EVA Composites Research Articles

Morphology and Mechanical Properties of LDPE, EVA and Fly Ash Composites

The fly ash from Pha Lai power plant was modified by vinyltrimetoxysilan (VTMS). The polymer composites based on low-density polyethylene (LDPE), ethylene vinyl acetate copolymer (EVA) and fly ash (FA) without and with vinyltrimetoxysilan (VTMS) modification were prepared by melt mixing in a Haake Rheomixer. The tensile strength and elongation at break of the LDPE/EVA/VFA composites were also higher than those of the LDPE/EVA/FA composites. The FESEM images proved that FA-VTMS particles disperse more regularly in the polymer matrix in comparison with FA without VTMS modification. In addition, the surface modification of the FA reduced the size of agglomeration of FA particles.

Enzymatic polymerization derived engineered polysaccharides as reinforcing fillers of ethylene vinyl acetate composites

A novel monomer based, controlled enzymatic polymerization was employed to produce an engineered alpha-1,3 glucan polysaccharide. The structure and material properties of the engineered polysaccharide were characterized using various techniques. The use of such engineered polysaccharide as a reinforcing filler of polymers was evaluated using model polymers. For this, the alpha-1,3 glucan was incorporated into ethylene vinyl acetate co-polymer (EVA) matrices with vinyl acetate content of 32% and 40% via a melt processing fabrication process. Various mechanical and rheological properties of the fabricated composites were evaluated. The effect of vinyl acetate content of the EVA resin on the interaction with alpha-1,3 glucan that result in various performances attributes was also investigated and reported. The incorporation of alpha-1,3 glucan in these EVA composites resulted in the improvement of key composite properties, such as toughness, modulus, wear resistance, and hardness showing the reinforcing potential of these engineered polysaccharides.

Preparation of graphene intercalated magnesium silicate for enhancing the thermal stability and thermal conductivity of ethylene-vinyl acetate copolymer

Ethylene-vinyl acetate copolymer (EVA) is a kind of thermoplastic resin with wide range of application. However, the enhancement of thermal resistance properties of EVA is still challenging. Herein, an effective approach is reported for the preparation of graphene nanosheets intercalated magnesium silicate (MS@GN) hybrids, which were employed as nano-additives for improving the thermal resistance properties and thermal conductivity of EVA. By controlling the content of MS@GN, 0.2 wt% of MS@GN in EVA composites showed enhanced thermal stability in terms of elevated decomposition temperature and enlarged storage modulus and thermal conductivity when compared with neat EVA. Especially, MS@GN has versatile advantages, such as thermally conductive network from the orderly intercalated graphene, high contacted area from the highly opened magnesium silicate, and desired dispersibility of MS@GN in the polymer matrices. Therefore, the MS@GN showed great potential for boosting the high temperature adaptation of EVA.

Effect of natural basalt fiber for EVA composites with nickel alginate‐brucite based flame retardant on improving fire safety and mechanical properties

The natural basalt fiber (BF) was incorporated into EVA composites with environmental‐friendly nickel alginate‐brucite based flame retardant (NiFR), to further improve the flame‐retardant effect and mechanical properties. The flame retardancy of EVA composites were characterized by LOI, UL 94, and cone test. With 55 wt% loading, 3BF/52NiFR had the highest LOI value of 31.9 vol.% in all fiber reinforced composites and pass UL 94V‐0 ratting. And comparing to 55B composite with untreated brucite, 3BF/52NiFR decreased peak of heat release rate by 47.8%, total heat release by 21.9%, and total smoke production by 35.5% and kept more residue 54.0% during cone test. Moreover, 3BF/52NiFR also enhanced the mechanical properties of composites by better compatibility with EVA matrix. BF/NiFR exert synergistic flame‐retardant effect major in promoting charring effect in condensed phase during combustion. The fire‐resisted and rigid BF into the char layer reinforced the intensity of protective barrier which prolonged the residence time of pyrolysis carbonaceous groups degraded from EVA matrix, resulting in less heat and smoke release.

