In situ preparation of cyclohexanone formaldehyde resin/layered silicate nanocomposites

In this study, in situ modified cyclohexanone formaldehyde resin (CFR) was prepared from clay (montmorillonite) and polydimethylsiloxane with diamine chain ends [α,ω‐diamine poly(dimethyl siloxane) (DA.PDMS)] in the presence of a base catalyst. Different clay contents (from 0.5 to 3 wt %) were used to produce clay‐modified nanocomposite ketonic resins [layered clay (LC)–CFR] and clay‐ and DA.PDMS‐modified nanocomposite ketonic resins (DA.PDMS–LC–CFR). The polymeric nanocomposite material prepared by this method was directly synthesized in one step. These nanocomposites were confirmed from X‐ray diffraction to have a layered structure with a folded or penetrated CFR, and they were further characterized via Fourier transform infrared spectroscopy–attenuated total reflectance and NMR spectroscopy. The thermal properties of all of the resins were studied with differential scanning calorimetry and thermogravimetric analysis. All of the resins showed higher thermal stability than their precursor CFR resin. The obtained samples were also characterized morphologically by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39918.     

Characterization of nanocomposite resol resins: Individual/synergist effects of alendronic acid and sepiolite

Alendronic acid modified resol nanocomposite resins (AA‐PFNCRs) and sepiolite modified resol nanocomposite resins (SEP‐PFNCRs) have been synthesized by in situ method in the presence of base catalyst. Additionally, the synergistic effects of alendronic acid and sepiolite clay (AA‐SEP‐PFNCR) on the resol resin have been studied. The structure, morphology, and thermal properties of these nanocomposites have been investigated by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and X‐ray Diffraction (XRD). The results demonstrated the interactions between the fillers and resol resin. Thermal properties of nanocomposite resins were improved due to alendronic acid and sepiolite. The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43807.     

Synthesis and characterization of styrene butadiene rubber—Bentonite clay nanocomposites

In the present study, naturally occurring unfractionated bentonite clay was used to prepare styrene butadiene rubber/bentonite clay nanocomposite by latex stage blending. The bentonite clay was organo‐modified by in situ resol formation by the reaction of resorcinol and formaldehyde. The latex clay mixture was co‐coagulated with acid. The resulting clay masterbatch was compounded and evaluated by Fourier Transform Infrared spectroscopy, X‐ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X‐ray spectroscopy (EDS), Scanning Electron Microscopy, Thermogravimetric analysis, and Differential Scanning Calorimetry. XRD showed that the interplanar distance of the in situ resol‐modified bentonite clay increased from 1.23 to 1.41 nm for the unmodified bentonite. TEM analysis indicated partial exfoliation and/or intercalation. EDS (Si and Al mapping) of the clay revealed the nature of the dispersion in the nanocomposites vis‐à‐vis the conventional styrene‐butadiene rubber (SBR)/bentonite clay composite. Thermogravimetric analysis was used to compare the decomposition trends of the SBR/clay nanocomposites with the SBR/clay composite. The glass transition temperature of SBR/clay nanocomposites increased as compared with that of neat SBR. Substantial improvement in most of the other mechanical properties was also observed in case of the nanocomposites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Study on BMI modified allyl‐functional novolac resin/silica cloth composites: Effect of allylation degree on thermal and mechanical properties

A series of allyl‐functional novolac resin with various allylation degree, from 32.4 to 114.6%, were synthesized and then blended reactively with 4,4′‐bismaleimide biphenyl methane (BMI) at a weight ratio of 2.50:1 to get BMI‐modified allyl‐functional novolac (BMAN) resins. BMAN resins were used as matrix resin to fabricate BMAN/Silica cloth composites by compression molding process. Heat‐resistant properties of the composites were evaluated by means of dynamic mechanical analysis. The results indicated that thermal resistance of the composites increased as allylation degree of BMAN resins increased. Mechanical properties of the composites, including interlaminar shear strength (ILSS) and flexural strength at room temperature and 300°C, were determined, and the results showed that with increase in allylation degree of matrices the ILSS and flexural strength values of composites at room temperature decreased, but the values of ILSS and flexural strength at 300°C increased. Scanning electron microscope morphology analysis of fracture surface for composites revealed that tough interphase was responsible for the better mechanical properties of the composites based on lower allylation degree resins. POLYM. COMPOS., 28:180–185, 2007. © 2007 Society of Plastics Engineers     

