Evaluation of shape memory fabrics

Abstract

Shape memory fabrics in this research are novel and temperature sensitive products prepared by applying waterborne thermally sensitive shape memory polymers (SMP) onto fabrics through specific finishing processes. This thesis concerns the evaluation of shape memory effects of fabrics using modified evaluation methods. There are three thermally sensitive shape memory effects for fabrics. They are flat appearance, crease retention and bagging recovery. A subjective evaluation method for evaluating the fabric shape memory effects in water was developed based on the AATCC Test Method 124 and 88C. The experimental procedures were newly designed. The effect of water temperature, recovery method and drying method on fabric shape memory effects were investigated. The results show that the shape memory fabrics possess shape memory effects of flat appearance and crease retention in water at 60 oC. Moreover, tumble dry could enhance the shape memory effects of fabrics. In addition, washing in the recovery stage of fabrics can give a higher fabric shape memory effect compared with immersing samples in water. An objective evaluation method was also established to evaluate the fabric shape memory effects of flat appearance and crease retention in water. This newly designed method was modified from the AATCC Test Method 66. The Wrinkle Recovery Tester was used to measure the Original Angles and Shape Memory Angles. These parameters were used in newly developed equations of Shape Memory Coefficient of flat samples (Sf%) and Shape Memory Coefficient of creased samples (Sc%). Since it was found that the Shape Memory Coefficients were complicated and has a limitation, their equations were then further simplified and modified respectively. A Flat Recovery % (FRec%) and Crease Recovery % (CRec%) were developed to give a better representation of the fabric shape memory effects. After investigating the fabric shape memory effects in water, the fabric shape memory effects in air at various temperatures and relative humidities were determined using both subjective and objective evaluation methods. It is discovered that high relative humidity can enhance the fabric shape memory effect of flat appearance. However, the fabric shape memory effect of crease retention is lowered if the relative humidity is too high. Furthermore, an optimum condition for the recovery of fabrics in air is found. The relationship between the fabric shape memory effects in water and air was compared, using a subjective evaluation method. It is shown that the fabric shape memory effects of flat appearance and crease retention in water are higher than that in air. It is easier for samples to recover their original flat and creased shapes in water than in air. Apart from the flat appearance and crease retention, the fabric shape memory effect of bagging recovery was also evaluated. The Bagging Recovery Percentages for the warp direction (BPR%) and the weft direction (BTR%) of a fabric were established. The experimental procedures were designed in order to measure the bagging recovering ability of samples after immersing in water at various temperatures. In addition, a Bagging Recovery Rating (BRR) was set up to integrate the ability of fabric bagging recovery in warp and weft directions to determine the fabric shape memory effect. The finding shows that a knitted fabric has a higher bagging recovery effect when putting in water at switch temperature compared with woven fabrics. Study on the evaluation of shape memory fabrics by using new characterization methods can help to understand the fabric shape memory effects under various conditions clearly. As a result, designing evaluation methods and analysing evaluation results for the shape memory fabrics are very significant.