Plasticization effects, determination

This behaviour was explained as owing to a process of supramolecular structure loosening as a result of a polymer plasticization effect determined by CO2, which allowed quicker removal of CO2 [17]. The obvious consequence was that the kinetics equations established for every particular case (PUs sheet thickness or CO2 concentration) depended on the initial CO2 concentration. 

The model of Condo permits the determination of the limiting pressure at which the glass state exists, on the basis of a reduced number of parameters (only the glass transition temperature of the pure polymer is needed to calibrate the energy parameter) for this reason, it seems particularly useful for the prediction of the plasticizing effects. 

DMTA is a very interesting tool for characterizing heterogeneous materials in which domains of distinct Tg values coexist. The most interesting cases involve modified thermosets of different types (see Chapter 8). Examples are the use of rubbers (e.g., liquid polybutadiene and random copolymers), or thermoplastics (e.g., polyethersulphone or polyetherimide in epoxy matrices or poly(vinyl acetate) in unsaturated polyesters), as impact modifier (epoxies), or low-profile additives (polyesters). The modifier-rich phase may be characterized by the presence of a new a peak (Fig. 11.10). But on occasions there may be superposition of peaks and the presence of the modifier cannot be easily detected by these techniques. If part of the added polymer is soluble in the thermoset matrix, its eventual plasticizing effect can be determined from the corresponding matrix Tg depletion, and the... 

On the basis of observations made on limited structural series, certain authors (e.g., Adamson, 1980) suggested that water absorption would occur by occupancy of the available free volume by water molecules. Despite its seductive intuitive character, this theory fails to explain why free-volume rich substances such as silicone rubbers, crosslinked polyethylene, or simply liquid aliphatic hydrocarbons are hydrophobic. Furthermore, experimentally determined apparent heat of dissolution values (Hs) and plasticization effects generally agree well with theoretical predic-... 

Test methods for determining chemical resistance of plastics Effects of liquids on rubbers, test method Test method for chemical resistance of protective linings Test method for determining chemical resistance of fiberglass-reinforced thermosetting resin... 

The above examples demonstrate that it is not possible to predict a precise stereochemistry for a copper(II) complex in view of the existence of distortion isomers of Type A and B and of cation or anion distortion isomers. Each will have a definite stereochemistry, but a range of possible distortions (within certain limits) can arise due to the Plasticity Effect of the copper(II) ion and its variable eccentricity. This means that crystallographic data will be essential in determining the precise stereochemistry of the copper(II) ion in these distorted geometries. It also opens up the possibility that through... 

Our study is outlined in five parts, (a) Two polystyrene plastics were reinforced at different fiber contents alternately with polyester, asbestos, and glass fibers, (b) The mechanical/physical properties of the resultant monofiber-reinforced plastics were determined and compared, (c) Combinations of fibers were then used to fabricate multifiber-rein-forced structures to exploit simultaneously the particular advantages of the different reinforcements, (d) The effect of each fabrication stage on the molecular weight and molecular weight distribution of the matrix plastics was established and (e) a linear mathematical model was formulated to predict the properties of multifiber structures and forecasted values compared with corresponding values experimentally obtained from (c) above. 

Fixed arm peel and T-peel test procedures are used to measure peel strength for flexible laminates. Analysis of the contributions from elastic and plastic deformations of the peel arms during these tests enables the energy contribution from plastic effects to be subtracted from the energy required to peel the laminate. In this way, the adhesive fracture toughness is determined. 

The zero-shear viscosity of a concentrated polymer solution can be treated by a modified version of the method used to calculate the zero-shear viscosity of a polymer melt. The modifications take the two effects of the solvent (plasticization and true dilution of the polymer) into account. Approximations are involved, however, in determining the appropriate mixing rules for the plasticization effect and the magnitude of the true dilution effect. The zero-shear viscosity of concentrated polymer solutions will be discussed briefly in Section 13.G. 

The data thus far have shown that S-PS can be plasticized effectively with respect to backbone and ionic domain plasticizers. By appropriate choice of the plasticizer type either the PS backbone or the ionic domains can be plasticized preferentially. By appropriate control of the metal sulfonate content and the polarity of the plasticizer used, flexible S-PS compositions possessing useful tensile properties are feasible. While this approach has substantial merit, it is apparent that simply increasing the level of a phthalate plasticizer to improve melt flow results in a substantial decrease in useful tensile properties. It would be desirable to use a given level of backbone plasticizer and adjust the melt flow of the entire composition by independently plasticizing the ionic domains. One approach to achieve this objective has been described in the plasticization of ionic groups in metal-sulfonated ethylene propylene terpolymers (9). In those systems, the incorporation of metal carboxylates as plasticizers can improve both flow behavior and tensile properties. It is of interest to determine if this class of plasticizers can be combined with the phthalate plasticizers used for the S-PS backbone to provide an improved balance of flow behavior and tensile properties for S-PS s. 

The additives employed in field of plastic moulding achieve effects which meet the complex demands of this moulding technology by the mode of their contact with the particle surface and their constitutionally determined effects. Plasticizing effects are achieved by the functional groups of polyether, polymeric alcohol and fatty acid preparations. 

Testing of plastics articles - Determination of the effect of internal pressure oti hoi- low... 

The activation energy of the p-relaxation in dry PMMA, the one due to the prominent water-plasticization effect, and finally that due to the rotation of the a-methyl group discussed above can be determined from the information in Fig. 5.10 and are... 

Differential scanning calorimetry directly measures the heat flow to a sample as a function of temperature. A sample of the material weighing 5 to 10 g is placed on a sample pan and heated in a time- and temperature-controlled manner. The temperature usually is increased linearly at a predetermined rate. DSC is used to determine specific heats (Fig. 10-11), glass transition temperatures (Fig. 10-12), melting points (Fig. 10-13) and melting profiles, percent crystallinity, degree of cure, purity, thermal properties of heat-seal packaging and hot-melt adhesives, effectiveness of plasticizers, effects of additives and fillers (Fig. 10-14), and thermal history. 

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