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     

Cure Characteristics of Phenol-Formaldehyde Resin Catalyzed with Ba(OH)2

Phenol-formaldehyde resins are high performance wood adhesives, and are also used to impregnate base papers which are manufactured high-pressure laminates applied in furniture and interior decoration. In this investigation, PF resins catalyzed with Ba(OH)₂ were studied. Both Ba(OH)₂ content and F/P molar ratio were found to influence the cure rate. The cure rate of the Ba(OH)₂ catalyzed PF resin was faster by 50% than that of ordinary PF resin at 150°C. The DSC results showed that the Ba(OH)₂ catalyzed PF resin was cured at a lower temperature than the ordinary PF resin. And the IR results showed that the Ba(OH)₂ catalyzed PF resin has higher degree of ortho-position coupling.     

Improvement of UF/fiberglass mat properties used in roofing shingles through emulsion polymers and nanoclay addition

Modification of urea–formaldehyde (UF) resin binder for making fiberglass mats was aimed as a route to enhance its brittleness and improve its mechanical properties. The UF resin modifiers were chosen among pure acrylate emulsion polymers having different glass transition temperatures (T _g). Blends of 10% w/w based on dry modifiers and UF resin were prepared. The most effective modifier was chosen and 4 wt% of nanoclay was added to the UF resin for improvement of its mechanical properties. Morphologies of the fractured surface of the UF-modified films were investigated by scanning electron microscopy (SEM). Coarser texture of the fractured surface was regarded as an increased toughness of the modified UF resin. Investigation of gel time at 100 °C on various modified urea–formaldehyde resins showed that the gel time of the modified UF resins generally decreases with adding polymeric emulsions. It is decreased further when less film forming latex (higher T _g) is used in UF resin. Less film formation on the other hand, promotes easier water release during UF resin curing. Tensile and tear strength of the fiberglass mat composites have been increased up to 300 and 50%, respectively, while additional increase of 33% in tensile strength was obtained when nanoclay was incorporated into the composites. X-ray diffraction (XRD) analysis and Si-mapping through SEM were employed in order to show the dispersion and the distribution of nanoclay in the composites, respectively. The disappearance of the peak at 2θ = 7.22 confirmed the exfoliation of the employed nanoclay.     

Properties of compression‐molded plates made from wood powders impregnated with liquefied wood‐based novolak‐type phenol‐formaldehyde resins

Novolak‐type phenol‐formaldehyde (PF) resins with solution form were prepared by reacting phenol‐liquefied Cryptomeria japonica (Japanese cedar) wood with formalin in the presence of methanol. Wood powders of Albizzia falcate (Malacca albizzia) impregnated with these resins were air dried followed by an oven‐dried at 60°C. DSC analysis showed the PF resin existing in wood powders could be melted, and could be cured if hexamine was mixed and heated at high temperature. Compression‐molded plates made with PF resin impregnated woods had a high degree of curing reaction. However, compression‐molded plates hot‐pressed at 180°C for 8 min or 200°C for 5 min had better internal bonding strength and dimensional stability than others. Premixing hexamine with PF resin and impregnating into wood powders simultaneously could enhance the reactivity of PF resin, but it was not useful for improving the properties of compression‐molded plates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde resin

The aim of this research was to investigate the physical and mechanical properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde (LPF) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid, and then, various contents of modified lignins (10, 15, and 20 wt%) were added as a substitute of phenol in phenol–formaldehyde (PF) resin synthesis. The properties of the synthesized resin were compared with those of a control PF resin. The changes in curing behavior of the resins prepared were analyzed by differential scanning calorimetry (DSC). The physical properties of the resins prepared, as well as the water absorption, thickness swelling, shear strength, and formaldehyde emission of the plywood panels bonded with these adhesives, were measured according to standard methods. DSC analysis indicated that in comparison with PF resins, curing of the LPF resin occurred at lower temperatures. The physical properties of the synthesized resins indicated that viscosity and solid content increased, while gel time and density decreased by addition of treated lignin to the PF resin. Although the panels containing resins with modified lignin yielded low formaldehyde emission, their dimensional stability was worse than those bonded with a commercial PF adhesive. The plywood prepared using IL-treated lignin PF resins has shear strength, which satisfy the requirements of the relevant standards specifications and significantly better than that of panels prepared with the control PF resin. The mechanical properties of the panels could be significantly enhanced with increased percentage of treated lignin content from 0 to 20 wt%.     

