Novolac Resin Research Articles

One-pot synthesis of organo-silica hybrids with high thermal properties via a simple sol–gel process

Organic–inorganic hybrid composites have received much attention of scientists in the recent years due to the notable improvement of thermal properties without using of organic or inorganic nanoparticles. Hence, we have developed a facile strategy to prepare a 3D hybrid network based on silane materials and novolac resin via sol–gel process. At first step, novolac resin was prepared by general procedure with appropriate thermal properties and then modified with (3-chloropropyl)triethoxysilane (CPTES) to form MNR. In second step, to cure MNR and prepare hybrid composite structures, general amine-cured system and sol–gel process were applied to prepare MNH and MNSG samples, respectively. XRD analysis was used to support the formation of silane networks in hybrid samples. Investigation of thermal properties by DSC and TGA showed that cured samples had much higher thermal stability and char yield with respect to novolac and modified resin (MNR) originated from formation of 3D Si–O–Si network. Presented method limited some disadvantages of using nanoparticles such as aggregation and poor distribution. Such hybrid composites with high thermal stability have potential applications in advanced fields such industrial molds, coatings, adhesives and composites.

The effect of free dihydroxydiphenylmethanes on the thermal stability of novolac resin

Phenolic resins (PRs) play an important role in aerospace due to their low cost, outstanding chemical resistance, mechanical properties, thermal properties and ablative properties. However, the industrially produced PRs are often mixtures of polyphenolic compounds with different structures and molecular weights, among which the low molecular weight components are detrimental to the properties of PRs, especially the thermal stability. In this paper, the dihydroxydiphenylmethane (DHDM) contents in several typical industrial novolac resins (NRs) were measured by liquid chromatography and gel permeation chromatography, and the effect of DHDM content on the viscosity, curing process, glass transition temperature (Tg) and thermal stability of NRs was investigated. The results showed that a significant reduction in viscosity and Tg was observed for the NRs with higher DHDM content. The existence of DHDMs reduced the gel point and crosslinking density of the cured NRs by hexamethylenetetramine, leading to a significant decrease in the 5% weight loss temperature, the maximum weight loss temperature, as well as the char yield at 800 °C. Therefore, in addition to the free phenols, we should pay more attention to the DHDMs existed in the NRs. This study provides an important insight for NR manufacturers that the DHDM contents should be reduced through the proper control of process parameters to further expand their wider application scope.

Preparation of waterborne epoxy dispersion and its application in 2K waterborne epoxy coatings

Waterborne epoxy dispersions have excellent permeability and adhesion to various polar substrates and they are widely used as coatings and adhesives in industrial applications. Herein we present experimental schemes of a reactive emulsifier and three waterborne epoxy dispersions prepared for waterborne epoxy coatings. First, the epoxy groups in polyethylene glycol diglycidyl ether (PEGDGE) and epoxy resin E20 are ring-opened with amino hydrogen in ethanolamine, followed by neutralizing with glacial acetic acid (HAc) to obtain an emulsifier for emulsifying epoxy resins. Then two bisphenol A epoxy resins E20, E51 and a novolac epoxy resin NPPN631 are employed as emulsified oil phase to prepare waterborne epoxy dispersions with the above emulsifier. And finally the as-prepared waterborne epoxy dispersions are applied in 2K waterborne epoxy coatings. The results indicate that when the molar ratio of PEGDGE with an epoxy equivalent of 109 g▪mol−1 and epoxy resin E20 is 2:1, the synthesized emulsifier possesses the optimal emulsifying ability for epoxy resin, with the Krafft point of 56°C, and the HLB of 16. The coating films from 2K waterborne epoxy coatings occupy excellent wear resistance, thermal stability, hardness and mechanical properties. By exploring the curing mechanism, the superior performances of the coatings film prepared by waterborne epoxy dispersion and waterborne epoxy curing agent are presented.

Reduction of negative environmental impact of mechanisms by improving tribotechnical indicators of sealing materials

In order to eliminate the negative environmental impact of transport and mechanisms operating under high speeds and loads, high abrasion wear, composite materials for sealing devices, thrust bearings, Goodrich stern bearings have been developed by the interaction of nitrile butadiene rubber with novolac resin, cured with dinitrile. The physico-mechanical and tribotechnical data of laboratory and production tests of the developed composites are shown.

