Improved Flame Retardant Properties Research Articles

Low-flammability carbon fiber reinforced composites based on low-viscosity phosphorus-containing epoxy binders for transfer molding methods

This study is the first investigation into the possibility of low viscosity phosphorus-containing epoxy binders using triglycidyl phosphate for carbon fiber-reinforced polymers (CFRPs) production by resin transfer molding (RTM). Rheological studies and flammability evaluations were carried out to determine the optimum concentrations of triglycidyl phosphate in the epoxy binder. The introduction of triglycidyl phosphate into the epoxy composition was shown to produce self-extinguishing epoxy polymers. In addition, the curing kinetics of the phosphorus-containing epoxy binder was evaluated using differential scanning calorimetry (DSC) to optimize the curing process. The impregnation process of the product in the PAM-RTM software package was modeled to evaluate the possibility of obtaining large-size CFRP parts based on the developed binder by transfer molding methods. The physical-mechanical and fire-resistant tests of CFRPs showed significant improvement in flame-retardant properties in the modified samples, while maintaining high values of strength and elastic modulus. The study concluded that the introduced triglycidyl phosphate significantly affects the binder properties by reducing the viscosity, and increasing the flame retardancy, thus opening a promising direction for developing advanced composite materials.

Effect of aluminum diisobutyl hypophosphate in polyethylene terephthalate and its flame retardant mechanism

AbstractAlkyl hypophosphate flame retardants have aroused intense research interests in flame retardancy of polymers owing to the combined effect of gas phase and condensed phase. In this work, aluminum diisobutyl hypophosphate (APBA) was incorporated into polyethylene glycol terephthalate (PET) to investigate its flame retardant effect and mechanism. PET achieved a V‐2 level in UL‐94, with a low LOI of 21.2%. In contrast, PET/APBA‐15% composites showed a 51% increase of LOI value and a V‐0 level, accompanied with the significant reduction of melt droplets. Gas phase analysis by Py‐GC/MS and TG‐FTIR indicated that the phosphorous free radicals and nonflammable gases were generated during the cracking of APBA, resulting in the radical quenching and dilution of combustible gas. Condensed phase analysis by SEM, Raman, and XPS results revealed that APBA could effectively facilitate the formation of dense char layers consisting of aluminophosphate and graphitic structures due to the interaction with PET matrix. The compact barrier layer could insulate heat and inhibit the volatilization of combustible materials, leading to improved flame retardant properties. Furthermore, the introduction of APBA increased the melt viscosity of PET/APBA composites according to rheological analysis, which further promoted the formation of a char barrier layer to further enhance the flame retardant properties.Highlights Aluminum diisobutyl hypophosphate is used as an efficient flame retardant for PET. The flame retardant can degrade to release the phosphorous free radicals. The flame retardant can interact with the PET matrix and promote the charring.

Intelligent bamboo: A splendid flame retardant, fire warning and photothermal sterilization nanocoating via low-temperature evaporation induced self-assembly

The application of bamboo to assist carbon neutral strategy has attracted worldwide attention due to its naturally carbon-negative property. However, the inherent defects of flammable and mildewed make bamboo encounter a bottleneck in its application. Hence, an intelligent bamboo (IB) with integrated performances of stable connection, high-temperature resistance, reliable fire warning and splendid photothermal sterilization properties was constructed via low-temperature evaporation induced self-assembly strategy. The hydrogen bonding, coordination complexes, van der Waals forces, and electrostatic forces can be formed between Ti3C2Tx (MXene) and pre-treated bamboo substrate (TB). The optimized bamboo-based fire alarm sensor (AM@TB) exhibits significant improvement in flame retardant properties, e.g., the limiting oxygen index (LOI) value of AM@TB8-2 was 61.4%, surpassing TB by an impressive margin of 65.8% and the vertical burning test reach the UL94 V-0 rating. Besides the PHRR (heat release rate) of AM@TB8-2 was decreased 80.3% compared to TB. The residual mass of AM@TB8-2 is 34.5%, which is 1.6 times higher than TB. Additionally, the AM@TB8-2 presents a sensitive fire warning response (∼2 s) and reliable repeatability. Furthermore, based on the outstanding photothermal conversion performance of MXene, AM@TB8-2 demonstrates predominant sterilization efficacy after a near-infrared laser (NIRL) illumination. Therefore, this work provides inspiration for the design and fabrication of high-performance IB that combine fire safety and antimicrobial properties.

