Physical Barrier Effect Research Articles

Al2O3/h‐BN/epoxy based electronic packaging material with high thermal conductivity and flame retardancy

AbstractThe long‐term and stable operation of integrated circuits and microelectronics requires packaging epoxy resin (EP) exhibit high thermal conductivity for efficient heat dissipation, and excellent flame retardancy in case of thermal runaway. We achieved such EP composite via filling poly‐dopamine (PDA) modified nanoscale Al2O3 spheres and microscale h‐BN sheets. The PDA modification increases the compatibility between fillers and EP and largely reduces the viscosity, improving the dispersion of fillers in EP thus the thermal conductivity of EP composites. In addition, NH3, H2O, and N2 generated during the combustion of phenolic hydroxyls and aminos in PDA combined with the physical barrier effect of Al2O3 and h‐BN can improve the flame retardancy of EP composites. As a consequence, the EP composite filled with PDA modified Al2O3 (26.67 wt%) and h‐BN (13.33 wt%) (i.e., PDA‐BNAO/EP) shows a thermal conductivity of 1.192 W/mK (654.9% of EP), a peak heat release rate of 194.9 W/g (33.8% of EP), and total heat release of 15.2 kJ/g (54.5% of EP), respectively. What's more, the viscosity of PDA‐BNAO/EP is 20,443 mPa s, which is only 20% of BNAO/EP (whose viscosity is 102,281 mPa s). More importantly, the PDA‐BNAO/EP has good dynamic mechanical properties with the storage modulus of 14.69 Gpa, glass transition temperature of 91.9°C and good electrical insulation, which is desired for packaging of microelectronics. PDA‐BNAO/EP composite should be a promising candidate for widespread packaging materials of microelectronics.

A Comparative Study of Chloride Adsorption Ability and Corrosion Protection Effect in Epoxy Coatings of Various Layered Double Hydroxides

The positive influence of chloride adsorption on the enhanced protection effect was always emphasized in the published literature. The concrete contribution of chloride adsorption and physical barrier effect of LDH in coatings still remains unclear at present. This work was aimed at exploring the significance of the chloride adsorption role of LDH in the corrosion protection of epoxy coatings. The synthesized LDH samples were characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) to show the influence of different parameters on its morphology, structure and composition, respectively. The corrosion-electrochemical behavior was investigated using electrochemical impedance spectroscopy (EIS) and salt spray test. It was found that although CaAl-LDH presented a lower chloride adsorption ability in comparison with other samples; it showed effective corrosion protection due to the higher physical barrier effect of CaAl-LDH with typically hexagonal and plate-like morphology due to good compatibility with the epoxy coatings. The results indicated that the corrosion protection effect of the incorporated LDH was more closely related to its physical barrier role rather than the role of the chloride adsorption, which was misunderstood in the previous publications. This work clarified the contribution comparison of the chloride adsorption and physical barrier of LDH in epoxy coating corrosion protection for the first time.

Effectiveness of physical barriers and enhanced fertilization in controlling predation on tilapia and catfish aquaculture systems by four piscivorous water bird families

Waterbirds cause substantial fish-stock losses in open aquaculture systems, particularly in developing countries where fish-ponds are smaller and predator control methods largely manual or under-resourced. This study: (1) used three fish-pond treatment meassures to assess their efficiencies in deterring predation pressure by four piscivorous waterbird families in small tilapia and catfish farms in western Kenya; and (2) distinguished bird group(s) most effectively deterred by these measures. The treatment measures were: coarse-grid wire mesh barriers; finer-grid wire barriers; and enhanced pond fertilization. Twelve fish-ponds were randomly sampled to assess birds' pond-neigborhood assemblages and their predation deterrence responses to pond treatment effects. Bird species richness was not affected by pond cover status, enhanced pond fertilization or type of pond cover barrier. However, pond-cover status, singularly and interactively with enhanced fertilization, reduced bird encounter rates while cover barrier type did not. Conversely, cover status, cover barrier type and fertilization each separately but not interactively contributed to improved deterrence to bird predation rates overall. However, while predation by families of larger birds was effectively reduced by enhancing pond fertilization or cover barriers, predation by families of smaller birds was prevented only by fine-grid chicken-mesh barriers. These results demonstrate that using enhanced fertilization and physical barriers can significantly contribute to reduction in predation pressure on open-culture pond-fish by most piscivorous birds, but may not always be effective if used separately. Effectiveness of combination of measures chosen will depend on types of target bird species and their feeding habits. The results constitute additional knowledge on field techniques useful in diversifying solution options for minimizing impacts of vertebrate predation on pond-fish stocks toward promoting sustainable aquaculture production and improving rural human nutrition.

