Thermal Hazard Characteristics of Unsaturated Polyester Resin Mixed with Hardeners

Abstract

Unsaturated polyester resin (UP) is a critical polymer material in applications of many fields, such as the chemical industry, military, and architecture. For improving the mechanical properties, some hardeners, such as methyl ethyl ketone peroxide (MEKPO) or tert-butyl peroxy-2-ethylhexanoate (TBPO), can trigger the curing reaction in UP polymerization, which causes that UP changes the structure from monomer to polymer. However, polymerization is a strong exothermic reaction, which can increase the risk of thermal runaway reaction in UP. Therefore, the mechanisms and characteristics in the thermal runaway reaction of UP mixed with hardeners should be studied for preventing and controlling UP explosion. The thermal hazards of UP mixed with hardeners were determined by thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC) analysis. According to the results, UP mixed with MEKPO exhibited a more violent mass loss and exothermic reaction than UP mixed with TBPO. Furthermore, the thermal runaway reactions of UP mixed with MEKPO or TBPO with different mixing proportions of 1:1, 3:1, and 5:1 were determined. Irrespective of MEKPO or TBPO, the mixing proportions of 3:1 exhibited a high onset temperature and low enthalpy of curing reaction (ΔHexo). This demonstrated that this proportion was safer during UP polymerization. The results of this study can provide useful information for preventing UP explosion and developing polymerization technology.

Hydrophobically Associated Hydrogel for High Sensitivity and Resolution of an Interdigital Electrode Pressure Sensor

“…Presumably this is because of hydrophobic cross-linking points which can be formed between PLMA and PPy through hydrophobic association, and with the increase of PPy, such a cross-linking point is also gradually increased, which makes it possible to effectively dissipate the energy generated during the deformation of the hydrogel through the dissociation-conjugation of hydrophobic association and then improves the mechanical properties of the hydrogel. Usually an increase in cross-linking points leads to a greater cross-linking density, which results in a faster gelation rate. , The polymerization reaction is strongly exothermic, so the gelation process of SDS/PPy/LMPAm and SDS/LMPAm hydrogels was monitored in real time by infrared thermography. As seen from Figure S3, at 6 min, SDS/PPy/LMPAm started to warm up rapidly, indicating that the polymerization had begun.…”

“…Usually an increase in cross-linking points leads to a greater cross-linking density, which results in a faster gelation rate. 41,42 The polymerization reaction is strongly exothermic, 43 so the gelation process of SDS/PPy/LMPAm and SDS/LMPAm hydrogels was monitored in real time by infrared thermography. As seen from Figure S3, at 6 min, SDS/PPy/LMPAm started to warm up rapidly, indicating that the polymerization had begun.…”