Styrenic Polymer Blend for HFO Stress Crack Resistance
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Solution Overview
Problem
The use of hydrofluoro olefin (HFO) blowing agents in refrigeration systems leads to aggressive environmental stress cracks in polystyrene inner liners of cooling apparatuses, reducing their lifespan due to susceptibility to stress crack damage.
Innovation Solution
A polymer blend comprising 80-96% impact modified styrenic polymer, 1-7% polyisobutylene and polyolefin blend, and 3-13% elastomeric block copolymer, specifically designed to enhance environmental stress crack resistance, with the elastomeric block copolymer having a monomer composition of 25-60% diene and 75-40% vinylaromatic compounds, and a glass transition temperature differential between its phases, is used to mitigate stress crack issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If HFO blowing agents are used in refrigeration systems, then environmental global warming potential is reduced, but environmental stress crack resistance of polystyrene inner liners deteriorates
Solution Approach 1:
The patent applies composite materials by creating a polymer blend consisting of impact modified polystyrene (80-96 wt%), polyisobutylene (1-7 wt%), and elastomeric block copolymer (3-13 wt%). This composite formulation combines multiple polymer components to achieve both environmental compatibility with HFO blowing agents and improved stress crack resistance, resolving the contradiction between environmental performance and material reliability.
Solution Approach 2:
The patent employs parameter changes by modifying the chemical composition and structural parameters of the polystyrene material. Specifically, it adjusts the glass transition temperature differential between hard and soft phases to 30-80°C, controls diene content at 25-60%, and optimizes the proportion of hard phase at 5-40% by volume. These parameter adjustments enhance the material's resistance to HFO-induced stress cracks while maintaining environmental compatibility.
2Strength
If impact modified polystyrene is used to improve toughness, then impact resistance is improved, but environmental stress crack resistance in presence of HFO deteriorates
Solution Approach 1:
The patent resolves this contradiction by formulating a composite material that integrates impact modified polystyrene with polyisobutylene and elastomeric block copolymer. The synergistic combination of these components maintains the impact resistance provided by the impact modified polystyrene while the additional components contribute to improved environmental stress crack resistance against HFO, achieving both properties simultaneously.
Solution Approach 2:
The patent applies local quality by creating distinct phases within the polymer blend with different properties. The hard phase (vinylaromatic blocks) provides structural integrity and impact resistance, while the soft phase (diene blocks) with specific glass transition temperature contributes to stress crack resistance. This local differentiation of material properties within the composite enables simultaneous achievement of impact resistance and environmental stress crack resistance.
Data Source
AI summary
Polymer blends comprising components A), B) and C): A) 80 to 96% by weight of an impact modified styrenic polymer A), B) 1 to 7% by weight of a polymer blend B) comprising B1) 25 to 75% by weight of polyisobutylene and B2) 25 to 75 % by weight of a polyolefin, C) 3 to 13% by weight of an elastomeric block copolymer C) of structure (A-(B/A))n-A, where A is a vinylaromatic block, (B/A) is a random copolymer block of vinylaromatic monomer and diene, and n is 1 to 10, exhibit improved environmental stress crack resistance properties in presence of hydrofluoro olefins.