Effect of cashew nut shell liquid (CNSL) on properties of phenolic resins

Cashew nut shell liquid (CNSL) is a natural product, and because of its phenolic nature it undergoes reactions similar to those of phenol. The cost of CNSL is much less than phenol. The effect of replacement of phenol by CNSL on the properties of novolak and resole resins was experimentally investigated. © 1996 John Wiley & Sons, Inc.     

Polymers from Renewable Resources. XXVII. Studies on Synthesis,Characterization, and Thermal properties of Resins Derived from Cardanyl Acrylate-Furfural-Organic Compounds

Cardanol, the major constituent of cashew nut shell liquid (CNSL), is extracted from CNSL by vacuum distillation at 3–4 mm pressure of mercury and 230–240°C temperature. Cardanyl acrylate, a derivative of cardanol, is prepared by the Kaliyappan method. A number of resins have been synthesized by condensing cardanyl acrylate with furfural and selective organic compounds in the presence of acid as catalyst. The resins have been characterized by Fourier transform infrared spectra. Solvent absorptivity of the resins have been studied by taking toluene and dimethyl formamide as solvents. The thermal behavior of the resins have been studied. The overall activation energy and order of degradation of the resins have also been evaluated using the Freeman-Anderson method.     

Hybrid Polymer Networks of Epoxy Resin and Substituted Phenolic Novolacs

Hybrid polymer networks of diglycidyl ether of bisphenol (DGEBA) resin and phenolic novolac resins were prepared and tested for mechanical properties, hardness, and water absorption. The novolacs employed were based on each of phenol and substituted phenols such as p-cresol, t-butyl phenol, and cardanol. Cardanol is the main constituent of cashew nut shell liquid (CNSL), a renewable resource. Blends containing 10–15 wt% of novolac resin show substantial improvement in properties. These properties show a declining trend with higher novolac loading. The stoichiometric ratio between phenol and formaldehyde in the novolacs was optimized (1:0.8) for maximum property enhancement. The property profiles of the epoxy/novolac networks show that novolacs are effective modifiers for commercial epoxy resin. Incorporation of novolacs of substituted phenols results in relatively greater improvement in energy absorption during failure.     

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     

Effect of Phenol/Formaldehyde Stoichiometry on the Modification of Epoxy Resin Using Epoxidized Novolacs

ABSTRACT

Unmodified epoxy resins based on bisphenol A exhibit brittleness and low elongation after cure. This article reports the results of a study for improving the properties of epoxy resin by blending with suitable thermosets. Hybrid polymer networks of diglycidyl ether of bisphenol A (DGEBA) resin with epoxidized phenolic novolac resins (EPN) containing phenol and formaldehyde in different stoichiometric ratios were prepared by physical blending. The modified epoxy resins were found to exhibit improved mechanical and thermal properties compared to the neat resin. DGEBA resins containing 2.5 to 20 wt% of epoxidized novolac resins (EPN) prepared in various stoichiometric ratios (1:0.6, 1:0.7, 1:08, and 1:0.9) between phenol and formaldehyde were cured using a room temperature amine hardener. The cured samples were tested for mechanical properties such as tensile strength, modulus, elongation, and energy absorption at break. All the EPNs are seen to improve tensile strength, elongation, and energy absorption at break of the resin. The blend of DGEBA with 10 wt% of EPN-3 (1:0.8) exhibits maximum improvement in strength, elongation, and energy absorption. EPN loading above 10 wt% is found to lower these properties in a manner similar to the behavior of any filler material. The property profiles of epoxy–EPN blends imply a toughening action by epoxidized novolac resins and the extent of modification is found to depend on the molar ratio between phenol and formaldehyde in the novolac.     

