Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The PHRR decreases by 80%, and the TSP decreases by 66.9%.

The LOI increases from 18% to 28.0%, and the composite achieves a UL-94 V-0 rating.

Compared with conventional flame-retarded PP, the tensile strength increases from 16.55 to 19.07 MPa, and the impact strength increases from 3.25 to 8.50 kJ·m−2.


ABSTRACT
A novel hyperbranched phosphorus-containing polyamide (HPA-NP) was synthesized and incorporated into a polypropylene (PP) matrix to achieve a superior balance between flame retardancy and mechanical performance. The distinctive three-dimensional hyperbranched architecture, in which 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and phenolic moieties were grafted as functional “fruits,” improved the interfacial compatibility between HPA-NP and the PP matrix, thereby promoting effective stress transfer. The combined introduction of phosphorus- and hydroxyl-containing groups imparted HPA-NP with flame-retardant functions in both the condensed and gas phases, thereby promoting the development of a compact intumescent char upon combustion. Consequently, the composite with only 2.4 wt% HPA-NP achieved a high limiting oxygen index (LOI) of 28%, a UL-94 V-0 rating, and an 80% reduction in peak heat release rate (PHRR, from 780.4 to 155.5 kW m−2). Importantly, these improvements in fire safety were achieved without compromising mechanical integrity, as evidenced by a tensile strength of 18.2 MPa and a notched impact strength of 6.6 kJ·m−2. These results demonstrated an effective approach for simultaneously enhancing flame retardancy and mechanical reinforcement in polyolefin composites.