Novel conductive adhesives for surface mount applications

Electrically conductive adhesives (ECAs) have been explored as a tin/lead (Sn/Pb) solder alternative for attaching encapsulated surface mount components on rigid and flexible printed circuits. However, limited practical use of conductive adhesives in surface mount applications is found because of the limitations and concerns of current commercial ECAs. One critical limitation is the significant increase of joint resistance with Sn/Pb finished components under 85°C/85% relative humidity (RH) aging. Conductive adhesives with stable joint resistance are especially desirable. In this study, a novel conductive adhesive system that is based on epoxy resins has been developed. Conductive adhesives from this system show very stable joint resistance with Sn/Pb‐finished components during 85°C/85% RH aging. One ECA selected from this system has been tested here and compared with two popular commercial surface mount conductive adhesives. ECA properties studied included cure profile, glass transition temperature (T_g), bulk resistivity, moisture absorption, die shear adhesion strength, and shift of joint resistance with Sn/Pb metallization under 85°C/85% RH aging. It was found that, compared to the commercial conductive adhesives, our in‐house conductive adhesive had higher T_g, comparable bulk resistivity, lower moisture absorption, comparable adhesion strength, and most importantly, much more stable joint resistance. Therefore, this conductive adhesive system should have better performance for surface mount applications than current commercial surface mount conductive adhesives. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 399–406, 1999     

氰酸酯树脂及其胶黏剂的研究概况

氰酸酯胶黏剂以其优异的介电性能、耐湿热性能和耐高温性能在国外被广泛用于航天、航空和电子领域,尤其是将其用于雷达天线罩、微波武器、隐身材料等先进武器的制造。从以下三个方面对氰酸酯树脂及其胶黏剂的研究做了简要的概述:(1)氰酸酯树脂的特性、种类、聚合反应机理、产品及应用;(2)四种增韧氰酸酯树脂的方法,着重介绍了橡胶弹性体、热塑性树脂、热固性树脂(环氧、双马来酰亚胺等)的改性效果;(3)国外氰酸酯胶黏剂的最新进展和系列化产品的性能介绍。     

Plywood adhesives derived from distillers' dried grains with solubles (DDGS) incorporating 2‐hydroxyethyl acrylate

Distillers' dried grains with solubles (DDGS), a byproduct of corn ethanol production, are currently used primarily as an alternative animal feed thanks to its high protein content and low cost. Previous research has developed a protein‐based bioadhesive from DDGS. However, the adhesive does not possess the appropriate properties to compete with synthetic adhesives and other bio‐based adhesives. In this study, a bioadhesive is prepared from DDGS and hydroxyethyl acrylate (HEA) is incorporated to improve the bonding strength and moisture resistance. The greatest increase in lap‐shear strength was observed in the adhesive containing 50% of the acrylic resin. Water resistance was absent from the original DDGS adhesive, but established upon the inclusion of HEA. HEA was found to self‐polymerize under the hot‐pressing conditions and form a co‐continuous phase with the protein adhesive derived from DDGS. The strength of the adhesives was adequate for bonding plywood panels. More work must be done to further enhance the performance of the adhesives for wider applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45689.     

Plant Polyphenol-Inspired Crosslinking Strategy toward High Bonding Strength and Mildew Resistance for Soy Protein Adhesives

Soybean protein adhesives are environmentally friendly biomass-based aldehyde-free adhesives that have good economic value for the wood industry; however, it remains challenging to produce soybean protein adhesives with excellent water resistance, toughness, and mildew resistance through a simple modification method. In this work, inspired by plant polyphenols, a novel crosslinked soybean meal adhesive (SMPT) is obtained using a facile economic method. Polyamidoamine-epichlorohydrin (PAE) and tannic acid (TA) are combined with a soybean meal matrix to form a tough co-crosslinked network through strong intermolecular forces (covalent bonds, ionic bonds, and hydrogen bonds) in adhesive system. The results show that the wet bonding strength of SMPT adhesives for plywood is 134.1% higher than the unmodified soybean meal adhesive. The adhesion properties met the standard requirements for interior-use plywood. And the compact cross-linking network structure is accelerated the greater energy dissipation, which improves the toughness of adhesive. Moreover, cationic azetidinium groups in PAE and phenol hydroxyl groups in TA synergistically not only exhibit the good antibacterial activities but also improve mildew resistance for SMPT adhesives. This facile strategy provides an economic sustainable method to prepare high-performance environmentally friendly wood adhesives.     

