Polystyrene Resin Composition for Blow-Molded Foamed Skin
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Solution Overview
Problem
The production of skin-covered foamed molded articles with elongated or complicated shapes faces challenges in achieving high productivity and sufficient adhesion strength between the foam layer and the skin, due to issues like parison drawdown, local thinning, and insufficient heat capacity, leading to cost inefficiencies and low yield.
Innovation Solution
A method involving a polystyrene resin composition with specific Charpy impact strength, melt mass flow rate, and molecular weight ratios, combined with the use of impact-resistant and recycled polystyrene resins, to form a parison that is extruded and blow-molded into a skin with a hollow interior space, where expanded polystyrene beads are filled and fused-bonded to form a uniform foam layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If impact resistant polystyrene resin is used to prevent cracks in the skin, then impact resistance is improved, but the parison tends to be drawn down and thinned during extrusion
Solution Approach 1:
The invention changes the molecular weight parameters of the polystyrene resin by controlling the weight average molecular weight (Mw) to be within a specific range of 100,000 to 1,000,000. This parameter optimization allows the resin to maintain both impact resistance and drawdown resistance, preventing parison thinning while preserving the skin's mechanical strength.
Solution Approach 2:
The invention uses a composite resin composition comprising polystyrene resin (70-95 parts by weight) and rubber component (5-30 parts by weight). This composite structure combines the high impact resistance of rubber-modified polystyrene with the drawdown resistance of properly selected polystyrene, achieving both crack prevention and uniform skin thickness without excessive drawdown.
2Strength
If the parison is extruded at high temperature to firmly fuse-bond the foam layer to the skin, then adhesion strength is improved, but the parison is drawn down and the upper portion becomes thinned
Solution Approach 1:
The invention optimizes the molecular weight parameters of the polystyrene resin (Mw: 100,000 to 1,000,000) to achieve the right balance between processability at high temperatures and resistance to drawdown. This allows the parison to be extruded at high temperatures for strong adhesion while preventing excessive thinning of the upper portion.
3Productivity
If a thin skin is used to reduce weight and cost, then productivity and cost efficiency are improved, but the heat capacity is insufficient leading to poor adhesion strength
Solution Approach 1:
The invention changes the resin composition parameters by using polystyrene with optimized molecular weight (Mw: 100,000 to 1,000,000) and controlling the rubber component content (5-30 parts by weight). This allows the skin to be made thinner for improved productivity while maintaining sufficient heat capacity and adhesion strength through the optimized resin formulation.
4Strength
If the skin is made thicker to ensure sufficient heat capacity and adhesion strength, then manufacturing quality is improved, but the weight and cost increase
Solution Approach 1:
The invention optimizes the resin parameters (Mw: 100,000 to 1,000,000 and rubber component: 5-30 parts by weight) to achieve the minimum necessary skin thickness for sufficient heat capacity and adhesion strength. This allows the skin to be as thin as possible while maintaining manufacturing quality, thereby reducing weight and cost.
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
This approach reduces parison drawdown, ensures uniform skin thickness, enhances impact resistance, and allows for a thinner, lighter skin-covered foamed molded article with improved adhesion strength and productivity, even for elongated or complicated shapes.
Implementation Method 1
heating the expanded polystyrene beads filled in the hollow interior space to fuse-bond the expanded polystyrene beads to each other
Implementation Method 2
fuse-bond the expanded polystyrene beads to each other and to form a foam layer fuse-bonded to the skin
Implementation Method 3
high-pressure blow air is introduced into the parison through the blow pin to press the parison against an inner surface of the mold to form a hollow molded article
Implementation Method 4
supplying a heating medium, such as steam, into the skin to cause the expanded polystyrene beads to expand (secondary expansion)
Data Source
AI summary
A method for producing a skin-covered foamed molded article includes blow molding a parison into a skin and heating expanded polystyrene beads filled in a hollow space of the skin to form a foam layer fuse-bonded to the skin, polystyrene resin composition having specific Charpy impact strength, MFR and branching degree. The skin of the skin-covered foamed molded article is formed of the specific polystyrene resin composition.