Ambuj D. Sagar

Starch fragmentation during extrusion processing

Abstract This study focuses on the molecular fragmentation of starch as a result of extrusion-based thermomechanical processing. Gel permeation chromatography-light scattering and bulk intrinsic viscosity measurements were used for the macromolecular characterization. The data indicate that the extrusion processing of starch results in a reduction in its molecular weight. Such a fragmentation of the starch polymer could be attributed, at least partly, to debranching of the molecules.

Irradiation‐modification of starch‐containing thermoplastic blends. I. Modification of properties and microstructure

Irradiation-modification of the blends of various starches with a synthetic polymer [poly(ethylene-co-vinyl alcohol)] was carried out using an electron beam. The effect of irradiation on neat starches was studies using gel permeation chromatography. Changes in the thermal and mechanical properties of the blends, as well as in their microstructures, were also evaluated. The data indicate, consistent with other reports in literature, that starch molecules fragment under the effect of ionizing radiation, while the EVOH is relatively unaffected. These substantial (mainly physical) modifications to the starch molecules manifest themselves in changes in the thermal behavior of the blends. Furthermore, the mechanical properties of filaments obtained from molten irradiated pellets were quite different from those of control filaments, at least for some starches. Micrographic examination of some blends indicated a correspondence between a modification in the microstructure of the filaments and a change in their mechanical properties. It seems likely that the enhanced mobility of the fragmented starch molecules in the melt is responsible for these changes in the microstructure and concomitantly, the mechanical properties of the blend. Such an irradiation-based physical modification of starch may be of use in tailoring the properties of commercial blends of starches with synthetic thermoplastics.

Automobiles and global warming: Alternative fuels and other options for carbon dioxide emissions reduction

This paper discusses the feasibility and desirability of the large scale production and use of alternative fuels as a strategy to mitigate carbon dioxide emissions from motor vehicles. Improving vehicle efficiency and changing to more efficient modes of passenger transportation are also examined. Widespread application of some potential alternative fuels could possibly reduce the greenhouse and other emissions from the transport sector, but technologies related to their production and use at a commercial level still need significant innovation. Commercial application of these fuels would also involve a number of other significant environmental and social impacts that should not be ignored.

Irradiation-modification of starch-containing thermoplastic blends. II. Rheological studies

This study involves an examination of the changes in the rheological behavior (specifically the non-Newtonian viscosity) of blends of various starches with a synthetic polymer (polyethylene-co-vinyl alcohol) as a result of irradiation-modification. The results are generally consistent with fact that starch degrades substantially upon irradiation, while the synthetic polymer is relatively unaffected. However, the high-amylose starch-containing blends are less sensitive to irradiation than we would expect ; this is attributed to possible interactions between the linear molecules from the high-amylose starch and the synthetic polymer.

Pest control strategies: Concerns, issues, and options

Abstract At the present time, the use of chemicals is by far the most widespread strategy to control populations of agricultural pests as well as vectors of human disease. A close examination of such an approach reveals many problems. Over the long term, the effectiveness of a chemical in controlling pests is severely attenuated. Furthermore, extensive pesticide use results in adverse human health and environmental effects. Integrated pest management (IPM) is discussed as an alternative, ecologically sound strategy for curtailing pest problems. It is also suggested that IPM be strongly promoted at a global level, but especially in third-world countries where pesticide-related problems often take on acute dimensions. The possible roles of international agencies in this context is also addressed briefly.

Estimation of inter-detector lag in multi-detection gel permeation chromatography

Abstract An analytical method for estimating the lag between concentration and molecular-mass-sensitive detectors has been developed. This method is simple in its approach and does not require any knowledge about the molecular mass distribution of the polymer sample used in the analysis. The elution behavior results obtained using the lag value from this method correlate well with those obtained from the traditional gel permeation chromatography peak calibration method.