key: cord-0951078-ynr336rf
authors: Wang, Xingguo; Wang, Wenjia; Wang, Shuheng; Yang, Yufan; Li, Hongfei; Sun, Jun; Gu, Xiaoyu; Zhang, Sheng
title: Self-intumescent polyelectrolyte for flame retardant poly (lactic acid) nonwovens
date: 2020-10-02
journal: J Clean Prod
DOI: 10.1016/j.jclepro.2020.124497
sha: 6da87ba5d9469c4a19503ea267dc54c9687d910c
doc_id: 951078
cord_uid: ynr336rf

The demand for eco-friendly poly (lactic acid) (PLA) nonwovens grows at a high rate in the past several decades, however, only a little attention has been received for flame retardant PLA nonwoven fabrics. In this work, a novel halogen-free self-intumescent polyelectrolyte tris (hydroxymethyl)-aminomethane polyphosphate (APTris) was synthesized by reacting ammonium polyphosphate with tris (hydroxymethyl) aminomethane, and was then used to improve the fire resistance of PLA nonwovens via a dip-nip process. The flammability characterization indicated the limiting oxygen index value was increased to 30.0% from 18.3%, and the damaged area in the vertical burning test was reduced by about 87.0% by the presence of APTris. The cone calorimeter test results revealed that the peak heat release rate and total heat release of the treated sample were decreased by 41.0% and 28.2% respectively compared with that of the control PLA nonwoven sample. The char residue was increased to 12.3 from 1.7 wt. % at 800 °C. It is suggested that the dense char barrier formed at the presence of APTris prevents heat, smoke, and gas transfer, and hence enhance thermal dilatability and flame retardancy of PLA nonwovens. This simple sustainable halogen-free treatment has great potential to produce cleaner commercialized flame-retardant PLA nonwovens.

With the depletion of fossil resources and deterioration of the environment, bio-based and biodegradable materials have been drawn more and more attention.

Poly (lactic acid) (PLA), which is derived from renewable resources (e.g., rice, corn, wheat, etc.), can be biodegradable to generate H 2 O and CO 2 (Iwata, 2015; Murariu and Dubois, 2016) , and has become one of the most widely used biodegradable materials. Compared with petroleum-based polymers, the production of PLA requires 25-55% less energy and consumes carbon dioxide, which doesn't cause environmental damage and pollution (Farah et al., 2016) . PLA fabrics are also considered as an ideal J o u r n a l P r e -p r o o f candidate to substitute petroleum-based chemical fabrics. PLA nonwovens grow at a high rate in the several decades (Wang et al., 2007) , and it is widely applied in the textile industry, such as upholstery backings, needle punched carpets, agricultural textiles, furniture fabrics, linings, and geotextile products (Cheng et al., 2016a) .

Unfortunately, PLA nonwovens are unsuitable in many commercial cases for its intrinsic flammability (Parma et al., 2014) . PLA is flammable with a very low limited oxygen index (LOI) of 18~19%, and the key challenge for flame retardant PLA is the severe molten dripping. Although intensive efforts have been made on the flame-retardant PLA thermoplastics, the research on flame-retardant PLA nonwovens are rarely reported so far. Therefore, it is necessary to develop high value-added biodegradable flame-retardant PLA nonwovens in the textile industry (Cheng et al., 2019; Shahid ul et al., 2013) .

