Effect of polyphenylsilsesquioxane on the ablative and flame-retardation properties of ethylene propylene diene monomer (EPDM) composite

Polyphenylsilsesquioxane (PPSQ) microspheres with ladder structure synthesized in the laboratory have been incorporated into ethylene propylene diene monomer (EPDM) composite in order to study the effect of PPSQ on the ablative and flame-retardation properties of EPDM composites. The results showed that PPSQ microspheres serve as an effective ablative additive and flame retardant for EPDM composites. Thus, PPSQ greatly improved the ablative properties of EPDM composites, with a 4.8 wt% loading leading to a remarkable reduction in the linear ablation rate of EPDM by about 50%. Moreover, this loading of PPSQ improved the flame retardancy and smoke suppression, and significantly reduced the PHRR of EPDM composite from 504 kW/m² to 278 kW/m². Moderate tensile strength could be obtained and the breaking elongation was improved for the EPDM/PPSQ composites. TGA results showed that PPSQ had little influence on the thermal decomposition of EPDM. SEM, CONE, and TG-FTIR tests showed that the char structure of EPDM composites was the primary factor through which PPSQ affected the ablative and flame-retardation properties of EPDM. The chars formed during the ablation of EPDM composites containing PPSQ had better structural stability and thermal stability, owing to the fact that they were denser, remained intact, and had an ordered arrangement of holes.     

Preparation of 3‐aminopropyltriethoxy silane modified cellulose microcrystalline and their applications as flame retardant and reinforcing agents in epoxy resin

Cellulose microcrystalline (CMC), a linear polysaccharide with glucosidic bond, was successfully extracted from bamboo powder and modified by 3‐aminopropyltriethoxy silane coupling agent (KH550) to prepare KH550‐CMC. The prepared KH550‐CMC, in association with ammonium polyphosphate (APP), was introduced into epoxy resin (EP) by casting process to obtain flame retardant composites. The fire performance evaluation indicated that the presence of 10‐phr APP and 5‐phr KH550‐CMC in EP achieved the maximal LOI value of 28.9%, passed the UL‐94 V‐0 rating, and significantly decreased the peak heat release rate from 1055 kW/m² of neat EP to 286 kW/m². The improved fire performance is due to the improvement of dispersity of CMC in EP matrix and formation of better char layer, thus protecting the matrix effectively. Moreover, the introduction of KH550‐CMC could also partly eliminate the negative influence of flame retardants on the mechanical properties of EP composites due to the strengthening effect of CMC and better interfacial compatibility after modification with KH550.     

Flame retardancy of carbon nanofibre/intumescent hybrid paper based fibre reinforced polymer composites

A hybrid nanopaper consisting of carbon nanofibre (CNF) and/or clay, polyhedral oligomeric silsesquioxane (POSS), ammonium polyphosphate (APP), has been fabricated through the papermaking process. The as-prepared hybrid nanopaper was then incorporated onto the surface of glass fibre (GF) reinforced polymer matrix composites through injection moulding. The morphologies of hybrid nanopapers with and without the polymer resin were characterized with scanning electron microscopy (SEM). The polymer resin penetrated the entire nanopaper under a high-pressure compressed air system. The thermal decomposition behaviour of hybrid nanopapers infused with resin was studied with real-time thermogravimetric analysis/Fourier transform infrared spectrometry (TGA/FTIR). The test results indicate that the addition of clay in the hybrid paper increased the char residues of the nanocomposites. The fire retardant performance of composite laminates incorporating hybrid nanopaper was evaluated by cone calorimeter testing using a radiant heat flux of 50 kW/m². The cone test results indicated that the peak heat release rate (PHRR) decreased dramatically in the case of laminate composites incorporating CNF/clay/APP hybrid paper. However, the extent of reduction of PHRR of the composite laminates incorporated with CNF/POSS/APP hybrid paper was lower. The formation of compact char materials was observed on the surface of the residues and analyzed by SEM and X-ray photoelectron spectroscopy (XPS). The flame retardant mechanisms of hybrid nanopapers in composite laminates are discussed.     

