Bio-Based Thermally Expandable Microspheres Shell Design
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Solution Overview
Problem
Conventional thermally expandable microspheres are produced from petrochemical-based monomers, which are not sustainable, and replacing them with bio-based monomers is challenging due to compatibility and performance requirements such as surface energy, gas barrier properties, and viscoelastic properties for effective expansion.
Innovation Solution
The use of unsaturated lactones as co-monomers to produce thermoplastic polymers that form thermally expandable microspheres with a shell encapsulating a blowing agent, allowing for expansion while retaining the agent, through an aqueous suspension polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional petrochemical-based monomers are used to produce thermally expandable microspheres, then good expansion properties and gas barrier properties are achieved, but the eco-footprint is increased due to reliance on fossil fuels
Solution Approach 1:
The invention changes the chemical composition parameters of the monomers from petrochemical-based to bio-based sources while maintaining the functional properties required for expansion. Specifically, it uses monomers with formula (1) where R1-R6 are selected from H, alkyl, aryl, or arylalkyl groups, allowing optimization of the polymer structure to achieve both sustainability and performance
Solution Approach 2:
The invention creates a composite polymer system by copolymerizing bio-based monomers of formula (1) with other ethylenically unsaturated monomers. This composite approach allows the polymer to exhibit both the environmental benefits of bio-based materials and the functional properties of conventional expandable microsphere materials
2Object-affected harmful factors
If bio-based monomers are used to replace conventional monomers, then the eco-footprint is reduced, but compatibility and performance requirements such as surface energy, gas barrier properties, and viscoelastic properties are difficult to meet
Solution Approach 1:
The invention systematically varies the substituent parameters R1-R6 in the monomer formula (1) to optimize the polymer's physical and chemical properties. By selecting different alkyl, aryl, or arylalkyl groups, the polymer's surface energy, gas barrier properties, and viscoelastic characteristics can be tuned to meet manufacturing requirements
Solution Approach 2:
The monomer formula (1) is designed with versatile substituent options that allow the same basic structure to serve multiple functions. The polymer can simultaneously provide structural integrity, gas barrier properties, and appropriate surface energy for suspension polymerization, while being derived from renewable resources
3Stability of the object's composition
If the polymer shell is made from bio-based monomers, then sustainability is improved, but the ability to retain blowing agent and achieve proper expansion is compromised
Solution Approach 1:
The glass transition temperature (Tg) of the polymer is optimized by adjusting the monomer structure parameters. The Tg is maintained within 50-250°C to ensure the shell becomes sufficiently soft at expansion temperatures to allow blowing agent volatilization and microsphere expansion, while remaining stable during storage and processing
Solution Approach 2:
The use of copolymers combining bio-based monomers with other ethylenically unsaturated monomers creates a composite shell structure that enhances gas barrier properties. This composite approach ensures the shell can retain the blowing agent during storage yet allow controlled expansion when heated
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
This approach results in thermally expandable microspheres with good expansion properties and a reduced eco-footprint, using bio-based monomers that are compatible with conventional monomers, ensuring effective expansion and retention of the blowing agent.
Implementation Method 1
aqueous suspension polymerization of ethylenically unsaturated monomer(s) using a free-radical initiator
Implementation Method 2
Upon heating the thermoplastic shell softens and simultaneously the blowing agent volatilizes
Implementation Method 3
the blowing agent volatilizes while being retained within the thermoplastic shell, which in turn causes an expansion
Data Source
AI summary
The present invention relates to thermally expandable microspheres at least partially prepared from bio-based monomers and to a process of their manufacture. The microspheres comprise a thermoplastic polymer shell encapsulating a blowing agent, wherein the thermoplastic polymer shell comprises a polymer being a homo- or copolymer of a lactone according to formula (1):wherein each of R1, R2, R3, R4, separately from one another, is selected from the group consisting of H and an alkyl group preferably with 1-4 carbon atoms. The invention further provides expanded microspheres, which can be used in a variety of applications.