The optical photographs of pure PEG sheet, PEG/PMMA composite sheet, and Pectin/PEG/PMMA composite sheet at 20 °C and 40 °C are shown in Fig. 4e–g and e′–g′, respectively. At 20 °C, the pure PEG sheet shows a white opacity (Fig. 4e), and PEG/PMMA composite sheet and Pe...