EVA Composites Research Articles

Optimisation of the ceramic-like body for ceramifiable EVA-based composites

AbstractVarious ceramifiable ethylene-vinyl acetate copolymer (EVA) composites were prepared by melt blending with two kinds of glass frits, organically modified montmorillonite (OMMT) and whitened and capsulised red phosphorus (WCRP). The influence of different filler components and firing temperatures on the ceramifiable properties of the composites was studied. The dripping behaviour of the composites was analyzed by a vertical burning test. The microstructure of the residues was characterised by X-ray diffraction (XRD) and scanning electron microscopy. The results showed that the optimised EVA composite was free of melt dripping during burning with the addition of OMMT. A dimensionally stable and dense ceramic residue was also obtained, especially with the addition of WCRP. It was suggested that new phases were formed at firing temperatures, and WCRP could promote the formation of ceramic body which was not fused during firing at 900°C as evidenced by XRD.

Effects of ZnO particles on space charge of EVA copolymer for HVDC cable accessory insulation

The performance of cable accessories, as an essential part of the HVDC networks, is a great concern to the reliability of the system. Cable accessories made of ethylene-vinyl acetate copolymer (EVA) by incorporation of specific fillers have to face the problem of space charge accumulation and become more unpredictable considering the complex conditions. The effects of doping contents on the space charge behaviors of EVA/ZnO composite are not completely clear, which need further investigation. In this paper, EVA composites were prepared by incorporating ZnO nanoparticles into EVA matrix with fraction of 0, 1, 5 and 10 wt% respectively, with which 5 wt% nano-sized plus 5 wt% micro-sized ZnO doped samples were chosen for comparison. The dependence of dielectric properties and conduction current on the doping contents was measured. PEA method was applied to research the space charge behaviors of EVA composites under -25 kV/mm. Obtained results show that the particles in EVA composite are in homodisperse. The permittivity is increased by ZnO doping and the dissipation factor of EVA composites with 1 and 5 wt% nanoparticles is lower at the lower frequencies. The homocharges injection occurs in cathode instead of anode when ZnO nanoparticles are introduced and 5 wt% nanoparticles doping performs well in suppressing space charge injection. The electric field of the 5 wt% nanoparticles doped EVA distributes more uniformly under the high electric stress than that of others. During the depolarization procedure, the total remnants charges of 10 wt% doped samples are the least in the final. The above results are well explained by the DC conduction, apparent mobility and trap distribution characteristics. The micro-sized ZnO particles may break the chains and produce new defects, which will act as local deep traps.

Effect of electron beam irradiation and microencapsulation on the flame retardancy of ethylene-vinyl acetate copolymer materials during hot water ageing test

Microencapsulated ammonium polyphosphate (MCAPP) in combination with polyester polyurethane (TPU) was used to flame retardant ethylene-vinyl acetate copolymer (EVA). The EVA composites with different irradiation doses were immersed in hot water (80°C) to accelerate ageing process. The microencapsulation and irradiation dose ensured positive impacts on the properties of the EVA composites in terms of better dimensional stability and flame retardant performance. The microencapsulation of APP could lower its solubility in water and the higher irradiation dose led to the more MCAPP immobilized in three dimensional crosslinked structure of the EVA matrix which could jointly enhance the flame retardant and electrical insulation properties of the EVA composites. So, the EVA composites with 180kGy irradiation dose exhibited better dimensional stability than the EVA composites with 120kGy due to the higher crosslinking degree. Moreover, the higher irradiation dose lead to the more MCAPP immobilizated in crosslinked three-dimensional structure of EVA, enhancing the flame retardancy and electrical insulation properties of the EVA composites. After ageing test in hot water at 80°C for 2 weeks, the EVA/TPU/MCAPP composite with 180kGy could still maintain the UL-94 V-0 rating and the limiting oxygen index (LOI) value was as high as 30%. This investigation indicated the flame retardant EVA cable containing MCAPP could achieve stable properties and lower electrical fire hazard risk during long-term hot water ageing test.

