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.     

Thermal degradation and flame retardancy of fumaric acid in thermoplastic polyurethane elastomer

In this paper, fumaric acid (FA) which was a new type of environmental and low‐cost flame retardant was applied for thermoplastic polyurethane elastomer (TPU). The flame‐retardant properties of TPU were tested using limiting oxygen index, cone calorimeter test, smoke density test, and thermogravimetric/Fourier transform infrared spectroscopy. It has been proved that FA could improve the difficulty of the ignition of the sample; the limiting oxygen index value of the sample (FA‐4) increased by 29.7% when 2.0 wt% FA was added to TPU. The cone calorimeter test showed that FA can greatly reduce heat release and smoke production during the combustion process of TPU composites. For example, compared with the pure TPU, the peak heat release rate and total smoke release of the sample (FA‐4) with 2.0 wt% FA were decreased by 50.8% and 51.5% respectively. The results of smoke density test showed that the luminous flux of the samples contained 0.5 wt% FA was increased by 79.2% compared with the pure TPU. The TG results revealed that the sample of FA‐4 had higher char residue content compared with the sample of TPU. The results of thermogravimetric/Fourier transform infrared spectroscopy proved that FA could decrease the initial decomposition temperature for TPU composites and increase the release of CO₂ and H₂O. All results of test illustrated that FA had good flame‐retardant effect on TPU.     

Synergistic effects between iron–graphene and melamine salt of pentaerythritol phosphate on flame retardant thermoplastic polyurethane

A comparison of melamine salt of pentaerythritol phosphate (MPP), and a synergistic agents, iron–graphene (IG) was performed in thermoplastic polyurethane (TPU) by masterbatch‐melt blending on thermal and flame retardant properties. The flame retardant properties of TPU composites were characterized by limiting oxygen index (LOI), UL 94 and cone calorimeter test (CCT). The CCT results revealed that IG can significantly enhance flame retardant properties of MPP in TPU. The peak heat release rate of neat TPU and flame retardant TPU/MPP composites decreased from 2192.6 and 226.7 to 187.2 kW/m² compared with that of TPU containing 0.25 wt% IG. The thermal stability and thermal decomposition of TPU composites were characterized by thermogravimetric analysis (TGA) and thermogravimetric/Fourier infrared spectrum analysis (TG‐IR). The results indicated IG and MPP can improve the thermal stability of TPU. The formation of thermal conductive network by IG can promote the decomposition of MPP into nonflammable melt, which can play the role of heat barrier and restrict the diffusion of fuels into combustion zone and access of oxygen to the unburned fuels. Copyright © 2016 John Wiley & Sons, Ltd.     

Synergistic effects between hollow glass microsphere and ammonium polyphosphate on flame-retardant thermoplastic polyurethane

It is mainly studied that the smoke-suppression properties and synergistic flame-retardant effect of hollow glass microsphere (HM) in flame retardant thermoplastic polyurethane (TPU) composites based on ammonium polyphosphate (APP) as a flame-retardant. Also, the smoke suppression properties and flame-retardant effect were investigated by smoke density test (SDT), cone calorimeter test (CCT), limiting oxygen index, and thermogravimetric analysis, separately. The char residues left after CCT were examined by scanning electron microscopy. The data of SDT shows that HM could effectively decrease smoke production of TPU composites. The results of CCT reveal that the system of APP/HM could reduce heat release rate, smoke production rate, and total smoke release. It is shown that APP/HM is a good system with smoke-suppression and synergistic flame-retardant properties in flame-retardant TPU composites.     

Properties of flame‐retardant TPU based on para‐aramid fiber modified with iron diethyl phosphinate

In this paper, a new type of flame retardant (AF‐Fe) based on para‐aramid fiber (AF) which was modified with iron diethyl phosphinate was applied for thermoplastic polyurethane elastomer (TPU). The flame‐retardant properties of TPU were tested using cone calorimeter test, smoke density test, and thermogravimetric analysis/infrared spectrometry. The cone calorimeter test showed that AF‐Fe can greatly reduce the heat release rate, total heat release, smoke factor, and other parameters of TPU composites compared with the sample of TPU/AF. For example, the pHRR of the composite with 1.0 wt% AF‐Fe was reduced by 15.19% compared with the sample with the same content of pure AF. In addition, the smoke factor of TPU/AFFe3 was reduced by 50.52% and 15.63% compared with TPU0 and TPU/AF respectively. The results of smoke density test showed that the luminous flux of TPU/AFFe3 was increased by 79.26% compared with the sample of TPU/AF. The TG results revealed that the sample with TPU/AFFe3 had lower weight loss rate and higher char residue content at 700°C compared with the sample of TPU/AF.     