Synergistic effects of organo‐sepiolite and zinc borate on the fire retardancy of polypropylene

Polypropylene (PP)/sepiolite/zinc borate (BZn) composites were prepared by melt extrusion after pre‐modification of sepiolite with cetyltrimethylammonium bromide. The synergistic effects of organo‐sepiolite (OSEP) and BZn on the fire retardancy of PP were studied. X‐ray diffraction and transmission electron microscopy were used to characterize the morphology of the composite. Thermogravimetric analysis, cone calorimetric analysis, limiting oxygen index, and the UL‐94 protocol (Demaisheng technology Co. Ltd.,Shenzhen,China) were used to assess the thermal stability and fire retardancy of the composites. The fire retardancy of PP was greatly improved by introducing OSEP and BZn. The reduction in peak heat release rate for PP/BZn composites at 10% BZn loading is 62% compared with pristine PP, but increased to 78% for PP/10%BZn/10%OSEP composite. Other fire retardant parameters were also improved. The fire performance index of PP/10%BZn/10%OSEP composite was 0.045 sm²/kW compared with 0.014 sm²/kW of pristine PP. The average mass loss rate was 12.1 g/sec/m² for the composite with both additives compared with 30.1 g/sec/m² for pristine PP; the smoke production rate decreased by 37% from 0.117 m²/s of pristine PP to 0.074 m²/s of PP/OSEP/BZn. The char residue of composite increased from 0.6% in pristine PP to 12.19% in the composite. The limiting oxygen index increased from 17.1 in pristine PP to 20.8 in the composite: all the samples could obtain a UL‐94 horizontal burn rating. Copyright © 2013 John Wiley & Sons, Ltd.     

Flammability characteristics and synergistic effect of hydrotalcite with microencapsulated red phosphorus in halogen-free flame retardant EVA composite

The flammability characteristics and synergistic effect of hydrotalcite with microencapsulated red phosphorus (MRP) in halogen-free flame retardant ethylene vinyl acetate (EVA) composite have been studied by cone calorimeter test (CCT), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 test. The results obtained by comparing the flame retardancy of hydrotalcite with magnesium hydroxide (MH) and aluminium hydroxide (AH) for their EVA composites showed that hydrotalcite has higher flame retardant effect than MH and AH at the same loading level. The CCT tests indicated that the heat release rate (HRR) and mass loss rate (MLR) of EVA composite blended with hydrotalcite greatly decreased compared with those blended with MH and AH. The LOI values of EVA/hydrotalcite composites are 3-4% higher than those of the corresponding MH composites at 40-60 wt% loading levels, and 6% higher than that of the corresponding AH composite at 40 wt% loading level. Moreover, the addition of a given amount of MRP apparently resulted in the increase of LOI value and decrease of the HRR and MLR as well the loading of hydrotalcite in EVA blend while keeping the V-0 rating in UL-94 test. However, the smoke release increased during the combustion of EVA/hydrotalcite blend containing MRP.     

The suitability of halloysite nanotubes as a fire retardant for nylon 6

This work presents the first study on the fire behaviour of halloysite nanotubes-nylon 6 composites. The nylon 6-halloysite composites were prepared at 5-30 wt% of halloysite loadings by a simple melt extrusion process. A range of standard fire tests and characterization techniques were used to assess the efficacy and mechanism by which the halloysite nanotubes inhibited the burning of nylon. We found that for such systems, relatively high concentrations of additive (≥15 wt%) were required to achieve the levels of fire retardant property normally associated with nanoclay (or layered silicate) additives. We proposed that the primary mechanism of flame inhibition for halloysite nanotubes was similar to that of conventional nanoclays; however, the ease of composite preparation is an attractive consideration for further development or study of such systems.     