The halogen-containing flame retardants were widely applied in the textiles industry (Kemmlein et al., 2009; Qi et al., 2014) , however, these halogenated compounds usually exist the harm of bioaccumulation in the environment and generate toxic gases during combustion to cause serious environmental pollution and health problems (Liu et al., 2020) . Therefore, halogen flame retardants are restricted more and more in many countries (Veen and Boer, 2012) . It has been demonstrated that P/N containing flame retardants are efficient additives to reduce the fire hazard of PLA thermoplastics (Bourbigot and Fontaine, 2010; Wang, X. et al., 2019) , and are more environmentally friendly than halogen-containing flame retardants. The introduction of phytic acid (PA) into PLA nonwovens by a pad-dry-cure process (Cheng et al., 2016b) increased the LOI value of PLA/45%PA sample by 37.3% in comparison with that of the control PLA nonwoven sample, but hardly reduced the damaged length in the vertical burning test. Other research reported (Cheng et al., 2016a ) that cyclic phosphonate ester improved the flame retardancy of PLA nonwovens by gas-phase mechanism, and the LOI value was increased by 33.1%, but the performance of microscale combustion and vertical burning test was not satisfactory. A mixture of phosphonate esters was used to enhance the fire performance of PLA nonwovens (Avinc et al., 2012) , after complex drying and curing J o u r n a l P r e -p r o o f procedure, the treated fabrics could pass the criteria of NFPA 701 after washing. The sheath/core configuration bicomponent PLA containing intumescent flame retardants were prepared by melt spinning to fabricate PLA nonwovens by thermal bonding (Maqsood and Seide, 2019) . The obtained PLA/APP5/PES10/KL3 nonwovens showed a 46.0% reduction in pHRR and a 34.5% increase in residual mass compared pure PLA nonwovens, the LOI value of that increased to 30.4% from 19.3%. However, the preparation process which involves high temperature spinning and bonding, is complex and toilsome. In summary, the effective and feasible way for flame-retardant PLA nonwovens is still under seeking.

Polyelectrolytes are long chain compounds with ionizable groups in their repetitive molecular units, which have been widely used as porous materials on environmental remediation, tissue engineering, and catalyst (Zhang et al., 2018) .

Polyelectrolytes are prepared by ionic reaction in aqueous solution, which is convenient, efficient, and eco-friendly (Christophe et al., 2004) . In recent years, polyelectrolytes have attracted extensive attention in the flame-retardant application.

Some bio-based materials including phytic acid, chitosan, casein, and polyethyleneimine have been frequently selected to match each other as anionic or cationic (Holder et al., 2017) . For examples, the chitosan/phytic acid (Zhang et al., 2014) was used to improve the flame retardancy of vinyl acetate copolymer (EVA), and showed excellent intumescent effect to promote the EVA composite to form a compact char layer. Polyethyleneimine and oxidized sodium alginate were alternately coated on polyester-cotton blend fabrics by the layer-by-layer assembly (Pan et al., 2018 ), which enabled the fabrics self-extinguish after being ignited. Guanidine sulfamate (GSM) was added in intumescent polyelectrolyte to improve the flame retardancy of polyester fabrics by the LBL technique (Jordanov et al., 2019) . In our previous work, phytic acid, casein, and ammonium polyphosphate were combined to form core-shell bio-polyelectrolyte PC@APP, and the presence of only 5% PC@APP significantly decreased the peak heat release rate of PLA composites (Jin et al., 2019) .

Overall, polyelectrolytes have been used to enhance the fire resistance of PLA plastic, so it is possible to improve the flame retardancy of PLA nonwoven fabrics by J o u r n a l P r e -p r o o f polyelectrolyte coating.

In this work, a novel polyelectrolyte of tris(hydroxymethyl) aminomethane polyphosphate (APTris) was designed and prepared based on the acid-base equilibrium theory. A high phosphorus-containing ammonium polyphosphate (APP) was chosen as anionic, and a polyhydroxy compound tris (hydroxymethyl)-aminomethane was selected as a guest compound with opposite charge. APTris coating was then introduced onto the surface of PLA nonwovens by a convenient pressure leaching and heat cure process. The combustion behavior and thermal stability of treated PLA nonwovens were comprehensively evaluated, and the mechanism of APTris in improving the flame-retardancy of the fabrics was discussed.

The strategy of coating single self-instrument polyelectrolyte provides an efficient, low cost way to enhance the fire safety of PLA nonwovens. The synthesis of water soluble APTris doesn't involve any toxic solvents, and involved raw materials are readily available at reasonable prices, and the dip-nip technology for flame retardant finishing of PLA nonwovens is efficient, low cost, and suitable for commercialization.

To the best of our knowledge, the application of polyelectrolytes to endow flame retardancy of PLA nonwovens has not been reported so far, this work should be one of the few to focus on the flame retardancy of bio-based PLA nonwovens.

