Polymethylmethacrylate viscosity

The DEHZ basestock was selected as an efficient compromise for desired properties in a partial synthetic oil. An engine oil was formulated using 200 neutral oil, 100 neutral oil, polymethylmethacrylate viscosity index improver, an additive package, and 15% DEHZ. See Table VII under Current 5W-30. This 5W-30 formulation was then subjected to the various tests described in Table VI for qualification as an SF engine oil. The results are presented in Table VIII. 

Transport Properties Although the densities of SCFs can approach those of conventional liquids, transport properties are more favorable because viscosities remain lower and diffusion coefficients remain higher. Furthermore, CO2 diffuses through condensed-liquid phases (e.g., adsorbents and polymers) faster than do typical solvents which have larger molecular sizes. For example, at 35°C the estimated pyrene diffusion coefficient in polymethylmethacrylate increases by 4 orders of magnitude when the CO2 content is increased from 8 to 17 wt % with pressure [Cao, Johnston, and Webber, Macromolecules, 38(4), 1335-1340 (2005)]. 

All of these intermolecular forces influence several properties of polymers. Dispersion forces contribute to the factors that result in increased viscosity as molecular weight increases. Crystalline domains arise in polyethylene because of dispersion forces. As you will learn later in the text, there are other things that influence both viscosity and crystallization, but intermolecular forces play an important role. In polar polymers, such as polymethylmethacrylate, polyethylene terephthalate and nylon 6, the presence of the polar groups influences crystallization. The polar groups increase the intensity of the interactions, thereby increasing the rate at which crystalline domains form and their thermal stability. Polar interactions increase the viscosity of such polymers compared to polymers of similar length and molecular weight that exhibit low levels of interaction. 

Figure 19 The terminal relaxation domain of diluted polymethylmethacrylate (a) and diluted polyisoprene (b) can easily be distinguished from the matrix one (dashed lines) in a Cole-Cole representation of complex viscosities [19]-...

Figure 9.14 Transmission electron micrograph of a section of bicontinuous phase formed by 53 wt% polystyrene and 47 wt% polymethylmethacrylate blended with a Brabender mixer at a rate of 20 rpm, which is roughly equivalent to 90 sec, at 200°C. At this shear rate, the two components have about the same viscosity, around 1000 Pa s. The characteristic domain width is around 1 /xm. (From Miles and Zurek 1988, reprinted with permission from the Society of Plastics Engineers.)...

Polystyrene Although polystyrene is usually bonded by solvent cementing, it can be bonded with vinyl acetate/vinyl chloride solution adhesives, acrylics, polyurethanes, unsaturated polyesters, epoxies, urea-formaldehyde, rubber-base adhesives, polyamide (Versamid-base), polymethylmethacrylate, and cyanoacrylates. The adhesives should be medium-to-heavy viscosity and room-temperature and contact-pressure curing. An excellent source is a Monsanto Company technical information bulletin which recommends particular commercial adhesives for bonding polystyrene to a number of different surfaces. Adhesives are recommended in the fast-, medium-, and slow-setting ranges (10). 

C. Parkinson et al. (17) considered the effect of particle size distribution on viscosity. They studied suspensions of polymethylmethacrylate) spheres in Nujol with diameters of 0.1, 0.6, 1.0 and 4.0 microns with different volume fractions and with different particle size combinations to determine the influence of size-distribution on the viscosity. Each particle size gave a certain contribution to the final viscosity based on the volume fraction and the hydrodynamic coefficient obtained from the empirical equation for that particle size. The contributions were expressed in the same form as in Mooney s model, and the viscosity was calculated from the product of each term, n... 

Experimental data for polymer solutions have been reported by Osaki, Tamura, Kurata, and Kotaka (60), by Booij (12), and by Macdonald (50). Osaki et al. used polystyrene in toluene, polymethylmethacrylate in diethylphthalate, and poly-n-butylmethacrylate in diethylphthalate. Booij s data were for aluminum dilaurate in decalin and a rubbery ethylene-propylene copolymer in decalin. Macdonald s experiments were performed on several polystyrenes in several Aroclors and on polyisobutylene in Primol. Shortly after the original publication of the Japanese group, Macdonald and Bird (51) showed that a nonlinear viscoelastic constitutive equation was capable of describing quantitatively their data on both the non-Newtonian viscosity and the superposed-flow material functions. Other measurements and continuum model calculations have been described by Booij (12 a). 

