Synthesis,Characterization, and Composite Properties of Casein Incorporated p-Aminophenol-Urea-Formaldehyde Copolymers

ABSTRACT

Modified Urea-formaldehyde (UF) thermosetting resin, containing casein and p-amino phenol has been synthesized by polycondensation of urea, casein, and formaldehyde in the presence of varying proportion of p-aminophenol under alkaline condition. All the prepared resins were characterized by free-formaldehyde content, free-phenol content, viscosity measurements, and infrared spectroscopy (IR). Their curing kinetics were studied isothermally and also by Differential Scanning Calorimetry (DSC) on dynamic run. The resin samples were cured isothermally at 120°C using two different curing agents, that is p-toluene sulphonic acid (PTS) and hexamine, to understand the curing behavior of novel resin samples. The cured resins were characterized by IR and thermogravimetric analysis (TGA). The resin samples were employed for the fabrication of glass fiber and jute fiber reinforced composites respectively by maintaining 2:3 and 3:2 proportion of resin: reinforcement. The prepared composites were tested for their mechanical properties and resistance toward various chemicals.     

Preparation,characterization, and composites from low formaldehyde emission urea–formaldehyde–casein copolymer

A modified urea–formaldehyde resin was synthesized by the condensation of urea and formaldehyde in the presence of varying proportions of casein up to 25% (w/w) of urea under alkaline conditions. All the prepared resins were characterized by free‐formaldehyde content, viscosity measurements, and number‐average molecular weight determination by vapor pressure osmometry and IR spectroscopy. Their curing kinetics were studied isothermally and by differential scanning calorimetry on dynamic runs. The resin samples were cured isothermally at 60, 80, and 100°C using ammonium chloride and hydroxylamine hydrochloride as curing agents. The isothermal curing study was also performed with hexamine at 120°C. Cured resins were characterized by IR and thermogravimetric analysis. The resin samples were employed for the fabrication of glass fiber and jute fiber reinforced composites by maintaining 2 : 3 and 3 : 2 proportions of resin/reinforcement, respectively. The prepared composites were tested for their mechanical properties and resistance toward various chemicals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 531–537, 2005     

Engineering biomass into formaldehyde‐free phenolic resin for composite materials

The use of formaldehyde to prepare phenol‐formaldehyde (PF) resins is one of the primary challenges for the world‐wide PF industry with respect to both sustainability and human health. This study reports a novel one‐pot synthesis process for phenol‐5‐hydroxymethylfurfural (PHMF) resin as a formaldehyde‐free phenolic resin using phenol and glucose, and the curing of the phenolic resin with a green curing agent organosolv lignin (OL) or Kraft lignin (KL). Evidenced by ¹³C NMR, the curing mechanism involves alkylation reaction between the hydoxyalkyl groups of lignin and the ortho‐ and para‐carbon of PHMF phenolic hydroxyl group. The curing kinetics was studied using differential scanning calorimetry and the kinetic parameters were obtained. The OL/KL cured PHMF resins were tested in terms of thermal stability, and mechanical properties for their applications in fiberglass reinforced composite materials. The results obtained demonstrated that OL/KL can be promising curing agents for the PHMF resins. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1275–1283, 2015     

Synthesis–structure–performance relationship of cocondensed phenol–urea–formaldehyde resins by MALDI‐ToF and 13C NMR

Matrix assisted laser desorption ionization time of flight (MALDI‐ToF) mass spectrometry has consistently confirmed on a number of PUF resins that phenol–urea cocondensates exist in phenol–urea–formaldehyde (PUF) resins. A noticeable proportion of methylene‐linked phenol to urea cocondensates were detected in all the PUF resins tried, alongside methylene bridges connecting phenol to phenol and urea to urea. The PUF, PF, and UF oligomers formed were identified. Variations of the PUF preparation procedure did always yield a certain proportion of the mixed phenol to urea cocondensates. Their relative proportion was determined and related the synthesis procedure used. Comparison of the MALDI‐ToF results with a ¹³C NMR investigation showed that in a real PUF resin in which phenol to urea cocondensates were identified the methylene bridge NMR signal at 44 ppm, characteristic of phenol to urea unsubstituted model compound cocondensates, does not appear at all. This confirmed that this peak cannot be taken as an indication of the existence of phenol and urea condensation under actual resin preparation conditions. The peak indicating cocondensation in PUF resins in which the phenolic nuclei and urea are substituted appears instead at 54.7–55.0 ppm. Thermomechanical analysis has again confirmed that the resin gel times greatly accelerates with increasing urea molar content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A Study on Composites from Casein Modified Melamine-Formaldehyde Resin

