M C. Paira et al. Carbon 38(2000)1323-1337 2805, a polycarbonate from Bayer. It is a standard grade (7) for injection moulding, with a weight average molecular weight (Mw) of 22 880 g mol and a polydispersivity Applying the equilibrium condition between the tensile index, measured as the ratio M /M,, equal to 1.86.The rce acting on a fibre of diameter d, and the shear forces glass transition temperature, Tg, was equal to 145+1C, as transferred through the interface, a simple expression, measured by differential scanning calorimetry(DSC),on a proposed by Fraser and Di Benedetto [13], can be obtained Perkin-Elmer DSc7 instrument. The coefficient of thermal for the average interfacial shear strength,t: was measured on a Perkin-Elmer dynamic- mechanical analyser, DMA7, working on thermo-mechani- o() (8) cal mode in expansion, in the temperature range of 90 to For a given fibre/matrix system, the smaller the fibre min,apc was determined to be 97x10C. The mechanical characterisation of Makrolon 2805. in tension. fragments obtained in the fragmentation test, the higher the was performed in an Instron 4505 testing machine. interfacial shear strength equipped with a clip strain gauge extensometer. The resul obtained for modulus, yield strength and strain were 2.17±0.06GPa,659±0.5 MPa and5.3±0.3%, respective 3.E 3.1. Materials 3. 2. Surface characterisation The carbon fibres studied in this work had different 3. 2.I. XPs characteristics and were subject to plasma treatment in Two distinct analyses were performed. a global de- section geometries, and the hoe ate ere pitch-based, two termination of the surface atomic composition,in terms of several conditions. Three of them w unsized a ith different cross- verall carbon, oxygen and nitrogen content, was done ras a commercial fibre, with an ESCALAB 200A-VG SCIENTIFIC spectrometer, treated and sized. For comparison, a PAN-based fibre sing a mg /al double X-ray source with a power of 300 unsized and untreated, was also studied. In terms of W. Then, a thorough spectral analysis was run for the mechanical classification, the pitch-based fibres can be pitch-based P120J and ribbon fibres, untreated and plasma considered as ultra-high modulus (UHM) and high treated for 75 W/3 min. This analysis was performed on a modulus(HM), and the PAN-based fibres as high tensile Leybold LHS 12 spectrometer. The spectral deconvolution strength(HT). The general description of the fibres used, was conducted using a DS 100 Leybold system as well as their code names, is presented in Table 1 The P120J fibres were plasma treated in a range of 3.2.2. Wettability measurements plasma power conditions(75 w,3 and 10 min, 100 W,3 The surface energy measurements were performed on min and 150 W,3 and 10 min). The ribbon and C320 fibres the carbon fibres using a CAHn Dynamic Contact Angle were treated at 75 W for 3 min. The plasma reactor was a Analyser, DCA- 322. The dispersive component of the Technics Plasma 200-G model, with a microwave power surface energy was measured using a-bromonaphthalene of 2.45 GHz. In all cases an oxygen pressure of as the non-polar liquid For the non-dispersive component, 00 Pa was used the octane/water system was adopted. The dispersi The polymer utilised in the present work was Makrolon component of the surface tension of both liquids, octane General description of the carbon fibres used pe Precursor material Cross-section geometry UHM Unsized. uncreate Proprietary treatment Ribbon, Clemson UHM Unsized untreated O, plasma/INCAR C320, Sigri Great Circular Unsized untreated Lakes O, plasma/INCARM.C. Paiva et al. / Carbon 38 (2000) 1323 –1337 1325 2805, a polycarbonate from Bayer. It is a standard grade 3 l ¯5 ]l . (7) for injection moulding, with a weight average molecular c 4 ¯ 21 weight (Mw) of 22 880 g mol and a polydispersivity Applying the equilibrium condition between the tensile index, measured as the ratio M¯ ¯ /M , equal to 1.86. The w n glass transition temperature, T , was equal to 145618C, as force acting on a fibre of diameter d, and the shear forces g measured by differential scanning calorimetry (DSC), on a transferred through the interface, a simple expression, proposed by Fraser and Di Benedetto [13], can be obtained Perkin-Elmer DSC7 instrument. The coefficient of thermal ¯ expansion, a , was measured on a Perkin-Elmer dynamic- for the average interfacial shear strength, t : PC mechanical analyser, DMA7, working on thermo-mechani￾d cal mode in expansion, in the temperature range of 90 to t ¯5 ]ss d l . (8) c 2.lc 1308C. For samples prepared with cooling rates of ¯68C/ 26 21 min, a was determined to be 97310 8C . The PC For a given fibre/matrix system, the smaller the fibre mechanical characterisation of Makrolon 2805, in tension, fragments obtained in the fragmentation test, the higher the was performed in an Instron 4505 testing machine, interfacial shear strength. equipped with a clip strain gauge extensometer. The results obtained for modulus, yield strength and strain were 2.1760.06 GPa, 65.960.5 MPa and 5.360.3%, respective- 3. Experimental ly. 3.1. Materials 3.2. Surface characterisation The carbon fibres studied in this work had different 3.2.1. XPS characteristics and were subject to plasma treatment in Two distinct analyses were performed. A global de￾several conditions. Three of them were pitch-based, two termination of the surface atomic composition, in terms of were obtained unsized and untreated, with different cross- overall carbon, oxygen and nitrogen content, was done section geometries, and the third was a commercial fibre, with an ESCALAB 200A-VG SCIENTIFIC spectrometer, treated and sized. For comparison, a PAN-based fibre, using a Mg/Al double X-ray source with a power of 300 unsized and untreated, was also studied. In terms of W. Then, a thorough spectral analysis was run for the mechanical classification, the pitch-based fibres can be pitch-based P120J and ribbon fibres, untreated and plasma considered as ultra-high modulus (UHM) and high treated for 75 W/3 min. This analysis was performed on a modulus (HM), and the PAN-based fibres as high tensile Leybold LHS 12 spectrometer. The spectral deconvolution strength (HT). The general description of the fibres used, was conducted using a DS100 Leybold system. as well as their code names, is presented in Table 1. The P120J fibres were plasma treated in a range of 3.2.2. Wettability measurements plasma power conditions (75 W, 3 and 10 min, 100 W, 3 The surface energy measurements were performed on min and 150 W, 3 and 10 min). The ribbon and C320 fibres the carbon fibres using a CAHN Dynamic Contact Angle were treated at 75 W for 3 min. The plasma reactor was a Analyser, DCA-322. The dispersive component of the Technics Plasma 200-G model, with a microwave power surface energy was measured using a-bromonaphthalene generator of 2.45 GHz. In all cases an oxygen pressure of as the non-polar liquid. For the non-dispersive component, 100 Pa was used. the octane/water system was adopted. The dispersive The polymer utilised in the present work was Makrolon component of the surface tension of both liquids, octane Table 1 General description of the carbon fibres used Designation and Type Precursor material Cross-section Treatment/origin producer geometry P120J, Amoco UHM Pitch Circular Unsized, untreated a O plasma/INCAR 2 P75S, Amoco HM Pitch Circular Proprietary treatment and sizing Ribbon, Clemson UHM Aromatic Ellipsoidal Unsized, untreated a University mesophase pitch O plasma/INCAR 2 C320, Sigri Great HT Polyacrylonitrile Circular Unsized, untreated a Lakes O plasma/INCAR 2 a Instituto Nacional del Carbon, Oviedo, Spain