Preparation and characterization of modified‐clay‐reinforced and toughened epoxy‐resin nanocomposites

Epoxy–clay nanocomposites were prepared by the dispersion of an organically modified layered clay in an epoxy resin (diglycidyl ether of bisphenol A) and curing in the presence of methyl tetrahydro acid anhydride at 80–160°C. The nanometer‐scale dispersion of layered clay within the crosslinked epoxy‐resin matrix was confirmed by X‐ray diffraction and transmission electron microscopy, and the basal spacing of the silicate layer was greater than 100–150 Å. Experiments indicated that the hydroxyethyl groups of the alkyl ammonium ions, which were located in the galleries of organically modified clay, participated in the curing reaction and were directly linked to the epoxy‐resin matrix network. Experimental results showed that the properties of epoxy were improved, evidently because of the loading of organically modified clay. The impact strength and tensile strength of the nanocomposites increased by 87.8 and 20.9%, respectively, when 3 wt % organic clay was loaded, and this demonstrated that the composites were toughened and strengthened. The thermal‐decomposition and heat‐distortion temperatures were heightened in comparison with those of pure epoxy resin, and so were the dynamic mechanical properties, including the storage modulus and glass‐transition temperature. Moreover, experiments showed that most properties of the composites were ameliorated with low clay contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2649–2652, 2004     

Synthesis,characterization, and thermo mechanical properties of siloxane‐modified epoxy‐based nano composite

In this study, polymer hybrid composites were synthesized by sol‐gel process. 3‐Amino‐propyltrimethoxysilane [APTMS)/γ‐Glycidoxypropyl trimethoxy‐silane (GPTMS); (4, 4′‐Methylene‐dianiline (DDM)] and 1,4‐Bis(trimethoxysilylethyl) benzene (BTB) were added to DGEBA type epoxy resin for anticipated to exhibit excellent thermal stability. Boron trifluoride monoethylamine (BF₃MEA) was used as catalyst. The structure of nanocomposites was characterized by attenuated total reflectance (ATR) and solid‐state ²⁹Si NMR which suggest EP‐APTMS‐BTB/EP‐GPTMS‐BTB possesses T³; T¹–T⁰, and T¹ structures when the BTB content was lower than 10 wt % and higher 20 wt %, respectively. BF₃MEA was proved to be an effective catalyst for the sol‐gel reaction of APTMS, but it could not promote for GPTMS. From TEM microphotographs, EP‐APTMS‐BTB (10 wt %) possesses a dense inorganic structure (particle size around 5–15 nm) compare with the loose inorganic structure of EP‐GPTM‐/BTB (10 wt %). DSC, TGA were use to analyze the thermal properties of the nanocomposites and DMA was used to analyze the dynamic mechanical properties of hybrid composites. The T_gs of all nanocomposites decreased with the increasing BTB content. A system with BTB content lower than 10 wt % showed good dynamic mechanical property and thermal stability (Td₅ increased from 336°C to 371°C, char yield increased from 27.4 to 30.2%). The structure of inorganic network affects the Td₅ and dynamic mechanical properties of composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40984.     

Flexible epoxy novolac coatings: Use of cardanol‐based flexibilizers

Flexible epoxy novolac coatings were developed by reacting an epoxy novolac resin, poly[(phenylglycidyl ether)‐co‐formaldehyde] (PPGEF) with an amine curing agent, 4,4′‐diamino‐3,3′‐dimethyldicyclohexyl methane (BMCHA), cardanol based reactive diluent (Cardolite NC‐513) and two different cardanol‐based flexibilizers (Cardolite NC‐514 and Cardolite NC‐547). The flexibilizer content was varied from 5 to 10% by weight of the resin. These resins were coated onto the stainless steel panels and tested for their gloss, cross‐hatch adhesion, falling weight impact resistance, flexibility, abrasion, scratch hardness, solvent scrub resistance, and chemical resistance. The thermo‐mechanical properties of these coatings were determined by TGA, DSC, DMTA, and tensile strength measurements. The cryofractured specimens were subjected to SEM analysis. The influence of structural differences of two flexibilizers on the coating properties was investigated. These coatings exhibited excellent properties and have great potential in industrial applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44920.     