Amino resins are used for various applications such as decorative plastic plates, decorative wood boards, particle boards, leather tanning, foam, coating, and molding materials. In the present work, it was planned to prepare modified melamine-formaldehyde resin by incorporating casein. The intended melamine-formaldehyde-casein (MFC) resin samples were prepared under alkaline condition with an 1:3 melamine: formaldehyde ratio. Casein was incorporated in varying proportions (up to 25% w/w of melamine content) at 85–90°C. The samples were characterized by viscosity measurement and vapor pressure osmometry (VPO). The resin samples were cured isothermally at 60°C using ammonium chloride as well as hydroxylamine hydrochloride and at 120°C using hexamine as the curing agents. Jute fabric (JFRC) and glass fabric reinforced composites (GFRC) were produced by maintaining 60:40 and 40:60 proportion of resin to reinforcement materials, respectively. The laminates thus formed were characterized for their mechanical properties and chemical resistance.     

Mahua‐oil‐based resins for the high‐temperature curing of fly ash coatings

We attempted to prepare medium‐oil‐length glycerol alkyds based on Mahua oil. Fatty acids were isolated from the oil and used in the preparation of alkyds by the fusion method. The resins were characterized by IR spectroscopic analysis. The physicochemical and film properties of these resins were also studied. IR analysis of the resins revealed the formation of phthalate esters showing characteristic peaks at 1720 cm^?1. The resin was modified with melamine formaldehyde, which cured at high temperatures. Alternatively, the resin was made to air dry with ester gum, and the curing behavior was studied. The suitability of these resins for high‐temperature curing fly ash coating applications was established. Coatings were formulated with these resins and with 40% fly ash as an extender. The coatings were characterized by standard techniques, particularly for their anticorrosive and antiabrasive properties. Resistance to corrosion was evaluated in humidity and in salt‐spray conditions. We conducted a high‐stress (two‐body) abrasion test to test the abrasive wear resistance of the coatings. The Mahua‐oil‐resin‐based fly ash coatings were suitable for application in moderately corrosive and abrasive environments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 110–120, 2003     

13C‐NMR study on the structure of phenol‐urea‐formaldehyde resins prepared by methylolureas and phenol

Phenol‐urea‐formaldehyde (PUF) resins were synthesized by reacting mixture of methylolureas (MMU), phenol, and formaldehyde. The structure of PUF cocondensed resins at different stages of reaction were analyzed by liquid ¹³C nuclear magnetic resonance (NMR) spectroscopy. The liquid ¹³C‐NMR analysis indicated that methylolureas had the dominant content in MMU with the reaction between urea and formaldehyde under the alkaline condition. The PUF cocondensed resins had no free formaldehyde. methylolureas were well incorporated into the cocondensed resins by reacting with phenolic units to form cocondensed methylene bridges. The second formaldehyde influenced the further reaction and the structure of the PUF resins. The resins with the prepared method of PUFB possessed relatively high degree of polymerization and low proportion of unreacted methylol groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fast advancement and hardening acceleration of low‐condensation alkaline PF resins by esters and copolymerized urea

Low‐condensation phenol‐formaldehyde (PF) resins coreacted under alkaline conditions with up to 42% molar urea on phenol during resin preparation yielded PUF resins capable of faster hardening times than equivalent pure PF resins prepared under identical conditions and presented better performance than the latter. The water resistance of the PUF resins prepared seemed comparable to pure PF resins when used as adhesives for wood particleboard. Part of the urea was found by ¹³C‐NMR to be copolymerized to yield the alkaline PUF resin; whereas, especially at the higher levels of urea addition, unreacted urea was still present in the resin. Increase of the initial formaldehyde to phenol molar ratio decreased considerably the proportion of unreacted urea and increased the proportion of PUF resin. A coreaction scheme of phenolic and aminoplastic methylol groups with reactive phenol and urea sites based on previous model compounds work has been proposed, copolymerized urea functioning as a prebranching molecule in the forming, hardened resin network. The PUF resins prepared were capable of further noticeable curing acceleration by addition of ester accelerators; namely, glycerol triacetate (triacetin), to reach gel times as fast as those characteristic of catalyzed aminoplastic resins, but at wet strength values characteristic of exterior PF resins. Synergy between the relative amounts of copolymerized urea and ester accelerator was very noticeable at the lower levels of the two parameters, but this effect decreased in intensity toward the higher percentages of urea and triacetin. ¹³C‐NMR assignements of the relevant peaks of the PUF resins are reported and compared with what has been reported in the literature for mixed, coreacted model compounds and pure PF and urea‐formaldehyde (UF) resins. The relative performance of the different PUF resins prepared was checked under different conditions by thermomechanical analysis (TMA) and by preparation of wood particleboard, and the capability of the accelerated PUF resins to achieve press times as fast as those of aminoplastic (UF and others) resins was confirmed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 359–378, 1999     

