Phenol–formaldehyde resins modified by copper nanoparticles

Abstract

Phenol–formaldehyde (PF) resins modified by copper nanoparticles were synthesised by in situ polymerisation process. X-ray diffraction (XRD), transmission electron microscopy (TEM) revealed that nanosized copper particles were well dispersed in the resulting PF resins. The thermal properties of the prepared PF resins were investigated by thermogravimetric analysis (TGA). It was indicated that copper nanoparticles remarkably improved the thermal stability of the PF resins at lower temperature. However, the copper nanoparticles increased the rate of the degradation of the PF resins at the elevated temperature. The toughness and the tribological properties of the friction materials based on the prepared PF resins were also studied. The results showed that copper nanoparticles obviously improved the brittleness and the tribological performances of the friction materials.     

Phenolic Resins Modified by Nanocopper Particles and their Service Performances

This article reports on the synthesis of phenol-formaldehyde (PF) resins, as modified by nanocopper particles, through the in situ polymerization process. XRD and TEM analysis revealed that nanocopper particles were well dispersed in the resulting PF resins. The thermal properties of the prepared PF resins were investigated by thermogravimetric analysis (TGA). The results indicated that nanocopper particles caused a remarkable improvement in the thermal stability of the PF resins at lower temperatures. The toughness and the tribological properties of the friction materials based on the prepared PF resins were also studied. The results showed that nanocopper particles substantially improved the brittleness and the tribological performances of the friction materials.     

Synthesis and properties of nano carboxylic acrylonitrile butadiene rubber latex toughened phenolic resin

Nano carboxylic acrylonitrile butadiene rubber latex‐toughened‐phenolic resins (XNBRL‐PF) were prepared by in situ polymerization in this work. The influence of nano XNBRL on the microstructure and physical properties of modified PF resin was investigated. Impact test testified that the impact strength of XNBRL‐PF was remarkably improved compared to pure PF and as the content of XNBRL increased to 10 wt %, the impact strength of the XNBRL‐PF kept increasing. Scanning electron microscope analysis of the fracture surface of the XNBRL‐PF indicated that the XNBRL were uniformly dispersed in the PF matrix, with diameters ranging from 200 to 400 nm. The results of Fourier transform infrared spectroscopy proved that chemical reaction occurred between XNBRL and PF matrix, which can greatly improve the interface interaction between rubber particles and PF matrix. Thermogravimetric analysis test showed that the incorporation of XNBRL can improve the thermostability of PF at low temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

有机硅改性松香基环氧树脂的制备及阻燃性能

制备了聚甲基苯基硅氧烷（PMPS）改性松香基乙二醇二缩水甘油醚AR-EGDE。红外光谱(IR)、核磁共振（¹³C NMR）和环氧值测试结果表明有机硅成功接枝至环氧树脂。同时,将PMPS与AR-EGDE充分混合得到物理改性树脂。通过力学性能和极限氧指数测试探讨了改性方法对改性树脂力学及阻燃性能的影响：化学改性优于物理改性及未改性的AR-EGDE。热失重、炭层分析表明,PMPS改性的树脂在受热和燃烧过程中,都能形成含硅炭层,该炭层可延缓内部材料热分解,同时阻止可燃裂解气体的释放和熔滴发生,从而提高材料的耐热和阻燃性能。物理改性松香基环氧,燃烧时无法形成有效富硅炭层覆盖于底部材料,从而使其阻燃性劣于化学改性。     

Studies on modified phenolic resin. Iv: Properties of phenolic resin modified with 4-hydroxyphenyl- maleimide/n-butylacrylate copolymers

Three 4-hydroxyphenylmaleimide/ n-butylacrylate (HPMI/n-BuA) copolymers with different monomer ratios were synthesized. Their average molecular weights, glass transition temperatures (T,_g), and thermal decomposition temperatures were measured. It was found that these copolymers had higher average molecular weights and higher thermal decomposition temperatures than novolac. Modified phenolic resins were prepared by transfer moulding from moulding compounds consisting of novolac, the copolymer, hexamethylenetetramine (hexamine), and glass fibre. Properties of the three kinds of modified phenolic resins were examined by flexural test, impact test, dynamic thermomechanometry, and observation of morphology. It was found that phenolic resin modified with HPMI/ n-BuA (1/3-6) copolymer and modified with HPMI/n-BuA (1/7-0) copolymer showed good toughness and good heat resistance. It was also found that the heat resistance of modified phenolic resins was improved by after-cure, but the mechanical properties were decreased by after-cure: similar behaviour was observed for unmodified phenolic resin.     