A guanidine phosphate-assisted boron nitride network enabled simultaneous improvements in flame resistance and thermal conductivity of polyvinyl alcohol (PVA)

Polyvinyl alcohol (PVA) plays an important role in many fields, but its flammability in air limits its wider application. In this work, SiO2@BN, a flame-retardant and heat conductive filler, were synthesized by hydrolysis of ethyl orthosilicate, and its structure and morphology were characterized successfully. SiO2@BN and guanidine phosphate (GP) were mixed evenly in the solution and added to PVA to form PVA composites. Based on the data of thermal conductivity, limiting oxygen index (LOI) and cone calorimeter test (CCT), the thermal conductivity and flame retardancy of the composite were studied, and the flame retardancy mechanism was explained. The results showed that the thermal conductivity of the PVA composite added with 2 wt.% SiO2@BN and 8 wt.% GP was 82.4% higher than that of pure PVA, and its LOI value reached 28.4%, which was 38.5% higher than that of pure PVA. The peak heat release rate (pHRR) and total heat release (THR) of the composites was 65.2% and 44.4% lower than those of pure PVA, respectively. The main reasons were the physical barrier effect of BN and SiO2, the dilution of the noncombustible gas generated by the decomposition of GP when heated, and the dehydration and carbonization of PVA promoted by the generated phosphoric acid, metaphosphoric acid and other substances.

Multifunctional Epoxy-Based Electronic Packaging Material MDCF@LDH/EP for Electromagnetic Wave Absorption, Thermal Management, and Flame Retardancy.

The sharp reduction in size and increase in power density of next-generation integrated circuits lead to electromagnetic interference and heat failure being a key roadblock for their widespread applications in polymer-based electronic packaging materials. This work demonstrates a multifunctional epoxy-based composite (MDCF@LDH/EP) with high electromagnetic wave (EMW) absorption, thermal conductivity, and flame retardancy performance. In which, the synergistic effect of porous structure and heterointerface promotes the multiple reflection and absorption, and dielectric loss of EMW. A low reflection loss of -57.77dB, and an effective absorption bandwidth of 7.20GHz are achieved under the fillings of only 10 wt%. Meanwhile, a 241.4% enhanced thermal conductivity of EP is due to the high continuous 3D melamine-derived carbon foams (MDCF), which provides a broad path for the transport of phonons. In addition, MDCF@LDH/EP composite exhibits high thermal stability and flame retardancy, thanks to the physical barrier effect of MDCF@LDH combined with the high temperature cooling properties of NiAl-LDH-CO3 2- . Compared with pure epoxy resin, the peak heat release rate and the total heat release rate are reduced by 19.4% and 30.7%, respectively. Such an excellent comprehensive performance enables MDCF@LDH/EP to a promising electronic packaging material.

Novel organophosphonate-decorated WS2 nanosheets towards flame retardancy and mechanical enhancement of epoxy resin

By noncovalently surface-modifying 2D WS2 nanosheets (WC) with in situ generated iron ethylenediamine tetramethylene phosphonate (FeP), novel organophosphonate-decorated nanosheets (WC@FeP) were designed and prepared. Combining the physical barrier effects of WC nanosheets with the catalytic charring activity of FeP, WC@FeP improved the flame retardancy of the epoxy resin (EP), including heat inhibition and smoke suppression. Compared with those of neat EP, the EP composites containing 8 wt% of the WC@FeP (EP/8WC@FeP) passed a UL94 V-0 rating with a LOI value increased from 22.5 to 29.5 vol%. Furthermore, the peak heat release rate (PHRR), total heat release rate (THR), and total smoke release (TSP) of EP/8WC@FeP were remarkably reduced by 58.2%, 25.1%, and 44.5%, respectively. In addition, thanks to the large aspect ratio of the decorated nanosheets with flexible-but-tough nature, WC@FeP effectively enhanced the mechanical properties of the composites, in which the tensile strength and modulus of EP/8WC@FeP were enhanced by 23% and 24%, respectively, without sacrificing the toughness. Taking advantage of these features, the surface organo-decoration of 2D nanosheets broadens their applications in polymeric materials.

