Volume 19, Issue 3

A new ortho-hydroxy-aryl-phosphonate additive was used to improve the flame resistance of an epoxy/anhydride system. Thermal, rheological, L.O.l. and SEM experiments were carried out to show that the P-additive acts not only as a flame retardant but also as a curing agent.

In this paper we carried out the crosslinking of the tetraglycidyl-4,4′- diaminodiphenyl methane epoxy resin by using a reactive poly(arylene ether sulphone) as curing agent. Differential scanning calorimetry was used to derive the kinetic parameters of the reactions involved in the cure process and to evaluate the extent of the reaction as a function of time by measuring the total (ΔH r ) and the residual heat(ΔH resid ) of the resin at different curing times. A comparatively slower reaction was found to take place when the resin was cured with the poly(arylene ether sulphone) that when it was cured with the conventional curing agent 4,4′-diaminodiphenyl sulphone.

The phenomenon of hole pressure occurs whenever a polymeric or viscoelastic liquid flows over a depression in a conduit wall. Numerical simulations undertaken for the flow of an aqueous polyacrylamide melt passing over a transverse slot arc considered here. The fluid model used for this study is a White-Metzner constitutive equation describing the non-Newtonian behavior of the melt. The results were computed by an elastic-viscous split-stress finite clement method (EVSS-FEM). a mixed finite clement method incorporating the non-consistent streamline upwind scheme. For verification, the numerical algorithm was first applied to compute the corresponding flow of the upper-convected Maxwell fluid model, a special case of the Whitc-Metzner model characterized by constant viscosity and relation time. The resulting hole pressure (P h ) was evaluated for various Deborah numbers (De) and compared with the analytical prediction derived from the Higashitani-Pritchard (HP) theory. The agreement was found to be satisfactory for creeping flow in the low De range, for which the HP theory is valid. Subsequently, the hole pressure of this flow problem was predicted. The streamlines and pressure distribution along the channel walls arc also presented. Furthermore, the effects of fluid elasticity, shear thinning, the exponent in the viscosity function and the relaxation-time function, and slot geometry on the hole pressure were investigated.

Some thermodynamic quantities were obtained for the interactions of poly (4-tert-butylstyrene) with alcohols, ketones, acetates, aromatics and alkanes by the inverse gas chromatography method in the temperature range of 343-463 K. The specific retention volumes (Vg°), the adsorption enthalpy of probes (ΔH 2 ), the partial molar free energy of sorption (ΔG 1 S ), the enthalpy of sorption (ΔH 1 S ), the entropy of sorption (ΔS 1 S ), the weight fraction activity coefficients of solute probes at infinite dilution (Ω 1 ∞ ), and the Flory- Huggins thermodynamic interaction parameters (χ ∞ 12 ) between polymer and solvents are given. The partial molar free energy (ΔG 1 ∞ , the partial molar heat of mixing (ΔH 1 ∞ at infinite dilution and the solubility parameters of the polymer (δ 2 ) were calculated. The solubility parameter of poly (4-tert-butyl- styrene) was determined from either the slope or intercept as 7.25 (cal/cm 3 ) 0,5 and 7.00 (cal/cm 3 ) 0,5 at 180°C, respectively.

Tires mounted on vehicles stored in the open air are subject to various forms of deterioration as a result of heat aging, oxidation and ozone attack, and must be protected by the use of chemical antidegradants, and if possible from direct sunlight. The effects of such deterioration on the properties of sidewall rubbers have been studied on tires of various ages taken from army stores, and certain conclusions have been drawn.