Fully bio-based and intrinsically flame retardant unsaturated polyester cross-linked with isosorbide-based diluents

Unsaturated polyester resins (UPR) are composed of prepolymers and styrene diluents, while the former are produced by co-polycondensation between diol, unsaturated diacid and saturated diacid. In this work, bio-based UPR prepolymers were synthesized from bio-based oxalic acid, itaconic acid, and ethylene glycol, which were then diluted with bio-based isosorbide methacrylate (MI). Meanwhile, the phenylphosphonate were introduced into the molecular chains of prepolymers to achieve intrinsic flame retardancy of bio-based UPR. The potential of the reactive MI diluents as substitutes of volatile styrene, was also assessed through the volatility test, curing kinetics and gel contents analysis. For UPR materials with styrene diluents, the UPR materials can achieve UL-94 V0 level and the 28% of limiting oxygen index (LOI) with 2.63 wt% of phosphorus contents. By contrast, the UPR materials with MI diluents can reach UL-94 V0 level with only 2.14 wt% of phosphorus contents. As the phosphorus contents were further increased to 2.63 wt%, UPR materials can achieve highest 29%, while the peak of heat release rate (PHRR) and total heat release (THR) were decreased by 68.01% and 48.62%, respectively. The Flame Retardancy Index (FRI) was also used to comprehensively evaluate the flame retardant performance of UPR composites. Compared with neat UPR, the composites with MI diluents and phosphorus containing structures increased from 1.00 to 6.46. The mechanism for improved flame retardancy was analyzed from gaseous and condensed phase. Additionally, the tensile strengths of bio-based UPR materials with styrene and MI diluents were studied. This work provides an effective method to prepared high-performance and fully bio-based UPR materials with improved flame retardant properties and safety application of reactive diluents.

Effect of magnesium hydroxide and graphene nanoplatelets on the properties of peroxide cross‐linked linear low‐density polyethylene nanocomposite

AbstractLinear low‐density polyethylene (LLDPE) and different concentrations (5‐20 wt%) of magnesium hydroxide (MAH) as a filler either with or without the addition of graphene nanoplatelets (GNPs) were peroxide cross‐linked using dicumyl peroxide as a cross‐linking agent in a twin‐screw extruder. The mechanical, thermal stability, flame retardancy, morphological, and rheological properties of the prepared samples were investigated. The mechanical properties of the peroxide cross‐linked LLDPE samples with higher MAH and GNP in the matrix were significantly improvement compared to neat LLDPE. This indicates that the addition of MAH and GNP to the peroxide cross‐linked LLDPE matrix could be suitable reinforcing fillers to achieve better and enhanced mechanical properties, particularly tensile strength. Conversely, a significant decrease in the elongation at break values was found for peroxide cross‐linked LLDPE samples compared to neat LLDPE. Similarly, results of thermogravimetric analysis revealed remarkable thermal stability enhancement in the peroxide cross‐linked LLDPE samples with higher MAH and GNP compared to neat LLDPE. The results from UL94 test demonstrated that the peroxide cross‐linked LLDPE samples comprising higher MAH with GNP exhibited improved V = 0 rating compared to poor no rating (NR) for neat LLDPE. Furthermore, the scanning electron microscope and digital images shown improved flame retardancy properties for these samples because of the formation of protective char layer on the sample surface. The complex viscosity for the peroxide cross‐linked LLDPE samples, at lower frequency, increased with increasing MAH loading and further addition of GNP compared to neat LLDPE.Highlights Cross‐linked polyethylene with flame retardant (FR) and nanofiller were prepared. Effects of cross‐linking and FR on the final properties of the polymer were studied. 20wt% FR with 3 phr nanofiller promoted the final properties of the polymer. Higher filler loading in the polymer improved flame retardancy and thermal stability. Combined effect of cross‐linking and FR has shown major improvement.

