Preparation of SiO₂-coated monostearate/polyvinyl blended membrane and thereof long-lasting anti-fog performance

Anti-fog film packaging can reduce the water activity in the package and reduce the large amount of waste caused by fruit and vegetable spoilage, so it is of great research significance. In this study, SiO₂ was used as the wall material, and the core material of glyceryl monostearate (GMS) was coated by emulsion polymerization and mixed with linear low-density polyethylene (LLDPE) to prepare a long-term anti-fog film. The results show that the chemical composition and crystal structure of the prepared samples are analyzed by FTIR and XRD, which proves that GMS is successfully covered. The micromorphology and cross-sectional microstructure of the samples are analyzed by SEM, and the prepared GMS@SiO₂ is spherical, which is well dispersed in the film. The particle size and DSC tests show that the GMS@SiO₂ samples prepared under the condition of 1:2 using GMS and tetraethyl orthosilicate (TEOS) have good particle size uniformity, 83.05% are concentrated at 20-100 nm, and have the highest coating rate, 69.9%. The results of N₂ adsorption and desorption show that there are many mesoporous structures on the surface of the GMS@SiO₂. The pore size is 17.918 nm, which can effectively delay the release of GMS. Through the analysis of the thermal properties of the sample by TG, it is found that SiO₂ wall material has a better protective effect on GMS, and the maximum loss temperature of GMS is increased from 298℃ to 405℃, which is increased by about 107℃. Through thermal anti-fog test, it is found that the prepared film can effectively extend the anti-fog time of the film and has superior anti-fog performance, in 1-11 h, the film anti-fog grade is DE grade; Within 11-60 h, the film anti-fog grade is E grade, and the anti-fog film prepared directly added to GMS is E grade in 1-11 h. The anti-fog grade is grade D within 11-60 h, and the prepared anti-fog film will have broad application prospects in the fields of fruit and vegetable preservation.