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Blends of linear and long - chain branched poly (l - lactide)s with high melt strength and fast crystallization rate / Liangyan Wang in Industrial & engineering chemistry research, Vol. 51 N° 30 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 30 (Août 2012) . - pp. 10088-10099 Titre : Blends of linear and long - chain branched poly (l - lactide)s with high melt strength and fast crystallization rate Type de document : texte imprimé Auteurs : Liangyan Wang, Auteur ; Xiabin Jing, Auteur ; Haibo Cheng, Auteur Année de publication : 2012 Article en page(s) : pp. 10088-10099 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Crystallization  Strength Résumé : The long-chain branched polylactides (LCB-PLAs) prepared by coupling the hydroryl-teaninated two-arm (linear) and triarm PLA prepolymers of identical arm length with hexamethylenediacianate (HDI) were used to improve the melt rheological and crystallization properties of linear polylactide resin, PLA 4032D from NatureWorks. The blends containing LCB-PLA displayed higher zero shear viscosities, more significant shear shinning, more melt elasticity, and much longer relaxation times together with significant strain hardening in elongational deformation. Tg, Tm and crystallinity (Xc) of linear PLA remained virtually unaffected, but the crystallization rate increased obviously, since the branch points of LCB-PLAs could play a role of nucleating agent. High melt strength, fast crystallization, and favorable miscibility improved the foaming ability of the linear/ LCB-PLA blends, substantially. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26201423 [article] Blends of linear and long - chain branched poly (l - lactide)s with high melt strength and fast crystallization rate [texte imprimé] / Liangyan Wang, Auteur ; Xiabin Jing, Auteur ; Haibo Cheng, Auteur . - 2012 . - pp. 10088-10099. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 30 (Août 2012) . - pp. 10088-10099 Mots-clés : Crystallization  Strength Résumé : The long-chain branched polylactides (LCB-PLAs) prepared by coupling the hydroryl-teaninated two-arm (linear) and triarm PLA prepolymers of identical arm length with hexamethylenediacianate (HDI) were used to improve the melt rheological and crystallization properties of linear polylactide resin, PLA 4032D from NatureWorks. The blends containing LCB-PLA displayed higher zero shear viscosities, more significant shear shinning, more melt elasticity, and much longer relaxation times together with significant strain hardening in elongational deformation. Tg, Tm and crystallinity (Xc) of linear PLA remained virtually unaffected, but the crystallization rate increased obviously, since the branch points of LCB-PLAs could play a role of nucleating agent. High melt strength, fast crystallization, and favorable miscibility improved the foaming ability of the linear/ LCB-PLA blends, substantially. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26201423

Rheology and crystallization of long - chain branched poly (l - lactide)s with controlled branch length / Liangyan Wang in Industrial & engineering chemistry research, Vol. 51 N° 33 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 33 (Août 2012) . - pp. 10731-10741 Titre : Rheology and crystallization of long - chain branched poly (l - lactide)s with controlled branch length Type de document : texte imprimé Auteurs : Liangyan Wang, Auteur ; Xiabin Jing, Auteur ; Haibo Cheng, Auteur Année de publication : 2012 Article en page(s) : pp. 10731-10741 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Crystallization Résumé : A series of long-chain branched poly(L-lactide)s (LCB-PLAs) with controlled branch length were prepared by a simple and efficient method through a combination of ring-opening polymerization (ROP) of L-lactide and a coupling reaction between the terminal OH groups of the PLA prepolymers and the NCO groups of HDI. The influences of reaction conditions on the synthesis of the LCB-PLAs were investigated, and the structures of the resultant LCB-PLAs were characterized by 1H NMR spectroscopy and SEC-MALLS. By adjusting the degree of polymerization and the composition of the prepolymers, LCB-PLAs with different branch densities and molecular weights between branch points were obtained. The effect of macromolecular chain branching on the rheology and crystallization of PLA was also investigated. The LCB structure contributed to the enhancement of the zero-shear viscosity, complex viscosity, storage modulus, melt strength, and strain hardening under elongational flow. Thermal behavior indicated that the branch structure resulted in a short nucleation induction period and more rapid crystallization, which can be a guarantee of high-strength foams. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26286447 [article] Rheology and crystallization of long - chain branched poly (l - lactide)s with controlled branch length [texte imprimé] / Liangyan Wang, Auteur ; Xiabin Jing, Auteur ; Haibo Cheng, Auteur . - 2012 . - pp. 10731-10741. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 33 (Août 2012) . - pp. 10731-10741 Mots-clés : Crystallization Résumé : A series of long-chain branched poly(L-lactide)s (LCB-PLAs) with controlled branch length were prepared by a simple and efficient method through a combination of ring-opening polymerization (ROP) of L-lactide and a coupling reaction between the terminal OH groups of the PLA prepolymers and the NCO groups of HDI. The influences of reaction conditions on the synthesis of the LCB-PLAs were investigated, and the structures of the resultant LCB-PLAs were characterized by 1H NMR spectroscopy and SEC-MALLS. By adjusting the degree of polymerization and the composition of the prepolymers, LCB-PLAs with different branch densities and molecular weights between branch points were obtained. The effect of macromolecular chain branching on the rheology and crystallization of PLA was also investigated. The LCB structure contributed to the enhancement of the zero-shear viscosity, complex viscosity, storage modulus, melt strength, and strain hardening under elongational flow. Thermal behavior indicated that the branch structure resulted in a short nucleation induction period and more rapid crystallization, which can be a guarantee of high-strength foams. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26286447