Processing of natural lignocellulosic coir fibres for enhanced flame retardancy using aluminium trihydrate

The high lignin cellulose ratio in coir fibres makes it more susceptible to fire, whereby coir and its allied products are pushed back away from fire retardant applications. These fibres are subjected to treatments by soaking in hot dilute solution of aluminium trihydrate for enhanced fire retardancy. The treated fibres exhibited improved flame retardant properties with reduced water absorption and showed no remarkable change on the physical and mechanical characteristics. The time of burning was significantly reduced from 182 to 65 seconds and the treated fibres did not produce smoke when burnt. The flame propagation rate was reduced by 2.5 times and limiting oxygen index elevated by 1.2 times compared to the raw fibre. As a low toxic, sparingly soluble substance, aluminium trihydrate is a better halogen-free fire retardant addition for coir fibres in product manufacturing in the coir sector.

Fabrication and post‐processing of PI/PVDF‐HFP/PI electrospun sandwich separators for lithium‐ion batteries

AbstractPI/PVDF‐HFP/PI sandwich separators were prepared by electrospinning, and subsequent pressing and heat treatment were used to improve their properties. Morphology, porosity, air permeability, contact angle, and other specifications of the separators were evaluated. The results showed that heat treatment changed separator porosity and permeability. The pressed and heat‐treated PI/PVDF‐HFP/PI separators showed suitable air permeability (313.49 s) and higher porosity (71.57%) compared to commercial PP separators. Subsequent heat treatment improved tensile strength from 3.48 to 19.09 MPa. The use of polyimide as the sandwich in PI/PVDF‐HFP/PI sandwich separator causes improved flame retardant properties and minimizes thermal shrinkage (2%). On the other hand, the use of PVDF‐HFP as an intermediate layer with a melting temperature of 148–155°C makes for a safe condition to shut down ta lithium‐ion battery and prevents an explosion. Finally, a coin cell assembled with a pressed and heat‐treated PI/PVDF‐HFP/PI separator showed a discharge capacity of 176 mAh/g at the rate of 0.1C and had higher capacity at the rates above 2C in comparison to the commercial separator (PP).

Synthesis of ZnFe2O4@Mg‐Al‐SDBS LDH composites for regulating heat and fire safety properties of polyurea

AbstractThe flame retardant zinc ferrite@Mg‐Al‐sodium dodecyl benzene sulfonate layered double hydroxide (ZnFe2O4@Mg‐Al‐SDBS LDH) was prepared successfully by simple hydrothermal method and co‐precipitation method. ZnFe2O4 nanoparticle was used as the core on which Mg‐Al LDH was encapsulated to form a spherical structure with a lamellar intercalation layer. The microstructure, the phase structure, and the thermal properties of flame retardant were characterized in detail. Compared with pure polyurea (PUA), the total heat release (THR), peak heat release rate (PHRR) and smoke factor (SF) of PUA/ZnFe2O4@Mg‐Al‐SDBS LDH 3.0 wt% decreased by 17.64%, 20.13%, and 28.42%, respectively. In the combustion process, Mg‐Al LDH could generate porous metal oxides (Al2O3 and MgO), and ZnFe2O4 could also be decomposed into ZnO and Fe2O3. These oxides catalyzed cross‐linking of polymer molecules, to promote the formation of a dense char layer, and isolated heat and combustible gases from the underlying material. The improved flame retardant properties of the modified intercalated microspheres could be attributed to catalytic carbonization and physical barrier. Moreover, the mechanical properties of PUA composites were tested by universal tensile testing machine. The results showed that the addition of ZF@MASL flame retardant had little influence on the mechanical properties of PUA composites.