Study of thermal stability and ablation behavior of carbon/epoxy‐novolac composites

The use of carbon/epoxy‐novolac composites as advanced ablative materials for insulation of exit cone of solid‐propellant rocket nozzles are studied. In this article, three types of carbon fabrics are used and their composites are prepared by use of impregnation and hand lay‐up methods. To study the thermal stability and ablation behavior, these composites are tested by thermal tests such as thermogravimetric analysis (TGA) and oxyacetylene standard flame tests; the latter test is one of the most important standard tests of ablative materials. The test apparatus is made according to American standard, ASTM‐E‐285‐80, and over 33 polymeric composites and 3 steel specimens were carried out according to its standards. It is found that the composites that are made up of C‐9750 fabric (high‐strength carbon fabric) in comparison with steel and the other types of carbon fabric specimens have the highest thermal stability and the best ablation behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2455–2461, 2003     

Effect of temperature‐pressure cycles on structural properties of epoxy‐based composites for printed circuit boards applications

During multilayer printed circuit board production, cyclic pressure–temperature (P–T) treatments can give rise to mechanical and thermal stresses with subsequent inner delamination phenomena. These are mainly related to the thermomechanical properties of epoxy resins used in the manufacturing process. In this study, the physical and chemical changes of commercial epoxy‐based prepregs were investigated as a function of P–T treatments by means of thermogravimetric analysis, differential scanning calorimeter, and Fourier transform infrared‐photoacoustic spectroscopy. It was verified that the thermal properties start to decrease after the first P–T treatment. In connection, absorbance spectra indicated that the peaks at 2273 cm^?1 and 2235 cm^?1 (cyanate group) disappeared after this treatment. Heat transfer as a function of laminate thickness (consequently, as a function of P–T treatment) is one variable that probably contributes to the findings in the work. The results of this study indicated that the analytical methods were satisfactory to determine the beginning of the deterioration of the printed circuit as a function of the P–T treatments. They can be used as a reference for quality controls and to prevent mechanical problems such as interlaminar fractures in the relevant printed circuits. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and dielectric properties of short‐carbon‐fibers/epoxy‐modified‐organic‐silicone‐resin as heat resistant microwave absorbing coatings

Heat resistant microwave absorbing coatings were prepared by brushing and thereafter heat treatment, using epoxy modified organic silicone resin as binding material, short carbon fibers (C_sf) as absorbers, talcum powder and glass powder as filling materials. The mechanical and dielectric properties of the coatings before and after heat treatment at 600°C for 10 mins were studied. The results showed that the adhesive power after heat treatment enhances remarkably, both the real (ε′) and imaginary (ε″) parts of the permittivity of the coatings increase with increasing C_sf content in the frequency range of 8.2–12.4 GHz. The calculation value of the reflection loss as single layer absorber indicates that epoxy modified organic silicone resin coatings containing short carbon fibers could be a promising radar absorbing material applied at high temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1392‐1398, 2013     

The effect of nanoclay and MWNT on fire‐retardency and mechanical properties of unsaturated polyester resins

The influence of nanomaterials such as Multi‐Walled Carbon NanoTubes (MWNT) and organoclay (Cloisite 30B) on the physical and mechanical properties of thermoset matrix such as Unsaturated Polyester (UP) resins is investigated. Although styrene containing UP resins have a wide spread application in industry, lack of information exists regarding the behavior of MWNT/organoclay/polyester ternary nanocomposite systems. The main aim of this research was first to evaluate the effect of nanofiller on the flammability of UP resins and, second, to characterize their mechanical properties such as toughness and their tensile strength. The rheological studies showed shear thinning for samples of UP resins containing MWNT and Cloisite 30B. The cone calorimetry measurement was used to evaluate the flame‐retardency, the gas emission of the nanocomposite and whether or not this system can be designated as a nanocomposite. This was understood in the test by the peak heat release rate being lowered and shifted to shorter times. Furthermore, the tensile and impact properties of samples were evaluated. The obtained results indicated that nanofiller particles caused both increase and decrease in the impact and tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Theoretical analysis of fracture of tetra‐needle‐like ZnO whisker in polymer composite

It is of practical importance to develop the tetra‐needle‐shaped ZnO whisker (T‐ZnOw)‐reinforced polymer composites that have isotropic properties. To give a guidance of material design and manufacture, it is necessary to have a theoretical analysis of the fracture mechanisms of this peculiar structure fiber in polymer composites. Based on previous investigations of the T‐ZnOw‐reinforced polymer composites, and from the viewpoint of materials mechanics, here we analyzed the distribution of stresses on different points of the tetra‐ needle‐like crystal whiskers in a composite and calculated the total stress at the connection point. The results indicate that the stress on the connection point is proportional to the exerting force and correlates with the dimension, the size, and the location of the whiskers. According to the theoretical derivations, it was found that the stress at the connection point of the T‐ZnOw is much larger than that at the others, leading to breakage on that point mainly or wholly, which is in accordance with the experimental observations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of cardanol‐based epoxidized novolac resins modified with carboxyl‐terminated butadiene–acrylonitrile copolymer

