Polyamide Cap Layer for Coextruded Polyolefin Foam
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The low-pressure molding (LPM) process for producing vehicle interior trim components faces issues such as foam shear and degradation due to high injection temperatures of polypropylene, leading to defects like 'orange peel' and foam loss, which increases production costs and waste, especially when using bilaminates or trilaminates.
Innovation Solution
A physically crosslinked, closed cell polyolefin foam with a polyamide cap layer is coextruded and laminated to a film, fabric, or foil, providing a protective barrier that remains intact at injection temperatures, reducing the need for additional offal and minimizing material waste, and allowing direct injection into the mold cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polypropylene is injected at high temperature (200°C) to fill the mold cavity, then the mold cavity can be filled efficiently, but the foam layer undergoes shear and degradation causing orange peel defects and foam loss
Solution Approach 1:
The patent introduces a polyamide cap layer as an intermediary between the foam layer and the injected polypropylene. This cap layer has a melting temperature above the injection temperature of the polypropylene, allowing it to act as a protective barrier that prevents direct contact between the hot polypropylene and the foam layer, thereby eliminating shear and degradation while maintaining efficient mold filling
2Reliability
If polypropylene is injected at the offal portion of the bilaminate to avoid foam damage, then foam shear and degradation are reduced, but the cost increases due to additional offal waste
Solution Approach 1:
The patent extracts the protective function from the offal region and concentrates it in a thin polyamide cap layer applied directly to the foam surface. This eliminates the need for extensive offal portions, as the cap layer provides the necessary protection at the injection point without requiring additional sacrificial material, thereby reducing offal waste while maintaining foam integrity
3Reliability
If a TPO or TPE layer is added to create a trilaminate structure to protect the foam, then foam shear and degradation are reduced, but material costs and manufacturing complexity increase
Solution Approach 1:
The patent uses a polyamide cap layer that is laminated to the foam layer. This composite structure provides the necessary protection against shear and degradation from hot polypropylene injection. The polyamide material is selected to have a melting temperature above the injection temperature, creating an effective barrier without requiring complex multi-layer trilaminate structures
Solution Approach 2:
The patent changes the key parameter of the protective layer from using TPO or TPE materials with melting temperatures below or near the injection temperature to using polyamide materials with melting temperatures above the injection temperature. This parameter change allows the protective layer to remain intact during injection, eliminating the need for thick sacrificial layers or complex trilaminate structures
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 polyamide cap layer effectively prevents foam shear and degradation, reducing material costs and waste, while maintaining the integrity of the foam structure, thus enhancing the LPM process efficiency and reducing production costs.
Implementation Method 1
The polyamide cap layer can be selected that is not only above the melting temperature of the polypropylene being injected, but also above the injection temperature. Thus, the high melt temperature of the polyamide can ensure that the polyamide remains intact, providing a barrier that does not melt or sheer when in contact with the injected polypropylene
Implementation Method 2
a method of making coextruded, crosslinked polyolefin multilayer foam/polyamide cap structures
Implementation Method 3
a physically crosslinked, closed cell polyolefin foam with at least one polyamide cap layer
Data Source
AI summary
Described herein are physically crosslinked, closed cell continuous multilayer foam structures that includes a foam layer comprising polypropylene, polyethylene, or a combination of polypropylene and polyethylene and a polyamide cap layer. The multilayer foam structure can be obtained by coextruding a multilayer structure comprising at least one foam composition layer and at least one cap composition layer, irradiating the coextruded structure with ionizing radiation, and continuously foaming the irradiated structure.