Aluminum Diethylphosphinate Research Articles

Synergy between piperazine pyrophosphate and aluminum diethylphosphinate in flame retarded acrylonitrile-butadiene-styrene copolymer

Acrylonitrile-butadiene-styrene (ABS) copolymer was combined with piperazine pyrophosphate (PAPP) and aluminum diethylphosphinate (AlPi) to prepare the flame retarded ABS (FRABS) composites by melt blending method. The PAPP/AlPi mixture with a mass ratio of 4:1 achieved an optimum synergy at a 25 wt.% flame retardant loading. The relevant composite (FRABS-3) reached the UL-94 V-0 rating (3.2 mm) and got a limiting oxygen index (LOI) of 30.8%. The synergistic flame retardancy mechanism of PAPP and AlPi was investigated using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer coupled with an FTIR spectrometer (TG-FTIR), cone calorimeter test (CCT), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The synergism is based primarily on the Lewis acid-base interactions between PAPP and AlPi. The interactions lead to the formation of a cohesive, uniform, and thermally stable char layer before ABS starts to decompose. The barrier effect of the high-quality char layer plays a dominant role in reducing the flammability of FRABS-3. Furthermore, fuel dilution and flame inhibition effects of the evolved gases also contribute to the superior flame retardancy of FRABS-3 to some extent.

Flame Retarded Rigid Polyurethane Foams Composites Modified by Aluminum Diethylphosphinate and Expanded Graphite

Rigid polyurethane foam (RPUF) was an organic porous material, which was applied in many fields for excellent thermal insulation and mechanical properties, especially in building insulation. However, the poor fire performance significantly suppresses its further application. In this work, aluminum diethylphosphinate (ADP) combined with expanded graphite (EG) to form a synergistic flame retarded system, which was introduced to fabricate flame retarded rigid polyurethane foam composites (FR-RPUF) by one-step water-blown method. Furthermore, thermal insulation, thermal stability, fire performance, and decomposition products of RPUF and FR-RPUF composites were systematically investigated. It was found that FR-RPUF composites possessed LOI of 25.9 vol% with V-1 rating in UL-94 test when 10 php of ADP and 20 php of EG were added, which were better than RPUF composites with ADP or EG added alone. MCC test showed that RPUF/ADP24/EG6 had the lowest PHRR value of 159.85 W/g, which was 52.01 W/g lower than that of pure RPUF. Gas phase products investigation implied that the combination of ADP and EG could decrease toxic and combustible gases intensities, thus significantly enhancing fire safety of FR-RPUF composites. SEM test indicated that ADP and EG promoted the formation of dense and continuous char residue, which significantly inhibited heat and substance transfer in combustion, thus significantly enhancing fire performance of FR-RPUF composites.

Preparation and properties of modified aluminum diethylphosphinate flame retardant for low‐density polyethylene

AbstractTo improve the flame retardancy of low‐density polyethylene (LDPE) and mechanical properties of LDPE composites, phenol‐formaldehyde aluminum diethylphosphinate microcapsules (PF@ADP) was prepared by in‐situ polymerization with phenol‐formaldehyde (PF) resin as the wall material and halogen‐free flame‐retardant aluminum diethylphosphinate (ADP) as the core material. The effects of PF@ADP on flame retardancy and mechanical properties of LDPE were investigated by methods of combustion experiments, mechanical analysis, thermogravimetric analysis (TGA), and smoke density analysis. The results indicated that, compared with ADP/LDPE composites, the flame retardancy and mechanical properties of PF@ADP/LDPE were obviously improved. With the addition of 20 wt% PF@ADP (PF:ADP = 3:7), the limit oxygen index (LOI) of LDPE composites increased to 30.7% and UL‐94 reached V‐1 grade. The tensile strength and elongation at break reached 12.5 MPa and 431.2%, which was 20.2% and 23.1% higher than that of ADP/LDPE with the same addition. The addition of PF@ADP was beneficial to the smoke suppression of LDPE.