Simultaneously improving flame retardancy, water and acid resistance of ethylene vinyl acetate copolymer by introducing magnesium hydroxide/red phosphorus co-microcapsule and carbon nanotube

In this work, a co-microcapsule of magnesium hydroxide (MH) and red phosphorus (RP) (denoted as M[MH&RP]) was synthesized using 4, 4′-diphenylmethane diisocyanate and melamine via one-step in-situ surface polymerization, which was subsequently introduced into ethylene vinyl acetate copolymer (EVA) as a flame retardant. The results indicate that the core-shell structured co-microcapsule displays increased thermal and thermo-oxidative stability as well as better dispersion in EVA. Flame retardancy of the EVA/M[MH&RP] composite improves significantly in comparison with the EVA/MH/RP composite due to formation of continuous and compact char layer on the surface of the composite. Moreover, this flame-retardant composite exhibits excellent water and acid resistance. The addition of a small amount of multi-walled carbon nanotube (MWCNT) further increases flame retardancy of the EVA/M[MH&RP] composite considerably and the flame-retardant EVA/M[MH&RP]/MWCNT composite has good mechanical flexibility and electrical insulation. This work has provided a simple method to prepare multi-functional flame-retardant EVA composite.

Preparation and flame retardancy of nitrogen and phosphorus containing flame retardant of N@PGS-AlHP for EVA composite

A novel organic@inorganic-inorganic hybrid flame retardant named N@PGS-AlHP (where PGS = palygorskite, AlHP = aluminum hypophosphite) which could increase simultaneously the interfacial interaction and the flame retardancy of EVA was prepared. The EVA was mixed with N@PGS-AlHP and expandable graphite (EG) to enhance its flame retardancy. FTIR, XRD, SEM and TGA confirmed that AlHP had been precipitated on the palygorskite and PGS-AlHP was grafted by O-carboxyl benzoyl octadecylamine which was prepared by the reaction of octadecylamine and phthalic anhydride successfully. The results of flame retardancy test showed that the prepared composite of EVA/N@PGS-AlHP/EG obtained the highest LOI value of 40.1% with additives of 30 wt% of flame retardants of N@PGS-AlHP/EG. The EVA/N@PGS-AlHP/EG composite obtained the highest residue mass (61.4 wt%) after combustion, which was due to the introduction of the AlHP flame retardant and N element. The char residue could contribute to enhance the flame retardancy of EVA composite.

JOINT TREATMENT OF BENTONITES WITH INORGANIC POLYELECTROLYTES AND CATIONIC SURFACTANTS IN ORDER TO PROMOTE ORGANOCLAY EXFOLIATION

A new approach to production of organomodified bentonites is offered. Bentonites are consecutively treated with inorganic polyelectrolyte (sodium silicate solution) and quaternary ammonium salts, as a result exfoliated organoclays are obtained. An ejector set up has been used for treatment of natural bentonites. Samples of activated bentonites treated in the ejector set up with sodium silicate solution (up to 21 g of sodium silicate per 100 g of bentonite) were prepared. Structure of the obtained bentonite and organoclay samples was established by X-ray diffraction analysis. It has been shown that treatment of the activated bentonite with sodium silicate does not influence the structure of the non-modified bentonite particles, but facilitates exfoliation of clay after organomodification. Polymer composites based on EVA containing 5% wt. of bentonites were prepared by extrusion mixing. In case of non-modified bentonites microcomposites are formed. In case of organomodified bentonites, not treated with sodium silicate, intercalated nanocomposites are formed. Treatment of bentonite with sodium silicate solution and subsequent organomodification ensures the production of exfoliated nanocomposite. Mechanical properties of obtained polymer composites were determined. Incorporation of 5% wt. clays or organoclays into the polymer material leads to increase in Young modulus (up to 50%), tensile strength (up to 20%); elongation at break decreases by 10% or less. In order to ensure the more significant reinforcing effect in EVA composites optimization of the organomodified bentonite composition (selection of surfactant and its content in the organoclay) has to be carried out with account for the polymer properties.

