Polymer composite fracture surfaces studies

Scanning Electron Microscopy (SEM) with magnification capability of up to 20,000X was used for the study of the polymer composite fracture surfaces. The freshly fractured surfaces were coated with a 250 thick Au-Pd conducting layer. 

Denison P, Jones FR, Brown A, Humphrey P, Paul AJ, Scanning SIMS spectography of cfrp, Ishida H ed., Interfaces in Polymer, Geramic and Metal Matrix Gomposites, 239-248, 1988. Hearn MJ, Briggs D, ToF-SIMS studies of carbon fiber surfaces and carbon fiber composite fracture surfaces. Surface Interface Analysis, 17(7), 421 et seq, 1991. 

Several studies of polymer/silane coupling agent interphases have involved the use of scanning electron microscopy (SEM) [5-7]. For example, Vaughan and Peek [6] have used SEM to examine fracture surfaces to determine the mode of failure of composite materials and to draw conclusions about interfacial interactions of various coupling agents and epoxide and polymer resin systems. 

The effect of the curing agent concentration on the morphology of the polymer-polymer composites was studied by SEM. Micrographs of the fractured surfaces of samples a-1, a-2, a-3 and a-4 are shown in Figures 3, 4, 5 and 6 respectively. The average density and diameter of the rubber particles are given in Table II. The number of particles per unit area increased with... 

The polymers, whose characteristics are summarized in Table 1, were melt mixed in a Brabender-like apparatus at 200 C and at two residence times 6 min, at 2 r.p.m. and further 10 min. at 32 r.p.m. The blend compositions are listed in Table 2. After premixing, cylindrical specimens were obtained directly by extrusion using a melting-elastic miniextruder (CSI max mixing extruder mod. CS-194), Thermal and tensile mechanical tests were performed on these specimens by an Instron Machine (mod. 1122) at room temperature and at cross-head speed of 10 mm/min. Also made were morphological studies by optical microscopy of sections microtomed from tensile samples and scanning electron microscopy of fractured surfaces of samples broken at liquid nitrogen temperature. Further details on the experimental procedures and on the techniques used are reported elsewhere . 

Zhou and co-workers [27] studied the effect of surface treatment of calcium carbonate with sulfonated PEEK on the mechanical properties of the polymer. Tests used included tensile tests, flexural tests, notched Izod impact tests, TGA, DSC and SEM. The modulus and yield stress of the composites increased with CaCOs particle loading. This increase was attributed to the bonding between the particles and the PEEK matrix, was proved by the SEM of the tensile fracture surface of the composites. The treated fillers were found to give a better combination of properties, which indicated that the sulfonated PEEK played a constructive role in the calcium carbonate/PEEK composites. 

Using this technique, hard filler particles in a matrix become more clearly detectable without superposition by brittle fracture edges of the matrix polymer, as illustrated in Fig. 1.36. in this unconventional approach, the fracture surface must be obtained at a temperature at which the matrix is soft (the temperature must be sufficiently high above the glass transition temperature of the matrix) and the inclusions are hard (below the glass transition temperatures of the particles) at the same time. Besides the study of polymer composites, this procedure can also yield successful results for polymer blends, where the rubber particles were hardened by osmium tetroxide treatment. For instance, taking a fracture of an ABS polymer at 130°C, the temperature is well above the glass transition temperature of the SAN matrix, but the stained particles remain hard [12]. 

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