An efficiently halogen-free flame-retardant long-glass-fiber-reinforced polypropylene system

Comparative catalytic reduction and degradation with biodegradable sodium alginate based nanocomposite: Zinc oxide/N-doped carbon nitride/sodium alginate

Sodium alginate (SA) is a biodegradable macromolecule which is used to synthesize nanocomposites and their further use as catalysis. Zinc oxide (ZnO) and nitrogen doped carbon nitride (ND-C3N4) nanoparticles are prepared using solvothermal and hydrothermal methods, respectively. ZnO/ND-C3N4/SA nanocomposites are successfully synthesized by employing in-situ polymerization. The presence of essential functional groups is confirmed by Fourier transform infrared (FTIR) spectroscopic analysis. Controlled spherical morphology for ZnO nanoparticles, with an average diameter of ∼52 nm, is shown by Scanning electron microscopic (SEM) analysis, while rice-like grain structure with an average grain size ∼62 nm is exhibited by ND-C3N4 nanoparticles. The presence of required elements is confirmed by Energy dispersive X-ray spectroscopic (EDX) analysis. The crystalline nature of nanocomposites is verified by X-ray diffraction spectroscopic (XRD) analysis. The investigation of the catalytic efficiency for degradation and reduction of various organic dyes is carried out on nanoparticles and nanocomposites. Thorough examination and comparison of parameters, such as apparent rate constant (kapp), reduction time, percentage reduction, reduced concentration and half-life, are conducted for all substrates. The nanocomposites show greater efficiency than nanoparticles in both reactions: catalytic reduction and catalytic degradation.

Advances in Polymeric Neutron Shielding: The Role of Benzoxazine-h-BN Nanocomposites in Nuclear Protection

Given their substantial neutron capture cross-section, extreme hardness, and high chemical and thermal stability, boron-based materials are widely used as building blocks to protect against highly ionizing radiations such as gamma rays and neutrons. Indeed, uncontrolled nuclear radiation exposure can be highly hazardous to radiation workers and the public. In this sense, this work presents an extensive study and experimental evaluation of the nuclear shielding features of hexagonal-boron nitride (h-BN) based nanocomposite, where bisphenol-A based polybenzoxazine (BA-PBz) was used as matrix. The neutron shielding studies were carried out at the nuclear research reactor of Algeria NUR. The surface treatment of h-BN nanoparticles was confirmed by FTIR and XPS techniques. The curing behavior and the degradation phenomena of the nanocomposites were evaluated by DSC-TGA analyses. The distribution of h-BN nanoparticles within the polymer matrix was assessed by TEM and SEM. The results showed that the developed boron nitride-based nanocomposite exhibits intriguing shielding performances and good thermal stability. The DSC-TGA tests exhibit high degradation temperature that reach 279°C. The highest performances were obtained at an h-BN concentration of 7 wt%, where the macroscopic cross was found to be (Σ = 3.844 cm-1) with a screening ratio of (S = 96.12%), equivalent to a mean free path (λ) of 0.138 cm.

Optimisation of Additives to Maximise Performance of Expandable Graphite-Based Intumescent-Flame-Retardant Polyurethane Composites

The effect of varying the weight percentage composition (wt.%) of low-cost expandable graphite (EG), ammonium polyphosphate (APP), fibreglass (FG), and vermiculite (VMT) in polyurethane (PU) polymer was studied using a traditional intumescent flame retardant (IFR) system. The synergistic effect between EG, APP, FG, and VMT on the flame retardant properties of the PU composites was investigated using SEM, TGA, tensile strength tests, and cone calorimetry. The IFR that contained PU composites with 40 wt.% EG displayed superior flame retardant performance compared with the composites containing only 20 w.t.% or 10 w.t.% EG. The peak heat release rate, total smoke release, and carbon dioxide production from the 40 wt.% EG sample along with APP, FG, and VMT in the PU composite were 88%, 93%, and 92% less than the PU control sample, respectively. As a result, the synergistic effect was greatly influenced by the compactness of the united protective layer. The PU composite suppressed smoke emission and inhibited air penetrating the composite, thus reducing reactions with the gas volatiles of the material. SEM images and TGA results provided positive evidence for the combustion tests. Further, the mechanical properties of PU composites were also investigated. As expected, compared with control PU, the addition of flame-retardant additives decreased the tensile strength, but this was ameliorated with the addition of FG. These new PU composite materials provide a promising strategy for producing polymer composites with flame retardation and smoke suppression for construction materials.

