Methacrylic Resin Molded Article for Thin-Wall Impact Strength
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Solution Overview
Problem
Methacrylic resin compositions used in vehicle components face challenges in achieving sufficient Charpy impact strength, particularly as components become thinner and larger, leading to decreased impact resistance.
Innovation Solution
A molded article composed of a methacrylic resin composition with specific properties, including a pencil hardness of 2 H or higher and a craze formation time of 19 seconds or longer, measured using a defined test method, and containing two methacrylic resins with specific molecular weight ratios and structural units, is produced through injection molding under controlled temperature and speed conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the molded article is made thinner and larger to meet weight reduction and design requirements, then the weight and size requirements are satisfied, but the impact strength decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight distribution of the methacrylic resin, specifically setting W1 (ratio of peak area from starting point to molecular weight 30,000) to 10-25% and W2 (ratio of peak area from molecular weight 300,000 to end point) to 5-35%, with Mw/Mn ratio between 2.0-6.0. These parameter optimizations enable the resin to achieve both thin-wall moldability and high impact strength, resolving the contradiction between weight reduction and impact strength maintenance.
Solution Approach 2:
The patent uses composite materials by combining methacrylic resin with specific additives including nucleating agents (0.01-1.0 part by mass), antioxidants (0.01-1.0 part by mass), and UV absorbers (0.01-1.0 part by mass). This composite approach enhances the impact strength and overall performance of the molded article while maintaining the thin-wall structure required for weight reduction.
2Reliability
If conventional methacrylic resin composition is used, then the basic transparency and heat resistance are achieved, but the Charpy impact strength is insufficient
Solution Approach 1:
The patent resolves this contradiction by changing the molecular weight distribution parameters of the methacrylic resin. By controlling W1 to 10-25%, W2 to 5-35%, and Mw/Mn to 2.0-6.0, the resin maintains its inherent transparency and heat resistance while achieving sufficient Charpy impact strength. This precise parameter control allows all three properties to coexist at required levels.
Solution Approach 2:
The patent employs composite materials by formulating the methacrylic resin with specific additives: nucleating agents (0.01-1.0 part by mass) to enhance crystallinity and mechanical properties, antioxidants (0.01-1.0 part by mass) to prevent degradation and maintain long-term reliability, and UV absorbers (0.01-1.0 part by mass) to protect against UV damage. This composite formulation achieves the required Charpy impact strength while preserving transparency and heat resistance.
3Use of energy by moving object
If the molded article is produced with thinner walls to reduce weight, then fuel efficiency improves, but the impact resistance decreases
Solution Approach 1:
The patent addresses this contradiction by optimizing the molecular weight distribution parameters of the methacrylic resin. By setting W1 to 10-25%, W2 to 5-35%, and Mw/Mn to 2.0-6.0, the resin achieves excellent thin-wall moldability and high impact strength simultaneously. This enables production of thinner molded articles for weight reduction and improved fuel efficiency while maintaining sufficient impact resistance.
Solution Approach 2:
The patent uses composite materials by combining methacrylic resin with nucleating agents (0.01-1.0 part by mass), antioxidants (0.01-1.0 part by mass), and UV absorbers (0.01-1.0 part by mass). This composite formulation enhances the impact resistance of thin-walled molded articles, enabling weight reduction for improved fuel efficiency without sacrificing the required impact resistance.
Data Source
AI summary
Provided are a molded article excellent in a Charpy impact strength and a method of producing the same. A molded article contains a methacrylic resin composition containing at least one methacrylic resin, in which a pencil hardness is 2 H or higher, and a craze formation time is 19 seconds or longer, the craze formation time being measured by sequentially performing the following steps 1) to 5):1) preparing a test piece that is a strip-shaped molded article, the test piece having a through-hole provided on one end side in a longitudinal direction;2) heating and drying the test piece;3) clamping the other end side of the test piece in the longitudinal direction and fixing the test piece to a fixing table so that extending directions of an upper surface and a lower surface of the test piece coincide with a horizontal direction;4) applying ethanol one or more times to a predetermined region of the upper surface while generating a surface stress on the upper surface by applying a load calculated by a specific equation in a vertical direction at a position where the through-hole of the test piece is provided, and maintaining a state in which the ethanol is applied; and5) obtaining the craze formation time by measuring a time from the start of the application of the ethanol to the formation of the craze in the test piece.