Novel environmentally friendly tannin-cyclohexanone formaldehyde resin for high performance applications

Purpose: Cyclohexanone-formaldehyde resin (CFR) was in situ modified with tannin (T) in the presence of sodium hydroxide. The purpose of this study is to produce eco-friendly tannin-modified cyclohexanone resins (TCFR) with a one-step method that has higher decomposition temperature than CFR. The solubility, molecular weight and thermal properties of the product were investigated. Design/methodology/approach: Cyclohexanone, formalin (37 per cent aqueous solution) and tannin were mixed and 20 per cent aqueous NaOH solution was added to produce the resin. Tannin has environmentally friendly bio-based phenolic compounds that the tannin structure has been incorporated into the structure of the cyclohexanone formaldehyde resin during the in situ modification of resin, such as resole resin. Findings: The improvement of the properties of the TCFRs produced from condensed tannin. TCFRs were soluble in common organic solvents. The product TCFR has a dark red colour. Research limitations/implications: The reaction mixture must be stirred continuously. Subsequently, 37 per cent formalin was added drop-wise in total while refluxing. The amount of aqueous NaOH solution of it is limited, as the formed resin may become insoluble in common organic solvents. At the end of the reaction, a water-soluble resin is obtained. Then, the water of water phase was removed from TCFR reaction system, successively by evaporating with rotary evaporator. Practical implications: This study provides the application of ketonic resins. The TCFR containing tannin groups may also promote the adhesive strength of a coating. Social implications: These resins may be used for the preparation of adhesive. Condensed tannin, with a large amount of Catechol groups was considered for reducing the formaldehyde emission level on the adhesive system. Originality/value: TCFR has been synthesised in the presence of a base catalyst. Environmental and ecological concerns have increased the attention paid by chemical industry to renewable raw materials.