Phenolic foams toughened with crosslinked poly (n‐butyl acrylate)/silica core‐shell nanocomposite particles

A new type of crosslinked poly (n‐butyl acrylate) (PBA)/silica core‐shell nanocomposite particles was adopted as toughening agent to improve the mechanical properties of phenolic foams. The effects of the nanocomposite particles on the structures and properties of lightweight phenolic foams were investigated. SEM result showed that the addition of a small quantity of the nanocomposite particles can significantly enhance the structural homogeneity of phenolic foams. Thermalgravimetric analysis result suggested that the incorporation of the nanocomposite particles did not affect the thermal stability of the toughened phenolic foams. The flexural strength, compressive strength, and elastic modulus of the phenolic foams increased distinctively after the addition of the nanocomposite particles, the maximum values of which increased by 36.0%, 42.9%, and 32.3%, respectively. In this study, the optimum dosage of the nanocomposite particles is 0.03 phr in the modified phenolic foams. Moreover, the influence on the flammability of phenolic foams by toughening can almost be neglected. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42590.     

腰果酚/聚乙烯醇改性酚醛树脂的制备

以腰果酚、聚乙烯醇作为苯酚与甲醛缩聚的改性剂,研究了腰果酚和聚乙烯醇的用量,催化剂类型和用量等对其性能的影响。结果表明:改性酚醛树脂的最佳条件为:苯酚、腰果酚、聚乙烯醇、甲醛的最佳摩尔比为0.85:0.32:0.02:1,最佳的催化剂为苯磺酸,用量为4.5%。     

腰果酚/聚乙烯醇改性酚醛树脂的制备

以腰果酚、聚乙烯醇作为苯酚与甲醛缩聚的改性剂,研究了腰果酚和聚乙烯醇的用量,催化剂类型和用量等对其性能的影响。结果表明:改性酚醛树脂的最佳条件为:苯酚、腰果酚、聚乙烯醇、甲醛的最佳摩尔比为0.85:0.32:0.02:1,最佳的催化剂为苯磺酸,用量为4.5%。     

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。     

腰果酚、三聚氰胺改性酚醛树脂的制备

以苯酚与甲醛作为原料,采用腰果酚、三聚氰胺对酚醛树脂进行改性,研究了腰果酚含量、三聚氰胺含量、催化剂加入方式以及干燥温度等对其性能的影响,得出改性酚醛树脂的适宜生产工艺条件:n(总酚量):n(醛)=1:0.91,n(苯酚):n(甲醛):n(腰果酚):n(三聚氰胺)=1:1:0.1067:0.0541,催化剂含量3.1%,反应时间约为2.5h,真空干燥温度为100℃。     

酚醛树脂基耐磨复合材料的改性及性能

采用原位改性法合成腰果酚改性酚醛树脂,并与粒径不同的碳化硅(SiC)混合物复配制备了腰果酚改性酚醛树脂基耐磨复合材料。通过红外光谱证明成功合成了腰果酚改性酚醛树脂,且树脂符合磨具磨料用液体树脂的基本要求。扫描电镜SEM图及力学性能测试结果表明,与普通酚醛树脂相比,腰果酚改性酚醛树脂粘结Si C的能力更强,且偶联剂的加入能提高树脂与碳化硅之间的相容性。在腰果酚含量为15%时,固化剂含量为10%,偶联剂含量为2.5%时,改性酚醛树脂基复合材料的拉伸、弯曲等力学性均能达到最优。通过分析耐磨测试结果发现,二硫化钼的添加能有效降低复合材料的磨损率,提高腰果酚改性酚醛树脂基耐磨复合材料的耐磨性。     

腰果酚改性甲阶酚醛树脂的合成及其泡沫性能研究

用腰果酚代替部分苯酚改性酚醛树脂,制备可发性甲阶酚醛树脂。并讨论了腰果酚替代量对改性酚醛树脂性能及其泡沫性能的影响,通过红外光谱仪、热重分析仪对树脂结构及热稳定性进行表征,运用万能电子试验机对甲阶酚醛树脂泡沫的力学性能进行了研究。结果表明:当腰果酚替代量为10%时,制得的树脂黏度为4650mPa·s,树脂中游离苯酚含量从6.72%降为5.45%,游离甲醛含量从1.17%降为0.68%,甲阶酚醛树脂泡沫压缩强度达到最大值0.20MPa,但树脂热稳定性及甲阶酚醛树脂泡沫阻燃性有所下降。     

Flammability properties and mechanical performance of epoxy modified phenolic foams

