Polymers measurement values

BOPP/SiOx/hybrld polymer (measured value) <0.05... 

From the ratio of activities and measured values of n, the average number of initiator fragments per polymer can be determined. Carry out a similar argument for the ratio of activities for polystyrene and evaluate the average number of initiator fragments per molecule for each polymer from the following datat ... 

A comparison of these predicted values of E with the measured values plotted in the bar-chart of Fig. 3.5 shows that, for metals and ceramics, the values of E we calculate are about right the bond-stretching idea explains the stiffness of these solids. We can be happy that we can explain the moduli of these classes of solid. But a paradox remains there exists a whole range of polymers and rubbers which have moduli which are lower - by up to a factor of 100- than the lowest we have calculated. Why is this What determines the moduli of these floppy polymers if it is not the springs between the atoms We shall explain this under our next heading. 

With the availability of the higher density polymers the value of the melt flow index as a measure of molecular weight diminishes. For example, it has been found that with two polymers of the same weight average molecular weight (4.2 X 10 ), the branched polymer (density = 0.92 g/cm ) had only 1/50 the viscosity of the more or less unbranched polymer (density = 0.96 g/cm ). This is due to long chain branches as explained above. 

The toughness of interfaces between immiscible amorphous polymers without any coupling agent has been the subject of a number of recent studies [15-18]. The width of a polymer/polymer interface is known to be controlled by the Flory-Huggins interaction parameter x between the two polymers. The value of x between a random copolymer and a homopolymer can be adjusted by changing the copolymer composition, so the main experimental protocol has been to measure the interface toughness between a copolymer and a homopolymer as a function of copolymer composition. In addition, the interface width has been measured by neutron reflection. Four different experimental systems have been used, all containing styrene. Schnell et al. studied PS joined to random copolymers of styrene with bromostyrene and styrene with paramethyl styrene [17,18]. Benkoski et al. joined polystyrene to a random copolymer of styrene with vinyl pyridine (PS/PS-r-PVP) [16], whilst Brown joined PMMA to a random copolymer of styrene with methacrylate (PMMA/PS-r-PMMA) [15]. The results of the latter study are shown in Fig. 9. 

We employed a comparative Z-scan procedure, wherein we perform a reduced-aperture Z-scan on CS2 immediately followed by reduced and open-aperture Z-scans on the polymer solution at a particular wavelength. The peak on-axis intensity, /0, is then calculated from the CS2 peak to valley transmission change using previously measured values for its non-linear axis of refraction. Based on the work of Sheik-Bahae et al the equation for /0is given by 37]... 

Unfortunately, a few papers are known where normal stresses during shear flow of filled polymers were measured directly. Here an additional problem is connected with the solution of the problem what is considered a one-valued measure of elasticity of a material and under what conditions to compare the measured values of normal stresses. Moreover, the data at hand often represent rather a contradictory picture. 

This equation appears to have a number of names, of which the Mark-Houwink equation is the most widely used. In order to use it, the constants K and a must be known. They are independent of the value of M in most cases but they vary with solvent, polymer, and temperature of the system. They are also influenced by the detailed distribution of molecular masses, so that in principle the polydispersity of the unknown polymer should be the same as that of the specimens employed in the calibration step that was used to obtain the Mark-Houwink constants originally. In practice this point is rarely observed polydispersities are rarely evaluated for polymers assigned values of relative molar mass on the basis of viscosity measurements. Representative values of K and a are given in Table 6.4, from which it will be seen that values of K vary widely, while a usually falls in the range 0.6-0.8 in good solvents at the 0 temperature, a = 0.5. 

The calculated [r[] value is compared with the measured value. Further b values are then tried until the difference between the measured and calculated intrinsic viscosities is minimised. It is also possible to determine both Ml and b if [n] and Mj are known for the whole polymer. 

Vc crystalline Va, amorphous). The densities of the pure crystalline (pc) and pure amorphous (pa) polymer must be known at the temperature and pressure used to measure p. The value of pc can be obtained from the unit cell dimensions when the crystal structure is known. The value of pa can be obtained directly for polymers that can be quenched without crystallization, polyfethylene terephtha-late) is one example. However, for most semi-crystalline polymers the value of pa is extrapolated from the variation of the specific volume of the melt with temperature [16,63]. 