Synergistic Effects of Nano-zinc Oxide on Improving the Flame Retardancy of EVA Composites with an Efficient Triazine-Based Charring Agent

The synergistic effect of nano-zinc oxide (nano-ZnO) on the flame retardancy and thermal stability of intumescent flame retardant ethylene–vinyl acetate (EVA/IFR) consisting of novel hyperbranched triazine-based charring agent (HTCFA) and APP was evaluated by limiting oxygen index (LOI), UL-94 measurement, cone calorimeter test (CCT) and thermogravimetric analysis (TGA), and the residue analysis was also carried out through scanning electron microscopy (SEM), fourier transform infrared (FTIR), laser raman spectroscopy (LRS), and X-ray photoelectron spectroscopy (XPS). The results showed that introducing a certain amount of nano-ZnO could obviously enhance LOI value and UL-94 rating, and effectively restrain the combustion performance of EVA/IFR composites, leading to the decrease of heat and smoke release. The addition of 0.5 wt% nano-ZnO into EVA/IFR composite obtained the highest catalytic effectivity (CAT-EFF). TGA results uncovered a distinct synergistic carbonization effect existed between nano-ZnO and IFR, and nano-ZnO could obviously improve the high-temperature thermal stability and promote the char formation of IFR and EVA/IFR. Analysis of final char residues proved that the incorporation of appropriate amount of nano-ZnO contributed to remaining more P and forming more high-quality graphitization char layers with richer P–O–C and P–N cross-linking structures in condensed phase owing to the catalytic carbonization effect of nano-ZnO on IFR system, which played a critical role in remarkable improvement of flame retardancy and smoke suppression properties of composites.

Three-dimensional cross-linking structures in ceramifiable EVA composites for improving self-supporting property and ceramifiable properties at high temperature

Ceramifiable EVA composite with three dimensional cross-linking structures was prepared by bis (tert-butylperoxy) diisopropyl benzene (BIPB) as cross-linking agent, and silicate glass frits (SGF) and ammonium polyphosphate (APP) were utilized as additives. By using FTIR, DSC and measurement of gel content, the formation of cross-linking structures was studied. Rheometer and TGA were used to characterize the rheological properties and thermal stability of the composite. The effect of cross-linking structures on the self-supporting property and the ceramifiable properties of the composite was investigated. The apparent porosity of the ceramic residues was examined. XRD and SEM were used for the phase composition and morphology of the ceramic residues analysis respectively. Results suggested that the cross-linking reaction occurred in the EVA matrix and the SGF and APP have no effect on the cross-linking reaction. The formation of cross-linking structures improved the rheological properties and thermal stability of the composite, resulting in the improvement on self-supporting and ceramifiable properties. Further, we demonstrated that cross-linking structures as “skeletal structures” could support its own weight before inorganic crystalline phases appeared, which provided a necessary prerequisite for its excellent self-supporting property in the range of 0–1000 °C. In addition, it has been proved that the apparent porosity was decreased and the compactness of ceramic residues was enhanced after the cross-linking structures were formed.

Simultaneously Improved Flame Retardance and Ceramifiable Properties of Polymer-Based Composites via the Formed Crystalline Phase at High Temperature.

Ceramifiable polyolefin materials have an excellent application prospect in high-temperature-resistant wires and cables because of their excellent fire safety performance via a ceramization process under fire conditions. During the ceramization process, the control of the crystalline phase plays a vital role in determining the final fire resistance and ceramifiable properties. In this work, ammonium polyphosphate/zinc borate (APP/ZB) was developed to achieve the highly efficient flame retardance and ceramization of the ethylene-vinyl acetate/mica powder/organo-modified montmorillonite (EVA/MP/OMMT) composite. In the combustion test, the EVA/MP/OMMT/APP/ZB system displayed obvious flame retardance feature, showing much lower total heat release and total smoke production than neat EVA. After treating at high temperatures, rigid ceramic products were formed for EVA/MP/OMMT/APP/ZB. The ceramic that was formed at 900 °C had a flexural strength of 10.3 MPa for EVA/MP/OMMT/APP/ZB containing 23 wt % of APP/ZB (9.9:13.1), increased by 2475.0, 635.7, and 586.7% compared to the corresponding values of EVA/MP/OMMT, EVA/MP/OMMT/ZB, and EVA/MP/OMMT/APP. For the latter two systems, the content of ZB or APP was 23 wt %. APP/ZB showed a remarkable fluxing effect on the ceramization of the MP-based EVA composite. The fluxing mechanism of APP/ZB was revealed by different measurements. Both APP and ZB led to the formation of a glass melt containing α-Zn3(PO4)2 and orthophosphate by increasing the temperature. Successively, the melt crystalline structure cohered the OMMT and MP together, accompanied by the gradual disappearance of the mica phase and the generation of eutectic phenomenon. Finally, a ceramic with high flexural strength was formed, leading to the improved flame retardance and ceramifiable properties of EVA-based composites.