A comparison of developmental toxicity of brominated and halogen-free flame retardant on zebrafish

Brominated diphenyl ethers (BDEs) are halogenated flame retardants. Several concerns related to persistence and toxicity of BDEs have been resulted in a growing need of BDEs replacement. The use of halogen-free flame retardants (HFFR) has increased as a safer alternative, but little information is available on their toxic potential for environmental health and for developing organisms. Therefore, the aim of this study was to evaluate and compare the toxicity of three congeners of BDEs (BDE-47, BDE-99 and BDE-154) with an HFFR (aluminum diethylphosphinate, ALPI) on zebrafish (Danio rerio) by assessing endpoints of lethality, sub-lethality and teratogenicity at the earlier stages of development. The highest tested concentration of BDE-47 (12.1 mg/L) induced pericardium and yolk sac edemas that first appeared at 48 h post-fertilization (hpf) and then were mostly reabsorbed until 144 hpf. BDE-47 also showed a slight but non-significant tendency to affect swim bladder inflation. The rate of edemas increased in a concentration-dependent manner after exposure to BDE-99, but there were no significant differences. In addition, the congener BDE-99 also presented a slight and non-significant effect on swim bladder inflation, but only at the highest concentration tested. Regarding BDE-154 exposure, the rate of edemas and swim bladder inflation were not affected. Finally, in all ALPI exposure concentrations (0.003 up to 30 mg/L), no sub-lethal or teratogenic effects were observed on developing organisms until 96 hpf. Although further studies are needed, our results demonstrate that when comparing the developmental toxicity induced by flame retardants in zebrafish, the HFFR ALPI may be considered a more suitable alternative to BDE-47.

Degradation mechanism and flame retardancy of aluminum phosphonate in glass fiber-reinforced poly(butylene terephthalate)

In an attempt to investigate the flame-retardant effectiveness of aluminum phosphonate on glass fiber-reinforced poly(butylene terephthalate) (GF-PBT), aluminum monomethyl methane phosphonate (MMAlPo) was synthesized. The thermal degradation and flame-retarding performance were studied, and the results were compared with aluminum diethylphosphinate (DEAlPi) which its commercial name is aluminum phosphinate. From TGA, SEM, and FT-IR experiments, it is found that the gas-phase action is dominant for MMAlPo due to the formation of O–P● and P–O· radicals coming from the cleavage of C–P and C–O linkages, while DEAlPi acts mainly in the gas phase along with minor contribution from the condensed phase. The synergism of melamine polyphosphate (MPP) in combination with MMAlPo or DEAlPi was also investigated, and it was found that MPP does not show any synergistic effect with MMAlPo, while a slight synergism is obtainable with DEAlPi. The reason for this finding is discussed related to the differences in thermal degradation mechanism between MMAlPo and DEAlPi.

The advancement of bis(2-hydroxyethyl)terephthalate recovered from post-consumer poly(ethylene terephthalate) bottles compared to commercial polyol for preparation of high performance polyurethane

The behavior of rPUf (polyurethane foam derived from bis(2-hydroxyethyl) terephthalate (BHET) recovered from post-consumer poly(ethylene terephthalate)-PET bottles) and cPUf (polyurethane foam based on a commercial polyol) were evaluated by comprehensive characterizations, and their thermal stabilities, flammabilities, and physical properties were compared. Without using a flame retardant, rPUf passed the UL-94HB standard, whereas cPUf burned rapidly to the holding clamp. Various formulations of rPUf and cPUf with established eco-friendly fire retardants (FRs), including triphenyl phosphate, aluminum diethylphosphinate, and aluminum trihydroxide, exhibited notably higher fire resistance. The differences between the experimental and calculated densities showed the effectiveness of the foaming process. A larger difference indicated that the FR improved the foaming process more. The BHET structure contains an aromatic moiety that strongly enhanced the compressive strength and protected the rPUf/FRs from biodegradation, as evidenced by sorption isotherm experiments. For that reason, the rPUf/FRs could be used as building materials, especially under high humidity conditions. These are the advantages of BHET over the commercial polyol for PUf preparation. Chemical recycle of post-consumer PET bottles to produce high performance PUf could be applied on an industrial scale and then it creates the sustainable recycling industry.

Isothermal pyrolysis investigation of aluminum diethylphosphinate mixed as a flame retardant additive into ultra-high molecular weight polyethylene

Aliphatic polymers such as polyethylene or polypropylene are widely used in spite of their high flammability and forces the introduction of flame retardants (FR), e.g. metal phosphinates, into the polymers. These flame retardants usually act in the condensed phase or may influence the gas phase mechanism of combustion. However, the modes of action are not yet understood in detail and require increasing research. In this study a contribution to the latter is made. The thermal decomposition behavior of aluminum diethylphosphinate (AlPi) as FR, mixed in ultra-high molecular weight polyethylene (UHMWPE) is investigated here by molecular beam mass spectrometry (MBMS) in an oxygen-free atmosphere. The isothermal pyrolysis experiments for this system have been systematically studied by first concentrating on each neat compound, FR and polymer, respectively, followed by the analysis of doped polyethylene blends. The aim is to detect phosphorus-containing species in the gas phase, which is the minimum requirement for a gas phase active FR. It was found that the main product of AlPi is diethylphosphinic acid, which subsequently degrades to lighter species or dimerizes. In the mixture, although the AlPi decomposition is influenced by the polymer in the condensed phase, most of the species responsible for a flame suppressant effect are still present in the gas phase.