Flame-retardant properties and mechanism of LGF/PBT/DOPO-HQ-conjugated flame-retardant composites

In this article, long fiber reinforced polybutylene terephthalate (LGF/PBT/DOPO-HQ) flame-retardant composites were prepared using 10-(2,5-dihydroxy phenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) as the conjugated flame-retardant. The effects of different flame-retardant contents on the combustion properties of the composites were investigated. The results showed that after adding 14% of DOPO-HQ, the flame-retardant effect of the composite reached the V-0 level of UL-94 fire rating with an ultimate oxygen index (LOI) of 26.4%. The average heat release rate (Av-HRR), peak heat release rate (PHRR), and total heat release rate (THR) decreased by 45.9, 56.5, and 32.6%, respectively. This shows that LGF/PBT/DOPO-HQ composite has good flame-retardant properties. Meanwhile, the flame-retardant mechanism of cohesive phase and gas-phase synergy during the combustion of flame retardants was analyzed by carbon layer morphology and dynamic thermal decomposition.

Highly Flame-Retardant and Low Heat/Smoke-Release Wood Materials: Fabrication and Properties

Wood is an important renewable material exhibiting excellent physical and mechanical properties, environmental friendliness, and sustainability, and has been widely applied in daily life. However, its inherent flammability and susceptibility to fungal attack greatly limit its application in many areas. Use of fire-retardant coatings and preservatives has endowed wood with improved safety performance; importantly, the cooperative effect of dual treatments on the burning behavior and flame retardancy of wood needs to be better understood. Here, a two-step treatment for wood is proposed, with a copper–boron preservative (CBP) and a fire-retardant coating. The thermal degradation and burning behavior of treated wood were investigated. The CBP formed a physical barrier on the wood surface, facilitating a charring process at high temperatures and thus suppressing the release of heat and smoke. Notably, the dual-treated wood exhibited lower heat release and reduced smoke emission compared with the mono-treated wood, indicating a cooperative effect between CBP and fire-retardant coatings, beneficial to the improvement of fire safety. This experimental work improved fire retardance and suppressed smoke release in flammable materials, and offers a new design for developing fire-retardant coatings.

Mechanical Properties of Polypropylene-Based Flame Retardant Composites by Surface Modification of Flame Retardants

A flame retardant refers to a substance that can be added to a material having the property of being efficiently combusted to improve the material physically and chemically. It should not affect the physical properties required for the final product. Halogen-based compounds are representative flame retardants with excellent flame retardancy. However, their use is limited due to restrictions on the use of chemicals introduced due to human safety. Magnesium hydroxide, one alternative material of halogen flame retardants, is widely used as an eco-friendly flame retardant. However, the most significant disadvantage is high load. To find a solution to this problem, many studies have been conducted by mixing magnesium hydroxide with other additives to create a synergistic effect. In this study, flame retardancy and mechanical properties of polypropylene-based flame retardant composites as a function of mixing surface-modified magnesium hydroxide with phosphorus-based flame retardants were investigated. All materials including PP, additives, and flame retardants were mixed using an extrusion process. Specimens were prepared by an injection process of the compound made after mixing. As a result of the evaluation of the mechanical properties by the modified flame retardant, the relational expression of the mechanical performance degradation as a function of the amount of addition was obtained, and the tensile (CBATS) and bending strength (CBABS) were performed on the amount of flame retardant added. The relational expression obtained in this study is considered to be a formula for predicting the strength reduction according to the addition amount of the modified flame retardant and can be used in industry. In addition, it was found that the addition amount of the modified flame retardant had a greater effect on the lowering of the bending strength.

The Flame-Retardant Mechanisms and Preparation of Polymer Composites and Their Potential Application in Construction Engineering

Against the background of people's increasing awareness of personal safety and property safety, the flame retardancy (FR) of materials has increasingly become the focus of attention in the field of construction engineering. A variety of materials have been developed in research and production in this field. Polymers have many advantages, such as their light weight, low water absorption, high flexibility, good chemical corrosion resistance, high specific strength, high specific modulus and low thermal conductivity, and are often applied to the field of construction engineering. However, the FR of unmodified polymer is not ideal, and new methods to make it more flame retardant are needed to enhance the FR. This article primarily introduces the flame-retardant mechanism of fire retardancy. It summarizes the preparation of polymer flame-retardant materials by adding different flame-retardant agents, and the application and research progress related to polymer flame-retardant materials in construction engineering.

