Phase change materials coating methods

Zuckerman JL, Pushaw RJ, Perry BT and Wyner DM (2003), Fabric coating containing energy absorbing phase change material and method of manufacturing same, US Patent 6514362. 

In the solvent method the separation of the solubilised or dispersed material from the solvent phase can be explained by precipitation or phase change induced by solvent evaporation, addition of electrolyte, pH modification or heat treatment (Krochta and McHugh 1997). Such treatments can be adjusted to enhance film formation or specific properties. For composite emulsion-based films or coatings a lipid material and most likely a surfactant, is added to the solution, which is then heated above the lipid melting point and homogenised. The prepared solution is then applied on an appropriate support and the solvent evaporates. 

This method utihzes a fused silica rod coated with a thin layer of stationary phase mounted in a holder. During extraction, the fiber is exposed to the sample, and analytes are adsorbed onto the stationary phase and concentrated. After a defined extraction time, the fiber is withdrawn in the holder and then analytes are thermally desorbed in the GC injector. Several types of coatings are commercially available, such as PDMS, polyamide, Carbowax-DVB, Carboxen-PDMS, and PDMS-DVB. Coatings prepared with three kinds of materials are also available (e.g., DVB-Carboxen-PDMS) [71]. Selection of the fiber is mainly based on the principle like dissolves like. For example, PDMS sorbent is suitable for the extraction of hydrocarbons, and the sorbent should be polar for the extraction of alcohols or ketones. The thickness of the coating film determines the sorption capacity of the fiber. Changing the temperature, pH, or ionic strength of the hquid... 

In application of the method, care should be taken not to change the properties of the active phase (or its precursor) in the process of slurry dip-coating, and attention should be paid to the adhesion of the coated layer. Encapsulation of the active phase may occur, which reduces the availability of the active phase. An attractive feature of slurry dipcoating is that it enables depositing of a synthesized active phase or a support material with known properties on a monolith surface. When the active phase or its precursor is difficult to synthesize or is prepared under conditions that may damage the support (e.g., perovskite) [88,94], the method is very useful. 

Physical Vapor Deposition (PVD) includes various methods for depositing thin films onto a substrate by the condensation of a desired vapor. For this process the coating material changes from the solid phase to the vapor phase and back to the solid phase (as it builds a film on the substrate). See Fig. 3 [12]. 

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