Plasticization of cellulose diacetate by graft copolymerization of ε‐caprolactone and lactic acid

Abstract

Graft copolymerization of ε‐caprolactone (CL) and lactic acid (LA) onto cellulose diacetate (CDA) at the residual hydroxyl positions was conducted to obtain thermoplastic CDA. The effects of the reaction temperature and time and the CL/LA molar ratio in the feed on the progress of the graft copolymerization were investigated. The molecular weight of CDA was increased by this graft copolymerization. The oxycaproyl and lactyl molar substitutions (MS_CL and MS_LA, respectively) in grafted CDA (g‐CDA) were determined through ¹H‐NMR spectral analysis. These MS values were controllable by changing the reaction conditions adequately. The flow temperature and melt viscosity of g‐CDA decreased with an increase in the total substitution of MS_CL and MS_LA, and transparent polymer sheets could be obtained from the resulting g‐CDA by hot pressing at around 200°C without adding any plasticizer. The mechanical properties of the molded g‐CDA samples varied widely, depending on the different combinations of the MS_CL and MS_LA values; the g‐CDA sheets became elastic when the MS_CL was larger than the MS_LA, and their tensile strengths were enhanced as the MS_LA was increased. It was thus found that CDA was successfully plasticized by this graft copolymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2621–2628, 2002