Phenol–formaldehyde‐type resins made from phenol‐liquefied wood for the bonding of particleboard

Liquefaction of southern pine wood in phenol in 30–40 : 70–60 weight ratios resulted in homogeneous liquefied materials, which were directly used to synthesize phenol–formaldehyde (PF)‐type resins. The synthesized resins showed good physical and handling properties: low viscosity, stability for storage and transportation, and resin applicable by a common sprayer. Particleboard panels bonded with the synthesized resins showed promising physical properties and significantly lower formaldehyde emission values than those bonded with the urea–formaldehyde resin control. One deficiency observed for the synthesized resins was lower internal bond values, which might be overcome the use of a hot‐stacking procedure. Overall, the process of wood liquefaction with limited amounts of phenol as a solvent was shown to have the potential of providing practical, low‐cost PF‐type resins with very low formaldehyde emission potentials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Use of a methylolated softwood ammonium lignosulfonate as partial substitute of phenol in resol resins manufacture

The synthesis of lignin‐phenol‐formaldehyde (LPF) was studied to determine its optimum operating conditions. The lignin proposed as phenol substitute has been the softwood ammonium lignosulfonate. The resin synthesis was optimized by varying the methylolated lignosulfonate content, 18–52%; the sodium hydroxide to phenol‐modified lignosulfonate molar ratio, 0.3–0.94; and the formaldehyde to phenol‐modified lignosulfonate molar ratio, 1.1–3.5. The parameters employed in the characterization of LPF resins were free phenol, free formaldehyde, gel time, alkaline number, viscosity, pH, solid content, and chemical structure changes. The properties of LPF resin comply with the requirements for its utilization in plywood manufacture. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 643–650, 2004     

Ion exchange resins from phenol/formaldehyde resin‐modified lignin

Phenol/formaldehyde resin, commonly sulfonated, is used as ion exchanger. Lignin, which is the phenolic polymer matrix in wood, was isolated from olive stone biomass by alkaline hydrolysis of weak ether bonds (Kraft lignin, KRL). It was then hydroxymethylated (KRLH) with an aqueous solution of formaldehyde. Novolac resin (N) was synthesized from phenol and formaldehyde under acidic conditions. KRL or KRLH was incorporated into phenol/formaldehyde during polymerization (N‐KRL, N‐KRLH). The products of polymerization (N, N‐KRL and N‐KRLH) were sulfonated with concentrated H₂SO₄ (1:3 w/w as typical proportion according to literature or 1:6 w/w as an excess of H₂SO₄) and then cross‐linked with formaldehyde. The different products were characterized by IR spectroscopy, swelling in ethanol, acetone and in an aqueous solution of 1 N NaOH. The ion‐exchange capacity, the moisture retention capacity and the titration curves of the sulfonated and cured products were determined. The ion‐exchange capacity and the uptake of metal ions (mainly Co²⁺ and Cu²⁺) detected by atomic absorption spectroscopy, on the sulfonated materials, prepared in an excess of H₂SO₄, is higher for N‐KRL and N‐KRLH than for N and it takes place at the same rate or faster. The latter shows a medium acidic behaviour according to the titration curves, in contrast with the sulfonated N‐KRLH and N‐KRL which show a strongly acidic behaviour. © 2001 Society of Chemical Industry     

Novel nitrogen‐containing epoxy resin. I. Synthetic kinetics

A novel nitrogen‐containing epoxy resin was synthesized by two steps: (1) condensation reaction between xyleneformaldehyde resin and phenol, to obtain thermoplastic xylenephenolformaldehyde (XPF) resin; and (2) addition reaction between XPF resin and triglycidyl isocryanurate (TGIC). The synthetic kinetics of XPF resin were intensively investigated by gel permeation chromatography (GPC). The results showed that XPF resin, with different molecular weights and low content of free phenol, could be obtained by changing the reaction conditions. The kinetics of reaction between XPF resin and TGIC was monitored by GPC and epoxy value titration. The results showed that the percentage conversion of TGIC was >85% within 60 min at 140°C and the epoxy value, about 0.3–0.4 mol/100 g, varied with the reaction conditions. This novel epoxy resin exhibited good stability of storage and could be used as a basic resin for making prepreg and laminate. The structures of XPF and XT resins were characterized by IR and ¹H‐NMR spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96:723–731, 2005     

Determination of the formaldehyde‐to‐phenol molar ratios of resol resins by infrared spectroscopy and multivariate analysis

