Publication: Development of thermochromic films of polylactic acid (pla)-based smart materials
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Date
2024-09-01
Authors
Chan, Qi-Hua
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Abstract
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.