Modified Materials Based on SKN-40 Butadien-Nitril Rubber

Identified in work dependency allow to predict the flammability properties, rate of coke combustion and height butadiene-nitrile rubberswith BS-120 white carbon additives and novolac phenol-formaldehyde SF010A resins.

Micro‐Phase Separation within Epoxy Resin Yields Ultrathin Mesoporous Membranes with Increased Scalability by Conversion from Spin‐ to Dip‐Coating Process

AbstractUltrathin mesoporous membranes offer highly desirable characteristics for separation tasks regarding selectivity and mass transport of proteins. They have potential applications as separation devices in microfluidics, diagnostics, sensing, and high‐precision separations for pharmaceutical formulation. Especially for large‐scale and mass production, sophisticated production processes represent a barrier for wider application. A method is developed to produce nanomembranes with a thickness of 75 nm and 40 nm pores with an epoxy resin. The novolac resin is cured with branched polyethylenimine to form a covalently crosslinked polymer membrane with perforations spanning the entire thickness. Pore formation relies on micro‐phase separation of the curing agent during casting and the selective dissolution of the emergent nanodomains which thereby serve as pore templates. The resulting membranes are hydrophilic and therefore suitable for applications with biological fluids. Mechanical testing of the flexible but robust thin films reveals an ultimate tensile strength of 15 MPa and a biaxial modulus of 0.8 GPa. Proteins with a diameter of less than 12 nm can diffuse through the pores and permeation rates are pH dependent. The entire fabrication process is transferred to a dip‐coating approach, which is more suitable for a potential large‐scale production.

Chemical incorporation of epoxy-modified graphene oxide into epoxy/novolac matrix for the improvement of thermal characteristics

Chemical incorporation of epoxy-modified graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-modified GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modified GO to the resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, and Raman spectroscopy were used for approving modification of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modification with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modified GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modified GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modified GO.

Health Risk Assessment of Photoresists Used in an Optoelectronic Semiconductor Factory.

Photoresist materials are indispensable in photolithography, a process used in semiconductor fabrication. The work process and potential hazards in semiconductor production have raised concerns as to adverse health effects. We therefore performed a health risk assessment of occupational exposure to positive photoresists in a single optoelectronic semiconductor factory in Taiwan. Positive photoresists are widely used in the optoelectronic semiconductor industry for photolithography. Occupational exposure was estimated using the Stoffenmanager® model. Bayesian modeling incorporated available personal air sampling data. We examined the composition and by-products of the photoresists according to descriptions published in the literature and patents; the main compositions assessed were propylene glycol methyl ether acetate (PGMEA), novolac resin, photoactive compound, phenol, cresol, benzene, toluene, and xylene. Reference concentrations for each compound were reassessed and updated if necessary. Calculated hazard quotients were greater than 1 for benzene, phenol, xylene, and PGMEA, indicating that they have the potential for exposures that exceed reference levels. The information from our health risk assessment suggests that benzene and phenol have a higher level of risk than is currently acknowledged. Undertaking our form of risk assessment in the workplace design phase could identify compounds of major concern, allow for the early implementation of control measures and monitoring strategies, and thereby reduce the level of exposure to health risks that workers face throughout their career.

تحضيرودراسة تحليلية للبولي يوريثان المحضر من ( راتنج الريسول نوفولاك – بولي اثيلين كلايكول ) المشترك

Resol novolac resin was prepared by condensation of novolac resin with formalin solution in the presence of sodium hydroxide as catalyst, then new copolymer were prepared by reaction of this resin with polyethylene glycol. This new copolymer was supported on polyurethane foam as solid phase and applied to separation a mixture of Cr(III) and Cd(II) ions from aqueous solutions prior to the determination by flame atomic absorbtion spectrometry. The optimum conditions of some parameters effect on recovery of the ions such as acidity, eluent condition, shaking time, and eluent flow rate were investigated. At pH 4,5, the maximum recovery (90%) of Cd(II) by stripping with 40 ml of (1N) nitric acid ,while for Cu (11) was 80 % with 50 mL of (2N) nitric acid .On the other hand thermal stability for the prepared polyurethane was evaluated by TGA.

