Controlled-Lifetime Environmentally Degradable Plastics Based on Conventional Polymers

摘要

Macromolecules can be degraded using abiotic processes such that the molecular fragments are biodegradable. In the case of aliphatic polyesters, for example, the first stage in this two-stage process is hydrolysis. The second stage is bioassimilation of the hydrolysis products. In the case of hydrocarbon polymers, such as PE, the first stage is oxidation initiated by heat or UV light or mechanical stress. The oxidized fragments of PE molecules are biodegraded in the second stage by the complex mixtures of microorganisms found in soil, in composting operations, or in landfill sites. All of our data show that the TDPA~(TM) additive packages can accelerate the initial degradation of many hydrocarbon polymers, to the point where they become biodegradable, in timescales which are acceptable for many practical applications, ranging from packaging to landfill cover. Control of the rates of the two stages, in the case of various commercial PE's, is achieved through a balance of appropriate additives. In this way, end-use performance can be altered to fit specific markets without altering the normal degradation pathways and products. Independent testing has shown that full, direct food contact is permitted for both degradable and compostable EPI TDPA~(TM) film products. The additive formulations can provide, if required, sensitivity to near-UV light as well as to heat. The essential feature of the additive packages developed by EPI is control of the lifetime of the material.