Phenolic resol resin from phenolated corn bran and its characteristics

To prepare phenolic resol resin, corn bran (CB) was liquefied in the presence of phenol and the liquefied CB was condensed with formaldehyde under alkaline condition. From NMR spectra of phenolated CB and phenolated CB–based resol resin, it was found that phenol was reacted with depolymerized CB components and the phenolated CB was methylolated by condensation with formaldehyde. Molecular weight distribution was divided into a high molecular weight zone, attributed mainly to phenolated CB, and a low molecular weight zone, which was attributed to the condensation reactants of formaldehyde and the unreacted phenol of liquefied CB. When reaction conditions became severe, a high molecular weight zone was increased. Formaldehyde/unreacted phenol of liquefied CB molar ratio most affected the change of a low molecular weight zone. To reduce the viscosity of the phenolated CB–based resol resin, a milder condensation condition was required compared with that for preparing the conventional resol resin. Properties of the resol resin were comparable to those of conventional resol resin for plywood manufacture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1365–1370, 2003     

Biodegradable polyurethane foam from liquefied waste paper and its thermal stability,biodegradability, and genotoxicity

Liquefaction of waste paper (WP) was conducted in the presence of polyhydric alcohols to prepare biodegradable polyurethane foam. The liquefied‐WP‐based polyol had suitable characteristics such as apparent molecular weight, hydroxyl value, and viscosity for the preparation of rigid polyurethane foam and was successfully applied to produce polyurethane foam with the appropriate combinations of foaming agents. The obtained foams showed satisfactory densities and mechanical properties as good as those of foams obtained from liquefied wood‐ and starch‐based polyols. The foams had almost the same thermal stability at initial weight loss and seemed to be potentially biodegradable because they were degraded to some extent in leaf mold. There were no mutagens or carcinogens in the water extracts of the foams. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1482–1489, 2002     

发泡性竹材苯酚液化物/多聚甲醛树脂的合成研究

在碱性条件下由竹材苯酚液化物和多聚甲醛制备出具有优良发泡性液化竹基酚醛树脂.考查了竹材液化物树脂化时间、温度、多聚甲醛与苯酚的物质的量比、氢氧化钠与苯酚物质的量比等因素对液化竹材酚醛树脂(BPE)黏度及其固含量的影响.结果表明,采用n(多聚甲醛)/n(苯酚)=1.2,树脂化时间为2 h,温度为70℃,n(氢氧化钠)/n...     

Phenolic resol resin adhesives prepared from alkali-catalyzed liquefied phenolated wood and used to bond hardwood

Wood-based resol resins were prepared from both water- and sodium hydroxide (NaOH)-catalyzed liquefied phenolated wood. The effects of various reaction parameters, e.g. the concentrations of phenol and formaldehyde, temperature, and time, on the extent of yield, free phenol content, molecular weight as well as the gluability of the resol resins have been evaluated. As far as the yield, free phenol content, and molecular weight are concerned, the optimum conditions of resol resin preparation were found to be a phenol : wood weight ratio of 4 : 6, a formaldehyde : phenol mole ratio of 1.5 : 1, a temperature of 82.5°C, and time 3 h. However, these optimum conditions changed when the performance of the adhesives was considered in terms of the adhesive bond strengths for plywood joints. The yield, molecular weights, polydispersity, and gluability of resol resins prepared from water-catalyzed liquefied wood were lower compared with those prepared from NaOH-catalyzed ones. In most cases, the dry-bond strengths of the experimental plywood joints exceeded the minimum Japan Agricultural Standard (JAS) values. On the other hand, except at a higher formaldehyde: phenol ratio (i.e. 2.0 : 1 mole ratio), the plywood joints of all samples delaminated during 'boil-dry-boil' cyclic treatments. However, both dry- and wet-bond strengths of the plywood joints could be improved to exceed standard values by using an additional crosslinking agent, e.g. poly(methylene (polyphenyl isocyanate)) (polymeric MDI). The adhesive perfomance of the wood-based resol resins was explained on the basis of the adhesion between wood veneers and resol resin adhesives.     