Control of microvoids in resol phenolic resin using unsaturated polyester

A major drawback of cured phenol formaldehyde resin is the presence of microvoids, resulting from the liberation of condensation byproducts. In an attempt to rectify this, phenolic resol resin was blended with unsaturated polyester (UP). UPs with various maleic anhydride (MA) to phthalic anhydride (PA) ratios were synthesized and later mixed with resol resin in various proportions. The best MA/PA ratio was found out by determining the specific gravity, acetone‐soluble matter, and volatile content of the cast blend, cured under a satisfactory time–temperature schedule. The influence of acid value of the UP and the most desirable UP content were also investigated on the basis of the quality of the modified phenolic samples. The structural changes in the modified resin were studied using FTIR spectroscopy. Scanning electron micrographs (SEM) of the fractured surfaces were obtained to ascertain the extent of microvoids in the modified resin. Both thermogravimetric analysis results and SEM micrographs confirm the effectiveness of UP in reducing the microvoids in the cast resol resin. The tensile and impact strengths of the samples also reflect the superior quality of the resol phenolic resins that have been modified by UP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Antireflective coatings using organically modified silica and polyimide via solution casting method

Antireflective (AR) coatings were prepared using a polyimide and two types of organically modified silica colloids via a solution casting method. The optically transparent polyimide was prepared from 2,2′‐Bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 4,4′‐oxydianiline (ODA). The silica colloids were driven to the coating‐air interface by either the fluorinated alkyl group or PDMS (Polydimethylsiloxane) segment tethered onto the silica colloids. The amount of fluorinated alkyl groups and the molecular weight of the siloxane grafted on the silica colloid were varied. The PDMS‐silica and fluorosilica colloids were characterized by TEM (Transmission Electron Microscopy), DLS (Dynamic Light Scattering), FTIR (Fourier Transform Infrared Spectroscopy), solid‐state ¹³C NMR (Nuclear Magnetic Resonance) and solid‐state ²⁹Si NMR. The AR coatings were characterized by UV–vis (Ultraviolet–Visible Spectroscopy) transmittance spectra, AFM (Atomic Force Microscope), and SEM (Scanning Electron Microscope). The effects of modified silica loading and type of solvent on AR properties were studied. An enhancement in AR activity was observed for 1 wt% PDMS‐modified (low molecular weight) silica coatings and 3 wt.% fluorosilica‐10 in dimethylacetamide (DMAc). In comparison with cyclopentanone (CPT), DMAc favors migration of silica particles toward coating‐air interface giving higher transmittance. The migration of particles to the surface and consequently increased surface roughness was observed by SEM. POLYM. ENG. SCI., 53:2228–2241, 2013. © 2013 Society of Plastics Engineers     

Mechanical properties and structures of dicyanate–clay nanocomposites

Dicyanate–clay nanocomposites comprising a dicyanate resin and a type of organically modified clay were prepared and characterized, and their thermomechanical properties were investigated. The organically modified clay had silicate layers of nanometer size intercalated with an organic modifier, which improved the compatibility between the clay and organic materials, such as dicyanate resins. Dynamic mechanical analysis was performed to investigate the thermomechanical properties of the dicyanate–clay nanocomposites containing various amounts of the clay. The storage modulus of the nanocomposites below their glass‐transition temperatures slightly increased with increasing clay content. The glass‐transition temperature of the dicyanate–clay nanocomposites increased with increasing clay content. The nanostructures of the dicyanate–clay nanocomposites were characterized by transmission electron microscopy and X‐ray diffraction analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2629–2633, 2003     

Block copolymers of acrylonitrile and poly(dimethylsiloxane)s

The chemical redox system of ceric ammonium nitrate(Ce⁴⁺) and poly(dimethylsiloxane)s (PDMS) with monohydroxy (MH), dihydroxy (DH), and diamine(DA) chain ends was used to polymerize acrylonitrile (AN) to produce monohydroxy poly(dimethylsiloxane)s‐b‐polyacrylonitrile (MH.PDMS‐b‐PAN), dihydroxy poly(dimethylsiloxane)s‐b‐polyacrylonitrile (DH.PDMS‐b‐PAN), and α, ω‐diamine poly(dimethylsiloxane)s‐b‐polyacrylonitrile (DA.PDMS‐b‐PAN) block copolymers. The concentration, reaction time, and the type of poly(dimethylsiloxane) affect the yield and the molecular weight of the copolymers. The ratio of AN/ceric salt/PDMS has remarkably affects the properties of formed copolymers. DH.PDMS‐b‐PAN copolymers were also prepared by electroinduced polymerization in the presence of catalytic amount of Ce⁴⁺ in a divided electrochemical cell where Ce³⁺ is readily oxidized into Ce⁴⁺ at the anode. The products were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, DSC, and their surface properties were investigated through contact‐angle measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of polymeric curing agent modified with silazanes on the mechanical properties of silicone rubber