Influence of Initial Fibre Length and Content Used in the Injection Moulding of CFRP on the Properties of C/C and C/C-SiC Composites

The production of C/C-SiC composites comprises a three-stage process: forming (CFRP-composite), pyrolysis (C/C-composite) and liquid silicon infiltration (C/C-SiC). A new promising approach for the manufacturing of CFRP intermediate composites is the injection moulding of customised granulates (novolac resin, hardener, processing additives and short carbon fibre) produced by compounding technique. To date, a direct dosing of short carbon fibre into the compounder was technically not realisable due to fibre separation and electrostatic charging in the hopper. A possible substitute solution has been the direct feeding of a carbon fibre bundle from a roving into the compounder. However, this is associated with a severe damage of the fibres and an inaccurate adjustment of the fibres content. In the present article, new chopped carbon fibres provided with an adapted sizing to be directly dosed into the compounder are used. The fibres possess a predefined length of 3 and 6 mm and their content amounts to 50 and 58 wt.%. The influence of the initial fibre length and fibre content on the physical and mechanical properties of the resulting CFRP-, C/C-and C/C-SiC-composites is presented and discussed. In addition, the impact of fibre feeding procedure at the compounding stage on the microstructure is considered

Evaluation of DOPO and Nano-Silica Modified Epoxy Resin Systems as Low Viscous, Flame Retardant Additives for Infusion and Injection Processing of Carbon Fiber Reinforced Plastics

In the present study, a low viscous (complex viscosity between 200 to 500 mPas at 60 °C), flame retardant epoxy resin formulation is prepared and transferred to the carbon fiber reinforced plastic (CFRP) laminate using resin transfer molding (RTM) method. For the laminate production, a 12k carbon fiber fabric with an areal weight of 400 g/m2 is used to achieve a fiber volume content of approximately 60 vol % carbon fibers. Subsequently the unmodified laminate is produced, varying carbon fiber volume content to study its effect on flame retardant properties. As additives, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) modified epoxy resin and nanosilica particles delivered in an epoxy novolac masterbatch are added to the neat novolac resin system. The mixture is cured with isophorone diamine (IPDA) and polyetheramine hardener blend, resulting in a glass transition temperature of 104 °C for the unmodified laminate. Flame retardant properties of the materials are tested using cone calorimeter and thermal gravimetrical analysis. In addition, the mechanical behavior of the systems is evaluated via three-point bending method in static and dynamical loadings. In order to get deeper information on the resulting flame retardant mechanisms of the additives, the residual cone calorimeter char is analyzed with scanning electron microscopy, indicating the different flame retardant mechanisms of phosphorous and silica as well as the combination of both additives.

Investigation on the Flame Retardant Properties and Fracture Toughness of DOPO and Nano-SiO2 Modified Epoxy Novolac Resin and Evaluation of Its Combinational Effects.

In this study, the flame-retardant, thermal and mechanical properties of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and nano-SiO2 modified epoxy novolac resin is evaluated, and the combinational effects of both additives are verified. As a hardener, an isophorone diamine (IPDA) and polyetheramine blend is stoichiometrically added to obtain a low viscous epoxy resin system, suitable for resin injection and infusion techniques. The glass transition temperature (Tg) and the silica dispersion quality is affected by the DOPO modification and the nano silica particles. The flame-retardant (FR) and mechanical properties of the additives are investigated separately. The fracture toughness could be increased with the incorporation of both FR additives; however, the effect is deteriorated for higher DOPO amount which is referred to silica particle agglomeration and consequently reduced shear yielding mechanism. Flame-retardant properties, especially the peak heat release rate (pHRR) and the total heat release (THR) could be decreased from 1373.0 kW/m2 of neat novolac to 646.6 kW/m2 measured by resins with varying phosphorous and silica content. Thermogravimetric analysis (TGA) measurements show the formation of a high temperature stable char layer above 800 °C which is attributed to both additives. Scanning electron microscopy (SEM) images are taken to get deeper information of the flame-retardant mechanism, showing a dense and stable char layer for a certain DOPO silica mixture which restrains the combustible gases from the burning zone in the cone calorimeter test and influences the fire behavior of the epoxy resin.

