O-cresol Formaldehyde Epoxy Resin Research Articles

Fabrication and curing properties of o-cresol formaldehyde epoxy resin with reversible cross-links by dynamic boronic ester bonds

Conventional cured o-Cresol Formaldehyde Epoxy Resin (o-CFER) with permanent crosslink network is relatively stiff, brittle, and unrecyclable. In order to overcome these defects, herein 2,2′-(1,4-phenylene)-bis [4-mercaptan-1,3,2- dioxaborolane] (BDB) is employed as curing agent and a novel type of covalent adaptable network o-CFER is constructed by the reaction between thiols in BDB and epoxy groups in o-CFER. Obtained curing o-CFER vitrimers possess superior thermostability and good mechanical properties. Because of the transesterification of boronic ester bonds, o-CFER network topologies can be altered, contributing a self-healing ability and shape memory to the produced polymer. Besides, it is investigated the effects of the healing time and temperature on self-healing capability and achieved a healing efficiency of above 95% at 160 °C for 12 h. Moreover, through hot press, the pulverized samples of 8%C-o-CFER can be reshaped several times and mechanical properties of the recycled samples are well-restored even higher than those of pristine after being remolded at 200 °C for 60 min.

Preparation of water-based epoxy resin and its application as an automotive air filter paper binder

Water-based epoxy resin emulsion was prepared by emulsifying o-cresol formaldehyde epoxy resin with self-emulsified epoxy curing agent synthesized in this study and then used as an environmentally friendly binder for automotive air filter paper. The preparation process of the self-emulsified epoxy curing agent was confirmed by Fourier transform infrared spectroscopy (FTIR). The effects of neutralization degree (Neu) and amount of curing agent on the formation of epoxy resin emulsion were studied. The micro-morphology and size distribution of the epoxy resin latex were characterized by transmission electron microscopy (TEM) and dynamic and static light scattering, respectively. The micro-structure of the air filter paper surface was studied by scanning electron microscope (SEM). The mechanical strength and moisture-resistance properties of air filter strengthened by the prepared water-based epoxy resin emulsion was tested and compared to three commercial binders. The prepared epoxy resin emulsion greatly enhanced the mechanical properties and moisture-resistance properties of the air filter paper while maintaining its filtration properties. Therefore, the epoxy resin emulsion can be used as an environmentally friendly water-based binder for automotive air filter paper with excellent comprehensive properties.

Preparation, curing, and properties of boron-containing bisphenol-S formaldehyde resin/o-cresol formaldehyde epoxy resin/nano-SiO2 composites

Boron-containing bisphenol-S formaldehyde resin (BBPSFR) with different amounts of nano-SiO2 by in situ formation was used to cure o-cresol formaldehyde epoxy resin (o-CFER). The curing kinetics, dynamic mechanical properties, and thermal stability of BBPSFR/o-CFER/nano-SiO2 composites (BCS) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetry (TG), and thermogravimetrymass spectrometry (TGMS). Morphology of nano-SiO2-containing BBPSFR and glass fiber laminates of the BCS were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The mechanical properties and electrical properties were also determined. The results showed that nano-SiO2 accelerated the curing process and decreased the curing temperature; the non-isothermal curing kinetics of the BCS can be described by the two-parameter (m, n) Sestak-Berggren kinetic model, and the average value of m was 0.32 and n was 1.00. The thermal stability was enhanced by the addition of nano-SiO2, especially at higher temperatures, and the residual weight increased with increasing nano-SiO2 content. Incorporation of 6 wt% of nano-SiO2 increased the impact strength from 105 to 149 kJ/m2 and storage modulus at ambient from 6.85 to 12.7 GPa, and the TEM photograph of which showed that nano-SiO2 particles (about 50 nm) were dispersed in the matrix more uniformly. The volume resistance, R v, and dielectric constant, e, slightly increased when the nano-SiO2 content was 3 wt%.

