Preparation and properties of organic montmorillonite/SiO2 aerogel/PET composites and their fibers

Purpose - The purpose of this study is to improve the mechanical properties, thermal insulation properties and flame retardant properties of polyethylene terephthalate (PET), the organic montmorillonite (OMMT)/SiO2 aerogel/PET composites and fibers were prepared, and the effects of the OMMT/SiO2 aerogel on the structure, thermal conductivity and flame retardance of the OMMT/SiO2 aerogel/PET composites and their fibers were systematically investigated. Design/methodology/approach - The OMMT/SiO2 aerogel/PET composites and fibers were prepared by in-situ polymerization and melt spinning using SiO2 aerogel as thermal insulation filler and OMMT (DK2) as comodified filler. Findings - The experimental results showed that OMMT improved the crystallization properties of PET. Compared with the crystallinity of SiO2 aerogel/PET composites (34.8%), SiO2 aerogel/PET composites and their fibers reached 45.1% and 49.2%, respectively. The breaking strength of the OMMT/SiO2 aerogel/PET composite fibers were gradually increased with the OMMT content. When the content of OMMT was 0.8 wt.%, the fracture strength of the composite fibers reached 4.40 cN/dtex, which was 54% higher than that of the SiO2 aerogel/PET fiber. In addition, the thermal insulation properties of the composites and their fibers were improved by addition of fillers, and at the same time reached the flame retardant level. The thermal conductivity of the 0.8 wt.% OMMT/SiO2 aerogel/PET composites was 101.78 mW/(m<middle dot>K), which was 49.3% and 58.8% lower than that of the SiO2 aerogel/PET composites and the pure PET, respectively. The thermal conductivity of the fiber fabrics woven from the 0.8 wt.% OMMT/SiO2 aerogel/PET composites was 28.18 mW/(m<middle dot>K), which was 29.0% and 44.6% lower than that of the SiO2 aerogel/PET composite fiber fabrics and PET fiber fabrics. The flame retardancy of the composites was improved, with an limiting oxygen index value of 29.2% for the 0.8 wt.% OMMT/SiO2 aerogel/PET composites, which was 4.1% higher compared to the SiO2 aerogel/PET composites, and achieved the flame retardant level. Research limitations/implications - The SiO2 aerogel/PET composites and their fibers have good mechanical properties, flame retardant properties and thermal insulation properties, exhibited good potential for application in the field of thermal insulation, such as warm clothing. Nowadays, as the energy crisis is becoming more and more serious, it is very important to improve the thermal insulation properties of PET to reduce energy losses and mitigate the energy crisis. Originality/value - In this study, PET based composites and their fibers with excellent mechanical properties, thermal insulation properties and flame retardant property were obtained by using three-dimensional network porous silica aerogel with low density and low thermal conductivity as the thermal insulation functional filler and two-dimensional layered OMMT as the synergetic modified filler.