Multi-layer PLA Foamed Body Heat Resistance
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Solution Overview
Problem
Conventional polylactic acid resin foamed bodies, whether crystalline or non-crystalline, face challenges in achieving a balance between heat resistance, thermoformability, and mechanical strength, with crystalline forms having poor foamability and non-crystalline forms lacking heat resistance.
Innovation Solution
A multi-layered polylactic acid resin foamed body is created by combining a polylactic acid resin foamed layer with a thermoplastic resin layer, where the foamed layer's cell shape and thermal properties are optimized to satisfy specific conditions, including cell diameter ratios and calorific values, to enhance mechanical strength and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-crystalline polylactic acid resin is used for foaming, then good moldability and foamability are achieved, but heat resistance deteriorates and the foamed sheet deforms even at room temperature
Solution Approach 1:
The invention divides the polylactic acid resin into multiple layers with different crystallinities. The first layer (foamed layer) uses non-crystalline resin for good foamability, while the second layer (skin layer) uses crystalline resin for heat resistance. This segmentation allows each layer to fulfill its specific functional requirement without compromising the other.
Solution Approach 2:
Different regions of the foamed body are assigned different material properties. The inner foamed layer has non-crystalline structure optimized for cell formation, while the outer skin layer has crystalline structure optimized for thermal stability. This local differentiation of material quality resolves the contradiction between foamability and heat resistance.
2Temperature
If a crystalline polylactic acid resin is used for foaming, then good heat resistance is achieved, but foamability and thermoformability deteriorate
Solution Approach 1:
The crystalline polylactic acid resin is segregated to the skin layer only, while the foamed layer uses non-crystalline resin. This segmentation ensures that the crystalline resin provides heat resistance where needed without interfering with the foamability of the bulk material.
Solution Approach 2:
The crystalline structure is localized to the outer skin layer where heat resistance is critical, while the inner foamed layer maintains non-crystalline structure for optimal cell formation and expansion during foaming.
3Device complexity
If a single-layer polylactic acid resin foamed body is produced, then simplicity of structure is maintained, but mechanical strength and heat resistance cannot be simultaneously optimized
Solution Approach 1:
The invention creates a composite structure with two distinct layers: a non-crystalline foamed layer for mechanical cushioning and cell structure, and a crystalline skin layer for thermal stability and surface quality. This composite approach optimizes both mechanical strength and heat resistance simultaneously.
Solution Approach 2:
The single-layer structure is segmented into two functional layers with different material properties. The foamed layer provides mechanical strength through its cellular structure, while the skin layer provides heat resistance through crystalline ordering, achieving both properties without excessive complexity.
4Temperature
If crystalline polylactic acid resin is used for foaming, then heat resistance is improved, but thermoformability deteriorates due to high apparent density and non-uniform cell shapes
Solution Approach 1:
The structure is segmented so that the foamed layer (non-crystalline) handles thermoforming operations with its uniform cell structure and lower apparent density, while the skin layer (crystalline) provides heat resistance during and after forming.
Solution Approach 2:
The non-uniform cell shapes and high apparent density issues are localized to the skin layer which does not require thermoforming, while the foamed layer maintains uniform cells optimized for thermoformability.
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 multi-layered structure achieves excellent mechanical strength and heat resistance, enabling the production of foamed bodies with improved thermoformability and heat resistance through heat treatment, suitable for applications requiring both properties.
Implementation Method 1
the difference (ΔHendo:2° C./min−ΔHexo:2° C./min) between an endothermic calorific value (ΔHendo:2° C./min) and an exothermic calorific value (ΔHexo:2° C./min) of said foamed layer as measured by heat flux differential scanning calorimetry at a heating rate of 2° C./min is less than 40 J/g
Implementation Method 2
a multi-layered polylactic acid resin foamed body obtained by heat treating the above multi-layered polylactic acid resin foamed body and having excellent heat resistance and mechanical strength
Data Source
AI summary
An object of the present invention is to provide a multi-layered polylactic acid resin foamed body of a crystalline polylactic acid resin which has good appearance and excellent mechanical strength such as bending strength and compressive strength and which is capable of being imparted with excellent heat resistance, and to provide a multi-layered polylactic acid resin foamed molded article having excellent appearance, heat resistance and mechanical strengh. The multi-layered polylactic acid resien foamed body of the present invention is a laminate having a polylactic acid resin foamed layer and a thermoplastic resin layer provided at least one side of the foamed layer, wherein the foamed layer has a cell shape satisfying specific conditions, wherein the difference (ΔHendo:2° C./min−ΔHexo:2° C./min) between an endothermic calorific value (ΔHendo:2° C./min) and an exothermic calorific value (ΔHexo:2° C./min) of the foamed layer as measured by heat flux differential scanning calorimetry at a heating rate of 2° C./min is less than 40 J/g, and wherein the endothermic calorific value (ΔHendo:2° C./min) is at least 10 J/g and the exothermic calorific value (ΔHexo:2° C./min) is at least 3 J/g.