Polymeric curing agent modified with hexamethyldisilazane (PCA‐D), or with hexamethylcyclotrisilazane (PCA‐T), was used to improve the mechanical properties of hydroxyl‐teminated polydimethylsiloxane (PDMS) rubber. The structure and the gel time of PCA were characterized by ²⁹Si NMR and shear viscosity measurement, respectively. The PCA modified with silazanes was more stable in storage than that without treatment (PCA‐0). Chemical bonds were formed during the reaction of silazanes and PCA according to ²⁹Si NMR results. The crosslink density (γ_e) and the mechanical properties of PCA/PDMS rubber were determined by swelling equilibrium and stress–strain tests. It was found that PCA treated with both silazanes could better enhance the mechanical properties of PCA/PDMS rubber compared with PCA‐0. PCA‐T/PDMS rubber, with additional crosslinks, was the best among the three types of PCA/PDMS rubber on the mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of natural and organically modified montmorillonite clays on the properties of polydimethylsiloxane rubber

The effects of natural (MT) and organically modified (O‐MT) montmorillonite clays on the properties of polydimethylsiloxane (PDMS) rubber were evaluated. Rubber composites with different clay contents were prepared by a compounding procedure in an open two‐roll mill, which was followed by a compression‐molding step in which the PDMS matrix was peroxide crosslinked. The clay rubber composites were characterized by swelling measurements in toluene, thermogravimetric analyses, X‐ray diffraction, scanning electron microscopy, and tensile tests. The introduction of MT restricted the solvent swelling and increased the crosslinking density of the rubber, which indicated the formation of a covalent filler–matrix interface. The enhanced interaction between MT and PDMS reduced the aggregation size of MT particles in the MT composites and promoted an increase in the separation of the clay layers. When the rubber was filled with O‐MT, a higher solvent amount was incorporated in the material, and this trend increased with the clay content. Moreover, the low interaction between O‐MT and the PDMS chains resulted in larger clay aggregates in the O‐MT composites compared to those with MT. Despite the different interface natures, both clays enhanced thermal stability and acted as reinforcing fillers in relation to Young's modulus and tensile strength. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of clay on mechanical and gas barrier properties of blown film LDPE/clay nanocomposites

Low density polyethylene (LDPE)/clay nanocomposites, which can be used in packaging industries, were prepared by melt‐mix organoclay with polymer matrix (LDPE) and compatibilizer, polyethylene grafted maleic anhydride (PEMA). The pristine clay was first modified with alkylammonium salt surfactant, before melt‐mixed in twin screw extruder attached to blown‐film set. D‐spacing of clay and thermal behavior of nanocomposites were characterized by Wide‐Angle X‐ray Diffraction (WAXD) and differential scanning calorimetry (DSC), respectively. WAXD pattern confirmed the increase in PEMA contents exhibited better dispersion of clay in nanocomposites. Moreover, DSC was reported the increased PEMA contents caused the decrease in degree of crystallinity. Mechanical properties of blown film specimens were tested in two directions of tensile tests: in transverse tests (TD tests) and in machine direction tests (MD tests). Tensile modulus and tensile strength at yield were improved when clay contents increased because of the reinforcing behavior of clay on both TD and MD tests. Tensile modulus of 7 wt % of clay in nanocomposite was 100% increasing from neat LDPE in TD tests and 17% increasing in MD tests. However, elongation at yield decreased when increased in clay loading. Oxygen permeability tests of LDPE/clay nanocomposites also decreased by 24% as the clay content increased to 7 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of resol‐layered silicate nanocomposites