Fire retardancy of ethylene-vinyl acetate composites – Evaluation of synergistic effects between ATH and diatomite fillers

In the present work, diatomite was used as co-filler in aluminium hydroxide/ethylene-vinyl acetate composites (ATH/EVA). This silica-based marine sediment acts as a synergistic agent with ATH, to increase the flame retardant properties of EVA composites. When diatomite was used with ATH the formation of an expanded layer during cone calorimetry tests was observed. This layer presents a complex structure which better insulates the sample and reduces the heat release rate (HRR). Rheological measurements, such as complex viscosity obtained with an ARES apparatus, suggest an influence of the viscosity of the sample melt. We assume that the viscosity of the EVA composites is influenced by the porosity of the diatomite. Better residue cohesion was also obtained in presence of diatomite.

Preparation and Application of Colemanite Matrix Complex Flame Retardant

In this paper, stearic acid, titanate coupling agent (NDZ-311) and silane coupling agent (KH-570) were selected as modifiers to modify colemanite powder and the resulted products were characterized by XRD and FT-IR. The results show that the surfaces of colemanite particles were effectively modified by stearic acid and coupling agents. The modified colemanite /EVA composites were then prepared and the effect of coupling agent addition on the mechanical properties and flame retardancy of EVA composites was investigated. The EVA composite doped with 40% of modified colemanite (coupling agent accounting for 1% of colemanite mass) exhibits a tensile strength of 9.80MPa, a breaking elongation of 696.5% and a limit oxygen index of 29.6%. The complex flame retardant was obtained by means of grafting amine polyphosphate onto the surface of colemanite using polyphosphoric acid (PPA) and laurylamine as raw materials. The obtained product was analyzed by XRD and FT-IR. The EVA composite doped with 40% of the complex flame retardant has a tensile strength of 8.57MPa, a breaking elongation of 671.3% and a limit oxygen index of 32.6%.

Synergistic effects of 4A zeolite on the flame‐retardant properties and thermal stability of an efficient halogen‐free flame‐retardant EVA composite

The synergistic effects of 4A zeolite (4A) on the thermal degradation, flame retardancy, and char formation of an efficient halogen‐free flame‐retardant ethylene‐vinyl acetate copolymer composite (EVA/IFR) were investigated by limited oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test (CCT), digital photography, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), laser Raman spectroscopy (LRS) and thermogravimetric analytical (TGA) methods. It was found that a small amount of 4A clearly improved the LOI value of the EVA/IFR composite and reinforced the fire retardant performance with a great reduction in the combustion parameters of the EVA/IFR system from the CCT test. The entire composites passed the UL‐94 V‐0 rating test. The TGA and integral procedure decomposition temperature (IDPT) results showed that 4A enhanced the thermal stability of the EVA/IFR system and increased the char residue content effectively. The morphological structures observed by digital and SEM imaging revealed that 4A could promote EVA/IFR to form a more continuous and compact intumescent char layer. The LRS and EDS results demonstrated that by introduction of 4A into the EVA/IFR system, a more graphite structure was formed with increase phosphorus content in the char residue. POLYM. ENG. SCI., 56:380–387, 2016. © 2016 Society of Plastics Engineers

Improved ceramifiable properties of EVA composites with whitened and capsulized red phosphorus (WCRP)

Phase separation between SGFs and phosphates promotes formation of cristobalite at high temperature, which leads to improvements in ceramifiable properties.

Toughened elastomer/polyhedral oligomeric silsesquioxane (POSS)‐intercalated rectorite nanocomposites: Preparation, microstructure, and mechanical properties

Improving the properties and behaviors of polymeric materials is significantly important both in industry and academic area. In this contribution, natural rubber (NR) and ethylene‐vinyl acetate copolymer (EVA) based nanocomposites were prepared using polyhedral oligomeric silsesquioxane (POSS) intercalated rectorite (POSS‐REC) as the nanofiller. The microstructure and POSS‐REC dispersion in the composites were investigated via XRD and TEM. The results indicated that intercalated‐exfoliated POSS‐REC/NR composites and exfoliated POSS‐REC/EVA composites were obtained successfully. Thermal properties data indicated that the presence of POSS‐REC improved thermostability of the composites. SEM observations of fracture surfaces showed that POSS‐REC in the composites could terminate primary crazings and induce new smaller crazings. Mechanical tests showed that tensile strength and elongation at break of the composites increased notably with the content of POSS‐REC. On the basis of experimental data, a possible dispersion model was proposed. The obtained nanocomposites may have excellent prospects in the fields demanding high performances. POLYM. COMPOS., 38:E443–E450, 2017. © 2015 Society of Plastics Engineers