Synthesis of wood‐based epoxy resins and their mechanical and adhesive properties

Wood‐based epoxy resins were synthesized from resorcinol‐liquefied wood. Wood was first liquefied in the presence of resorcinol with or without a sulfuric acid catalyst at high temperature. Because of the hydroxyl groups, the resorcinol‐liquefied wood was considered as a precursor for synthesizing wood‐based epoxy resin. Namely, the phenolic OH groups of the liquefied wood reacted with epichlorohydrin under alkali condition. By the glycidyl etherification, epoxy functionality was introduced to the liquefied wood. The epoxy functionality of the resins was controlled by the concentration of phenolic OH groups in the liquefied wood, which would be a dominant factor for crosslink density and properties of the cured epoxy resins. The flexural strength (150–180 MPa) and the modulus of elasticity (3.2 GPa) of the highly crosslinked wood‐based epoxy resin were equivalent to those of the commercially available epoxy resin, diglycidyl ether of bisphenol A (DGEBA). Also, the shear adhesive strength of the wood‐based epoxy resin was higher than that of DGEBA when plywood was used as the adhesive substrates. The mechanical and adhesive properties suggested that the wood‐based epoxy resins would be well suited for matrix resins of natural plant‐fiber reinforced composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2285–2292, 2006     

Synthesis of epoxy resins from alcohol‐liquefied wood and the mechanical properties of the cured resins

New wood‐based epoxy resins were synthesized from alcohol‐liquefied wood. Wood was first liquefied by the reaction with polyethylene glycol and glycerin. The alcohol‐liquefied wood with plenty of hydroxyl groups were precursors for synthesizing the wood‐based epoxy resins. Namely, the alcoholic OH groups of the liquefied wood reacted with epichlorohydrin under alkali condition with a phase transfer catalyst, so that the epoxy groups were put in the liquefied wood. The wood‐based epoxy resins and the alcohol‐based epoxy resins as reference materials were cured with polyamide amine. The glass transition temperature (Tg), the tensile strength, and the modulus of elasticity of the wood‐based epoxy resin were higher than those of the alcohol‐based epoxy resin. Also, the shear adhesive strength of the wood‐based epoxy resin to steel plates was higher than those of the alcohol‐based epoxy resins, which was equivalent to the level of petroleum‐based bisphenol‐A type epoxy resins. The higher Tg of the wood‐based epoxy resin than that of the alcohol‐based epoxy resin is one of the evidences that the wood‐derived molecules were chemically incorporated into the network structures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Acid‐catalyzed liquefaction of waste paper in the presence of phenol and its application to Novolak‐type phenolic resin

Liquefaction of waste paper (WP) was performed in the presence of phenol with an acid catalyst. Newspaper (NP) was liquefied more easily than box paper (BP) or business paper (BNP). Differences in the degree of liquefaction were due to different chemical compositions. That is, NP had a relatively high lignin content, which is known to be easily liquefied, whereas BP and BNP were mainly composed of cellulose with a crystalline structure, which is difficult to liquefy. The acid concentration and phenol/WP ratio were more important factors in the regulation of liquefaction than reaction temperature. The changes in the apparent molecular weight depending on the reaction time were more significant for phenolated NP, with high lignin content, than for phenolated BP. The obtained phenolated products showed thermal flow properties and reactivity as good as those of phenolated wood and commercial Novolak resin. Thermosetting moldings were obtained from phenolated products, and their flexural properties and thermal stability were comparable to those of phenolated wood and commercial Novolak resin. Flexural properties were further improved by the cocondensation reaction between the unreacted phenol of phenolated products and formaldehyde. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1473–1481, 2002     

Polymerization induced viscoelastic phase separation of porous phenolic resin from solution

The porous structure evolution of thermosetting phenolic resin controlled by polymerization induced viscoelastic phase separation from solution was investigated in this work. The ultimate morphology and the evolution of a porous texture for the resol resin/solvent system were characterized by digital camera and optical microscopy. In-situ Fourier transform infrared spectroscopy and a rheological method were used to trace the curing reaction of the resol resin/solvent system. The impacts of solvent content and curing temperature on the foaming behavior were quantitatively and systematically investigated. Based on the relationship between the morphology evolution and curing dynamics, the foaming mechanism of the polymerization induced viscoelastic phase separation was elucidated. The present work provides new insight into the foaming mechanism of thermosetting materials and may be helpful for morphological control in the preparation of lightweight porous phenolic material. © 2016 Society of Chemical Industry     

Synthesis of phenolic resol resins using cornstalk-derived bio-oil produced by direct liquefaction in hot-compressed phenol–water

For the synthesis of biomass-based resol resins, cornstalk powders were liquefied in a hot-compressed phenol–water (1:4, wt./wt.) medium at 300–350 °C. It was observed that essentially no phenol was reacted with the cornstalk degradation intermediates during the liquefaction process. The cornstalk-derived bio-oils contained oligomers of phenol and substituted phenols, originated primarily from the lignin component of the cornstalk feedstock. Using the cornstalk-derived bio-oils, resol resins were readily synthesized under the catalysis of sodium hydroxide. The biomass-derived resol resins were brown viscous liquids, possessing broad molecular weight distributions. In comparison with those of a conventional phenol resol resin, the properties of the bio-based resins were characterized by GPC, FTIR, DSC and TGA. The as-synthesized bio-oil resol resin exhibited typical properties of a thermosetting phenol–formaldehyde resin, e.g., exothermic curing temperatures at about 150–160 °C, and an acceptable residual carbon yield of ca 56% at 700 °C for the cured material.     