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     

Sustainable phenolic thermosets coatings derived from urushiol

The over-exploitation of finite fossil resources and/or the increased environmental and sustainable awareness inspire scientists and technologists to search for inexpensive alternatives from renewable chemicals. Phenol formaldehyde (PF) resins, the oldest type of synthetic polymers with good mechanical properties and heat resistance, are widely used in the production of coatings, laminates, molding compositions, and glues. Here, biobased urushiol-derived PF resins were synthesized from the alkali-catalyzed reaction between urushiol and formaldehyde. The chemical compositions and molecular structures of resole resins were characterized by carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy, and their curing behaviors were studied by differential scanning calorimetry. The as-prepared urushiol-derived resole resins had methylol (Ph−CH₂OH), ortho- and para-hemiformal groups (Ph−CH₂OCH₂OH), and the para−para/ortho−para/ortho−ortho links of methylene groups (Ph−CH₂−Ph), whereas the resole resins had low curing temperatures at about 100–113°C. Additionally, given the long side alkyl group moiety on the aromatic rings of urushiol, the films of cured urushiol-derived resole resins had low glass transition temperatures of 132 ± 2°C. Furthermore, the as-prepared urushiol-derived coatings exhibited excellent physical and mechanical properties.     

Physical,mechanical, and thermal properties of polyurethanes based on hydroxyalkylated cardanol–formaldehyde resins

Polyurethanes are synthesized using three different hydroxyalkylated cardanol–formaldehyde resins, diphenylmethane diisocyanate (MDI), and a commercial polyol (PPG‐2000). These polyurethanes are found to be tough and crosslinked. A polyurethane prepared using a higher mole ratio of cardanol/formaldehyde of hydroxyalkylated cardanol–formaldehyde resin is found to possess better thermal and mechanical properties than the polyurethane prepared from a lower mole ratio. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 284–288, 2005     

Phenolic resins: 100 Years and still going strong

After 100 years phenolic resins continue to be a prominent resin system with an impressive worldwide volume of nearly 6 million tons/year. It is a ubiquitous adhesive for a diverse spectrum of materials such as wood, glass, metal, paper and rubber with several of these applications being developed by Baekeland during the early stages of his resin commercialization. Many recent technical conferences have been held and were identified with important early Baekeland advances such as Baekeland 2007, Baekeland 2009 and the more recent Baekeland 2011 – all commemorating different initial activities of Baekeland and centennial recognition of his 1907 patent, first production of phenolic resin in Erkner, Germany in 1909 and the centennial celebration of the production of phenolic resin in Japan in 1911. This presentation provides an overview and evaluation of large volume application markets for resole and novolak resins in 2011 and comments related to anticipated greater growth of novolak resins over resole resins. Both resole and novolak resins are viewed as reactive intermediates that undergo a variety of chemical transformations into various improved and in many instances upgraded resin systems that lead to both recognizable and newly reactive resins for value added products. New areas involving phenolic resins are described and consist of Phenol Resorcinol Formaldehyde (PRF) resins, Nanomodification, Novel Novolak Process, ionic liquids, Phenolic Hybrids, and Poly Aryl Ether Amide based on novolak and phenylene bisoxazoline (PBO).     

Studies on jute-reinforced composites,its limitations,and some solutions through chemical modifications of fibers

Jute, unlike other natural fibers, absorbs moisture and its moisture regain property is quite high. Water migration and subsequent degradation of jute-based composites can be a problem. Because jute is hydrophilic and the matrix resins are mostly hydrophobic, wetting of the fibers with resins is poor, for which high resin consumption may occur that would increase the cost of composites. To reduce the moisture regain property of jute fiber, it is essential to pretreat the jute fiber so that the moisture absorption is reduced and the wettability of the resin is improved. Jute fiber in the form of nonwoven jute has been pretreated with precondensate like phenol formaldehyde, melamine formaldehyde, cashew nut shell liquid-formaldehyde, and polymerized cashew nut shell liquid. The moisture content of the pretreated nonwoven jute has been determined by conventional methods and by a differential scanning calorimetric technique. Treatment of jute with precondensate causes the reduction of water regain property in jute. Pretreated nonwoven jute has been impregnated with phenol formaldehyde resin, and the composite board has been prepared therefrom. The jute composite board has been tested for bending strength, tensile strength, thickness swelling, and water absorption. Thermal analyses, such as differential scanning calorimetry and thermogravimetry, have also been conducted on jute and pretreated jute fibers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1093–1100, 1998     

Effects of cashew nut shell liquid as a plasticizer on cure characteristics,processability, and mechanical properties of 50 : 50 NR/EPDM blends: A comparison with paraffin oil

