Polyester-Polyimide Thermoplastic Foam for Heat-Stable Molding

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Solution Overview

Problem

Existing thermoplastic resin foams and fiber-reinforced composites face issues with low heat resistance and softening when heated, leading to reduced rigidity and handling difficulties, and existing methods for improving heat-dimensional stability prolong molding times and require additional equipment.

Innovation Solution

A thermoplastic resin foam and fiber-reinforced resin composite are developed using a mixture of crystalline and amorphous polyester resins, combined with a polyimide resin, to achieve a single glass transition temperature and enhanced heat resistance, along with a method of extruding and foaming a thermoplastic resin composition to form the foam.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a foamed PET sheet is preheated to soften and then molded with a temperature that promotes crystallization, then heat-dimensional stability is improved, but molding time is prolonged and equipment investment is required

Engineering Contradiction:

Improveheat-dimensional stabilityVSAvoidmolding time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The invention changes the chemical composition parameters of the resin by incorporating polyimide resin alongside polyester resin, creating a composite material with inherently improved heat resistance and dimensional stability without requiring post-molding heat treatment processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite thermoplastic resin composition combining polyester resin and polyimide resin, where the polyimide component provides high-temperature stability and dimensional integrity, eliminating the need for separate crystallization promotion steps and specialized equipment

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If a thermoplastic polyester resin foam sheet contains specific proportions of crystalline and amorphous polyester resins, then heat-dimensional stability is improved, but heat resistance is reduced causing softening when heated

Engineering Contradiction:

Improveheat-dimensional stabilityVSAvoidheat resistance

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

The invention combines polyester resin with polyimide resin to create a composite material that leverages the high-temperature stability of polyimide to compensate for the softening tendency of polyester, achieving both heat-dimensional stability and heat resistance through synergistic material properties

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention modifies the resin composition by introducing polyimide resin with high glass transition temperature (150-250°C) to raise the overall thermal stability parameter of the foam, enabling it to maintain rigidity at temperatures where pure polyester would soften

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If pre-foamed granules of PET with low crystallinity are filled into a mold and heated to perform in-mold foam molding, then the molding process is simplified, but crystallization must be promoted after heating which prolongs molding time

Engineering Contradiction:

Improvemolding process simplicityVSAvoidmolding time

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The invention uses a composite resin composition of polyester and polyimide that provides inherent heat resistance, eliminating the need for post-heating crystallization promotion steps and allowing the molding process to be both simplified and time-efficient

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The polyimide resin component self-provides thermal stability during the molding process, automatically maintaining dimensional integrity without requiring external crystallization promotion measures or extended heating cycles

Inventive Principle:

Principle #25Self-service

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 resulting foam and composite exhibit improved heat resistance and rigidity, maintaining structural integrity during heating, while reducing molding time and equipment requirements.

Implementation Method 1

a method of extruding and foaming a thermoplastic resin composition to form the foam

Methodology Applied

Scientific EffectFoaming: Foam

Implementation Method 2

achieve a single glass transition temperature and enhanced heat resistance

Methodology Applied

Scientific EffectGlass transition:

Data Source

PatentUS12590208B2Thermoplastic resin foam, thermoplastic resin foam sheet, fiber-reinforced resin composite, method for manufacturing thermoplastic resin foam, thermoplastic resin foam molded article, method for manufacturing thermoplastic resin foam molded article, and foamed resin composite

Publication Date: 2026.03.31 SEKISUI PLASTICS CO LTD

AI summary

A thermoplastic resin foam including a thermoplastic resin, wherein: the thermoplastic resin includes a polyester resin and a polyimide resin, and the thermoplastic resin foam shows a single glass transition temperature Tg. The glass transition temperature of the thermoplastic resin is preferably 80 to 130° C. An absolute value of difference between heat absorption and heat generation, each determined by heat flux differential scanning calorimetry at a heating rate of 10° C./min, is preferably 3 to 35 J/g.