Mechanical and thermal properties of cationic ring-opening o-cresol formaldehyde epoxy/polyurethane acrylate composites enhanced by reducing graphene oxide

Polyurethane acrylate (PUA) and o-cresol formaldehyde epoxy resin (o-CFER) is synthesized. The PUA/o-CFER glass fiber-reinforced composites cured by free radical/cationic ring-opening reaction are modified by the reducing graphene oxide (r-GO). Effect of r-GO on the thermal and mechanical properties of PUA/o-CFER glass fiber-reinforced composites are characterized by FTIR, DMA and TGA. The result of FTIR shows that the system has cured completely. DMA analysis indicates that this system has better compatibility, and the glass transition temperature (T g) decreases with increasing r-GO content. TGA analysis shows that the initial thermal degradation temperature (T id) and activation energy (E a) enhance 13.1 °C and 3.12 kJ/mol, respectively. The tensile and impact strength of glass fiber-reinforced composites are approximately 50 and 60 % higher than those without r-GO. It is shown that the r-GO can enhance the mechanical properties and thermal stability of composites.

Preparation of phosphorous- and nitrogen-containing epoxy emulsion and its flame retardancy

In this study, phosphorous-containing epoxy resin was first prepared by modifying o-cresol formaldehyde epoxy resin with 9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide. Self-emulsified nitrogen-containing epoxy curing agent was prepared by the reaction of bisphenol A epoxy resin E-44, triethylene tetramine and acrylonitrile. Phosphorous- and nitrogen-containing epoxy emulsion was obtained by emulsifying the phosphorous-containing epoxy resin with the self-emulsified epoxy curing agent. Effects of parameters to the formation of epoxy emulsion were studied. The microstructure and size distribution of the epoxy latex were characterized by transmitting electron microscopy and Malvern particle sizer, respectively. The flame retardancy of the phosphorous- and nitrogen-containing epoxy thermoset was tested by limiting oxygen index, UL-94 test method and thermal gravimetric analysis. Scanning electron microscopy was used to observe the micro-morphology of char residue of epoxy thermoset. The result shows that the prepared phosphorous- and nitrogen-containing epoxy emulsion presents excellent stability and the epoxy thermoset has excellent flame retardancy.

Effects of carbon nanotubes on curing and properties of boron-containing bisphenol-S formaldehyde resin/o-cresol epoxy resin composites

Boron-containing bisphenol-S formaldehyde resin (BBPSFR) with different amounts of carbon nanotubes (CNTs) was used to cure o-cresol formaldehyde epoxy resin (o-CFER). The curing kinetics, dynamic mechanical properties, and thermal stability of BBPSFR/o-CFER/CNTs (BCC) composites were investigated by DSC, DMA, and TGA. The morphology of BCC composites was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The mechanical properties and electric properties were also determined. The results showed that the glass transition temperature Tg, initial decomposition temperature Tid all increased with increasing CNTs content. The Tg and Td5 is about 20°C and 30°C higher than that of pure BBPSFR/o-CFER (BC), when content of CNTs is 1.5 wt%. The curing reaction active energy Ea can be calculated by Kissinger’s method. When the conversions α is between 0.15 and 0.95, Ea has a slight increase for the BBPSFR/o-CFER (BC) composite, but it exhibits slight decrease for the BCC composites. The non-isothermal curing kinetics of the BCC can be described by the two-parameter (m, n) Sestak-Berggren kinetic model. The BCC has the highest tensile and impact strength when contains of CNTs is 1.0 wt%, which is 34 MPa and 13 kJ/m2 higher than that of pure BC laminate, respectively. The electric properties of BCC laminates were improved by the addition of 1.0 wt% CNTs.

Preparation of phosphorus-containing epoxy emulsion and flame retardancy of its thermoset