50 : 50 natural rubber (NR) and ethylene–propylene–diene monomer rubber (EPDM) blends were prepared with different contents of cashew nut shell liquid (CNSL), a natural product obtained from the shells of the cashew nut, as a plasticizer. For comparison, a commercial paraffin oil plasticizer was also used. The effect of plasticizer content on the cure characteristics, processability, and mechanical properties such as tensile strength, elongation at break, and Young's modulus before and after ageing was investigated. Scanning electron microscopy (SEM) was used to observe the blend morphology. The results indicated that the CNSL plasticizer resulted in lower Mooney viscosity and lower cure time of the 50 : 50 NR/EPDM blends. The incorporation of CNSL into 50 : 50 NR/EPDM blends improved tensile strength and elongation at break but decreased Young's modulus. On addition of CNSL the resistance of the blends to heat and weathering ageing improved. Scanning electron micrographs revealed that the morphology of the blend plasticized with CNSL is finer and more homogeneous compared with the blend plasticized with paraffin oil. Overall results indicate that CNSL can be used as a cheaper plasticizer to replace paraffin oil in NR/EPDM blends with improved processability and mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

New melamine–formaldehyde–ketone resins. VI. Preparation of filled molding compositions and compression‐molding materials from reactive solvents based on cyclohexanone

The conditions and a method of preparing new molding compositions and filled compression‐molding materials from melamine–formaldehyde–cyclohexanone resins are described. The resins were obtained from melamine solutions in a reactive solvent prepared by the reaction of 1 mol of cyclohexanone with 7 mol of formaldehyde. The fillers were wood powder and sulfite cellulose. The thermal properties of the samples prepared from the compositions were studied with dynamic thermal analysis, thermogravimetry, and differential scanning calorimetry analysis. Selected mechanical properties [Brinell hardness, unnotched impact strength (Charpy method), and bending strength] of the cured resins were also measured. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterisation of rigid polyurethanes based on hydroxyalkylated cardanol formaldehyde resin

Abstract

Rigid polyurethanes have been synthesised using 4,4′-dicyclohexylmethane diisocyanate reacted with either hydroxyalkylated cardanol formaldehyde or hydroxyalkylated dimerised cardanol formaldehyde resins. These polyurethanes are crosslinked. Polyurethanes prepared from linear hydroxyalkylated cardanol formaldehyde resin have better thermal and mechanical properties than polyurethanes prepared from branched hydroxyalkylated resins. The polyurethanes prepared from hydroxyalkylated dimerised cardanol formaldehyde resins excel over the polyurethanes from hydroxyalkylated cardanol formaldehyde resins.     

Adhesives and coatings based on poly(vinyl acetal)s

Phenolic resins such as resole phenol– and cresol–formaldehyde, as well as low-molecular-weight epoxy resin based on bis(4-hydroxy phenol) cyclohexane were prepared and modified with various types of the prepared poly(vinyl acetal)s. Poly(vinyl formal), poly(vinyl isobutyral), and poly(vinyl propional) were used. This study indicated that the optimum conditions for curing phenolic or epoxy resin–poly(vinyl acetal)s adhesive compositions are of an equal weight ratio or a 2 : 1 weight ratio in the presence of phthalic anhydride (10 or 20 wt %) of resin content as a curing agent at 150°C for 20 or 60 min, respectively. The effect of acetal type on the tensile shear strength values of resin samples, cured under the previously mentioned optimum conditions for different times, was investigated. The effect of structure of cresol–formaldehyde and epoxy resins was also studied. Metallic and glass coatings from the previous pure resins and their formulated mixtures were also prepared and evaluated as varnishes or paints. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1769–1777, 1998     

可替代石油裂解原材料腰果酚探索

腰果壳液的主要成分腰果酚是一种具有不饱和长链烃基的天然酚类化合物。本文通过相关实验,将腰果酚加氢,制出了间十五烷基酚,并裂解制乙烯,可以得出腰果酚可替代石油作为生产乙烯裂解原料。     

Synthesis of novolac‐type phenolic resins using glucose as the substitute for formaldehyde

