A blue thermochromic pinewood that can change from dark blue to light blue at 38–48°C

A blue thermochromic dye (B-TD) was prepared by mixing crystal violet lactone (CVL), hydroxyethyl acrylate (HEA) and myristic acid myristyl ester (MME). B-TD is a phase-changing material and can change colour at above 32°C about 5 s. The B-TD can permeate into pre-treated pinewood samples about 8–10 mm from the surface of samples after immersed pre-treated pinewood samples in B-TD for about 10 min at 70 °C. A blue thermochromic pinewood (B-TP) was prepared by filled the B-TD into pre-treated pinewood and covered polypropylene wax that can prevent B-TD overflowing from wood-based material when at phase-changing temperature. The B-TP can change colour from dark blue to light blue at 38–48°C, and can recover dark blue at below 38°C after about 5 h. B-TP can be used in a kind of pinewood woodwork that can indicate the temperature of woodwork surface to users by its colour-change phenomenon at 38–48°C, covering the lowest temperature of cryogenic burns (42°C), so this kind of pinewood woodwork can warn the temperature of cryogenic burns for avoiding cryogenic burns by its colour-change phenomenon.