Thermally Expandable Microcapsule Shell for High-Temperature Foaming
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Solution Overview
Problem
Thermally expandable microcapsules used in various applications face issues with maintaining high expansion ratios and resisting burst or shrinkage at high temperatures due to insufficient thermal resistance and strength, leading to deflation and reduced foaming efficiency.
Innovation Solution
A thermally expandable microcapsule is developed with a shell containing a thermosetting resin and a polymer obtained from a monomer composition comprising a nitrile-type monomer and a monomer with a carboxyl group, which enhances thermal resistance and gas-barrier properties, preventing burst and shrinkage at high temperatures and maintaining high expansion ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a volatile expansion agent is used in a thermoplastic shell polymer, then the microcapsule can be thermally expanded at relatively low temperature (80-130°C), but the expansion ratio is lowered and the microcapsule bursts or shrinks at high temperature due to insufficient thermal resistance
Solution Approach 1:
The shell is constructed as a composite material containing both thermoplastic polymer and thermosetting resin. The thermoplastic component (e.g., polyvinylidene chloride) provides flexibility and expansion capability, while the thermosetting resin (e.g., phenolic resin, epoxy resin, or isocyanate-modified polyurethane) forms a three-dimensional crosslinked network that provides high thermal resistance and structural strength. This composite structure allows the microcapsule to maintain both expandability at low temperature and resistance to burst/shrink at high temperature.
2Reliability
If a polymer with three-dimensional crosslinking is used to increase thermal resistance, then the microcapsule shows strong resistance to shrinkage, but the rigid crosslinks disturb expansion during foaming and reduce the expansion ratio
Solution Approach 1:
The shell structure exhibits local quality differentiation where the thermosetting resin provides rigid three-dimensional crosslinked regions for thermal resistance, while the thermoplastic polymer provides flexible regions that can expand during foaming. This spatial differentiation of properties within the composite shell allows simultaneous achievement of high thermal resistance and high expansion ratio.
Solution Approach 2:
The shell composition is designed with specific parameter ranges: thermosetting resin content of 5-50 parts by weight per 100 parts by weight of thermoplastic polymer, and crosslinking agent content of 1-20 parts by weight per 100 parts by weight of thermosetting resin. By controlling these parameters, the shell achieves optimal balance between rigidity (for thermal resistance) and flexibility (for expansion).
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 microcapsule achieves a high expansion ratio and stable foaming performance even at elevated temperatures, ensuring effective weight reduction and improved thermal insulation in foam molded products.
Implementation Method 1
a volatile expansion agent that can be gasified at a softening temperature or lower of the shell polymer
Implementation Method 2
a volatile expansion agent that can be gasified at a softening temperature or lower of the shell polymer
Data Source
AI summary
The present invention provides a thermally expandable microcapsule that maintains a high expansion ratio and hardly bursts and shrinks even at a high temperature, a foamable thermoplastic resin masterbatch and a foam molded product that are produced using the thermally expandable microcapsule, and a method for producing the thermally expandable microcapsule. The thermally expandable microcapsule comprises a volatile expansion agent included in a shell as a core agent and the shell formed of a polymer, the shell containing a thermosetting resin and a polymer obtainable by polymerization of a monomer composition containing a nitrile-type monomer and a monomer having a carboxyl group, and the thermosetting resin having no radical-polymerizable double bond and at least two functional groups reactive with a carboxyl group per molecule.