Pirfenidone-loaded hyaluronic acid methacryloyl hydrogel for preventing epidural adhesions after laminectomy.

It is inevitable that scar formation occurs between the spinal dura and surrounding tissues after laminectomy. While extensive epidural fibrosis, which results in limited nerve root activity and severe pain, is the main cause of postoperative failed-back surgery syndrome. Novel biomaterial loading effective drugs based on reasonable design are eagerly needed for the safe and effective prevention of epidural adhesions. We filtrated a suitable dose of pirfenidone (PFD) to load hyaluronic acid methacryloyl (HAMA) hydrogel in vitro. And then, we compare PFD-loaded HAMA hydrogel with only using PFD or HAMA hydrogels after laminectomy by in vivo studies in rats.We describe a safe and efficient anti-adhesive PFD-loaded HAMA hydrogel that prevents epidural fibrosis through the stable and sustained release of PFD. It was shown that the PFD-loaded HAMA hydrogel effectively inhibited cell penetration and suppressed collagen I/III expression. Thus, it effectively prevented the formation of adhesions through pharmacological and physical processes. The PFD-loaded HAMA hydrogel can effectively prevent adhesion formation in both pharmacological and physical barrier effects.

Self-doped poly(aniline-co-metanilic acid) copolymer coatings for enhancing the corrosion resistance of 304 stainless steel

Self-doped conducting poly(aniline-co-metanilic acid) (SPANI) copolymer coatings are electropolymerized for corrosion protection of 304 stainless steel (304SS) in a 0.3 M HCl solution. The synthesized SPANI coating is more compact and uniform, which exhibits improved barrier resistance to aggressive ions. The potentiodynamic polarization curve and electrochemical impedance spectroscopy results show that the SPANI copolymer coatings significantly suppress the corrosion current density, increase the charge transfer resistance, and effectively inhibit corrosion of the 304SS substrate. In addition, the SPANI copolymer coating exhibits a nondestructive topography after 120 h of immersion in a corrosive environment, which further confirms its superior protection performance. Owing to their enhanced physical barrier effect (compact coating surface with low porosity) and superior anodic protection, SPANI copolymer coatings are more corrosion resistant. Furthermore, the outcomes of the quantum chemical calculation and molecular dynamic simulation indicate that the SPANI copolymer chains are more stabilized and display favorable compatibility with the Fe (1 1 0) surface via electrostatic force. The better surface coverage and higher adsorption activity ensure an excellent chemical-anchor effect on the Fe (1 1 0) plane and thus achieve higher corrosion inhibition efficiency of the SPANI copolymer coatings.

Research for electrodeposited superhydrophobic Ni-W-WS2 coating and its anticorrosion and wear resistance

In this work, with the help of pulsed electrodeposition technology, Ni-W/WS2 superhydrophobic composite coatings on carbon steel surfaces were fabricated. Moreover, the effects of different WS2 concentrations on the surface morphology, microhardness, wear resistance and corrosion resistance of Ni-W coatings were also investigated. The results show that the addition of different concentrations of WS2 has a great influence on the microscale and submicron-sized roughness layered surface structure of the superhydrophobic coating surface. Furthermore, the embedding of WS2 also maximizes the wear and corrosion resistance of the Ni-W coating. This is reflected by the fact that the Ni-W/WS2 (0.3 g/L) composite coating possesses the narrowest wear section and the lowest average coefficient of friction (COF=0.14). In 3.5 wt%NaCl solution, the Ni-W/WS2 (0.3 g/L) composite coating has the highest corrosion potential (Ecorr=−0.309 V) and the lowest corrosion current density (icorr=1.415 μA·cm−2), which show the best corrosion resistance. The related enhancement mechanisms originate from the physical barrier effect of 2D nanosheets and the formation of tribo-transfer films.

