SynopsisThe adhesion of poly(ethy1ene terephthalate) (PET) to rubber in tire composites was significantly improved by exposure of the PET to "low-temperature" gas plasmas. Rubber composites built using a singledip resorcinol-formaldehyde-latex (RFL) adhesive and plasma-treated PET reinforcement were studied. The effects of treatment conditions on this adhesion improvement were examined. The improvement was insensitive to nature of the gas, exposure time, power level, and pressure within the operating limits of the plasma generator. Fiber finish on filaments being treated was detrimental to the adhesion improvement; however, an overcoating of treated filaments with finish was not detrimental. The effects of tire building operations on this adhesion improvement of treated P E T were examined. The improvement was found over a wide range of adhesives, adhesive-curing conditions, rubber compositions, and bonding testing conditions.

synopsisAmorphous unoriented poly(ethy1ene terephthalate) was crystallized a t 25°C by various organic liquids. The crystallinity induced in the amorphous polymer was measured by differential scanning calorimetry and infrared spectroscopy. The ability of liquids to interact with and induce crystallinity in the amorphous polymer was classified on the basis of their solubility parameters. Measurements of the density of liquidcrystallized 0.8-mil films of poly(ethy1ene terephthalate) indicated the presence of extensive internal voids in the semicrystalline polymer matrix. Comparison of differential scanning calorimetric thermograms and infrared spectra of heatccrystallized and liquidCrystallized polymer indicated significant differences in the polymer morphologies induced by the two crystallization processes.

The antimony catalyst content of poly(ethylene terephthalate) has an appreciable effect on the tendency of the polymer to crystallize upon cooling from the melt. Nucleation density increases significantly as antimony catalyst concentration increases. The crystallization tendency of the polymer at a given molecular weight correlates strongly with both the antimony content and the diethylene glycol comonomer content. The behavioral patterns of nucleation by catalyst remnants are similar in polyester prepared from terephthalic acid or dimethyl terephthalate. The antimony catalyst is deposited in the polyester matrix in a form suitable to nucleate quiescent crystallization. The differences in tendency to crystallize that correlate with catalyst and diethylene glycol comonomer content are reflected in the crystallinity of injection molded samples.

synopsisThe dynamic loss energy measurements for characterizing adhesion using Vibron DDV-I1 have been applied to the tire cord-rubber composite system, and the relationships between these dynamic measurements and static adhesion test (H-block pull test and strip peeling test) were also investigated. Tested samples were the commercial nylon 66 tire cord and poly(ethy1ene terephthalate) tire cord with two adhesive systems. The d e gree of adhesion (adhesion factor) was obtained as the energy dissipation at the tire cordto-rubber interface as measured by dynamic testing. It was shown that energy dissipation is increased at the filamentrmatrix interface when the composite is subjected to continuous cyclic loading if a condition of poor adhesion exists. The test was based upon the separation of the total energy dissipation in a composite under cyclic loading into a portion associated with viscous properties of the constituent materials and a second portion resulting from the lack of perfect bonding in the interfacial regions. The strip peeling measurement of adhesion exhibited an approximately linear correlation with the dynamic loss energy measurement of adhesion. The dynamic energy loss measurement is suggested as a potential source of information on the rheological characteristics of the interfacial region of bonding.