This work has been mainly focused on the development and optimization of the processing methodology to produce epoxy modified phenolic foams. This study analyzes the relation between the composition and the structure as well as the mechanical and flammability performance of epoxy‐phenolic (E‐P)‐based foams. Phenolic foams modified with different types and compositions of epoxy resin were successfully synthesized and characterized, showing uniform pore structure. Two epoxy resins were used for this approach. One is regular diglycidyl ether of bisphenol A (Epon 826) type and the other is a brominated bisphenol A (DER 542), which has halogen groups in the structure to improve the flammability properties of the resulting foams. Cone calorimeter (ASTM E 1354) was used to measure the heat release rate, the time to ignition, and other flammability properties of the E‐P foams with different types of epoxy resins, under well‐controlled combustion conditions. The mechanical performance of the system was studied and compared with competing foams, such us phenolic, epoxy, and polyurethanes, in aspects of compression, friability, and shear performances. Compared with conventional phenolic foams, E‐P foams exhibit significant improvement in mechanical performance, lower friability and similar resistance to flame. These results demonstrate the potential of the E‐P foam as a flame resistant and high performance core material for sandwich structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1399–1407, 2007     

Mechanical and thermal properties of modified red mud‐reinforced phenolic foams

A new type of composite based on phenolic foams reinforced with red mud microparticles was prepared using a thermal foaming method. Red mud was ground into ultrafine particles with grain diameters ranging from 1 to 1.5 μm. Silane coupling agent γ‐ureidopropyltriethoxysilane was used to modify the red mud microparticles to improve particle dispersion and adhesion between the particles and the phenolic matrix. The effects of the modified red mud microparticles on the mechanical and thermal properties of the composite were investigated at weight ratios ranging from 0 to 21%. The phenolic foams incorporating 15 wt% of the filler exhibited the best integrated performance. In comparison with native phenolic foams, tensile strength and impact strength were increased by 81.8 and 82.3%, respectively. Furthermore, the addition of modified red mud microparticles to the phenolic foam significantly decreased its thermal conductivity while increasing its limiting oxygen index. A morphological analysis using scanning electron microscopy indicated that incorporation of the modified red mud microparticles into the foam produced relatively small and uniformly sized cells within the material, which indicated that the observed improvements in mechanical and thermal properties were primarily due to the chemical adhesion between the particles and the matrix and good dispersion of particles in the matrix. The reinforced foams described in this study can be used in a variety of applications in the field of heat insulation. © 2018 Society of Chemical Industry     

Adhesive properties of blends of phenol/cardanol–formaldehyde copolymer resin with polychloroprene rubber

This is a continuation of an earlier study on the adhesive properties of neoprene–phenolic resin blends. The phenolic resin used is derived from a mixture of phenol and cardanol, a renewable resource. Having established the utility of cardanol for formulating adhesives, this study investigates the effect of varying the phenol: cardanol ratio in the formulation. The effect of varying the total resin content at various phenol/cardanol ratios is also studied. It is found that a phenol/cardanol ratio of 80:20 is optimum for shear strength of aluminum–aluminum bonds, while a 60:40 ratio is the best for peel properties. For SBR–SBR and SBR–Al bonds, a 60:40 ratio is optimum for both peel as well as shear strength. Further, an 80 phr total resin content in the primer and a 40 phr resin content in the adhesive are found to give the best shear and peel strengths for SBR–Al bonds. The study reveals that the copolymer based on phenol, cardanol and formaldehyde is a better choice for the resin than either of the individual condensation products of phenol or cardanol with formaldehyde.     

Phenolic foams from wood tar resols

This article investigates resole‐type phenolic foams, in which 40% phenol was substituted with distilled oily fractions from wood tar. Different proportions of blowing agent, hexamethylenetetramine, and stabilizer, a sodium alkyl sulfate surface active agent, were used to produce a series of rigid foams, which were characterized by curing index, density and hardness. The average curing index was about 90% and densities ranged from 480 to 960 kg.m^?3. A fractal dimension (D_f) approach was used to assess the homogeneity of pores within the foams and an average (dimensionless) value of 2.6 was found, indicating a non uniform structure. Compressive strength tests of the foams gave values above 1.0 MPa, which is higher than those for typical phenolic foams. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Effect of SiO2 on rheology,morphology, thermal,and mechanical properties of high thermal stable epoxy foam

