Phase Change Materials Microcapsules Research Articles

Core content and stability of n‐octadecane‐containing polyurea microencapsules produced by interfacial polymerization

AbstractMicroencapsulation of phase change material (PCM) n‐octadecane was carried out by interfacial polymerization technique using core and bulk monomers as toluene‐2,4‐diisocyanate (TDI) and diethylene triamine (DETA), respectively. Cyclohexane was used as the solvent for TDI and n‐octadecane, which formed the oil phase. The effect of encapsulation procedure, core‐to‐monomer ratio (CM ratio) and PCM‐to‐cyclohexane (PC) ratio was investigated on core content, encapsulation efficiency, and stability of microcapsules. Using a modified procedure, the core content was found to increase with the increasing CM ratio and reached a maximum at 3.7, while the encapsulation efficiency continuously decreased with the increasing CM ratio. Also the encapsulation efficiency was found to have a strong dependence on PC ratio and a maximum encapsulation efficiency of 92%, along with the core content of 70% was obtained with CM ratio of 3.7 along with the PC ratio of 6. The microcapsules were well shaped, i.e., round and regular, with narrow size distribution at these conditions. The PCM microcapsules were found to be stable to heat treatment at 150°C for 8 h. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Thermal stability of composite phase change material microcapsules incorporated with silver nano-particles

This paper reports a study on the thermal stability of phase change material microcapsules that are incorporated with silver nano-particles (Ag-NPs). The novel microcapsules were fabricated by the technique of in situ polymerization, with aminoplast as the wall and phase change material bromo-hexadecane (PCM BrC16) as the core. Thermal gravimetry (TG) analysis was applied to measure the thermal stability of these microcapsules and surface morphology of the microcapsules was observed by means of scanning electron microscopy (SEM) after an application of curing treatment at 130 °C. Comparing with conventional phase change material microcapsules (PCMMs), nano-composite phase change material microcapsules (NCPCMMs) have higher thermal stability. This can be attributed to nano-composite structure of the microcapsules, in which metal Ag-NPs distributed on the surface to increase wall toughness and strength. The possible reinforcement mechanisms of the nano-composite structure are explored.

A computational analysis for effects of fibre hygroscopicity on heat and moisture transfer in textiles with PCM microcapsules

To describe the heat and moisture transfer in porous textiles with phase change material (PCM) microcapsules, a dynamic model was developed. In the model the moisture sorption of fibres and the effects of the phase transition temperature range and the heating/cooling rate on the phase change processes of the PCM were considered. Meanwhile, the theoretical predictions were validated by experimental data. Then, the processes of moisture transfer in the inter-fibre void spaces and in the fibres and their interaction with heat transfer and regulation of PCM microcapsules during ambient transient conditions were illustrated by a series of 3D diagrams. The results show that fibre hygroscopicity impacts the effect of PCM microcapsules in delaying fabric temperature variations very significantly.

Preparation of PCM microcapsules by using oil absorbable polymer particles

We attempted to prepare microcapsules by absorbing n-pentadecane as the phase change material (PCM) and methyl methacrylate (MMA) as the shell material into oil absorbable polymer particles. We could prepare the microcapsules containing PCM with the polymethyl methacrylate (PMMA) shell. In the experiment, the volume of methyl methacrylate monomer and the soaking time for oil absorbable polymer particles to soak into MMA were changed stepwise. With the increase in the volume of MMA absorbed, the diameters and mechanical strength of microcapsules were increased. Furthermore, it was found that the amount of PCM leaking from the microcapsules was decreased with the volume of MMA absorbed.

Functional Textiles Based on Polymer Composites

AbstractSummary: Functional textiles provide ample evidence of the potential wealth of opportunities still to be realised in the textile industry. In this paper, intelligent‐wear garments with thermoregulating properties are prepared using phase change materials (PCMs) microcapsules and tested. At the same time, a series of nylon 6 nanocomposites with different filler/Jojoba Oil contents have been prepared with the purpose of obtain active fibers providing care, comfort and protection for the skin. Jojoba Oil delivery through polyamide matrix in conditions simulating current applications was studied by FT‐IR.

Development of thermoregulating textile materials with microencapsulated phase change materials (PCM). IV. Performance properties and hand of fabrics treated with PCM microcapsules

AbstractPolyester knit fabrics were treated with phase‐change‐material microcapsules by a pad–dry–cure method with a polyurethane binder. The treated fabrics were evaluated in terms of the thermal properties, air permeability, moisture vapor permeability, moisture regain, low‐stress mechanical properties, and hand, with respect to the add‐on of microcapsules. The surface morphology of the treated fabrics was investigated with scanning electron microscopy. The low‐stress mechanical properties of the treated fabrics, including the tensile, shear, bending, surface, and compression properties, were measured with the Kawabata evaluation system for fabrics (KES‐FB). As the add‐on increased, the heat storage capacity of the treated fabrics increased. The treated fabric with 22.9% add‐on was capable of absorbing 4.44 J/g of heat. The air permeability and moisture vapor permeability decreased, whereas the moisture regain increased, with an increase in the add‐on. The tensile linearity and geographical roughness increased, whereas the resilience, bending, and shear properties decreased with an increase in the add‐on. The fabrics became stiffer, less smooth, and less full as the add‐on increased, and thus the total hand value decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 910–915, 2005

Development of thermoregulating textile materials with microencapsulated phase change materials (PCM). II. Preparation and application of PCM microcapsules

AbstractMelamine–formaldehyde microcapsules containing eicosane were prepared by in situ polymerization. The characterization of the microcapsules, including the particle size and size distribution, morphology, thermal properties, and stability, was carried out. The prepared microcapsules were added to polyester knit fabrics by a conventional pad–dry–cure process to develop thermoregulating textile materials. The morphology, thermal properties, and laundering properties of the treated fabrics were also investigated. The microcapsules were spherical and had melamine–formaldehyde shells containing eicosane. The microcapsules were strong enough to secure capsule stability under stirring in hot water and alkaline solutions. The heat storage capacity increased as the concentration of the microcapsules increased. The thermoregulating fabrics had heat storage capacities of 0.91–4.44 J/g, which depended on the concentration of the microcapsules. The treated fabrics retained 40% of their heat storage capacity after five launderings. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2005–2010, 2005

Experimental and Numerical Investigation of the Effect of Phase Change Materials on Clothing During Periodic Ventilation

A numerical and experimental investigation is conducted of periodic ventilation pro cesses in fabric containing microcapsules of phase change materials (PCM). When PCMS are added to textiles, they release heat as the liquid changes to a solid state and absorb heat as the solid returns to a liquid state. In this work, PCMS are incorporated in a numerical three-node fabric ventilation model to study their transient effect on body heat loss during exercise when subjected to sudden changes in environmental conditions from warm indoor air to cold outdoor air. The results indicate that the heating effect lasts approxi mately 12.5 minutes depending on PCM percentage and cold outdoor conditions. Heat released by PCMS decreases the clothed-body heat loss by an average of 40-55 W/m2 for a one-layer suit depending on the frequency of oscillation and crystallization temperature of the PCM. The experimental results reveal that under steady-state environmental condi tions, the oscillating PCM fabric has no effect on dry resistance, even though the measured sensible heat loss increases with decreasing air temperature of the chamber. When a sudden change in ambient conditions occurs, the PCM fabric delays the transient response and decreases body heat loss.

Heat Storage Characteristics of Phase Change Material Microcapsule Slurry in a Rectangular Cavity with a Heating Vertical Wall.

This paper has dealt with the Heat storage characteristics of the microcapsule slurry composed of phase change material (PCM) as a latent heat storage material and water. A rectangular cavity with a heating vertical wall, which was filled with the microcapsule slurry, was selected as the present research model. The heating wall temperature, the width of the cavity and the PCM concentration were set as parameters. It was clarified that the transportation of latent heat evolved by melting of the PCM in the slurry exerted on a remarkable influence on the natural convection heat transfer. In addition, it was found that the heat transfer coefficient reached a local maximum value with an increase in initial temperature difference between heating wall and PCM. The heat storage completion time also have a local maximum value with an increase in heating wall temperature due to the latent heat by melting the PCM in the slurry.

Using Phase Change Materials in Clothing

When microcapsules of phase change materials (PCMS) are added to textiles, they absorb heat energy as they change from a solid to a liquid state and release heat as they return to a solid state. This project quantifies the effect of PCMS in clothing on heat flow from the body during temperature transients. One- and two-layer body suits are constructed of a fabric/foam laminate produced with and without PCMS, and heat loss from a thermal manikin is measured as it is moved from a warm chamber to a cold chamber and back again. The results indicate that the heating and cooling effects last approximately 15 minutes. Heat released by PCMS in a cold environment decreases body heat loss by an average of 6.5 W for a one-layer suit and 13.2 W for a two-layer suit compared with non-PCM counterparts. PCM cooling effects increase body heat loss in a similar manner; therefore, PCMS in clothing provide a small, temporary heating/cooling effect during environmental transients.