Mechanical and thermal properties and flame retardancy of phosphorus-containing polyhedral oligomeric silsesquioxane (DOPO-POSS)/polycarbonate composites

A novel polyhedral oligomeric silsesquioxane containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-POSS) has been incorporated into polycarbonate (PC) composites in order to study its effect on mechanical and thermal properties and flame retardancy. The mechanical and thermal properties of the DOPO-POSS/PC composites have been investigated by tensile and flexural testing, DSC, and DMA. Slight enhancements of yield stress, and flexural strength and modulus, and obvious decreases of fracture strength and strain of the DOPO-POSS/PC composites were observed with an increase in DOPO-POSS loading. The glass transition temperatures (T_g) of the composites were reduced with increasing DOPO-POSS loading. The morphology of the PC composites was evaluated by SEM, which indicated that the DOPO-POSS was dispersed with a particle size of 100-250 nm in the PC matrix. The thermal degradation behaviour and flame retardancies of PC composites with different DOPO-POSS loadings were investigated by TGA, LOI, UL-94 standard, and cone calorimetry. The composite had an LOI value of 30.5 and a UL-94 rating V-0 when the content of DOPO-POSS was 4%.     

Influence of surface modification of fillers and polymer on flammability and tensile behaviour of polypropylene-composites

An intumescent system consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and natural zeolite (clinoptilolite, Gördes II) as a synergistic agent was used in this study to enhance flame retardancy of polypropylene (FR-PP). Zeolite was incorporated into flame retardant formulation at four different concentrations (1, 2, 5, and 10 wt%) to investigate synergism with the flame retardant materials. Filler content was fixed at 30 wt% of total amounts of flame retardant PP composites. Zeolite and APP were treated with two different coupling agents namely, 3-(trimethoxysilyl)-1-propanethiol and (3-aminopropyl)-triethoxysilane for investigation of the influence of surface treatments on mechanical properties and flame retardant performance of composites. Maleic anhydride grafted polypropylene (MAPP) was used for making polypropylene hydrophilic. Flammability of FR-PP composites was measured by the determination of limiting oxygen index (LOI). The LOI values reached to a maximum value of 41% for mercapto silane treated APP:PER (2:1) PP composite containing 5 wt% zeolite. The tensile strength of composites was increased by the addition of MAPP and elongation at break of composites was increased with silane treatments.     

Failure analysis of plain woven glass/epoxy laminates: Comparison of off-axis and biaxial tension loadings

An experimental study was focused on investigation of the failure properties of plain woven glass/epoxy composites under off-axis and biaxial tension loading conditions. Four fibre orientations (0°, 15°, 30° and 45° with respect to the load direction) were considered for off-axis tests and two biaxial load ratios for biaxial tests to study failure characteristics and mechanism. Four classical polynomial failure criteria - Tsai-Hill, Hoffman, Tsai-Wu and Yeh-Stratton - were analysed comparatively to predict off-axis and biaxial failure strength of the composites. For failure prediction of the plain woven composites under multiaxial tension loads, the Tsai-Wu criterion was modified by introducing an interaction coefficient F₁₂ obtained from 45° off-axis or biaxial tension tests and the Yeh-Stratton criterion was modified with the interaction coefficient B₁₂ = 0 or obtained from the biaxial tension test. The former criterion was found to have higher accuracy. Finally, according to macroscopic and microscopic studies, the failed specimens showed mostly distinct failure with a specific fracture orientation, mainly exhibiting fibre or fabric tensile fracture mode and a combination of matrix cracking and delamination, both in off-axis and cruciform samples.     

Preparation, properties and characterizations of halogen-free nitrogen-phosphorous flame-retarded glass fiber reinforced polyamide 6 composite