Hydrosoluble ammonium polyphosphate (APP, 10<n<20) was obtained from Shandong Shi An Chemical Industry Co. LTD. Tris (hydroxymethyl)-aminomethane (Tris) was purchased from Beijing Aoboxing Biotech Co., Ltd., Hexadecyl trimethyl ammonium bromide (CTAB) was received from Tianjin Jinke Fine Chemical

Research Institute. PLA nonwovens were purchased from Chengdu Julong Non-woven Co., LTD. with an average filament diameter of 16.5 μm and a surface weight of 100 g/m 2 . The preparation process of APTris was illustrated in Scheme 1(a). After dissolving 20 g APP in a 500 mL beaker with 300 mL DI water, 20 g Tris was added into the solution. The mixed solution was vigorously magnetic stirred at 70 o C, during which NH 3 was continuously released. The reaction was stopped when the pH value reached 7. The solvent was removed by using a rotary evaporator, and the obtained white sticky precipitate was washed with ethanol. Finally, the white viscous product was further dried under vacuum at 80 o C until constant weight. The yield of target product was around 87 wt%.

The treatment process of PLA nonwovens was described in Scheme 1(b).

Specifically, PLA nonwovens were pretreated with C 19 H 42 BrN to improve its hydrophilia and then was impregnated in APTris solution with a concentration of 150 g/L. The pretreated nonwovens were pressured through a two-roll laboratory padder (HB-BL, Huibao Dyeing and Finishing Machinery Factory). Different pressure between the two-rolls was used to obtain samples with different weigh gains, which was listed in Table 1 . Finally, the impregnated nonwovens were dried at 80 o C for 2 h.

PLA nonwovens impregnated with 150 g/L APP solution was selected as a control sample.

J o u r n a l P r e -p r o o f 

The weight gain is calculated according to formula (1):

Weight gain (wt.%) = ×100% (1) Where W 0 presents the original weight of PLA nonwovens before treatment, and W 1 is the weight after treatment.

The vertical burning test was carried out based on the standard ASTM D6413-13 using a JF-3 type instrument with the sample size of 30×8 cm 2 , and the LOI value was measured based on the standard GB/T 5454-1997 with the sample size of 15×6 cm 2 using CFZ-2 type instrument. The results were averaged by five parallel specimens.

Cone calorimeter tests were implemented according to ISO 5660 using a cone calorimeter (FTT, UK) under a heat flux of 35 kW/m 2 . Five identical PLA nonwovens with a size of 100 × 100× 1.8 mm 3 were superimposed as one sample, and the test results were averaged by five measurements.

The pyrolysis of PLA nonwovens was analyzed at smaller-scale combustion by using an MCC. Samples of 4.0±1 mg were heated from 25 o C to 750 o C at a heating rate of 1 o C/s under a mixing flow of N 2 (80 cc/min)/ O 2 (20 cc/min), the final result was also obtained by averaging five measurements.

Thermo Nicolet NEXUS 670 type spectrometers were used to collect the Fourier Transform Infrared Spectroscopy (FTIR) spectra by using a KBr pellet pressing J o u r n a l P r e -p r o o f method in a range of 4000~400 cm -1 .

The X-ray photoelectron spectroscopy (XPS) was carried out on an ESCALAB 250 (ThermoFisher Scientific USA) spectrometer with a source of monochromated Al

Kalph 150 W. The pass energy was 200 eV for a survey and 30 eV for high resolution scans.

2.4.6. Thermogravimetric Analysis (TGA)

The thermal stability was evaluated using a TA-Q50 apparatus, an alumina crucible contained 6.0±1.0 mg samples was heated from ambient temperature to 800 o C at a heat rate of 10 o C/min under N 2 atmosphere.

The microscopy images were obtained from a scanning electron microscopy (SEM) instrument (HITACHI S-4700 at a 20 kV beam voltage).

