Preparation And Properties Of Nitrogen-containing Phthalonitrile Resin

With the development of science and technology,higher requirements are put forward for the properties of materials.Phthalonitrile resin(PN)stands out among many high-performance resin materials due to its high decomposition temperature,good mechanical properties and excellent flame retardancy.It has broad application prospects in aerospace,shipbuilding,automobile manufacturing,microelectronics and other fields.Although phthalonitrile resin has excellent comprehensive properties,it also has obvious disadvantages,such as high melting point,poor processing performance and so on,which hinder its application and development.In order to solve these problems,flexible groups such as ether bond were introduced into the structure of benzonitrile in the previous research work.At the same time,in order to maintain the mechanical properties,some rigid structures are also introduced into the molecular chain.Most of these rigid structures are benzene ring structures,but there are few studies on nitrogen-containing aromatic heterocycles.In order to prepare phthalonitrile resin with good processability,heat resistance and mechanical properties,a new type of benzonitrile monomer,4,6-bis[3-(3,4-dichlorophenoxy)-phenoxy]pyrimidine(BCPM),was synthesized by introducing pyrimidine ring as a rigid part into the molecular structure of phthalonitrile while introducing flexible ether bond.4-aminophenoxy-o-phthalonitrile(APPH)was used as catalyst to cure the monomer to obtain the polymerization product.The melting point of BCPM is 159 ?,with a wide processing window(117 ?)and a low melting viscosity(<1.5 Pa·s).The Kissinger equation was used to determine the apparent activation energy required for monomer curing to be 80.96 k J/mol,which indicates that the processability is good.The resin has excellent mechanical properties and thermal stability.At 400 ?,the storage modulus is still as high as 1741 MPa,and no glass transition occurs.Substituting the residual carbon ratio at 850 ? into the formula calculates the limiting oxygen index as47,which indicates that it is a high temperature resistant flame retardant resin.Secondly,the pyridazine ring which also is nitrogen heterocyclic structure was inserted into the phthalonitrile molecular chain with 3,6-dichloropyridazine as the raw material by one pot two-step method.At high temperature,the polymerization products were obtained by Apph catalysis.The phthalonitrile monomer has not only a low melting point(74 ?),but also a wide processing window(178 ?).At the same time,it has excellent mechanical properties and thermal stability.At 30 ?,the storage modulus is as high as 3781 MPa,the glass transition temperature is higher than 400 ?,the initial decomposition temperature in inert gas is 500 ?,and the ultimate oxygen index is 48.The results show that the introduction of pyridazine ring can not only effectively reduce the melting point of phthalonitrile monomer,but also improve the processability,mechanical properties and heat resistance.