Nanoengineering of brucite@SiO2 for enhanced mechanical properties and flame retardant behaviors

An efficient halogen-free composite flame retardant (CFR) consisting of a brucite core and a thin SiO2 shell was synthesized via a facile nanoengineering route. The as-synthesized CFR was employed as a filler material to improve the mechanical performance and flame retardancy of EVA composite. In comparison with that of EVA/brucite and EVA/PM, the mechanical properties of EVA/CFR, especially the tensile strength (TS), presented a remarkable increase reaching at least a 25% increment. Meanwhile, with the same 50 wt% of fillers, the EVA/CFR formulation could achieve a limiting oxygen index (LOI) value of 34 (13% higher than that of EVA/PM blends) and UL-94 V-0 rating. Moreover, the heat release rate (HRR), peak heat release rate (PHRR), total heat released (THR), smoke production rate (SPR) and mass loss rate (MLR) were considerably reduced. Based on the results, the enhanced mechanism for the mechanical properties and flame resistance of CFR particles has been also proposed, which could be mainly ascribed to structural synergy between brucite core and SiO2 shell. Therefore, the nanoengineering of brucite@SiO2 might pave the way for the future development of a facile large-scale approach to brucite-based flame retardant materials.

The Effect of a Novel Intumescent Flame Retardant-Functionalized Montmorillonite on the Thermal Stability and Flammability of Eva

A novel intumescent flame retardant-functionalized montmorillonite (PAB-MMT) was prepared by modification of sodium montmorillonite (Na-MMT) with an intumescent flame retardant (PAB) containing phosphorus-nitrogen structure. The results of X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analysis indicated that PAB had intercalated into Na-MMT. The applications of this fact for improving the thermal stability and flammability of poly(ethylene-co-vinyl acetate) were investigated by thermogravimetric analysis (TGA), and microscale combustion calorimetry (MCC). Scanning electron microscopy (SEM) was carried out to learn the morphology of the char residue. The results showed that the addition of PAB-MMT into EVA could improve the flame retardancy of the EVA matrix. The peak heat release rate (PHRR) and total heat release (THR) were significantly reduced in comparison with those of other EVA composites. The TGA data showed higher char residue than other composites, which was the reason for the improved flame retardancy.

Influence of the pentaerythritol phosphate melamine salt content on the combustion and thermal decomposition process of intumescent flame‐retardant ethylene–vinyl acetate copolymer composites

ABSTRACTPentaerythritol phosphate melamine salt (PPMS) as a single‐molecule intumescent fire retardant was synthesized and characterized. The influence of the PPMS content on the combustion and thermal decomposition processes of intumescent‐flame‐retardant (IFR) ethylene–vinyl acetate copolymer (EVA) composites was studied by limiting oxygen index (LOI) measurement, UL 94 rating testing, cone calorimetry, thermogravimetric analysis, and scanning electron microscopy. The LOI and UL 94 rating results illustrate that PPMS used in EVA improved the flame retardancy of the EVA composites. The cone calorimetry test results show that the addition of PPMS significantly decreased the heat‐release rate, total heat release, and smoke‐production rate and enhanced the residual char fire performance of the EVA composites. The IFR–EVA3 composite showed the lowest heat‐release and smoke‐production rates and the highest char residue; this means that the IFR–EVA3 composite had the best flame retardancy. The thermogravimetry results show that the IFR–EVA composites had more residual char than pure EVA; the char residue yield increased with increasing PPMS content. The analysis results for the char residue structures also illustrated that the addition of PPMS into the EVA resin helped to enhance the fire properties of the char layer and improve the flame retardancy of the EVA composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42148.