One important exception to this rule is vinylketone polymers in which the Norrish type II reaction is responsible for the decrease of the molecular weight of irradiated polymers (see section 4). In contrast to polymethylmethacrylate, polymethylacrylate becomes insoluble on irradiation with 253.7 nm in vacuo [82]. In air, no visible insoluble material is formed and an apparent quantum yield of chain scission of 1.3 x 10-2 has been determined by viscosity measurements [82]. However, a qualitative comparison of sedimentation patterns of initial and irradiated samples indicates that crosslinking also occurs in the presence of air even if gelation is retarded by oxygen. This makes the above-mentioned value meaningless. Photolysis of thin polymethylacrylate films at 253.7 nm in vacuo has also been studied by measuring the insoluble fraction as a function of dose as described in section 2. Quantum yields of 1.9 x 10-3 have been estimated for both the chain scission and the crosslinking processes [83]. 

No single description or definition adequately covers all lubricants or lubrication processes. For example, we have seen that a fluid can function as a lubricant by virtue of its viscosity as a liquid. We have also seen that a monomolecular film of stearic acid deposited on a metal surface acts as a lubricant and dramatically reduces the coefficient of friction. A polymeric substance such as polymethylmethacrylate when dissolved in an oil will increase its viscosity and improve its loadcarrying performance in the hydrodynamic lubrication process. Stearic acid dissolved in a carrier oil can effect a strong reduction in the coefficient of friction for metal rubbed against metal. 

PVDF films have been coextruded " to fabricate multilayer films. The specifications of the main and satellite extruders are listed in Table 6.11 and illustrated in Fig. 6.27. In one construction, the top layer consisted of 60% by weight PVDF and 40% by weight of polymethylmethacrylate. The alloy had a melt viscosity of 18,200 poise at a temperature of... 

Polymer melts can be classified based on their viscosity low viscosity melts for polyacylamide polyethylene, polypropylene and polystyrene medium viscosity melts for ABS, cellulose acetate, POM and styrene butadiene and high viscosity melts for polycarbonate, polymethylmethacrylate, polypropylene oxide and polyvinyl chloride. 

Attempts were made to relate intrinsic viscosity [T)] to solubility parameters of mixed solvents. 82 of polymer was calculated from the equation [T)] = f(8i). The authors assumed that the maximum value of [11] is when 5j = 8j of polymer. However, studying [t)] for polymethylmethacrylate in fourteen liquids, the authors found a large scatter of experimental points through which they have drawn a curve with a diffusion maximum. Thus the precision of 8j values was affected by 10% scatter in experimental data. 

Different polymer blends like PE (polyethylene)/PS (polystyrene) [10-11] and PMMA (polymethylmethacrylate)/PS [12-13] have been produced using supercritical C02-assisted extrusion. Fully intermeshing twin-screw extruders have been used in these studies. A decreased shear thinning behavior on dissolution of supercritical CO2 into blends was observed. The obtained reduction in viscosity ratio resulted in a finer dispersion of the minor phase, which is desirable to create a good polymer blend. The effect of supercritical CO2 on the dispersion of the minor phase for a PMMA/PS blend can be seen clearly in Fig. 12.5. 

A material that solidifies from the molten state without crystallization, a supercooled liquid whose shear viscosity is t > 10 Pas, a liquid whose rigidity is great enough to be put to use, or a glassy state of matter. A typical glassy material is hard and brittle (tensile modulus E 70 GPa, tensile strength a 0.5 GPa). Typical polymeric glasses are atactic polystyrene, atactic polymethylmethacrylate, polycarbonate, etc. 

In Table 5.4.2, a number of liquid mixtures are listed to act as cosolvents of polymethylmethacrylate Intrinsic viscosity [r ] has been reported in... 

Reasonable confidence that these two curves are appropriate to describe the viscosity dependence is only possible because the number of independent measurements is very large. With fewer points Sasaki, et a/.(16) examined dilute polymethylmethacrylate in seven solvents, finding a x t]) qualitatively similar to... 

---