Modification of cyanate ester resin by poly(ethylene phthalate) and related copolyesters

Aromatic polyesters were prepared and used to improve the brittleness of the cyanate ester resin. The aromatic polyesters include poly(ethylene phthalate) (PEP) and poly(ethylene phthalate‐co‐1,4‐phenylene phthalate). The polyesters were effective modifiers for improving the brittleness of the cyanate ester resin. For example, inclusion of 20 wt % PEP (MW 19,800) led to a 120% increase in the fracture toughness (K_IC) with retention in flexural properties and a slight loss of the glass transition temperature compared to the mechanical and thermal properties of the unmodified cured cyanate ester resin. The microstructures of the modified resins were examined by scanning electron microscopy and dynamic viscoelastic analysis. The thermal stability of the modified resins was lower than that of the unmodified resin as determined by thermogravimetric analysis. The water absorptivity of the modified resin increased significantly, compared to that of the unmodified cured cyanate ester resin. The toughening mechanism was discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified cyanate ester resin system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 208–219, 2000     

Bark extractives-based phenol–formaldehyde resins from beetle-infested lodgepole pine

In this study, phenol–formaldehyde (PF) resins derived from the bark extractives were synthesized and characterized. Bark of lodgepole pine (Pinus contorta Dougl.) infested by mountain pine beetle (Dendroctonus ponderosae Hopkins) was first extracted with 1% NaOH. The bark extractives with and without acid-neutralization were then dried to the solid state. The neutralized and non-neutralized extractives were used to partially replace petroleum-based phenol for synthesizing the bark extractives-PF resins. In comparison with a commercial PF resin and a laboratory made PF resin (Lab PF), the bark extractive-PF resins were found to have higher molecular weights, higher viscosities, and shorter gel times. Acid neutralization of the bark extractives increased the molecular weight of the extractives and modified the performance and curing behavior of the resulting bark extractive-PF resins. Bark extractive-PF resins (BEPF) showed a similar level of post-cured thermal stability to that of the lab PF at higher temperatures, but they differed significantly from that of the commercial PF resin. The bark extractive-PF resins made from both neutralized and non-neutralized extractives at 30% replacement of phenol (by weight) exhibited similar dry and wet bond strengths to the commercial PF resin. At 50% substitution level, BEPF had dry and wet bond strengths similar to the lab PF resin. Our findings suggest that alkaline extractives from mountain pine beetle-infested lodgepole pine bark are suitable for partially substituting phenol in the synthesis of phenolic resin for use in wood adhesives.     

Properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde resin

The aim of this research was to investigate the physical and mechanical properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde (LPF) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid, and then, various contents of modified lignins (10, 15, and 20 wt%) were added as a substitute of phenol in phenol–formaldehyde (PF) resin synthesis. The properties of the synthesized resin were compared with those of a control PF resin. The changes in curing behavior of the resins prepared were analyzed by differential scanning calorimetry (DSC). The physical properties of the resins prepared, as well as the water absorption, thickness swelling, shear strength, and formaldehyde emission of the plywood panels bonded with these adhesives, were measured according to standard methods. DSC analysis indicated that in comparison with PF resins, curing of the LPF resin occurred at lower temperatures. The physical properties of the synthesized resins indicated that viscosity and solid content increased, while gel time and density decreased by addition of treated lignin to the PF resin. Although the panels containing resins with modified lignin yielded low formaldehyde emission, their dimensional stability was worse than those bonded with a commercial PF adhesive. The plywood prepared using IL-treated lignin PF resins has shear strength, which satisfy the requirements of the relevant standards specifications and significantly better than that of panels prepared with the control PF resin. The mechanical properties of the panels could be significantly enhanced with increased percentage of treated lignin content from 0 to 20 wt%.     