Synthesis of a Novel Phosphorous-Nitrogen Based Charring Agent and Its Application in Flame-retardant HDPE/IFR Composites

In this work, a novel phosphorous-nitrogen based charring agent named poly(1,3-diaminopropane-1,3,5-triazine-o-bicyclic pentaerythritol phosphate) (PDTBP) was synthesized and used to improve the flame retardancy of high-density polyethylene (HDPE) together with ammonium polyphosphate (APP). The results of Fourier transform infrared spectroscopy (FTIR) and ¹³C solid-state nuclear magnetic resonance (NMR) showed that PDTBP was successfully synthesized. Compared with the traditional intumescent flame retardant (IFR) system contained APP and pentaerythritol (PER), the novel IFR system (APP/PDTBP, weight ratio of 2:1) could significantly promote the flame retardancy, water resistance, and thermal stability of HDPE. The HDPE/APP/PDTBP composites (PE3) could achieve a UL-94 V-0 rating with LOI value of 30.8%, and had a lower migration percentage (2.2%). However, the HDPE/APP/PER composites (PE5) had the highest migration percentage (4.7%), lower LOI value of 23.9%, and could only achieve a UL-94 V-1 rating. Besides, the peak of heat release rate (PHRR), total heat release (THR), and fire hazard value of PE3 were markedly decreased compared to PE5. PE3 had higher tensile strength and flexural strength of 16.27 ± 0.42 MPa and 32.03 ± 0.59 MPa, respectively. Furthermore, the possible flame-retardant mechanism of the APP/PDTBP IFR system indicated that compact and continuous intumescent char layer would be formed during burning, thus inhibiting the degradation of substrate material and improving the thermal stability of HDPE.

The Effect of Ultraviolet Ageing on the Flame Retardancy, Thermal Stability and Mechanical Properties of LGFPP/IFR

In this work, long glass fibre reinforced polypropylene/intumescent flame retardants (LGFPP/IFR) composites are exposed to ultraviolet (UV) radiation with wavelength of 340 nm for 0–800 h. The effects of UV ageing on the flame retardancy, thermal stability and mechanical properties of LGFPP/IFR composites are investigated and discussed by limiting oxygen index (LOI), UL–94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), mechanical properties and energy dispersive X-ray analysis (EDAX). A slight variation in LOI values and UL-94 levels are observed, and CCT results display a lower heat release rate for all aged samples. The TGA result also shows that aged samples have a higher degradation temperature with the prolongation of the aging time. EDAX showed higher content of the O, P and N elements on the surface of samples after 600 h ageing, which means partly gathering of IFR particles. The tensile, bending and impact strengths decrease after ageing, and the fracture morphology shows that interface debonding occurs.

Facile synthesis of a flame retardant melamine phenylphosphate and its epoxy resin composites with simultaneously improved flame retardancy, smoke suppression and water resistance

A flame retardant melamine phenylphosphate (MPhP) was facilely synthesized by the reaction of phenylphosphoric acid (PPA) and melamine (MEL), and was characterized by FTIR and NMR. Epoxy resin (EP) composites containing MPhP were prepared, and the effect of MPhP content on flame retardancy, smoke suppression, mechanical properties and thermal stability of the composites was investigated. It is observed that the LOI of the EP composite with 20 wt% MPhP (EP/MPhP20) is 26.5%, and the composite EP/MPhP20 reaches a UL 94 V-0 rating. Cone calorimeter test results show that the peak heat release rate, total heat release and total smoke release of EP/MPhP20 decrease by 51%, 34%, and 24%, respectively compared with those of pure EP. The flame retardancy of the EP/MPhP composites after the water treatment at 80 °C for 72 h is basically maintained, indicating that the composites have good water resistance. The mechanical strengths of the EP/MPhP composites decrease gradually with an increase in the MPhP content. Moreover, the thermal stability of the EP/MPhP composites was studied.

Functionalized allylamine polyphosphate as a novel multifunctional highly efficient fire retardant for polypropylene

In this study, an efficient novel allylamine polyphosphate (AAPP) as a flame retardant (FR) crosslinker is used to improve the thermal stability of flame retarded polypropylene (PP) composites under electron beam treatment.

A highly efficient gas-dominated and water-resistant flame retardant for non-charring polypropylene

In this work, a novel mono-component and gas-dominated flame retardant, named DPPIP, was prepared through an amidation reaction of diphenylphosphinyl chloride and piperazine, and used to flame retard PP.

Efficient organic–inorganic intumescent interfacial flame retardants to prepare flame retarded polypropylene with excellent performance

An efficient and simple approach for the preparation of organic–inorganic intumescent interfacial flame retardants, aiming at enhancing the flame-retardant efficiency and interfacial adhesion between matrix and flame retardants was presented.

