不同形貌的银对导电胶性能的影响

银的形貌、银表面的润滑剂、树脂基体的成分、固化过程等都会影响导电胶的性能。其中，银的形貌是一个关键的因素。论文研究了在相同条件不同形貌的银对导电胶性能的影响。将银片、银球和银线用戊二酸处理以消除其他因素的影响，然后这些银粒子被用作导电填料与环氧树脂混合制备导电胶。研究了不同形貌银粉制备的导电胶热降解性能、导电性能、机械性能及贮存稳定性。结果表明在相同条件下银线制备的导电胶具有最低电阻率和渗流阈值、最好的机械性能、以及较好的贮存稳定性，银片制备的导电胶导电性能和贮存稳定性比用银球制备的导电胶好，但机械性能比用银球制备的导电胶差。     

Polymer-Solid Interface Connectivity and Adhesion: Design of a Bio-Based Pressure Sensitive Adhesive

Adhesion at polymer-solid interfaces was explored for a new bio-based pressure sensitive adhesive (PSA) in terms of sticker groups, φ_X, on the polymer phase, receptor groups, φ_Y, on the solid surface, and the bond strength of the sticker-receptor X-Y acid-base interaction, χ. The polymer-solid interface restructuring models of Gong and Lee et al. were extended with new percolation models of entanglements and interface strength to determine the optimal sticker group concentration, φ?_X. For the general case where φ_Y and χ are constant, it is predicted that when φ_X < φ?_X, that the critical peel energy behaves as G_1c ～ φ_X/φ?_X and the locus of failure is adhesive between the polymer and the solid. However, when φ_X > φ?_X, failure occurs cohesively in a polymer-polymer interface adjacent to the solid and the strength decreases as G_1c ～ φ?_X/φ_X. The switch from adhesive to cohesive failure can be understood in terms of the changes in the chain conformations of the adhered chains and their decreasing interpenetration, X_i, with the bulk chains, via X_i ～ 1/r, where r = χφ_Xφ_Y. The optimal value of φ_X which maximizes the adhesion and determines the mode of failure is given by φ?_X ≈ 0.129/C_∝, and for typical values of the characteristic ratio C_∝ in the range 7–20, φ?_X ≈ 1% mole fraction, corresponding to about 2 sticker groups per entanglement molecular weight, M_e. This result was verified for a bio-based PSA synthesized from an acrylated high oleic fatty acid, which was copolymerized with maleic anhydride as the sticker group. The observed behavior is counterintuitive to the current wisdom for the effect of acid-based interactions on adhesion, where the strength is expected to increase with the number of X-Y contacts. The surprisingly low value of φ?_X ≈ 1% sticker groups which maximizes the adhesion strength can now be readily calculated using the percolation model of entanglements and fracture.     

Power feed synthesis of pressure-sensitive latex adhesives

Latex particles with the same core composition of poly(MMA-co-ALMA) and different shell compositions of poly(BA-co-AA) were prepared by semibatch emulsion polymerization using ‘power feed’ monomer and chain transfer agent addition methods in the shell layers. The seed stage involved formation of seed particles of 111 nm in diameter with a batch process. After that, two growth stages formed the final particle diameter, d_z = 300 nm measured by dynamic light scattering. The gel content and the molecular parameters of the polymer were determined. The adhesive properties including loop tack, peel force and shear resistance were measured according to the FINAT test methods No. 9, 1 and 8. An evaluation was also made for the relationship between pressure-sensitive properties and molecular parameters. Introducing power feed to semibatch emulsion polymerization had no significant effect on the latex preparations and could improve the final conversion and the colloidal stability. The observed particles were grown without significant secondary nucleation. The power feed methods had no effect on the glass transfer temperature (T_g) of the shell layer also. Emulsion polymerization conducted by positive power feed resulted in the formation of longer primary polymer chains at the beginning than that conducted by negative power feed and standard uniform feed, which caused a very high gel fraction. As pressure-sensitive adhesives prepared by using the positive power feed had the highest gel content and strongest core–shell interaction, they exhibited the highest shear resistance, but the lowest tack and peel force.     

Effect of Blend Ratio and Testing Rate on the Adhesion Properties of Epoxidized Natural Rubber (ENR 25)/Styrene–Butadiene Rubber (SBR) Blend Adhesive

The effect of rubber blend ratio and testing rate on the adhesion properties of epoxidized natural rubber (ENR 25)/styrene–butadiene rubber (SBR) blend adhesive were studied using 40 parts per hundred parts of rubber (phr) of coumarone-indene resin as the tackifying resin. Toluene and poly(ethylene terephthalate) (PET) film were used as the solvent and substrate, respectively. A SHEEN hand coater was used to coat the adhesive on the PET substrate at 30, 60, 90, and 120 µm coating thickness. Viscosity was determined by a Brookfield viscometer whereas loop tack, peel strength, and shear strength were measured by a Llyod Adhesion Tester at various testing rates from 10 to 60 cm/min. Results show that viscosity increases gradually with % ENR 25. However, loop tack, peel strength, and shear strength of adhesives indicate a maximum value at 40% ENR 25, after which the adhesion properties decreases with further increase in % ENR 25. This observation is attributed to the varying degree of wettability which culminates at an optimum value of 40% ENR 25 blend ratio. In all cases, the adhesion properties increase with increasing coating thickness and rate of testing.     

