Plastisol viscosity

Plastisol Viscosity and Viscosity Stability. After the primary contribution of the resin type in terms of its particle size and particle size distribution, for a given PVC resin, plastisol viscosity has a secondary dependence on plasticizer viscosity. The lower molecular weight and more linear esters have the lowest viscosity and hence show the lowest plastisol viscosity, ie, plastisol viscosity for a common set of other formulation ingredients... 

Plastisols are often mixed and then stored rather than processed immediately (Fig. 5). It is of great importance in this case for the plasticizer to show htde or no paste thickening action at the storage temperature, and clearly it is not advisable to use a plasticizer of too great an activity, since grain sweUing, leading to plastisol viscosity increase, can occur at low temperatures for some active plasticizer systems. 

Plasticizers for acryhcs include all common phthalates and adipates. There has been interest in the development of acryUc plastisols similar to those encountered with PVC. Clearly the same aspects of both plastisol viscosity and viscosity stabiUty are important. Patents appear in the Hterature (32) indicating that the number of available plasticizers that show both good compatibiHty with acryHc resins and satisfactory long-term plastisol stabiHty may be fewer than those showing equivalent properties with emulsion PVC resins. 

Another very important property of plasticizers for PVC resins is the ability to act as a dispersing medium for polyvinyl chloride plastisols. The performance of the particular plasticizer in a plastisol application depends to a great extent on a property known as its viscosity stability. The stability of the plastisol to viscosity build up is the manifestation of the solvating effects of the plasticizer, and thus, those materials with higher solvating efficiency tend to display an increase in plastisol viscosity on standing. Figure 3 is the plot of the viscosity stability of PVC o-phthalate ester plastisol compositions and, in essence, compares the alcohol-derived plasticizers with that of the olefin-derived plasticizer. The data show that... 

Cowperthwaite, Coe, and Frissell (J) in their viscosity/temperature studies have defined the temperature at which the plastisol viscosity begins to increase as the gel temperature. These authors also studied the tensile strength of films cast on glass plates, fluxed at a series of temperatures between 300° and 425°F. They have defined the temperatures at which tensile strengths of 1000 and 1500 p.s.i. are attained as the fluxing temperatures. ... 

Time Dependence of Plastisol Viscosity in the Course of Gelatination... 

Attempts to give a quantitative analysis of plastisol extrusion were undertaken only in a few published papers. They were based on the analysis of plastisol viscosity as a function of temperature and time. If in the processing of thermosetting plastics their viscosity is assumed as practically independent of time (except of materials sensitive to structural and chemical transformation in temperature and stress fields which are accompanied by thermo-mechanical decomposition and cross-linking of macromolecular chains, the extent of the larter being influenced by the time of exposure to thermal and mechanical loads 18-21)), then at extrusion of plastisols, in view of their gelatination, the additional condition should be satisfield ... 

The rheological properties of plastisols generally could not be characterized on the basis of viscosity at some fixed shear rate (effective viscosity). Nevertheless, for practical purposes plastisols are conventionally classified into low-viscous (1-3 Pa s), medium-viscous (10-15 Pa s), and high-viscous (100-1000 Pa s) plastisols. Viscosities are measured at low shear rate y = 1 s l when plastisol flow is Newtonian. 

The effect of various plasticizers was studied for a number of plastisols prepared both from emulsion and suspension PVC 2>6,7,37 42 46 4% Judging from the published data 48), the most viscous plastisols are formed with mesamole, low-viscosity plastisols with dioctyladipate taken as a base, irrespectively of PVC type. Plastisol viscosity may be controlled by certain additives small smounts of certain solvents may lower plastisol viscosity by as much as an order of magnitude37,41>, the use of bentonites makes pastes more dense 40,48>. Thermoplastic polyethylene may also be used as a thickening agent6,42). 

In this case, the dependence of plastisol viscosity on mould temperature Tm is given by the expressions of the type of Eqs. (3.8-3.10) ... 

Determine the initial plastisol viscosity at optimal temperature Tffl and the given... 

Analysis of the viscosity aging data, Table III, reveals one significant trend. In general, as dryer temperatures are increased, plastisol viscosity aging decreases, Figure IX. The... 

Figure 5. Effect of atomizer speed at low dryer inlet and outlet temperatures on plastisol viscosity (dryer conditions—inlet/outlet 150°/60°C atomizer tip speed (-Q-) 79 m/s (---------------) 98 m/s (-----) 118 m/s (- -) 138 m/s)...

This data coupled with the viscosity and microscopic analysis illustrates a factor important to plastisol viscosity. For example, samples from dryer conditions 150/75 °C and 180/75 °C 138 M/sec tip speed have essentially identical particle size distributions, Figure XIV, but have different viscosities, Figure XV and Table II. 0max for the two samples indicate a difference... 

Figure 15. Illustration of different plastisol viscosities produced by resins having the same particle size distribution (see Figure 14) (dryer conditions—inlet/outlet (------------) 150°/75°C (------) 180°/75°C atomizer tip speed 138 m/s)...

Initial viscosities seem to be dependent on several resin variables within the plastisol. Resin particle size distribution is important to the viscosity in that decreased interparticle void volume by improved packing will decrease plastisol viscosities. The intraparticle void volume within agglo-... 

The drying conditions required for the optimization of plastisol viscosities will be dependent upon the latex PSD and percent solids. These factors need to be considered when performing drying studies and predictive work. 

Plastisol viscosity modifiers Fatty alcohol ethoxylates Sodium dialkyl sulphosuccinates Viscosity modification... 

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