Synergistic flame-retardant effect between lignin and magnesium hydroxide in poly(ethylene-co-vinyl acetate)

AbstractIn this study, we evaluated the interest of combining magnesium hydroxide (MDH) and lignin for developing complementary flame retardant actions in poly(ethylene-co-vinyl acetate) (EVA). Lignin was selected owing to its char forming ability thatwas supposed to reinforce the endothermic effect provided by MDH. The effect of lignin chemical modification by ammonium phosphate functions also evaluated as a way for enhancing its charring effect. Fire properties and thermal behavior of EVA composites were characterized using cone calorimeter, Pyrolysis Combustion Flow Calorimeter (PCFC) and thermogravimetric analysis (TGA). The effect of the incorporation of lignin alone on EVAcomposite thermal and fire behavior first evaluated. Results evidenced that the incorporation of lignin, whatever its nature, induced important reduction of composite thermal stability during TGA analysis as well as significant reduction of the time to ignition (TTI) in cone calorimeter test. However, a significant reduction of peak of heat release rate (pHRR), higher than that obtained with MDH was observed. The combination of lignin and MDH was led to further reduction of pHRR. Furthermore, it was concluded that the chemical modification of lignin is not required prior obtaining improved flame-retardant properties.

Synergistic effect of polydopamine-polyethylenimine copolymer coating on graphene oxide for EVA nanocomposites and high-performance triboelectric nanogenerators.

While the demand for lightweight high-strength nanocomposites is immense, their progress has been severely limited due to inferior filler dispersion and filler–matrix interface adhesion. This article reports a novel modification of graphene oxide (GO) encapsulated by the copolymer of polydopamine (PD) and polyethylenimine (PEI) via a Michael addition reaction, aiming to create robust ethylene vinyl acetate copolymer (EVA) nanocomposites even at very low amounts of filler loading by overcoming the above hindrances. It has been found that the addition of only 1.2 wt% modified GO (i.e., PD–PEI–rGO) increased the tensile strength, Young's modulus and storage modulus of EVA composites by 80%, 50% and 24%, respectively. These increments surpass many recent claims on relevant composites. Excellent molecular level dispersion was also observed from the fracture surface SEM images. Being amine-rich with high electron-donating capability and mechanically robust, the nanocomposite served as an outstanding tribopositive material, thereby generating 7.49 V and 4.06 μA output voltage and current, respectively, when employed in a triboelectric nanogenerator (TENG). The high electrical outputs led the device to light up 43 blue LEDs instantaneously upon hand pressing, demonstrating that the nanocomposite is indeed a promising candidate for harvesting green energy. Moreover, the nanogenerator displayed outstanding cyclic performance stability (even after 8000 cycles) and environmental durability.

Effect of carbonized wood fiber loading on properties of ethylene vinyl acetate copolymers

In this research, wood fiber waste type B was carbonized in stand steel tabulate and the whole system was kept in the furnace to undergo combustion process for 3 h at a temperature of 700 °C. The new promising filler is carbonized wood fiber (CWF). It was characterized using SEM–EDX to measure elemental composition. Based on the carbon content in CWF filler, it was proceeded in the melt-blending technique within EVA (semi-crystalline) using a Brabender plasticorder. The aim of this study was to investigate the effect of CWF loading on physical, mechanical, thermal and electrical performances of EVA composites. The statistical analysis indicates that there was no significant difference between theoretical and measured density, proven by p value of 0.2564. The void content increased dramatically up to 2% and remains a valid value for composite production. The mechanical properties dropped gradually with increasing CWF filler within EVA composites and similarly by mass swell percentages. The enhancement of conductivity in these composites was due to the attraction of CWF to EVA, promoting formation of conductive networks. The percolation threshold of CWF in the EVA matrix was determined at 10 phr of CWF loading. Thermal stability of composites increased with the increasing of CWF filler. Lastly, crystal orientation ratio and d-spacing reduced with the addition of CWF filler in EVA/CWF composites.