APTris and PLA nonwovens were calcined in a muffle (Thermo Scientific, FB-1310M) respectively according to a method reported elsewhere , and the calcined temperatures were determined according to the corresponding TG curves. 0.2 g APTris was calcined for 5 min at fixed temperatures (250, 275, 300, 350, 450, 550 , and 650 , respectively), 1.0 g PLA and 1.0 g PLA/25%APTris nonwovens were calcined simultaneously for 5 min at fixed temperatures (200, 250, 350, 400 , and 650 , respectively).

J o u r n a l P r e -p r o o f The FTIR spectra of APP, Tris, and APTris are shown in Fig. 1(a) . The peaks at 3367 cm -1 and 3203 cm -1 in the APTris curve belong to the stretching vibrations of -OH and N-H, the peaks in the range 2970 to 2850 cm -1 correspond to C-H of an aliphatic hydrocarbon, indicating the presence of Tris. Besides, the peaks at 1295 cm -1 , 1056 cm -1 , and 975 cm -1 are the absorbance of P=O, P-O, and P-OH in APTris, respectively (Chen et al., 2020; Yuan et al., 2018) , and the weakened relative intensity indicates that APP is successfully combined with Tris .

The elemental composition and chemical states of APTris and APP are investigated by XPS. The same element composition is found in the survey scanning spectra of APP and APTris in Fig. 1(b) . The predominant peaks correspond to C1s respectively. In the high resolution scanning of N1s in APP, it is fitted into two peaks ( Fig.1 (c) ), the first one at 401.6 eV is assigned to NH 4 + , the other at 399.6 eV is corresponding to -P-NH-P- (Camino et al., 1985; Shao et al., 2014) . However, N1s spectrum for APTris is fitted into two peaks at 400.5 and 401.8 eV ( Fig.1 (d) ), which is assigned to N-C derived from the reaction of APP and Tris (Jin et al., 2017) .

Meanwhile, Table 2 also gives the changes of composition obtained from XPS results.

The percentage of N, O, and P atomic in APTris decreases to 8.70%, 42.74%, and 7.69% respectively, which is lower than that of APP. Besides, the C atomic percentage increases from 12.03% to 39.87% because of the reaction of APP and Tris. Similar results are obtained from organic elemental analysis (OEA) measurement, the C content increases from 4.36% to 21.49%, and the N content decreases from 25.07% to 11.74% for APTris. As shown in Fig. 2 , 200 mg APTris and 200 mg APP (as a control group) are simultaneously calcined in muffle for 5 min at a different temperature to evaluate the thermal dilatability. Fig. 2(a) shows that the color of APTris turns to brown and then to black from white with the increase of temperature, the volume of the APTris is gradually expanding observed from Fig. 2(b) , which indicates that APTris has excellent quick thermal dilatability and carbonizing properties. The incorporated Tris acts as a blowing agent and a charring agent during combustion and plays an important role in achieving quick self-intumescence for APTris. Fig. 2 (c) displays the inner structure of the intumescent char layer of APTris, one can see that a cavity structure is formed by the expansion process. Besides, the carbonized temperature of J o u r n a l P r e -p r o o f

APTris is around 275 , which is lower than the decomposition temperature of PLA nonwovens. Besides, the char layer maintains a compact intumescent structure from 350 to 550 . Hence, the early char layer formed by APTris can well protect the underlying PLA nonwovens by slowing down the conduction of heat and the transfer of oxygen/volatile fuel. surface texture of nonwovens before and after treatment is minimal (Fig. S1 ). The surface microtopography of treated nonwovens and dispersion state of flame retardant can also observed in Fig. 3 . The original PLA nonwovens show a multilayer overlap structure with quite smooth surface in Fig. 3(a, a 1 ). For PLA/17%APP nonwoven sample in Fig. 3(b, b 1 ) , one can see most APP particles aggregate between fibers. The difference is that APTris affixed on fibers surface tightly and distributed evenly shown in Fig. 3(c, c 1 ) . It is supposed that it exist strong interfacial interaction between APTris and PLA, which is due to the polar polyhydroxy groups in APTris. Therefore, the compatibility of APTris is superior to that of APP in PLA

