Heterophasic Propylene Copolymer Automotive Part Tiger Stripe Reduction
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Solution Overview
Problem
Current polypropylene-based materials used in automotive parts face issues with high emissions of volatile organic compounds (VOCs) and the occurrence of 'tiger stripes' due to the use of inorganic fillers like talc, which affect mechanical properties and optical surface quality.
Innovation Solution
A thermoplastic composition combining a heterophasic propylene copolymer with high aspect ratio talc and specific antioxidant additives, such as tocopherol or tocotrienol, to achieve reduced emissions and improved mechanical properties while minimizing tiger stripes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If inorganic filler (talc) is added to polypropylene based materials to achieve low Coefficient of Linear Thermal Expansion (CLTE) and desired mechanical properties, then stiffness and thermal stability are improved, but optical surface properties deteriorate and tiger stripes occur
Solution Approach 1:
The patent changes the chemical parameters of the polymer matrix by using a specific propylene-α-olefin copolymer with controlled composition (5-20 wt% α-olefin content) and molecular weight distribution. This parameter change allows the material to maintain low CLTE and good stiffness while improving surface optical properties and reducing tiger stripes, as the copolymer's flexible chain structure better accommodates the talc filler without causing surface defects.
Solution Approach 2:
The patent creates a composite material system combining propylene-α-olefin copolymer with specific talc filler content (20-40 wt%). The composite achieves optimal balance between mechanical properties (stiffness, low CLTE) and surface quality by carefully controlling the interaction between the copolymer matrix and talc filler, where the copolymer's composition acts as a compatibilizer reducing tiger stripe formation.
2Stability of the object's composition
If inorganic filler (talc) is added to achieve low CLTE and mechanical properties, then thermal stability and stiffness are improved, but tiger stripes and color variations occur
Solution Approach 1:
The patent modifies the polymer composition parameters by incorporating α-olefin comonomer units (5-20 wt%) in the propylene copolymer chain. This compositional change alters the polymer's interaction with talc filler and its thermal behavior, maintaining thermal stability while reducing the formation of tiger stripes and color variations during injection molding.
3Strength
If conventional polypropylene based materials are used to reduce cost and achieve good mechanical properties, then manufacturing cost is reduced and strength is improved, but VOC emissions increase
Solution Approach 1:
The patent changes the chemical composition parameters by using a propylene-α-olefin copolymer with specific molecular weight and comonomer content, replacing conventional homopolymer or simple copolymer formulations. This parameter change reduces VOC emissions while maintaining mechanical properties, as the copolymer structure allows for optimized processing conditions and reduced need for volatile additives.
Data Source
AI summary
The present invention relates to an automotive part (such as an exterior automotive part, a semi-exterior automotive part or an interior automotive part) prepared from a thermoplastic composition comprising:from 48-95 wt. % based on the weight of the composition of a heterophasic propylene copolymer; wherein said heterophasic propylene copolymer consists of i) a propylene-based matrix consisting of a propylene homopolymer and/or a propylene-α-olefin copolymer, said propylene α-olefin copolymer consisting of at least 70 wt. %, and ii) a dispersed ethylene-α-olefin copolymer comprising ethylene and at least one C3 to C10 α-olefin;from 0-20 wt. %, preferably from 1-20 wt. % ethylene-α-olefin elastomer comprising ethylene and a C3 to C10 α-olefin;from 1-30 wt. % high aspect ratio;from 0.05-2 wt. % antioxidant additive selected from the group consisting of i) a tocopherol or a tocotrienol; or ii) a hydroxylaminefrom 0-3 wt. % an additional additive.