Ethylene vinyl acetate nanocomposites with hybrid silicate nanofillers of destabilized natural and commercial bentonites and organomontmorillonites

In this research, the interlayer destabilization process of bentonite was applied to gain a loosely packed, swelled, and disorganized clay layered structure for better polymer intercalation and filler dispersion during the fabrication of ethylene vinyl acetate (EVA) nanocomposites. Three different destabilization methods were applied to natural and commercial bentonites and their effects on swelling and platelets’ ordering of the clays were observed. X‐ray diffraction results suggest that the destabilization process through a combination of pH control and salt addition is more efficient in swelling both types of bentonite clays. This was supported by field emission scanning electron microscopy analysis where smaller, more loosely packed, and uniform platelets were observed due to swelling of both natural and commercial bentonite clays. The “destabilized” bentonites were used as the co‐nanofiller with the organically modified montmorillonite (OMMT) to form hybrid silicate nanofillers for EVA matrix reinforcement. Results show that the “destabilized” natural bentonite (NB) prepared by the combination of pH control and salt addition is most efficient in reinforcing the EVA matrix when combined with the OMMT by achieving 124.9% increment in tensile strength and 190.8% in toughness values. This could be related to the improved dispersion of bentonites upon the destabilization process that allows greater matrix–filler interactions in the nanocomposite system. In summary, the destabilization process through the combination of pH control and salt addition is the promising and practical technique to improve the dispersion of bentonites throughout the EVA matrix. Without the use of expensive and toxic chemicals, it can be adopted as a new approach to swell bentonites for more environmentally friendly nanocomposite technology. J. VINYL ADDIT. TECHNOL., 25:396–411, 2019. © 2019 Society of Plastics Engineers     

Morphology, rheology and dynamic mechanical properties of PP/EVA/clay nanocomposites

This paper reports on morphology, rheology and dynamic mechanical properties of polypropylene (PP)/ethylene vinyl acetate (EVA) copolymer/clay nanocomposite system prepared via a single step melt compounding process using a twin screw micro-compounder. Scanning electron microscopic (SEM) investigations revealed that the dispersed phase droplet size was reduced with incorporation of an organo-modified montmorillonite (OMMT). This reduction was more significant in presence of a maleated PP (PP-g-MAH) used as compatibilizer. Phase inversion in the compatibilized blends caused a further decrease in PP droplet size. The OMMT gallery spacing was higher in nanocomposites with EVA as matrix which could be attributed to higher tendency of OMMT nanoparticles towards EVA rather than PP. This enhanced tendency was confirmed by rheological analysis too. Transmission electron microscopy (TEM) results also showed that the majority of OMMT nanoparticles were localized on the interface and within EVA droplets. According to dynamic mechanical analysis, the compatibilized nanocomposites showed higher storage and loss moduli due to better dispersion of OMMT layers. The modulus enhancement of nanocomposites as a function of OMMT volume fraction was modeled by Halpin-Tsai’s-Nielsen expression of modulus for nanocomposites. The results of modeling suggested that the aspect ratio of the intercalated OMMT, in the form of Einstein coefficient (K _E), plays a determining role in the modulus enhancement of nanocomposites.     

Pre‐dispersing of montmorillonite nanofiller: Impact on morphology and performance of melt compounded ethyl vinyl acetate nanocomposites

Ethyl vinyl acetate (EVA) copolymers are potential materials for biomedical applications due to their exceptional mechanical properties and biocompatibility. As new medical device designs continue to reduce in size, new materials are required that exhibit improved strength and toughness. In this research, EVA nanocomposites containing synthetic montmorillonite (MMT) are being investigated as new biomedical materials with similar flexibility, biocompatibility, and biostability to neat EVA, but with far superior tensile strength and toughness. We show that the pre‐dispersing of the organo‐MMT prior to melt compounding with the EVA matrix can facilitate nanofiller exfoliation and dispersion in the EVA, thereby enabling significant improvement of EVA nanocomposite performance when high organo‐MMT loading (5 wt %) was added. It was observed that the polarity of pre‐dispersing medium influenced the nanofiller's surfactant organization and distribution, organo‐MMT exfoliation, and dispersion in the EVA, and also interphases of the host copolymer. Consequently, changes in morphology have brought noticeable effects on the mechanical and thermal properties of the EVA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43204.     

