Thermoplastic Composition Reducing Tiger Stripes
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Solution Overview
Problem
Thermoplastic compositions used in manufacturing articles often suffer from 'tiger stripes,' which are color and gloss variations due to unstable mold filling properties, resulting in unsatisfactory optical surface properties, despite achieving a soft touch feel.
Innovation Solution
A thermoplastic composition comprising 10-40% glass fibers, 22-46% propylene homopolymer matrix phase, 1.5-26% ethylene-propylene copolymer dispersed phase, and 11-46% elastomers, specifically a mixture of ethylene/C5-8 α-olefin and ethylene/C3-4 α-olefin copolymers, which improves both soft touch feel and optical surface properties by reducing tiger stripes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a polyolefin composition is used to achieve soft touch feel, then the tactile quality is improved, but the optical surface properties deteriorate due to tiger stripes
Solution Approach 1:
The patent applies parameter changes by modifying the elastomer composition parameters - specifically using a mixture of ethylene/C5-8α-olefin copolymer and ethylene/C3-4α-olefin copolymer in defined weight ratios. This compositional parameter change stabilizes the melt viscosity during injection molding, eliminating tiger stripes while preserving soft touch properties.
Solution Approach 2:
The patent uses composite materials by combining specific types of elastomers (ethylene/C5-8α-olefin copolymer and ethylene/C3-4α-olefin copolymer) in a controlled mixture within the thermoplastic composition. This composite elastomer system provides both the soft touch feel and the stable rheological properties needed to prevent surface defects.
2Ease of operation
If elastomers are added to provide soft touch feel, then tactile properties are improved, but mold filling stability deteriorates causing tiger stripes
Solution Approach 1:
The patent changes the elastomer composition parameters by selecting specific copolymer types (ethylene/C5-8α-olefin and ethylene/C3-4α-olefin) and controlling their weight ratios. This parameter optimization ensures that the elastomer blend maintains stable melt viscosity throughout injection molding, preventing tiger stripe formation while delivering soft touch performance.
3Strength
If glass fibers are included to enhance mechanical properties, then strength is improved, but surface optical quality deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the elastomer composition parameters to counterbalance the surface-defect-inducing effect of glass fibers. The specific elastomer mixture stabilizes the melt flow, ensuring uniform fiber distribution and stable mold filling, thereby preventing tiger stripes even in the presence of 10-40 wt% glass fibers while maintaining mechanical reinforcement.
Data Source
AI summary
The invention is directed to a thermoplastic composition and to an article made from said thermoplastic composition. More in particular, the invention relates to blended polyolefinic materials, which, after moulding, provide a soft touch feel. The thermoplastic composition of the invention comprises (A) 10-40 % by total weight of the composition of glass fibres; (B) 22-46 % by total weight of the composition of a propylene homopolymer matrix phase; (C) 1.5-26 % by total weight of the composition of an ethylene-propylene copolymer dispersed phase; and (D) 11-46 % by total weight of the composition of a mixture of elastomers, said mixture comprising an ethylene/C5-8 α-olefin copolymer and an ethylene/C3-4 α-olefin copolymer.