Synthesis of Cardanol-Based Novolac Resin from Cashew Nut Shell Liquid

Synthesis of Cardanol-Based Novolac Resin from Cashew Nut Shell Liquid

Finite Element Simulation of Indentation Experiment on Branched Epoxy Novolac Resin

The main purpose of this study was to investigate the micro-indentation test method on the branched epoxy novolac resin (ENR) and to validate it by means of finite element simulation. At the first stage, the micro-indentation test was carried out with the purpose of establishment of the Young’s modulus of ENR by the empirical relation to polymer materials. Experiments were performed by using the Vickers-type indenter. At the second stage, the finite element model was used to model the load-displacement curve of the material with the use of the initial values of elastic modulus and yield strength of material. The effectiveness of the use of these properties was investigated by using the planning of experiments and response surface technique. Full factorial design method was used to perform a series of numerical experiments. Then, a comparison of the results of micro-indentation test and finite element simulations was performed in order to compare and validate the values of Young’s modulus obtained from two different techniques. Good correlation between the experimental and numerical Young’s modulus was observed.

Polystyrene‐modified novolac epoxy resin/clay nanocomposite: Synthesis, and characterization

A polystyrene‐modified epoxidized novolac resin/montmorillonite nanocomposite was fabricated and characterized successfully. For this purpose, novolac resin (NR) was epoxidized through the reaction of phenolic hydroxyl group with epichlorohydrin in super basic medium to produce epoxidized novolac resin (ENR). Afterward, a polystyrene was synthesized by atom transfer radical polymerization (ATRP) technique, and then brominated at the benzylic positions using N‐bromosuccinimide (NBS). The brominated polystyrene (PSt‐Br) was reacted with ethanolamine in basic medium in order to afford an amine‐functionalized polystyrene (PSt‐NH2). An organo‐modified montmorillonite (O‐MMT) was synthesized through the treatment of MMT with hexadecyl trimethyl ammonium chloride salt. Finally, ENR‐PSt/MMT nanocomposite was fabricated through curing a mixture of ENR (70 wt.%) and O‐MMT (5 wt.%) with PSt‐NH2 (25 wt.%). Transition electron microscopy (TEM) and powder X‐ray diffraction (XRD) analysis revealed that the fabricated nanocomposite has an exfoliated structure. Thermal property studies using thermogravimetric analysis (TGA) showed that the curing of ENR by PSt‐NH2, as well as incorporation of a small amount of MMT have synergistic effect on the thermal stability of the ENR resin.

Carbon Nanotube‐phenolic Resin Composite Electrode Fabricated by Far Infrared‐assisted Crosslinking for Enhanced Amperometric Detection

AbstractThe composite of carbon nanotube (CNT) and phenolic resin was prepared in a piece of fused silica capillary based on the far infrared‐assisted crosslinking of phenolic novolac resin in the presence of CNTs and hexamethylenetetramine for electrochemical sensing. The surface morphology and structure of the prepared materials were investigated by scanning electron microscopy, energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy. The results indicated that CNTs in the composite was adhered by the crosslinked phenolic resin to form an electrically conductive network. Many broken ends of CNTs appeared on the surface of the composite electrode in the form of a nanoelectrode array. The novel electrode was employed in the amperometric detection of synephrine and hesperidin in Citri Reticulatae Pericarpium in combination with capillary zone electrophoresis. The novel CNT‐based electrode owned the advantages of high sensitivity, low fabrication expense and excellent electrocatalytic performances, indicating great promise for the electrochemical detection in other analysis systems.

