Adhesive Blends Research Articles

Thermal analysis characterization of a commercial thermoplastic/thermoset adhesive

DSC, TGA and DMA thermal analysis techniques are used to characterize a complex adhesive blend. The chemical and thermomechanical property development shown to follow a two-stage process. Beneficial synergy between these analysis tools is demonstrated in this study.

Optical adhesives based on blends of methylmethacrylate-co-glycidylmethacrylate copolymer and bisphenol-A diglycidyl ether

In pursuit of nonbirefringent optical adhesives, various copolymers of methylmethacrylate and glycidylmethacrylate (MMA-co-GMA) were synthesized and subsequently blended with bisphenol-A diglycidyl ether (EPON-828) epoxy prepolymer using acetone as a common solvent. Miscibility and optical properties of these adhesive blends were investigated by means of differential scanning calorimetry (DSC), dielectric thermal analysis (DETA), and refractive index measurements. The increasing trend of the single glass transition temperatures of the copolymers as well as of their refractive indices with increasing MMA content suggests that these copolymers are probably of a random type. The adhesive blends, after curing with trimellitic anhydride (TMA), remained transparent, suggestive of a single-phase character. The complete miscibility of the adhesive blends made the refractive indices to be adjustable by simply varying the ratio of MMA-co-GMA copolymer in the blends. In addition, the positive and negative dielectric anisotropies (intrinsic birefringence) of the constituent molecules can be compensated fully in their cured states, thereby yielding significant reduction in the net birefringence in the blends of 50–80 wt % copolymer and a zero-birefringent optical adhesive at 60 wt %. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1911–1917, 1997

Development of Non-Birefrmgent Optical Adhesives

The birefringence compensation technique1 has been employed through polymer blending for the development of non-birefringent optical adhesives. It has been found that trimellitic anhydride(TMA)-cured polymethylmethacylate(PMMA)/Epoxy EPON-828) as a possible system resulted in phase separation due to polymerization2. To circumvent the problem of polymerization-induced phase separation, a copolymer system comprised of methylmethacrylate(MMA) and glycidylmethacrylate(GMA) was synthesiztd3. The MMA-co-GMA copolymer was subsequently blended with EPON-828, then cured thermally with TMA. The cured blend films showed single glass transition at all compositions and optical transparency suggestive of miscible character. These optical adhesive blends showed zero birefringence or zero optical retardation at compositions between 60–70-wt% copolymer. The zero Birefringence afforded by the compensation of the intrinsic birefringence of the constituent polymer chains may be attributed to the complete miscibility of the blends in the cured state.

Compressive Mechanical Properties of the Nomex/Thermoset Honeycomb Cores

Nomex/Thermoset honeycombs with hexagonal cell shape were fabricated by impregnating the Nomex T412 paper using a resol, a resol modified with 20 phr of a bismaleimide and a resol modified with 20 phr of a poly(vinyl butyral) (PVB) respectively. The density of the honeycombs ranged from 2.0 to 4.0 lb/ft3. To fabricate the Nomex/Thermoset honeycombs with dimensions of 300×300×50 mm, an expansion procedure was employed. An epoxy-based adhesive system comprising 4,4′-tetraglycidyl diaminodiphenyl methane 35%, diaminodiphenyl sulfone 12%, the resol 35% and the PVB 18% was formulated and used to bond honeycomb cell nodes before expanding stacked ribbons. The adhesive blend was formulated to obtain a good honeycomb shape by reducing spreading of the resin during cure. The cure behaviors of the adhesive and the resol were investigated by differential scanning calorimetry. The compressive mechanical properties of the honeycombs were investigated and the effects of the impregnating thermoset resin systems on the compressive mechanical properties of the honeycombs were analyzed. The effect of the compressive mechanical properties of the honeycombs comprising pure resol on cure conditions was investigated. © 1997 John Wiley & Sons, Ltd.

The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance

AbstractThe effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot‐melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer‐modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot‐melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock‐containing systems. © 1995 John Wiley & Sons, Inc.

Interaction of nylon polymers with epoxy resins in adhesive blends

Blends of nylon-epoxy resins are used as adhesives. It is found by swelling tests that the epoxy resin crosslinks the nylon. By the failure of poly-N,N'-diisobutylhexamethyleneadipamide to cure and by the failure of prereactions of the nylon with phenyl glycidyl ether, it is shown that the epoxy resin reacts with the nylon through the amide hydrogen. The effect of the epoxy cure on increasing the brittle strength and on decreasing the yield strength of the nylon is discussed in terms of stresses in the adhesive joint.