Halogen free nitrogen-phosphorous flame retardants (PMOP) were prepared through reaction of melamine and polyphosphoric acid in the presence of flame retardant modifier CM with silicotungistic acid as a catalyst in aqueous solution. FT-IR, XRD, DSC and TGA techniques were used to characterize the reaction product PMOP. The obtained flame retardants were then used to prepare flame retardant (FR) polyamide 6 (PA6) composite reinforced with glass fiber (GF) and the factors affecting the flame retardancy of the material were also investigated. The FR GF reinforced PA6 composite and the obtained charred layers were analyzed by utilizing TGA, SEM, FT-IR and XRD. The properties of the charred layer were connected with the flame retardancy of the corresponding material to reveal the flame retarding mechanism of FR GF reinforced PA6 composite. The experimental results show that PMOP flame retardant consists of melamine polyphosphate, melamine phosphate and possible melamine pyrophosphate. The presence of CM was found to improve the flame retardancy of FR GF reinforced PA6 composite. It was experimentally found that PMOP flame retardant, which is comparatively stable in the range of processing temperatures of PA6, is particularly suitable for flame retarding PA6 reinforced with GF. With increasing the flame retardant content, the flame retardancy of the FR reinforced material is not improved so obviously. However, the increase in the GF content greatly improves the flame retardancy of the composite, because GF greatly increases the char yield of material, decreases the maximal thermal decomposition rate, promotes the formation of charred layer with (PNO)_x structure and greatly increases the strength of the charred layer. The prepared FR GF reinforced PA6 composites have good comprehensive properties with flame retardancy 1.6 mm UL 94 V-0 level, tensile strength 76.8 MPa, Young's modulus 11.7 GPa, Izod notched impact strength 4.5 kJ/m², flexural strength 98.0 MPa and flexural modulus 7.2 GPa, showing a better application prospect.     

Fire behaviour of hybrid filament-wound single and adhesively bonded composites tubes under static pressure

The present work aims to experimentally investigate the fire behaviour of water-filled E glass reinforced thermoset resin hybrid filament-wound composites tubes under static pressure. Heretofore, fire endurance tests have been conducted on single and adhesively bonded tubes manufactured by CTRA Company. Furthermore, internal pressure tests until failure have been performed on the burnt single and burnt joined tubes in order to quantify their abilities to contain the fluid after being exposed to heat flux. A comparison between the pressure behaviour of exposed to fire (burnt) and non-exposed tubes (single and joined) was also inspected. The identification of the fire-induced damage mechanisms of the tubes was performed through optical microscopy, Scanning Electron Microscopy (SEM) and X-ray tomographic observations. Finally, the thermal analysis was carried-out on burnt specimens in order to better understand the multiphysical phenomenon taking place during the fire endurance tests. The experimental results have revealed that the combustion process of both single and joined tubes was described in four steps namely tube heating, resin degradation, ignition and flame decay. Moreover, it was found that no leakage was witnessed on the tubes (single and joined) outer surfaces during the fire endurance tests. The comparison between the pressure behaviour of the burnt single tube and the burnt joined one has proved that the single tube is much resistant under internal pressure loading than the burnt joined tube. Finally, the fire-induced damage included matrix cracking and delamination between the tube plies which was noticed from microscopic observations.     

Synergistic flame retardant effects of nano-kaolin and nano-HAO on LDPE/EPDM composites

A novel flame retardant system composed of nano-kaolin and nano-HAO (nano-sized hydroxyl aluminum oxalate) was used for flame retarding the low density polyethylene (LDPE)/ethylene propylene diene rubber (EPDM) blends. Results of fire testing showed that nano-kaolin and nano-HAO exhibited excellent synergistic effects on the flame retardancy of the LDPE/EPDM composites. When 12 wt% nano-kaolin took the place of 12 wt% nano-HAO in the composites, the LOI of the composites increased from 31.0% to 35.5% and the composites could meet the UL94V-0 standard. Through thermogravimetric and differential thermal analysis (TG-DTA) it was found that nano-HAO mainly affected the degradation of the experimental composites chemically. Meanwhile, results of scanning electronic microscope (SEM) and Fourier transformation infrared spectra (FTIR) of the composites on the char layer revealed that nano-kaolin mainly affected the transfer process physically by aggregating with nano-HAO and thus the synergistic effect on flame retardancy appeared.     

