Thermal degradation of polymer-fire retardant mixtures: Part VI—Mechanism of interaction in polystyrene-chloroparaffin mixtures

In mixtures of polystyrene with a fire retardant chloroparaffin, the rate of volatilisation of the polymer is initially increased during the thermal dehydrochlorination of the additive. In the residue which results, the volatilisation of polystyrene occurs at a lower rate than when it is heated alone. The mechanisms of the reactions which occur in the mixture are discussed and related to the fire retardant action of the chloroparaffin.     

Thermal degradation of polymer-fire retardant mixtures: Part IV—Mechanism of fire retardancy in polypropylene-chlorinated paraffin mixtures

From oxygen and nitrous oxide indices of polypropylene-chlorinated paraffin mixtures it can be deduced that, in addition to the flame poisoning effect of HCl eliminated by the chloroparaffin, the lower flammability of the volatile products formed by thermal degradation of polypropylene heated in the presence of this additive seems to contribute to its fire retardance activity.     

Thermal degradation of fire retardant chloroparaffin-metal compound mixtures: Part III—A comparison of the behaviours of antimony trioxide and bismuth compounds

The characteristics of the evolution of the flame inhibitors HCl and metal chlorides from thermally degrading mixtures of a chloroparaffin and antimony trioxide or Bi compounds are compared with reference to the behaviour of these mixtures as fire retardant additives for polymers.     

Thermal degradation of polymer-fire retardant mixtures—Part I: Polypropylene-chlorinated paraffin. Evidence of interactions

Evidence is given that the thermal behaviour of a mixture of polypropylene and a fire retardant chlorinated paraffin (Cl 70%) is not the sum of their individual behaviours. An interaction is shown to take place in the degrading mixtures which is related to the low temperature dehydrochlorination step of the chloroparaffin. This occurs at temperatures at which pure polypropylene is stable and leads to an increase in the overall rate of volatilisation of the mixtures compared with that of the separate components. A partial overlapping of volatilisation of polymer and additive, which otherwise degrade in two well separated temperature ranges when heated alone, is observed.The relevance of these observations to the mechanism of fire retardance is discussed.     

Thermal degradation of polymer-fire retardant mixtures: Part III—Degradation products of polypropylene-chlorinated paraffin mixtures

When polypropylene is thermally degraded in mixtures with a highly chlorinated fire retardant chloroparaffin, a smaller amount of the lighter hydrocarbon fraction, which is also modified in composition, is evolved compared with that evolved from pure polypropylene. A corresponding increase in the amount of high boiling chain fragments is obtained from the mixtures. This effect can be explained in terms of the interactions which occur between degrading polymer and additive.     

Pyrolysis of polypropylene in the presence of halogenated paraffin and bismuth salt: Some aspects of the degradation mechanism

A study is reported of the condensed-phase reactions which occur during the thermal degradation of mixtures of polypropylene and flame retardant additives.Using the pyrolysis-gas chromatographic-mass spectrometric technique, various mixtures of polypropylene, chloroparaffin and bismuth salt were studied. By comparing the pyrograms with that of pure polypropylene, two effects were noted. Firstly there was a decrease in the amount of low boiling degradation products, which suggests that the unzipping reaction becomes less favoured. Secondly, there was a change in the ratio between the diastereoisomers of tetramer and pentamer, i.e. a reduction of the isomerization caused by hydrogen transfer along the polymer chain.     

