The influence of miscibility of an acrylic PSA and several tackifier resin systems upon PSA performance was investigated. When the acrylic copolymer and the resins were blended in various proportions, three types of mixing state were found: miscible system, partially miscible system and immiscible system. In the case of miscible systems, PSA performance (tack, peel strength and shear resistance) depended upon the viscoelastic properties of the PSA. In the case of completely immiscible systems, the above PSA performance depended primarily upon the viscoelastic properties of a continuous matrix phase, and the separated resin phase acted as a kind of filler. In the case of partially miscible systems, the PSA performance changed discontinuously at the resin concentration where phase separation occurred. It suggests that the phase structure of a PSA greatly influences the PSA's performance. 相似文献
The frictional forces between pressure sensitive adhesives (PSAs), including rosin tackifier resin, and a probe tip were measured with scanning probe microscopy (SPM). A peak that appeared in the scanning rate-frictional force curve shifted to a lower scanning rate with decrease in temperature. The frictional force reflects rheological behavior of the PSA. In the case of the miscible system, the tendency of a peak to shift to a lower scanning rate was observed with increase in tackifier content; however, in the case of the immiscible system, no remarkable shift was observed. The frictional force is influenced by viscoelastic properties of the PSA, which systematically changed with miscibility. The high-scanning rate resulted in the interfacial failure on the surface, while the low-scanning rate resulted in the cohesion failure. 相似文献
The frictional forces between pressure sensitive adhesives (PSAs) and a probe tip were measured with a scanning probe microscopy (SPM). A peak appeared in the scanning rate-frictional force curve shifted to a lower scanning rate with decreasing temperature. In the case of the miscible system of isoprene matrix of SIS base polymer, the tendency of a peak to shift to a lower scanning rate was observed with increasing tackifier content; however, in the case of the immiscible system of styrene domain of SIS base polymer, no remarkable shift was observed. The frictional force is influenced by viscoelastic properties of the PSA which systematically changed with miscibility. In this study, it is aimed to clarify the correlation between the observation of phase structure and the behavior of surface rheology by using two kinds of tackifiers that have different miscibility with the polyisoprene phase or the polystyrene phase of SIS triblock copolymer. 相似文献
The effect of varying interaction parameters on the phase diagrams of ternary polymer blends was explored by simulating spinodals through use of the Flory-Huggins lattice theory. Results indicate that miscibility is favored for the case of ternary mixtures of marginally miscible or marginally immiscible pairs where all pair interactions are nearly athermal. Miscibility is restricted for asymmetric ternary blends when one of the polymer pairs is either strongly miscible or strongly immiscible. For symmetric blends of partially immiscible pairs, both two-phase and three-phase miscibility gaps are predicted. 相似文献
Summary: In this paper, immiscible, partially miscible and miscible blends of polyamide 66 (PA66) and high density polyethylene (HDPE) were obtained by changing compatibilizer concentrations. Mechanical and tribological properties of materials were tested. It was found that the addition of compatibilizer greatly improved the mechanical properties of PA66/HDPE blends. The wear of PA66/HDPE blends was strongly affected by the phase structure. The best blend for lower friction coefficient and higher wear resistance was the blend with a miscible structure, which significantly improved the tribological properties of PA66 and HDPE. SEM investigations on the worn surface and the steel counterface indicated that, for the immiscible and partially miscible blend systems, the dispersed HDPE particles were pulled out from the worn surfaces during sliding because of the poor adhesion between HDPE and PA66, while this was not observed in the miscible blend system.
SEM micrograph of the worn surface formed by PA66/HDPE blend without HDPE‐g‐MAH. 相似文献
The dynamic mechanical properties and the adhesive strengths of Epikote 828 and Epikote 828-ATBN blend systems were investigated. The ATBN blend systems were proved to be completely incompatible with the dynamic mechanical measurement and also fitted well with Takayanagi's model which was designed for completely incompatible two-phase systems. The epoxy resin had a nonreacted part when cured at room temperature. The blending of ATBN reduced the nonreacted part of the epoxy resin, and made contributions to the adhesive strengths. In the case of tensile test of crosslap specimens using aluminium as adherends, the adhesive strengths of ATBN blend systems were almost 1.5-fold of those of epoxy resin without blending of ATBN. As for wood adherends, the maximum of the adhesive strengths was found at 60°C for epoxy resin without blending of ATBN, and at 0°C for ATBN blend systems. The facts meant that there were mutual interactions between the adhesive strengths and the viscoelastic behavior of the adhesive polymers in the two-phase systems as observed in completely miscible polymer blends. There was not pronounced distinction between epoxy resins without blending of ATBN and ATBN blend system, as to the shear adhesive strengths. 相似文献
In a study of pressure-sensitive adhesives prepared from mixtures of natural rubber and three different tackifying resins, it was shown that a tackifying resin may form either one- or two-phase systems with natural rubber. Measurements of the viscoelastic properties of the adhesives show that the effect of tackifying resins is to modify the viscoelastic properties so that the adhesive performance in bonding and unbonding is improved. It is suggested that a two-phase system is not necessary for good tack, and a theory based on a two-phase system cannot adequately explain the rate dependence of tack tests. Tack measured by the probe test is shown to be dependent upon a balance between the viscoelastic properties and the transition temperature of the adhesives. This theory is used to explain the effect of contact time, withdrawal speed, and resin softening point on the tack of adhesives. 相似文献
In this report, we review and discuss the results of our recent studies on the characteristics of microphase separation behavior and interphase stabilization for high performance polymer blends. The blends investigated include crystalline/crystalline polymers, crystalline/amorphous polymers, liquid crystalline polymer/thermoplastics, and amorphous/amorphous thermoplastics or thermosetting systems. Most of the blends are either immiscible or partially miscible, and are thermodynamically unstable or meta-stable systems. The macro-properties of these blends are controlled by many factors such as the miscibility, phase morphology and structure, crystallinity, kinetics of crystallization or phase separation processing, and interfacial adhesion of the components. Among these, the microphase and interfacial structures are the most significant factors influencing the ultimate properties of the blends. In order to obtain relatively stable blends, formation of semi-IPN in either the bulk or interphase, and/or the occurrence of crosslinking, transesterification and physical entanglement in the interfacial region will be profitable to the stabilization of the blending systems.The project supported by FORD and NSFC No. 09415312 相似文献
The relation of morphology to the linear viscoelastic properties for polymer blends consisting of an inert polypropylene and an elastomeric dispersed phase, made of two miscible copolymers, EVA and EMA, was investigated. The rheological properties of the elastomeric phase were modified by crosslinking in presence of an organometallic catalyst. The activation energy for the transesterification reaction taking place between EVA and EMA has been determined by following the increases of the complex viscosity with time and temperature. The Palierne model has been used to describe the linear viscoelastic behavior of the blends, and to estimate the interfacial tension between the immiscible components. The model was shown to describe relatively well the linear viscoelastic properties of reactive and nonreactive blends containing 30% or less elastomer. In parallel, the morphology of reactive and nonreactive blends (i.e. without catalyst in the elastomeric phase), before and after rheological experiments, has been determined using scanning electron microscopy. The size of the dispersed elastomeric particles for reactive blends prepared using an internal mixer was found to be, in most cases, much smaller than that for nonreactive blends. 相似文献