Synergistic fire safety improvement between oyster shell powder and ammonium polyphosphate in TPU composites

In this article, oyster shell powder (OSP) was used as fire safety agent with ammonium polyphosphate (APP) in thermoplastic polyurethane (TPU) composites. The synergistic fire safety improvement between OSP and APP was intensively investigated using limiting oxygen index (LOI), UL‐94, smoke density test (SDT), and cone calorimeter test (CCT). There is a good synergistic effect of reducing the fire hazards when OSP was used with APP in TPU. The peak heat release rate (pHRR) of the sample with 2.0‐wt% OSP and 8.0‐wt% APP decreased to 86.8 kW/m² from 175.7 kW/m² of the sample with only 10.0‐wt% APP. The SDT results showed that the luminous flux of sample OSP2/APP8 was up to 28.9% at the end of experiment with flame, which was much higher than that of pure TPU (1.5%). The thermal stability and thermal decomposition of TPU composites were characterized by thermogravimetric analysis/Fourier infrared spectrum analysis (TG‐IR). The result revealed the inert gasses (including CO₂ and water vapor) produced by the reaction between OSP and APP. A char formed on the surface of composites, hindered the flame spread, reduced the release of combustible gas, and restricted the precursor of smoke into combustion zone.     

Morphology,thermal stability,and flammability of polymer matrix composites coated with hybrid nanopapers

In this study, a hybrid nanopaper consisting of carbon nanofiber (CNF) and polyhedral oligomeric silsequioxane (POSS) or cloisite Na⁺ clay, has been fabricated through the papermaking process. The hybrid nanopaper was then coated on the surface of glass fiber (GF) reinforced polymer matrix composites through resin transfer molding (RTM) process. The morphologies of the hybrid nanopaper and resulting nanocomposites were characterized with scanning electron microscopy (SEM). It can be seen that the nanopaper had a porous structure with highly entangled carbon nanofibers and the polyester resin completely penetrated the nanopaper throughout the thickness. The thermal decomposition behavior of the hybrid nanopapers and nanocomposites was studied with the real‐time thermogravimetric analysis/ flourier transform infrared spectrometry (TGA/FTIR). The test results indicate that the addition of pristine nanoclay increased the thermal stability of the nanopaper, whereas the POSS particles decreased the thermal stability of the nanopaper. The fire retardant performance of composite laminates coated with the hybrid nanopaper was evaluated with cone calorimeter tests using a radiated heat flux of 50 kW/m². The cone calorimeter test results indicate that the peak heat release rate (PHRR) decreased dramatically in composite laminates coated with the CNF‐clay nanopaper. However, the PHRRs of the CNF‐POSS nanopaper coated composite laminates increased. The formation of compact char materials was observed on the surface of the residues of the CNF‐clay nanopaper after cone calorimeter test. The flame retardant mechanisms of the hybrid nanopaper in the composite laminates are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and applications of biscyclic phosphorus flame retardants

The influence of structural effects of organo-phosphorus flame retardants (FRs) on their flame retardant action was investigated. A series of spirobisphosphorus compounds including 3,9-dibutyl-3,9-dioxo-2,4,8,10-tetraoxa-3,9-diphosphaspiro-5,5-undecane were prepared using various synthetic methods such as the Arbuzov reaction. The chemical structure of the product was confirmed by ¹H and ³¹P NMR. Thermogravimetric analysis (TGA) results reveal that these cyclic phosphorus compounds show a single step degradation in the range of 250-400 °C and act in the gas phase rather than in the condensed phase. The obtained products were blended with an acrylonitrile-butadiene-styrene copolymer (ABS) or polycarbonate (PC) and their flame retardant behavior was evaluated using a UL-94 vertical test. V-0 ratings are achieved at 15-35 wt% loading of FR for ABS and at a much lesser amount of loading for PC. In both cases, it is apparent that the flame retardancy is strongly dependent on the P content of the flame retardant.     

