Renewable polyester film having a low modulus and high tensile elongation

摘要

A film that is formed from a thermoplastic composition is provided. The thermoplastic composition contains a rigid renewable polyester and a polymeric toughening additive. The toughening additive can be dispersed as discrete physical domains within a continuous matrix of the renewable polyester. An increase in deformation force and elongational strain causes debonding to occur in the renewable polyester matrix at those areas located adjacent to the discrete domains. This can result in the formation of a plurality of voids adjacent to the discrete domains that can help to dissipate energy under load and increase tensile elongation. To even further increase the ability of the film to dissipate energy in this manner, the present inventors have discovered that an interphase modifier may be employed that reduces the degree of friction between the toughening additive and renewable polyester and thus reduces the stiffness (tensile modulus) of the film.

主权项

1. A film comprising a thermoplastic composition, wherein the thermoplastic composition comprises:
at least one rigid renewable polyester having a glass transition temperature of about 0° C. or more; from about 1 wt. % to about 30 wt. % of at least one polymeric toughening additive based on the weight of the renewable polyester; from about 0.5 wt. % to about 15 wt. % of at least one interphase modifier based on the weight of the renewable polyester, wherein the interphase modifier facilitates debonding from the renewable polyester; and a polyepoxide modifier having a number average molecular weight of from about 7,500 grams per mole to about 250,000 grams per mole; wherein the thermoplastic composition has a morphology in which a plurality of discrete primary domains are dispersed within a continuous phase, the discrete primary domains containing the polymeric toughening additive and the continuous phase containing the renewable polyester, wherein a plurality of substantially homogeneously distributed voids are located adjacent to the discrete primary domains; wherein the film exhibits a tensile modulus in the machine direction and cross-machine direction of about 2500 Megapascals or less, a tensile elongation at break in the machine direction of about 10% or more, and a tensile elongation at break in the cross-machine direction of about 15% or more, wherein the tensile modulus and tensile elongation at break are determined at 23° C. according to ASTM D638-10, wherein the ratio of the glass transition temperature of the thermoplastic composition to the glass transition temperature of the renewable polyester is from about 0.7 to about 1.3.