Preparation of dyeing, flame retardant and anti-dripping polyethylene terephthalate fibers based on natural sodium copper chlorophyll dyeing and intercalation of phosphorylated sucrose fatty acid ester

As the largest synthetic fibers in the world, polyethylene terephthalate (PET) fibers have a wide range of applications. However, PET fibers are flammable fibers with serious droplet phenomenon during combustion, which has great potential safety hazards. To solve the issue, multifunctional PET fibers with dyeing, flame retardant and anti-dripping were developed in this work. First, dyed PET fibers (DY-PET) were prepared by directly dyeing of PET fibers with sodium copper chlorophyllin (SCC). Then, DY-PET was intercalated with ammonium phosphate of sucrose fatty acid ester (APSFA) to obtain the flame retardant PET fibers (FR-PET). Compared with the original samples, the peak heat release rate (PHRR) and total heat release rate (THR) of DY-PET and FR-PET were significantly reduced. Meanwhile, the limiting oxygen index (LOI) of DY-PET and FR-PET was also improved, indicating the improved flame retardant properties of DY-PET and FR-PET. In addition, the anti-dripping performance was excellent, which was mainly due to the high temperature self-crosslinking, high temperature ionic aggregation and hydrogen bond & π-π stacking effect. The improved flame retardant performance of FR-PET was attributed to the blocking effect of the generated char layer catalyzed by APSFA under high temperature and the dilution effect of incombustible gas resulting from the thermal decomposition of APSFA. This work provided a scalable strategy for the design of dyeing, flame retardant and anti-dripping PET fibers, and endowed PET with great potential application in the field of functional polymer materials.

Preparation of Magnesium Hydroxide Flame Retardant from Hydromagnesite and Enhance the Flame Retardant Performance of EVA.

In this study, hydromagnesite, a rare natural hydrated alkaline magnesium carbonate, was used to synthesize magnesium hydroxide (MH) as a flame retardant for ethylene-vinyl acetate (EVA) to enhance its fire resistance and smoke suppression. Various concentrations of sodium hydroxide (NaOH) were used to alter the morphology and the flame-retardant efficiency of synthesized MH. EVA/MH composites were prepared through melt blending, and the influence of NaOH on the flame retardancy and mechanical properties was investigated by means of the limiting oxygen index (LOI), cone calorimeter test (CCT) and tensile test. The flame retardancy results demonstrated that composites exhibited remarkably improved flame retardant properties after introducing MH, reflected by an increase in the LOI value from 20% for neat EVA to roughly 38%. Additionally, the peak of heat release rate (pHRR), the total heat release (THR) and the peak of the smoke production rate for EVA3 were decreased by 37.6%, 20.7% and 44.4% compared with neat EVA, respectively. In the meantime, increasing char residues were also observed. The incorporation of different MH concentrations had a limited effect on the mechanical properties of the EVA/MH composites.

Effect of Polyolefin Elastomers’ Characteristics and Natural Magnesium Hydroxide Content on the Properties of Halogen-Free Flame-Retardant Polyolefin Composites

This study examines the preparation of several composites that are based on natural magnesium hydroxide (n-MDH) and various poly(ethylene-co-octene) polyolefin elastomers (POEs). Design of experiment (DoE) principles have been applied in order to optimize the mechanical, rheological, and flame-retardant properties of the final composites. DoE allows one to evaluate the influence of each variable on an experiment’s final properties. By increasing the density and crystallinity of the POE, a higher elastic modulus was obtained, which resulted in greater tensile strength and lower elongation at break. Improved flame retardant properties (as measured by the limiting oxygen index (LOI) and vertical burning tests) were obtained by increasing the amount of filler within the composite up to 65% and using a polymer with high crystallinity. More specifically, the best balance between mechanical, rheological, and flame retardant properties was provided by DoE using 63.75% n-MDH filler. The agreement between the predicted performance and the final properties of the composites has enabled the innovative use of DoE to provide reliable predictions about the final mechanical and flame retardant properties of the compounds that are used for low voltage electrical cable applications.

