氨酯丙烯酸酯(PUA)的光聚合过程。结果发现,引发剂含量增加可以提高固化速率,降低聚合过程中的法向应力;UV光强降低会减少收缩应力,但同时也会降低体系的双键转化率。当单体官能度增加,凝胶点推迟出现,收缩应力降低。随着稀释剂单体中乙氧基柔性链增加,固化材料的柔韧性增大,从而收缩应力降低。     

紫外光固化导电胶的制备及固化动力学机制

为研究紫外光固化导电胶的性能及固化机制,以银包铜粉、环氧丙烯酸树脂为原料制备固化胶,采用刮涂法将浆料涂覆到载玻片上,置于紫外光下固化获得导电涂层。对试样的微观结构、力学和电学性能进行表征,对固化体系的热行为及固化反应动力学机理进行了研究,并利用Kissinger和Grane模型计算固化反应的活化能和反应级数。研究结果表明:光辐射下导电胶层可快速固化;当填料含量为70wt%时,浆料达最低电阻率1.122mΩ·cm;填料含量75wt%时剪切值最大为57.4MPa;活性稀释剂含量为35wt%时,浆料具有最佳的固化速度和网联结构;固化反应过程中表观活化能为15.17kJ/mol,固化工艺为172.3℃→302.05℃→369.35℃,为一级固化反应;浆料在200℃以下具有较好的抗氧化性能。     

低温快速固化环氧导电胶的制备与性能

采用E-51型环氧树脂为导电胶基体树脂, 低分子量聚酰胺树脂(PA)为固化剂, 填加经硅烷偶联剂(KH550)改性后的纳米级和微米级铜粉及助剂制备导电胶。首次采用了液态固化剂(低分子量的聚酰胺酯), 以解决导电胶制备过程中填料用量受限的难题。通过正交试验方法探讨了导电胶中导电填料的含量、导电填料配比、硅烷偶联剂用量和还原剂添加量对导电胶粘接性能和导电性能的影响, 对导电胶的制备工艺进行了优化, 获得了制备导电胶的最佳方案。测试结果表明该导电胶能够在60 ℃下4 h内快速固化。在填料质量分数为65%时, 导电胶具有最低的体积电阻率3.6×10-4 Ω·cm; 导电胶的抗剪切强度达到17.6 MPa。在温度为85 ℃、湿度(RH)为85%的环境下经过1000 h老化测试后导电胶电阻率的变化和剪切强度的变化均不超过10%。      

Rheokinetic investigations on the thermal cure of phenol-formaldehyde novolac resins

The curing behavior of commercial phenol-formaldehyde novolac resins with hexamethylenetetramine (HMTA) under non-isothermal and isothermal conditions was followed by dynamic rheological measurements. Changes in parameters of the viscoelastic material such as storage modulus (G′) and complex viscosity (η*) during the cure process were evaluated accurately. The isothermal kinetics reaction was described using a phenomenological equation based on the Malkin and Kulichikhin model. The systematic increase in (E_a) values showed that the increase in bulk viscosity during the reaction alters the resin curing process by reducing diffusion of molecules and hindering network growth. Higher HMTA contents lead to faster growing rates in the crosslinking network, hence there are more crosslinked bonds after a shorter period of reaction. This fact implies that active species need more energy to form new crosslinking bonds, changing the curing reaction mechanism.     

Residual stress development during the composite patch bonding process: measurement and modeling

This paper presents an experimental technique for monitoring residual stress development throughout the composite patch repair curing process. Using this technique, process-induced strains and specimen warpage during a number of different cure cycles were measured for a simulated single-sided composite patch repair of an aluminum substrate. Models for adhesive cure rate and glass transition behavior of the patch adhesive resin (FM 300-1K) were combined with a simple bi-metallic strip model to predict specimen warpage and strain behavior during cure. Model predictions were compared with experimental measurements and were used to assist in the development of optimized cure cycles. Using these optimized cycles, it was found that it was possible to achieve significant (>20%) reductions in patch warpage and at the same time, minimize processing time and obtain a high final adhesive degree of cure. Experimental observations suggest that an improved patch model incorporating adhesive viscoelastic behavior during cure would assist in achieving additional process improvements.     