Cyclodextrin microencapsulated ammonium polyphosphate: Preparation and its performance on the thermal, flame retardancy and mechanical properties of ethylene vinyl acetate copolymer

Cyclodextrin microencapsulated ammonium polyphosphate (MCAPP) was prepared by the reaction between cyclodextrin (CD) and toluene-2,4-diisocyanate (TDI) with the goal of improving the water durability of APP and preparing a novel functional flame retardants. The Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) results indicated MCAPP were successfully prepared, and the water contact angle (WCA) results indicated that cyclodextrin resulted in the transformation of hydrophilic to hydrophobic of the flame retardant surface. The MCAPP was then incorporated into the ethylene vinyl acetate copolymer (EVA) system and the effects of the MCAPP on the mechanical, combustion, thermal, interfacial adhesion and flame-retardant properties of EVA cable were investigated and compared by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), limiting oxygen index (LOI), mechanical test, cone calorimeter and UL-94 test. The characterization for the various properties of EVA composites demonstrated that cyclodextrin microencapsulation technology could enhance the interfacial adhesion, resulting in the improved mechanical, thermal stability, combustion properties and flame-retardant properties compared with those of EVA/APP/CD system. Furthermore, the water resistance experiments results demonstrate that EVA/MCAPP composites have good water durability due to the hydrophobic property of MCAPP. Above all, the microencapsulation of APP with cyclodextrin developed in this study may be a promising formulation for combining the acid source, the carbonization agent and the blowing agent in one flame retardant, and the MCAPP can solve the water resistance and the compatibility problem of the flame retardant during the industrial application.

Synergistic effect of carbon nanotubes in combination with magnesium hydroxide on the flame retardant poly(ethylene-co-vinyl acetate)

Abstract To investigate the synergistic effect of carbon nanotubes (CNTs) in combination with magnesium hydroxide (MH) on the flame retardant poly(ethylene-co-vinyl acetate) (EVA), a series of EVA-based composites filled with CNTs, MH, a mixture of MH and CNTs, and MH-modified CNTs (MH-CNTs) were prepared. Characterizations of the fillers and the composites were performed by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and cone calorimetry. The results indicated that the presence of CNTs affected the size of the attaching MH, which was decreased to around 20 nm. MH also had an enlarged special surface area in the MH-CNTs. A synergism was found in the MH-CNTs on the thermal retardant EVA composites due to the interaction between MH and CNTs.

Research on Properties of CB/EVA Semiconductive Shielding Composites

In order to select suitable carbon black (CB) for manufacturing semiconductive shielding materials of XLPE insulated high voltage cable, the composites were prepared with the melt blending method by adding CB with different properties into ethylene/vinyl acetate copolymer (EVA). The volume resistivity, mechanical property and rheological property of the composites were measured. The effects of the properties and content of CB on the various properties of the composites were investigated and their mechanism was analyzed. The research results show that both structure and specific surface area of CB have great effects on the volume resistivity and rheological property of the composites. Because high structure CB usually has high specific surface area, the high structure CB/EVA composites have low percolation threshold and low rheological property. The EVA composites containing low structure CB with larger specific surface area exhibit low conductivity and high melt viscosity. When the mass fraction of CB with low structure and small specific surface area reaches 35%, the volume resistivity of the composites is approximately 100 Ω·cm and the rheological property of the composites is obviously superior to the composites filled with high structure CB. The CB with small specific surface area and low structure as conductive filler is beneficial for good conductivity and extrusion processability of the semiconductive shielding materials.

Flame retardant ethylene‐vinyl acetate composites based on layered double hydroxides with zinc hydroxystannate

Mg‐Al‐Fe ternary layered double hydroxides (LDH) were synthesized based on red mud (RM) by calcination‐rehydration method, and characterized using X‐ray diffraction (XRD). And, the LDH coated with ZnSn(OH)6 (ZHS) was studied by XRD, scanning electron microscopy (SEM), transmission electron microscopy, and energy dispersive spectroscopy (EDS). The flame retardant and thermal properties of EVA composites based on RM, LDH and LDH coated with ZHS were studied using cone calorimeter test (CCT) and thermogravimetric analysis (TGA). The CCT data indicates that heat release rates (HRR) of EVA with LDH coated with ZHS decreases in comparison with that of EVA, EVA/RM and EVA/LDH composites. The TGA data show that LDH coated with ZHS can apparently increase the thermal stability and the charred residues after burning. POLYM. ENG. SCI., 54:2918–2924, 2014. © 2014 Society of Plastics Engineers

Mutual protection against UV aging of EVA composites using highly active optical conversion additives

The mutual ultraviolet (UV) degradation protection and optical conversion mechanism of ethylene-vinyl acetate copolymer (EVA) rare earth organic complex (REOC) composite were investigated.

