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This article reports the results of studies on the degradation of the blend of low-density polyethylene (LDPE) with a starch based prodegradant additive, named commercially as Polystarch plus H and abbreviated as PSH, under natural weather, underground soil aging, and sea water aging in Dhahran, Saudi Arabia. The work includes measurements of tensile properties, thermal behavior, and scanning electron microscopic (SEM) studies on the unaged and aged LOPE and the LDPE/PSH blend having 25% (w/w) of PSH. Results of the preliminary experiments showed that changes in properties are not prominent at lower loadings of PSH. In the case of the blend, incorporation of the additive PSH caused a reduction in elongation at break, which is accentuated under aging. The effectiveness of the prodegradant additive in the degradation behavior follows the order, natural aging > underground soil aging > sea water aging. It is believed that the prodegradant additive is effective in chain scission in sunlight under natural weathering conditions, in contrast to underground soil aging and sea water. POLYM. ENG. SCI., 53:2389-2397, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION Plastics have become an indispensable item in our daily life. Their specific properties such as light weight, easy processability, low cost, good resistance to chemicals and microorganisms, nonbiodegradable nature, [...]

Compatibility of starch/polyvinyl alcohol (PVA) blends, prepared by solution cast method, is dependent on the blend composition. Crystallinity of the blend, as measured by X-ray diffraction (XRD) and differential scanning calorimeter (DSC), decreases with increase in starch content. Thermogravimetric analysis (TGA) shows that the broadness in the peak width at the degradation region increases with increase in starch content in the starch/PVA blend. Dynamic mechanical thermal analysis (DMTA) reveal that the broadness of the relaxation peaks is due to the partial compatibility of the glycerol plasticized starch/PVA blends. The tensile property decreases with increase in starch content and the 30/70 starch/PVA blend shows maximum ductility in respect to both the percentage of elongation and energy at break. POLYM. ENG. SCI., 52:2167-2172, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Over the last several decades, the consumption of plastic materials has been continuously increasing due to the ease of processing, low cost, high durability, and a wide range in [...]

This article reports the rheological behavior of nanocomposites of isotactic polypropylene with both unmodified multiwall carbon nanotubes (CNTs) and phenol and 1-octadecanol (C18) functionalized CNT (f-CNT) at 0.1, 0.25, 1.0, and 5.0 wt% of the nanofillers. The incorporation of CNT at low loadings of 0.1 and 0.25 wt% decreases the storage and loss modulus and complex viscosity of the system, especially for the case of using f-CNT. Out of the two types of functionalizations, C18 functionalization registers the lowest modulus and viscosity and displays processing aid behavior at 0.1 wt% loading, which is believed to be due to the disruption of the polymer entanglements. As the nanofiller loading increases to 1 wt%, the disruption of polymer entanglements effect is balanced by the hydrodynamic effect and subsequently neat polypropylene (PP), and the filled PP systems show similar modulus and complex viscosity. As the nanofiller loading increases further to 5 wt%, the hydrodynamic effect becomes the dominating factor, and the modulus and the complex viscosity of the nanofilled system become greater than that of neat PR Results suggest that the 0.1 wt% loading of C18 f-CNT could be a useful processing aid additive for improving polypropylene processability. POLYM. ENG. SCI., 52:1868-1873, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Ever since their discovery in 1990s, carbon nanotubes (CNTs) have generated great interest particularly as fillers for preparation of a variety of high-performance polymer nanocomposites due to their ability [...]

Fluororubber vulcanizate powder (FVP) obtained from fluororubber based on tetrafluoroethylene/propylene/vinylidene fluoride terpolymer by mechanical grinding exists in a highly aggregated chain-like structure. X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies show that there are no chemical changes on the rubber surface following mechanical grinding of the fluororubber vulcanizate after heat aging at 200°C for 10 days. The incorporation of FVP as a filler in the fluororubber compound results in a marginal increase of Mooney viscosity, Mooney scorch time and shear viscosity. While tensile strength, modulus and hardness marginally increase on addition of FVP into the fluororubber compound, tear strength decreases. Rheometric studies show that FVP alone is susceptible to further crosslinking in the presence of a curing agent. Dynamic mechanical spectra reveal that the glass to rubber transition temperature shifts higher by the addition of FVP into the fluororubber compound. At omic force microscopy (AFM) images show uniform dispersion of FVP particles into the rubber matrix., INTRODUCTION Recycling of waste rubber is important for both economic and environmental reasons. A potentially attractive method is to grind waste vulcanized rubber and use the resultant powder as a [...]

The silicone rubber vulcanizate powder (SVP) obtained from silicone rubber by mechanical grinding exists in a highly aggregated state. The particle size distribution of SVP is broad, ranging from 2 μm to 110 μm with an average particle size of 33 μm. X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) Spectroscopy studies show that there is no chemical change on the rubber surface following mechanical grinding of the heat-aged (200°C/ 10 days) silicone rubber vulcanizate. Addition of SVP in silicone rubber increases the Mooney viscosity, Mooney scorch time, shear viscosity and activation energy for viscous flow. Measurement of curing characteristics reveals that incorporation of SVP into the virgin silicone rubber causes an increase in minimum torque, but marginal decrease in maximum torque and rate constant of curing. However, the activation energy of curing shows an increasing trend with increasing loading of SVP. Expectedly, incorporation of SVP does not alter the glass-rubb er transition and cold crystallization temperatures of silicone rubber, as observed in the dynamic mechanical spectra. It is further observed that on incorporation of even a high loading of SVP (i.e., 60 phr), the tensile and tear strength of the silicone rubber are decreased by only about 20%, and modulus dropped by 15%, while the hardness, tension set and hysteresis loss undergo marginal changes and compression stress-relaxation is not significantly changed. Atomic Force Microscopy studies reveal that incorporation of SVP into silicone rubber does not cause significant changes in the surface morphology., INTRODUCTION Disposal of worn-out rubber products and factory wastes is a global problem for both environmental and economic reasons. A potentially attractive method Is to grind vulcanized rubber and use [...]