J o u r n a l P r e -p r o o f Fig. 4 and Table 3 . From Fig. 4(a) , we can see that untreated PLA nonwoven decomposes in the range of 350~420 , with a 10% weight loss temperature (T 10% ) of 366.5 and a char residue value of only 1.7 wt.% at 800 . After the introduction of APTris, the T 10% value gradually decreases with the amount of APTris but the final char residue increases at high temperature range. The earlier pyrolysis of APTris leads to hydroxyl dehydration and inert gas release, which promotes the crosslink carbonization and reduce melt droplets of PLA nonwovens. In addition, APTris makes contribution to reducing the maximum weight loss rate (DTG max ) from 2.95 to 2.08 %/ in Fig. 4(b) , and increasing char residues at 800 from 1.7 to 12.3 wt.%, the experimental char residue value is 30% higher than that of calculated value. High char residue indicates uncomplete combustion of polymeric matrix, which usually reflects better flame retardancy . It can be found the PLA/17%APTris sample exhibits higher char residue and lower DTG max value than the PLA/17%APP sample. TG analysis curves of treated PLA nonwovens under air atmosphere are also carried out and shown in Fig. S2 and Table S1 . We can see similar result to that under nitrogen atmosphere. 3.4. The fire performance The data obtained from LOI and vertical burning test is shown in Fig. 5 . LOI, molten dripping, and damaged length are given in Fig. 5 shows the combustion curves of the heat release rate (HRR), total heat release (THR), total smoking production (TSP), and charring residues rate. Table 4 collects some key data from the cone test. In Fig. 6(a, b) a: MLR m stands for the mean mass loss rate of a specimen during the flame combustion process. As a supplement to CCT, the micro-scale combustion behavior of PLA samples are measured by microscale combustion calorimeter test (MCC), which is a convenient and effective approach to evaluate the flammability of volatiles generated during pyrolysis with milligram scale specimen (Pan et al., 2015; Yang et al., 2010) .

As shown in Fig. 7 (a), a high peak heat release rate (pHRR) of about 794 W/g is observed for the untreated PLA sample. The pHRR value is remarkably decreased to 472 W/g for the PLA/25%APTris sample, reflecting that the incorporation of APTris suppresses the combustion intensity. Fig. 7(b) shows the total heat release (THR) and pyrolytic products are remained in condense-phase rather than release to vapor phase, which demonstrates APTris acts in the condensed phase (Yang et al., 2010) ; on the other hand, APTris generates phosphorus containing radicals to capture hydroxyl radicals, and inhibits the combustion. The MCC data also demonstrates APTris also acts in the gas phase. To analyze the morphology of char residues conduces to understand the flame retardation of the condensed phase . The digital photographs and SEM images of the char residue after the cone calorimeter test are shown in Fig. 8 .

Compared with the macromorphology of char residues in From Fig. 8(a-c) , we can see that the PLA nonwoven sample treated by APTris shows a more integrated morphology than that treated by APP. For PLA/17%APP sample, the residue displays serious breakage with many voids and crevices, and the charred tanglesome fibers arrange randomly instead of forming a continuous char layer in Fig. 8(a 1 , a 2 ) . While the char residue of PLA/17%APTris is more continuous and compact with less breakage in Fig. 8(b 1 , b 2 ) . The uniform adhesion and quick thermal dilatability of J o u r n a l P r e -p r o o f APTris contribute to the crosslinking of tanglesome fibers to form compact char layers. It is worthy noting that the char residue becomes unabridged and compact for the PLA/25%APTris sample. Some raised lines on the char residue surface can be observed in Fig. 8(c 1 , c 2 ) . It is suggested that the uncomplete pyrolysis fabrics of PLA nonwovens construct the skeleton of the char layer. The compact char layer is beneficial to hinder the transfer of heat, fuel, and oxygen, and leave more pyrolysis products in the condensed phase (Gong et al., 2020) . Therefore, the flame retardancy of PLA nonwovens is improved. In order to investigate the flame retardant mechanism of PLA/APTris, the pyrolysis and carbonization process was simulated by calcining PLA and PLA/25%APTris nonwoven samples in a muffle furnace. Five calcined temperatures (200, 250, 350, 400, 650 ) are selected according to the TG curves. As shown in Fig.   9 (a), the untreated PLA is intensively pyrolyzed into combustible volatiles without obvious swelling. For PLA/25%APTris sample, the early degradation corresponds to the emission of inert gases (NH 3 , H 2 O, etc.), which results in the foaming and swelling of carbonaceous char. The color of char residues for untreated PLA sample is brownish red, whilst that for PLA/25%APTris sample becomes focal black at 250 .