Fabrication and evaluation of structural film adhesive using oxazolidinone modified novolac epoxy resin

ABSTRACTEpoxy film adhesives are of prime importance for the fabrication of lightweight honeycomb structures for aerospace industries. This work involves the synthesis of oxazolidinone modified epoxy novolac resin (EPN‐OXA) via the reaction of EPN and toluene diisocyanate. EPN‐OXA was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and epoxy equivalent weight. EPN‐OXA was blended with solid epoxy resin, polyethersulfone (PES) toughened liquid epoxy resin, dicyandiamide, and aluminum powder to fabricate a film adhesive curing at 170–180 °C. Effect of additives and curative on the adhesive property was studied to optimize the composition. Effect of PES on the optimized composition was studied in detail. The best composition exhibited lap shear strength of 370 ± 10 kgf cm−2 at 25 °C and the strength was retained to 75% at −196 °C and 52% at 120 °C. PES significantly enhanced the interfacial strength at different temperatures (~1.6‐fold at −196 and 25 °C and ~1.8‐fold at 120 °C). It also improved tensile strength and fracture toughness by 1.4‐ and 2‐fold, respectively. The toughening effect of PES was further confirmed by scanning electron microscopy images. PES marginally reduced the glass‐transition temperature and it exhibited no effect on thermal stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47520.

Novolac-based Polymer-silver Nanoparticles Hybrid: Synthesis, Characterization and Antibacterial Evaluation

Background:Hybrids, composed of silver nanoparticles (AgNPs) dispersed inside a polymer matrix thus combining properties of both the components offer antibacterial activity and several advantages. Nevertheless, the development of antibacterial hybrid material comprising both novolac type phenolic resin and AgNPs remains one of the untouched issues in human healthcare.Objective:We report herein the simple preparation of hybrid derived from functionalized novolac resin and AgNPs. The hybrid was tested for antibacterial activity towards Gram-positive and Gramnegative bacteria.Method and Results:Preparation and characterization of functionalized novolac resin and hybrid were achieved. Gram-positive bacteria (Staphylococcus aureus MTCC 3160, Staphylococcus epidermidis NCIM2493, Bacillus subtilis) and Gram-negative bacteria (Pseudomonas aeruginosa ATCC27853, Escherichia coli) were used to test the bactericidal efficiency of hybrid. The antibacterial effectiveness of hybrid was determined in terms of the minimum inhibitory concentration (MIC). In addition, treatment with hybrid caused cytoplasmic contents leakage evidencing membrane damage.Conclusion:The hybrid developed thus could provide opportunities to fabricate a wide range of antibacterial functional materials for different purposes in human health associated sectors.

Synthesis and Thermal Properties of Ethynyl Phenyl Azo Phenol-biphenylene Resin.

A novel addition curing ethynyl phenyl azo phenol-biphenylene resin (EPABN) was synthesized by introducing ethynylphenyl group into biphenyl novolac resin (BN) through diazo coupling reaction. Its synthesis reaction and curing mechanism were also proposed. Fourier transform infrared spectroscopy and 1H NMR spectroscopic analysis showed that the ethynylphenyl group was successfully linked to the BN molecular chain. By differential scanning calorimetry analysis, the curing process of EPABN resin was determined to be 150 °C/2 h + 172 °C/2 h + 203 °C/4 h + 255 °C/4 h + 300 °C/4 h. Gel permeation chromatography and elemental analysis showed that the introduction of ethynylphenyl group increased the number-average molecular weight and weight-average molecular weight of EPABN. Thermogravimetric analysis showed that the EPABN resin synthesized under the obtained optimum conditions has excellent heat resistance, ablation resistance, and mechanical properties. Td5 and Td10 of heat resistance of the cured EPABN resin are 463 and 531 °C, respectively, and its residual char yield at 700 and 1000 °C is 78.2% and 72.1%, respectively.

Intumescent Coatings Based on Tannins for Fire Protection

Accidents involving fire occur every day around the world, affecting thousands of people and causing economic losses. Some accidents are caused by steel structure failures, which experience a significant reduction in mechanical properties at temperatures of 400-550˚C. Therefore, fire protective coatings are required for steel structures and interest in the development of intumescent coatings has increased considerably. In this study, black wattle tannin was used as a carbon source in the formulation of intumescent coatings. Concentrations of 5% and 10% of tannin were incorporated into a novolac resin. The coating was applied on a steel plate and the thermal protection was evaluated by sample exposure to a flame for 30 min. The results showed that the tannin compound could be used as a carbon source for intumescent coatings. The temperature of the samples containing 10% of this compound was almost 300 ˚C lower compared to the uncoated steel plate.