石墨烯在聚合物阻燃材料中的应用及作用机理

本文从聚合物基底的阻燃复合材料类别角度出发,详细介绍了石墨烯在不同种类聚合物阻燃材料中的应用现状与作用机理。 包括有:石墨烯/聚乙烯、石墨烯/聚丙烯、石墨烯/聚苯乙烯、石墨烯/环氧树脂、石墨烯/聚氨酯、石墨烯/聚乙烯醇等多种石墨烯/聚合物复合阻燃材料。 同时还介绍了石墨烯基材料在其中所发挥的作用,该综述为发展出新型的石墨烯基/聚合物复合阻燃材料提供了很好的理论支持。     

Date palm fibre filled recycled ternary polymer blend composites with enhanced flame retardancy

Flammability of recycled polypropylene (PP)/low density polyethylene (LDPE)/high density polyethylene (HDPE) ternary blends containing date palm fibres is investigated in this study. Melt blending is used for the composite preparation and the palm fibres induce good mechanical strength to the blend composites. The effect of flame retardant magnesium hydroxide, is studied through the limiting oxygen index analysis and cone calorimeter studies. Morphology of the palm fibres in presence of fire retardant reveals interesting facts of base hydrolysis. Since the polymers used are recycled ones and the fibres are obtained from the date palm leaves, the whole composite manufactured stands as low cost, less energy consuming and environmental friendly. Though the flame retardant reduced the mechanical properties, the palm fibres strengthened the whole composite thus helping to achieve the flame retardancy and mechanical properties simultaneously. Flame retardancy is correlated with the thermal degradation and thermal conductivity of the blend fibre composites as well.     

Thermal degradation of fire retardant chloroparaffin-metal compound mixtures: Part II—Bismuth compounds

The mechanisms of reactions which occur on heating mixtures of Bi compounds and a chloroparaffin, which are suitable fire retardant additives for polymers, have been studied.BiCl₃, which is evolved at a high initial rate by reaction of Bi compounds with HCl eliminated by the chloroparaffin, has a strong catalytic effect on the dehydrochlorination process of the chloroparaffin itself. BiCl₃ evolution occurs in a two-stage process: a fast step characterised by a maximum rate at 300°C followed by a slower step which occurs between 300 and 500°C.     

Effect of chlorinated fire-retardant additives on the thermal degradation of polypropylene

Modifications in the thermal degradation mechanism of polypropylene caused by interactions between the degrading polymer, a chloroparaffin and bismuth carbonate (typical fire retardant additives) are studied.Preliminary TVA and pyrolysis-GLC results show that volatilisation of the polymer occurs at lower temperatures with production of a larger proportion of higher boiling chain fragments in the mixture than in the pure polymer.The products of a strongly exothermal reaction occurring when the two additives are heated together, as shown by DTA and TG, could play an important role in modifying the thermal degradation behaviour of polypropylene in the mixture.     

The formation of antimony oxychloride in flame retardant mixtures and its influence on flame retardant efficiency

Interaction of Sb₂O₃ with HCl vapour and chlorine-containing organic flame retardants in the presence and absence of polymers (polypropylene, polyethylene) has been studied at 473–773 K. It has been shown that SbOCl is formed in thermally degrading mixtures in the condensed phase. The influence of SbOCl formation on flame retardant efficiency is discussed.     

Study of the mechanism of intumescence in fire retardant polymers: Part II—Mechanism of action in polypropylene-ammonium polyphosphate-pentaerythritol mixtures

It is shown that, by the addition of a typical intumescent mixture of ammonium polyphosphate and pentaerythritol to polypropylene, the mechanism of intumescence which develops on heating is not significantly affected by dispersion of the intumescent mixture in the polymer. On the other hand, in these mixtures, polypropylene seems to evolve, by thermal degradation, a smaller amount of flammable products than when it is heated alone. The ammonium polyphosphate-pentaerythritol additive is shown to induce fire retardant characteristics in polypropylene by means of a ‘condensed phase’ mechanism.     

Thermal degradation of polymer-fire retardant mixtures—Part II: Mechanism of interaction in polypropylene-chlorinated paraffin mixtures

The thermal degradation of polypropylene is accelerated when it is heated in mixtures with a fire retardant chlorinated paraffin (Cl 70%) whose dehydrochlorination rate is simultaneously reduced.The mechanism proposed to account for this behaviour involves the attack of the chlorine atoms, which propagate the dehydrochlorination reaction, on the tertiary hydrogen atoms of polypropylene with formation of HCl. The kinetic chain length of the dehydrochlorination is decreased and the rate of evolution of HCl is lowered, while the radicals formed on the polypropylene chain lead to its scission and volatilisation.The effects of these reactions on the fire retardant performance of the mixture are discussed.     

