Renewable polyester compositions having a low density

摘要

A thermoplastic composition that contains a rigid renewable polyester and has a voided structure and low density is provided. To achieve such a structure, the renewable polyester is blended with a polymeric toughening additive to form a precursor material in which the toughening additive can be dispersed as discrete physical domains within a continuous matrix of the renewable polyester. The precursor material is thereafter stretched or drawn at a temperature below the glass transition temperature of the polyester (i.e., “cold drawn”). This creates a network of voids located adjacent to the discrete domains, which as a result of their proximal location, can form a bridge between the boundaries of the voids and act as internal structural “hinges” that help stabilize the network and increase its ability to dissipate energy. The present inventors have also discovered that the voids can be distributed in a substantially homogeneous fashion throughout the composition.

主权项

1. A thermoplastic composition comprising
a rigid polyester constituting 80 wt. % or more of the thermoplastic composition having a glass transition temperature of from 30° C. to 100° C., a polymeric toughening additive, and an interphase modifier comprising a silicone, silicone-polyether copolymer, alkylene glycol, alkane diol, amine oxide, fatty acid ester, or a combination thereof in an amount of from 0.1 wt. % to 15 wt. % based on the weight of the polyester, wherein the thermoplastic composition has a morphology in which a plurality of discrete primary domains and voids are dispersed within a continuous phase, the domains containing the polymeric toughening additive and the continuous phase containing the polyester, wherein the voids contain a combination of micro-voids having a dimension of about 1 micrometer or more and nano-voids having a dimension of less than about 1 micrometer, wherein the thermoplastic composition has a density of about 1.4 grams per cubic centimeter or less, and wherein the ratio of the glass transition temperature of the thermoplastic composition to the glass transition temperature of the polyester is from about 0.7 to about 1.3.