Studies on synthesis of modified epoxidized novolac resin from renewable resource material for application in surface coating

Synthesis of Cardanol-Based Acetaldehyde Novolac Resin from Cashew Nut Shell Liquid (CNSL)

Polymers are currently in the limelight. Phenolic resin is one of the polymer products obtained from the polymerization process, either from natural or synthetic sources. One of the natural compounds that can be applied to polymers is cardanol. This study aimed to synthesize cardanol-based acetaldehyde novolac resin from Cashew Nut Shell Liquid (CNSL). Isolation of cardanol from CNSL was done by liquid-liquid extraction method with acetone and purified by gravity column chromatography in a mixture of n-hexane and ethyl acetate in a ratio of 9:1. HPLC analysis showed that cardanol compounds had aliphatic chains with different levels of saturation and the yield was 18.48%. The cardanol-acetaldehyde novolac resin was synthesized through a condensation polymerization reaction with a cardanol-acetaldehyde mole ratio (1:0.5), using HCl as a catalyst. FTIR and 1H-NMR analysis were employed to identify the novolac resin structure. The product was a brownish-orange solid with a yield of 12.80 mg (40%) and followed ortho-ortho substitution. Cardanol is one of the natural phenol sources that might be utilized to manufacture novolac resins.

Energy efficient room temperature synthesis of cardanol-based novolac resin using acoustic cavitation

The present study deals with synthesis of cardanol-cased novolac (CBN) resin by the condensation reaction between cardanol and formaldehyde using acoustic cavitation. It is a step-growth polymerization which occurs in the presence of an acid catalyst such as adipic acid, citric acid, oxalic acid, sulphuric acid and hydrochloric acid. CBN was also synthesised by a conventional method for the sake of comparison of techniques. The effect of molar ratio, effect of catalyst, effect of different catalyst and effect of power on the conversion to CBN has been studied. The synthesised CBN was characterized using the Fourier Transform Infra Red Spectroscopy (FTIR), Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance (NMR) Spectroscopy and Thermogravimetric Analysis (TGA). The reaction was monitored by the Acid value, free formaldehyde content and viscosity of the synthesised product. The reaction time required for the conventionally synthesised CBN was 5 h (300 min) with 120 °C as an operating temperature while sonochemically the time reduced to 30 min at room temperature. The amount of time and energy saved can be quantified. Ultrasound facilitated synthesis was found to be an energy efficient and time-saving method for the synthesis of novolac resin.

Microwave-assisted synthesis and characterization of resole-type phenolic resins

Resoles were prepared under microwave irradiation with different phenols, such as phenol, o-, p-, and m-cresols, separately with formaldehyde having formaldehyde/phenol ratio of 2:1 in basic medium. Analogical synthesis was performed using conventional heating for comparing the methods. The methylolation of phenol was confirmed by Fourier transform infrared spectroscopic analysis and a reaction mechanism was proposed. The number-average molecular weight was found by gel permeation chromatography technique. On the basis of the calculated value of kinetic chain length, the structure of the resole-type phenolic resin was proposed. Differential scanning calorimetry technique was used to investigate the curing behavior. As assessed by dynamic thermogravimetry, traces of resole sample prepared from p-cresol were found to possess better thermal stability, both in conventional as well as microwave-irradiated systems, among all other resole samples. The tensile strength, elongation at break, and impact strength showed an increasing trend. The main advantage of the process is about sixfold reduction of reaction time of the process carried at microwave reactors in comparison with the conventional heating.

Photoageing of cardanol: characterization, circumvention by side chain methoxylation and application for photocrosslinkable polymers

Photoageing of cardanol and its limitation by methoxylation of the side chain to produce photocrosslinkable copolymers of tunable reactivity.

Kinetics and Mechanism of Formaldehyde-Free Phenol-Glucose Novolac Resin Cured with an Epoxy

Formaldehyde used in manufacture and curing of phenol formaldehyde (PF) resins is a big challenge for the PF industry with respect to sustainability and human health. Glucose has grand potential to replace formaldehyde in synthesis of bio-based phenolic novolac resins curable with hexamethylenetetramine (HMTA, derived from formaldehyde), an obstacle to achieve formaldehyde-free curing. This study reports the curing of phenol-glucose novolac resin with a bis-phenol-A type epoxy without using HMTA. The curing process was investigated by using dynamic differential scanning calorimetry measurements at different heating rates. Apparent activation energy of the curing reaction is 109.6 kJ/mol. Sestak–Berggren equation model was determined to be the reaction model according to Málek methods. The model-predicted reaction rates showed a good agreement with the experimental results. The results showed that the curing process was complicated; the kinetics expression was shown to be first-order autocatalytic reaction.