Mechanical properties and fracture morphology of Al(OH)3/polypropylene composites modified by PP grafting with acrylic acid

A highly efficient gas-dominated and water-resistant flame retardant for non-charring polypropylene

In this work, a novel mono-component and gas-dominated flame retardant, named DPPIP, was prepared through an amidation reaction of diphenylphosphinyl chloride and piperazine, and used to flame retard PP.

Flame Retarded PE with MH/ATH/Microencapsulated Red Phosphorous and its Toughening by Polymeric Compatibilizers

Non-halogen flame retarded polyethylene (PE) can be prepared by filling metallic hydroxides magnesium hydroxide (MH) or aluminium hydroxide (ATH), the mechanical properties of polymer composites will decline greatly when filling much more inorganic particles. Selecting microencapsulating particles, suitable synergistic agents or compatibilizers are good methods for improving the combination performance of composites. In this study, microencapsulated red phosphorous (MRP) was synthesized by using melamine-formaldehyde resin through in-situ polymerization, and used as a synergistic agent of MH and ATH, and the best proportion of three flame retardants was studied in detail. Results showed that flame retarded PE had a better combination performance when filling with 45 wt% compound flame retardants of MRP, MH and ATH under the weight ratio of 46/46/8. In order to improve the mechanical performance of composite, two polymeric compatibilizers POE-g-MAH and EPDM-g-MAH were selected to toughen the flame retarded PE composite. Results showed the flame resistance and mechanical properties of composites improved greatly with an increase of compatibilizer content, under the same condition, POE-g-MAH has a better contribution on the flame resistance and EPDM-g-MAH has a better toughening effect. The best flame retarded PE composite can be obtained by filling with 45 wt% compound flame retardants and 10 wt% EPDM-g-MAH.

An efficient mono-component polymeric intumescent flame retardant for polypropylene: preparation and application

We found in our previous study that ethylenediamine- or ethanolamine-modified ammonium polyphosphates could be used alone as an intumescent flame retardant for polypropylene (PP), but their flame-retardant efficiency was not very high. In this present work, a novel highly-efficient mono-component polymeric intumescent flame retardant, piperazine-modified ammonium polyphosphate (PA-APP) was prepared. The oxygen index value of PP containing 22 wt % of PA-APP reached 31.2%, which increased by 58.4% compared with that of PP with equal amount of APP, and the vertical burning test (UL-94) could pass V-0 rating. Cone calorimeter (CC) results indicated that PP/PA-APP composite exhibited superior performance compared with PP/APP composite. For PP containing 25 wt % of PA-APP, fire growth rate (FGR) and smoke production rate (SPR) peak were reduced by 86.4% and 78.2%, respectively, compared with PP blended with 25 wt % APP. The relevant flame-retardant mechanism of PA-APP was investigated by Fourier transform infrared spectroscopy etc. The P-N-C structure with the alicyclic amine was formed during the thermal decomposition of piperazine salt (-NH2(+)-O-P-), and the rich P-N-C structure facilitated the formation of stable char layer at the later stage, consequently improving the flame-retardant efficiency of APP.

Cellular Structure of EVA/ATH Halogen-free Flame-retardant Foams

Composites of etylene vinyl acetate (EVA)/aluminum trihydroxide (ATH) (up to 70 wt%) were foamed to create new materials with good fire retardancy properties and low weight, proving the feasibility of developing cellular structures when high levels of halogen-free flame retardants (HFFR) are included. An experimental study was carried out to explore the effects of chemical composition on cellular structure as well as the effect of structure on thermal stability, mechanical and combustion properties. Sample fabrication was carried out using an improved compression molding route consisting of polymer compounding, precursor preparation and foaming under pressure. The polymer matrix consisted of EVA as well as certain amount of linear low-density polyethylene-maleic anhydride as coupling agent. The inorganic filler used was ATH ranging from 0 wt% to 70 wt%. Furthermore, azodicarbonamide was used as chemical blowing agent. Foamed samples with cell sizes below 100 µm were produced. These samples showed similar fire retardancy than their solid precursors. The compatibilization was proved indispensable to achieve a good adhesion between mineral filler and polymer and to improve the cellular structure. The increase of the amount of filler has an interesting effect on the cellular structure, going from a closed-cell (up to 50 wt% of ATH) to an open-cell cellular structure (60 wt% of ATH or more). The feasibility of producing HFFR cellular materials has been demonstrated as a result of this investigation, leading to a notable reduction of material compared to the solid one and to new properties which can result in new applications.

Cellular Structure of Halogen-Free Flame Retardant Foams Based on LDPE

Composites of LDPE/ATH (up to 70 wt.%) were foamed to create new materials with good fire retardancy properties and low weight, proving the feasibility of developing cellular structures when high levels of inorganic fillers are included. An experimental study was carried out to explore the effects of chemical composition on cellular structure as well as the effect of structure on their thermal, mechanical and combustion properties. Samples fabrication was carried out using an improved compression moulding route consisting of polymer compounding, precursor preparation and foaming under pressure. The polymer matrix consisted of low density polyethylene as well as certain amount of LLDPE-g-MAH as compatibilizer agent. The inorganic filler used was aluminium trihydroxide (ATH) ranging from 0 wt.% to 70 wt.%. Furthermore, azodicarbonamide (ADC) was used as chemical blowing agent.

Foamed samples with cell sizes below 100 microns were produced. These samples showed similar fire retardancy than their solid precursors. The compatibilization was proved indispensable to achieve a good adhesion between mineral filler and polymer and to improve the cellular structure. The increase of the amount of filler has an interesting effect on the cellular structure, going from a closed-cell (at low contents) to an open-cell (at higher contents) cellular structure.

As a result of this investigation, halogen-free flame retardant cellular materials were processed, leading to a notable reduction of material compared to the solid one and to new properties which can result in new applications.