Cardanol‐based, novolac‐type phenolic resins were synthesized with a cardanol‐to‐formaldehyde molar ratio of 1 : 0.7 with different dicarboxylic acid catalysts, including oxalic and succinic acids. These novolac resins were epoxidized with a molar excess of epichlorohydrin at 120°C in a basic medium. The epoxidized novolac resins were separately blended with different weight ratios of carboxyl‐terminated butadiene–acrylonitrile copolymer (CTBN) ranging between 0 and 20 wt % with an interval of 5 wt %. All of the blends were cured at 120°C with a stoichiometric amount of polyamine. The formation of various products during the synthesis of the cardanol‐based novolac resin and epoxidized novolac resin and the blending of the epoxidized novolac resin with CTBN was studied by Fourier transform infrared spectroscopy analysis. Furthermore, the products were also confirmed by proton nuclear magnetic resonance and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy analysis. The molecular weights of the prepared novolacs and their epoxidized novolac resins were determined by gel permeation chromatography analysis. The blend samples, in both cases, with 15 wt % CTBN concentrations showed the minimum cure times. These blend samples were also the most thermally stable systems. The blend morphology, studied by scanning electron microscopy analysis, was, finally, correlated with the structural and property changes in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effects of soft‐segment molecular weight and organic modifier on properties of organic‐modified MMT‐PU nanocomposites

The effects of soft‐segment molecular weight and organic modification of montmorillonite (MMT) on thermal and mechanical properties of segmented polyurethane (PU) elastomers were investigated. The PU/MMT nanocomposites were prepared by in situ polymerization, and the compositions included soft segments with number average molecular weights of 1000, 2000, and 2900, and organic‐modified MMT (including MMT‐30B and MMT‐I30E). The nanocomposites produced were characterized using wide‐angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and mechanical testing. The TEM and XRD results revealed that both MMT‐30B and MMT‐I30E were intercalated, and partially exfoliated by the PU. Mechanical tests showed that the PU1000 series in soft‐segment molecular weight yielded superior tensile properties compared with the PU2000 and PU2900 series. Also, for a given molecular weight of soft segment in PU, the MMT‐30B nanocomposites exhibited greater increases in Young's modulus, tensile strength, and elongation at break than the MMT‐I30E counterpart, and the crystallinity of PU was enhanced by the clays. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Addition‐cure‐type phenolic resin based on alder‐ene reaction: Synthesis and laminate composite properties

A maleimide‐functional phenolic resin was reactively blended with an allyl‐functional novolac in varying proportions. The two polymers were coreacted by an addition mechanism through Alder‐ene and Wagner–Jauregg reactions to form a crosslinked network system. The cure characterization was done by differential scanning calorimetry and dynamic mechanical analysis. The system underwent a multistep curing process over a temperature range of 110–270°C. Although the cure profiles were independent of the composition, the presence of maleimide led to a reduced isothermal gel time of the blend. Increasing the allylphenol content decreased the crosslinking in the cured matrix, leading to enhanced toughness and improved resin‐dominant mechanical properties of the resultant silica laminate composites. Changing the reinforcement from silica to glass resulted in further amelioration of the resin‐reinforcement interaction, but the resin‐dominant properties of the composite remained unaltered. Increasing the maleimide content resulted in enhanced thermal stability. Integrating both the reactive groups in a single polymer and its curing led to enhanced thermal stability and T_g, but to decreased mechanical properties of the laminate composites. This can be attributed to a brittle matrix resulting from enhanced crosslinking facilitated by interaction of the reactive groups located on the polymer of an identical backbone structure. The cured polymers showed a T_g in the range of 170–190°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 737–749, 2001     

Interaction of a phosphorus‐based FR,a nanoclay and PA6—Part 1: Interaction of FR and nanoclay