自凝性松香改性酚醛树脂的合成研究

以两步法合成自凝性松香改性酚醛树脂,重点研究了酚醛浆的合成,通过考察酚醛摩尔比、催化剂用量、反应温度和反应时间对酚醛浆缩合反应的影响,得到适宜的酚醛浆合成条件:酚醛摩尔比1:1:5,催化剂用量为对叔丁基苯酚质量的3％,反应温度60℃,反应时间2．5-3 h。并对酚醛浆进行了GPC、VPO及红外光谱分析。利用该酚醛浆合成了具有良好自凝性的松香改性酚醛树脂。     

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     

Water-absorbing polyurethane foams from liquefied starch

Water-absorbing polyurethane foams were prepared from liquefied starch polyols and diphenylmathane diisocyanate (MDI) by using a cell-opening foaming surfactant. The liquefied starch polyols were obtained by the liquefactions of starch in the presence of polyethylene glycol-dominant reaction reagents by using sulfuric acid as a catalyst under either a refluxing condition or a reduced-pressure condition. The influences of the liquefaction conditions on the properties of the liquefied starch polyols were investigated, taking into account the requirements for preparing appropriate polyurethane foam. Feasible formulations for the preparation of the water-absorbing foams were proposed and the properties of the foams obtained were investigated. © 1996 John Wiley & Sons, Inc.     

环保可发性甲阶酚醛树脂的合成及性能研究

采用多聚甲醛代替37%甲醛溶液与苯酚逐步加成聚合,合成可发性甲阶酚醛树脂。通过粘度、固含量、游离苯酚和甲醛含量及凝胶时间测定以及IR,GPC和TG分析研究了多聚甲醛-苯酚物质的量比为1.8∶1条件下,缩聚反应温度及催化剂加入量对可发性甲阶酚醛树脂性能的影响。结果表明,缩聚反应温度为90℃,催化剂质量分数为5%(以苯酚质量计)时,可得到性能优良的可发性甲阶酚醛树脂,其性能如下:粘度2.6 Pa·s,游离甲醛质量分数1.23%,游离苯酚质量分数5.13%,热失重质量残留率50%以上。     

Preparation and characterization of water‐blown polyurethane foams from liquefied cornstalk polyol

Polyurethane foams were prepared from the liquefied cornstalk polyol, which was obtained by the liquefaction of cornstalk in the presence of polyhydric alcohols using sulfuric acid as catalyst. The advisable liquefaction reaction conditions were selected by investigating their influences on the properties of liquefied cornstalk polyol, taking account of the requirement for the preparation of appropriate polyurethane foams. The influences of the contents of catalysts, water, surfactant, and isocyanate on the properties of polyurethane foams were also discussed, and feasible formulations for preparing cornstalk‐based polyurethane foams were proposed. The results indicated that the foams prepared from such liquefied cornstalk polyol exhibited excellent mechanical properties and thermal properties, and could be used as heat‐insulating materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

杉木苯酚液化物合成热固型酚醛树脂的研究

以杉木为研究树种,对比不同料液比(木材与苯酚质量比)液化物与甲醛在碱性环境中反应,进行热固酚醛树脂制备试验。考察不同甲醛与苯酚物质的量之比值(r_F/P)、氢氧化钠与苯酚物质的量之比值(r_NaOH/P)和树脂化温度对树脂理化性能的影响。结果表明,采用料液比为1:2的液化物,r_F/P1.8,r_NaOH/P0.7,树脂化温度 80℃ 条件下合成的杉木液化物树脂压制的杨木三层胶合板满足I类胶合板强度要求,各项物理力学性能与常规PF树脂压制的板材相当,板材的甲醛释放量为 0.1 mg/L,远低于GB/T 9846-2004《胶合板》中的E₀级要求。     

Polyurethane foams made from liquefied bark‐based polyols

Liquefaction is known to be an effective method for converting biomass into a polyol. However, the relationships between bark liquefaction conditions and properties of the resulting foams are unclear. In this study, polyurethane foams (PUF) were made using bark‐based polyols obtained through liquefaction reactions of bark at two different temperatures (90 and 130°C). Through systematic characterization of the PUFs the influence of the liquefied bark and liquefaction conditions on foam properties could be observed. The bark‐based foams had similar foaming kinetics, thermal stability, and glass transition temperatures compared with the PEG‐based control foam. The bark‐based PUF from the polyol obtained at the higher liquefaction temperature showed comparable specific compressive strength to the PEG‐based control foam. Lastly, both bark foams exhibited a high amount of open‐cell content, with the foam made from the lower temperature liquefied polyol having poor cell morphology. This deviation from the controls in the open‐cell content may explain the lower modulus values observed in the bark PUFs due to the lack of cell membrane elastic stretching as a strengthening mechanism. These results demonstrated the influence of the bark liquefaction conditions on foam properties, thereby providing a better fundamental understanding for the practical application of bark‐based PUFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40599.     

