Low Temperature UV Microencapsulation of Phase Change Materials
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Solution Overview
Problem
Conventional methods for microencapsulating phase change materials (PCMs) require high temperatures, leading to leakage and degradation of thermal storage properties due to the tendency of organic PCMs to exude during phase change, especially at ambient temperatures.
Innovation Solution
A low temperature microencapsulation method using a thin film closed loop UV reactor, where a phase change emulsion is prepared with a surfactant and monomer, then subjected to UV photopolymerization within the reactor to form microcapsules, utilizing UV lamps for polymerization and a nitrogen atmosphere to prevent oxygenation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high temperature microencapsulation methods are used, then the encapsulation process can be completed, but the phase change material leaks and exudes to the surface causing oily stains and degradation of thermal storage properties
Solution Approach 1:
The invention changes the temperature parameter from conventional high temperatures to low temperatures (below the melting point of the phase change material), and introduces UV irradiation as a new parameter to initiate polymerization. This parameter change allows encapsulation without thermal leakage of the PCM.
Solution Approach 2:
The invention replaces the thermal field (heat-based polymerization) with a UV light field (photopolymerization). Instead of using thermal energy to cure the encapsulant, UV lamps initiate free radical polymerization at low temperatures, eliminating the thermal cause of PCM leakage.
2Ease of manufacture
If high temperatures are used for microencapsulation, then the encapsulation process proceeds, but the surface becomes oily and stained due to PCM exusion
Solution Approach 1:
The invention changes the temperature parameter from high to low (below PCM melting point), and introduces UV irradiation as the curing mechanism. This allows the encapsulation process to proceed without thermal exusion of PCM to the surface.
Solution Approach 2:
The invention substitutes thermal curing with UV photopolymerization. The UV light field initiates free radical polymerization of the encapsulant monomer at low temperatures, preventing the thermal conditions that cause oily stains while maintaining ease of manufacture.
3Manufacturing precision
If conventional microencapsulation methods are used, then encapsulation can be achieved, but the process requires high temperatures that cause degradation of thermal storage properties
Solution Approach 1:
The invention inverts the temperature parameter from high to low (below PCM melting point), and introduces UV irradiation intensity and duration as new control parameters. This maintains encapsulation quality while eliminating high temperature degradation.
Solution Approach 2:
The invention replaces the thermal field with a UV light field to initiate polymerization. UV photopolymerization proceeds at low temperatures through photochemical reactions, achieving the same encapsulation quality without thermal degradation of PCM properties.
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 method effectively encapsulates PCMs at lower temperatures, preventing leakage and maintaining thermal storage properties, as demonstrated by the production of stable, high-energy storage capacity microcapsules with improved morphology and thermal characteristics.
Implementation Method 1
initiating the photo polymerization of monomers using at least one UV lamp inside the UV reactor for photo polymerization until the phase change material is encapsulated within a polymeric shell
Data Source
Figure 1
Figure 2A~2B
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AI summary
The method for low temperature microencapsulation of phase change materials or other components includes the following steps: (a) preparing a phase change emulsion including droplets of at least one active phase-change material in water with a surfactant; (b) adding a monomer of at least one encapsulating agent; (c) introducing the phase change emulsion into a UV reactor while stirring the emulsion; and (d) initiating the photo polymerization of monomers using at least one UV lamp inside the UV reactor for photo polymerization until the phase change material is encapsulated within a polymeric shell to form microcapsules. The microcapsules obtained by this process may have a diameter between about 0.5 to about 2 µm. Other sizes can also be obtained by changing stirring speed of the emulsion.