Controllable Curing Reaction Cyanate Ester Resin System

Cyanate Ester (CE) resin as a typical performance of thermosetting resin matrix withspecial structure and function was developed in1980s. It owns attractive integratedperformances such as excellent dielectric constant (ε=2.6-3.2) and dielectric loss(tanδ=0.001-0.008), outstanding thermal stability, low moisture rate. Due to the brittlenessand high-temperature cure reaction, the application of CE is limited. Therefore, tougheningCE and improving the cure process of CE resin are necessary.The main tougheners for CE include: thermosetting resin, thermoplastic resin, rubberelastomer, inorganic nanoparticle, unsaturated double bond-containing compounds. Resultsshow that microcapsules can toughen reins matrix and control the chemical reaction fortheir special structures. In recent years, much attention has been piad to the application ofmicrocapsules to resins matrix. Considering the disadvantages of CE reisns, a novelmicrocapsule was synthesized to toughen CE and lower cure reaction temperature. Themain research contents include:Poly(urea-formaldehyde)(PUF) microcapsules (MCs) filled with dibutyltin dilaurate(DBTDL)(PUF/DBTDL MCs) were synthesized using urea (U) and formaldehyde (F) asthe wall shell materials by in situ polymerization. The U-F resins could easily polymerizein the presence of the core material DBTDL to produce PUF polymers, and then theydeposited on the surface of the DBTDL droplets, forming PUF/DBTDL MCs. Thedecomposition temperature (Tdi) at5%weight loss of PUF/DBTDL MCs was245°C.PUF/DBTDL MCs released the DBTDL under heating condition.Multiple dynamic differential scanning calorimetry (DSC) experiments of BisphenolA dicyanate (BADCy) resin systems with PUF/DBTDL MCs were performed at heatingrate β of5,10,15and20°C/min, respectively. The kinetic parameters of BADCy/MCsincluding activation energy Ea, pre-exponential factor A and reaction order n were analyzedusing the FlynnWall-Ozawa method, Kissinger method, Crane method, Ozawaiso-conversional method and Coats-Redfern method，respectively. The results indicated that the addition of the MCs decreased the reaction temperature and increased the reactionactivity of BADCy owing to the release of DBTDL from MCs under heating conditions.Compared with BADCy/un-microencapsulated DBTDL, the BADCy/microencapsulatedDBTDL had lower activation energy, pre-exponential factor and the reaction rate constantdue to the slow release of DBTDL from MCs. The reaction order n of BADCy/MCs wasclose to that of BADCy/DBTDL. The reaction model of BADCy/MCs was considered as atwo-dimensional nucleation (A2).PUF/DBTDL MCs were applied to BADCy resins to develop a novel low temperaturecure high performance BADCy/MCs systems. The effect of PUF/DBTDL MCs on thereactivity of BADCy was investigated. The mechanical property, the thermal property, thewater uptake and the dielectric property of cured BADCy/MCs resin systems werediscussed in detail. Results indicated that roughly varying the content of the encapsulatedDBTDL could easily and safely adjust the polymerization temperature. When the contentof PUF/DBTDL MCs was0.125wt%, the BADCy/MCs systems cured at low temperatureshowed excellent mechanical property, good thermal property, low water uptake and lowdielectric property.