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Composites of polypropylene with layered Mg-silsesquioxanes show an unusual combination of properties / Guruswamy Kumaraswamy in Industrial & engineering chemistry research, Vol. 47 n°11 (Juin 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3891–3899 Titre : Composites of polypropylene with layered Mg-silsesquioxanes show an unusual combination of properties Type de document : texte imprimé Auteurs : Guruswamy Kumaraswamy, Auteur ; Yogesh S. Deshmukh, Auteur ; Vishal V. Agrawal, Auteur ; Anuya A. Nisal, Auteur Année de publication : 2008 Article en page(s) : p. 3891–3899 Note générale : Bibliogr. p. 3898-3899 Langues : Anglais (eng) Mots-clés : Magnesium  silsesqiuoxanes;  Isotactic  polypropylene;  Melt  compounding Résumé : We report the synthesis of vinyl modified magnesium silsesqiuoxanes (“vinyl clay”), and the formation of their composites with isotactic polypropylene (iPP) by melt compounding. Vinyl clay is a layered compound with a layer thickness of approximately 1 nm. Vinyl clay does not exfoliate in iPP; rather, it disperses to form a network that exhibits a characteristic low frequency solid-like plateau in the elastic modulus in dynamic melt rheological measurements. Strangely, vinyl clay also plasticizes iPP—there is a decrease in the high frequency complex viscosity. The decrease in the complex viscosity is higher at higher frequencies, suggesting the influence of slip at the iPP−vinyl clay interface. The combination of the low frequency elastic plateau and plasticization makes the vinyl clay composite significantly more shear thinning than the matrix iPP. In the solid state, vinyl clay−iPP composites exhibit increased tensile modulus (showing ≈50% increase for a 5% loading), but surprisingly, no corresponding decrease in the elongation at break. Thus, while microstructural characterization indicates that only a small fraction, if any, of the vinyl clay is exfoliated, the enhancement in mechanical properties is similar to that observed for iPP-exfoliated montmorillonite nanocomposites. Our compounding protocol is unable to effectively disperse the clay in the iPP at clay loadings greater than about 7.5%. Therefore, the low frequency plateau in the melt elastic modulus and the solid tensile modulus increase with clay loading until 7.5% but exhibit a nonmonotonic decrease at higher clay loadings. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071658p [article] Composites of polypropylene with layered Mg-silsesquioxanes show an unusual combination of properties [texte imprimé] / Guruswamy Kumaraswamy, Auteur ; Yogesh S. Deshmukh, Auteur ; Vishal V. Agrawal, Auteur ; Anuya A. Nisal, Auteur . - 2008 . - p. 3891–3899. Bibliogr. p. 3898-3899 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3891–3899 Mots-clés : Magnesium  silsesqiuoxanes;  Isotactic  polypropylene;  Melt  compounding Résumé : We report the synthesis of vinyl modified magnesium silsesqiuoxanes (“vinyl clay”), and the formation of their composites with isotactic polypropylene (iPP) by melt compounding. Vinyl clay is a layered compound with a layer thickness of approximately 1 nm. Vinyl clay does not exfoliate in iPP; rather, it disperses to form a network that exhibits a characteristic low frequency solid-like plateau in the elastic modulus in dynamic melt rheological measurements. Strangely, vinyl clay also plasticizes iPP—there is a decrease in the high frequency complex viscosity. The decrease in the complex viscosity is higher at higher frequencies, suggesting the influence of slip at the iPP−vinyl clay interface. The combination of the low frequency elastic plateau and plasticization makes the vinyl clay composite significantly more shear thinning than the matrix iPP. In the solid state, vinyl clay−iPP composites exhibit increased tensile modulus (showing ≈50% increase for a 5% loading), but surprisingly, no corresponding decrease in the elongation at break. Thus, while microstructural characterization indicates that only a small fraction, if any, of the vinyl clay is exfoliated, the enhancement in mechanical properties is similar to that observed for iPP-exfoliated montmorillonite nanocomposites. Our compounding protocol is unable to effectively disperse the clay in the iPP at clay loadings greater than about 7.5%. Therefore, the low frequency plateau in the melt elastic modulus and the solid tensile modulus increase with clay loading until 7.5% but exhibit a nonmonotonic decrease at higher clay loadings. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071658p

Is leasing greener than selling? / Vishal V. Agrawal in Management science, Vol. 58 N° 3 (Mars 2012) 

Public ISBD [article]  in Management science > Vol. 58 N° 3 (Mars 2012) . - pp. 523-533 Titre : Is leasing greener than selling? Type de document : texte imprimé Auteurs : Vishal V. Agrawal, Auteur ; Mark Ferguson, Auteur ; L. Beril Toktay, Auteur Année de publication : 2012 Article en page(s) : pp. 523-533 Note générale : Management Langues : Anglais (eng) Mots-clés : Durable  goods  Sustainable  operations  Green  marketing  Environment  Servicizing Résumé : Based on the proposition that leasing is environmentally superior to selling, some firms have adopted a leasing strategy and others promote their existing leasing programs as environmentally superior to “green” their image. The argument is that because a leasing firm retains ownership of the off-lease units, it has an incentive to remarket them or invest in designing a more durable product, resulting in a lower volume of new production and disposal. However, leasing might be environmentally inferior because of the direct control the firm has over the off-lease products, which may prompt the firm to remove them from the market to avoid cannibalizing the demand for new products. Motivated by these issues, we adopt a life-cycle environmental impact perspective and analytically investigate if leasing can be both more profitable and have a lower total environmental impact. We find that leasing can be environmentally worse despite remarketing all off-lease products and greener than selling despite the mid-life removal of off-lease products. Our analysis also provides insights for environmental groups and entities that use different approaches to improve the environmental performance of business practices. We show that imposing disposal fees or encouraging remanufacturing, under some conditions, can actually lead to higher environmental impact. We also identify when educating consumers to be more environmentally conscious can improve the relative environmental performance of leasing. DEWEY : 658 ISSN : 0025-1909 En ligne : http://mansci.journal.informs.org/content/58/3.toc [article] Is leasing greener than selling? [texte imprimé] / Vishal V. Agrawal, Auteur ; Mark Ferguson, Auteur ; L. Beril Toktay, Auteur . - 2012 . - pp. 523-533. Management Langues : Anglais (eng) in Management science > Vol. 58 N° 3 (Mars 2012) . - pp. 523-533 Mots-clés : Durable  goods  Sustainable  operations  Green  marketing  Environment  Servicizing Résumé : Based on the proposition that leasing is environmentally superior to selling, some firms have adopted a leasing strategy and others promote their existing leasing programs as environmentally superior to “green” their image. The argument is that because a leasing firm retains ownership of the off-lease units, it has an incentive to remarket them or invest in designing a more durable product, resulting in a lower volume of new production and disposal. However, leasing might be environmentally inferior because of the direct control the firm has over the off-lease products, which may prompt the firm to remove them from the market to avoid cannibalizing the demand for new products. Motivated by these issues, we adopt a life-cycle environmental impact perspective and analytically investigate if leasing can be both more profitable and have a lower total environmental impact. We find that leasing can be environmentally worse despite remarketing all off-lease products and greener than selling despite the mid-life removal of off-lease products. Our analysis also provides insights for environmental groups and entities that use different approaches to improve the environmental performance of business practices. We show that imposing disposal fees or encouraging remanufacturing, under some conditions, can actually lead to higher environmental impact. We also identify when educating consumers to be more environmentally conscious can improve the relative environmental performance of leasing. DEWEY : 658 ISSN : 0025-1909 En ligne : http://mansci.journal.informs.org/content/58/3.toc