Pengju Liu

Interfacial carbonation for efficient flame retardance of glass fiber-reinforced polyamide 6

Wicking action, a typical physicochemical phenomenon, always causes high flammability of glass fiber (GF)-reinforced thermoplastic polymer composites due to the rapid and oriented flow of the polymer melt along the GF surface to the fire zone. This paper introduces an interfacial carbonation mode to solve the global challenge of flame resistance for these composites. Unlike the conventional bulk flame resistance mode, in which a high load of phosphorus flame retardants must be added and evenly distributed in the polymer matrix and the acid sources released by the flame retardants would catalyze the resin into a continuous and compact carbonate layer (the carbonates distributed in the bulk region are uncombined with the GFs), the interfacial mode enriches flame retardants in the GF-resin interfacial regions where wicking actions occur. After the composite burns, the released phosphorus acids can effectively carbonize the interfacial resin and the formed interfacial carbonate layer combining with the GF will convert the original smooth and high-energy GF surface to an inert and rough carbonate surface. The change of interfacial properties makes the adsorption, wetting, spreading and flow of the polymer melt along the GFs much more difficult, thus greatly weakening the wicking effects and improving the flame retardance efficiency of the composites.

The preparation and application of a graphene-based hybrid flame retardant containing a long-chain phosphaphenanthrene

A novel hybrid flame retardant combining graphene oxide (GO) with long-chain phosphaphenanthrene was fabricated via surface grafting reaction. Taking advantageous of the double barrier effects, including the physical shield contributed by graphene nanoplates during the initial stage and the chemical char contributed by phosphaphenanthrene during the later stage, greatly decreased the release rate of decomposed volatiles from the resin, as well as minimized the release of oxygen and combustion heat. Hence, such hybrid flame retardant can overcome the shortcomings of early acid catalyzed degradation effects caused by conventional flame retardants containing phosphorus. Satisfactory flame retardance was achieved (UL94 V-0 rating) with only 4% addition of the hybrid flame retardant to the epoxy resin laminate. Due to the long-chain and bulky phosphaphenanthrene groups, the interlayer attractive forces of the modified GO were effectively weakened, thus favoring the exfoliation and dispersion of graphene sheets. As a result, the incorporation of the flame retardant slightly enhanced the mechanical properties of the polymer composites, rather than deteriorating them, as occurs with traditional additive flame retardants. As a potential application for graphene, it is believed that the reported hybrid flame retardant has promising future prospect.

Synergistic Flame-retardant Effect and Mechanism of Nitrogen–Phosphorus-Containing Compounds for Glass Fiber-reinforced Polyamide 66

ABSTRACT The system based on aluminum phosphinate (OP) and melamine polyphosphate was applied in flame-retardant glass fiber-reinforced polyamide 66. From a qualitative and quantitative point of view, the incorporation of OP played a positive role in obtaining the homodisperse of flame-retardant particles throughout the composites. A two-step cooling mode during the degradation process was established to play an effective role in absorbing heat to retard the flame spread rate and provide enough time for barrier generation. In condensed phase, the cross-linked structure formed in residue promoted the construction of the high-quality barrier layer. GRAPHICAL ABSTRACT

Influence of Solid-state Shear Milling on Structure and Mechanical Properties of Polypropylene/Polyethylene Blends

ABSTRACT A polypropylene/polyethylene (50/50) blend was prepared at ambient temperature through a solid-phase mechanochemical reactor and is shown to have potential for development as an effective way of recycling mixed plastic waste. The changes of structure and properties of the prepared blend were systematically investigated. It was found that polypropylene and polyethylene phase dimensions significantly reduced and compatibility between phases was enhanced after co-milling. The excellent impact toughness is mainly attributed to the uniform dispersion of the polypropylene and polyethylene phases in the blend and the compatibilization effect of the PP/PE-grafted copolymers produced by the three-dimensional shearing force. GRAPHICAL ABSTRACT