Effect of nanowhisker-modified zeolites on mechanical and thermal properties of poly(vinyl acetate) composites with pure-silica MFI

The effect of nanoscale surface morphology of pure-silica MFI zeolite on the interfacial, mechanical, and thermal properties of pure-silica MFI zeolite/poly(vinyl acetate) (PVAc) composites was investigated under different annealing conditions. Mg(OH)₂ inorganic whisker- or asperity-like nanostructures were achieved on MFI nano- and micro-particle surfaces via Grignard or solvothermal treatment. The creation of nano-roughness on the MFI surface promoted compatibility between the zeolite and the polymer matrix, resulting in void-free interfaces. PVAc composites containing surface-modified particles showed increased tensile strength and elongation at break as compared with composites containing unmodified zeolite. Surface modification of the microparticles exhibited interfacial and mechanical enhancement over a wider range of annealing temperatures than nanoparticles. Differential scanning calorimetry revealed that surface treatment of MFI resulted in broader glass transitions compared to composites containing unmodified MFI. This is explained by improved interfacial adhesion and associated slower chain relaxation dynamics. Furthermore, X-ray diffraction demonstrated that enhanced adhesive interactions between the PVAc and the MFI surface are associated with surface-induced orientation of the MFI particles within the polymer matrix. The optimal surface morphology, associated with the most enhanced mechanical and thermal properties of composites, was produced with the solvothermal method.     

Preparation and properties of epoxy/phenol formaldehyde novolac/hexakis(methoxymethyl)melamine hybrid resins from in situ polymerization

Based on the self‐condensation of hexakis(methoxymethyl)melamine (HMMM), the condensation between HMMM and phenol formaldehyde novolac resin (n‐PF), and the addition reaction of diglycidyl ether of biphenyl A (DGEBA) and n‐PF, a homogeneous, transparent hybrid thermoset was prepared via in situ polymerization of DGEBA, n‐PF, and HMMM. No phase separations were observed even for the DGEBA/n‐PF/HMMM hybrid thermoset containing 40 wt % HMMM. These hybrid thermosets had high glass‐transition temperatures (98–127°C from differential scanning calorimetry and 111–138°C from dynamic mechanical analysis), excellent thermal stability with high 5 wt % decomposition temperatures (>322°C), high char yields (>24 wt %), and improved flame retardancy with high limited oxygen indices (>28.5). The excellent overall properties of these hybrid resins may lead to their applications in high‐performance “green” electronic products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Viscoelastic characteristics of chain extended/branched and linear polyethylene terephthalate resins

Two chemically modified chain extended/branched polyethylene terephthalate (PET) resins and one unmodified resin, considered to be linear, were characterized in terms of their melt flow, die swell, and viscoelastic properties. The three resins had reportedly similar nominal intrinsic viscosities but exhibited different viscoelastic behavior. The modified resins had lower melt flow index, higher die swell, higher complex viscosity and higher storage modulus than the unmodified one. The Cole–Cole plots of the resins were independent of temperature, and the data for modified resins formed a group that lay below the data group for the unmodified PET. The distribution of relaxation times was determined. The modified resins had higher relaxation strength, G_i, especially at high relaxation times, λ_i. The mean relaxation times of the chain extended/branched resins were approximately an order of magnitude higher than that of the unmodified resin, implying pronounced elastic character. The modified resins had better foaming characteristics in extrusion foam processing than the unmodified one owing to their elastic nature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1371–1377, 2000     

Mechanical,thermal, and morphological properties of bismaleimide/unsaturated polyester copolymers

An unsaturated polyester (UP) resin was modified by the addition of a thermosetting bismaleimide (BMD) as a second coreactive monomer. The copolymers were characterized in terms of mechanical, thermal, and morphological properties by tensile, bend, and impact testing; thermogravimetric analysis; heat deforming temperature analysis; dynamic mechanical analysis; and scanning electron microscopy. In addition, Fourier transform infrared spectroscopy of modified resin indicated that crosslinking networks were formed between BMD and UP. The properties of the modified resins were compared with those of unmodified resins. The results indicate that the addition of BMD not only improved the thermal decomposition temperature and heat deforming temperature but also caused small changes in the mechanical properties. The effect of the construct of BMD and the reactions among BMD, UP, and styrene were analyzed. The results show that BMD has great potential to improve the properties of UP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 593–598, 2006     

Study of jute fiber reinforced polyester composites by dynamic mechanical analysis

