Effects of Kevlar pulp on the enhancement of cryogenic mechanical properties of polyurethane foam

Abstract

Polyurethane foam (PUF) is used as an insulation material for liquefied natural gas (LNG) carrier storage systems to maintain the liquefaction temperature of natural gas at −163 °C and to prevent external heat input. Kevlar pulp, which maintains material performance at cryogenic temperatures, displays excellent heat resistance, elasticity, and nonflammability. In this study, Kevlar pulp was added to PUF as a reinforcement material. Various experiments, specifically microstructural analysis (SEM and computed tomography), material performance tests (compressive strength and thermal conductivity), and spectroscopic analysis (XRD and FTIR), were conducted to confirm the effect of the Kevlar additive. Finding the optimum weight-percentage range is important to obtain a valid result because mechanical properties of experimental insulation are adjusted by controlling the quantity of the additive. The results of this study show that adding 0.8 wt% Kevlar pulp achieves the best improvement in mechanical strength (6.535 MPa at cryogenic temperatures) and the optimum thermal conductivity (0.027 W/m∙K) because at this level, the cell volume distribution is the smallest. In addition, the results confirm that the addition of Kevlar pulp below a certain quantity threshold does not affect PUF parameters but merely acts as a useful intercellular filler to help improve insulation performance.