Star-shaped silicon-containing arylacetylene resin based on a one-pot synthesis using zinc powder catalysis with improved processing and thermal properties

Herein, reporting a simple, sustainable, and cost-effective chemical synthesis of a star-shaped silicon-containing arylacetylene (SSA) resin via a one-pot process using zinc powder as a catalyst. The as-prepared viscous liquid resins exhibited moderate rheological behavior. The thermal curing temperature was determined to be 203 °C using differential scanning calorimetry, which is much lower than that reported for polyimide and phthalonitrile (>300 °C), indicating the SSA resins are suitable for processing at a lower temperature. Thermogravimetric analysis also revealed the excellent thermal stability and extremely high carbon residue of the cured SSA resin (the temperature at 5% mass loss and residual yield at 800 °C under N₂ were 654 °C and 93%, respectively). The results showed the excellent processability and thermal stability of SSA resin. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48248.     

A novel type of Si‐containing acrylic resins: Synthesis,characterization, and film properties

A novel type of Si‐containing acrylic resins was prepared by two steps and investigated their usage as surface coatings materials. At first a reactive polysiloxane intermediate Z‐6018 was reacted with 2‐hydroxyethyl methacrylate (HEMA) in toluene at 110°C under N₂ atmosphere. After the condensation reaction was stopped, reacted with different acrylic ester monomers such as ethyl acrylate (EA) and methyl methacrylate (MMA) at different mole ratio (1/3 and 1/4) by the free radical addition polymerization. Structures of Si‐containing acrylic resins were characterized by Fourier Transform Infrared Spectrometer (FTIR) and thermal properties of these resins were investigated by thermogravimetric analysis and differential scanning calorimetry DSC techniques. Surface coating properties of the films prepared from these resin were also determined. The results showed that all films are flexible, glossy or semi gloss and have excellent drying and adhesion properties. All films also exhibit abrasion resistances moderately. Water resistance of the films was generally modified by cured in oven and alkaline resistance of the films prepared from resins containing ethyl acrylate units are excellent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Influence of Resin Molecular Weight on Curing and Thermal Degradation of Plywood Made From Phenolic Prepreg Palm Veneers

The present work evaluates curing and the thermal behavior of different molecular weight phenol formaldehyde (PF) resins used to prepare PF prepreg oil palm stem veneers. The physical properties (solid contents, gelation time, pH, and viscosity) of PF resins were determined. The molecular weight of resins was characterized by gel permeation chromatography, whilst thermal properties were determined by differential scanning calorimetry and thermogravimetric analyses. The average molecular weight of PF resins were 526 g/mole (low), 1889 g/mole (medium), and 5178 g/mole (control - commercial). Among the resins, medium (MMwPF) gives better thermal stability with a retained weight of 48.9% at 300°C. High (Commercial PF) had a low decomposition temperature (109.3°C) which occurred within 11 min. Both low (LMwPF) and MMwPF started to melt at ≥120°C. Based on strength and shear values, phenolic prepreg palm veneers can be prepared using either low or medium molecular weight PF but with varying results. In all cases, the mechanical properties of palm plywood made from PF prepreg veneers were superior to those made from PF-bonded plywood using the commercial process.     

