Polyisobutylene Density

What loading of wood flour (Table 11.2) in parts by weight is needed to make a polystyrene (density of 1.043 g/cm ) composite with the same density as water at 20°C (0.997 g/cm ) What loading of clay (Table 11.2) in polyisobutylene (density of 0.859 g/cm ) would give the same resulting density ... 

Barrier Properties. VinyUdene chloride polymers are more impermeable to a wider variety of gases and Hquids than other polymers. This is a consequence of the combination of high density and high crystallinity in the polymer. An increase in either tends to reduce permeabiUty. A more subtle factor may be the symmetry of the polymer stmcture. It has been shown that both polyisobutylene and PVDC have unusually low permeabiUties to water compared to their monosubstituted counterparts, polypropylene and PVC (88). The values Hsted in Table 8 include estimates for the completely amorphous polymers. The estimated value for highly crystalline PVDC was obtained by extrapolating data for copolymers. 

Polyisobutylene and similar copolymers appear to "pack" well (density of 0.917 g/cm ) (86) and have fractional free volumes of 0.026 (vs 0.071 for polydimethylsiloxane). The efficient packing in PIB is attributed to the unoccupied volume in the system being largely at the intermolecular interfaces, and thus a polymer chain surface phenomenon. The thicker cross section of PIB chains results in less surface area per carbon atom. 

Blends of isobutylene polymers with thermoplastic resins are used for toughening these compounds. High density polyethylene and isotactic polypropylene are often modified with 5 to 30 wt % polyisobutylene. At higher elastomer concentration the blends of butyl-type polymers with polyolefins become more mbbery in nature, and these compositions are used as thermoplastic elastomers (98). In some cases, a halobutyl phase is cross-linked as it is dispersed in the polyolefin to produce a highly elastic compound that is processible in thermoplastic mol ding equipment (99) (see Elastomers, synthetic-thermoplastic). ... 

In the absence of substantial unsaturation and of active groups on the chain for either polymer, only linear block copolymers are formed, according to the initiation Reactions 1 and 4. Low density polyethylene and high molecular weight polyisobutylene are typical of polymers which form block copolymer fractions on intensive mechanical working. The composition of block copolymers is related also to the relative rates of reaction, (Reactions 2 and 3) which is determined by the relative radical reactivity. 

The principal polyolefins are low-density polyethylene (ldpe), high-density polyethylene (hope), linear low-density polyethylene (lldpe), polypropylene (PP), polyisobutylene (PIB), poly-1-butene (PB), copolymers of ethylene and propylene (EP), and proprietary copolymers of ethylene and alpha olefins. Since all these polymers are aliphatic hydrocarbons, the amorphous polymers are soluble in aliphatic hydrocarbon solvents with similar solubility parameters. Like other alkanes, they are resistant to attack by most ionic and most polar chemicals their usual reactions are limited to combustion, chemical oxidation, chlorination, nitration, and free-radical reactions. 

In extension under conditions F — const, dependencies of total strain e and elastic strain a upon time t are measured as usual. In Refs. 11-13>15-35 38> these experiments were arranged with polyisobutylene samples with different molecular weights and with low-density polyethylene (see below). 

This section will deal with suppression of flow in extension of molten polymers in the region of significant elastic strains21 24 . The study of polyisobutylene 11-20 23,35) failed to reveal such phenomena (the velocity of irreversible strain ep = d(ln[3)/dt increased strictly with time). Retardation of polymer fluid flow is considered on the example of homogeneous extension at constant strain velocity and force. Most experiments were carried out with commercial low-density polyethylene (LDPE) with molecular weight MW 105. Figure 7 gives experimental dependencies of tensile force F/S0 and irreversible strain In 3 ( 3 = e/ot) upon time t at different... 

Let us consider now the effect of flow retardation in extension under constant force 25). The above-mentioned experiments wer,e carried out with low-density polyethylene at 125 °C and with polyisobutylene 11-20 at 44 °C. It should be noted right away that at the above-specified temperatures these melts have approximately similar characteristics under shear strain maximum viscosity is t) 3x 105 Pa s and relaxation time is 0 102 s. Flow curves in the investigated region of shear strain velocities also did not differ significantly from one another. 