Halogen‐free intumescent flame‐retardant ethylene‐vinyl acetate copolymer system based on organic montmorillonite and graphene nanosheets

Halogen‐containing flame retardants are not preferred for environmental reasons. Herein, a halogen‐free intumescent flame‐retardant ethylene‐vinyl acetate copolymer (EVA/IFR) system containing organic montmorillonite (OMMT) and graphene nanosheets (GNSs) is fabricated with well dispersion structure, enhanced thermal‐oxidative resistance at high temperature. Interestingly, the amount of residual chars from thermogravimetric analysis is increased to 12.7 wt % at 700 °C, the EVA/IFR composite containing both OMMT and GNSs exhibits the best flame retardancy with the lowest peak heat release rate value of 529.58 kW m^?2, and the highest limited oxygen index value of 24.8%. The excellent flame retardancy is attributed to the formation of complete and compact protective char layer. Furthermore, the decreases of the mechanical properties caused by the addition of IFR are relieved and a high volume resistivity is maintained when combining OMMT and GNSs in the EVA/IFR system together. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46361.     

A Study on Poly(vinyl alcohol-co-ethylene)-graft-Polystyrene Reinforced with Two Functional Nanofillers

A facile route was adopted to graft polystyrene on poly(vinyl alcohol-co-ethylene) matrix. Poly(vinyl alcohol-co-ethylene)-graft-polystyrene (PVAE-g-PS) was then reinforced with two types of nanofillers, i.e., graphene oxide (GO) and nanodiamond functional graphene oxide (GO-ND). PVAE-g-PS/GO and PVAE-g-PS/GO-ND nanocomposite series reinforced with 0.1—5 wt.% nanofiller were fabricated by solution processing. Structure of nanofillers and composite was confirmed by FTIR. FESEM imaging revealed that nanodiamond functional GO platelets were fully incorporated into matrix. TGA demonstrated enhanced stability of PVAE-g-PS/GO-ND nanomposites containing GO-ND. Similarly, UL 94 and electrical conductivity measurement of GO-ND-based system were found to be superior compared to one of copolymer/GO.     

Effect of OMMTs on flame retardancy and thermal stability of poly(ethylene‐co‐vinyl acetate)/LDPE/magnesium hydroxide composites

The aim of this study was to prepare poly (ethylene‐co‐vinyl acetate) (EVA)/ low density polyethylene (LDPE)/magnesium hydroxide (MH) composites applicable in cable industry with required flame retardancy. For this reason, two types of organo‐modified montmorillonites (OMMT) with different surface polarites (Cloisite 15A and Cloisite 30B) at various concentrations, and also combination of these two OMMTs with overall loadings of 2 wt % and 5 wt % were used. The samples were compounded using a twin screw extruder with total (MH + OMMT) feeding of 55 wt % and 60 wt %. Limiting oxygen index (LOI) of the samples containing 2 wt % of OMMTs increased about 16% and dripping was suppressed according to vertical burning test (UL‐94V). Thermogravimetric results of EVA/LDPE/MH samples containing OMMT showed that the beginning of second step degradation was shifted about 50°C to higher temperatures. The composite tensile strength results showed enhancement by incorporating some amount of nanoclays with EVA/LDPE/MH composites. Scanning electron microscopy images confirmed that MH particles had better wetting by EVA matrix in presence of nanoclays. Oxidative induction time of the EVA/LDPE/MH/OMMT nanocomposites was 140 min, which was more than that of the samples without OMMT (20 min). Employing the equal weight ratios of the two OMMTs demonstrated a synergistic effect on flame retardancy of the samples according to the both tests results (LOI, UL‐94V). X‐ray diffraction analysis of the samples confirmed the intercalation/semiexfoliation structure of nanosilicate layers in the bulk of EVA/LDPE matrix. This led to longer elongation at break and thermal stability of Cloisite 15A based nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40452.     

Effect of compatibilizer and silane coupling agent on physical properties of ethylene vinyl acetate copolymer/ethylene‐1‐butene copolymer/clay nanocomposite foams

In this study an attempt was made to obtain lower density of ethylene‐vinyl acetate copolymer (EVA)/ethylene‐1‐butene copolymer (EtBC) foams without sacrificing mechanical properties. For this purpose EVA/EtBC/clay nanocomposite foams were prepared. To investigate the effect of compatibilizer and silane coupling agent on the physical properties of the EVA/EtBC/clay foams, maleic anhydride‐grafted EtBC (EtBC‐g‐MAH) and the most commonly used silane coupling agent in rubbers, bis(3‐triethoxysilylpropyl) tetrasulfide (Si‐69) were used in the preparation of EVA/EtBC/clay nanocomposite foams. The formation of EVA/EtBC/clay nanocomposite foams was supported by X‐ray diffraction results. And, using a compatibilzer and silane coupling agent, lower density of EVA/EtBC/clay nanocomposite foams were obtained without sacrificing mechanical properties except compression set. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3259–3265, 2006     