Cyanoethylation of jute fibers in the form of nonwoven fabric was studied, and these chemically modified fibers were used to make jute–polyester composites. The dynamic mechanical thermal properties of unsaturated polyester resin (cured) and composites of unmodified and chemically modified jute–polyester were studied by using a dynamic mechanical analyzer over a wide temperature range. The data suggest that the storage modulus and thermal transition temperature of the composites increased enormously due to cyanoethylation of fiber. An increase of the storage modulus of composites, prepared from chemically modified fiber, indicates its higher stiffness as compared to a composite prepared from unmodified fiber. It is also observed that incorporation of jute fiber (both unmodified and modified) with the unsaturated resin reduced the tan δ peak height remarkably. Composites prepared from cyanoethylated jute show better creep resistance at comparatively lower temperatures. On the contrary, a reversed phenomenon is observed at higher temperatures (120°C and above). Scanning electron micrographs of tensile fracture surfaces of unmodified and modified jute–polyester composites clearly demonstrate better fiber–matrix bonding in the case of the latter. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1505–1513, 1999     

Synthesis of silicone–acrylic resins and their applications to superweatherable coatings

Silicone–acrylic resins were synthesized to prepare superweatherable paints for building materials. The raw materials used were n‐butyl acrylate, methyl methacrylate, and n‐butyl methacrylate as acrylic monomers and 3‐methacryloxypropyltrimethoxysilane (MPTS) as a silicone monomer reactive with the acrylic monomers. Acrylic copolymers were synthesized such that their glass‐transition temperatures were adjusted to 30°C and their MPTS contents were varied to 10, 20, and 30 wt %. As the content of silicone and MPTS increased, average molecular weight and viscosity increased, and thermal stability at high temperatures improved. When we tested the properties of coatings by blending the synthesized silicone–acrylic resins with a white pigment, adhesion was superior with various substrates, and their properties were suitable on the whole. Weatherability was tested by an outdoor exposure test with a weather‐ometer and an accelerated weathering tester, and their results showed that silicone–acrylic resin composed of 30 wt % MPTS was a superweatherable coating. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1614–1623, 2001     

Influence of in situ‐generated silica nanoparticles on EPDM morphology,thermal, thermomechanical,and mechanical properties

Silica nanoparticles were synthesized by means of a sol–gel method and generated in ethylene propylene diene monomer rubber (EPDM) by in situ synthesis. The properties were determined using scanning electron microscopy, attenuated total reflectance Fourier‐transform infrared spectroscopy, thermogravimetric analysis, tensile testing, dynamic mechanical analysis, swelling tests, and gel content determination. The silica particles were homogenously dispersed in the EPDM matrix, with the presence of agglomerates, especially for high silica contents. The swelling experiments showed a decrease in the crosslinking density of the vulcanized rubber due to the presence of the silica nanoparticles. The mechanical properties, however, were significantly improved by the presence of the stiff silica nanoparticles. The effect of the amount of silica on the thermomechanical properties and thermal degradation of EPDM was also investigated. The presence of silica showed an increase in the storage and loss moduli at high temperatures, probably due to the increasing filler content. The thermal degradation analysis showed that the presence of silica particles incorporated in the EPDM matrix had no significant influence on the thermal stability of the composites. POLYM. COMPOS., 36:825–833, 2015. © 2014 Society of Plastics Engineers     

Synthesis and physicochemical investigation of imide-functionalized silica nanocomposites

The incorporation of inorganic nanoparticles into polymers have gained significant attention to improving functional properties. The ultimate nanocomposite behaviors are influenced by many parameters, such as microstructural distribution that are produced during the treatment process. Herein, a hybrid material integrating a modified network into a polyimide PI matrix was produced via the sol–gel method by the reaction of pyromellitic dianhydride, 4, 4-oxydianaline, and 1, 5-diaminonaphthalene to synthesize copolyimides nanocomposite. The modified polyimide and unmodified polyimide silica (SiO₂) nanoparticles were incorporated in the polyimide matrix to have polyimide silica nanocomposite. In modified silica nanoparticles, 3-aminopropyltriethosilane was introduced to have better compatibility among inorganic–organic hybrid with similar chemical contact due to their flexible alkyl group. The surface morphology or structure of silica and polyimide was affirmed by scanning electron microscopy, Fourier transforms infrared spectroscopy confirmed the synthesis of pure polyimide, unmodified polyimide, and modified polyimide silica via presence and absence of certain peaks. Thermogravimetric analysis (TGA) results showed high thermal stability of nanocomposites as silica content increases. In contrast to unmodified silica, the modified silica provides more thermal stability to the nanocomposites. Dynamic mechanical analysis was used to investigate the tensile stress of pure polyimide, unmodified, and modified silica nanocomposites. Thermal stability, storage modulus, and moisture absorption of these hybrid materials were improved with silica nanoparticles. The TG mass spectrum confirms the successful synthesis of modified silica networks. The substituted silica nanoparticles show higher mechanical toughness and storage in modified compared to unmodified silica nanocomposite, which exhibits stronger binding attraction between silica nanoparticles and polyimide matrix.     