Several block and graft copolymers have been shown to form stable aggregates under thermodynamically poor solvent conditions, as a result of differences in the solubility of different parts of a macromolecule. Whereas in a good solvent the experimentally measured value of A2 for a copolymer represents the balance of all the multiple interactions, under thermodynamically poor conditions A2 is mainly determined by the interaction of the groups situated on the polymer-solvent interface. Groups which form the hydrophobic core and are not in a contact with the solvent do not contribute significantly to the solution properties of the copolymer. 

The electron mobility of oxadiazoles have been measured in a polymer matrix, values of 10 7 up to 10 3 cm2/Vs have been obtained [262, 263], These values are exceeded by starburst phenylquinoxalines (30) that approach 10-4 cm2/Vs at 106 V/cm [264]. Other material classes that are very interesting candidates for electron-transport layers comprise naphtalene-, 60, and perylenetetracarboxylic diimides, 59 [265], as well as bathophenanthroline [266] with reported electron mobilities of 10 3 and 4.2 x 10 4cm2/Vs, respectively. 

These equilibrium constants vary with molarity of the HF solution. Measured values corrected for zero ionic strength at 25 °C are = 6.71 x 10 4 mol 1, K2=3.86 1 mol-1, and K3=2.71mor1 [BrlO, Iul, Wall], implying a dissociation of only a few percent. This unusual behavior is still controversial and has been attributed to the greater strength of the H-F bond compared to the other hydrogen halides [Pal], to the presence of the dimer (HF)2 [Wal], or to polymers that may... 

To be certain that ionic character of the HA surface is operative in its contact with the cell in aqueous media, streaming potential measurements were carried out at pH 6.0 and 7.4. The C, potential for the polymer-coated glass beads (48-60 mesh) was calculated from the measured values of the streaming potential. The results obtained are shown in Table 10. 

Even within the limitations of fixed conformation, early force fields were deficient. The predicted unit cell dimensions were too small by more than 20 percent This situation was remedied by adjusting nonbonded potentials describing the fluorine-fluorine and carbon-fluorine interactions until predicted unit cell dimensions adequately reproduced experimentally measured values. This fitting was actually carried out using structural information from several polymers and was not an ad hoc parameterization for PTFE. It should also be pointed out that reproducing PTFE cell dimensions was a process of achieving an approximately correct interchain spacing for an approximate helix since the actual crystalline structure was not known at that time. Subsequently, it has become... 

Dipole measurements of PEMA are performed in different solvents, and experimental measurements are theoretically analyzed on the basis of the RIS formalism. Energetic and geometric parameters proposed for PMMA are found to give a reasonable account of the experimentally measured values, in general. However, the change in average dipoles with temperature is found to exhibit a substantial dependence on the type of solvent, which indicates the importance of specific solvent-polymer interaction on the conformational characteristics of the chain. 

When a low viscous solvent must be used in combination with a rather low molecular weight of the polymer, measurements are restricted to low /3-values, due to the discussed onset of turbulent flow. As in such a case the extinction angle % does not deviate very much from 45 degrees within the regime of laminar flow, it must be measured with a high absolute accuracy to furnish a reliable value for cos 2% or cot 2% [cf. eq. (3.42) or (3.44a)]. Measurements on a polydisperse sample become more reliable under such conditions due to the fact that cot 2 is increased by the polydispersity factor [eqs. (3.75a) and (3.83a)]. Examples for such a behaviour will be discussed in Section 3.8.3. 

Table 4 shows the effect of monomer concentration, coinitiator concentration, and conversion on the composition of poly(4-methyl-1-pentene) using EtAlCl2 coinitiator at — 50° C. The 1,2-, 1,3-, and 1,4-repeat unit concentrations in the polymer have been determined from polymer spectra by use of a computer curve simulator-plotting program and are rounded to the nearest percent. No limits of error are indicated since none could be determined analytically. A reasonable error is thought to be +15% of the measured value. 

The typical effect of rate on the measured value of K,c and the associated type of crack growth can clearly be seen in Fig. 4 for an epoxy polymer based upon a DGEBA resin and cured with various amounts of TETA. The values of K ci and K ca are those for crack initiation and arrest (Fig. 2b) respectively and the difference between them characterises the amount of crack jumping which has taken place. When the difference... 

Fig. 17a and b. Variation of Klc/Klcs ratio with j/e44 a Unmodified, simple epoxy polymer b Rubber-modified epoxy polymer AO values of q deduced from Eq. (6) A.0 measured values ofp Full curve Theoretical relation from Eq. (12)... 

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