The dependance of effectiveness of incorporated microencapsulated phase change materials on different structures of knitted fabrics

Abstract

In order to ensure thermal comfort of the wearer, clothing directly contacting to the skin has to have good thermoregulation properties. Various types of phase change materials (PCM) are used in the production of smart materials capable actively control the temperature of the body. PCM have the capacity to absorb, store and release heat energy. Their effectiveness is characterized by quantities of absorbed/released heat energy, expressed as enthalpy. Higher is the enthalpy better thermoregulation effect is achieved. The aim of the research was to determine the dependence of PCM efficiency on the structure of double layer knitted fabrics and to evaluate their durability of finishing with microcapsules. Double layer weft knitted fabrics of four different combined patterns, manufactured from cotton/PES, PES (Coolplus®, 4 channel profile fiber) and PES spun yarns of linear density 20.0 tex, were selected for investigations. In order to increase effectiveness of thermoregulation all fabrics were equally treated with organic PCM microcapsules MikrathermicTM P by padding method. These microcapsules have functional reactive groups on the shell surface which bind to fibres and can react with cellulosic and synthetic fibers without binders. The effectiveness of PCM on knitted fabrics treated with microcapsules was investigated in the temperature range of −10−+50 °C at 10 °C/min speed in heating and cooling processes with differential scanning calorimeter (DSC) Q10. Examinations (DSC thermograms) have showed that absorbed energy (cooling effect) of all investigated knitted fabrics is higher than released energy (heating effect). It was determined that the effectiveness of incorporated PCM depends on the structure of knitted farbics. The fibre composition of fabrics has the biggest influence on the initial effectiveness of PCM. The maximum effect of PCM (approx. 7.08-5.65 J/g) was received for knitted fabrics, produced from cotton/PES, and the smallest effect–from PES spun yarns. Investigating the durability of microcapsules to washing it was determined that the PCM effectiveness of various knitted fabrics meanly decreases approx. 1.4-2.7 times after 5 washing cycles. Treatment of samples to artificial day light showed that PCM on knitted fabrics are stable in comparison with applied dyes - colour difference ΔECMC after treatment reaches 1-2.4 value.