Resol‐layered silicate nanocomposites were synthesized by intercalative polymerization of phenol and formaldehyde using layered clays such as an aminoacid‐modified montmorillonite (MMT) and a commercial modified MMT (Cloisite 30B). The composites were prepared by a sequential process in which one of the reactives of the phenolic resin was reacted with the organosilicate and subsequently cured with triethylamine. The nanocomposites were studied by means of X‐ray diffraction, atomic force microscopy, and thermogravimetric analysis. Results show a strong clay composition dependence on the intercalation state. The composite of resol with 2 wt % aminoacid‐modified MMT content has the best dispersion of clay layers. Thermal stability of nanocomposites was slightly increased in comparison with the neat resol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Nanocomposites of polypropylene impact copolymer and organoclays: role of compatibilizers

Nanocomposites of polypropylene impact copolymer and organoclays were prepared using different compatibilizers (polypropylene‐graft‐(maleic anhydride) (PPMA), polyethylene‐graft‐(maleic anhydride) (PEMA) and their mixture) and varying percentages of clay (3 and 6%) in an attempt to obtain balanced mechanical properties. The nanocomposites were prepared by melt compounding and test specimens were prepared by injection molding. Mechanical properties such as tensile, flexural and Izod impact strength are reported. The clay dispersion was investigated using wide‐angle X‐ray diffraction while the phase morphology was characterized using scanning electron microscopy. It is shown that the mechanical properties of the system with mixed PPMA and PEMA compatibilizers showed the best balance of mechanical properties among the nanocomposites explored. Copyright © 2006 Society of Chemical Industry     

Thermally resistant carbazole‐modified phenol–formaldehyde resins

Phenol–formaldehyde resins were modified with carbazole in order to improve their thermal resistance. Attempts to incorporate carbazole rings into novolac and resol resins were made using three methods: (1) the addition of N‐(hydroxymethyl)carbazole (HMC) into a phenol–formaldehyde mixture, (2) the addition of carbazole into a phenol–hydroxymethyl derivative of acetone mixture, where the hydroxymethyl derivative of acetone was used as formaldehyde donor, and (3) by prolonging the time of high‐temperature reaction between phenol, carbazole and formaldehyde. The temperature and time of reaction were critical for incorporation of carbazole, which successfully led to highly temperature‐resistant carbazole‐modified novolacs for the latter procedure. When carbazole was incorporated into novolac structure at a level of 8 mol%, the thermal resistance increased by 118 °C measured as 5% mass loss temperature. Other procedures led to solids containing carbazole or HMC as physical admixtures. The obtained composites revealed variable thermal resistance effects; the carbazole‐modified resol containing 9 mol% of carbazole showed 47 °C increase of thermal resistance in comparison with non‐modified resol, measured as 5% mass loss temperature. © 2015 Society of Chemical Industry     

Effects of silane and the lowering of pH on the properties of phenol–formaldehyde resol resins and resin coatings

Phenol–formaldehyde resol resins were modified by the addition of silane (3‐aminopropyltriethoxysilane) and the lowering of pH (formic acid). The effects of the modifications on the properties of the resins during storage were studied through comparison with the parent resins and by viscosity measurements, NMR spectroscopy, ultraviolet–visible spectroscopy, and differential scanning calorimetry. Resin coatings on paper were prepared to determine the influence of discoloration of the resin solution on the color of the cured resin. A decrease in the pH of the NaOH‐catalyzed resin solutions lightened the color of the solutions and corresponding coatings, whereas silane additions made the coatings slightly more yellow. The lowering of pH increased the viscosities and decreased the reactivities of the resin solutions compared with the unmodified reference resins during storage. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1933–1941, 2007     

Synthesis and characterization of vinyl‐polyhedral oligomeric silsesquioxanes‐reinforced silicone resin with three‐dimensional cross‐linking structure

A novel thermal stability and highly transparent silicone resin‐type material was prepared via hydrosilylation of vinyl‐polyhedral oligomeric silsesquioxanes (POSS)‐grafted methylhydrosilicone oil and vinylmethylsilicone oil in the presence of Karstedt catalyst. The morphology, mechanical property, thermal stability, optical transmittance, thermal‐oxidation resistance of the vinyl‐POSS‐reinforced silicone resins were systematically investigated. Scanning electron microscopy showed that the vinyl‐POSS‐reinforced silicone resins had good compatibility with polydimethylsiloxane (PDMS) systems. The mechanical analysis and thermo gravimetric analysis indicated that the mechanical properties and thermal stability increased with increasing quantity of vinyl‐POSS. However, the optical transmittance increased with the increasing amount of vinyl‐POSS rather than decreased. In addition, the incorporation of vinyl‐POSS did not improve the thermal resistance of the PDMS polymers. The product has the potential application for LED packaging. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42187.     