Effect of Borax and Boric Acid on Thermal and Flammability Properties of Rice Husk Reinforced Recycled HDPE Composite

Studies show Rice Husk (RH) and plastic appear viable in the production of a composite material. Flammability is a crucial parameter that limits multiple applications of such materials. Borax (BX) and Boric Acid (BA) have been used for wood and coating products, continually proving to be decent fire retardant agents in wood and plastic composites. In this study, the aim is to develop, test and investigate the thermal and flammability properties of RH reinforced Recycled High-Density Polyethylene (rHDPE) integrated with Maleic Anhydride Polyethylene (MAPE) as a binding agent, with Borax (BX) and Boric Acid (BA) as a fire retardant agent. RH was impregnated with BX and BA (1:1) solution at 2, 3, and 4% weight concentration and oven-dried after seven days at 105 °C for 24 hours. Only an average of 43 wt% of BX and BA remains after the impregnation process. Flammability test results show that adding RH to the composite enhanced flame retardancy compared to the pure rHDPE while adding MAPE as a binding agent makes the composite more flammable. Composite with BX and BA showed significant improvement in flame retardant properties by reducing the horizontal burning rate by 26% for 3% weight and 46% for 5% weight of MAPE. Thermogravimetric analyses exhibit an increase in the thermal stability by adding RH to reinforce rHDPE than pure rHDPE and further augmented by the integration of BX and BA. Keywords: rice husk, recycled high-density polyethylene, thermal, flammability

Castor-oil based polyurethane/NiCo-OLDH nanocomposites with improved flame retardant properties

Polymer nanocomposites are known for improved thermal properties, mechanical properties, gas permeability and flame retardant properties compare to neat polymer matrix or conventional composites. Polymer matrix nanocomposites are widely used in defense use, equipment, automobiles and aircraft components, housings, packaging, coating applications. The present work aims to prepare polymer matrix nanocomposites to improve the flame retardant properties of a matrix where reinforcement is flame retardant in nature. The castor-oil based polyurethane has been synthesized by reacting castor-oil and isophorone diisocyanate which is flammable. It is very important to mention that inorganic nanofillers i.e. layered double hydroxides have been used as a reinforcement in castor-oil based polyurethane to increase the flame retardant, thermal and mechanical properties of nanocomposites. In this study, nickel–cobalt organomodified layered double hydroxide (NiCo-OLDH) has been prepared by the co-precipitation method. The prepared NiCo-OLDH has been characterized by various techniques. The average particle size of the OLDH nanoparticles is 68 nm as analyzed by particle size analyzer. The morphology of the OLDHs are in fibril form as shown in transition electron microscopy (TEM). The different weight percentages of NiCo-OLDH (1.5–5%) have been incorporated into synthesized castor oil based polyurethane (COBPU) to prepare COBPU/NiCo-OLDH nanocomposites using solvent blending method and characterized by FTIR, XRD, SEM, TGA techniques. FTIR has been used to confirm the functional group and metal oxide present in the nanocomposites. COBPU/NiCo-OLDH nanocomposites have shown a 10 % improvement in thermal stability and an increased in tensile strength of 26% as compared to neat COBPU. Flame retardancy as measured by LOI of the nanocomposites are in the range of 23–28%.

Morphological, Mechanical and Thermal Characterization of Intralayer Hybrid Composites Based on Polylactic Acid (PLA) and Sisal Fiber

ABSTRACT Novel intralayer hybrid composites (IHC) based on a commercial polylactic acid (PLA) matrix reinforced with a hybrid plain-woven fabric, composed of PLA filaments and sisal fibers, were obtained by film stacking followed by compression molding. Two different stacking configurations were explored. In one configuration, weft and warp directions of all fabric layers were equally oriented whereas in the other configuration, weft and warp directions of fabric layers were alternately oriented. The effect of the stacking sequence on the materials morphology and thermal and tensile behavior was investigated. All obtained composites presented higher thermal stability than the matrix due to the presence of the natural fibers and PLA filaments and also, the existence of lignocellulosic compounds in the woven fabric led to a char yield residue, with the expected improvement of flame retardant properties. Although both IHCs exhibited highly anisotropic tensile behavior, the composite having an alternated fabric layers configuration, presented a good balance of stiffness and strength for the two main orthogonal loading directions.

