Polypropylene Core Polyethylene Shell Foamed Bead Molded Article
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Solution Overview
Problem
Molded articles of polypropylene-based resin expanded beads often have insufficient protective properties and rigidity, and those made from polyethylene-based resin expanded beads tend to have high mass per unit volume, leading to issues with deformation and bending under weight and packaged objects.
Innovation Solution
A molded article comprising a core layer of polypropylene-based resin in a foamed state and a covering layer of polyethylene-based resin, with specific magnification, compressive stress, and flexural modulus ranges to achieve balanced rigidity and lightness, produced through a method involving granulation, expansion, and in-mold molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyethylene-based resin expanded beads are used to achieve rigidity, then rigidity is improved, but mass per unit volume increases leading to deformation and bending
Solution Approach 1:
The invention uses composite expanded beads comprising a polypropylene-based resin core layer and a polyethylene-based resin covering layer. This composite structure combines the light weight advantage of polypropylene with the surface properties of polyethylene, achieving rigidity without excessive mass per unit volume increase
Solution Approach 2:
The covering layer is applied only on the surface of the core layer, providing localized polyethylene properties where needed for surface performance while maintaining the lightweight polypropylene core, thus balancing rigidity and weight
2Weight of moving object
If polypropylene-based resin expanded beads are used, then mass per unit volume is reduced, but protective properties and rigidity become insufficient
Solution Approach 1:
The composite structure with polypropylene core and polyethylene covering layer provides both the light weight of polypropylene and the enhanced protective properties of polyethylene, resolving the contradiction between weight reduction and sufficient protection
Solution Approach 2:
The invention optimizes the mass ratio between core layer and covering layer (core layer: covering layer = 95:5 to 88:12) to achieve the right balance between maintaining low mass per unit volume and providing sufficient protective properties and rigidity
3Reliability
If the covering layer mass ratio is increased to improve protective properties, then protective properties are improved, but mass per unit volume increases
Solution Approach 1:
The invention defines an optimal range for the mass ratio between core layer and covering layer (95:5 to 88:12), which provides sufficient protective properties while controlling mass per unit volume increase
Solution Approach 2:
The covering layer is applied only where needed on the surface, providing protective properties locally without adding excessive overall mass to the expanded bead molded article
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 provides a molded article with enhanced protective properties and rigidity while maintaining a small mass per unit volume, effectively addressing the limitations of existing polypropylene and polyethylene-based resin expanded bead materials.
Implementation Method 1
a core layer in a foamed state containing a polypropylene-based resin and a covering layer which covers the core layer and contains a polyethylene-based resin
Data Source
AI summary
A molded article of polypropylene-based resin expanded beads, obtained by in-mold molding of the polypropylene-based resin expanded beads, each bead including: a core layer, in a foamed state, having a polypropylene-based resin; and a covering layer, which covers the core layer, having a polyethylene-based resin. A molded article magnification X [times] of the molded article is 55 times to 90 times, a value of a product X·σ50 of a 50% compressive stress σ50 [kPa] and the molded article magnification X is 6500 or more, and a 5% compressive stress σ5 of the expanded beads molded article is 5 kPa to 25 kPa.