Nanoplatelet reinforcement of cavity cell walls in polymer foams using carbon dioxide supercritical fluid

Reinforcing the cavity cell walls of polymer foams using nanoparticles can offer a new era for the property‐structure‐processing field in the development of functionalized ultra‐light components and devices manufactured from foam. When the nanoparticles are exfoliated in polymers, the viscosity substantially increases and thus mixing or foaming usually becomes almost impossible. We use CO₂ supercritical fluid (CO₂ SCF) for the mixing and foaming of poly(ethylene‐vinyl acetate) copolymer (EVA) with montmorillonite (MMT) nanoplatelets. The in situ evaporation of CO₂ induces robust cavity cells of the EVA/MMT nanocomposite foam in a stable form of spherical shapes, which are seldom achieved by other methods. As the bubble grows and becomes stabilized in CO₂ SCF, the exfoliated MMT nanoparticles are aligned at the cell walls by the Gibbs adsorption principle to minimize the surface energy at the gas–liquid interface and increase the rupture strength of the cavity walls. It is demonstrated that the developed methodology can be successfully used for foaming EVA containing high vinyl acetate (VA) content (>40%). Since EVA is too soft to construct cell walls of foam using conventional methods, the applicability of the developed methodology is extensively broadened for superior adhesion and compatibility with other materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46615.     

Effect of hot air aging on the properties of ethylene‐vinyl acetate copolymer and ethylene‐acrylic acid copolymer blends

The aim of this investigation is to evaluate the effect of hot air aging on properties of ethylene‐vinyl acetate copolymer (EVA, 14 wt % vinyl acetate units), ethylene‐acrylic acid copolymer (EAA, 8 wt % acrylic acid units), and their blends. Attenuated total reflection‐Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), wide angle X‐ray diffraction, and mechanical tests are employed to investigate the changes of copolymer blends' structures and properties. Increase of carbonyl index derived from ATR measurements with aging time suggests the incorporation of oxygen into the polymeric chain. By DSC measurements, the enthalpy at low temperature endothermic peak (T_m2) of EAA becomes less and disappears after 8 weeks aging, but enthalpy at T_m2 of EVA is not influenced by the hot air aging and remains stable despite of the aging time. For various proportions of EAA and EVA blends, enthalpy at T_m2 decreases as the EAA proportion increases when aging time is 8 weeks; after several weeks of hot air aging, the various blends appear a same new peak just over the aging temperature 70°C which is due to the completion of crystals which are not of thermodynamic equilibrium state. Mechanical tests show that increase of crystallinity and hot air aging deterioration both have influence on the hardness, tensile strength, and elongation at break. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Free‐radical grafting of trans‐ethylene‐1,2‐dicarboxylic acid onto molten ethylene‐vinyl acetate copolymer

Distinctive features of free‐radical grafting of trans‐ethylene‐1,2‐dicarboxylic acid (TEDA) onto macromolecules of molten ethylene‐vinyl acetate copolymer (EVA) in the course of reactive extrusion have been investigated along with structure, mechanical characteristics, and high‐elastic properties of molten functionalized products (EVA‐g‐TEDA). It is shown that EVA‐g‐TEDA yield depends on both the peroxide initiator concentration and content of vinyl acetate units in the copolymer molecular structure. At functionalization, acid grafting is accompanied by secondary reactions of macromolecular degradation and crosslinking. With a low‐peroxide initiator concentration (0.1 wt %), degradation prevails; with a higher (0.3 wt %) concentration, crosslinking of macromolecules prevails. It is reported that monomers being grafted attach mostly over secondary carbon atoms in the polymer chain. EVA‐g‐TEDA appears to have a less perfect crystal structure with a lower‐melting temperature and crystallinity as against the starting polymer. The functionalized products display enhanced rigidity and lower deformability in comparison with the initial copolymer. Variations in the swelling ratio and melt strength of EVA‐g‐TEDA depend on the course of competing secondary processes of macromolecular degradation and crosslinking. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

In situ synthesis and characterization of polypropylene/polyvinyl acetate‐organophilic montmorillonite nanocomposite