Synthesis and characterization of thermosetting polyacetylene-terminated silicone resins

A novel polyacetylene-terminated silicone (PTS) resins possessing low curing temperature and high heat resistance has been prepared by Grignard reaction using m-diacetylenylbenzene (DEB), 1,3,5-triacetylenylbenzene(TEB), and dichlorosilane as original materials. The reaction of the functional groups was characterized by in situ Fourier transform infrared spectrometer. The experimental results indicated that Si─H and C≡CH bonds are almost exclusively involved in the crosslinking reaction, while ─C≡C─ bonds only partially react. Further, Si─H and C≡CH bonds can participate in the curing reaction at relatively low temperatures, but ─C≡C─ bonds require higher temperature, indicating the higher activity of Si─H and C≡CH bonds than ─C≡C─ bonds. As determined by differential scanning calorimetry, PTS resins have low peak exothermic temperature at 184.5 °C, which is lower than MSP resin (~ 210 °C); in addition, rheological test showed that PTS resins have a very wide processing window from 40 to 163.3 °C, indicating that the PTS resins have excellent processability with a low curing temperature and wide processing window. What is more, TGA results of thermal-cured PTS resins revealed that T_d5 (5% weight loss temperature) of PTS-H10 reached the highest of 684.4 °C. Compared with PTS-H0 resin, there is an increase of 124.2 °C and the remarkably increased heat resistance correlated with a higher m-DEB input ratio. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48783.     

Investigation of novel polytriazole resins

2,4,6-Tri(4-propargyloxy-phenyl)pyridine(POPP) was made from 2,4,6-tri (4-hydroxyphenyl)pyridine(HPP) and propargyl bromide. The chemical structures of POPP and HPP were well characterized by means of FTIR, ¹H-NMR, ¹³C-NMR, and elemental analysis. Novel polytriazole resins (P-PTA resins) were prepared from POPP and azide compounds via 1, 3-dipolar cycloaddition reaction and characterized by solubility, FTIR, DSC, and TGA analyses. The P-PTA resins show good solubility in common solvents. The resins could be cured at 80 °C. The glass transition temperature (T_g) and the 5% weight loss temperature (T_d5) of the cured P-PTA-33 resin arrive at 310 and 365 °C in nitrogen atmosphere, respectively.     

Studies on the thermal and curing behavior of polyimide blends

Blends of thermosetting (Thermid MC-600 and Thermid FA-700) and thermoplastic (UL-TEM 1000) polyimide resins with different compositions were prepared. Curing and thermal behavior of the blends were investigated using differential scanning calorimetry and dynamic thermogravimetry in a nitrogen atmosphere. The peak exotherm temperature increased with increasing amount of thermoplastic resin, whereas the heat of polymerization decreased. The electrical characteristics of the blends were also investigated using a dielectric analyzer. Dynamic as well as isothermal scans were recorded. Ionic conductivity, permittivity, and the loss factor were measured as a function of temperature at various frequencies. These results showed the complete curing of the resins having 50% Ultem at 225°C in 1 h, whereas Thermid MC-600 required a postcuring step to observe fully cured resins. A marginal decrease in thermal stability was observed on blending. © 1994 John Wiley & Sons, Inc.     

A Novel Type of Organo Clay Containing Alkyd-Melamine Formaldehyde Resins

In this study, organo clay-modified alkyd resins were synthesized and these modified alkyd resins were cured with different ratios of melamine formaldehyde resin for the first time. Alkyd resins were blended with 30% and 40% of a commercial melamine-formaldehyde resin. Alkyd-melamine formaldehyde resin films were cured at 140°C for 2 h in an oven. The effect of organo clay addition on the physical and chemical film properties was investigated. These surface coating properties of the resins enhanced with amount of organo clay up to 2–3%. These resins are suitable for manufacturing of high-performance industrial baking enamels.     

Study of hybrid isocyanate and high-mono-hydroxymethyl urea content urea-formaldehyde resins