Effects of the aluminum filler content on moisture diffusion into epoxy adhesives in distilled water and sea water

Epoxies are the most common of high‐performance structural adhesives, especially in automotive and aircraft manufacturing. In a variety of industrial applications, epoxy adhesives are required to have enhanced thermal conductivity. The normal method of changing this property is to add to the epoxy a filler of higher conductivity than the continuous phase. Although the improvement in the thermal properties of adhesives by the addition of metal fillers is obvious, their influence on water sorption characteristics of adhesives is not clear. It was the objective of this study to shed light on these aspects, which are lacking in the literature. The emphasis was placed on determining the moisture sorption behavior of aluminum‐powder‐filled epoxy adhesives under complete immersion in distilled water and sea water. Moisture diffusion tests show that the addition of aluminum filler into epoxy decreases the total amount of water intake at saturation in both fluids. However, there appears to be no significant effect of the aluminum filler content on the moisture diffusivity in epoxy adhesive specimens in either distilled water or seawater. It has also been determined that the adhesives adsorb a larger amount of water upon exposure to distilled water than when exposed to seawater, whereas the moisture diffusion rate in the adhesive immersed in seawater is higher than that in distilled water. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1165–1171, 2005     

Hygrothermal Properties of Epoxy Film Adhesives

The hygrothermal response of high performance epoxy film adhesives, in their bulk state, has been characterized over a wide range of temperatures, following exposure to a combination of humidity (95% R.H.) and heat (50°C).

Experimental results have indicated that the testing temperature has a pronounced effect on both tensile modulus and strength of the adhesives, while the effect of moisture content varies with respect to the adhesive type. The moduli of the film adhesives, which have a wide range of glass transition temperatures (T_g), have been related to both moisture level in the adhesive and testing temperature. This has been accomplished by employing a dimensionless temperature, which incorporates the wet and dry T_g and the testing, as well as a reference, temperature. The strength properties have shown a higher degree of scatter using the abovementioned dimensionless temperature.

Scanning electron microscopy of the fracture surfaces have shown a good agreement between the effects of moisture and the mechanical properties. Adhesives which exhibited good moisture resistance, as manifested by the stability in their tensile properties, showed minor changes in their fracture surfaces regardless of moisture conditioning. Distinctively, the effect on strength properties has been correlated with typical moisture-induced fracture mechanisms.     

Preconditioning of epoxy film adhesives for bond strength improvement

The moisture level of two commercial overaged epoxy film adhesives has been controlled by drying under vacuum and/or exposure to humid atmosphere. Shear and peel bond strengths of the conditioned adhesives were evaluated. Predrying of the uncured adhesive under vacuum (3–5 mm Hg) at room temperature is shown to be very effective for bond strength enhancement. Additional humidifying/drying circles show the same effect but some irreversible degradation occurs and only partial improvement of adhesive bond strength is achieved.     

建筑结构胶的耐湿热老化性能研究

耐湿热老化是建筑结构胶的重要性能指标,正在受到越来越多的关注。研究了不同种类的固化剂对改性环氧树脂类建筑结构胶的耐湿热老化性能的影响,同时也对增韧剂、无机填料及助剂等因素进行了探讨。采用自制的固化剂所配制的建筑结构胶耐湿热老化性能优良,完全满足国家标准的要求。     

可控环境下的结构胶粘剂拉伸测试系统

根据结构胶粘剂力学性能测试的特点,提出了一种在可控环境条件下对结构胶粘剂进行拉伸性能测试的自动化测试系统,并详细介绍了该测试系统的设计原理、硬件组成和软件实现,以及环境温度和湿度等的控制方法。最后采用该系统对金属铜丝和一种结构胶粘剂薄膜进行了拉伸测试。测试结果表明,该系统自动化程度高,测试结果准确,具有较高的实际应用价值。     

Hygrothermal Properties of Epoxy Film Adhesives

The hygrothermal response of high performance epoxy film adhesives, in their bulk state, has been characterized over a wide range of temperatures, following exposure to a combination of humidity (95% R.H.) and heat (50°C).

