No abstract

No abstract

No abstract

Inverse gas chromatographic experiments (IGC) with a styrenebutadiene rubber (SBR) as the stationary phase have been conducted at temperatures on either side of the polymer TB and at carrier gas flow rates up to 60 mL/min. Above the Tg retention volumes decrease with rising carrier flow rate, attaining equilibrium values at high flow rates. The equilibrium values are interpreted as being due solely to surface interactions, calculations having shown that under these carrier gas flow rates dwell times of probe molecules at the polymer surface are too short to permit diffusion into the bulk. In this manner it is possible to use IGC for surface characterizations of polymers above their T,. The chromatographic data also allow the maximum size of vapor molecules able to diffuse into the polymer bulk to be estimated.

The present work was done to improve the impact property of isotactic polypropylene (PP), especially at low temperatures, by incorporating ethylene propylene diene monomers (EPDM). This was done by ensuring compatibility between the two polymers with phase modifiers polyethylene grafted with maleic anhydride (PE-g-MA) and initiator dicumyl peroxide (DCP). In addition, attempts were also made to understand the fundamentals of impact toughening as well as fracture toughness, and to correlate the results with that of morphological evidences obtained from scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. Varying the ratios of all blend composition, mechanical properties were studied. It was observed that as the rubber fraction increased, the impact property as well as fracture toughness increased. All these tests also showed promising results when PE-g-MA was added, leading to more improvement in all the mechanical properties including increase in crystallite size. It had shown plasticization effect on the compositions, which could be further confirmed by differential scanning calorimetry (DSC) compared to the uncompatibilized ones. But when DCP was added, it behaved like an initiator which directly reacted with the PP matrix, decreasing the molecular weight of the blend with decreasing size of the crystallites.

SynopsisEffects of E / P ratio of the EPDM rubber on the flow behavior and morphology of the crosslinkable polyethylene and EPDM blends have been studied as a function of shear rate and processing temperature. High-E/P-ratio EPDM rubber exhibits high viscosities within the temperature range studied but the extrudate swell is higher for the low E/P ratio EPDM. Shear modulus, stored elastic energy and flow activation energy are higher for high E/P ratio EPDM but relaxation time is higher for low E/P ratio EPDM. At a particular blend ratio these rheological parameters show a change in their pattern. This point of change in pattern occurs at a lower level of EPDM having a high E/P ratio; this suggests an early phase inversion as corroborated by the SEM studies. Melt fracture occurs to a larger extent for the low E/P ratio EPDM in its blends with XLPE.

No abstract

No abstract