Study of nanocarbon black as synergist on improving flame retardancy of ethylene-vinyl acetate/brucite composites

Nanocarbon black (CB) was introduced into ethylene-vinyl acetate/brucite (EM) composites to investigate the synergistic effect of CB and metal hydroxide on improving the flame retardancy of EVA. Flammability properties of the as-prepared EVA composites were investigated by thermogravimetric analysis, limiting oxygen index (LOI), UL-94 test and cone calorimetry test. The results indicated that the optimum mass ratio of CB/brucite was 1/54, at which the EVA composites displayed dramatic improvement on thermal stability and flame retardancy. The LOI value was as high as 35.3%, the UL-94 passed the V-0 rating, and the peak heat release rate reduced 79% in comparison with pure EVA. Based on the morphology and structure analysis for residue chars, the flame-retardant mechanism was attributed mainly to the positive synergistic effect of CB and brucite on promoting the formation of better carbon protective layer during combustion.

Improving fire retardancy of ceramifiable polyolefin system via a hybrid of zinc borate@melamine cyanurate

To achieve a high flame retardancy of ethylene-vinyl acetate copolymer (EVA)-based ceramifiable composites, we prepared a hybrid of zinc borate@melamine cyanurate (ZB@MCA) by depositing zinc borate (ZB) at the surface of melamine cyanurate (MCA) on the basis of their hydrogen bonding, and incorporated the ZB@MCA into the EVA/glass powder/mica powder/organo-modified montmorillonite (EVA/GP/MP/OMMT) system to form a novel flame-retardant and ceramifiable EVA composite (EVA/GP/MP/OMMT/ZB@MCA). For EVA/GP/MP/OMMT/ZB@MCA composite with a weight ratio of 35/23/17/5/20, its ceramic formed at 800 °C has the flexural strength of 13.9 MPa, keeping at a high level. The burning tests confirmed that the limiting oxygen index (LOI) value of the composite reached 27.5%, and the UL-94 V-0 rating was achieved. The peak of heat release rate (PHRR) and the peak of smoke production rate (SPR) decreased remarkably compared with the corresponding value of neat EVA in cone calorimeter test. Thermogravimeter-Fourier transform infrared spectroscopy (TG-FTIR) and X-ray photoelectron spectroscopy (XPS) spectra were used to illustrate the flame-retardant mechanism of ZB@MCA in ceramifiable EVA system, and the result illustrated that the gas-phase flame-retardant mechanism was dominant, meanwhile, the ZB facilitated the formation of ceramic layer as a physical barrier in condensed phase, further leading to the enhancement of flame retardancy of EVA composite.

Flame retardancy and thermal behavior of intumescent flame-retardant EVA composites with an efficient triazine-based charring agent

Intumescent flame retardant (IFR) EVA composites were prepared based on a hyperbranched triazine charring-foaming agent (HTCFA) and ammonium polyphosphate (APP). The synergistic effect of HTCFA and APP on the flame retardancy and thermal behavior of the composites were investigated through flammability tests, cone calorimeter measurements, thermogravimetric analysis (TGA) including evolved gas analysis (TG-IR) and residue analysis (Fourier transform infrared (FTIR), laser Raman spectroscopy (LRS), x-ray Photoelectron Spectroscopy (XPS) and scanning electron microscopy (SEM)). The flammability test results showed HTCFA/APP (1/3) system presented the best synergistic effect in flame-retardant EVA composites with the highest LOI value and UL-94 V-0 rating. As for cone calorimeter results, IFR changed the combustion behavior of EVA and resulted in remarkable decrease of flammability and smoke product. TGA results showed the synergistic effect between APP and HTCFA could strengthen the char-forming ability of composites. TG-IR results indicated the melt viscosities and gas release with increasing temperature were well-correlated for EVA/IFR composite. The residue analysis results from SEM, LRS, FT-IR and XPS revealed IFR promoted forming more compact graphitic char layer, connected by rich P–O–C and P–N structures.