Despite the proximity of flow curves, as well as values r) and 0 for these polymers (values r 0 and 0 are usually subject to dimensionless representation, normalization ofo0 and t), the time during which the maximum possible strain is attained In max = 2.8 for polyethylene and exceeds that of polyisobutylene at the same o0 by factor of 6. In this case the dependency In e(t) in the region of measurement for polyisobutylene is characterized by increasing strain velocity x = d(ln e)/dt in contrast to which x(t) decreases strictly in low-density polyethylene within a significant section of s and becomes approximately constant at high values of t. 

Division of the total tensile strain under conditions of F = const into several components 25,6R,69) produced interesting results (see Fig. 8). It has been found that the behavior of molten low-density polyethylene (Fig. 8a) is qualitatively different from polyisobutylene (Fig. 8 b) the extension of which was performed under temperature conditions where the high-elasticity modulus, relaxation time, and initial Newtonian viscosity practically coincided (in the linear range) in the compared polymers. Flow curves in the investigated range of strain velocities were also very close to one another (Fig. 21). It can be seen from the comparison of dependencies given in Fig. 8a,... 

The osmotic pressure of a solution of a synthetic polyisobutylene in benzene was determined at 25°C. A sample containing 0.20 g of solute per 100 mL of solution developed a rise of 2.4 mm at osmotic equilibrium. The density of the solution was 0.88 g/mL. What is the molar mass of the polyisobutylene The osmotic pressure is equal to that of a column of the solution 2.4 mm high. By the formula in Chapter 5,... 

Fig. 13.56 is chosen as an example showing the curves of polyisobutylene. These curves were corrected (reduced) for density and temperature. An arbitrary temperature T0 (K) (25 °C) was selected as the reference temperature. The reduced modulus values were calculated by... 

PB PBI PBMA PBO PBT(H) PBTP PC PCHMA PCTFE PDAP PDMS PE PEHD PELD PEMD PEC PEEK PEG PEI PEK PEN PEO PES PET PF PI PIB PMA PMMA PMI PMP POB POM PP PPE PPP PPPE PPQ PPS PPSU PS PSU PTFE PTMT PU PUR Poly(n.butylene) Poly(benzimidazole) Poly(n.butyl methacrylate) Poly(benzoxazole) Poly(benzthiazole) Poly(butylene glycol terephthalate) Polycarbonate Poly(cyclohexyl methacrylate) Poly(chloro-trifluoro ethylene) Poly(diallyl phthalate) Poly(dimethyl siloxane) Polyethylene High density polyethylene Low density polyethylene Medium density polyethylene Chlorinated polyethylene Poly-ether-ether ketone poly(ethylene glycol) Poly-ether-imide Poly-ether ketone Poly(ethylene-2,6-naphthalene dicarboxylate) Poly(ethylene oxide) Poly-ether sulfone Poly(ethylene terephthalate) Phenol formaldehyde resin Polyimide Polyisobutylene Poly(methyl acrylate) Poly(methyl methacrylate) Poly(methacryl imide) Poly(methylpentene) Poly(hydroxy-benzoate) Polyoxymethylene = polyacetal = polyformaldehyde Polypropylene Poly (2,6-dimethyl-l,4-phenylene ether) = Poly(phenylene oxide) Polyp araphenylene Poly(2,6-diphenyl-l,4-phenylene ether) Poly(phenyl quinoxaline) Polyphenylene sulfide, polysulfide Polyphenylene sulfone Polystyrene Polysulfone Poly(tetrafluoroethylene) Poly(tetramethylene terephthalate) Polyurethane Polyurethane rubber... 

