Iranian polymer journal
Volume:17 Issue: 9, 2008

Simultaneous measurement of effective thermal conductivity (λe) and effective thermal diffusivity (χe) of three samples of polypyrrole doped with metals Ni and Co in different percentage: polypyrrole doped with 100% Co (S1), polypyrrole doped with 50-50% Ni and Co (S2), and polypyrrole doped with 100% Ni (S3) have been made using transient plane source (TPS) technique. The amorphous nature of polypyrrole composites was confirmed by XRD studies. Characterization through SEM and EDX gives the information of surface morphology and elemental analysis of samples. From surface morphology it is found that surface is not smooth and contains macro-granular structure. EDX results confirm the presence of metal present in the samples. Thermal transport properties i.e., effective thermal conductivity (λe) and effective thermal diffusivity (χe) were measured at normal pressure from room temperature to 170ºC. From these investigations, it has been found that both λe and χe increase to maximum up to 110º and then a constant value is attained with further increase of temperature i.e., 170ºC. The values of λe and χe of sample S3 doped with 100% Ni is higher as compared to sample S1 (Co 100%) and sample S2 (Ni, Co 50-50%). This result has been explained on the basis of bonding of cobalt and nickel with polypyrrole matrix during the polymerization and higher values for S3 are attributed to the more metallic nature of Ni.

Due to different polarity and structure between the thermoplastic and elastomeric phases, most thermoplastic elastomers are incompatible. Poor interfacial adhesion and high interfacial tension between rubber and thermoplastic phases are main reasons for incompatibility of these systems. The blends of polypropylene (PP)/ethylene propylene diene monomer (EPDM) containing 20% EPDM may be compatibilized with maleic anhydride grafted PP (PP-g-MAH) and maleic anhydride grafted EPDM (EPDM-g-MAH) ranging from 0 to 6 phr. The dynamic rheological behaviour of the blends in presence of compatibilizer and applying dynamic vulcanization were studied using parallel plate rheometric mechanical spectrometer (RMS) at 190°C. The Cole- Cole and van Gurp-Palmen plots for all samples were plotted to make correlation between rheology and the obtained morphology of the blends. It was found that the complex viscosity (η*) of the dynamic vulcanized blends levelled up with increase of compatibilizer concentration while for un-vulcanized blends it was levelled off for the same ratio of PP/EPDM. Storage modulus of compatibilized samples showed two relaxations shoulder at high concentration of compatibilizer which at low frequencies is attributed to interfacial relaxation and at high frequencies is related to EPDM droplets. There was no considerable difference among intersection frequencies (ωc) for un-vulcanized samples which means compatibilizer is more effective in combination with dynamic vulcanization. Morphological study showed that the size of dispersed phase decreased with combination of dynamic vulcanization and compatibilization.

Vanadium (IV) oxyacetylacetonate or vanadium (IV) oxyacetylacetonate-2,2,6,6- tetramethylpiperidinyl-1-oxy (TEMPO) complexes activated with diethyl aluminium bromide as catalysts were employed for the polymerization of methyl methacrylate in benzene at 40ºC. The catalysts were compared based on various parameters such as Al/V ratio, reaction time, catalyst, monomer concentration and temperature on the rate of polymerization and yield. The rate of polymerization increased linearly with increasing monomer concentration with first order dependence. Polymer yield was maximum when the Al/V ratios were 2.2 and 1.4 and the activation energies were 8.9 and 9.1 kcal.mol-1, respectively for the catalysts VO(acac)2 / AlEt2Br and VO(acac)2 / AlEt2Br / TEMPO. Inclusion of TEMPO to the catalyst system VO(acac)2 / AlEt2Br shows increased catalytic activity. The catalyst systems have resulted in syndiotactic rich PMMA’s having Mn values in the range of 12000–23000. PMMA’s of narrow molecular weight distributions in the range of 1.2-1.7 could be obtained under mild conditions in benzene solvent at 40ºC.