Microencapsulation of ammonium polyphosphate with hydroxyl silicone oil and its flame retardance in thermoplastic polyurethane

Microencapsulated ammonium polyphosphate (MAPP) is prepared using hydroxyl silicone oil by in situ polymerization and characterized by XPS. Microencapsulation gives MAPP better water resistance and flame retardance compared with APP in thermoplastic polyurethane (TPU). Thermal stability and fire resistance behavior have been analyzed and compared. The LOI value of the TPU/MAPP composite is higher than that of the TPU/APP composite. The UL 94 rating of the TPU/MAPP composite is V-0 at the 20 wt% additive level, whereas TPU/APP gives V-2 rating at the same loading level. The water resistant properties of the TPU composites are studied. Results of the cone calorimeter and microscale combustion calorimeter experiment show that MAPP is an effective flame retardant in TPU compared with APP.     

Effect of surface chemical modification for aluminum hypophosphite with hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene on the fire retardancy,water resistance,and thermal properties for polyamide 6

The surface chemical modified aluminum hypophosphite (AHP) defined as MAHP was successful prepared through P–H bonds on AHP surface reacted with the aldehyde groups in hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene made in our lab. The wettability of the flame retardants was evaluated by water contact angle tests, and the water contact angle of the prepared MAHP dramatically increased from 0° for AHP to 145°, which indicated the surface modification made the superhydrophilic AHP into superior hydrophobic MAHP. The prepared MAHP and AHP, respectively, incorporated into polyamide 6 (PA6) matrix to prepare flame retardant PA6 composites and the fire retardancy and thermal degradation behavior of flame retardant PA6 composites were investigated by limiting oxygen index, vertical burning test (UL‐94), cone calorimeter, and thermogravimetric analysis tests. The morphologies and chemical compositions of the char residues for PA6 composites were investigated by scanning electron microscopy and X‐ray photoelectron spectroscopy, respectively. The water resistant properties of flame retardant PA6 composites were evaluated by putting the samples into distilled water at 70°C for 168 hr, and the mechanical properties for flame retardant PA6 composites were investigated by the tensile, flexural, and Izod impact strength tests. The results demonstrated that the PA6/MAHP composites successfully passed UL‐94 V‐0 flammability rating, and the limiting oxygen index value was 27.6% when the loading amount of MAHP was 21 wt%. However, there is no rating in vertical burning tests for PA6/AHP composite with the same amount of AHP, which indicated the surface modification of AHP enhanced the flame retardancy efficiency for PA6 composites. The morphological structures and analysis of X‐ray photoelectron spectroscopy of char residues revealed that the surface modification of AHP benefited to the formation of a sufficient, flame retardant elements rich, more compact and homogeneous char layer on the materials surface during combustion, which prevented the heat transmission and diffusion, limit the production of combustible gases, inhibit the emission of smoke and then led to the reduction of the heat release rate and smoke produce rate. The mechanical properties results revealed that the surface modification of AHP enhanced the mechanical properties, especially the Izod impact strength comparing with that of PA6/AHP composites with the same amount of flame retardant. After water resistance tests, the PA6/MAHP composites remained superior flame retardancy and presented continuous and compact char layer after cone calorimeter tests; however, the fire retardancy for PA6/AHP composite obviously decreased, and the char layer was discontinuous with big hole caused by the extraction of AHP by water during water resistance tests. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of natural basalt fiber for EVA composites with nickel alginate‐brucite based flame retardant on improving fire safety and mechanical properties

The natural basalt fiber (BF) was incorporated into EVA composites with environmental‐friendly nickel alginate‐brucite based flame retardant (NiFR), to further improve the flame‐retardant effect and mechanical properties. The flame retardancy of EVA composites were characterized by LOI, UL 94, and cone test. With 55 wt% loading, 3BF/52NiFR had the highest LOI value of 31.9 vol.% in all fiber reinforced composites and pass UL 94V‐0 ratting. And comparing to 55B composite with untreated brucite, 3BF/52NiFR decreased peak of heat release rate by 47.8%, total heat release by 21.9%, and total smoke production by 35.5% and kept more residue 54.0% during cone test. Moreover, 3BF/52NiFR also enhanced the mechanical properties of composites by better compatibility with EVA matrix. BF/NiFR exert synergistic flame‐retardant effect major in promoting charring effect in condensed phase during combustion. The fire‐resisted and rigid BF into the char layer reinforced the intensity of protective barrier which prolonged the residence time of pyrolysis carbonaceous groups degraded from EVA matrix, resulting in less heat and smoke release.     