The melt flow properties of unfilled and filled brominated isobutylene-co-paramethylstyrene (BIMS) were measured by means of a capillary viscometer at three different temperatures (90°C, 110°C and 130°C) and four different shear rates (61, 122, 245 and 306 [s.sup.-1]). The effect of addition of EPDM rubber on melt flow properties of unfilled BIMS was also studied. Evaluation of the processability was done by measuring the extrudate roughness (ER) of the extrudates obtained from the MPT. The viscosity of the systems decreased with the shear rate, indicating their pseudoplastic or shear thinning nature. As expected, the viscosity of BIMS increased with the addition of fillers and decreased with the addition of oil. For the neat systems, viscosity increased with the addition of EPDM, and the blends showed a positive deviation, indicating interdiffusion of the polymer chains across the phase boundaries. The activation energy of the filled systems at constant filler loading increased with i ncreasing filler surface area (N330 > N550 > N774, each at 30 phr loading), and filler loading (50 > 30 > 10 phr, for N330) and decreased with the addition of oil (2.5 > 5.0 > 7.5 phr, for system containing 30 phr of N330). The silica filled system showed a higher activation energy and ER than the carbon black-filled systems. With addition of N330 and N550 carbon blacks to BIMS, the extrudate roughness (ER) decreased, whereas it increased with the addition of N774 carbon black. With an increase in filler loading, ER initially increased and then decreased as compared to the neat system. For the filled systems, ER initially decreased up to 5 phr of oil, beyond which it increased., INTRODUCTION One of the major concerns of the rubber industry is the processing behavior of an elastomer during processing operations such as mixing, extrusion, calendering and molding. The flow behavior [...]

Milling behavior of brominated isobutylene-co-paramethylstyrene (BIMS), and its blends with ethylene propylene diene rubber (EPDM), with special reference to the effect of addition of different fillers, filler loadings and processing oil, was investigated over a range of temperatures in a drop mill operation. The critical nip gap (CNG), at which a front to back roll transition (F-B transition) occurs, was also measured. Addition of different fillers reduced the value of the critical nip gap and the mill band formation indices for DIMS as compared to the gum polymer, indicating a decrease in the tendency to go to the back roll. The systems containing reinforcing fillers showed a lower value of the critical nip gap, as compared to systems containing low or non-reinforcing fillers. For different filled blends of DIMS and EPDM, the ONG decreased on increasing the EPDM content, indicating a decrease in the tendency for a F-B transition. The CNG decreased on increasing the N330 carbon black-loading, while it increa sed with the addition of processing oil. The results were explained in terms of rubber to metal adhesion and viscosity of the polymers., A.K. Bhowmick (*) INTRODUCTION Milling is an important operation in the processing of compounded rubbers. The great advantage of two-roll mills is that it represents an open process to which [...]

The optical attributes of PrAg in paramagnetic phase at normal pressure and ferromagnetic phase at normal and high pressure were examined. It was found that exchange interaction plays an important role on its optical characteristics, thereby influencing the ferromagnetic nature of Ag. On the other hand, the magnitude and position of peaks in the optical spectrum are affected by the oscillator strength or transition probability.

A study was conducted to analyze the transport features of HCL doped polyaniline (PANI) and polyaniline-methyl cellulose dispersion at low temperature to 1.8K and in magnetic fields up to 8T. A CHN analyzer was utilized to determine the weight percentage of PANI. Results showed that the temperature dependence of resistivity was weaker than reported values for PANI protonated with HCl.

A study was conducted to investigate electrical transport in paratoluene sulfonate-doped polypyrrole films. Magnetoconductance was examined using 3D electron-electron interaction and weak electron localization theory. Conductivity in the insulating region was correlated with the variable hopping theory. Results indicated that the inelastic scattering length is consistent with the theory of inelastic scattering.

The electromagnetic interference shielding effectiveness and return loss of short carbon fiber filled polychloroprene rubber composites of varying sample thickness and fiber aspect ratio were studied in the frequency range of 8 to 12 GHz (X-band). It was observed that composites prepared by 'cement mixed' method having high fiber aspect ratio (L/D = 100) show higher shielding effectiveness and lower return loss than the composites prepared by 'mill mixed' method with low fiber aspect ratio (L/D = 25). This indicates that loss due to absorption increases with increasing fiber aspect ratio. Similar effect has also been observed with increasing sample thickness.

A study of carbon fiber-filled polychloroprene rubber (neoprene) contrasts mill mixing with cement method, which increases fiber aspect ratio and thus, conductivity. Vulcanization is compared with thermovulcanization, wherein temperature affects volume resistivity. There is also a 'hysteresis loop' lasting up to 30 phr loading. Present afterwards are inter-fiber contacts that help electrical performance due to increased concentration. Further, increased temperature causes a break in the linearity of the current-voltage plots. The Hall effect reveals that increased fiber loading decreases mobility while increasing the concentration of carriers, mostly electrons.