Influence of TiO2 particles and APP on combustion behavior and mechanical properties of flame-retardant thermoplastic polyurethane

The experimental investigation on combustion behavior and mechanical properties of flame-retardant thermoplastic polyurethane were performed in the article. By the masterbatch-melt blending technique, the TiO₂ particles were well dispersed in TPU/APP composites. The microscopic morphology structure was observed by TEM and SEM. TEM images of TPU–TiO₂ masterbatch material showed that the grain sizes of TiO₂ particles were 200–400 nm. The SEM result indicated that the TiO₂ particles could enhance compatibility and dispersion of APP in TPU. The mechanical properties of TPU composites were characterized by dynamic mechanical analysis (DMA) and tensile tests, respectively. The DMA results indicated that TiO₂ particles could improve the viscoelastic property of the TPU/APP composites. The tensile strength achieved a significant improvement with addition of TiO₂ particles. APP/TiO₂-5 obtains a better value of 344% than APP-1 (277%). Also, the flame-retardant property and thermal stability of the TPU composites were characterized using cone calorimeter test (CCT) and thermogravimetric analysis (TGA), respectively. The CCT results revealed that TiO₂ particles could enhance the flame-retardant property of APP in TPU. The peak heat release rate of APP/TiO₂-4 containing 0.5% TiO₂ decreased to 157.27 kW m^?2 from 225.5 kW m^?2 of APP-1 sample without any TiO₂. The TiO₂ particles could promote the formation of carbon layers which restrict the diffusion of fuels into combustion zone and access of oxygen to the underlying materials. The TGA results indicated that TiO₂ can improve the thermal stability of TPU/APP composites.

     

Fire‐safe agent integrated with oyster shell and melamine polyphosphate for thermoplastic polyurethane

At present, thermoplastic polyurethane (TPU) is widely used, but there are still many defects in fire safety, such as burning with heavy smoke and dripping. In this article, OS@MP was synthesized by modifying oyster shell (OS) powder with melamine polyphosphate (MP) and then served as fire‐safe agent for TPU. The fire performance of TPU composites were investigated using microscale combustion colorimeter (MCC), cone calorimeter test (CCT), smoke density test (SDT), and thermogravimetric analysis/Fourier transform infrared (TG‐FTIR) spectrum analysis. The MCC and CCT results revealed that OS@MP could reduce the fire hazards of TPU composites. The peak heat release rate (pHRR) of the sample with 10.0 wt% OS@MP decreased to 170.86 kW/m² from 1772.37 kW/m² for pure TPU. And, the SDT results showed that OS@MP could significantly reduce the smoke production of TPU composites. The TG‐FTIR also confirmed that the noncombustible gases (including CO₂, ammonia, and water vapor) produced by OS@MP have played a reinforcing role in TPU composites as well as a char formed on the surface of composites, which could act as a barrier to prevent the heat and air, reinforce the fire safety of TPU.     

Flame retardancy and thermal decomposition behavior of TPU/chitosan composites

The application of chitosan (CS) in new materials is a hot research topic. In this paper, CS was used alone as flame retardant to prepare thermoplastic polyurethane elastomer (TPU) composites. Then, the flame retardancy and thermal decomposition behavior of TPU/CS composites were intensively investigated using cone calorimeter test (CCT), scanning electron microscope (SEM), microscale combustion colorimeter (MCC) test, thermogravimetric analysis/infrared spectrometry (TG‐IR), and gas chromatography‐mass spectrometry (GC‐MS). The results showed that CS can reduce the fire risk of TPU; 2.0‐wt% CS could make the peak value of heat release rate (pHRR) decreased to 457.2 kW/m², reduced by 65.9% compared with TPU. And the peak value of smoke production rate (pSPR) and total smoke release (TSR) of the same sample was decreased by 79.4% and 54.2%, respectively. The TG‐IR and GC‐MS results confirmed that CS could promote TPU decomposition in advance, reacting with the decomposition products of TPU. Therefore, the production of combustible gas was reduced. The GC‐MS results showed that the production of isocyanates and ethers was reduced with the addition of CS. The digital photographs of SEM for the samples after CCT were shown that the char residue layer of the sample containing 2.0‐wt% CS was fibrous in shape. It could be speculated that the thermal decomposition products from TPU could react with CS at low temperature, which reduced the production of flammable gases. So CS had a good prospect in reducing the fire hazard for TPU.     

