Halochromic poly(lactic acid) as innovative ph-sensors
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Date
2019-07
Authors
Ng Jia Yam
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Abstract
Poly(lactic acid) PLA has low flexibility and limited report about adding pH dye into polymer. PLA-pH sensors incorporated with plasticizer poly(ethylene glycol) (PEG) (0.16, 0.28, 0.37, 0.44 and 0.49 wt%) and dye bromocresol purple (0.001, 0.002, 0.003, 0.005 and 0.0074 wt%) were produced using solution casting method. Different techniques such as scanning electron microscope (SEM), fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), ultraviolet-visible spectroscopy (UV-Vis), and tensile testing were used to assess the properties of PLA-pH sensor. Colour change testing and real-life food application (lemon and fish) were implemented to investigate the colour changing properties of the sensor. Results showed that PLA-pH sensors changed colour towards different pH solution. The sensors showed yellow colour in acidic solution and violet colour in alkaline solution. The sensors showed clearly visible colour change when under exposed to lemon and fish. No colour changed was observed on the first 24h, but bluish green on the sensors was observed on the 2nd day. This colour became darker eventually violet colour formed on the 4th day. SEM results showed that dye was homogenously dispersed in the PLA matrix and presence of dye was confirmed using FTIR. Tensile testing showed that dye didn’t significantly influenced the tensile properties of the sensors.