An efficient and convenient strategy toward fire safety and water resistance of polypropylene composites through design and synthesis of a novel mono‐component intumescent flame retardant

A novel mono‐component flame‐retardant additive poly (dimethylol melamine piperazine pyrophosphate) defined as PDMPP was synthesized from formaldehyde, melamine, and piperazine pyrophosphate. Its chemical structure was well characterized by Fourier transform infrared spectroscopy, ¹³C and ³¹P solid‐state nuclear magnetic resonance, and elemental analysis tests. PDMPP was incorporated into polypropylene (PP) matrix, and the fire‐retardant performance, thermal properties, and water resistance of PP composites were investigated in detail. PP/23 wt% PDMPP composites before and after water resistance tests both achieved UL‐94V‐0 grade during vertical burning tests, and the limiting oxygen index was slightly declined from 26.7% to 26.3%. Small amount of PDMPP was extracted by hot water, and the weight loss percentage was 0.67% during water resistance tests. The piperazine and triazine rings in PDMPP contributed to a much better char‐forming capability, and then a greatly expanded and coherent char residue was generated during combustion and exhibited excellent isolation effect. The heat release rate, carbon monoxide production, and smoke production rate of the flame‐retarded PP composites before and after water resistance tests were effectively suppressed to a low level. Consequently, the introduction of PDMPP apparently improved the fire safety of PP composites as well as excellent water‐resistant performance.     

Simultaneously improving the flame retardancy and mechanical properties for polyamide 6/aluminum diethylphosphinate composites by incorporating of 1,3,5‐triglycidyl isocyanurate

The effect of 1,3,5‐triglycidyl isocyanurate (TGIC) as a synergistic agent on the fire retardancy, thermal, and mechanical properties for polyamide 6/aluminium diethylphosphinate (PA6/AlPi) composites were investigated in detail by limiting oxygen index; vertical burning (UL‐94); cone calorimeter; thermal gravimetric analysis; rheological measurements; and the tests of tensile, flexural, and Izod impact strength. The morphologies and chemical compositions of the char residue were investigated by scanning electron microscopy, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectra. The results demonstrated that AlPi and TGIC exerted an evident synergistic effect for flame retardant PA6 matrix, and the PA6/AlPi/TGIC composites with the thickness of 1.6 mm successfully passed UL‐94 V‐0 rating with the limiting oxygen index value of 30.8% when the total loading amount of AlPi/TGIC with the mass fraction of 97:3 was 11 wt%. However, the samples failed to pass the UL‐94 vertical burning tests when AlPi alone is used to flame retardant PA6 matrix with the same loading amount. The thermal gravimetric analysis data revealed that the introduction of TGIC promoted the char residue formation at high temperature. The rheological measurement demonstrated that the incorporation of TGIC improved the storage modulus, loss modulus, and complex viscosity of PA6/AlPi/TGIC composites comparing with that of neat PA6 and PA6/AlPi composites due to the coupling reaction between TGIC and the terminal groups of PA6 matrix. The morphological structures of char residues demonstrated that TGIC benefited to the formation of more homogenous and integrated char layer with no defects and holes on the surface comparing with that of PA6/AlPi composites during combustion. The higher melt viscosity of composites and the integrated and sealed char layer effectively inhibited the volatilization of flammable gas into the combustion zone and then led to the reduction of the heat release. The results of mechanical properties revealed that the incorporation of TGIC enhanced the mechanical properties for PA6/AlPi/TGIC composites comparing with that of PA6/AlPi composites with the same loading amount of flame retardant caused by the chain extension effect of TGIC. As a result, the flame retardancy and mechanical properties of PA6/AlPi composites simultaneously enhanced due to the introduction of TGIC.