The thermal decomposition of organophosphorus fire‐retardant (OP1311) and/ or organonanoclay (Cloisite 30B) is hereby investigated employing thermogravimetric analysis (TGA), to give an insight into their intrinsic behaviour and interaction in polymer nanocomposites for fire safety applications, because the addition of OP1311 and Cloisite 30B in Polyamide 6 (PA6) seems to have a synergistic effect on the thermal decomposition of PA6 (part 2 of the paper). An important objective of this research was to determine to what extent phosphorus components escape in the gaseous phase, which will affect the heat of combustion of the fire‐retarded polymer. The decomposition products arising from pyrolysis and combustion are investigated by means of Fourier transform infrared spectroscopy. Under pyrolytic conditions, the inclusion of Cloisite 30B into OP1311 (FR) shows a synergistic effect on the initial mass loss at low temperature of ～280–420°C and leads to the acceleration of the thermal degradation process. While the DTG curve of Cloisite 30B shows two distinct degradation peaks (steps) that of OP1311 and OP1311 plus Cloisite 30B show four degradation steps. TGA measurements of OP1311 in nitrogen show more mass loss than in air, whereas Cloisite 30B gives similar amounts of mass loss in air and nitrogen. In nitrogen, the major evolved gaseous species from Cloisite 30B alone are hydrocarbons, 2‐(diethylamino)ethanol and water, whereas the evolved gases from that of OP1311 at ～320°C are mainly water, at ～420°C, carbon dioxide, water and ammonia and at 480–570°C diethylphosphinic acid. Under thermo‐oxidative conditions, the gases evolved are mainly carbon dioxide and water from both Cloisite 30B and OP1311. Copyright © 2009 John Wiley & Sons, Ltd.     

Poly (diallyldimethylammoniumchloride)/sodium‐montmorillonite composite; structure,and adsorption properties

A cationic polyelectrolyte, poly (diallyldimethylammoniumchloride) (PDADMAC) and a smectite‐type layered silicate (sodium activated montmorillonite clay (Sodium‐Montmorillonite, NaMt)), intercalated composites (PDADMAC/NaMt) were prepared. Basal spacings (d001) of NaMt in composites were measured by X‐Ray diffraction analysis (XRD). Ultrasonic addition of low molecular weight PDADMAC into the NaMt structure (at very low concentration and very low PDADMAC(g)/NaMt(g) ratios) resulted in good adsorbing properties both for positively and negatively charged dyes. The adsorption kinetics of the prepared composites both for negatively charged [remazol black (RB)] and positively charged [methylene blue (MB)] reactive dyes were investigated. The RB adsorption efficiency of the positively charged composite is approximately three times that of the pure NaMt while its MB adsorption efficiency is as good as that of pure NaMt. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of reprocessing on the hygroscopic behavior of natural fiber high‐density polyethylene composites

Detailed analysis of the effects of recycling process on long‐term water absorption, thickness swelling, and water desorption behavior of natural fiber high‐density polyethylene composites is reported. Composite materials containing polyethylene and wood flour, rice hulls, or bagasse fibers and 2% compatibilizer were produced at constant fiber loading and were exposed to a simulated recycling process consisting of up to five times grinding and reprocessing under controlled conditions. A wide range of analytical methods including water absorption/desorption tests, thickness swelling tests, density measurement, scanning electron microscopy, image analysis, contact angle, fiber length analysis, Fourier transform infrared spectroscopy, and tensile tests were employed to understand the hygroscopic behavior of the recycled composites. Water absorption and thickness swelling behaviors were modeled using existing predictive models and a mathematical model was developed for water desorption at constant temperature. Results indicated that generally the recycled composites had considerably lower water absorption and thickness swellings as compared with the original composites which were attributed to changes in physical and chemical properties of the composites induced by the recycling process. Water desorption was found to be faster after recycling. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of an oxide fiber‐reinforced silica matrix composite

Oxide (Nextel? 440) fiber‐reinforced silica composites, with the density and porosity of 1.97 g/cm³ and 21.8%, were prepared through sol‐gel. Their average flexure strength, elastic modulus, shear strength, and fracture toughness at room temperature were 119.7 MPa, 25.6 GPa, 10.8 MPa, and 4.0 MPa·m^1/2, respectively. The composites showed typical toughened fracture behavior, and distinct pullout fibers were observed at the fracture surface. Their mechanical properties were performant up to 1000°C, with the maximum flexural strength of 132.2 MPa at 900°C. Moreover, the composites showed good thermal stability, even after thermal aging and thermal shock at elevated temperatures.     

Mechanical and anticorrosion properties of furan/epoxy‐based basalt fiber‐reinforced composites

A furan/epoxy blend applicable to composite manufacture was studied and corresponding basalt fiber‐reinforced composites were prepared. The processability, mechanical properties, and reasons for the improved mechanical properties of this blend were investigated by rheology machine, mechanical testing machine, and scanning electron microscopy. With excellent processability, furan/epoxy was suitable for manufacturing composites. Furan/epoxy with the ratio of 5/5 showed the best properties, and the impact strength, flexural strength and flexural modulus were 15.43 kJ/m², 102.81 MPa, and 3209.40 MPa, respectively. The river‐like fracture surface of the furan/epoxy system was well consistent with the mechanical properties. The mechanical and anti‐corrosive properties of basalt fiber‐reinforced furan/epoxy composites were also studied. The mechanical properties of composites changed the same as those of furan/epoxy matrix did. Furan resin effectively improved the anti‐acid but not anti‐alkali property of composites, probably because furan could be cured in acidic condition and basalt fiber was resistant to acid and alkali. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44799.     