Construction of a P–N–Si flame retardant coating on the cotton fabric with the integration of biomass carbon dots and ammonium polyphosphate

In order to improve the flame retardancy of cotton fabric, a kind of biomass carbon dots (CDs) particles were interspersed in the ammonium polyphosphate (APP) layer to achieve a new efficient CDs-based APP (CDs-APP) composite flame retardant by the integration technology. Then the CDs-APP layer was coated on the surface of cotton fabric. The microstructure and thermal stability of CDs-APP particle were characterized by the Transmission electron microscopy (TEM), Fourier infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The mass ratio of CDs to APP was 15.52%, which contains the C, O, N, Si and P elements, accounting for the 28.86%, 42.29%, 19.01%, 2.58% and 6.26%, respectively. The flame-retardant mechanism of CDs-APP was investigated by the limiting oxygen index (LOI), vertical combustion, cone calorimeter, thermogravimetric and thermogravimetric-infrared analysis. The results showed that, when the content of CDs-APP was about 10%, the LOI value of cotton fabric rose to 36.1%. The burning time and damage length have reduced to 4.5 s, 5.6 cm, respectively. And the fabric achieved B1 level. The addition of CDs-APP decreased the total heat release, heat release rate, total smoke emission and smoke emission rate of cotton fabric, among the peak-heat release rate has decreased by 55.78%. By quantifying the flame-retardant modes of CDs-APP, it displayed the superposition of physical barrier effect, flame inhibition effect and catalytic charring effect, accounting for 45.96%, 8.62% and 47.85%, respectively.Graphical abstract

Effectiveness of physical barriers in mitigating human–elephant negative interactions in North-East India

Physical barriers, like solar fences, elephant-proof trenches, stone, or rubble walls, are installed as conflict mitigation interventions in India’s major Asian elephant (Elephas maximus) ranges. However, installations lacking a priori scientific assessment of site specificity for reducing elephant incursion in the human settlements often fail in the intended goals of the resource-intensive management interventions. Since humans are central to conflict issues, research focusing on social aspects is essential for devising solutions. Despite the use of barriers in the Golaghat district in Assam, human–elephant conflict (HEC) cases are increasing, which offers an opportunity to evaluate their efficacy. Optimized hotspot analysis of the historic HEC records from 2010 to 2019 was done to check the spatial extent of the conflict and its dispersion in the district. We also assessed the efficiency of a 4.2-km long solar fence and a 2-km long elephant-proof trench through generalized linear modeling. We evaluated the encounter rates of elephant signs and other site covariates at the barrier and non-barrier sites. Multinomial logistic regression was applied to assess the perception of local people on the barriers and overall HEC in their areas based on their willingness to pay (WTP) for maintenance of the barriers. The highest cases occurred between 2016 and 2017, making up 25% of the total conflict cases. It was noticed that the extent of these hotspots was concentrated, and there was no dispersion of the conflict to other areas. Furthermore, a significant difference in the encounter rates of elephant signs between barriers and no barrier sites was observed. Solar fenced areas showed relatively lower encounter rates than areas with the trench, suggesting better efficiency of solar fencing than trench in the landscape. In addition, only five out of seven explanatory variables, viz., the persistence of HEC cases, amount of ex-gratia compensation, time taken in getting compensation, change in elephant behavior (incursion), and crop-raiding frequency significantly explained people’s perception of the barrier and non-barrier sites. According to local people, physical barriers are essential in managing HEC; hence, installing and maintaining solar fences in the high conflict hotspots is crucial for this landscape.

