Thermo‐physical properties of polypropylene fibers containing a microencapsulated flame retardant

A microencapsulated flame retardant with a melamine‐formaldehyde shell was prepared by in situ polymerization, then incorporated into an iPP matrix with a coupling agent to manufacture multifilament yarns by melt spinning. The influence of the post‐treatment on the resulted microcapsules with an alcoholic solution was also studied. The spinnability of these formulations based on the interface characterization from contact angle measurements, tensile test and thermal characterizations was explored to determine the maximum draw ratio (DR) to apply. Finally, knitted fabrics were processed from multifilaments, and their flame‐retardant properties were evaluated by performing fire tests according to the FMVSS 302 and Din 4102 part B experiments. The different mechanical and thermal behaviors were discussed in terms of the influence of the DR and the post‐treatment applied on fibers during the spinning process and during the recovery of the microcapsules, respectively. The results showed that it was possible to obtain multifilament yarns with a DR of 4, but the best properties were obtained with a DR of 3 and for un‐treated microcapsules. Furthermore, the samples containing un‐treated microcapsules reach a B rating at the FMVSS test with a fast flame progression and a very low duration of burning. Copyright © 2012 John Wiley & Sons, Ltd.