Epoxy Composites Reinforced with Negative‐CTE ZrW2O8 Nanoparticles for Electrical Applications

The potential for incorporating negative‐CTE zirconium tungstate (ZrW₂O₈) nanoparticles in an epoxy matrix with the aim of developing epoxy/ZrW₂O₈ nanocomposites with tailored CTE values for electrical applications is investigated. The ZrW₂O₈/epoxy nanocomposites are prepared through incorporation of up to 20 vol% unfunctionalized nanoparticles or silane‐functionalized nanoparticles containing either epoxy or amine end groups. Improvements in thermomechanical and dynamic mechanical properties of the epoxy matrix are achived with no detrimental effect on the dielectric strength, which suggests that these nanocomposites could be viable candidates for a wide range of electrical applications.

     

Mechanical modeling of a three‐phase nanocomposite polymeric material

The presented model to predict the elastic modulus of a polymer/ellipsoidal filler/oblate platelet system is based on Eshelby's equivalent inclusion method and Mori‐Tanaka's back‐stress analysis. We considered wood flour and intercalated clay particles in three‐phase polymer nanocomposites as ellipsoidal and oblate platelet shapes, respectively. The intercalated clay particles along with the polymer chains in the clay galleries are treated as equivalent oblate fillers (EOFs). Via controlling wood flour and EOF aspect ratios (α and β) and the silicate layer number (n) in an EOF, the model prediction was compared with experimental data. The model predicted α and β values are within a range of 2.4–5 and 44–75, respectively, which are in good agreement with experimental observations. Quantitative agreement between model prediction and experimental data is achieved for α = 3.7 and β = 75 when n = 2. The proposed model recovers the two‐phase results for polymer/ellipsoidal filler systems or polymer/oblate platelet systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of water‐insoluble functional copolymers containing amide,amine, and carboxylic acid groups and their metal‐ion‐uptake properties

The crosslinked poly[N‐(3‐dimethylamino)propylmethacrylamide] [P(NDAPA)] and poly[N‐(3‐dimethylamino)propylmethacrylamide‐co‐acrylic acid] [P(NDAPA‐co‐AA)] were synthesized by radical polymerization. The resins were completely insoluble in water. The metal‐ion‐uptake properties were studied by a batch equilibrium procedure for the following metal ions: silver(I), copper(II), cadmium(II), zinc(II), lead(II), mercury(II), chromium(III), and aluminum(III). The P(NDAPA‐co‐AA) resin showed a lower metal‐ion affinity than P(NDAPA), except for Hg(II), which was retained at 71% at pH 2. At pH 5, the resin showed a higher affinity for Pb(II) (80%) and Cu(II) (60%), but its affinity was very low for Zn(II) and Cr(III). The polymer ligand–metal‐ion equilibrium was achieved during the first 20 min. By changing the pH, we found it possible to remove between 60 and 70% of Cd(II) and Zn(II) ions with (1M, 4M) HClO₄ and (1M, 4M) HNO₃. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5232–5239, 2006     

Preparation and properties of epoxy‐modified tung oil waterborne insulation varnish

This work aimed to develop a novel epoxy‐modified tung oil waterborne insulation varnish with blocked hexamethylene diisocyanate as a curing agent. The Diels–Alder reaction between tung oil and maleic anhydride, and the ring‐opening esterification reaction of epoxy resin were confirmed. The conversion rate of epoxy was explored as a function of reaction time and temperature. The effects of epoxy resin content on the thermal stability, water absorption and insulation properties (insulation strength, volume resistivity, and surface resistivity) of films were investigated, and the resistances of films to salted water were evaluated. The increase in epoxy resin contents could improve the thermal stability and insulation properties of films, and decreased the water adsorption of films, but when the epoxy resin content reached 30% and above, the water solubility of resin became poor. After being immersed in 3.5 wt % NaCl solution, the electrical insulation strength of films were lower than that in dry state, and decreased as the immersed time prolonged. In particular, the electrical insulation strength loss of films increased significantly for epoxy resin content at 15% and below. Furthermore, the increase of epoxy resin content could improve the hardness and adhesion of films, but the flexibility of films became worse. On the basis of experimental, the epoxy resin content at 25% was appropriate to prepare waterborne epoxy‐modified tung oil resin. The resulting varnish may have potential as an immersing insulation varnish for the spindle of electric motor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42755.