Preparation of a novel phosphorus‐containing organosilicon and its effect on the flame retardant and smoke suppression of polyethylene terephthalate

A novel phosphorus‐containing silicone flame retardant (PDPSI) was prepared by Mannish reaction, and a series of PDPSI/PET composites were prepared by melt blending method. The nuclear magnetic resonance (¹H NMR), Fourier transformation infrared (FTIR), and the thermogravimetric analyzer (TGA) results indicated that PDPSI showed network structure and owned good thermal stability, with the char residue of 62.2% at 800°C. The flame retardancy of PDPSI/PET composites was characterized by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter (CCT). The results revealed that the addition amount of PDPSI was 5%, the LOI value of PDPSI/PET composites increased to 27.3%, and UL‐94 test passed V‐0 rating. When the PDPSI loading was 3%, PET composites showed excellent flame retardancy and smoke suppression, with a decrease in the peak heat release rate (PHRR) by 71.19% and the total smoke release (TSP) reduced from 14.4 to 11.1m². The scanning electron microscopy (SEM) and FTIR results of char residue demonstrated that the flame‐retardant mechanism of PDPSI was solid phase flame retardant. PDPSI catalyzed the aromatization reaction of PET to promote the formation of a dense and continuous carbon layer, finally improving the flame retardancy and smoke suppression properties of PET.     

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.     

Synthesis of a novel ionic liquid containing phosphorus and its application in intumescent flame retardant polypropylene system

A novel ionic liquid containing phosphorus ([PCMIM]Cl) was synthesized and characterized by FTIR, ¹H NMR, ¹³C NMR and ³¹P NMR. Moreover, a new intumescent flame retardant (IFR) system, which was composed of [PCMIM]Cl and ammonium polyphosphate (APP), was used to impart flame retardancy and dripping resistance to polypropylene (PP). The flammability and thermal behaviors of intumescent flame‐retarded PP (PP/IFR) composites were evaluated by limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA) and cone calorimeter test. It was found that there was an obvious synergistic effect between [PCMIM]Cl and APP. When the weight ratio of [PCMIM]Cl and APP was 1:5 and the total amount of IFR was kept at 30 wt%, LOI value of PP/IFR composite reached 31.8, and V‐0 rating was obtained. Moreover, both the peak heat release rate and the peak mass loss rate of PP/IFR composites decreased significantly relative to PP and PP/APP composite from cone calorimeter analysis. The TGA curves suggested that [PCMIM]Cl had good ability of char formation, and when combined with APP, it could greatly promote the char formation of PP/IFR composites, hence improved the flame retardancy. Additionally, the rheological behaviors and mechanical properties of PP/IFR composites were also investigated, and it was found that [PCMIM]Cl could also serve as an efficient lubricant and compatibilizer between APP and PP, endowing the materials with satisfying processability and mechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.     

Properties of fire agent integrated with molecular sieve and tetrafluoroborate ionic liquid in thermoplastic polyurethane elastomer

Thermoplastic polyurethane (TPU) elastomer has a widely application because of its perfect physical and chemical properties. However, it was limited by its low reliability in fire safety. In this paper, a new fire agent integrated with molecular sieve and tetrafluoroborate ionic liquid ([EOOEMIm][BF₄]) was used to improve fire safety of TPU. The fire safety of TPU composites was investigated by cone calorimeter test, smoke density test, and thermogravimetric/infrared spectroscopy, respectively. The results showed that modified molecular sieve (MMS) can improve fire safety of TPU effectively. The luminous flux increased to 10.10%, total smoke release decreased by 58%, and heat release rate declined of 65% than pure TPU when the addition of MMS was 0.5 wt%. In addition, MMS can improve thermal stability of TPU even in nitrogen according to thermogravimetric/infrared spectroscopy test. These proved that MMS has a satisfactory application prospect in fire safe polymer materials.     

