Preparation And Properties Of Hyperbranched Benzoxazine/Epoxy Resin

Epoxy resin has good chemical corrosion resistance,mechanical,and dielectric properties.It is widely used in electronic components,package coatings and aerospace applications,but it still has some shortcomings,such as a poor toughness,weak impact resistance and easy aging.To overcome these aforementioned issues,new hyperbranhced polymers were produced and then used as new modifiers to further improve the properties of the epoxy resins.In fact,hyperbranched polymers possess some interesting properties,such as they have a special dendritic molecular structure,large number of terminal groups along with the other characteristics,could be a good option for enhancing the overall performances of thermoset polymers at lower costs.In this paper,two kinds of triamine diphenol-type hyperbranched benzoxazines(TADP-HBs),which were namely HB-TH and HB-TBF,were synthesized using hydroquinone and bisphenol AF as phenol sources,and polyetheramine T403 as amine source,respectively.In the meantime,four trisphenols diamine type hyperbranched benzoxazines(TPDA-HBs),which were abreviated as HB-PED230,HB-PED400,HB-PMD230 and HB-PMD400,were experimentally produced from the 1,1,1-Tris-(4-hydroxytriphenyl)ethane,the 4,4',4"-trihydroxytriphenylmethane as phenol sources,and the polyetheramine D230 and D400 as amine sources,respectively.Hereafter,the HB-TH,HB-TBF,HB-PED230,HB-PED400,HB-PMD230 and HB-PMD400 were characterized by Fourier transform infrared spectroscopy(FT-IR)and nuclear magnetic resonance(1H NMR).The epoxy resin(E-51)system was toughened by blending with the as-prepared hyperbranched benzoxazines as modifiers.Hereafter,the hyperbranched benzoxazine/epoxy resin blends were prepared and then investigated using the FT-IR,differential scanning calorimetry(DSC),thermogravimetric analyzer(TGA),mechanical test,and scanning electron microscope(SEM).The curing process of hyperbranched benzoxazine followed the cationic ring-opening solidification mechanism.Since the hyperbranched polymer structure contains a large amount of hydroxyl groups,the initial curing temperature was between 146 and 199?,which was significantly lower than the initial curing temperature of the typical benzoxazine monomer.The curing temperature peak was estimated to be between 247 and 254?,which was equivalent to 1,3-benzoxazine,and the exothermic enthalpy was between 131.1 and 250.3 J/g.The decomposition temperatures(T5 and T10)at 5 and 10%weight losses were between 280 and 300 ?,and 300 and 330?,respectively,while the carbon residue(YC)was between 20%and 40%.In addition,the synthesized hyperbranched benzoxazines have good solubility in most organic solvents.The epoxy resin cured product was prepared by using E-51 as the matrix resin,4,4'-diaminodiphenyl sulfone(DDS)as the curing agent and the hyperbranched benzoxazines as modifiers.The results showed that with the increase of hyperbranched polymer content in epoxy resin systems,the glass transition temperature(Tg)of the blend system firstly increased and then decreased.The Ts and T10 of the system slightly decreased,while the Yc marginally increased.The mechanical properties had also been improved to some extent,among which the HB-TBF-12%/E-51/DDS system had the best thermal stability(Yc reached 14.6%).It was found that the bending stress of HB-TH-12%/E-51/DDS system was 48.1%higher than that of E-51/DDS system,and the elongation at break and Impact strength of HB-PMD400-12%/E-51/DDS system were 2.0 times and 4.5 times higher than those of the E-51/DDS system.The results of SEM test showed that with the addition of hyperbranched polymers,the fracture surface gradually appeared tearing and wrinkling,showing obvious ductile fracture characteristics.