Novel Novolac type phenolic resins were prepared using glucose as the substitute for toxic formaldehyde (a carcinogenic chemical). The resins were synthesized with varying molar ratios of phenol to glucose, catalyzed by strong acid (such as sulfuric acid) at 120–150°C. Analysis of the resins using gel permeation chromatography (GPC) and proton nuclear magnetic resonance (¹H‐NMR) showed that they were broadly distributed oligomers derived from the Fridel‐Crafts condensation of phenol and glucose. Using hexamethylenetetramine (HMTA) as the curing agent, the phenol‐glucose resins could be thermally cured and exhibited exothermic peaks at 130–180°C, typical of thermosetting phenolic resins. The cured resins showed satisfactory thermal stability, e.g., they started to decompose at >280°C with residual carbon yields of above 58% at 600°C. Based on the thermal properties, phenol‐glucose resin with a molar ratio of 1 : 0.5 is promising as it could be cured at a lower temperature (147°C) and exhibited a satisfactorily good thermal stability: it started to decompose at >300°C with a residual carbon yield of >64% at 600°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of substituted phenol–formaldehyde resins using solid-state carbon-13 NMR

Crosslinked substituted phenol–formaldehyde resins were synthesized from cashew nut shell liquid, 3-n-pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and investigated using carbon-13 NMR in the solid state using cross-polarization, magic angle spinning, and dipolar decoupling. Comparisons were made between the spectra of pure phenol–formaldehyde resins and it was shown possible to distinguish between the resins. It was also shown that the proton-dephased spectrum gave better spectral resolution for the substituted compounds. In addition, the solids carbon-13 technique verified that the degradation of the substituted phenolic resins occurs first with the degradation of the side chain in agreement with suggestions from earlier work.     

Structural effect of phenalkamines on adhesive viscoelastic and thermal properties of epoxy networks

Phenalkamine, the Mannich reaction products from cardanol, formaldehyde, and polyamines were prepared using ethylene diamine, diethylene triamine and triethlene tetraamine. These products were characterized by high‐pressure liquid chromatography (HPLC), infrared spectroscopy, and nuclear magnetic resonance spectroscopy (1H NMR). Clearly resolved peaks due to presence of triene, diene, monoene, and saturated side chain containing species of cardanol were observed in HPLC. The presence of characteristic methylene linkages of Mannich bases at δ 3.5–4.0 ppm was observed by 1H NMR. These curing agents were reacted with diglycidyl ether of bisphenol‐A at room temperature and the curing times were optimized. The cured resins showed good adhesion with different metal surfaces particularly higher values were observed with copper due to its high surface energy. The viscoelastic properties of the cured samples were determined by dynamic mechanical thermal analysis. The storage modulus (E′) was found to be in the order of 10⁹ Pa and tan δ values are around 90°C. A reduction in storage modulus (E′) and an increase in tan δ values on postcuring were observed. Thermogravimetry analysis showed two‐stage degradation above 250°C for the cured samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4741–4748, 2006     

The effect of CTBN concentrations on the kinetic parameters of decomposition of blends of cardanol‐based epoxidized novolac resin modified with carboxyl‐terminated liquid copolymer

Cardanol‐based novolac resins were separately prepared with different mole ratios of cardanol‐to‐formaldehyde with different acid catalysts. These resins were epoxidized with epichlorohydrin, in basic medium, at 120°C. The resins were, separately, blended with different weight percentages of carboxyl‐terminated butadiene acrylonotrile copolymer and cured with polyamine. Structural changes during blending were studied by FTIR spectroscopic analysis. Coats–Redfern equation was utilized to calculate the kinetic parameters, viz., order of decomposition reaction (n), activation energy (E), pre‐exponential factor (Z), and rate decomposition constant (k), for the decomposition of the samples. It was found that the degradation of the epoxies and their blend samples proceeded in two steps. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

腰果酚制备可发性酚醛树脂的合成工艺研究

以苯酚、腰果酚、甲醛为原料,NaOH为催化剂,乙二醇为助剂,合成了可发性酚醛树脂,通过粘度,固含量,韧性测试研究了原料的配比,腰果酚替代苯酚的比例,催化剂用量,反应时间,反应温度及乙二醇用量对合成树脂性能的影响并通过IR,TG分析对树脂结构及耐热性进行了表征。结果表明,适宜的反应条件为:F/P比(甲醛与总酚物质的量比值)1.6,腰果酚替代量20%,催化剂用量1%,反应时间3 h,反应温度80℃,乙二醇质量分数10%～15%。以腰果酚制备的CPF树脂耐热性变化不明显,拉伸强度为22.34 MPa,断裂伸长率3.08%,冲击强度3.56 kJ/m2,较PF树脂有很大提高。