Silica nanoparticles modified with vinyltriethoxysilane and their copolymerization with N,N′‐bismaleimide‐4,4′‐diphenylmethane

The synthesis and characterization of the vinyltriethoxysilane‐modified silica nanoparticles were investigated. It was shown that the vinyltriethoxysilane molecules had been successfully grafted onto the silica nanoparticles. The native and silane‐modified silica dispersions in N‐methyl‐2‐pyrrolidone with the total solids contents within the range 1–6 wt % exhibited dramatically different flow behaviors. The polymerization of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) initiated by barbituric acid in the presence of the native or vinyltriethoxysilane‐modified silica nanoparticles were then carried out in γ‐butyrolactone (total solids content = 20%). The higher the level of silica, the better the thermal stability of the BMI/silane/silica composite particles. The silane‐modified silica particles significantly improved their dispersion capability within the continuous BMI oligomer matrix. Furthermore, the degree of dispersion of the vinyltriethoxysilane‐modified silica particles in the BMI oligomer matrix decreased with the weight percentage of silica based on total solids increased from 20 to 40 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: Sci 103: 3600–3608, 2007     

Preparation and properties of a novel flame retardant polyurethane quasi‐prepolymer for toughening phenolic foam

A novel phosphorus‐ and nitrogen‐containing polyurethane quasi‐prepolymer (PNPUQP) was synthesized and incorporated into phenolic foam (PF) in different ratios in order to improve the toughness. The structure of PNPUQP was confirmed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The effects of PNPUQP on the flame retardant properties, thermal stability and mechanical properties of modified PF were investigated. The results suggested that the addition of 3 wt % PNPUQP increased the toughness of PF and improved the flame retardancy. The investigation on the morphology of PF and modified PF by scanning electron microscope (SEM) certified the good toughness of the PNPUQP on PF. Additionally, the thermal properties of the foams were investigated by thermogravimetric analysis (TGA) under N₂ atmosphere. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42424.     

In situ generation of the surface‐modified silica nanoparticles within the silicone matrix

In this study, silica nanoparticles were generated and simultaneously modified inside the silicone resin. Intensive dispersion of the filler and prevention of the cure inhibition effect associated with the regular and unmodified silica particles as well as providing the conditions for grafting to the resin chains were targeted in this work. The dimensions of the nanoparticles, surface morphology, and cure property of the composites were investigated by transmission electron microscopy and differential scanning calorimetry and optimized. Surface chemistry of the modified nanoparticles was investigated by Fourier transform infrared spectroscopy and water contact angle measurement. The effect of in situ synthesis/modification of the silica nanoparticles on mechanical characteristics of the obtained nanocomposites were also examined mainly by tensile properties. POLYM. COMPOS., 36:1365–1370, 2015. © 2014 Society of Plastics Engineers     

Effect of resin type and content on properties of composite particleboard made of a mixture of wood and rice husk

This study investigated the effect of resin type and content on the dimensional stability and mechanical properties of single-layer composite particleboards made of a mixture of wood particles (70 wt%) and rice husk particles (30 wt%). Two types of resin, urea–formaldehyde (UF) resin and phenol–formaldehyde (PF) resin, were used in the experiments at three different contents which were 8, 10, or 12 wt%. The dimensional stability of the samples was significantly improved by increasing the resin content. When the contents of the UF and PF resins increased from 8 to 12 wt%, the WA values of the samples decreased to18% and 33%, respectively. Similar results were also observed for the TS values. The UF resin bonded samples swelled two times more than the PF resin bonded particleboard. The mechanical properties of the PF resin bonded samples were better than the UF resin bonded samples. When the contents of the UF and PF resins increased from 8% to 12 wt%, the internal bond strength values of the samples increased to 21% and 41%, respectively. The bending strength and modulus of elasticity of the samples were not significantly increased by increasing contents of the UF and PF resins, except for the 12 wt% content.