Finally, the carbon shell is formed at the presence of APTris after 400 .

Combined with the above analysis, the flame retardant mechanism of APTris is proposed and presented in Fig. 9(b) . Some PO· and PO 2 · free radicals generated from the decomposition of APTris capture HO· and H· free radicals in the gas phase, which blocks the chain reaction of combustion in the vapor phase (Salmeia et al., 2015) .

Even more important, APTris can self-crosslink, and expandquickly to form P-O-P, P-O-C network structures in the condensed phase, which is conducive to establish a physical barrier to hinder the transformation of oxygen, volatiles, and heat. The condensed phase flame retardant mechanism plays a dominant role. Hence, the smoke is timely suppressed and the flame retardancy of nonwovens is significantly improved.

Eco-friendly nonwovens are a potential alternative for the current commercial petroleum-based nonwovens, such as polyethylene terephthalate (PET) and polypropylene (PP). PLA nonwovens have been regarded as a green and sustainable textile in industry, owning to energy saving of production (25%-55% than petro-based polymers) and biodegradability (Rasal et al., 2010) . Therefore, PLA nonwovens have significant potential applications in garment industries, medical supplies, decoration, agricultural cultivation, and so on. For example, due to the coronavirus COVID-19, a mass of masks and protective personal equipment, made of polypropylene (PP) nonwoven material, have been used in the past several months (News, 2020), but the post-treatment of medical waste will face a baptism because of the difficult biodegradation for PP products. Therefore, biodegradable PLA nonwovens are a more ideal material to fabricate disposable protective equipment. The inherent flammability of PLA nonwovens is one of the limitations of its industrial application. PLA nonwovens can be fabricated via needle-punching, melt-blowing or spun-bonding.

The functional additives are generally incorporated during melt spinning process, but the choice for flame retardants is limited by many factors, such as the thermal stability, compatibility, solubility, etc. Besides, the spinnability of PLA containing flame retardants is usually reduced. Table 5 lists the fire performance and cost of flame-retardant PLA nonwovens from the published literature and this work. We can see APTris treated PLA nonwovens in this work is inexpensive, more feasible and higher efficiency than the chemical grafted (Cheng et al., 2016a) , spun-bonded (Maqsood and Seide, 2019) and other flame retardant treated (Cheng et al., 2016b) J o u r n a l P r e -p r o o f PLA nonwovens . The synthesis of APTris doesn't involve any toxic solvents, and the involved raw materials have reasonable price and rich source, which is suitable for industrial to produce cleaner flame retardant PLA nonwovens. 

A novel polyelectrolyte APTris was successfully prepared through ion-exchange reactions between APP and tris(hydroxymethyl) aminomethane. The incorporation of polyhydroxy Tris effectively increased the thermal dilatability and carbonizing properties of APP. The flame retardancy of PLA nonwovens treated with APTris was significantly improved. The presence of APTris effectively eliminated molten drops, greatly reduced the damaged length/area, and significantly decreased the pHRR, THR, TSP, HRC values of the PLA nonwoven samples. The condensed phase mechanism played a leading role. It was suggested that APTris rapidly expand and carbonize with the substrate to form compact protective layers, which restrained heat, smoke, and gas transfer during combustion. Meanwhile, the released inert gases diluted oxygen and J o u r n a l P r e -p r o o f combustible volatiles in the gas phase. This research has provided a new strategy for producing cleaner flame-retardant PLA nonwovens in the textile industry. Further investigation on improving the durability of flame retardant PLA nonwovens are undertaking in our laboratory.