Novel bio-based lignosulfonate and Ni(OH)2 nanosheets dual modified layered double hydroxide as an eco-friendly flame retardant for polypropylene

In this paper, a functionalized layered double hydroxide (LDH-LS@Ni(OH)2) flame retardant was designed and fabricated based on a multi-modifier system consisting of lignosulfonate (LS) and Ni(OH)2 and used as a novel flame retardant for polypropylene (PP). In this multi-modifier system, LS as a compatibilizer and charring agent to improve compatibility and char yield, and Ni(OH)2 was utilized to improve the graphitization of char residual, resulting in a PP/LDH-LS@Ni(OH)2 composite with higher thermal stability. With the addition of LDH-LS@Ni(OH)2 was only 15 wt%, the PP/LDH-LS@Ni(OH)2 composite achieved a limiting oxygen index (LOI) of 30.8% and passed the UL-94 V-0 rating. At the same time, the peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) were significantly reduced by 62.7%, 29.5%, and 46.2%, respectively. The flame retardant properties of LDH-LS@Ni(OH)2 were mainly due to the catalytic charring effect of the transition metal elements and the physical barrier effect of the hydrotalcite. More specifically, as a highly efficient flame retardant, LDH-LS@Ni(OH)2 has promising potential in reducing the fire hazards of PP composites.

A novel P/Ni-doped g-C3N4 nanosheets for improving mechanical, thermal and flame-retardant properties of acrylonitrile–butadienestyrene resin

The ubiquitous application of highly flammable acrylonitrile–butadienestyrene (ABS) resin has brought great fire threat to human and environment. Unfortunately, current flame retardants often improve flame retardancy but reduce mechanical and thermal properties, seriously affecting their practical application. We herein reported novel multifunctional, high-efficiency, phosphorus and nickel co-doped graphitic carbon nitride (Ni-P-C3N4) nanoflakes to address the trade-off between flame retardancy and mechanical/thermal properties. The addition of 2.0wt% of Ni-P-C3N4 increased the initial degradation temperature and tensile strength of ABS composite (ABS/Ni-P-CN2) by 15 °C and 24.3% relative to virgin ABS, indicating its positive effect on thermal and mechanical properties. Compared with ABS, ABS/Ni-P-CN2 exhibited a notable increase in time to ignition, along with 32.4% and 33.8% reductions in peak heat release rate (PHRR) and peak smoke production rate (PSPR), demonstrating excellent anti-ignition, flame-retardant and smoke-suppressive performances. The increased fire safety was mainly due to the physical barrier effect of g-C3N4 nanosheets and the catalytic charring effect of P and Ni. This work offers a novel design strategy to create multifunctional flame retardants for fabricating fire-safe polymer composites with superior thermal and mechanical properties, holding great potential in industries.

Qualitative and Quantitative Correlation of Microstructural Properties and In Vitro Glucose Adsorption and Diffusion Behaviors of Pea Insoluble Dietary Fiber Induced by Ultrafine Grinding.

Ultrafine grinding is an important pretreatment to achieve the physical modification of dietary fiber. In this study, ultrafine grinding treatments were performed for different times to give pea insoluble dietary fiber (PIDF) samples with varied particle sizes (D50). The correlations and quantitative relationships between the microstructures of multi-scales PIDF and its in vitro glucose adsorption and diffusion behaviors were comprehensively evaluated. The results indicated that the specific surface area (SSA), pore volume (PV) and oxygen-to-carbon surface ratio (O/C) of PIDF were significantly increased by ultrafine grinding at the cellular scale, while D50 and cellulose crystallinity (CrI) were significantly decreased. These changes significantly improved the glucose adsorption capacity (GAC) of PIDF. The order of importance of microstructural changes on GAC was O/C > PV > SSA > CrI > D50. GAC showed positive exponential relationships with SSA, PV, and O/C and showed a negative linear relationship with CrI. The ability to retard glucose diffusion increased significantly with decreased fiber particle size because of improved adsorption and interception of glucose and the dense physical barrier effect of PIDF. The quantitative equation of maximum glucose dialysis retardation index was GDRImax = −1.65 ln(D50) + 16.82 ln(GAC) − 68.22 (R2 = 0.99). The results could provide theoretical support for quantitative and targeted intervention of dietary fiber structure for blood glucose control.

