Preparation And Properties Of Al₂O₃/OMMT/E51-BCE Composites

Bisphenol A cyanate ester(BCE)has the characteristics of low dielectric constant,low dielectric loss and good processability,and raw materials are relatively cheap.However,the molecular structure of BCE is in the high regularity status,which makes its toughness very low and limits the applications in the field of circuit board substrates.In order to improve the toughness of BCE without destroying other properties,this paper used bisphenol A epoxy resin(E51)to modify BCE in the way of copolymerization to prepare a modified matrix resin(E51-BCE)with high toughness.In the meantime,a nano Al2O3 was prepared by the Sol-Gel method,and sodium montmorillonite(MMT)was intercalated with octadecyl trimethyl ammonium chloride(OTAC)to prepare an organic montmorillonite(OMMT).Then,the Al2O3 and OMMT were used as blend reinforcements to prepare Al2O3/OMMT/E51-BCE composites,and the influences of the reinforcement mass fraction in the composites on their mechanical and dielectric properties of the composites were studied.Infrared spectroscopy(FT-IR),X-ray diffraction(XRD),thermogravimetric analysis(TGA),and transmission electron microscopy(TEM)were used to characterize the Al2O3 and OMMT prepared in this paper.The Al2O3 is confirmed to be the nano-scale needle-shaped y-type crystal,and the OTAC is successfully inserted into the MMT interlayers,and the OMMT is obtained.The crystal face distance of the OMMT is 2.14 nm,which is 0.7 nm higher than that of the MMT.The curing process of E51-BCE system was determined to be 180?/4 h+200?/2 h by the non-isothermal differential scanning calorimetry(DSC)method.At the same time,FT-IR was used to track the curing reaction of E51-BCE at the initial curing temperature of 160? and 180?.The results show that when curing begins at 160?,the reaction of E51-BCE system is more complicated,and multi-polymerizations are synchronously performed,while the curing reactions are in obvious sequence,when the initial curing temperature is 180?.The fracture surface morphology of the composites was observed by scanning electron microscope(SEM),and appropriate content of blend reinforcements show good dispersibility with the matrix resin.The test results of the mechanical and dielectric properties indicate that Al2O3 significantly improves the dielectric properties of composites,while OMMT has a greater impact to improve the toughness of composites.When the Al2O3 content is 3 wt%,the dielectric properties of Al2O3/E51-BCE composites are in the best performance,the dielectric constant and dielectric loss is 3.87 and 0.0029,respectively,at an electric field frequency of 100 Hz.OMMT/E51-BCE composites have the best mechanical properties when the content of OMMT is 2 wt%,the bending strength is 181.6 MPa and the impact strength is 32.6 kJ/m2.As for Al2O3/OMMT/E51-BCE composites,the comprehensive properties of the composites are the best,when the content of Al2O3 and OMMT are both 2 wt%.The bending strength and impact strength are 187.3 MPa and 35.1 kJ/m2,respectively,and the dielectric constant is further reduced to 3.39,at the electric field frequency of 100 Hz.