Zhiqiang Tao

Processing and Properties of Carbon Fiber-reinforced PMR Type Polyimide Composites

Carbon fiber-reinforced PMR-type polyimide composites were prepared from T-300 carbon fibers and polyimide matrix resin derived from 4,4′-methylenediamine (MDA), p-phenylenediamine (p-PDA), diethyl ester of 3,3′,4,4′-oxydiphthalic acid (ODPE) and monoethyl ester of cis-5-norbornene-endo- 2,3-dicarboxylic acid (NE). The rheological properties of the PMR polyimide matrix resin were investigated. Based on this information, an optimized molding cycle was designed for fabricating T-300/PI composites. The composites exhibited high thermal stability and good mechanical properties. The glass transition temperature (T g) determined by dynamic mechanical analysis and the decomposition temperature at 5% of weight loss (T 5) were higher than 360 and 540°C, respectively. The flexural strength and shear strength of the composites were 1560 and 95 MPa, respectively. The composite also exhibited good thermal-oxidative stability and hygrothermal resistance as evaluated under the conditions of isothermal aginginairat320°C and hygrothermal aging at 120°C under 2 atm. The unaged thermal and mechanical properties of the composites were hardly changed after isothermal aging for 500 h and hygrothermal aging for 100 h. The scanning electron microscopic analyses for both the isothermally and hygrothermally aged composites revealed that the matrix was bonded to the fibers very well, implying that no interface degradation occurred during the aging experiments

Short Carbon Fiber-Reinforced PMR Polyimide Composites with Improved Thermo-oxidative and Hygrothermal Stabilities

A series of short carbon fiber-reinforced polyimide composites (SCF/PI) with different SCF loadings was prepared by thermal curing of B-staged molding powders, which were obtained by impregnating short carbon fibers with PMR monomer solution in ethyl alcohol, followed by thermally baking up to 220°C. The B-staged molding powders possess good melt-flowing characteristics and processing properties. Experimental results demonstrated that the fully-cured SCF/PI composites exhibited high thermal stability with the glass transition temperatures determined by dynamic mechanical analysis (DMA) of 412-432°C and the decomposition temperatures at 5% of weight loss in the range 497-512°C. The SCF/PI composites also had good mechanical properties, which were affected by the SCF loading. The tensile strength and the flexural strength of SCF/PI composites increased as the SCF loadings increased and then decreased gradually. SCF-20/PI has the highest tensile strength of 101 MPa and SCF-10/PI gave the highest flexural strength of 154 MPa. The SCF/PI composites exhibited a great improvement in impact toughness in comparison with PMR-15. Despite the impact strength of SCF/PI being slightly decreased as the SCF loading was increased, it was still within the range of 15-23 J cm~2.Furthermore, SCF/PI composites exhibited excellent thermal-oxidative and hygrothermal stabilities. The SCF/PI composites showed a weight loss of less than 6% after isothermal aging for 500 h at 320°Cinair. There was no significant difference in thermogravimetric analysis (TGA) and DMA curves for SCF-20/PI after hygrothermal treatment at 120°C under 2 atm for 50 h

Aromatic Polyimide Resins for High Density Packaging Substrates

Molecular weight-controlled aromatic polyimide resins for fabrication of high density IC packaging substrates have been developed. The aromatic polyimide resins showed good laminate processability, which could easily dissolve in organic solvent to give low viscosity solution for impregnation of E-glass fiber cloths. After completely removal of the organic volatile, the polyimide/glass fiber (PI/GF) cloth prepreg could be plied up and then thermally cured at 280degC to give the PI/GF laminate suitable as packaging substrate core. Experimental results indicated that the polyimide laminates have the desirable characteristics for packaging substrate core, including 1) excellent thermal stability with initial thermal decomposition temperature of >500degC, CLE(in-plane) of 15-19 ppm/degC and glass transition temperature of >220degC; 2) good mechanical properties with flexural strength of >430 Ma and flexural modulus of 20 GPa, tensile strength of >230 MPa and impact toughness of 84 kJ/m2; 3) great electrical insulating and dielectric properties with volume resistivity of >1016 Omegaldrcm, dielectric constant of 4.1 and dissipation factor of 0.005 etc.; and 4) high peel strength of copper foil to laminate in Cu-claded laminate (>1.5N/mm).