Self-extinguishing polypropylene with a mass fraction of 9% intumescent additive - A new physical way for enhancing the fire retardant efficiency

Effect of Functionalized Carbon Microspheres Combined with Ammonium Polyphosphate on Fire Safety Performance of Thermoplastic Polyurethane

In this article, carbon microspheres (CMSs) synthesized by the hydrothermal method and CMSs-Fe (with Fe³⁺ adsorbed on the surface of CMSs) were combined with ammonium polyphosphate (APP) to achieve the fire safety improvement of thermoplastic polyurethane (TPU). The fire safety performance of TPU composites was investigated by the cone calorimeter test, microscale combustion calorimeter test, thermogravimetric analysis/infrared spectrometry, Raman spectrometry, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that CMSs and CMSs-Fe can improve the fire safety performance of TPU/APP composites and the effect of CMSs-Fe was better than that of CMSs. The peak heat release rate of the sample containing 0.25 wt % CMSs and 7.75 wt % APP was 16.7% lower than that of the sample containing 8.00 wt % APP, and the content of toxic gases was also reduced in the fire smoke. Also, total heat release and total smoke release of the sample containing CMSs-Fe were 54.7% and 11.6%, respectively, lower than those of the sample containing 0.25% CMSs. It confirmed the contribution of CMSs to the flame retardant system, and the performance of CMSs is improved by adsorbing Fe³⁺.

Key Role of Reinforcing Structures in the Flame Retardant Performance of Self-Reinforced Polypropylene Composites

The flame retardant synergism between highly stretched polymer fibres and intumescent flame retardant systems was investigated in self-reinforced polypropylene composites. It was found that the structure of reinforcement, such as degree of molecular orientation, fibre alignment and weave type, has a particular effect on the fire performance of the intumescent system. As little as 7.2 wt % additive content, one third of the amount needed in non-reinforced polypropylene matrix, was sufficient to reach a UL-94 V-0 rating. The best result was found in self-reinforced polypropylene composites reinforced with unidirectional fibres. In addition to the fire retardant performance, the mechanical properties were also evaluated. The maximum was found at optimal consolidation temperature, while the flame retardant additive in the matrix did not influence the mechanical performance up to the investigated 13 wt % concentration.

Synthesis and properties of novel polystyrene/polyurea and functional graphene-based nanocomposite foams

A simple route has been adopted for the fabrication of polyurea using polycondensation of 4,4'-diphenylmethane diisocyanate and 1,4-phenylene diamine. Amalgamation of polystyrene, polyurea and functional graphene (F–G) yielded a series of nanocomposite foams. The morphological, electrical, mechanical, thermal, and flammability properties of materials were investigated and found to be dependent upon the intrinsic properties of graphene-based materials and their state of dispersion in matrix. Field emission scanning electron microscopy revealed a strong interaction between polystyrene/polyurea and functional graphene surface forming unique layered cellular structure. Mechanical results revealed a synergistic interaction between F–G and polystyrene/polyurea matrix providing a shielding mechanism against graphene layer damage during compression. The 10% thermal decomposition temperature of polystyrene/polyurea/F–G 1–5 foams measured was in the range of 432–470℃. UL 94 showed V-1 rating for polystyrene/polyurea foam, while polystyrene/polyurea/F–G 1–5 foams attained V-0 rating. Water absorption capacity was improved steadily with the time and was maximum after 96 h for polystyrene/polyurea/F–G 5 foam (4.53%). Functional graphene also produced excellent electrical conductivity improvement in polystyrene/polyurea/F–G 5 foam (101) relative to polystyrene/polyurea/F–G 1 foam (10−2) and neat polystyrene/polyurea foam materials (10−7).

Effect of Particle Size of Additives on the Flammability and Mechanical Properties of Intumescent Flame Retarded Polypropylene Compounds

The effect of particle size reduction of the components of a common intumescent flame retardant system, consisting of pentaerythritol (PER) and ammonium polyphosphate (APP) in a weight ratio of 1 to 2, was investigated on the flammability and mechanical performance of flame retarded polypropylene (PP) compounds. Additives of reduced particle size were obtained by ball milling. In the case of PER, the significant reduction of particle size resulted in inferior flame retardant and mechanical performance, while the systems containing milled APP noticeably outperformed the reference intumescent system containing as-received additives. The beneficial effect of the particle size reduction of APP is explained by the better distribution of the particles in the polymer matrix and by the modified degradation mechanism which results in the formation of an effectively protecting carbonaceous foam accompanied with improved mechanical resistance. Nevertheless, 10% higher tensile strength was measured for the flame retarded PP compound when as-received APP was substituted by milled APP.