Preparation and corrosion resistance of epoxy resin coating for bonded NdFeB magnet

The epoxy resin (ER) coatings were coated on ring-shaped bonded NdFeB magnet (RSM) using air spraying and cathodic electrophoresis deposition processes. The morphologies and microstructures of the bare RSM (B-RSM), sprayed ER/RSM (S-ER/RSM) and electrophoretic ER/RSM (E-ER/RSM) were observed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), 3D laser confocal scanning microscopy (LSCM) and fourier infrared spectrometer (FTIR). The corrosion behaviors of the ER coatings were analyzed by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and neutral salt spray test (NSS). The results showed that ER coatings covered the pores of B-RSM well and played a good sealing role. Moreover, E-ER/RSM had a more uniform film layer and better surface leveling than S-ER/RSM. Compared with B-RSM and S-ER/RSM, the corrosion current density (Icorr) of E-ER/RSM reached 1.904 × 10−5 A/cm2, one order of magnitude lower than that of B-RSM (1.033 × 10−4 A/cm2) and about twice lower than that of S-ER/RSM (4.728 × 10−5 A/cm2). The value of charge transfer resistance (Rct) of E-ER/RSM is 1671.6 Ω·cm2, which is higher than that of both B-RSM (236.96 Ω·cm2) and S-ER/RSM (425.46 Ω·cm2). The NSS time of E-ER/RSM reached 144 h, longer than that of S-ER/RSM (72 h) and B-RSM (24 h). The corrosion resistance of bonded NdFeB magnets was improved due to the good shielding properties and physical barrier effect of the ER coatings. In addition, the corrosion mechanisms of ER coatings were discussed in detail.

PH-responsive bimetallic Ce-ZIF-8 nanocontainer for the active corrosion protection of Al alloys

In this study, novel pH-sensitive bimetallic Ce-ZIF-8 nanocontainers are loaded with benzotriazole (BTA) corrosion inhibitors and then decorated with a polydopamine (PDA) shell. The applied PDA layer acts as an acid-responsive gatekeeper, controlling the intelligent release of the encapsulated inhibitors and also preventing their self-leakage. UV–vis and ICP-OES tests indicate that the BTA and cerium inhibitors release slowly in the neutral 3.5 wt% NaCl solution. Afterward, the designed pH-responsive Ce-ZIF-8-BTA-PDA nanocontainers are dispersed uniformly in the epoxy matrix as a novel intelligent filler. EIS results demonstrate that the incorporation of Ce-ZIF-8-BTA-PDA nanocontainers significantly improves the corrosion resistance of epoxy coatings, in which the low-frequency impedance is about three orders of magnitude higher than that of the pure epoxy coating after 60 days of immersion. Furthermore, the low-frequency value of the scratched Epoxy-Ce-ZIF-8-BTA-PDA coating increases from 5.05 × 105 Ω cm2 to 8.83 × 105 Ω cm2 after 8 h of exposure to the 3.5 wt% NaCl solution, confirming their outstanding self-healing performance. The excellent corrosion protection and self-healing ability are due to the incorporation of the Ce-ZIF-8-BTA-PDA nanocontainers, improving the surface compactness and therefore enhancing the physical barrier effect. Moreover, the intelligent release of the encapsulated corrosion inhibitors provides active corrosion protection performance by forming a dense protective film on the Al alloy surface when the coating is damaged. Meanwhile, the highly dispersed nanocontainers lengthen the diffusion path of corrosive ions and therefore extend the service life of the epoxy coatings in aggressive environments. This new type of acid-responsive smart coating based on the bimetallic Ce-ZIF-8 nanocontainers has the potential to broaden the future applications of active corrosion protection of metals.

In situ phase separation of novel phosphorus-containing polyester in epoxy resins towards simultaneously improved thermal conductivity and fire safety