A novel polymer‐nanoclay hybrid nanocomposite based on polyvinyl acetate (PVAc)‐organophilic montmorillonite (OMMT) has been reported via an in situ intercalated polymerization technique. The hybrid material was synthesized by one‐step emulsion polymerization of vinyl acetate in the presence of OMMT using polyvinyl alcohol as the stabilizing agent. The intercalated polymerization was characterized by X‐ray diffraction (XRD). The XRD patterns show that the interlayer spacing of OMMT after polymerization increased from 2.64 to 3.78 nm, indicating that the large macromolecular chain of PVAc was formed in the OMMT interlayer space. The Fourier transform infrared spectrum showed the characteristic absorption of PVAc in the OMMT particles separated from the nanocomposite, and the position of peaks shifted to high wave numbers. This showed that there was an interaction between PVAc and OMMT nanoparticles. A two‐fold blend composed of PVAc‐nano‐OMMT/PP was prepared by the melt‐blending technique. XRD and transmission electron microscopy images of the PVAc‐nano‐OMMT/PP composite further confirmed the formation of a partially delaminated nanocomposite structure. Thermogravimetry results showed that the thermal stability of PVAc‐nano‐OMMT/PP was greater than that of either polypropylene (PP) or Nano‐OMMT/PP blend. PVAc‐nano‐OMMT/PP had better toughness, as the mass fraction of OMMT was 5 wt %. The flame retardancy of PP, Nano‐OMMT/PP, and PVAc‐nano‐OMMT/PP composites was also studied. According to the limiting oxygen index (LOI) data and Cone calorimeter test, the addition of PVAc‐OMMT resulted in higher LOI and lower heat release rate, effective heat of combustion, smoke release course, and better flame retardancy and barrier properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of a novel silicone containing vinylic macromonomer and its uses in the preparation of poly (silicone‐co‐styrene‐co‐butylacrylate) with montmorillonite nanocomposite emulsion

A new silicone containing macromonomer, 4‐(methacrylamido) phenoxy polymethylhydrosiloxane (4‐MPMHS) with a vinyl group, was successfully synthesized. Then poly (silicone‐co‐styrene‐co‐butylacrylate) with montmorillonite, P (Si‐co‐St‐co‐BA) with MMT nanocomposite emulsion was prepared by in situ intercalative emulsion polymerization of styrene (St), butyl acrylate (BA), and 4‐MPMHS, in the presence of organic modified montmorillonite (OMMT) with different OMMT contents (0, 0.5, 1.0, 1.5, and 2 wt %). Potassium persulphate (KPS) was used as an initiator and sodium lauryl sulfoacetate (SLSA) and nonyl phenol ethylene oxide—40 U (NP‐40) were used as anionic and nonionic emulsifiers, respectively. The resulting macromonomer was characterized by elemental analysis, Fourier transformer infrared (FT‐IR), proton (¹H NMR), and carbon (¹³C NMR) nuclear magnetic resonance spectroscopes. The OMMT was characterized by FT‐IR and X‐ray diffraction (XRD). The nanocomposite emulsions were characterized by using Fourier Transform infrared spectroscopy (FT‐IR), laser light scattering, and surface tension method. Thermal properties of the copolymers were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and then the effects of OMMT percent on the water absorption ratio and drying speed were examined. Results showed that OMMT could improve the properties of emulsion. In other words, the properties of nanocomposite emulsions were better when compared with those of the silicone‐acrylate emulsion. The property of nanocomposite emulsion containing 1 wt % OMMT was the best one, and the following advantages were obtained: smaller particle size, faster drying speed, smaller surface tension, and improved water resistance by the incorporation of OMMT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of an (Intumescent flame retardant)‐montmorillonite combination on the thermal stability and fire‐retardant properties of LDPE/EVA nanocomposites