Metal‐organic frameworks derived ZnO@MOF@PZS flame retardant for reducing fire hazards of polyurea nanocomposites

Transition metal as flame retardant has attracted intense interests in recent years. In this work, ZnO@MOF@PZS was prepared via hydrothermal and polycondensation methods. ZnO nanoflowers played the role as a template for growth of MOF@PZS and zinc source for formation of MOF. Subsequently, the obtained ZnO@MOF@PZS was mixed into polyurea (PUA) to investigate its flame retardancy and toxicity suppression properties. The cone calorimeter test (CCT) showed that ZnO@MOF@PZS significantly improved the flame retardancy of PUA composites. The addition of 3 wt% ZnO@MOF@PZS into PUA could result in peak heat release rate (PHRR), total heat release (THR) and total CO production (TCO) of 28.30%, 19.59% and 36.65%, respectively. The result of universal testing machine showed that ZnO@MOF@PZS‐add PUA had better mechanical properties. It is notable that the improved flame retardant properties for PUA composites are mainly attributed to ZnO@MOF@PZS promoting the formation of dense char residue.

Magnetic Field-Induced Orientation of Modified Boron Nitride Nanosheets in Epoxy Resin with Improved Flame and Wear Resistance.

In this work, self-lubricating boron nitride nanosheets (BNNs) were decorated with flame-retardant zinc ferrite (ZnFe2O4), followed by stearic acid modification to obtain magnetic and hydrophobic properties. Under the external magnetic field, the obtained ZnFe2O4-BNNs can be well ordered into one-dimensional orientation in the epoxy resin (EP) matrix-enabling improved flame retardant properties. Compared to a randomly oriented ZnFe2O4-BNN equivalent, the well-orientated ZnFe2O4-BNNs (at 10% mass fraction) reduce the peak heat release rate and CO production by 47 and 51%, respectively. Furthermore, the ZnFe2O4-BNN/EP composite monoliths demonstrate excellent durability, displaying continued superhydrophobicity under Taber abrasion, high external pressure, knife scratch, long-term exposure to acids/bases, and harsh UV irradiation. In addition, the result shows that the well-oriented ZnFe2O4-BNN/EP composite demonstrates better tribological performance and the friction coefficient is reduced by 76.9%.

Combustion forming hollow nanospheres as a ceramic fortress for flame-retardant fiber

Simple, effective and safe flame retardants are required to improve flame retardant properties of polymer fibers. However, traditional additive flame retardants, such as halogen-flame retardants and intumescent flame retardants, are likely to cause phase separation of functional phases due to their poor dispersibility and compatibility, or are difficult to be suitable for the high temperature processing conditions of melt-spun fibers. Here, in an effort to develop a practical flame retardant system in which zinc diphosphinate (DEPZn) and D-glucose (DG) were selectively incorporated into polyethylene terephthalate (PET) fiber was developed. As a result, the dense nano-scale zinc phosphate microspheres were formed on the surface and inside the residual carbon during combustion. Thus, PET fibers were endowed with excellent flame retardancy through a thermal barrier and enhancement of physical strength for the carbon layer. Moreover, a synergistic flame-retardant effect was found between DEPZn and DG. DG reduced the size of the zinc phosphate nanosphere from 200 ​nm to 50 ​nm, making the carbon layer denser and smoother. As a result, the peak heat release of the resultant PET composite fiber decreased to 410 ​kW/m2 compared 1276 ​kW/m2 for neat PET fiber. Moreover, the total smoke release also dropped from 71 ​MJ/kg of neat PET fiber to 64 ​MJ/kg for PET composite fibers. These results provide a promising strategy for the production of industrialized PET flame retardant fibers.

Functionalized CNTs with DOPO and Silicon Containing Agents: Effective Reinforcer for Thermal and Flame Retardant Properties of Polystyrene Nanocomposites.

DOPO and silicon containing agents modified multiwalled carbon nanotubes (MCNTs) were synthesized through sol-gel process and MCNTs are introduced into polystyrene (PS) through in situ polymerization. TEM observations and FTIR results of MCNTs demonstrated that the MCNT nanofillers were coated with the organic/inorganic flame retardant compound. Moreover, the TEM results of the composites indicate that MCNTs dispersed in polystyrene PS matrix uniformly due to the modification. The PS/MCNTs composites showed improved thermal stability as well as flame retardant properties in comparison with PS/CNTs composites, which are due to the good dispersion of MCNT in the PS matrix. MCNTs in the PS matrix can also reduce the peak heat release rate, total heat release and improve the smoke suppression performance. The improved flame retardant properties are attributed to the char reinforcing effect of CNTs, which can provide enough time for MCNTs and organic/inorganic compound to trap the degradation of polymer chains and catalyze the formation of char. The char layers can not only serve as an efficient insulating barrier to reduce the exposure of PS matrix to heat source but also retard the releasing of combustible gas.