Synthesis of a novel hybrid synergistic flame retardant and its application in PP/IFR

A novel inorganic-organic hybrid synergistic flame retardant was prepared by sol-gel reaction and characterized by NMR and FT-IR. It showed that the fire resistance of polypropylene/intumescent flame retardant (PP/IFR) composites could be improved with the combination of hybrid synergistic flame retardant. The char morphology and structure of PP composites were characterized by SEM and Raman spectra. The influence of the hybrid flame retardant on the thermal degradation process of PP composites was analyzed by FT-IR and the rheological behavior of the PP composites was also evaluated. The thermal stability of PP composites was characterized by TGA, weight loss difference and integral procedural decomposition temperature (IPDT). It indicated that the hybrid synergistic flame retardant had good synergistic effect with IFR.     

Synergistic fire retardancy of colemanite, a natural hydrated calcium borate, in high-impact polystyrene containing brominated epoxy and antimony oxide

This study explores for the first time the synergistic fire retardant action of natural hydrated calcium borate, namely the mineral colemanite, which partially replaces antimony oxide in brominated flame retardant high-impact polystyrene compounds. Various antimony oxide to hydrated calcium borate ratios were employed keeping the brominated flame retardant additive at a constant loading level. With partial colemanite substitution for antimony oxide, lower heat release rate, total heat evolved and fire growth index was obtained under forced flaming fire conditions. Synergism was also seen in limiting oxygen index along with maintained V-0 classification in UL-94 tests. Regarding fire behaviour and flammability ratings, a large antimony oxide to calcium borate ratio provided ultimate fire retardant performance whereas magnitudes of synergism in average heat release rate and total heat evolved tend to be higher towards a smaller ratio. Effective heats of combustion and structural/morphological characterization of fire residues ascribed the underlying mechanism demonstrated by hydrated calcium borate to the formation of a consolidated residue that co-operates with the dominant gas phase fire retardancy originating from bromine-antimony synergism. It is thus proposed that coupling is achieved between gas phase and condensed phase modes of action increasing the overall fire retardant effectiveness. Along with enhanced fire retardancy, thermal stability and mechanical properties were satisfactorily maintained with the use of hydrated calcium borate at a variety of loading levels in compounds.     

使用裂解气相色谱对几种阻燃聚丙烯材料热稳定性及阻燃机理的探讨

用裂解气相色谱（PyGC)考察了经三种类型阻燃剂（含磷、含溴、含溴和磷）改性的聚丙烯的热稳定性。利用PyGC-MS法分析不同样品的高温裂角产物,以此来推测阻燃材料受热分解时气相以及凝聚相所发生的反应,推断阻燃机理,分析影响阻燃效果的因素,为阻燃剂的开发提供有益参考。结果证实,它们都影响聚丙烯的热降解。溴系阻燃剂和磷系阻燃剂是分别从气相阻断、凝固相加速成炭实现阻止燃烧的,而磷-溴型阻燃剂同时具备单纯含磷或者含溴阻燃能力。     

Microwave-assisted extraction of decabromodiphenylether from polymers

Contrary to its lower brominated congeners, the flame retardant decabromodiphenylether (DecaBDE) is not banned by the decision 2005/717/EG of the European Union. But the question of the bioavailability and bioaccumulation of this second most used flame retardant worldwide becomes subject of more intense research. In the present study, we developed a microwave-assisted method for the extraction of DecaBDE from polymers. Owing to its main use in electrical and electronic appliances and according to the fire safety standard UL94 V-0, the extraction procedure was carried out for the model compounds polyethylene and polystyrene. Special emphasis has been given to an accurate optimization by an experimental response surface design. Quantification was performed by means of HPLC-DAD. In order to achieve comparable data, extraction was also performed with classic Soxhlet extraction. To compare these results with an independent technique, microwave-induced oxygen combustion and ion chromatography complete this study.     