The combined effects of an organically modified montmorillonite (OMMT) and an intumescent flame retardant, poly (piperazine spirocyclic pentaerythritol bisphosphonate) (PPSPB), in (low‐density polyethylene)/[ethylene‐(vinyl acetate) copolymer] (LDPE/EVA) nanocomposites were observed. The results from X‐ray diffraction and transmission electron microscopy studies showed that exfoliated LDPE/EVA/PPSPB/OMMT nanocomposites were formed. Thermal stability and flammability properties were investigated by thermogravimetric analysis and cone calorimeter tests. The combination of PPSPB and montmorillonite improved thermal stability and reduced significantly the flammability, including peak heat release rate (PHRR), total heat release, average mass loss rate, etc. The PHRR of LDPE/EVA/PPSPB/OMMT was reduced by about 50% compared to that of an LDPE/EVA blend. The morphology and composition of the residues generated by cone calorimeter tests were investigated by scanning electronic microscopy (SEM) and energy dispersive X‐ray (EDX) analysis. The results of SEM showed that a compact and dense intumescent char was formed from the LDPE/EVA/PPSPB/OMMT nanocomposite upon combustion. The results of EDX examination revealed that the carbon content of this char was increased significantly by the combined effect of PPSPB and montmorillonite. J. VINYL ADDIT. TECHNOL., 19:285–292, 2013. © 2013 Society of Plastics Engineers     

Preparation and properties of poly(silicone‐co‐acrylate)/montmorillonite nanocomposite emulsion

Poly (silicone‐co‐acrylate)/montmorillonite nanocomposite emulsion were prepared by in situ intercalative emulsion polymerization of acrylate and organosilicone, in the presence of organic modified montmorillonite (OMMT) with different OMMT contents (0, 0.5, 1, 1.5, and 2 wt %). The nanocomposite emulsions were characterized with X‐ray diffraction (XRD), laser light scattering, fourier transform infrared (FTIR), rheological measurements, surface tension, drying speed, and water absorption property. Results showed that OMMT could improve the properties of emulsion, in other words, the properties of nanocomposite emulsion were better when compared with those of the silicone–acrylate emulsion. The properties of nanocomposite emulsion containing 1 wt % OMMT was the best one, and obtained the following advantages: smaller particle size, faster drying speed, shorter curing time, smaller surface tension, bigger apparent viscosity, and improved resistant water by the incorporation of OMMT. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3963–3970, 2006     

Styrene–butadiene–styrene/montmorillonite nanocomposites synthesized by anionic polymerization

We successfully synthesized an exfoliated styrene–butadiene–styrene triblock copolymer (SBS)/montmorillonite nanocomposite by anionic polymerization. Gel permeation chromatography showed that the introduction of organophilic montmorillonite (OMMT) resulted in a small high‐molecular‐weight fraction of SBS in the composites, leading to a slight increase in the weight‐average and number‐average molecular weights as well as the polydispersity index. The results from ¹H‐NMR revealed that the introduction of OMMT almost did not affect the microstructure of the copolymer when the OMMT concentration was lower than 4 wt %. Transmission electron microscopy and X‐ray diffraction showed a completely exfoliated nanocomposite, in which both polystyrene and polybutadiene blocks entered the OMMT galleries, leading to the dispersion of OMMT layers on a nanoscale. The exfoliated nanocomposite exhibited higher thermal stability, glass‐transition temperature, elongation at break, and storage modulus than pure SBS. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Influence of Matrix Polarity on the Properties of Ethylene Vinyl Acetate–Carbon Nanofiller Nanocomposites

A series of ethylene vinyl acetate (EVA) nanocomposites using four kinds of EVA with 40, 50, 60, and 70 wt% vinyl acetate (VA) contents and three different carbon-based nanofillers—expanded graphite (EG), multi-walled carbon nanotube (MWCNT), and carbon nanofiber (CNF) have been prepared via solution blending. The influence of the matrix polarity and the nature of nanofillers on the morphology and properties of EVA nanocomposites have been investigated. It is observed that the sample with lowest vinyl acetate content exhibits highest mechanical properties. However, the enhancement in mechanical properties with the incorporation of various nanofillers is the highest for EVA with high VA content. This trend has been followed in both dynamic mechanical properties and thermal conductivity of the nanocomposites. EVA copolymer undergoes a transition from partial to complete amorphousness between 40 and 50 wt% VA content, and this changes the dispersion of the nanofillers. The high VA-containing polymers show more affinity toward fillers due to the large free volume available and allow easy dispersion of nanofillers in the amorphous rubbery phase, as confirmed from the morphological studies. The thermal stability of the nanocomposites is also influenced by the type of nanofiller.     