Novel metal complexes as potential synergists with phosphorus based flame retardants in polyamide 6.6

Aluminium (AlW), tin (II) (SnW) and zinc (ZnW) tungstates were previously found to increase char formation in polyamide 6.6 (PA66), but have never before been studied for their potential as synergists when present with phosphorus-containing (PFRs) flame retardants. We investigate this gap in the scientific knowledge in this publication. Tungstate-PFR interactions of PA66 composites were investigated by thermal analysis, limiting oxygen index (LOI), UL94, cone calorimetry and evolved gas analysis (TGA-FTIR).Of the three tungstates, AlW in the presence of aluminium diethylphosphinate (AlPi) or a mixture of AlPi and melamine polyphosphate (MPP), promotes the highest level of flame retardancy in terms of a balance of high LOI, V-rating and TGA residual char in air at 500 °C and reduction in cone calorimetric peak heat release rate (RPHRR = 80%). This observation has been related to AlW having the highest Lewis acidic properties. While zinc tungstate displays the lowest levels of interaction with either PFR, it shows significant smoke suppressant properties.Elemental analysis of cone calorimetric chars suggests that while some loss of phosphorus occurred from SnW/AlPi/MPP-containing composites, most likely via volatile diethyl phosphinic acid formation, nearly 10% reduction also occurred in the Sn/W molar ratio indicating some volatilisation of tin. The TGA (in air)-FTIR results for carbon dioxide, ammonia and hydrocarbon fuel species evolution enabled discussions of the effect that each tungstate had on the flame retardant mechanisms operating.

Analysis of mechanical properties and distribution of deformation during the shear of polymer-fiber composites containing flame retardants

The work examined the effect of flame retardant addition to the epoxy resin powder matrix on the mechanical properties of composites reinforced with biaxal glass fabric. Two flame retardant systems were used to modify the epoxy resin: (1) melamine polyphosphate (MPP) and aluminum diethyl phosphinate (AlDPi); (2) ammonium polyphosphate (APP) and dipentaerythritol (DPE). The flame retardant content was 25 wt %. In addition, individual compositions also contained 15 wt % of zinc borate (ZB). Tensile, bending and shear tests for the obtained composites were performed. Furthermore, using the digital image correlation method, an analysis of local strains on the sample surface during shear test was carried out. The obtained results indicate, that the amount and type of flame retardant affects the mechanical properties of the composites. Among the tested systems, the best results were obtained for a composite containing 18 wt % ammonium polyphosphate and 7 wt % dipentaerythritol. Compared to the reference sample, among others, the shear stress and shear modulus increased by 25.0 and 39.7%, respectively. In turn, a clear deterioration of the tested parameters was observed in the case of a composite with a matrix containing 15 wt % of AlDPi, 10 wt % of MPP and 15 wt % of ZB, because, compared to unmodified composite, the flexural, tensile and shear stress were reduced by 50.9, 53.5 and 34.8%, respectively.

Efficient flame retardant interplay of unsaturated polyester resin formulations based on ammonium polyphosphate

The flame retardant effects of ammonium polyphosphate (APP) in combination with different mineral flame retardants as well as the combination of APP and phosphorus based flame retardants in unsaturated polyester resin was investigated. Flammability and thermal stability of unsaturated polyester (UP) composites were evaluated with UL-94 vertical burning, thermogravimetric analysis (TG) and cone calorimetry. The morphology of char residues was examined via scanning electron microscopy (SEM). An interaction between APP and phosphinate salts was observed. A combination of 20 wt-% APP and aluminum diethylphosphinate (AlPi) passed UL 94 V-0 classification. In contrast the combination of APP and mineral flame retardants did not show sufficient burning behavior in UL 94 vertical burning test. Furthermore, PHRR and THR was reduced by introduction of phosphinate salts or mineral flame retardants, compared with a formulation containing solely APP. SEM of the residues showed that the combination of APP and the phosphinate salts forms a though and dense residue that can protect underlying material. An incorporation of mineral fillers and APP leads to a fragile residue.

