Coatings specimens Polymer

It is necessary to recognize here that in this stutty the comp< ite specimens were prepared from fibers which were coated by polymers formed under one set of electropolymerizations conditiors, and that these conditions were not optimized with respect to composite pro rties. The results are thus taken oidy to indicate the potential of electropolymerization for interphase modification in graphite fiber composites and the need to standardize electropolymerization conditions and monomer system to control polymer film properties and, through them, composite properties. 

In [332] it was noted that the strength of samples cut out at different locations of an article made from filled thermoplastics by pressure molding may differ widely — which is due to the non uniform orientation of the polymer at different locations of the mold. The very high strength parameters of composites with PMF in molded specimens are obviously also due to orientation effects, while for standard mixed samples of similar composition (that is, a matrix which, apart from the filler, contains some superhigh molecular polyethylene imitating the PMF coats) the... 

It has been found that, for a fixed mineral filler content, the viscosity of PMF-based composites increases when the coat is made of polyethylene [164, 209, 293], poly(vinyl chloride) [316] and polypropylene [326, 327], The picture was different, however, for composites based on the ethylene/vinyl acetate copolymer to which kaolin with grafted poly (vinyl acetate) was added [336]. Addition of PMF with a minimum quantity of grafted polymer results in a sharp drop of flowability (rise of viscosity), in comparison to addition of unmodified filler but with a further increase of the quantity of grafted polymer the flow gradually increases and, depending on the kaolin content and quantity of grafted polymer, may even become higher than in specimens with unmodified filler, for equal concentrations. 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

The plastics industry uses P.Y.173 to color various polymers. Incorporated in plasticized PVC, P.Y.173 is one of the tinctorially weaker pigments of its class. 1.8% pigment is required to produce 1/3 SD specimens containing 5% TiOz. The systems are almost completely fast to overcoating. P.Y.173 demonstrates excellent lightfastness and durability in rigid PVC and in PVC plastisols intended for coil coating. 

Polymer coatings on stiffer substrates can be measured by time-resolved techniques (Sinton et al. 1989). Often in these cases it is not convenient to measure a direct reflection from an uncoated part of the substrate at more or less the same time, and anyway the substrate may not be flat, but this may not matter if it can be assumed that either the thickness or the longitudinal velocity of the coating does not vary. The time interval between the echoes from the top and bottom surfaces of the coating can then be used to determine the unknown quantity. An example of the kind of signal that can be obtained is shown in Fig. 10.5. The specimen was a coating of PET (polyethylene terephthalate) 15 m thick on a stone-finish rolled steel substrate. Although there is some overlap of the two echoes, there is no difficulty in... 

The specimens were coated with a blend of the carboxylated polyester and second polymer in a solvent (10% solids), which, when possible, consisted of a conventional lacquer solvent (74.2% toluene, 7.4% butyl alcohol, 7.4% Solvesso 100 solvent, 3.7% ethyl acetate, 3.7% butyl acetate, and 3.6 Cellosolve acetate). If the second polymer was not soluble (polysulfone, polycarbonates, PPO), chloroform was used. The coatings were dried for 1 hour at room temperature and then for 2 hours in an oven at 115°C. The coating thickness was about 0.5 mil. 

Si(Li) detectors without Be windows ("windowless") or with thin metal-coated polymer films (Ultra-Thin Window UTW) have become an important peripheral to modern-day AEMs for the qualitative detection of elements with 5vacuum requirements because the removal of the Be window increases the probability of detector contamination (from the specimen or column environment) and consequent degradation of performance [12]. Windowless and UTW Si(Li) detectors are commonly installed with additional airlock mechanisms and only on instruments with acceptable levels of vacuum cleanliness. Thus, design constraints on modern AEMs preclude placement of the UTW detector close to the sample. In addition, loss of detection efficiency at low energies (light-element K-lines with the L-lines of transition metals all conspire to limit windowless or UTW EDS analysis of minerals to a qualitative basis only. 

The resonant beam test technique forms the basis of the ASTM Standard E756-83 for measuring the viscoelastic properties of damping materials. Fundamentally, the beam test requires that the resonant frequencies of a metal-beam, mounted in cantilever fashion, be determined as a function of temperature and frequency the beam is then coated with a polymer and the resonant frequencies and corresponding modal damping of the composite beam are determined as a function of temperature and frequency. From these two data sets, the vibration damping properties of the polymer can be evaluated. The ASTM Standard provides the necessary equations to obtain the complex modulus data from the collected test data and also provides guidelines for the proper choice of the specimens (1.21. The principal difference between the beam test and the other methods used here is that the beam test calculates the material properties from the test results on the metal beam and the composite beam whereas the... 

The uniformity of the plasma polymer coating with respect to chemical composition along 10-m coated silicone tubing was examined by XPS. Specimens of about 2 cm in length were cut from the top, middle, and bottom sections of the... 

The retardation of the migration of silicone oligomers from the silicone tubing after being coated indicates that the plasma polymer coating applied to the tube substrate is in a form of continuous film with barrier characteristics instead of some other physical forms (e.g., powder). Direct evidence of this aspect can also be seen from the fact that all test specimens prepared had passed the dye penetration test. 

The microstructure and micromechanics of isolated crazes have drawn the attention of many investigators (see, for example, the review of Kramer Berger (1990)), probably because of the similarity in shape between crazes and cracks. Kramer Berger (1990) have observed craze microstructure by transmission electron microscopy (TEM) and analysed the stress-strain relationship in and around a craze on the basis of TEM images. They adopted a skilful technique to strain a copper grid coated with a thin film of a polymer to form crazes in the specimen chamber of... 

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