Effect of combined flame retardant, liquid repellent and softener finishes on poly(lactic acid) (PLA) fabric performance

Main-chain poly(phosphoester)s: History, syntheses, degradation, bio-and flame-retardant applications

Flame retardancy of polylactide: an overview

Study of the mechanism of intumescence in fire retardant polymers: Part V-Mechanism of formation of gaseous products in the thermal degradation of ammonium polyphosphate

Inhibited combustion of graphene paper by in situ phosphorus doping and its application for fire early-warning sensor

Improvement of flame retardancy of poly(lactic acid) nonwoven fabric with a phosphorus-containing flame retardant

Phytic acid as a bio-based phosphorus flame retardant for poly(lactic acid) nonwoven fabric

A bio-resourced phytic acid/chitosan polyelectrolyte complex for the flame retardant treatment of wool fabric

Formation and properties of positively charged colloids based on polyelectrolyte complexes of biopolymers

Physical and mechanical properties of PLA, and their functions in widespread applications -A comprehensive review

Superior thermal and fire safety performances of epoxy-based composites with phosphorus-doped cerium oxide nanosheets

Biodegradable and bio-based polymers: future prospects of eco-friendly plastics

Flame suppression by aerosols derived from aqueous solutions containing phosphorus

The preparation of a bio-polyelectrolytes based core-shell structure and its application in flame retardant polylactic acid composites

The fire performance of polylactic acid containing a novel intumescent flame retardant and intercalated layered double hydroxides

Flame retardant polyester fabric from nitrogen-rich low molecular weight additives within intumescent nanocoating

Brominated flame retardants in the European chemicals policy of REACH-Regulation and determination in materials

Preparation and characterization of chitosan derivatives and their application as flame retardants in thermoplastic polyurethane

Flame retardant cellulosic fabrics via layer-by-layer self-assembly double coating with egg white protein and phytic acid

Novel bicomponent functional fibers with sheath/core configuration containing intumescent flame-retardants for textile applications

PLA composites: From production to properties

France has ordered 1 billion masks from China

Formation of self-extinguishing flame retardant biobased coating on cotton fabrics via Layer-by-Layer assembly of chitin derivatives

Hypophosphorous acid cross-linked layer-by-layer assembly of green polyelectrolytes on polyester-cotton blend fabrics for durable flame-retardant treatment

Study on flame retardant properties of poly(lactic acid) fibre fabrics

Brominated flame retardants in the urban atmosphere of Northeast China: Concentrations, temperature dependence and gas-particle partitioning

Poly(lactic acid) modifications

An Overview of Mode of Action and Analytical Methods for Evaluation of Gas Phase Activities of Flame Retardants

Perspectives for natural product based agents derived from industrial plants in textile applications -a review

An efficient mono-component polymeric intumescent flame retardant for polypropylene: preparation and application

The Development of a European Fire Classification System for Building Products -Test Methods and Mathematical Modelling

Simultaneous fire safety enhancement and mechanical reinforcement of poly(lactic acid) biocomposites with hexaphenyl (nitrilotris(ethane-2,1-diyl))tris(phosphoramidate)

The influence of cerium dioxide functionalized reduced graphene oxide on reducing fire hazards of thermoplastic polyurethane nanocomposites

An effective flame retardant containing hypophosphorous acid for poly (lactic acid): Fire performance, thermal stability and mechanical properties

Abrasion resistance of thermally bonded 3D nonwoven fabrics

Investigation of the flammability of different textile fabrics using micro-scale combustion calorimetry

Poorly-/well-dispersed graphene: abnormal influence on flammability and fire behavior of intumescent flame retardant

Is there any way to simultaneously enhance both the flame retardancy and toughness of polylactic acid?

Chitosan/Phytic Acid Polyelectrolyte Complex: A Green and Renewable Intumescent Flame Retardant System for Ethylene-Vinyl Acetate Copolymer

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

In situ growth of 0D silica nanospheres on 2D molybdenum disulfide nanosheets: Towards reducing fire hazards of epoxy resin