Influence of isopropyl tris(dioctylphosphoryloxy) titanate for flame-retardant TPU based on oyster shell powder

The flammability and droplet properties of thermoplastic polyurethane (TPU) have limited its wide application in many fields. In this article, isopropyl tris(dioctylphosphoryloxy) titanate was selected as synergism and compatilizer with oyster shell powder as flame retardant in TPU composites. And the influence of isopropyl tris(dioctylphosphoryloxy) titanate for flame-retardant TPU composites has been intensively investigated using the smoke density test, the cone calorimeter test, and the thermogravimetric analysis/infrared spectrometry, respectively. The test results show that isopropyl tris(dioctylphosphoryloxy) titanate can reduce the smoke production and heat release. And the total smoke production was reduced by 32% when the mass fraction of isopropyl tris(dioctylphosphoryloxy) titanate was 0.1%. The above results indicate that isopropyl tris(dioctylphosphoryloxy) titanate has a good application prospect in reducing the risk of TPU combustion.

     

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.     

“One‐pot” synthesis of crosslinked silicone‐containing macromolecular charring agent and its synergistic flame retardant poly(l‐lactic acid) with ammonium polyphosphate

A crosslinked silicone‐containing macromolecular charring agent (CSi‐MCA) was synthesized via “one‐pot” process, and it was combined with ammonium polyphosphate (APP) to synergistically improve the flame retardancy of poly(l ‐lactic acid) (PLA). The chemical structure of synthesized CSi‐MCA was characterized by Fourier transform infrared spectroscopy and solid‐state ¹³C nuclear magnetic resonance. The thermal gravimetric analyzer indicated that the CSi‐MCA displayed good thermal stability and high residue via the catalytic crosslinking. Furthermore, the flame retardant effect of CSi‐MCA and APP as intumescent flame retardants in PLA system was investigated by limited oxygen index, UL94, and cone calorimeter test. When the content of CSi‐MCA was 5 wt% and APP was 10 wt% (CSi‐MCA/APP = 1/2), the limited oxygen index value of composites was 33.6 and UL94 classed a V‐0 rating. The peak heat release rate and total heat release of PLA composites containing both APP and CSi‐MCA decreased significantly in comparison with those with APP or CSi‐MCA alone. The flame retardancy mechanism was investigated via analyzing residual chars by scanning electron microscopy and X‐ray photoelectron spectroscopy as well as the possible chemical reaction between APP and CSi‐MCA by thermal gravimetric analyzer and Fourier transform infrared spectroscopy. The results showed that the enhanced flame retardancy was attributed mainly to synergistic effect of CSi‐MCA and APP, which could form a compact, continuous, and protective layer during combustion. Copyright © 2017 John Wiley & Sons, Ltd.     

Synergistic effects of ammonium polyphosphate and red phosphorus with expandable graphite on flammability and thermal properties of HDPE/EVA blends

In this work, the flame‐retardant high‐density polyethylene/ethylene vinyl‐acetate copolymer (HDPE/EVA) composites have been prepared by using expandable graphite (EG) as a flame retardant combined with ammonium polyphosphate (APP) and red phosphorus masterbatch (RPM) as synergists. The synergistic effects of these additives on the flammability behaviors of the filled composites have been investigated by limiting oxygen index, UL‐94 test, cone calorimeter test, thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR), and scanning electron microscopy. The results show that APP and RPM are good synergists for improving the flame retardancy of EG‐filled HDPE/EVA composites. The data from TGA and FTIR spectra also indicate the synergistic effects of APP and RPM with EG considerably enhance the thermal degradation temperatures but decrease the charred residues of the HDPE/EVA/EG composites because the flame‐retardant mechanism has changed. The morphological observations present positive evidences that the synergistic effects take place in APP and RPM with EG in flame‐retardant EG‐filled HDPE/EVA/EG composites. The formation of stable and compact charred residues promoted by APP and RPM with EG acts as effective heat barriers and thermal insulations, which improves the flame‐retardant performances and prevents the underlying polymer materials from burning. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermal stability and fire reaction of poly(butylene succinate) nanocomposites using natural clays and FR additives