Experimental results have indicated that the testing temperature has a pronounced effect on both tensile modulus and strength of the adhesives, while the effect of moisture content varies with respect to the adhesive type. The moduli of the film adhesives, which have a wide range of glass transition temperatures (T_g ), have been related to both moisture level in the adhesive and testing temperature. This has been accomplished by employing a dimensionless temperature, which incorporates the wet and dry T_g and the testing, as well as a reference, temperature. The strength properties have shown a higher degree of scatter using the abovementioned dimensionless temperature.

Scanning electron microscopy of the fracture surfaces have shown a good agreement between the effects of moisture and the mechanical properties. Adhesives which exhibited good moisture resistance, as manifested by the stability in their tensile properties, showed minor changes in their fracture surfaces regardless of moisture conditioning. Distinctively, the effect on strength properties has been correlated with typical moisture-induced fracture mechanisms.     

建筑结构胶抗冲击剥离性能研究

抗冲击剥离性能作为一项新的强制性指标已列入建筑结构胶国家相关标准之中。从改性环氧树脂类建筑结构胶配方特点出发,研究了环氧树脂种类、填料、增韧剂的添加量、固化剂种类等因素对结构胶抗冲击剥离性能的影响。结果表明,固化剂和增韧剂决定着胶粘剂的抗冲击剥离性能,含填料体系的冲击剥离强度优于不含填料配方,选用合适的环氧树脂和助剂(偶联剂、消泡剂、触变剂等)能得到综合性能良好的建筑结构胶。     

New Developments in Structural Adhesives for the Automotive Industry

Recently developed epoxy paste adhesives, reactive hot melts, adhesive film tape and polyurethane adhesives are presented for structural bonding in the automotive industry. Paste adhesives usually require a precure stage to obtain handling strength of the joints and to guarantee wash-out resistance of the adhesive in the paint baths. This step can be omitted with reactive hot melts and adhesive film tape, which are solid before and after their application. In addition they allow an improved working hygiene. Some mechanical properties of the adhesives are shown such as lap shear strength and peel strength as well as lap shear strength as a function of the bondline thickness. Results of the excellent durability of epoxy one-component pastes, reactive hot melts and adhesive film tape are given from cyclic environmental and salt spray tests.     

热红外伪装涂料的制备研究

以自制的水性粘合剂制备了一种热红外伪装涂料,刷涂于载体上,制得热红外伪装涂层.研究了载体的种类和涂层增质量率对涂层红外发射率的影响,并研究了涂层增质量率对涂层透湿、耐磨和耐有机溶剂等性能的影响.研究结果表明:选用涤纶布为涂层载体,当涂层增质量率为30％时,制备的织物涂层具有良好的透湿性、耐摩擦性和耐有机溶剂腐蚀性,此时涂层的红外发射率为0.61,满足作为热红外伪装织物的基本要求.     

Structure–property relationships in one‐component polyurethane adhesives for wood: Sensitivity to low moisture content

The causes of strength loss of wood joints and their consequent delamination from one‐component polyurethane adhesives used for bonding structural wood when used at a low moisture content was investigated by testing wood joint strength and elongation at rupture at different wood moisture contents and by ¹³C‐NMR spectroscopy and scanning electron microscopy of the hardened bond line. The combination of the relative proportion of the still‐reactive free ? NCO groups on the polyurethane, of the wise choice of degree of polymerization of the resin, and of a slower rate of reaction were the three parameters found to be important in overcoming the problem of poor or no bonding of wood at low to very low moisture contents from one‐component polyurethane adhesives. The results obtained indicated that one‐component polyurethane adhesives that had a combination of a higher proportion of still‐unreacted ? NCO groups, a lower degree of polymerization, and a slower reaction rate were capable of overcoming the problem of the high sensitivity of polyurethane gluing at low to very low wood moisture contents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4181–4192, 2006     

Molecular design and hygrothermal resistance of high-toughness polysiloxane–polyurethane block copolymer composite adhesives

