Pusat Pengajian Kejuruteraan Bahan dan Sumber Mineral - Tesis

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    Development of thermochromic films of polylactic acid (pla)-based smart materials
    (2024-09-01)
    Chan, Qi-Hua
    Thermochromic materials respond to temperature changes by changing colour. As polylactic acid (PLA) is inherently non-thermochromic, commercial pigments were incorporated to impart thermochromism onto PLA. However, a high amount of fillers may cause agglomeration and poor dispersion. Plasticisers can be used to counteract the issue of poor dispersion. Moreover, blending transparent PLA with an opaque polymer may affect the colour of the thermochromic samples produced. In the first part of this study, thermochromic PLA with varying pigment content (0-3 wt.%) were produced using extrusion. In the second part, polyethylene glycol (PEG) plasticisers with different molecular weight (1400, 2500, 6000) were added to thermochromic PLA to improve the pigment dispersion. In the third part, thermochromic PLA was blended with the naturally opaque poly(butylene adipate-co-terephthalate) (PBAT) at different weight ratios (100/0, 70/30, 50/50, 30/70, 0/100). The thermochromic performance was assessed through visual observation and colorimetric analysis while the material properties were studied through tensile test, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Thermochromic PLA with 2 wt.% pigments recorded the highest total colour difference (ΔE) while that with 3 wt.% pigments exhibited clear colour changes and superior mechanical properties but the pigment dispersion was poor. Thus, PEG plasticisers were added, and it was found that the thermochromic performance and pigment distribution were successfully enhanced by PEG6000. The elongation at break also increased greatly. In addition, blending PBAT with thermochromic PLA generally improved the observability of thermochromic colour transition. The mechanical properties was also found to be tuneable with respect to the PLA/PBAT blend ratio, making thermochromic PLA/PBAT suitable for a wide range of applications such as packaging and medical devices.