A series of highly thermostable epoxy foams with diglycidyl ether of bisphenol‐A and bisphenol‐S epoxy resin (DGEBA/DGEBS), 4,4′‐diaminodiphenyl sulfone (DDS) as curing agent have been successfully prepared through a two‐step process. Dynamic and steady shear rheological measurements of the DGEBA/DGEBS/DDS reacting mixture are performed. The results indicate all samples present an extremely rapid increase in viscosities after a critical time. The gel time measured by the crossover of tan δ is independent of frequency. The influence of SiO₂ content on morphology, thermal, and mechanical properties of epoxy foams has also been investigated. Due to the heterogeneous nucleation of SiO₂, the pore morphology with a bimodal size distribution is observed when the content of SiO₂ is above 5 wt %. Dynamic mechanical analysis (DMA) reveals that pure epoxy foam possesses a high glass transition temperature (206°C). The maximum of specific compressive strength can be up to 0.0253 MPa m³ kg^?1 at around 1.0 wt % SiO₂. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40068.     

Preparation and characterization of highly thermostable polyisocyanurate foams modified with epoxy resin

A series of epoxy resin–modified polyisocyanurate (EP‐PIR) foams with oxazolidone (OX) rings and isocyanurate (IS) rings have been successfully prepared by the reaction of polymethylene polyphenyl isocyanate (PAPI) and diglycidyl ether of bisphenol‐A (DGEBA). Fourier transform infrared spectroscopy and differential scanning calorimetry are performed to investigate the influence of curing temperature on the chemical structure of EP‐PIR foams. The results indicate that low temperature is beneficial to the formation of the IS ring, and high temperature is in favor of the OX ring. The influence of the mole ratio of [PAPI]/[DGEBA] on the mechanical properties and thermal stability has also been studied. With the increase of [PAPI]/[DGEBA], the specific compressive strength shows a maximum of 0.0135 ± 0.0003 MPa m³/kg. The optimized mole ratio of [PAPI]/[DGEBA] is around 2.5 to reach the better mechanical and thermal properties, and the glass‐transition temperature is as high as 323.5°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43085.     

Resorcinol in high solid phenol−formaldehyde resins for foams production

The acid curing agent content and foaming temperature could be reduced by improving the resol reactivity. In this study, highly active and solid phenol?resorcinol?formaldehyde copolymer resins (PRFRs) with different resorcinol/phenol (R /P ) molar ratios and formaldehyde/(phenol + resorcinol) [F /(P + R )] molar ratios were synthesized through the copolymerization of resorcinol, formaldehyde, and phenol. Phenol?resorcinol?formaldehyde foams (PRFFs) were prepared with synthetic PRFRs. The results showed that PRFR‐2 exhibited higher reactivity, faster curing speed, and better thermal stability. In addition, the foam produced with the PRFR‐2 had improved mechanical and flame retardation properties and a compressive strength of 0.18 MPa, a flexural strength of 0.25 MPa, and a limited oxygen index (LOI) greater than 37%. The increased reactivity of the PRFRs correlated with the changing mechanical properties of PRFFs because of the effects of resorcinol and the molar ratio of formaldehyde to phenol and resorcinol. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44881.     

高邻位腰果酚-苯酚-甲醛树脂的合成及表征

在原苯酚甲醛高邻位树脂体系中引入具有长链烷基的取代酚——腰果酚进行改性,通过IR、DSC、TG等手段对高邻位腰果酚-苯酚-甲醛树脂的结构、固化性能及耐热性进行了分析,结果表明,合成树脂结构中含有腰果酚,且树脂结构属于高邻位结构,该树脂耐热性优于苯酚甲醛高邻位树脂;腰果酚的引入使固化速度和时间稍有减慢,但不影响固化工艺.制备了腰果酚-苯酚-甲醛-丁腈胶黏剂,胶黏剂具有优异的韧性及粘接性能.     

Molecular design of anti-biofouling materials from natural phenolic compounds

Many natural phenolic compounds found in plants are well known for their antibiotic and antioxidant activities. It has been hypothesized that these activities of natural phenols could be used for developing permanent anti-biofouling coatings. In this study, two phenolic components, anacardic acid and cardanol, were extracted from cashew nut shell liquid, and tested for their antibiotic and anti-biofouling activities against Pseudomonas fluorescens. Both compounds killed all the cells within 18 hours (anacardic acid) and 30 hours (cardanol) after the addition to the culture media at a concentration of 800 μg/ml. To form a stable permanent coating of these compounds, first they were polymerized by enzymatic polymerization, and the polymers were cross-linked on a glass slide. P. fluorescens were cultured on the coated and uncoated glasses for two weeks, and the images of the cells grown on the surfaces were taken by SEM. The coated surfaces clearly demonstrated anti-biofouling activities, showing not only fewer numbers of cells but also less exopolymer than the uncoated surfaces. Based on these results, a phenolic compound with a similar structure of anacardic acid was synthesized by using propylene diamine and fluorocarboxylic acid with cardanol. The synthesized phenolic compound was polymerized and cross-linked on a glass slide to test the anti-biofouling activity. The SEM images of the cells on the coated surface showed considerable decreases in the number of adhered cells and the amount of exopolymers even more than the anacardic acid and cardanol coatings. It is thought that the natural phenolic compounds with active functional groups can be used for anti-biofouling agents. This paper is dedicated to Prof. Chang Kyun Choi for celebrating his retirement from the School of chemical and biological engineering of Seoul National University.     