With the development of new energy sources, the demand for aluminum composite films for power batteries is expanding; at the same time, higher requirements have been put forward for aluminum composite films and adhesives. Polyurethane, as the binder of aluminum composite films, strongly affects the performance of aluminum composite films when exposed to moisture and high temperature and can lead to delamination. This thesis prepares a polyurethane and silicone block copolymer composite adhesive by adjusting the ratio of hard and soft polyurethane segments to obtain polyurethane (PU) with excellent flexibility. On the basis of block copolymerization with bis-amino-terminated organosiloxane (ATPS), obtained excellent flexibility, high peel strength, moisture resistance, and heat resistance from a polysiloxane-based polyurethane composite adhesive (PUSR). The properties are also tested using tensile tests and peel strength tests. The test results show that by adjusting the ATPS content, the flexibility and hydrophobicity of the PUSR composite adhesive further improved, with a tensile strength of 36 MPa, an elongation at break of 757%, and bonding performance of 11 N/15 mm. Additionally, the damp heat resistance of 6 N/15 mm, exceeding the international standard of 3 N/15 mm, in the power battery soft package aluminum–plastic film has potential application prospects.     

Combination of lignin polyol–tannin adhesives and polyethylenimine for the preparation of green water‐resistant adhesives

In this study, a green adhesive from renewable lignin and tannin was developed with polyethylenimine (PEI) with a method to improve the water resistance of the lignin/tannin adhesive. Lignin polyols were prepared through the liquefaction of oil‐palm empty fruit bunches. The characteristics of the adhesive samples were compared with those of a commercial phenol–formaldehyde resin. Three plywood specimens bonded with the new adhesive showed a very high tensile strength (63.04 MPa) and were very water resistant. The effect of the solid content of the adhesives on the tensile strength and gel time and various weight ratios of PEI on the tensile strength and water resistance of the plywood specimens were evaluated. Thermal stability tests revealed that the lignin polyol–tannin/PEI adhesives had a high heat resistance (360 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43437.     

An innovative biomass-based wood adhesive generated from peony seed meal: Its preparation and properties

Plant protein-based adhesives, particularly those derived from soybean meal (SM), have been available for various product applications. However, the high cost of SM has limited large-scale manufacturing, despite sufficient production capacity. Peony seed meal (PSM) is abundant in proteins, polysaccharides, and polyphenols, the protein in PSM contains highly hydrophobic amino acids, resulting in low water solubility and water holding capacity. It is worth investigating whether the unique composition of hydrophobic amino acids in PSM protein can enhance the water resistance of PSM-based adhesives. Additionally, the lower price of PSM, which is approximately two-thirds of the cost of SM, makes it a more valuable raw material for adhesives. Herein, we report a simple and practical approach for preparing PSM-based wood adhesives by utilizing the highly active cross-linking agent of polyamidoamine-epichlorohydrin (PAE). The results showed PSM-based adhesives possessed excellent adhesion, especially the adhesive of “PSM-36%”, with the wet bond strength and the aged bond strength reaching 1.60 and 0.83 MPa, respectively, meeting the standards outlined for indoor-use plywood (≥0.98 MPa). Mechanistic studies indicated that the adhesion mechanism of such PSM-based adhesives might involve high solid content, low viscosity, high thermal stability, and the formulation of covalent bonds and hydrogen bond networks.     

混凝土加固改造用建筑结构胶黏剂在中国的发展

综述了混凝土加固改造用建筑结构胶在中国的发展。中科院大连化物所研制开发的JGN型建筑结构胶及加固技术首开我国化学法粘钢加固之先河,已应用于许多工程之中。随后,国内涌现出各种各样的建筑结构胶如碳纤维胶、锚固胶、灌缝胶等满足了土木工程领域不同方面的需要。文章最后展望了建筑结构胶的发展方向。     

耐高温热固性树脂胶粘剂的研究动态

综述了耐高温热固性树脂胶粘剂的发展过程与研究现状,介绍了近年来国内外几种性能优异的热固性树脂胶粘剂,提高其高温性能的一些主要途径和改性方法,并介绍了新型功能填料在树脂中的应用情况,最后对耐高温热固性树脂胶粘剂的总体发展趋势进行了展望。     

聚氨酯结构胶粘剂在电梯镶板上的应用

电梯镶板是典型的品种多、数量少的产品，为满足电梯镶板高效率生产的需要，日本近几年开发出适应电梯轻量化、电梯镶板薄型化要求、粘接性能优异的聚氨酯结构胶粘剂。本文介绍了电梯镶板粘接的必要性、粘接工艺及新开发的聚氨酯结构胶粘剂的特征等。