Research High-temperature Performance Of Novel Hybrid Composites Bearing Phthalonitrile Resins

As a novel thermosetting resin,Phthalonitrile resin（Bpph）expressed excellent thermostability,mechanical properties,processing performance and processability,widely used in aerospace,electronics,automobile industry and other fields.In this article,phthalonitrile resin was synthesized and the organic-inorganic hybridism between phthalonitrile and inorganic particles was investigated,meanwhile a new type of heat resisting carbon fiber reinforced composites were prepared.This research showed that Bpph/CF composites exhibited comprehensive performance after hybridized by B₄C.The main contents of this work are as follows:Bpph was synthesized by 4-Nitrophthalonitrile（Nph）and Biphenol（Bp）at the ratio of 2:1.The structure and performance of the Bpph were characterized by Fourier transform infrared spectrometry（FT IR）,H NMR Spectroscopy,differential scanning calorimeter and rheological analysis.The Bpph resin was mixed with Al₂O₃ and B₄C,and the hybrid system was obtained with the 4’4-diaminodiphenyl sulfone（DDS,5wt%）.The curing kinetics of different systems was studied via the Kissinger equation,and B₄C reduced the activation energy.The rheological analysis showed that inorganic particles broaden the processing window of Bpph.The FT IR results indicated that the B-H bonds were formed between B₄C and Bpph after cured with the DDS,and the stability of the material was improved.The thermal properties of cured resin modified inorganic particles were characterized by TGA and DTG and DSC,and the Tg of all systems were higher than 400℃.After being cured,Bpph hybridized by B₄C exhibited excellent thermal stability.T_d5%of N₂ as high as 600℃,and C_y1000℃was 86%.The T_d5%of air atmosphere up to 581℃,C_y1000℃was 80.6%.Although the thermal stability properties of Bpph were promoted by blended with B₄C,it is not sufficient to meet the requirements of mechanical properties in practical application.So designing and fabricating B₄C hybrid Bpph matrix composites are practically significant.The Bpph solution was obtained by solvating neat Bpph in hot N,N-Dimethylacetamide solution（1:3）.After drying for hours,the prepreg was obtained.The control variables and orthogonal analysis method were used to explore the autoclave moulding process of neat Bpph matrix composites and the B₄C hybrid Bpph matrix composites.The flexural properties and the interlaminar shear performance both at normal temperature and high temperature were characterized by universal testing machines.The results indicated that all the composites were in good performance in high temperature resistance,especially B₄C hybrid Bpph matrix composites showed excellent flexural properties and interlaminar shear performance in high temperature.The flexural strength of B₄C hybrid Bpph/T700 composites was 1829 MPa at home temperature,while 400℃up to 1004 MPa.Meanwhile the flexural strength of the B₄C hybridized Bpph/T800 fabric reinforced composites was 219 MPa at 450℃.The dynamic mechanical analysis（DMA）found that the Tg of all the composites were greater than 480℃and all the B₄C hybrid Bpph matrix composites were thermostable through TGA.