The toughening effect and mechanism of styrene‐butadiene rubber nanoparticles for novolac resin

In this article, phenolic nanocomposites were prepared using styrene–butadiene rubber (SBR) nanoparticles with an average particle size of about 60 nm as the toughening agent. The mechanical and thermal properties of phenolic nanocomposites and the toughening mechanism were studied thoroughly. The results showed that when adding 2.5 wt % SBR nanoparticles, the notched impact strength of phenolic nanocomposites reached the maximum value and was increased by 52%, without sacrificing the flexural performance. Meanwhile, SBR nanoparticles had no significant effect on the thermal decomposition temperature of phenolic nanocomposites. The glass‐transition temperature (T_g) of phenolic nanocomposites shifted to a lower temperature accompanying with the increasing T_g of loaded SBR, which showed there was a certain compatibility between SBR nanoparticles and phenol‐formaldehyde resin (PF). Furthermore, the analysis of Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy indicated that there existed a weak chemical interaction between SBR nanoparticles and the PF matrix. The certain compatibility and weak chemical interaction promoted the formation of a transition layer and improved the interfacial bonding, which might be important reasons for the great enhancement of the toughness for phenolic nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41533.     

Carbon foam production from bio-based polyols of liquefied spruce tree sawdust: Effects of biomass/solvent mass ratio and pyrolytic oil addition

One of the next-generation structural materials is carbon foam. Porous materials have become an intriguing alternative material to traditional ones in many utilizations based on their light weight and incomparable properties. Coal or fossil oils are conventionally used to produce pitch, phenolic resin, and polyurethane as carbon foam precursor. Biomass liquefaction is a developing technique to convert biomass resources into the industrial chemicals. In this study, spruce tree sawdust was liquefied under mild conditions with different solvent type (phenol or phenol + bio-oil mixture). The unique aspect of this work is the synthesis of bio-polyol when pyrolytic oil is used as an alternative to phenol in the solvolysis reaction and its evaluation in carbon foam production with multilayer graphene sheets. Therewithal, the ratios of biomass to solvent were 1/3 as well as 1/5, and the comparison of product characteristics is another originality of the study. Slow pyrolysis of spruce tree sawdust was performed under static atmosphere and bio-oil was characterized with elemental analysis and various chromatographic and spectroscopic techniques. The effect of mass ratio of biomass/solvent on the characteristics of porous resin foams synthesized from liquefaction product. Obtained resin foams were carbonized at 400 °C, and then activated at 800 °C under nitrogen atmosphere. Structure evaluation of resin foams, carbonized foams, and activated carbon foams from liquefied spruce tree sawdust was investigated by using elemental analysis, x-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electron microscopy, true/bulk density, and compressive strength tests. Although the surface area values decreased when bio-oil was added as a solvent, it was determined that the compression strengths of the produced carbon foams (up to 1.080 MPa) were higher than that of conventional phenolic foams. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47185.     

A new thermo set system based on cardanol benzoxazine and hydroxy benzoxazoline with lower cure temperature

This paper describes the synthesis and characterization of a new curing system consisting of mono functional benzoxazine based on cardanol and hydroxyl functionalized benzoxazoline, where the phenol hydroxyl group acts both as a catalyst for the ring opening reaction of benzoxazine as well as oxazoline ring. The curing initiation temperature of cardanol benzoxazine was reduced to 138 °C from 230 °C with incorporation of hydroxy benzoxazoline (HBO). The heat of polymerization value has increased with incorporation of hydroxyl benzoxazoline up to 50 mol.%. The activation energy of cardanol benzoxazine has reduced initially with incorporation of hydroxyl benzoxazoline and later increased with respect to composition of monomers in the mixture. The flexible cardanol benzoxazine polymer displayed a lower storage modulus of 2.7 × 10⁸ [pa] and a tan δ of 104 °C. The copolymers exhibited significant enhancement in these values with incorporation of hydroxyl benzoxazoline. The width of tan δ peak of copolymers also increased suggesting enhancement of toughness.