Study on the Thermal Insulation Performance of PAN Pre-Oxidised Fibre Felts

In this paper, an orthogonal experiment of 3 factors and 3 levels was firstly designed to prepare PAN pre-oxidised fibre felts with good thermal insulation properties; the range method was used to analyse the result of the orthogonal experiment, and finally the tensile properties and thermal stability were tested. Finally, pre-oxidised fibre felt composites for the coating of silica aerogel were prepared using the coating process to compound silica aerogel on re-oxidised fibre felts. Firstly, the influence of the content of silica aerogel on the heat insulation performance of the coated composite materials was analysed, and then a test of the coefficient of thermal conductivity, an experiment on the back temperature, and characterisations of the tensile properties and thermal stability of the composite coating of pre-oxidised fibre felt composites of the coating of silica aerogel were carried out. Results showed that through analysis of the orthogonal experiment, we can state that the best preparation process of pre-oxidised fibre needled felts was as follows: needle number – 2, needle depth – 8 mm, and needle frequency – 140 times/min. The transverse tensile strength of PAN pre-oxidised fibre needled felts prepared by crossly webbing of PAN pre-oxidised fibres was superior to the longitudinal tensile strength; thermogravimetric analysis showed that the pre-oxidised fibre needled felts had excellent thermal stability. The coefficient of thermal conductivity of the aerogel coating of the composites firstly decreased and then increased with an increase in the content of aerogel. Coated composites had the lowest coefficient of thermal conductivity when the aerogel content was 4% wt. At temperatures of 100 °C, 150 °C and 200 °C, the heating rate of the transient-state back temperature and the steady-state average temperature were both the lowest when the aerogel content was 6% wt.