Comparative study on the effect of electron beam irradiation on the physical properties of ethylene-vinyl acetate copolymer composites

Ethylene-vinyl acetate copolymer (EVA) flame retarded by a combination of cellulose acetate butyrate (CAB) microencapsulated ammonium polyphosphate (MCAPP) and polyamide-6 (PA-6) have been crosslinked by high energy electron beam irradiation. The effect of high energy electron beam irradiation on the crosslinking degree, mechanical, electrical and thermal properties of EVA/MCAPP/PA-6 cable material was studied by gel content, heat extention test, mechanical test, dynamic mechanical analysis, high-insulation resistance meter and thermogravimetric analysis. The gel content and heat extention test results showed that the EVA/MCAPP/PA-6 composites can be easily crosslinked by electron beam irradiation. The tensile strength of EVA composites was drastically increased from 16.2 to maximum 26.2MPa as the electron beam irradiation dose increases from 0 to 160kGy. The volatilized products of EVA/MCAPP/PA-6 composites were analyzed and compared by thermogravimetric analysis/infrared spectrometry (TG-FTIR).

Fire retardancy of ethylene vinyl acetate/ultrafine kaolinite composites

The flame retardant effect of ultrafine kaolinite in Ethylene Vinyl Acetate copolymer (EVA) was studied and compared to that conferred by aluminum trihydrate (ATH). The thermal degradation and flammability of EVA composites were evaluated up to 60 wt% filler loading. Thermogravimetric (TG) and cone calorimeter analyses showed a higher decomposition temperature range and an improved FR performance for EVA/kaolinite composites in comparison to EVA/ATH composites. For a loading of 35 wt%, the peak of heat release rate (pHRR) of EVA/kaolinite was reduced by 55% compared to EVA/ATH. Moreover, we observed that kaolinite leads to a significant intumescent behavior during cone calorimeter tests. Finally, the rheology in the molten state of the different samples was studied and viscosity seems to play an important role on the fire retardancy of EVA/kaolinite composites.

Preparation of microcapsulated ammonium polyphosphate, pentaerythritol with glycidyl methacrylate, butyl methacrylate and their synergistic flame‐ retardancy for ethylene vinyl acetate copolymer

A new series of microcapsules containing pentaerythritol (PER) and ammonium polyphosphate (APP) with glycidyl methacrylate and butyl methacrylate as shell materials were synthesized by in situ polymerization. The structure and performance of the microencapsulated APP and microencapsulated PER were characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle. The flame retarded ethylene‐vinyl acetate copolymer (EVA) composites were studied by limiting oxygen index, UL‐94 test, and cone calorimeter. It was found that the microencapsulation of flame retardants (FRs) with the glycidyl methacrylate and butyl methacrylate lead to a decrease in the particle's water solubility and an improvement of the hydrophobicity. Results also demonstrated that the FR properties of EVA/microencapsulated APP/microencapsulated PER composites were better than those of the EVA/APP/PER composites at the same loading of FRs. The thermogravimetric analysis results reflected that the microencapsulated EVA composites had better thermal stability because of the forming of stable char during the combustion. Copyright © 2013 John Wiley & Sons, Ltd.

Synergistic flame retardant effect of metal hydroxide and nanoclay in EVA composites

This study focused on the flame retardancy of ethylene-vinyl acetate copolymer (EVA) in combination with metal hydroxide and nanoclay. Fire tests, such as limiting oxygen index (LOI), flammability (UL-94), cone calorimeter, and smoke density chamber were employed to evaluate the effect of composition variation for the metal hydroxide and the nanoclay in EVA composites. The experimental results showed that when the nanoclay of 1 or 2 weight per cent was substituted for the aluminum hydroxide or magnesium hydroxide in EVA blends, the LOI value was significantly improved while the V-0 rating was maintained. The data obtained from the cone calorimeter test indicated that the peak heat release rate (pk-HRR) is reduced by about 28%–47%. The smoke density data (maximal smoke density, Dm) showed a reduction by about 16%–25%. The thermogravimetric analysis (TGA) data also showed that the nanoclay increased the thermal stability and char residue of the EVA samples. Hence, it is suggested that the metal oxide layer on the burning surface is reinforced by the formation of silicate layer, which is both structured and compacted and acts as the insulation, and the newly formed layer responds to the synergistic effect of flame retardancy as well as smoke suppression observed in the EVA blends.