Effect of Brominated Epoxy Resins on the Thermal Stability and Flame Retardancy of Long-Glass-Fiber Reinforced Polyamide 6

In this work, the compounds of brominated epoxy resins and antimony trioxide (BER/Sb2O3) additives are analyzed and added into long-glass-fiber reinforced polyamide 6 (PA6/LGF) composites in order to solve the “candle-wick effect” caused by glass fibers. The thermal stability, flammability, and morphology of charred residues of the flame retardant PA6/LGF composites are investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), and scanning electronic microscopy (SEM). The results show the addition of BER/Sb2O3 provides improvements in flame retardancy by increasing the LOI values, enhancing UL-94 rating, and reducing the heat release rate, total heat release and effective heat of combustion due to the formation of consolidated and thick charred residual structures on the surfaces of the LGF reinforced PA6 composites. When the content of BER/Sb2O3 is increased to 12 wt%, the LOI value and UL-94 rating of BER/PA6/LGF composites reach 24.8 and V-0, respectively. The TGA results exhibit that the decomposition temperature of the PA6/LGF composites decreases with the addition of BER/Sb2O3 additive, resulting in forming some high quality residual char layer. A possible flame retardant mechanism is proposed to illustrate the effect of the gaseous and condensed phases on the flame retardancy of the PA6/LGF composites.

Key Role of Reinforcing Structures in the Flame Retardant Performance of Self-Reinforced Polypropylene Composites

The flame retardant synergism between highly stretched polymer fibres and intumescent flame retardant systems was investigated in self-reinforced polypropylene composites. It was found that the structure of reinforcement, such as degree of molecular orientation, fibre alignment and weave type, has a particular effect on the fire performance of the intumescent system. As little as 7.2 wt % additive content, one third of the amount needed in non-reinforced polypropylene matrix, was sufficient to reach a UL-94 V-0 rating. The best result was found in self-reinforced polypropylene composites reinforced with unidirectional fibres. In addition to the fire retardant performance, the mechanical properties were also evaluated. The maximum was found at optimal consolidation temperature, while the flame retardant additive in the matrix did not influence the mechanical performance up to the investigated 13 wt % concentration.

Microencapsulation of ammonium polyphosphate with melamine-formaldehyde-tris(2-hydroxyethyl)isocyanurate resin and its flame retardancy in polypropylene

The reaction scheme of MFT resin pre-polymer.

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

We found in our previous study that ethylenediamine- or ethanolamine-modified ammonium polyphosphates could be used alone as an intumescent flame retardant for polypropylene (PP), but their flame-retardant efficiency was not very high. In this present work, a novel highly-efficient mono-component polymeric intumescent flame retardant, piperazine-modified ammonium polyphosphate (PA-APP) was prepared. The oxygen index value of PP containing 22 wt % of PA-APP reached 31.2%, which increased by 58.4% compared with that of PP with equal amount of APP, and the vertical burning test (UL-94) could pass V-0 rating. Cone calorimeter (CC) results indicated that PP/PA-APP composite exhibited superior performance compared with PP/APP composite. For PP containing 25 wt % of PA-APP, fire growth rate (FGR) and smoke production rate (SPR) peak were reduced by 86.4% and 78.2%, respectively, compared with PP blended with 25 wt % APP. The relevant flame-retardant mechanism of PA-APP was investigated by Fourier transform infrared spectroscopy etc. The P-N-C structure with the alicyclic amine was formed during the thermal decomposition of piperazine salt (-NH2(+)-O-P-), and the rich P-N-C structure facilitated the formation of stable char layer at the later stage, consequently improving the flame-retardant efficiency of APP.

Synthesis and Properties of a Novel Intumescent Flame Retardant and its Application in LLDPE

In this study, a novel phosphorus-containing flame retardant (IFR) of spirocyclic pentaerythritol diphosphonate dinitroguanidine (SPDD) was successfully synthesized, which was characterized by 1H NMR, 31P NMR and FTIR spectra. At the same time, the SPDD was used in LLDPE to prepare flame-retardant materials whose flammability and thermal behavior were studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and scanning electron microscopy (SEM). The TGA data showed that SPDD could effectively enhance the thermal stability and char residue of LLDPE/IFR composite. And with the increase of SPDD, the LOI value of LLDPE/IFR increases obviously. When SPDD reached 30 wt%, the LOI value of LLDPE/IFR reaches 31 %. The SEM also shows the surface of intumescent chars of LLDPE/IFR (30 %) has many sphere-like swollen bubbles.