Toughening Modification Of Polybenzoxazine And Its Low Dielectric COF Composites

As a novel thermosetting resin with excellent properties,polybenzoxazine could be potentially used in the fields of aerospace,microelectronics and locomotive.However,the inner brittleness of polybenzoxazine seriously restrict the commercial application,which could be easy to produce stress cracking leading to reduction of product performance.In addition,the dielectric constant of polybenzoxazine is relatively large,which could not meet the requirements of the highly integrated microelectronics in the 5G era.First,in order to investigate the scientific problem concerning on the mechanism how the interaction between nylon and benzoxazine and the melting point of nylon influence the toughening effect,three different nylons of PA12,PA11 and PA9T were incorporated into polybenzoxazine of PH-ddm,and the polybenzoxazine/nylon composites could thus be obtained after curing.The results indicate that the toughening effect of PA12 is the strongest,and PA11 is less efficient.The incorporation of PA9T could seriously deteriorate the toughness of polybenzoxazine.When the nylon content is 10 wt%,the tensile strength and fracture toughness of PPH-ddm,PPH-ddm/PA12,PPH-ddm/PA11 and PPH-ddm/PA9T are 49.5,53.0,51.2,29.3 MPa and 0.60,0.81,0.77 and 0.45 MPa·m^1/2,respectively.The fourier infrared spectrum（FTIR）showed that the hydrogen bonds could be formed between PA12 and PPH-ddm while no hydrogen bonds could be formed between nylons of PA11 and PA9T and PPH-ddm.The surface contact angles and surface energy analysis revealed that polar component of surface tension of PA12 and PPH-ddm was close to each other,indicating of the strongly interfacial interaction between PA12 and PPH-ddm.The scanning electron microscopy（SEM）observation indicates that the filaments could be observed between PA12 and PPH-ddm phases.It is revealed that the formation of hydrogen bonds and chemical bonds is beneficial to strengthen the interfacial adhesion and improve the resulting toughness of PPH-ddm resin matrix.In contrast,the existence of PA11particles could restrict the crack propagation while PA9T could not toughen the PPH-ddm resin,which should be attributing to the better compatibility between PA11 and PPH-ddm.Both of PA12 and PA11 could facilitate the curing of PH-ddm and slightly increase the glass transition temperature of PPH-ddm.Unfortunately,the PA9T will restrict the curing of PH-ddm monomer,leading to the obvious decrease of glass transition temperature of PPH-ddm,which should be related to the melting point of nylons.For example,the melting point of PA11 is relatively low,and the PA11 should be in the melting state even prior to the ring-opening reaction of PH-ddm.During the curing process,the existence of PA11 will not influce the ring-opening and crosslinking of PH-ddm.Attributing to the high melting point of PA9T,the particles are in the solid state during the whole curing process.The existence of PA9T particles will restrict the curing of PH-ddm.In general,in the nitrogen atmosphere,the incorporation of nylon particles will reduce the thermal stability of PPH-ddm.The PPH-ddm/PA12 specimens are more thermally stable than PPH-ddm/PA11 and PPH-ddm/PA9T,attributing to the stronger interfacial interaction between PA12 and PPH-ddm.The study could provide new ideas and theoretical guidelines to the toughening of polybenzoxazines by select the appropriate nylon particles.The three-dimensional covalent organic framework COF-300-V was blended with PH-ddm to fabricate the composites.By the use of porous structure of COF,the air could be introduced into the composites,thereby reducing the dielectric constant and dielectric loss.The results indicate that the incorporation of COF could effectively reduce the dielectric constant of PPH-ddm.At the COF content of 3 wt%,the dielectric constant and dielectric loss of PPH-ddm decreased from 3.61 and 0.031 to 2.62 and0.017.The SEM images reveal that the compability between COF and PPH-ddm is poor,and COF nanoparticles tend to aggregate in the resin matrix.Moreover,the introduction of COF could impede the curing of monomers,reducing the crosslinking density and the corresponding glass transition temperature of PPH-ddm.The COF particles could reduce the water surface contact angle of PPH-ddm from 95.2°to 76.2°,demonstrating of the obviously enhancement of hydrophility of PPH-ddm.In addition,the existence of COF could obviously enhance the thermal stability of PPH-ddm.The degradation temperature at 5%weight loss could increase to 19℃ at COF content of3 wt%.The introduction of amide bond into COF particles is believed to strengthen the interaction between COF and resin matrix,which could be potentially used in the field of microelectronics.