Preparation of urea formaldehyde microsphere and its effect on flame retardant ethylene vinyl acetate composites

Urea formaldehyde microsphere (UFM) was prepared and used with organic montmorillonite (OMMT) to modify the flame retardant efficiency of ethylene vinyl acetate copolymer (EVA)/intumescent flame retardant (IFR) composites. The results show that single IFR may modify the flame retardancy of EVA, but its efficiency is not good enough. The EVA composite containing 21 wt% IFR is just classified the UL_94 V2 and has a limiting oxygen index (LOI) 24.7 vol%. Combining UFM with IFR does not improve the flame retardancy of EVA/IFR composites, and blending OMMT with IFR only improves its LOI. Adding 2 wt% UFM, 2 wt% OMMT, and 17 wt% IFR into EVA, it obtains the UL_94 V0 without melt dripping and a LOI 29.0 vol%. Also, the peak heat release rate and total heat release decrease a lot. Good synergistic effects among IFR, UFM, and OMMT improve the char residues and modify the char micromorphology of EVA composites, which provide better protect for the underlying resin.

Preparation and assembly of five photoresponsive polymers to achieve complex light-induced shape deformations

Five photoresponsive polymers towards ultraviolet (UV), visible, and near-infrared (NIR) light were prepared and assembled to achieve complicated light-induced shape deformation. The UV light responsive polymer was contributed by a synthesized linear polyurethane elastomer (azo-PU) containing azobenzene groups in the main chains, which presented both shape-memory effect and UV light-induced shape deformation behavior. The other four polymers that were sensitive to visible or NIR light consisted of crosslinked poly(ethylene-co-vinyl acetate) (EVA) composites mixing with gold nanoparticles (AuNPs), Nd(TTA)3Phen, Yb(TTA)3Phen, and Sm(TTA)3Phen as photothermal fillers, respectively. The results showed that the shape recoveries of these EVA composites were triggered merely by visible and/or NIR light with suitable wavelengths. Moreover, the assembly of the prepared five light-induced polymers in three different manners improved the spatiotemporal control of complicated shape deformations upon different light illumination sequences. Benefiting from the creation and assembly of five photoresponsive polymers with high wavelength selectivities, complex shapes of polymer specimens can be achieved in a remote and non-contact manner via simply tuning irradiation sequences. The reported materials here and their assembly manners provide a strategy to expand the applications of photoresponsive polymers.

Influence of ammonium polyphosphate on flame-retardant behavior and smoke suppression property of EVA/magnesium hydroxide composites

ABSTRACTTo overcome the flammability and smoke generation of EVA, samples with different mass fraction of magnesium hydroxide (MH) and ammonium polyphosphate (APP), have been prepared by internal mixer and cured by compression molded. The fire characteristics including smoke and heat production of EVA composites were studied by cone calorimeter test (CCT), limiting oxygen index test, UL-94 test, scanning electron microscopy, and thermogravimetric (TG) analysis, respectively. For the sample EVA5 loading 10.0 mass% APP and 40.0 mass% MH, the LOI value can be increased to the value of 31.1 and reach V-0 level. The CCT test showed that APP and MH could significantly improve the fire safety of EVA. Remarkably, the peak of heat release rate, the peak of smoke production rate, and total smoke release for EVA5 were decreased by 75.4%, 88.1% and 70.8% compared with pure EVA, respectively. TG test showed that APP promoted the char formation in the degradation process of EVA; as a result, the residual carbon was increased. The results indicated that APP combined with MH could facilitate the formation of the rigid intumescent char and obviously enhance the flame retardancy, smoke suppression and thermal stability of the EVA matrix.

An experimental study on the use of waste aggregate for acoustic attenuation: EVA and rice husk composites for impact noise reduction

The civil construction sector is one of the areas that most generates waste and consumes raw materials. To mitigate this environmental damage, is possible to use waste from other sectors to reduce raw material or by minimizing the generation of waste with materials of satisfactory durability. One of the main points to be evaluated is how such materials behave to the loads application and other mechanical stresses, and how it affects their acoustic performance. These mechanical tests usually are performed only in industrial materials. Still, the search for building performance is increasingly based on the sustainability, safety and habitability. Habitability requirements include acoustic performance, which is vital in buildings because its absence could cause stress, insomnia, hearing loss and other problems. So, this article proposes the use of EVA waste and rice husk in subfloors to decrease impact noise, replacing natural fine aggregates in the contents of 25, 50 and 75%. Compressive creep, dynamic stiffness and impact noise tests were performed. The results show that the use of both natural and artificial waste can represent gains in the efficiency of impact noise acoustic insulation for subfloors when used in larger proportions.