Fire resistance and mechanical properties of powder-epoxy composites reinforced with recycled glass fiber laminate

In this article the effect of type and content of fractions of recycled glass fiber reinforced plastics (GFRP) on the mechanical properties and flame resistance of epoxy composites (EP) were investigated. For this purpose, post-production waste of glass fabric reinforced laminate with epoxy matrix containing 15 wt % of aluminum diethylphosphinate (AlDPi), 10 wt % of melamine polyphosphate (MPP) and 15 wt % of zinc borate (ZB) was ground and sieved to obtain four fractions of grain size: >1 mm (A), 1–0.5 mm (B), 0.25–0.5 mm (C) and

Preparation and Characterization of DOPO-Functionalized MWCNT and Its High Flame-Retardant Performance in Epoxy Nanocomposites.

In this work, functionalized multi-walled carbon nanotubes (MWCNT) were synthesized by the reaction between acylated MWCNT and 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB). The obtained MWCNT-ODOPB was well dispersed into epoxy resins together with aluminum diethylphosphinate (AlPi) to form flame-retardant nanocomposites. The epoxy resin nanocomposite with phosphorus content of 1.00 wt % met UL 94 V-0 rating, exhibited LOI value of 39.5, and had a higher Tg compared to neat epoxy resin, which indicates its excellent flame retardant performance. These experimental results indicated that MWCNT-ODOPB was a compatible and efficient flame retardant for epoxy resins. Moreover, cone calorimeter analysis showed that the peak heat release rate (pHRR), total heat release (THR) values, and CO2 production profiles of the composites decreased with an increase in the additional amount of phosphorus.

Anti-flammability, mechanical and thermal properties of bio-based rigid polyurethane foams with the addition of flame retardants.

Adding efficient and environmentally friendly flame retardants to polyurethane foams is the preferable way to improve their flame resistance ability. In this work, bio-based rigid polyurethane foams (RPUFs) were prepared with the addition of dicyclohexyl aluminium hypophosphate (DAH) or aluminium diethyl phosphinate (ADP) as the flame retardant. The mechanical properties, thermal degradation and flammability behavior of the obtained RPUFs were evaluated by means of compressive strength tests, thermogravimetry analysis, vertical burning test and scanning electron microscopes. The characterization results indicate that, with the same content of flame retardant, the compressive strength at the deformation of 10% for each RPUF prepared with the addition of DAH is higher than that of the foams with ADP addition, which fully meets the specifications for building insulation materials. Moreover, the average flame height of each RPUF with the addition of flame retardants is less than 250 mm, whereas the average burning time of RPUF with 15 wt% addition of DAH is only 4.4 s, far less than that (12.5 s) of the foam with the same addition amount of ADP. The RPUFs with DAH addition have the potential advantages for thermal insulation applications in various fields.

Synergistic Effects of Aluminum Diethylphosphinate and Melamine on Improving the Flame Retardancy of Phenolic Resin

A series of novel flame retardants (aluminum diethylphosphinate and melamine) were used to improve the fire performance of phenolic resin. Fourier transform infrared spectroscopy (FTIR) was used to characterize the modification results. Thermo-gravimetric analysis (TGA) was used to study the thermal decomposition of phenolic resin system, and the flame retardancy of phenolic resin system was tested by vertical combustion test (UL-94) and limiting oxygen index (LOI). The combustion properties of modified phenolic resin were further tested with a cone calorimeter(CCT). Finally, the structure of carbon residue layer was measured by scanning electron microscopy (SEM). The results show that with the introduction of 10 wt % aluminum diethylphosphinate in phenolic resin, the LOI reaches 33.1%, residual carbon content increase to 55%. The heat release rate (HRR) decreased to 245.6 kW/m2, and the total heat release (THR) decreased to 58.6 MJ/m2. By adding 10 wt % aluminum diethylphosphinate and 3 wt % melamine, the flame retardancy of the modified resin can pass UL-94 V-0 flame retardant grade, LOI reaches 34.6%, residual carbon content increase to 59.5%. The HRR decreases to 196.2 kW/m2 at 196 s, relatively pure phenolic resin decreased by 35.5%, and THR decreased to 51 MJ/m2. Compared with pure phenolic resin, the heat release rate and total heat release of modified phenolic resin decreased significantly. This suggests that aluminum diethylphosphinate and melamine play a nitrogen-phosphorus synergistic effect in the phenolic resin, which improves the thermal stability and flame retardancy of the phenolic resin.