The formaldehyde/phenol (F/P) ratios of resol resins were successfully predicted by the recording of infrared (IR) spectra of both calibration and analyzed resins and by a multivariate analysis technique. In the creation of applicable models, the best correlating IR spectral areas were found between 1800 and 700 cm^?1. The positive effects of the increasing replicates and the omission of first‐derivative preprocessing on model quality were proven by systematic testing. The characteristic statistical parameters were acceptable when the resin was similar to the calibration resins. Although the calibration samples had narrow F/P molar ratios (2.00–2.40), or a particular urea content or alkalinity, the best calibration model could also successfully predict the F/P molar ratios of resins with greater F/P ratios, higher urea contents, and lower alkalinity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3582–3586, 2003     

Controlled synthesis of high‐ortho‐substitution phenol–formaldehyde resins

The relationship between the use of 19 kinds of metal catalysts and the proportion of ortho–ortho links of novolac resins was studied. The proportion of ortho–ortho links of novolac resins was characterized with Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR. The effects of different catalysts and different reaction conditions, such as the molar ratio of phenol to formaldehyde, the pH value of the reaction, and the reaction time, were examined. Phenol–formaldehyde resins were synthesized with a certain proportion of the ortho position through the adjustment of the reaction conditions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 652–658, 2005     

多聚甲醛与苯酚物质的量比对可发性甲阶酚醛树脂性能的影响

采用多聚甲醛代替37%的甲醛溶液,在20%NaOH水溶液催化下与苯酚逐步加成聚合,合成了可发性甲阶酚醛树脂。研究了多聚甲醛与苯酚物质的量比(F/P)对合成树脂固含量、粘度、游离苯酚、游离甲醛、凝胶时间、分子结构、分子质量、树脂热性能及泡沫性能的影响。结果表明,F/P值为1.8时,可得到性能优良成本较低的可发性甲阶酚醛树脂,树脂粘度1.4 Pa.s,游离甲醛质量分数1.17%,游离苯酚质量分数6.72%,羟甲基指数1.41,树脂分子质量在240左右,耐热性较好。     

Development and characterization of a wood adhesive using bagasse lignin

Bagasse is spent fiber left after extraction of sugar. It is mainly used as a fuel to concentrate sugarcane juice. In the present work, the possibility of preparing wood adhesives from bagasse has been explored. The parameters for the preparation of a lignin phenol formaldehyde (LPF) adhesive, (lignin concentration, formaldehyde to phenol molar ratio, catalyst concentration, reaction time and reaction temperature) have been optimized. It was found that up to 50% of phenol can be substituted by bagasse lignin to give LPF wood adhesive having better bonding strength in comparison to a control phenol formaldehyde (CPF) wood adhesive. Prepared resins were characterized using IR, DSC and TGA. IR spectra of LPF resin showed structural similarity with CPF resin. Thermal stability of LPF resin was found to be lower as compared to CPF resin. DSC studies reveal a lower curing temperature for LPF adhesive in comparison to CPF adhesive. A shelf-life study reveals that LPF exhibits consistent behavior as compared to CPF in respect to adhesive strength.     

氯化铵对酚醛甲阶树脂固化速率和游离甲醛含量的影响

针对酚醛树脂的固化问题,以MPF甲阶树脂为对象,酸性盐氯化铵为酸度调节剂,研究加入氯化铵后体系固化时间和游离甲醛的变化情况,并探讨了氯化铵添加量对它们的影响。结果显示,氯化铵完全可以作为酚醛甲阶树脂的固化剂；加入少量氯化铵时,固化速度就明显加快；氯化铵的加入量在0．6%～1．2%,固化时间和游离甲醛含量的减少都很明显；当氯化铵的添加量继续增加,游离甲醛含量继续减少,但对固化时同的影响很小。通过对游离甲醛的分析,确定甲醛随氯化铵添加量的变化率为0．4～0．6。     

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。     

Synthesis,characterization, and application of new low‐cost ion exchangers

This paper represents a simple method for preparing and characterizing of low‐cost ion exchangers of sulfonated carbon prepared from Terminalia Chebula‐Retz., (family–combretaceae) as a source of cheap plant material blended with phenol‐formaldehyde as a crosslinking agent. The prepared ion exchange resins (IERs) are characterized by infrared (IR) spectral and thermal studies. All the important physicochemical properties of the ion exchangers have been determined. The synthesized resins have cation exchange capacity upto 1.84 mmol g^?1. The rational thermodynamic equilibrium constant (ln K) are calculated for H⁺ and Zn²⁺ exchanges on the resin having various amount of sulfonated Terminalia Chebula Retz. carbon (STCC). The thermodynamic parameters were calculated, and suitable explanations are given. It is concluded from the present study that PFR sample could be blended with 20% (w/w) of STCC, without affecting its physicochemical, spectral, and thermal properties. Hence blending with STCC will definitely lower the cost of the ion exchange resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4104–4113, 2006     

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