Within the family of polyolefins there are many individual families that include low density polyethylenes, linear low density polyethylenes, very low polyethylenes, ultra low polyethylenes, high molecular weight polyethylenes, ultra high molecular weight polyethylenes, polyethylene terephthalates, ethylene-vinyl acetate polyethylenes, chlorinated polyethylenes, crosslinked polyethylenes, polypropylenes, polybutylenes, polyisobutylene, ionomers, polymethylpentene, thermoplastic polyolefin elastomers (polyolefin elastomers, TP), and many others. 

The calculated detonation parameters as well as the equations of state for the detonation products (EOS DP) of the explosive materials TKX-50 and MAD-X1 (and also for several of their derivatives) were obtained using the computer program EXPL05 V.6.01. These values were also calculated for standard explosive materials which are commonly used such as TNT, PETN, RDX, HMX, as well as for the more powerful explosive material CL-20 for comparison. The determination of the detonation parameters and EOS DP was conducted both for explosive materials having the maximum crystalline density, and for porous materials of up to 50 % in volume. The influence of the content of the plastic binder which was used (polyisobutylene up to 20 % in volume) on all of the investigated properties was also examined. 

Beret, S. Prausnitz, J. M., "Densities of Liquid Polymers at High Pressure. Pressure-Volume-Temperature Measurementsfor Polyethylene, Polyisobutylene, Poly(vinyl acetate), and Poly(dimethylsiloxane) to 1 kbar," Macromolecules, 8, 536 (1975). 

The van Krevelen method should be used in those cases where the deviation with GCVOL is over 6% (polyisobutylene, polyvinyl propionate) and for those polymers for which the GCVOL group parameters are not available. The density of polymers is important in many calculations. Several of the free-volume activity coefficient models discussed in Section 16.4 require the densities of polymers (and solvents) as input. We will see then that certain models are quite sensitive to the values of the densities employed. Moreover, polymer density data are often employed in equations of polymers for obtaining the pure polymer parameters. 

Polyisobutylene of molecular weight 1.46x10 was dissolved in toluene at 65°C and the solution was slowly cooled till it became turbid. Calculate an estimate of the volume fraction of polymer in the separated phase. [Polymer density = 0.92 g/cm molar volume of toluene = 106.9 cm /mol]... 

We have a dilemma we need a high-quality solvent to insure that the polymer remains in solution when it is formed but we need a solvent whose quality can be easily adjusted to induce the polymer to drop out of solution. How can we resolve it First, we need to know the thermodynamic variables that cause the occurrence of an LCST (chapter 3). The key variable in this instance is the chemical nature of the solvent or, to a first approximation, the critical properties of the solvent. Decreasing the solvent quality shifts the LCST curve to lower temperatures, and it is this variable that we wish to manipulate to force the polymer out of solution. To demonstrate the effect of solvent quality on the location of the LCST curve, consider the difference in LCST behavior for the same polymer, polyisobutylene, in two different solvents, n-pentane and cyclooctane. The LCST curve for the polyisobutylene-rt-pentane system begins at 70°C, while for the polyisobutylene-cyclooctane system it begins at 300°C (Bardin and Patterson, 1969). Cyclooctane, which has a critical temperature near 300°C, is a much better solvent than n-pentane, which has a critical temperature near 200°C, probably because cyclooctane has a greater cohesive energy density that translates into a lower thermal expansion coefficient, or equivalently, a lower free volume. Numerous examples of LCST behavior of polymer-solvent mixtures are available in the literature, demonstrating the effect of solvent quality on the location of the LCST (Freeman and Rowlinson, 1960 Baker et al., 1966 Zeman and Patterson, 1972 Zeman et al., 1972 Allen and Baker, 1965 Saeki et al., 1973, 1974 Cowie and McEwen, 1974). 

Polypropylene is somewhat similar to HDPE in general properties. It exists as a homopolymer and a copolymer with ethylene and other hydrocarbons. It can also be blended with polyisobutylene. PP is one of the lowest density plastics, translucent to natural milky white with a highly crystalline structure. PP homopolymer has poor low-temperature resistance but this has largely been overcome by copolymerisation with ethylene. 

Discovery of High-Pressure (Low-Density) Polyethylene Polyisobutylene... 

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