Microencapsulation of bisphenol-A bis (diphenyl phosphate) and influence of particle loading on thermal and fire properties of polypropylene and polyethylene terephtalate

Microencapsulated flame retardant, bisphenol-A bis (diphenyl phosphate) (BDP), with a silane shell was prepared by sol–gel process with the goal of incorporating them in polymeric matrices by melt blending to improve the flame retardancy of isotactic polypropylene (iPP) and polyethylene terephtalate (PET). The influence of the loading content on thermal transitions has been studied by differential scanning calorimetry (DSC), the thermal stability of the polymer/microcapsules composites has been assessed by thermogravimetric analysis (TGA) and cone calorimetry has been used to study the fire reaction. It was noticed that the microcapsules have a limited influence on the thermal transitions of iPP matrix, but a decrease of the melting and glass transition temperatures was detected for the PET microcomposites. TGA results showed that the addition of microcapsules could improve char formation of the PET systems both in nitrogen and in air atmospheres, whereas only a small improvement of the thermal stability was detected in oxidative atmosphere for the iPP samples. Furthermore, cone calorimeter experiments show that the incorporation of microcapsules in the iPP gives almost no improvement in the iPP fire reaction. However, the microcapsules act as flame retardant in PET reducing the heat release rate during the combustion and the total heat evolved. Therefore, microcapsules can act as a char promoter agent to enhance the fire resistance in the case of PET.     

Preparation of piperazine cyanurate by hydrogen‐bonding self‐assembly reaction and its application in intumescent flame‐retardant polypropylene composites

Piperazine cyanurate (PCA) is designed and synthesized via hydrogen‐bonding self‐assembly reactions between piperazine and cyanuric acid. Chemical structure and morphology of PCA are investigated by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The prepared PCA is combined with ammonium polyphosphate (APP) to prepare flame‐retardant polypropylene (PP) composites. Thermostability, flammability, and combustion characteristics of PP composites are analyzed. The maximum thermal decomposition rate of flame‐retarded PP composites has an apparent reduction compared with that of pure PP, and obvious char is left for this intumescent flame retardant (IFR) system of APP and PCA. A high limiting oxygen index value and UL‐94 V‐0 rating are achieved with addition of APP and PCA. In cone calorimetry test, heat and smoke releases of PP are significantly decreased by this IFR system. Gaseous decomposition products during the thermal decomposition of flame‐retardant composites are studied. Chemical structure and morphology of char residues are analyzed. The results illustrate that APP and PCA have a superb synergistic action in the aspect of improvement in fire safety of PP. A possible flame‐retardant mechanism is concluded to reveal the synergism between APP and PCA.     

Bis(1-propyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-diazene - An innovative multifunctional radical generator providing flame retardancy to polypropylene even after extended artificial weathering

In this work, we report the synthesis and use of an innovative multifunctional radical generator, i.e., bis(1-propyloxy-2,2,6,6-tetramethylpiperidyl)-4-diazene (AZONOR) that alone can effectively provide flame retardancy and self-extinguishing properties to both polypropylene films and plaques. Polypropylene samples containing very low concentrations of 0.25-1 wt% of this additive can successfully pass not only the fire standard tests of DIN 4102 B2 and NF P92-505 but also the more challenging UL94 VTM-2 standard. Besides relative low levels of addition and having no detrimental effect on polypropylene appearance or its mechanical and processing properties another great advantage offered by this flame retardant is its multifunctionality, i.e., high flame retardant durability after artificial weathering. Thus, even after 2000 h of artificial weathering no significant decrease in flame retardant efficacy could be observed.