Exertion of Inhibiting Effect by Aluminosilicate Layers on Swelling of Solution Blended EVA/Clay Nanocomposite

Summary: Ethylene vinyl acetate (EVA) copolymer/dodecyl ammonium ion intercalated montmorillonite (12Me‐MMT) nanocomposites were swelled in xylene under atmospheric condition. Swelling index of these nanocomposites decreased with filler loading indicating that the solvent uptake of these nanocomposites was inversely related to the filler contents. The volume fractions of nanocomposites showed an increasing trend with filler concentration because of unswelling effect exerted by aluminosilicate layers. The cross‐link density was determined using the Flory‐Rehner equation and it was observed that the cross‐link density of these nanocomposites also showed an increasing trend with increasing filler loading. Free energy change (ΔG_mix) and the change in entropy (ΔS_mix) on swelling of EVA/12Me‐MMT nanocomposites in xylene were calculated and these values reaffirmed that the interaction between polymer chains and silicate layers was very strong which induced remarkable inhibiting ability on EVA matrix when swelled in xylene.

TEM photograph of EVA/12Me‐MMT nanocomposite containing 8 wt.‐% 12Me‐MMT.     

New fabricate of styrene-butadiene rubber/montmorillonite nanocomposites by anionic polymerization

Styrene-butadiene rubber/montmorillonite (SBR/MMT) nanocomposites were successfully synthesized by in situ living anionic polymerization with n-BuLi as initiator. The results from kinetics study and ¹H NMR indicated that the addition of organophilic montmorillonite (OMMT) did not changed the living copolymerization and the components of the copolymer on the whole when OMMT content was lower than 3 wt %. However, gel permeation chromatography showed that the introduction of OMMT resulted in small amount of high-molecular weight fraction of SBR in the composites, leading to an increase in the weight-average molecular weight and polydispersity index, but the unchangeableness of the number-average molecular weight. The result from transmission electron microscopy and X-ray diffraction revealed that a completely exfoliated structure existed in the nanocomposite with 25 wt % styrene and OMMT content from 1 to 4 wt %, and styrene played an important role in the expanding of OMMT layers. Moreover, the nanocomposites possessed higher glass-transition temperature, thermal stability, tensile strength and elongation at break than SBR when the OMMT content ranged from 2.5 to 4 wt %. A schema was proposed to illustrate the formation of the nanocomposite and the exfoliation structure with physical cross-linking between SBR chains and OMMT.     

Enhanced thermal conductivity and mechanical properties of hybrid MoS2/h‐BN polyurethane nanocomposites

Nanocomposites based on molybdenum disulfide (MoS₂), hexagonal boron nitride (h‐BN) and hybrid MoS₂/h‐BN nanofillers with different wt % in elastomeric polyurethane (PU) were studied with respect to their microstructure, thermal and mechanical properties. Tensile tests showed increases up to 80% in Young`s modulus for both h‐BN and hybrid MoS₂/h‐BN composites. These results agree with dynamic mechanical analysis tests, which confirm an increase of up to 106% in storage modulus for hybrid MoS₂/h‐BN with 0.5 wt % content. When the hybrid MoS₂/h‐BN nanofillers were incorporated into the polymeric matrix, increases up to 102% in crosslink density were observed, indicating that strong interactions between the hybrid nanofillers and PU were established. However, the most important synergistic effect between the mixture of MoS₂ and h‐BN nanoadditives was the increase of up to 752% in thermal conductivity with respect to neat polymer. Therefore, hybrid composites based in two‐dimensional MoS₂/h‐BN nanofillers with multifunctional attributes can be applied in advanced polymeric materials that require high mechanical and thermal performance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46560.     

Study on the nonisothermal crystallization process of mLLDPE/EVA blends using FTIR micro‐spectroscopy

The nonisothermal crystallization process has been investigated by Fourier transform infrared (FTIR) micro‐spectroscopy for the 40/60 wt % blends of metallocene linear low density polyethylene (m‐LLDPE) and ethylene/vinyl acetate copolymer (EVA) at the molecular level. In the cooling process, thermal spectra of mLLDPE/EVA blends were collected between 150°C and 67°C at 1°C interval. According to the van't Hoff equation at constant pressure, the changes of absorbance ratio corresponding to high and low vibrational states were calculated; hereby, apparent enthalpy differences of vibration energy states transformation (?H_v) of characteristic groups could be obtained. Combining with DSC analysis, two exothermal peaks were examined in the crystallization process, corresponding to mLLDPE‐rich and EVA‐rich domains, respectively; while in comparison of the ?H_v values of various characteristic groups corresponding to the two exothermal peaks, the bending vibrational mode of methylene groups has been found to make a prominent contribution to the movement and regular arrangement of mLLDPE and EVA chain segments towards each rich domain in the crystallizing process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 261–267, 2005