Polymeric thermal management materials (PTMMs) attained with expected thermally conductive performance and flame retardancy are still urgently being required. Herein, a novel phosphorus-containing polyester named poly(bis(1,1’-biphenoxyl)hexyl 5-(diphenylphosphoryl-amino)isophthalate) (PBHPI) was synthesized and incorporated into the epoxy resin (EP). After curing with 4,4’-diaminodiphenyl sulfone (DDS), in situ networks were obtained via reaction-induced phase separation (RIPS) between PBHPI and EPDDS, which induced the preferable distribution of boron nitride nanosheets (BNNSs) at the interface between the PBHPI-rich and EP-rich phases; therefore the photon transmission pathways were constructed. Due to the flame inhibition activity of PBHPI and the physical barrier effect of BNNSs, EPDDS/PBHPI/BNNSs composites exhibited expected fire safety performance of heat insulation and smoke suppression in cone calorimetry: the peak heat release rate (PHRR) reduced by 60%, total heat release (THR) by 40% and total smoke production (TSP) by 41%, compared with EPDDS. In addition, the incorporation of barely 1 wt% BNNSs improved the thermal conductivity of the composites. This work combining the molecular design of the novel phosphorus-containing polyester and the RIPS methods to construct in situ networks provided a feasible solution and unique insight into the design of PTMMs in a facile and convenient way.

Enhanced flame retardancy level of a cotton fabric treated by an ammonium pentaborate doped silica-KH570 sol

Tetraethoxysilane (TEOS), γ- (methacryloyloxy) propyltrimethoxysilane (KH570) and ammonium pentaborate (AP, NH4B5O8) were used as a precursor, silane coupling agent and flame retardant additive to prepare a series of single (SiO2), composite (SiO2-KH570) and doped (SiO2-KH570-AP) sols via sol-gel processes. The sols were post finished to cotton fabrics through dipping-curing methods. Results show that as-prepared sol-gel systems are successfully deposited on cotton fabrics. SiO2-KH570-AP@COT shows the highest initial pyrolysis temperatures (296.4°C), char residue rate (31.5%), LOI (24.0%) and ΔLOI/Δm (4.75%/g), the most beneficial after-flame time (14.1 s) and after-glow time (0.0 s), the most complete char residue (30.0 cm), the second highest maximum pyrolysis temperature (356.6°C) and an effective synergistic effectiveness parameter (>1.0). Its flame retardancy is mainly promoted by both individually positive and jointly synergistic actions of silica sol (strong physical barrier and structural support effects in enhancing thermal stability and providing char frame), KH570 (strong coupling effect in combining components and reinforcing interface properties between components and cotton fibers) and AP (release of water molecules for cooling burning zone, diluting and isolating oxygen and gaseous products and promoting char formation). The flame-retardant treatment deteriorated the tensile strength of cotton fabrics.

Flame Retardant Strategies and the Physical Barrier Effect of Nanoparticles to Improve the Thermal Performance of a Polymer

Flame Retardant Strategies and the Physical Barrier Effect of Nanoparticles to Improve the Thermal Performance of a Polymer

Enhanced flame retardant performance of rigid polyurethane foam by using the modified OMMT layers with large surface area and ammonium polyphosphate

A phosphorus-containing organosilicon compound (PCOC) was synthesized and used to modify organic-montmorillonite named M-OMMT. The results showed that the interlayer spacing of the intercalated M-OMMT layers became larger and the exfoliated M-OMMT layers were connected by PCOC after the modification. Then, M-OMMT was combined with ammonium polyphosphate (APP) to improve the flame retardancy of rigid polyurethane foam (RPUF) composites. The thermal stability and flame retardancy of RPUF with M-OMMT and APP was lucubrated using thermogravimetric analysis (TGA), limited oxygen index (LOI) and cone calorimeter test. After the addition of modified OMMT layers, the Td,5%, Tmax1 and Tmax2 of RPFU/APP/M-OMMT (234 °C,304 °C and 462 °C) were all higher in contrast to RPUF/APP/OMMT (223 °C, 298 °C and 454 °C). Compared with RPUF/APP/OMMT, the peak heat release rate and total smoke release of RPUF/APP/M-OMMT were apparently reduced from 292 kW/m2 and 552 m2/ m2 to 156 kW/m2 and 350 m2/ m2, and the residual char yield increased by 37%. The SEM results showed that the addition of M-OMMT promoted the formation of a more compact and intumescent char layer. After the modification of PCOC, the layers of M-OMMT overlapped each other to form a larger surface area, which can exert a better physical barrier and protective effect together with APP on RPUF, fabricating the RPUF/APP/M-OMMT composite with the good flame-retardant property.