In this study, the effects of the opening ratio and neutralization degree of diethanolamine to the formation of epoxy emulsion were examined. o-Cresol formaldehyde epoxy resin was modified with 9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide and diethanolamine and was then neutralized by acetic acid to obtain a phosphorus-containing epoxy emulsion by the phase inversion method. The microstructure and size distribution of the epoxy latex were characterized using transmission electron microscopy and the Malvern particle sizer, respectively. The glass transition temperatures of epoxy resins and their thermosets were characterized using differential scanning calorimetry. The flame retardancy of the phosphorus-containing epoxy thermosets was tested by the UL-94 test method, limiting oxygen index (LOI), and thermogravimetric analysis (TGA). The result shows that when the diethanolamine opening ratio was 22.5% and neutralization degree was 100.0%, a stable epoxy emulsion was obtained. When the phosphorus content of the epoxy resin was 2.5 wt%, the LOI value of the epoxy thermoset can reach 36.8 and pass the V-0 rating of the UL-94 test. TGA and scanning electron microscopy images of char residue of epoxy thermosets show that the flame-retardant mechanism of the phosphorus-containing epoxy thermoset was mainly attributed to a condensed-phase mechanism.

Synthesis and Properties of Flame-Retardant Waterborne Emulsion Derived from O-Cresol Formaldehyde Epoxy Resin

By modifying O-cresol Formaldehyde epoxy resin with DOPO and Diethanolamine, and then neutralized by acetic acid, phosphorous-containing epoxy emulsion with excellent flame retardancy can be obtained under strong agitation. Diethanolamine opening rate and neutralized degree to the formation of epoxy emulsion were optimized. The flame-retardant property of the cured phosphorous-containing epoxy resin was test by UL-94, LOI and TGA method. The result shows that when the opening rate of Diethanolamine is 25.0% and the neutralized degree is 95.0%, stable epoxy emulsion can be obtained. When phosphorus content of the epoxy resin was 3.0wt%, the LOI value of the resin can be reach to 39.2 and pass the UL-94 test，the 700°C char remaining is 30.0wt%. The result shows that the flame retardant mechanism of the phosphorous-containing epoxy resin is mainly through a condensed- phase mechanism.

Curing Behavior, Kinetics and Thermal Properties of o-Cresol Formaldehyde Epoxy Resin Modified by Liquid Crystalline Epoxy Resin

The curing kinetics of a bi-component system of o-cresol-formaldehyde epoxy resin (o-CFER) modified by liquid crystalline p-phenylene di[4-(2,3-epoxypropyl) benzoate] (p-PEPB), with 4,4-diamino-diphenyl ether (DDE) as a curing agent, was investigated by nonisothermal differential scanning calorimetry (DSC) method. The relationship between apparent activation energy, Ea, and the conversion α was obtained by the isoconversional method of Ozawa. A molecular reaction mechanism is proposed. The results show that the values of Ea in the initial stage are higher and tend to decrease slightly with the reaction progress. The primary amines have a higher Ea than secondary amines. The average curing Ea of o-CFER/p-PEPB/DDE system is 61.64 KJ/mol. These curing reactions can be described by a model proposed by Šesták and Berggren, which includes two parameters of m and n. Parameters such as reaction orders were evaluated using the Šesták-Berggren (S-B) equation and the following kinetic equation: dα/dt = Aexp(−Ea/RT)α m (1 − a) n . The curing behavior of the system was studied by polarized optical microscopy (POM) and torsional braid analysis (TBA). The compatibility of the p-PEPB and o-CFER system is very good. Temperature of mechanical loss peak is higher by 63°C than the common o-CFER epoxy resin, when the weight ratio of p-PEPB with o-CFER is 4:100.

Curing Kinetics of o-Cresol Formaldehyde Epoxy Resin and Succinic Anhydride System Catalyzed by Tertiary Amine

The kinetics of the cure reaction for system of o-cresol formaldehyde epoxy resin (o-CFER)/succinic anhydride (SA) and tertiary amine as a catalyst was investigated with a differential scanning calorimeter (DSC). Autocatalytic behavior was shown in the first stages of the cure for the system, which was well described by the model proposed by Kamal that includes two rate constants, k1 and k2, and two reaction orders, m and n. The overall reaction order, m + n, is in the range 2.1-2.6, and the activation energy for k1 and k2 was 109 and 72.0 kJ/mol, respectively. In the later stages, a cross-linked network was formed and the cure reaction is mainly controlled by diffusion. Diffusion factor, f(alpha), was introduced into Kamal's equation, then the calculated values agree very well with the experimental data. The molecular mechanism of this curing reaction was discussed.