Studies on fly‐ash‐filled natural rubber modified with cardanol derivatives: Processability,mechanical properties,fracture morphology,and thermal decomposition characteristics

Fly ash, a by‐product of thermal power stations, was used as a filler in natural rubber (NR) in presence of 5–10 phr of phosphorylated cardanol prepolymer (PCP) and hexamethylene tetramine cured PCP (PCPHM). The compositions modified with the cardanol‐based resins showed lower power consumption for mixing, lower cure time, improved tensile properties and tear strength, and higher thermal stability. Scanning electron microscopy of the fracture surfaces of the tensile‐failed specimens showed finer and more uniformly distributed filler particles in the rubber matrix in the presence of PCP/PCPHM. The cardanol‐based resins are expected to function as a coupling agent between the filler and rubber leading to the improvement in mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4801–4808, 2006     

Curing behavior study of polydimethylsiloxane‐modified allylated novolac/4,4′‐bismaleimidodiphenylmethane resin

The curing behavior of polydimethylsiloxane‐modified allylated novolac/4,4′‐bismaleimidodiphenylmethane resin (PDMS‐modified AN/BDM) was investigated by using Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry. The results of FTIR confirmed that the curing reactions of the PDMS‐modified AN/BDM resins, including “Ene” reaction and Diels–Alder reaction between allyl groups and maleimide groups, should be similar to those of the parent allylated novolac/4,4′‐bismaleimidodiphenylmethane (AN/BDM) resin. The results of dynamic DSC showed that the total curing enthalpy of the PDMS‐modified AN/BDM resins was lower than that of the parent resin. Incorporation of polydimethylsiloxane (PDMS) into the backbone of the allylated novolac (AN) resin favored the Claisen rearrangement reaction of allyl groups. The isothermal DSC method was used to study the kinetics of the curing process. The experimental data for the parent AN/BDM resin and the PDMS‐modified AN/BDM resins exhibited an nth‐order behavior. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical properties,thermal stability,and flame retardance of novolac‐type phenolic resin blended with poly(dimethylsiloxaneadipamide)

Mechanical properties (flexural strength, flexural modulus, and notched Izod impact strength), thermal stability, and flame retardance of poly(dimethylsiloxane adipamide) (PDMSA)‐toughened novolac type phenolic resin were investigated. Mechanical properties of modified novolac‐type phenolic resin increase with PDMSA contents, because the soft segment of PDMSA absorbs the loads in the network of brittle novolac‐type phenolic resins. TGA results show that the thermal degradation temperatures are higher than 400°C, and the temperature of 10% weight loss increases with increasing the PDMSA content. The char yield increases with novolac‐type phenolic resin content. The morphologies of the fracture surface of the modified novolac‐type phenolic resin were investigated by scanning electron microscopy (SEM). Morphological results agree with those from mechanical properties of the modified novolac‐type phenolic resin. The modified novolac‐type phenolic resin also shows excellent flame retardance that is UL‐94, V‐1, and the limited oxygen index is higher than 35. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 631–637, 2001     

Mechanical performance of resol type phenolic resin/layered silicate nanocomposites

Clay addition has been shown to affect polymer resins positively in terms of several physical and chemical properties, including mechanical performance, high temperature endurance and durability. These increases are limited only to relatively low concentrations of reinforcement phase, but at these low concentrations polymer/layered silicate nanocomposites (P/LS NC) have shown to exhibit higher mechanical performance than fiber reinforced polymer composites. This is among the several reasons that make P/LS NC's one of the most widely studied class of materials today. In this study, the mechanical performance of resol type phenolic resin/layered silicate nanocomposite specimens was examined by carrying out 3‐point bending, Charpy impact and fracture toughness tests to couple the observations, microstructural analysis is done through X‐ray diffraction and scanning electron microscopy. The effects of especially three factors; cure method, clay amount, and clay modification were investigated. It was concluded that highest mechanical performance was obtained by the acid curing of the phenolic resin with very low amounts (e.g., 0.5%) of either very hydrophobic or very hydrophilic Na‐montmorillonite clay additions. Improvements as high as 7% in flexural strength, 11% in flexural strain at break, 16% in Charpy impact strength, and 66% in fracture toughness values were obtained. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers