**Abstract**

Phase change materials (PCMs) have been integrated into clothing and textiles to provide added value in terms of thermoregulation and thus added comfort to the wearer in intensely hot and cold weather conditions. Since clothing is laundered several times during the service life of the textile, the effects of simulated domestic laundering on the physical and thermal properties of a non-woven textile that contains PCMs were investigated. The thermal properties, such as the thermal degradation, melting, evaporation, and crystallisation were measured by the Thermal Gravimetric Analysis (TGA) and the Differential Scanning Calorimetry (DSC) analytical techniques. The physical properties, such as the microcapsule size distribution, and the microcapsule morphologies of the PCM microcapsules, were measured by the Scanning Electron Microscopy (SEM) and Raman analytical techniques. The primary objective of this study is to determine the effect of repeated laundering at different wash temperatures.

**Keywords:** phase change materials, repeated laundering, thermal degradation, crystallisation, enthalpy, thermograms, thermal properties, physical properties

## **1. Introduction**

Phase change materials (PCMs) are 'latent' heat storage materials. The thermal energy transfer happens when a material changes from solid to liquid or liquid to solid. PCM absorbs and releases heat at an almost constant temperature. Latent heat stores 5 to 14 times more heat per unit volume than sensible storage materials such as bricks or rocks. Latent heat storage is one of the highly effective techniques of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method requires a significantly higher storage density with a minor temperature difference between storing and releasing heat [1].

As described by Grynaeus et al. [2], PCMs are designed to utilise latent heat absorption associated with a reversible phase change transition, such as solid to liquid transition. The material can be used as an absorber of heat whereby several thermal energies will be absorbed by the PCM before its temperature can increase. The PCM can also be preheated and used as a barrier to cold, as a greater quantity

of heat must be removed from the PCM before its temperature can begin to decline.

The development and application of PCM, as a class of thermal energy storage systems, are receiving increasing attention due to their contribution to a more efficient environmentally friendly energy utilisation. The PCM technology was first developed in the 1970s by the National Aeronautics and Space Administration (NASA) of the United States to protect delicate instruments in outer space from large temperature extremes. Today PCMs are one of the most widely used energy storage materials in the fields of solar energy utilisation, energy-conserving in buildings, thermal insulation, and thermal regulation [3].

According to Yazdi & Sheikhzadeth [1], textiles are one of the most used applications of PCMs for thermoregulating principles. During the phase change, the temperature remains unchanged; as a result, the PCM can stabilise the human body temperature. The cooling effect of the PCM depends on the ability to absorb heat during the periods when external heat load or body heat production surpasses heat loss.

In the highly competitive textile marketplace, customers are requiring not only comfort and fashion, but also functionality in both daily wear and sporting apparel. Phase change materials have been incorporated into clothing to provide added functionality and value in terms of thermoregulation and thus increased comfort to the wearer, in notably extreme weather conditions and sporting activities. Since clothing is laundered many times, it was deemed important to study the effect of repeated laundering on the thermoregulating properties of fabrics containing PCMs.

In this study, the effect of simulated domestic laundering on the physical and thermal characteristics of a non-woven textile that contains PCM is investigated since this is important in terms of the functional lifecycle and durability of PCMs and can contribute to improving the physical and thermal performance of PCMs and their design, as well as the laundering conditions [4, 5].