Physico‐chemical,thermal, and mechanical approaches for the characterization of solubilized and solid state chitosans

This study was conducted on the both solid and solubilized chitosans to propose an approach for the physico‐chemical, thermal and mechanical characterizations of this polysaccharide. The polysaccharide used was a 90% deacetylated chitosan having a molecular weight of 98.4 kDa. The flow property of chitosan solutions was evaluated revealing a shear‐thinning behavior. The thermal characterization was carried out by studying heat specific capacity, glass transition temperature, and thermal conductivity on chitosan dried specimens (solid state). Their T_g were measured by DSC and confirmed by DMA at 102 and 122°C depending on concentrations of initial chitosan solutions. The mechanical characterization was conducted by analyzing Young modulus, tensile strength, and elongation at break of chitosan specimens. They exhibited a higher elongation at break and a lower tensile strength when made from high concentrated chitosan solution (9% w/v). Differences in mechanical behavior of specimens were explained by differences of crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41257.     

Oxirane Cleavage Kinetics of Epoxidized Soybean Oil by Water and UV‐Polymerized Resin Adhesion Properties

Di‐hydroxylated soybean oil (DSO), a biobased polyol synthesized from epoxidized soybean oil (ESO) could be used to formulate resins for adhesives; however, current DSO synthesis requires harsh reaction conditions that significantly increase both cost and waste generation. In this paper, we investigate the kinetics of oxirane cleavage in ESO to DSO by water and elucidate the role of different process parameters in the reaction rate and optimization of reaction conditions. Our kinetic study showed that ESO oxirane cleavage was a first‐order reaction and that the ESO oxirane cleavage rate was greatly influenced by tetrahydrofuran (THF)/ESO ratio, H₂O/ESO ratio, catalyst content, and temperature. Optimized reaction parameters were THF/ESO of 0.5, H₂O/ESO of 0.25, catalyst content of 1.5 %, and reaction time of 3 h at 25 °C. DSO with hydroxyl value of 242 mg KOH/g was obtained under these conditions. We also characterized the structure, thermal properties, adhesion performance, and viscoelasticity of UV‐polymerized resins based on this DSO. The resin tape exhibited peel adhesion strength of 3.6 N/in., which is comparable to some commercial tapes measured under similar conditions.     

Preparation and properties of environment-friendly acrylic latex laminating adhesives applied in plastic/plastic composite films

Acrylic latex laminating adhesives (ALLAs) were successfully prepared via a monomer-starved seeded semi-continuous emulsion polymerization with butyl acrylate (BA), methyl methacrylate (MMA), styrene (St), acrylamide (Am), and methacrylate glycidyl ether (GMA) as monomers. Impacts of GMA on the final latex, the dried latex films and the adhesive properties of ALLAs were investigated, respectively. The results indicated that the increase of GMA contents in the pre-emulsion feed has no apparent effect on the final latex average particle size and size distribution, while the gel contents, glass transition temperature (T_g) and water contact angle of the ALLAs gradually increased, and the molecular weight (M_n, M_w) obviously increased. Additionally, as the amount of GMA increased from 0 to 10?wt%, the maximum peel strength of the composite films reached 3.72 N/15mm with 5?wt% GMA contents. When heated to 65?°C, the peel strength of the composite films with 5?wt% of GMA can still maintain an acceptable peel strength (2.51 N/15mm) for application, showing excellent adhesive performance and heat resistance properties.     

阵列波导器件封装用UV胶粘接力学性能分析

以阵列光纤与波导芯片的粘接力学性能为研究对象,首先理论分析UV固化胶的不同布胶方式下封装器件承受的最大拉伸力、剪切力和弯曲力,然后运用有限元软件对接头受力所产生的应力分布进行仿真分析。通过对模型的计算和仿真结果的对比分析,在经济性、可靠性和可操作性等原则下,提出了在耦合端面涂胶的优化布胶方式。     

用均匀设计和正交设计研究水性PU压敏胶配方

为制得环保、交联型水性聚氨酯压敏胶,以IPDI、聚醚多元醇、DMPA、TMP为主要原料进行乳液聚合.用红外光谱表征合成材料的结构,测定其初粘性、持粘性、180°剥离强度.运用均匀设计筛选配方,并用正交图表分析较优值,通过正交试验确定了压敏胶的最佳配方.当n-NCO/n聚醚-OH=2.5:1,TMP/N220的-OH物质的量比为1:3时,压敏胶综合性能最好,初粘性为13号钢球,持粘性为23.1 h,180°剥离强度为20.14 N/20 mm.     

耐高温有机胶粘剂研究进展

对国内外耐高温有机胶粘剂进行了综述。对环氧树脂、酚醛树脂、聚氨酯、聚酰亚胺、有机硅和氰酸酯等耐高温有机胶粘剂的性能和应用进行了全面讨论,并对其今后的发展趋势进行了展望。