Multilayer Monovinylidene Aromatic Sheet for Recyclability and Stress Resistance
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Solution Overview
Problem
Existing techniques for recycling monovinylidene aromatic polymers face challenges due to variable qualities such as degree of crosslinking, gel content, mineral oil content, rubber content, and molecular weight, which affect processability and environmental stress crack resistance.
Innovation Solution
The development of thermoformable sheets with three or more layers, where the inner layer is composed of post-consumer and post-industrial recycled monovinylidene aromatic polymers impact modified by rubber, and the outer layers are made from impact modified monovinylidene aromatic polymers or their blends with polyolefins, enhancing environmental stress crack resistance and recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If post-consumer and post-industrial recycled monovinylidene aromatic polymers are used in the inner layer, then recyclability is improved, but environmental stress crack resistance deteriorates due to variable qualities
Solution Approach 1:
The sheet is divided into multiple layers with different compositions. The inner layer contains recycled polymers for recyclability, while outer layers contain impact modifiers and copolymers for environmental stress crack resistance. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
The invention uses composite material structures where the inner layer combines recycled monovinylidene aromatic polymers with impact modifiers, and outer layers combine monovinylidene aromatic polymers with unsaturated nitrile copolymers. These composite structures provide both recyclability and environmental stress crack resistance simultaneously.
2Reliability
If impact modifiers are added to improve impact strength, then environmental stress crack resistance improves, but processability deteriorates
Solution Approach 1:
Impact modifiers are added locally to specific layers (inner layer and optionally outer layers) rather than uniformly throughout the entire sheet. This localized approach provides environmental stress crack resistance where needed while maintaining better processability in the overall manufacturing process.
Solution Approach 2:
The invention controls the amount and type of impact modifiers used, and adjusts processing parameters such as temperature and mixing conditions to maintain processability while achieving the required environmental stress crack resistance. The copolymer composition is also optimized to balance these properties.
3Reliability
If multiple layers with different compositions are used to achieve excellent environmental stress crack resistance, then environmental stress crack resistance improves, but device complexity increases
Solution Approach 1:
The sheet is segmented into multiple layers with distinct compositions optimized for different functions. The inner layer focuses on recyclability with impact modification, while outer layers focus on environmental stress crack resistance. This functional segmentation achieves high reliability without unnecessary complexity.
Solution Approach 2:
The multilayer structure serves multiple functions simultaneously: the inner layer provides recyclability and impact strength, while outer layers provide environmental stress crack resistance and barrier properties. This multi-functionality justifies the increased structural complexity by delivering comprehensive performance.
4Ease of manufacture
If virgin monovinylidene aromatic polymers are blended with recycled polymers to improve processability, then processability improves, but recyclability deteriorates
Solution Approach 1:
Virgin and recycled polymers are segregated into different layers based on their optimal uses. The inner layer is dominated by recycled polymers to maintain recyclability, while virgin polymers may be used in outer layers where processability is more critical. This local quality differentiation resolves the contradiction.
Solution Approach 2:
The multilayer structure segments virgin and recycled polymer materials into different zones. This segmentation allows the recycled polymer-rich inner layer to maintain recyclability while outer layers with virgin polymers provide enhanced processability, eliminating the need to compromise overall recyclability for processability improvements.
Data Source
AI summary
Disclosed herein are compositions including a thermoformable sheet having three of more layers. Two layers include one or more monovinylidene aromatic monomer containing polymers which are impact modified by a rubber, one or more monovinylidene aromatic monomer and unsaturated nitrile containing copolymers, or a blend of one or more monovinylidene aromatic monomer containing polymers and a polyolefin, which exhibit resistance to environmental stress cracking. At least one of the two layers is an outer layer. An inner layer includes post-consumer recycled monovinylidene aromatic monomer containing polymers which are impact modified by a rubber, post-industrial recycled monovinylidene aromatic monomer containing polymers which are impact modified by a rubber. Optionally, the composition may include virgin monovinylidene aromatic monomer containing polymers which are impact modified by a rubber. Optionally, the composition may include an outer layer which is a gloss layer.