Blow-Molded Polyolefin Foam with Uniform Closed-Cell Expansion
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Solution Overview
Problem
Blow-molded foam products often have unevenly sized foamed cells, leading to surface roughness and potential cell rupture during expansion, which affects their smoothness and weight efficiency.
Innovation Solution
A blow-molded foam with a closed cell structure and polyolefin-based resin, specifically a propylene homopolymer with a long-chain branched structure, is produced using a process involving a mixing step with a foaming agent in a supercritical state, ensuring uniform cell size and surface smoothness through controlled expansion and extrusion rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If foamed cells are expanded to high expansion ratio, then weight reduction is achieved, but cell rupture and size unevenness occur leading to poor surface smoothness
Solution Approach 1:
The patent changes the physical state parameter of the foaming agent from gaseous to supercritical state. This parameter change allows the foaming agent to dissolve uniformly in the resin and generate bubbles of uniform size during expansion, achieving both high expansion ratio (weight reduction) and uniform cell size (surface smoothness) without cell rupture
Solution Approach 2:
The patent utilizes the phase transition of the foaming agent from supercritical state to gaseous state during the blow-molding process. The supercritical CO2 dissolves in the resin, then upon pressure release and heating, transitions to gas phase forming uniform bubbles that expand uniformly, achieving homogeneous cell structure with high expansion ratio while maintaining surface smoothness
2Manufacturing precision
If cell diameter is reduced to achieve fine cells, then expansion ratio can be maintained, but cell size becomes non-uniform resulting in poor surface smoothness
Solution Approach 1:
The patent applies parameter changes by transforming the foaming agent into supercritical state, which fundamentally changes how the foaming agent interacts with the resin. This single parameter change (state of foaming agent) simultaneously achieves uniform cell size distribution and maintains process simplicity, avoiding the need for complex multi-step processes
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 has homogeneous cell sizes, reduced weight, and improved surface smoothness, enhancing ventilation efficiency and impact resistance, while maintaining high rigidity and appearance, particularly suitable for climate control ducts and skinned panels.
Implementation Method 1
a foaming agent which is a supercritical fluid
Implementation Method 2
the foamed cells are abruptly expanded to make cells larger
Data Source
AI summary
The present invention provides a process for producing a blow-molded foam including foamed cells, the process including:kneading a polyolefin-based resin containing a foaming agent mixed therewith in an extruder, andextruding a parison formed of the polyolefin-based resin between split mold blocks from a die slit at an extrusion rate of 700 kg/h or more.