Properties of phase change material impregnated vegetal nonwovens for use in cementitious composite reinforcement

Natural fibres offer sustainable reinforcement for composites, while the construction sector seeks materials combining thermal regulation and mechanical performance. This work investigates the little-explored direct impregnation of nonwoven flax fibres with phase change materials (PCM) for multifunctional cement composites. Two PCMs with different phase transition temperatures (21 and 28 °C) were evaluated. The nonwoven impregnated with 28 °C PCM exhibited superior performance, both in thermal and mechanical terms, and for this reason it was selected for incorporation into the cementitious composites. In addition, a comparison was carried out with a microencapsulated PCM displaying a similar transition temperature. All composite samples underwent thermal analysis and mechanical tests. Thermal performance improvements relative to the control specimens (without PCM) resulted in a significant time delay in temperature response in all cases. The nonwoven-impregnated composite manufactured above the transition temperature exhibited superior mechanical performance compared with microencapsulated PCM systems. Although showing lower strength than the control specimen without PCM, its remaining flexural strength of ∼7 MPa highlights its potential for non-structural applications, including roof tiles and, in specific cases, ventilated façades. • Flax nonwovens can effectively encapsulate PCM. • PCM-impregnated flax nonwovens enhanced thermal regulation in cementitious composites. • Nonwoven encapsulated PCM showed thermal delay comparable to microencapsulated PCM. • PCM-impregnated nonwovens keep strain-hardening behaviour.