Preparation and characterization of PET/SEBS incorporated with organomontmorillonite

This study is focused on the characterization of polyethylene terephthalate (PET)/Styrene-Ethylene-Butylene-Styrene (SEBS)/Organomontmorillonite (OMMT) blends. SEBS-g-MA is used as compatibilizer and SEBS is the impact modifier at 30 %wt. The compounds were blended by twin-screw extruder and molded for test specimen by injection molding. The effect of OMMT types (Cloisite15A and Cloisite30B) and contents (1 and 3 %w/w) on properties of PET blends with SEBS and SEBS-g-MA were investigated. The PET composites incorporated with Cloisite15A had higher impact strength and %elongation at break whereas lower tensile strength than the one with Cloisite30B. Comparing with PET/SEBS/SEBS-g-MA blends, adding OMMT into PET/SEBS/SEBS-g-MA would increase thermal property. However, it had no significant changes with higher OMMT. %Crystallinity of PET would be increased with OMMT contents. PET/SEBS/SEBS-g-MA had lower %LOI but higher burning rate compared with PET. However, the addition of OMMT could improve flame retardant properties of PET blends. Addition of Cloisite15A and Cloisite30B into PET/SEBS/SEBS-g-MA increased %LOI. From UL 94 tests, polymer composites could be classified in HB class. The burning rate of polymer composites was decreased with increasing OMMT due to decomposition of OMMT act as a barrier to inhibit combustion.

Development of Novel Polyamide 11 Multifilaments and Fabric Structures Based on Industrial Lignin and Zinc Phosphinate as Flame Retardants.

Biobased lignin represents one of the possible materials for next-generation flame retardant additives due to its sustainability, environmental benefits and comparable efficiency to other flame retardant (FR) additives. In this context, this study presents the development of FR polyamide 11 (PA11) multifilament yarns and fabric structures containing different industrial lignins (i.e., lignosulfonate lignin (LL), and Kraft lignin (KL)) and zinc phosphinate (ZnP). The combination of ZnP and lignin (KL or LL) at different weight ratios were used to prepare flame retarded PA11 blends by melt mixing using a twin-screw extruder. These blends were transformed into continuous multifilament yarns by the melt-spinning process even at a high concentration of additives as 20 wt%. The mechanical test results showed that the combination of KL and ZnP achieved higher strength and filaments showed regularity in structure as compared to the LL and ZnP filaments. Thermogravimetric (TG) analysis showed the incorporation of lignin induces the initial decomposition (T5%) at a lower temperature; at the same time, maximum decomposition (Tmax) shifts to a higher temperature region and a higher amount of char residue is reported at the end of the test. Further, the TGA-FTIR study revealed that the ternary blends (i.e., the combination of LL or KL, ZnP, and PA11) released mainly the phosphinate compound, hydrocarbon species, and a small amount of phosphinic acid during the initial decomposition stage (T5%), while hydrocarbons, carbonyls, and phenolic compounds along with CO2 are released during main decomposition stage (Tmax). The analysis of decomposition products suggests the stronger bonds formation in the condensed phase and the obtainment of a stable char layer. Cone calorimetry exploited to study the fire behavior on sheet samples (polymer bulk) showed an improvement in flame retardant properties with increasing lignin content in blends and most enhanced results were found when 10 wt% of LL and ZnP were combined such as a reduction in heat release rate (HRR) up to 64% and total heat release (THR) up to 22%. Besides, tests carried out on knitted fabric structure showed less influence on HRR and THR but the noticeable effect on postponing the time to ignition (TTI) and reduction in the maximum average rate of heat emission (MARHE) value during combustion.