Based on the difference in the reaction rate of different groups of urea-formaldehyde resins and isocyanate resins, this study designed two different urea-formaldehyde resins: a normal urea-formaldehyde resin (UF) and one with high mono-hydroxymethylurea content (UF*) to react with polymeric methylene diphenyl diisocyanate (pMDI) resin. The difference in mono- and di-hydroxymethyl urea content between UF and UF* resins was analyzed by nuclear magnetic resonance (NMR) spectroscopy, and results showed that the mono-hydroxymethyl urea content of the UF* resin was much higher than that of the conventional UF resin. The fourier transform infrared spectrometer (FTIR) analysis of differences between UF* and UF resin showed that the UF* process did not change the main structure of the conventional urea formaldehyde resin. Differential scanning calorimeter (DSC) analysis showed that the curing temperature of the hybrid UF*-pMDI resin was reduced 27.3°C compared to that of the UF-pMDI resin. When these hybrid resins were used to bond plywood respectively, test results showed that the UF*-pMDI resin improved the dry and wet bonding strength by 2.6% and 3.9%, respectively, compared with the UF-pMDI resin under the condition of hot pressing time (3 min) and temperature (140°C), meeting the requirement of Chinese standard of GB/T 9846–2015 for Class III board. This study provides a new path for further improving the performance and design of hybrid resins based on isocyanate and urea-formaldehyde resin.     

Study on the copolymers of silicon-containing arylacetylene resin and acetylene-functional benzoxazine

An acetylene-functional benzoxazine (AFBEN) which was used to modify poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) was synthesized by a solventless procedure. The modified resins (DMSEPE/AFBEN) were obtained by blending DMSEPE and AFBEN in different amount. The thermopolymerization of DMSEPE/AFBEN resins were investigated by DSC technique. The dynamic mechanical analysis showed that the storage modulus (E) of the cured DMSEPE/AFBEN resin containing less than 30 wt% AFBEN did not decrease at the temperature lower than 500 °C. When the AFBEN loading increased from 20 to 100 wt%, a decrease in glass transition temperature from 523 to 342 °C was observed. The thermal stability of the cured DMSEPE/AFBEN resins was determined by thermogravimetric analysis (TGA) in N₂ and air. The TGA results showed the cured DMSEPE/AFBEN resins had good thermal stability. The carbon fiber (T700) reinforced DMSEPE/AFBEN composites exhibited excellent mechanical properties (flexural strength: 1,694 MPa) at room temperature and high strength remaining of 76% at 300 °C.     

H2O2 as a modifier of phenol–formaldehyde resin used in the production of particleboards

The purpose of the research was to study the influence of H₂O₂ on the properties of fluid phenolic (PF) resin, the curing process, the cured resin structure, and the properties of the particleboards produced with its use. The influence of added H₂O₂ on resin usability at 20°C, on the gel time of the modified PF resin in the temperature range 110–140°C, and on the activation energy of the curing process were studied. Also, the structure of the cured resin was examined by Fourier transform infrared spectroscopy. Finally, the properties of the obtained particleboards were determined. The results indicate that the H₂O₂ modification leads to greater reactivity of the phenolic resin and increases the mechanical properties of particleboards. In contrast, there is no significant influence of H₂O₂ on the water resistance of the particleboards. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3084–3092, 2003     

Differential scanning calorimetry and dynamic mechanical analysis of amine-modified urea–formaldehyde adhesives

Urea–formaldehyde (UF) resins are susceptible to stress rupture and hydrolytic degradation, particularly under cyclic moisture or warm, humid conditions. Modification of UF resins with flexible di- and trifunctional amines reduces this problem. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to study the thermal behavior of modified and unmodified adhesives to identify the physical and morphological factors responsible for the improved performance. A UF resin modified by incorporating urea–capped poly(propyleneoxidetriamine) during resin synthesis exhibited a higher cure rate and greater cure exotherm than the unmodified resin. Resins cured with a hexamethylenediamine hydrochloride curing agent had slower cure rates than those cured with NH₄Cl. DMA behavior indicated that modified adhesives were more fully cured and had a more homogeneous crosslink density than unmodified adhesives. DMA behavior changed with storage of specimens at 23°C and 50% relative humidity, after previous heating for approximately 20 min at 105°C to 110°C. The initial changes were postulated to occur because of physical aging (increase in density) and continued cure. These were followed by physical breakdown (microcracking) and possibly cure reversion. © 1995 John Wiley & Sons, Inc.     