Thermal stability and fire retardancy of poly(1,4‐butanediol succinate) (PBS) nanocomposites with sepiolite and 2 halloysites was investigated using thermogravimetric analysis. Despite detrimental influence on thermal stability, confirmed by the use of isoconversional methods, nanoclays improve PBS fire behavior, studied using pyrolysis combustion flow calorimetry and cone calorimeter. Combinations of nanoclays with ammonium polyphosphate (APP) and aluminum diethyl phosphinate at 20 wt% global loading were tested using cone calorimeter at 50 kW/m². It was noticed that the formation of protective structures of metallic phosphates with APP improves fire performance. The influence of ternary compositions combining sepiolite, APP, and lignin on fire performance was investigated. The composition having equimassic loading of each component leads to strong reductions in peak of heat release rate and Maximum of Average Heat Release Evolved (MAHRE) through the formation of a cohesive protective residue, containing new types of metallic phosphates and reinforced by sepiolite particles. This composition also allows smoke release rate to be minimized.     

Influences of coupling agent on thermal properties, flammability and mechanical properties of polypropylene/thermoplastic polyurethanes composites filled with expanded graphite

In this study, polypropylene (PP)/thermoplastic polyurethanes (TPU) filled with inorganic intumescent flame retardant expanded graphite (EG) was prepared by melt blending in a twin-screw extruder. The thermal stability, fire retardancy, mechanical properties, and fracture morphology of PP/TPU composites with treated and untreated EG were investigated by thermogravimetric analysis, cone calorimeter, and scanning electron microscope. The results showed that both untreated and treated EG can greatly enhance the thermal stability and fire resistance of polymer matrix materials. Compared with untreated EG, treated EG can further improve the flame retardancy of the composites. For example, treated EG can further reduce the heat release rate, total heat release, and CO emissions of the composites in the combustion. Surface treatment of EG could significantly improve elongation at break and impact strength of PP/TPU/EG composites due to its enhanced interfacial adhesion and the good dispersion of EG particles in the polymer matrix.     

Thermal and flame retardant properties of novel intumescent flame retardant polypropylene composites

Novel intumescent flame retardant polypropylene (PP) composites were prepared based on a char forming agent (CFA) and silica-gel microencapsulated ammonium polyphosphate (Si-MCAPP). The thermal and flame retardancy of flame retardant PP composites were investigated by limiting oxygen index, UL-94 test, cone calorimetry, thermogravimetric analysis, scanning electron micrograph, and water resistance test. The results of cone calorimetry show that the flame retardant properties of PP with 30 wt% novel intumescent flame retardants (CFA/Si-MCAPP = 1:3) improve greatly. The peak heat release rate and total heat release decrease, respectively, from 1,140.0 to 156.8 kW m^?2 and from 96.0 to 29.5 MJ m^?2. The PP composite with CFA/Si-MCAPP = 1:3 has the excellent water resistance, and it can still obtain a UL-94 V-0 rating after 168 h soaking in water.     

Flame retardant mechanism of an efficient flame-retardant polymeric synergist with ammonium polyphosphate for polypropylene

An efficient flame retardant polymeric synergist poly[N⁴-bis(ethylenediamino)-phenyl phosphonic-N², N⁶-bis(ethylenediamino)-1,3,5-triazine-N-phenyl phosphonate] (PTPA) was designed and synthesized from cyanuric chloride, ethylenediamine and phenylphosphonic dichloride. It was characterized by Fourier Transform Infrared (FTIR), ¹H NMR and ³¹P NMR, Elemental Analysis (EA) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Combined with ammonium polyphosphate (APP), a new intumescent flame retardant (IFR) was obtained. The flammability behaviors of polypropylene (PP)/IFR system were investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimetry. With 25 wt% of IFR (APP:PTPA = 2:1), the PP/IFR system could achieve a LOI value of 34.0% and UL-94 V-0 rating, and the heat release rate (HRR), peak heat release rate (PHRR), total heat release (THR) and smoke production rate (SPR) were considerably reduced, especially HRR and SPR were decreased by 85% and 79%, respectively. The results indicate that there is an excellent synergism between APP and PTPA, which endows PP with both good flame retardancy and good smoke suppression. Furthermore, the thermal degradation mechanism of IFR and the flame-retardant mechanism of PP/IFR system were investigated by thermogravimetric analysis (TGA), FT-IR, TG-FTIR and scanning electron microscope (SEM). The study on the flame-retardant mechanism of IFR indicated that a structure containing –CN was formed due to the reaction between APP and PTPA.