Thermally Expandable Microcapsule Shell Strength
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Solution Overview
Problem
Existing thermally expandable microcapsules lack excellent heat resistance and high expansion ratios, making them unsuitable for molding processes involving high shearing forces like kneading, calender, extrusion, and injection molding, as they tend to burst or deform under high temperatures.
Innovation Solution
A thermally expandable microcapsule with a polymer shell that maintains a storage elastic modulus of 1×105 N/m2 or more at 200° C. and 250° C., and a maximum displacement of 300 μm or more, ensuring the shell remains in a rubbery state and supports high expansion ratios, thereby preventing deformation during molding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional thermally expandable microcapsules are used to achieve weight reduction and design impartment, then they can expand at low temperatures (80-130°C), but they burst or contract upon heating at high temperatures causing decreased expansion ratio
Solution Approach 1:
The patent changes the physical and chemical parameters of the shell polymer, specifically selecting polymers with softening points of 180°C or higher (such as polyacrylic acid, polyacrylamide, carboxymethyl cellulose, and their crosslinked products). This parameter change enables the microcapsules to maintain structural integrity at high temperatures while still allowing expansion, thereby resolving the contradiction between expansion temperature and heat resistance
Solution Approach 2:
The patent uses composite material structures by combining shell polymers with crosslinking agents to create a network structure that provides both thermal stability and expansion capability. The crosslinked shell structure prevents bursting at high temperatures while maintaining the ability to expand, thus resolving the contradiction between reliability at high temperature and expansion functionality
2Temperature
If thermally expandable microcapsules are heated at 130-140°C for about 1 minute to achieve thermal expansion, then partial expansion occurs, but it is difficult to produce microcapsules with excellent heat resistance having maximum foaming temperature of 180°C or higher
Solution Approach 1:
The patent systematically changes the softening point parameter of the shell polymer to 180°C or higher by selecting specific polymers (polyacrylic acid, polyacrylamide, carboxymethyl cellulose) and their crosslinked forms. This parameter elevation enables the shell to maintain strength at higher temperatures while still permitting expansion, resolving the contradiction between maximum foaming temperature and shell strength
Solution Approach 2:
The patent applies local quality by creating a crosslinked network structure specifically in the shell region, which provides localized reinforcement at high temperatures. The crosslinked structure maintains shell integrity where needed while allowing controlled expansion in the core region, thus resolving the contradiction between strength and foaming temperature
3Reliability
If thermally expandable microcapsules with high maximum foaming temperature (180°C or higher) are produced, then they show excellent heat resistance, but they are difficult to use in molding processes involving strong shearing force as they may deform or be crushed
Solution Approach 1:
The patent employs composite material strategy by combining shell polymers with crosslinking agents to form a reinforced network structure. This composite shell provides both the heat resistance required for high-temperature applications and the mechanical strength needed to withstand shearing forces during molding processes, resolving the contradiction between heat resistance and mechanical strength
Solution Approach 2:
The patent changes the structural parameters of the shell by introducing crosslinking, which fundamentally alters the mechanical properties. The crosslinked structure provides enhanced rigidity and strength to resist shearing forces while maintaining the high softening point for heat resistance, thus resolving the contradiction between reliability under thermal and mechanical stress
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 exhibits excellent heat resistance and high expansion ratios, enabling stable performance in molding processes with high shearing forces, resulting in foamed products with improved lightness, heat insulation, and shock resistance.
Implementation Method 1
a thermoplastic shell polymer including a volatile expansion agent which can change to a gas state at a softening temperature or lower of the shell polymer
Implementation Method 2
thermally expandable microcapsule... thermally expandable at a relatively low temperature of about 80 to 130° C.
Data Source
AI summary
A thermally expandable microcapsule, which shows excellent heat resistance and a high expansion ratio and thereby can be suitably used for molding processes involving high shearing force, such as kneading molding, calender molding, extrusion molding, and injection molding. The thermally expandable microcapsule also provides a foamed product using the thermally expandable microcapsule. The thermally expandable microcapsule contains a shell made of a polymer; and a volatile expansion agent as a core agent encapsulated in the shell, the storage elastic modulus (E′) of the shell at a temperature of 200° C. and a frequency of 10 Hz being 1×105 N/m2 or more, the storage elastic modulus (E′) of the shell at a temperature of 250° C. and a frequency of 10 Hz being 1×105 N/m2 or more, and a maximum displacement amount measured by thermomechanical analysis being 300 μm or more.