The synthesis of a secondary branched epoxy-modified silicone resin and its application at low temperature

To enhance the fracture toughness of epoxy resin at low temperature, a secondary branched epoxy-terminated silicone resin (ESR-6) was synthesized and incorporated into bisphenol A epoxy resin at different contents. The structure of ESR-6 was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance (¹H NMR), and the fracture surface of the composites was observed by scanning electron microscope (SEM) and atomic force microscopy. At room temperature and − 70°C, the maximum values of elongation at break were 15.78% and 12.55% with 10 wt% ESR. Compared with those of neat epoxy resin, the values of elongation at break of the composite were increased by 50.86% and 36.12%. The results of dynamic mechanical analysis also showed that the toughness of the modified resin had been improved. The SEM images of the fracture surfaces suggested that the fracture mode of the modified resin changed from brittle one to plastic one because of the addition of ESR-6, which further confirmed the toughening effect of ESR-6. These research results may provide a new strategy for enhancing the low-temperature toughness of epoxy resins.     

Synthesis of novel acrylic modified water reducible alkyd resin: Investigation of acrylic copolymer ratio effect on film properties and thermal behaviors

New four‐component water reducible acrylic modified alkyd resins that are based on 1,3‐propanediol and contain different ratios of acrylic copolymer (AC) were synthesized by using a novel four‐stage fatty acid method. The final content of solids in the water reducible acrylic modified alkyd resins was 60% by weight. After the modified alkyd resin films were cured at 150°C for 1 h, it was observed that the use of AC as the modifier component had improved their physical and chemical surface coating properties and thermal behaviors. Experimental results show that the optimum AC ratio is 40% of the equivalent amount of AC to alkyd resin. Low‐volatile organic compounds (VOC) content water reducible acrylic modified alkyd resins yielded soft and flexible films with high chemical/thermal resistance, suitable for manufacturing of surface coating binders. POLYM. ENG. SCI., 56:947–954, 2016. © 2016 Society of Plastics Engineers     

A high-performance bismaleimide resin with good processing characteristics

A new bismaleimide (BMI) resin system, designated 4504, with excellent heat resistance and good mechanical properties for advanced composites was developed. The 4504 resin was made up of 4,4′-bismaleimidodiphenyl methane, diallyl bisphenol A, and desirable catalysts. The reactivity of 4504 was investigated by gel characteristics and differential scanning calorimetry (DSC). Data showed that 4504 had a long work life under 100°C, but would gel within 7 min or 40 s at 140 or 160°C, respectively. The glass transition temperature (T_g) and heat-deflection temperature (HDT) of the cured 4504 resin were 315 and 290°C, respectively, which were much higher than the postcure temperature (200°C). In addition, the cured resin is also tough. Thermogravimetric analysis (TGA) in a nitrogen atmosphere revealed that the neat resin was stable up to 450°C; its char yield at 700°C under anaerobic conditions was 29.4%. Carbon fiber T300 laminates based on 4504 were prepared and characterized. In the case of short-beam (SBS) strength, when tested at 230°C, 51% of the original room temperature strength was retained. © 1996 John Wiley & Sons, Inc.     

Preparation and properties of dipropargyl ether of bisphenol A‐modified bismaleimide resins and composites

A kind of modified bismaleimide resin, with good heat resistance and processing properties for advanced composites, was developed. The modifier, dipropargyl ether of bisphenol A (DPBPA), was prepared by a phase‐transfer catalyzing procedure, characterized by FTIR, ¹H NMR, and elementary analysis, and used to modify 4,4′‐bismaleimidodiphenylmethane (BMDPM). The thermopolymerization of a DPBPA‐modified BMDPM resin was followed up by FTIR. The curing of the resin was investigated by differential scanning calorimeter and gelation characterization. The relation of viscosity and temperature was used to characterize the processability of the resin. The results of DMA analysis showed that the cured DPBPA‐modified BMDPM resins had a glass transition temperature higher than 320°C. The carbon fiber (T700) reinforced composites showed excellent flexural properties at ambient temperature and at 250°C. DPBPA could effectively improve mechanical properties without deteriorating heat resistance of the BMDPM resin a lot. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers