Pre-expanded Thermoplastic Elastomer Composition for Sealing
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Solution Overview
Problem
The challenge is to develop a pre-expanded elastomeric thermoplastic material with improved elastomeric properties and reduced volatile organic compound emissions, suitable for sealing applications, while avoiding the complexities of gas injection and precise dosing of chemical blowing agents, and maintaining the ability to be processed through standard extrusion or injection methods.
Innovation Solution
A non-crosslinked pre-expansion elastomeric thermoplastic composition comprising 15-37% multiblock elastomers with soft and hard blocks, and 0.5-2% heat-expandable polymeric particles, which can be heated to expand, resulting in a composition with enhanced elastomeric properties and low VOC emissions, processed using standard methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical blowing agents are used for expansion, then the material density is reduced, but the dosage precision is difficult to control leading to dispersity in final density
Solution Approach 1:
The patent divides the expansion function into separate physical expansion particles (microspheres) that are pre-filled with expandable fluid, rather than using chemical blowing agents that require precise dosing. These particles are incorporated into the thermoplastic elastomer composition at a controlled weight ratio (5-50% by weight), providing predictable expansion behavior without complex dosing requirements.
Solution Approach 2:
The patent introduces physical expansion particles as an intermediary substance that mediates the expansion process. These particles contain pre-measured expandable fluid (such as pentane, isobutane, or CO2) enclosed in porous polymer shells, acting as controlled expansion agents that eliminate the need for precise dosing of chemical blowing agents while achieving consistent density reduction.
2Reliability
If crosslinking is used to reduce residual deformation after compression, then the sealing properties are improved, but the volatile organic compound emissions increase
Solution Approach 1:
The patent changes the chemical composition parameters by selecting specific multiblock elastomers with appropriate glass transition temperatures and molecular weights that provide low compression set without requiring crosslinking. The composition includes soft blocks (polybutadiene, polyisoprene) and hard blocks (polystyrene, polyethylene) in controlled ratios that inherently deliver the required elastomeric properties and low residual deformation.
Solution Approach 2:
The patent creates a composite material system combining multiblock elastomers with physical expansion particles. This composite structure provides both the elastomeric properties needed for low residual deformation and the expansion capability for density reduction, all without requiring crosslinking agents that would generate VOC emissions.
3Quantity of substance
If gas injection is used for expansion, then the material density is reduced, but the equipment cost and implementation complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-filling porous polymer particles with expandable fluid during their manufacturing, before incorporation into the thermoplastic elastomer composition. This pre-preparation eliminates the need for complex gas injection equipment during processing, as the expansion capability is already built into the particles themselves.
Solution Approach 2:
The patent extracts the expansion function from the processing equipment (gas injection system) and embeds it directly into the material components (physical expansion particles). This extraction simplifies the processing equipment requirements to standard extrusion or injection molding machines while maintaining the density reduction benefit.
4Quantity of substance
If masterbatch dosing is used for expansion, then the material density is reduced, but the dispersity in final density increases
Solution Approach 1:
The patent applies local quality by ensuring uniform distribution of physical expansion particles throughout the thermoplastic elastomer composition. The particles are incorporated at controlled weight ratios (5-50% by weight) and their discrete, uniform size distribution (typically 10-100 micrometers) ensures consistent local expansion behavior, leading to uniform final density throughout the molded product.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves elastomeric properties comparable to non-expanded materials with reduced residual deformation after compression and lower VOC emissions, while allowing for simpler processing without the need for gas injection or precise dosing of blowing agents.
Implementation Method 1
During the preparation of the plastic material which consists of heating the elastomeric matrix, the polymeric particles of physical expansion swell under the effect of the increase in pressure due to the expansion of the fluid until reaching a certain size thus forming the porosity of the expanded elastomeric composition
Data Source
AI summary
The invention relates to a pre-expansion elastomeric thermoplastic composition comprising at least 10% by weight of one or more elastomers and heat-expandable polymer particles encapsulating a heat-expandable fluid. The invention also relates to a method for preparing an expanded elastomeric thermoplastic composition comprising the following steps: - injecting the pre-expansion elastomeric composition according to the invention into a mold or adding it to an extruder die, and then - heating the pre-expansion elastomeric composition to a temperature above the expansion temperature of the heat-expandable polymer particles, preferably above 160°C. The invention further relates to an expanded elastomeric thermoplastic composition obtainable by the method.Finally, the invention relates to a sealing lip used in the transport industry and in building construction.