Sustainable Cross-linked Polymers

Abstract

Plastics, which are composed of long molecules called polymers, are useful materials whose versatility, low cost, and durability has caused their annual production to surpass that of most other man-made materials. The manufacturing of plastics is almost exclusively dependent on petrochemicals derived from nonrenewable fossil fuels and virtually all major plastics today are so durable that they persist long past their functional lifetime, resulting in a staggering exponential increase in plastic waste generation. Unfortunately, only a small fraction of this waste is collected for value recovery (e.g., recycling and incineration) while the majority ends up stagnating in landfills or polluting the environment. Certain important subsets of plastics, such as those with cross-linked molecular architectures, cannot be recycled at all. Therefore, the sourcing and end-of-life landscape for plastics is unsustainable in the long term. One avenue of research which aims to provide workable solutions to these problems is the development of new, competitive materials which can be sourced from annually renewable feedstocks (i.e., biomass) and/or have more sustainable end-of-life fates (e.g., improved capacity for recycling or degradation). In this thesis, four projects are presented investigating various aspects of sustainable cross-linked plastics. Chapter 1 provides a summary of plastic use and sustainable plastic development, with emphasis on cross-linked polymers. Chapter 2 investigates a component of biodegradability for a commercial mulch film which cross- links under UV light. Chapters 3 and 4 describe the development of sustainable cross- linked elastomers, and Chapter 5 comprises a study of potentially recyclable polymers with dynamic urethane cross-links.