Characterization of polyurethane foams from soybean oil

Modified soy‐based vegetable oil polyols were successfully incorporated as a replacement for conventional polyols to produce flexible slabstock polyurethane foams. The oil was characterized for its hydroxyl value and fatty acid composition. The modified oils had higher hydroxyl values and lower unsaturated acids than regular unmodified oils. Three different modified polyols were used to investigate the reactivity with isocyanates. The effects on the foaming reaction of two different isocyanates, namely TDI and MDI, were investigated. The reactions were also carried out with a mixture of polyols containing synthetic polyols and vegetable oil‐based polyols to delineate the effect of each component. FTIR technique was used to identify the sequence of chemical reactions during the foaming process. The effect of water levels and isocyanate content on the kinetics of the foaming reaction was investigated. Information regarding the formation of hard and soft segments with the varying compositions was obtained. As the water content increased, the amount of the hard segment and urea formation increased in both soy oil polyols and synthetic polyols. Increased synthetic polyols in the mixture increased the rate of reaction and phase mixing due to the availability of primary hydroxyl groups. Scanning electron microscopy (SEM) and small‐angle X‐ray scattering (SAXS) were used to probe the morphology. As the water content increased, the cell size increased. At lower water content a more uniform cell structure was evident and at higher water levels hard domain size increased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3097–3107, 2002     

Properties of phenol‐formaldehyde resins prepared from phenol‐liquefied lignin

In this study, alkaline lignin (AL), dealkaline lignin (DAL), and lignin sulfonate (SL) were liquefied in phenol with sulfuric acid (H₂SO₄) or hydrochloric acid (HCl) as the catalyst. The phenol‐liquefied lignins were used as raw materials to prepare resol‐type phenol‐formaldehyde resins (PF) by reacting with formalin under alkaline conditions. The results show that phenol‐liquefied lignin‐based PF resins had shorter gel time at 135°C and had lower exothermic peak temperature during DSC heat‐scanning than that of normal PF resin. The thermo‐degradation of cured phenol‐liquefied lignin‐based PF resins was divided into four temperature regions, similar to the normal PF resin. When phenol‐liquefied lignin‐based PF resins were used for manufacturing plywood, most of them had the dry, warm water soaked, and repetitive boiling water soaked bonding strength fitting in the request of CNS 1349 standard for Type 1 plywood. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Heterocyclic‐based epoxy‐terminated structural adhesive. II. Curing,adhesive strength,and thermal stability

We studied the curing behavior of heterocyclic‐based epoxy‐terminated resins using diaminodiphenyl ether, diaminodiphenyl sulfone, benzophenone tetracarboxylicdianhydride, and the commercial hardener of Ciba‐Geigy's two‐pack Araldite as curing agents. The adhesive strength of the adhesives was measured by various ASTM methods such as lap‐shear, peel, and cohesive tests on metal–metal, wood–wood, and wood–metal interfaces. All of these results were compared with those of an epoxy resin prepared from bisphenol‐A and epichlorohydrin resin with an epoxy equivalent value of 0.519. The thermal stability of both the virgin resin and its cured form was also studied by thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3520–3526, 2002     

Foaming of rigid PVC/wood‐flour composites through a continuous extrusion process

The effects of chemical foaming agent (CFA) types (endothermic versus exothermic) and concentrations as well as the influence of all‐acrylic processing aid on the density and cell morphology of extrusion‐foamed neat rigid PVC and rigid PVC/wood‐flour composites were studied. Regardless of the CFA type, the density reduction of foamed rigid PVC/wood‐flour composites was not influenced by the CFA content. The cell size, however, was affected by the CFA type, independent of CFA content. Exothermic foaming agent produced foamed samples with smaller average cell sizes compared to those of endothermic counterparts. The experimental results indicate that the addition of an all‐acrylic processing aid in the formulation of rigid PVC/wood‐flour composite foams provides not only the ability to achieve density comparable to that achieved in the neat rigid PVC foams, but also the potential of producing rigid PVC/wood‐flour composite foams without using any chemical foaming agents.