Effect of Thermal Conductive Fillers on the Flame Retardancy, Thermal Conductivity, and Thermal Behavior of Flame-Retardant and Thermal Conductive Polyamide 6.

In this work, polyamide 6 (PA6) composites with improved flame retardancy and thermal conductivity were prepared with different thermal conductive fillers (TC fillers) such as aluminum nitride (AlN) and boron nitride (BN) in a PA6 matrix with aluminum diethylphosphinate (AlPi) as a fire retardant. The resultant halogen-free flame retardant (HFFR) and thermal conductive (TC) PA6 (HFFR-TC-PA6) were investigated in detail with a mechanical property test, a limiting oxygen index (LOI), the vertical burning test (UL-94), a cone calorimeter, a thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology of the impact fracture surface and char residue of the composites were analyzed by scanning electron microscopy (SEM). It was found that the thermal conductivity of the HFFR-TC-PA6 composite increased with the amount of TC fillers. The TC fillers exerted a positive effect for flame retardant PA6. For example, the HFFR-TC-PA6 composites with the thickness of 1.6 mm successfully passed the UL-94 V-0 rating with an LOI of more than 29% when the loading amount of AlN-550RFS, BN-SW08 and BN-NW04 was 30 wt%. The morphological structures of the char residues revealed that TC fillers formed a highly integrated char layer surface (without holes) during the combustion process, as compared to that of flame retardant PA6/AlPi composites. In addition, the thermal stability and crystallization behavior of the composites were studied.

An efficient synergistic system for simultaneously enhancing the fire retardancy, moisture resistance and electrical insulation performance of unsaturated polyester resins

Unsaturated polyester resins (UPR) are usually used in the field of electronic appliances, but their inherent flammability and hygroscopicity severely limit their wide application. In this research, dimelamine pyrophosphate (DMPY) was synthesized and constituted a synergistic flame retardant system (FRs) with aluminum diethylphosphinate (ADP). The FRs was applied to flame retarded UPR thermosets and the fire retardancy, moisture resistance, mechanical properties and flame retarded mechanisms of UPR/FRs were comprehensively investigated. When as low as 15 wt% FRs was incorporated, UPR/FRs achieved UL-94 V-0 rating during vertical burning tests and the limiting oxygen index value reached 27.9%. FRs stimulated UPR matrix to form uniform, stiff and dense char layer on materials surface during combustion process. Besides, the phosphine and phosphine oxygen radicals and inert gases generated from FRs exerted the inhibition and dilution effect in gas phase. Thus, the heat release and effective heat combustion of UPR/FRs were conspicuously suppressed. Moreover, UPR/FRs retained satisfactory flame retardancy and mechanical performance after water resistance tests. The moisture resistance of UPR/FRs was evidently enhanced compared with UPR and it led to the maintenance of electrical insulation properties of water treated UPR/FRs. Overall, the superior fire safety, moisture resistance and electrical insulation performance promised the flame retardant UPR thermosets crucial application values in the key areas.

The study on flame retardancy synergetic mechanism of magnesium oxide for PA66/AlPi composite

The flame retardant plays extraordinary important role in the most commonly used polymer materials of polyamide 6,6 (PA66). In this work, micron-sized magnesium oxide (MgO) as a synergist was used to combine with aluminium diethylphosphinate (AlPi) to synergistically enhance the flame retardancy of PA66. The synergetic system by AlPi and MgO improved the flame retardancy of PA66 matrix when the total loading amount only was 10 wt%. The LOI value of the composite was as high as 32.3% and the sample in vertical burning testing obtained UL-94 V-0 rating with the 1.6 mm thickness. The cone results of PA66/AlPi/MgO composite, such as HRR and THR, indicated that the AlPi/MgO synergetic system effectively reduced the fire hazard. The MgO reacted with diethylphosphinic acid produced by the degradation of AlPi to create the magnesium phosphate during the burning, which promoted the formation of char yield and enhanced the thermal stability of PA66 material. The microstructure of char residues exhibited that the char layer became more compact and homogeneous on the surface of PA66 during burning, which was also benefit to efficiently protect the composites from heat and oxygen. This work provided a new method of using synergetic system to enhance the flame retardancy of PA66 materials.

Excellent Fireproof Characteristics and High Thermal Stability of Rice Husk-Filled Polyurethane with Halogen-Free Flame Retardant.

