Synthesis And Application Of Cardanol Based Low Viscosity Resin

Cardanol is a low-cost,abundant natural phenolic compound extracted from cashew nut shell liquid,and contains a C15 unsaturated alkyl chain having unsaturation of 0 to 3.Cardanol is widely used in many aspects due to its multifunctional chemical structure,but there are few studies on its application in low viscosity,high heat resistance resins.In this paper,the cardanol-based epoxy resin and epoxy acrylate with low viscosity and excellent heat resistance were synthesized for the chemical structure of cardanol,and its application potential in photocuring was explored.The main findings are summarized as follows:(1)The cardanol-based epoxy resin(Cardanol Novolac Epoxy,referred to as ECN)was obtained by a condensation reaction between a cardanol and a formaldehyde solution under a certain ratio to obtain a polyhydroxy intermediate product(Cardanol Novolac,referred to as CN),followed by reaction with epichlorohydrin.In order to further reduce the viscosity of ECN,the synthesis process was optimized from the material ratio and experimental conditions,and the optimal synthesis process was determined.The obtained epoxy resin ECN had an epoxy value of 0.278 mol/100g-1,which was substantially close to the theoretical epoxy value,and the ECN viscosity was very low at 259 mPa-s.The synthesized ECN was characterized by 1HNMR,FT-IR and GPC.The results showed that the phenolic hydroxyl group was completely involved in the reaction,and the obtained epoxy resin was of high purity.The molecular weight distribution of ECN is concentrated,and the epoxy group is mainly 2 or 3.Adding ECN as a reactive diluent to the bisphenol A epoxy resin DGEBA can effectively reduce the viscosity of the epoxy system.When the ECN content is 20%,the viscosity of the system is reduced by about 80%.The introduction of a small amount of ECN can increase the crosslink density of the system,thereby enhancing the mechanical properties of the cured product,and has no adverse effect on other properties of the system.(2)The cardanol-based epoxy acrylate(Cardanol Novolac Epoxy Acrylate,referred to as EACN)was prepared by reacting ECN with acrylic acid and characterized by FT-IR and 1HNMR.By studying the properties of EACN,it was found that the prepared EACN has low viscosity,fast conversion rate,high conversion and 1.5%linear volume shrinkage during UV-curing.The cured product after illumination has excellent heat resistance,thermal decomposition initiation temperature above 300℃,and its surface has certain hydrophobicity,which the contact angle is 98.6°.(3)EACN was uniformly mixed as photocurable prepolymer with monomers with a total mass fraction of 20%to obtain five kinds of photosensitive resins,and their viscosity,photocuring properties,thermal properties and tensile properties were studied.The results showed that the five kinds of photosensitive resins have low viscosity,rapid conversion under illumination,and the linear volume shrinkage are all below 5%.The heat resistance of cured products are excellent,which the thermal decomposition initiation temperature can reach 350℃,and the mechanical properties and thermal properties of the photosensitive resin can be adjusted by changing the type of the monomer,thereby realizing the application of the photosensitive resin in various fields.In summary,the prepared natural product-based epoxy acrylate has fast photocuring rate,high conversion,low volume shrinkage and excellent heat resistance,which makes it possible to expand the biomass resource cardanol into the fields of high-value-added,high-performance materials such as UV-curing biomedical 3D printing and precision parts 3D printing.