Modifying Intercalation Of Sericite And Preparation Of Epoxy Resin/Sericite Nanocomposite

As an important layered silicate, sericite holds excellent physical and chemical properties. In order to highlight its layers'fuction and enhance its application value, sericite was composited with epoxy resin (EP), a widely used thermosetting resin, to prepare EP/sericite nanocomposite (EPSN), to improve mechanical properties of EP. On account of the stable structure of sericite, structure activation and reformation were made before modifying intercalation with organic compound, which was the basis of preparing EPSN.The technology and mechanisms of modifying intercalation of sericite and preparing EPSN were researched in this paper. Based on thermal activated sericite, acidification reduced the interlayer electron charge and sodium treatment increased the cation exchange capacity (CEC). Modifying intercalation with CTAB enlarged the interlayer spacing of sericite, and then EP monomers intercalated into sericite layers and polymerized, leading to the layers dispersed in EP phase uniformly, and EPSN was prepared.Thermal activated sericite was stirred with HNO3 of 5 mol/L at 95℃for 4 h, and Al³⁺ of 31.0 mg/g in sericite structure were dissolved. Sericite achieved a CEC of 56.37 mmol/100g, which was the basis of modifying intercalation, by stirred in NaCl saturated solution at 95℃for 3 h.Intercalated sericite was prepared by CTA⁺ intercalating into activated-reformed sericite. The optimal intercalated sericite, in which CTA⁺ enlarged the interlayer spacing from 1.0 nm to 5.2 nm, was prepared under these conditions: reaction time of 24 h, reaction temperature of 80℃, CTAB (mol)/sericite (CEC)=15, aqueous, pH=4. About 80% of CTA⁺ chains were thought to tilt with an angle about 60°against sericite layers in bimolecular way, about 20% and 2% were vertical and parallel to sericite layers in monomolecular way, respectively. CTA⁺ chains were considered to bend in interlayers by FTIR. TG and DSC proved that the quantity of CTA⁺ absorbed on the surfaces of sericite was equal to that of CTA⁺ intercalating into interlayers, approximately.Using DDM as curing agent, DMP-30 as accelerating agent, EPSN was prepared by EP monomers intercalating into modifying intercalated sericite layers and polymerizing at 80℃for 2 h and 150℃for 2 h. XRD and TEM showed that exfoliated nanocomposite was prepared when adding sericite less than 1 wt%. When adding 1 wt% sericite, EPSN achieved the best mechanical properties and the tensile strength, flexural strength, impact strength of nanocomposite were 110%, 41%, and 94% larger than pure EP, respectively.