The thermal stabilities, flame retardancies, and physico-mechanical properties of rice husk-reinforced polyurethane (PU–RH) foams with and without flame retardants (FRs) were evaluated. Their flammability performances were studied by UL94, LOI, and cone calorimetry tests. The obtained results combined with FTIR, TGA, SEM, and XPS characterizations were used to evaluate the fire behaviors of the PU–RH samples. The PU–RH samples with a quite low loading (7 wt%) of aluminum diethylphosphinate (OP) and 32 wt% loading of aluminum hydroxide (ATH) had high thermal stabilities, excellent flame retardancies, UL94 V-0 ratings, and LOIs of 22%–23%. PU–RH did not pass the UL94 HB standard test and completely burned to the holder clamp with a low LOI (19%). The cone calorimetry results indicated that the fireproof characteristics of the PU foam composites were considerably improved by the addition of the FRs. The proposed flame retardancy mechanism and cone calorimetry results are consistent. The comprehensive FTIR spectroscopy, TG, SEM, and XPS analyses revealed that the addition of ATH generated white solid particles, which dispersed and covered the residue surface. The pyrolysis products of OP would self-condense or react with other volatiles generated by the decomposition of PU–RH to form stable, continuous, and thick phosphorus/aluminum-rich residual chars inhibiting the transfer of heat and oxygen. The PU–RH samples with and without the FRs exhibited the normal isothermal sorption hysteresis effect at relative humidities higher than 20%. At lower values, during the desorption, this effect was not observed, probably because of the biodegradation of organic components in the RH. The findings of this study not only contribute to the improvement in combustibility of PU–RH composites and reduce the smoke or toxic fume generation, but also solve the problem of RHs, which are abundant waste resources of agriculture materials leading to the waste disposal management problems.

An insight into gas phase flame retardant mechanisms of AHP versus AlPi in PBT: Online pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry

As is well known, gas phase flame retardant mechanisms are very hard to be understood for the extremely intricate burning process but they are crucial for developing highly efficient flame retardants. Pyrolysis provides a valid way for this purpose because combustion proceeds after it. In this work, the pyrolysis behaviors of aluminum hypophosphite (AHP), aluminum diethylphosphinate (AlPi), poly(1,4-butylene terephthalate) (PBT) and PBT composites (with 10 wt% AHP or AlPi) were investigated by the fragment-free pyrolysis vacuum ultraviolet photoionization time of flight mass spectrometry (PY-PI-TOFMS) at different temperatures in real time. The gas phase flame retardant mechanism of AHP in PBT is proposed to be the flame inhibition effect of PH3, H3PO2 and P4 pyrolyzed from AHP. That of AlPi in PBT is speculated to be phosphorus-containing compounds and a kind of phosphorus radical pyrolyzed from AlPi as flame inhibitors and the promoted pyrolysis of AlPi by PBT matrix to be synchronous with it. The eight-membered cyclic non-covalent adduct of C2H5–(O=)P•–OH radical and a molecule of diethylphosphinic acid via intermolecular double hydrogen-bond interaction can produce PO type radicals more effectively in flame. Thermogravimetric analysis results are in accordance with those of pyrolysis. And the much better gas phase flame retardant effect of AlPi than AHP in PBT concluded from combustion tests are interpreted by pyrolysis results, which provides powerful guidance for developing highly efficient flame retardants.

Industrial-waste agave fibres in flame-retarded thermoplastic starch biocomposites

Flame-retarded biocomposites of thermoplastic starch and natural fibres are successfully processed according to state-of-the-art extrusion and injection moulding. Using agave fibres and henequen fibres recovered from local industrial waste is a convincing contribution to sustainability. A systematically varied set of biocomposites is investigated comprehensively, e.g. electron microscopy is used for characterizing the morphology, rheology for the melt viscosity, tensile and impact resistance for the mechanical properties, thermal analysis for the pyrolysis, UL 94 burning chamber and oxygen index for the flammability, and cone calorimeter for the fire behaviour. Achieving sufficient mechanical properties was not the goal in our pre-competitive study but may be tackled by adding compatibilizer in future. The combination of well-dispersed natural fibres, aluminium diethylphosphinate (AlPi) and a special silicone synergist (Si) is proposed as promising innovative route for V0-classified biocomposites. The flame-retardancy modes of action in the gas phase (fuel dilution and flame inhibition) and in the condensed phase (charring, protective layer formation) are discussed in detail, as is the role of combining the ingredients. This work is a convincing proof of principle of how to prepare industrial-waste fibres biocomposites, to apply the synergistic combination of AlPi and Si for future flame-retarded technical polymer materials that are based on renewable resources and compostable.