Recyclable Polyester Composition with Epoxide Chain Extender
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Solution Overview
Problem
Current recycling methods for polyesters, such as PET, result in low-quality recycled materials due to molecular weight reduction and branching/crosslinking issues during thermal processing, leading to compromised mechanical properties and high energy costs.
Innovation Solution
A recyclable polyester composition incorporating a sterically hindered epoxide or polyfunctional epoxide compound, along with a capping agent, to control chain extension and prevent branching/crosslinking during thermal processing, maintaining molecular weight and viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical recycling through high temperature extrusion is used to convert recycled PET flakes into pellets, then the recycling process is economically viable and environmentally friendly, but the molecular weight of PET is reduced and mechanical properties are compromised
Solution Approach 1:
The patent applies preliminary action by adding the epoxide compound and capping agent to the polyester composition before thermal processing. This pre-positioning of reactive components allows the chain extension and protective capting reactions to occur during the necessary high-temperature extrusion process, thereby maintaining molecular weight and mechanical properties while enabling economically viable mechanical recycling
Solution Approach 2:
The epoxide compound serves as an intermediary that mediates between the thermal processing conditions and the polyester chains. It reacts with end groups to extend chains and maintain molecular weight, while the capping agent acts as a second intermediary that protects against unwanted side reactions, together preserving mechanical properties during recycling
2Strength
If chain extenders are used to increase polymer molecular weight and offset molecular weight reduction during thermal processing, then high molecular weight polyesters can be maintained, but branching and crosslinking occur leading to degraded material quality
Solution Approach 1:
The capping agent acts as a protective intermediary that caps the hydroxyl groups generated during epoxide reaction with polyester end groups. This prevents the hydroxyl groups from participating in unwanted condensation reactions that would cause branching and crosslinking, thereby maintaining compositional stability while the epoxide compound extends chains to preserve molecular weight
Solution Approach 2:
The invention effectively extracts or removes the problematic hydroxyl groups from the system by having the capping agent react with them to form stable capped structures. This extraction of reactive hydroxyl groups eliminates their ability to cause branching and crosslinking, allowing chain extension to proceed without compromising composition quality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively recycles polyesters multiple times, maintaining their mechanical and chemical properties comparable to virgin materials, reducing recycling costs and plastic pollution.
Implementation Method 1
the epoxide compound provides controlled chain extension of the polyester subjected to thermal processing in a way that controls, limits, or prevent branching and crosslinking
Implementation Method 2
the capping agent is reactive with in situ-generated hydroxy groups resulting from reaction with the polyester and the epoxide compound
Data Source
AI summary
The disclosure relates to a recyclable polyester composition including a polyester, an epoxide compound, and optionally a capping agent. The epoxide compound can be a sterically hindered epoxide and/or a polyfunctional epoxide. The capping agent can be selected and included based on its ability to react with in situ-generated hydroxy groups resulting from reaction with the polyester and the epoxide compound. The capping agent is included when the epoxide compound is a polyfunctional epoxide in order to control or limit branching during chain extension. The inclusion of the epoxide compound provides a controlled chain extension of the polyester subjected to thermal processing in a way that controls, limits, or prevents branching and crosslinking, but which also increases polymer molecular weight in a manner that offsets the molecular weight reduction associated with thermal processing in the absence of the disclosed epoxide compounds.