Polyacetal Sliding Member Composition for Low-Friction Wear Resistance
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Solution Overview
Problem
Polyacetal resin sliding members exhibit high friction coefficients, stick-slip, and creaking sounds due to fluctuating friction coefficients, and existing solutions fail to adequately improve load carrying capacity and wear resistance while maintaining molding workability and preventing surface exfoliation.
Innovation Solution
A polyacetal resin composition comprising 1.5 to 7% ethylene-propylene-diene rubber, 0.5 to 3% saponified ethylene-vinyl acetate copolymer, and 0.05 to 0.3% ethylene-α-olefin copolymer, with an optional 0.1 to 10% lubricant, which enhances molding workability, prevents creaking sounds, and improves load carrying capacity and sliding characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyacetal resin alone is used for sliding members, then self-lubricity and wear resistance are excellent, but coefficient of friction is high and stick-slip occurs causing creaking sounds
Solution Approach 1:
The patent uses a composite material system combining polyacetal resin with ethylene-propylene-diene rubber (EPDM) and saponified ethylene-vinyl acetate copolymer. This composite structure allows the polyacetal to provide wear resistance while the rubber and copolymer components reduce friction and eliminate stick-slip phenomena, thereby preventing creaking sounds without sacrificing the base material's excellent wear properties.
2Object-generated harmful factors
If polyolefin resin is compounded with polyacetal resin to improve sliding characteristics, then friction is reduced to some extent, but load carrying capacity is insufficient under high load conditions and surface exfoliation may occur
Solution Approach 1:
The patent replaces polyolefin resin with ethylene-propylene-diene rubber (EPDM), which provides superior elasticity and adhesion. The EPDM forms a flexible, adherent layer that maintains load carrying capacity under high surface pressure conditions while preventing surface exfoliation. The saponified ethylene-vinyl acetate copolymer further enhances adhesion to the polyacetal matrix, ensuring structural integrity under load.
3Reliability
If complex molding conditions are used to achieve uniform mixing of components, then sliding characteristics are improved, but molding workability becomes complicated requiring temperature control
Solution Approach 1:
The patent defines specific compounding ratios (5-30 parts EPDM and 3-20 parts saponified ethylene-vinyl acetate copolymer per 100 parts polyacetal resin) that optimize mixing uniformity and sliding characteristics. These controlled parameter ranges enable consistent performance with standard molding procedures, eliminating the need for complex temperature control while achieving uniform component distribution and excellent sliding properties.
Data Source
AI summary
A polyacetal resin composition includes: in addition to a polyacetal resin as a principal component, 1.5 to 7% by mass of an ethylene-propylene-diene rubber; 0.5 to 3% by mass of a saponified ethylene-vinyl acetate copolymer; and 0.05 to 0.3% by mass of an ethylene-α-olefincopolymer.