Interface Stress-Induced Degradation of the Performance of Electrically Conductive Adhesives

Electrically conductive adhesives are of increasing importance as a powerful alternative to eutectic bonding. In the use of electrically conductive adhesives in soldering applications, a lack of conductivity of the adhesive bond between surface mounted devices (SMD) and the printed circuit board was frequently observed. This lack of conductivity caused failure of the unit because of an unacceptable series resistivity in the circuit. A failure analysis proved that the resistance of the contact between the adhesive and device depends on the stress situation in the bonded interface induced by the shrinkage of the adhesive during curing. Under stress, the formation of a resin segregation layer of low conductivity results. The outer shape of the electrical component as well as the SMD assembly process has strong influence on the electrical performance.     

双马来酰亚胺-聚醚砜复相树脂固化与相行为

采用非等温DSC研究了双马来酰亚胺-聚醚砜（BMI-PES）复相树脂体系的固化行为和固化动力学,根据Kissinger方程计算BMI-PES复相树脂固化的表观活化能和指前因子,利用Crane方程计算反应级数,得到反应动力学方程,进行了实验固化度与理论固化度对比验证,通过SEM研究BMI-PES复相树脂微观相结构随固化温度和时间的演化规律。树脂固化行为显示:BMI-PES复相树脂固化反应存在自催化现象,PES参与了BMI固化;随着升温速率增大,BMI-PES复相树脂固化特征温度均向高温移动,但固化热焓基本不变;随着PES添加量增多,反应速率增大,BMI-PES复相树脂固化热焓降低,而峰值固化温度无变化。固化动力学研究表明:随着PES添加量增多,BMI-PES复相树脂固化表观活化能增大,但指前因子和反应级数无变化,固化为一级反应;BMI-PES树脂在200℃固化时,反应前期固化度实验数据与理论值吻合度很高。SEM结果表明,BMI-PES树脂经180℃固化处理后产生了相反转结构。      

E 51环氧树脂固化反应中动力学转变

采用等温DSC法研究了E-51环氧树脂与4, 4’-二氨基二苯基砜(DDS)体系的固化反应过程, 并与已有固化模型拟合得到了170、180、190、200 ℃下的等温固化反应动力学的参数, 根据决定系数R2确定了适合的固化模型。研究表明: 当固化度小于40%时属于Kamal自催化模型; 当固化度大于40%时属于n级固化模型, 即固化反应由Kamal自催化反应向n级反应转变。      

潜伏性环氧树脂/胺基酰亚胺体系的固化动力学

分别采用Kamal模型和Kissinger模型研究了E-51/胺基酰亚胺潜伏性固化体系的等温和非等温固化动力学,讨论了该体系的固化反应机理。结果表明,由这两种动力学模型得到的固化动力学参数基本相近,E-51/胺基酰亚胺体系固化反应起始阶段的活化能较高,约为124 kJ/mol～131 kJ/mol。该体系的固化反应包含n级反应和自催化反应。胺基酰亚胺热分解反应是E-51/胺基酰亚胺体系固化反应的控制步骤。     

Smart cure cycles for the adhesive joint of composite structures at cryogenic temperatures

Adhesive joints are employed for composite structures used at the cryogenic temperatures such as LNG (liquefied natural gas) insulating tanks and satellite structures. The strength of the adhesive joints at the cryogenic temperatures is influenced by the property variation of adhesive and the thermal residual stress generated due to the large temperature difference (ΔT) from the adhesive bonding process to the operating temperature. Therefore, in this work, the strength and thermal residual stress of the epoxy adhesive at cryogenic temperatures were measured with respect to cure cycle. Also, the cure cycles composed of gradual heating, rapid cooling and reheating steps were applied to the adhesive joints to reduce the thermal residual stress in the adhesive joints with short curing time. Finally, a smart cure method was developed to improve the adhesive joint strength and to reduce the cure time for the composite sandwich structures at cryogenic temperatures.     

An analytical model for B-stage joining and co-curing of carbon fibre epoxy composites

The objective of this paper was to develop cure kinetic models to describe the B-stage curing and co-curing assembly of carbon fibre reinforced thermosetting polymer (CFRP) composites. Starting from the analytical model, temperature cycles and experimental procedures are developed to join a B-stage CFRP part to a reinforcing B-stage CFRP patch for local reinforcement. Our results show that by using the analytical model, one may precisely describe the cure reaction and join the composites without any additional adhesive. The co-cured composites were successfully manufactured with stable fibre volume fractions and glass transition temperatures between the two sub-components. Additionally, merits of the process, such as modifying reinforcing areas locally, or formation of net shape detail are discussed.