A novel highly efficient intumescent flame-retardant polypropylene: Thermal degradation, flame retardance and mechanism

Mechanical, Flame-Retardant and Dielectric Properties of Intumescent Flame Retardant/Glass Fiber-Reinforced Polypropylene through a Novel Dispersed Distribution Mode

The application of continuous glass fiber-reinforced polypropylene thermoplastic composites (GF/PP) is limited due to the inadequate flame retardancy of the polypropylene (PP) matrix. Apart from altering the composition of the flame retardants, the distribution modes of flame retardants also impact material performance. In this study, an alternative approach involving non-uniform distribution is proposed, namely, dispersed distribution, in which non-flame-retardant-content layers (NFRLs) and/or low-flame-retardant-content layers (LFRLs) are dispersed among high-flame-retardant-content layers (HFRLs). The mechanical, flame retardant and dielectric properties of GF/PP with intumescent flame retardant (IFR/GF/PP) are investigated comparatively under uniform, gradient, and dispersed distributions of the flame retardants. The results demonstrate that non-uniform distribution exhibits superior flame retardant performance compared to uniform distribution. Dispersed distribution enables IFR/GF/PP to attain enhanced mechanical properties and reduced dielectric constants while maintaining excellent flame-retardant properties.

Preparation of phosphorus-doped chitosan derivative and its applications in polylactic acid: Crystallization, flame retardancy, anti-dripping and mechanical properties

The topic of biobased flame-retardant PLA has always been of great interest. In our study, we successfully synthesized a phosphorus-containing chitosan derivative (PCS) and combined it with aluminum hypophosphate (AP) to create an effective flame-retardant PLA system. PCS acted as an enhancer, enhancing the thermal performance, crystallinity, and toughness of PLA/AP. Compared to PLA modified with 12 wt% AP achieving UL-94 V-2 level and 24.3 % of limited oxygen index, PLA containing 3 wt% PCS and 9 wt% AP achieved UL-94 V-0 level and limited oxygen index of 28 %. The system testing studies such as CCT, Raman, XPS, and TG-IR results indicated that PLA/AP/PCS exhibited a dual flame-retardant mechanism of condensed and gas phases.

Synergistic Effect of 4A Molecular Sieve on Intumescent Ternary H-Bonded Complex in Flame-Retarding of Polypropylene

In this study, a ternary hydrogen (H)-bonded complex intumescent flame retardant (TH-IFR) of melamine (ME) · phosphoric acid (PA)…pentaerythritol (PER) was synthesized through hydrothermal reaction. The combination of the synthesized TH-IFR with 4A molecular sieve as the synergist was used for the first time to improve the flame retardancy of polypropylene (PP). The involved structure, morphology, flame retardancy, flame-retarding mechanism and mechanical properties of the prepared PP composites were systematically investigated. The results show that incorporation of 1 wt% synergist 4A shows the optimum synergistic effect, and the flame retardancy and mechanical properties of the flame-retarded (FR) PP composites are significantly improved. Incorporation of 4A could change the pyrolysis process of the entire system and promote the char-forming chemical interaction, thereby further enhancing the flame retardancy of FR PP composite. The synergistically flame-retarding mechanism of 4A is explained by the significantly improved quality and quantity of the solid-phase char layer, which is formed through generation of SiO₂ and Al₂O₃ substances, and also participation of PP macromolecular chains in the final char layer formation during burning. Furthermore, the improved dispersion and compatibility of TH-IFR in the composite is largely beneficial to the improvement of flame retardancy and mechanical properties.