Plastisol measurements

Experimentally, Flynn (Ref 73a) has tested plastisol NC composite propints containing beryllium and triaminoguanidinium hydrazinium diazide in a closed bomb and measured the high specific impulses indicated in Table 23... 

An instrument for measuring the plasticity of an elastomer, e.g., Wallace Rapid Plastimeter Plastisol... 

Prior to the removal of the film from the gel block, samples of liquid were rapidly removed at various temperature levels and their viscosities measured on a Ferranti-Shirley cone plate viscometer at 20°C. The amount of material required fcr each measurement was very small and enough could be obtained by making one pass with a small spoon spatula across the width of the plastisol. At a temperature... 

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. 

Fig. 14. Dimensionless pressure as a function of dimensionless time at four points of the mould for plastisol I with gelatination taken into account upon moulding into a preheated mould. Solid lines calculated dotted measured...

In the experiments, the filling times for plastisols I and II were measured at various initial pressures and the values indicated by manometer 1-4 were read as a function of time. The data obtained were represented in the dimensionless form as recommended in Sect. 6.3 and compared with the predictions of theory. The typical data... 

Most of the plastisols are used in open molding. It is a very simple process to use. A measured amount of plastisol is poured into an open mold cavity. The mold and plastic are heated to gel and fuse the plastisol. The mold is then cooled so that it solidifies. It is stripped from the mold. Inserts can be placed in the liquid plastic before it is fused inserts can also be inserted in the mold before pouring. Two or more colors can be placed in different parts of the mold. 

This process resembles the open molding process except it is closed like a two-part compression mold (Chapter 14). A measured amount of plastisol is poured or pumped into the closed mold cavity, similar to close molding except that a slight pressure of about 5 psi (34.5 kPa) is applied. The mold is heated to fuse the plastisol then cooled. Later the mold is opened and the product stripped out. This process can provide for accurate thickness control, filling very complex shaped parts, and so on. 

The ease with which plasticiser is combined with PVC is a measure of processing characteristics critical in the dry blend mixing operation of S-PVC or the gelation stage of plastisols. Predictive equations have been developed (349). 

A study was carried out into the potential recovery of plasticiser and solvent from waste PVC plastisols using a ceramic multi-bore crossflow tube filter. The procedure employed to perform the test sequence involved clean water flux measurement, media acclimatisation, optimisation trial, concentration run, cleaning trial and final water flux measurement. Permeate samples were analysed using gas chromatography and compared with standards of diisononylphthalate(DINP)/white spirit mixtures. The ceramic membrane successfully recovered a clear mixture of DINP and white spirit. 

Triallyl cyanurate(TAC) was used as a reactive plasticiser to promote the high-temp, creep resistance of PVC plastisols. The resultant crosslinked structure was characterised using gel content and swell ratio measurements as well as FTIR spectroscopy. The crosslinking reaction was initiated using peroxide. The effect on the network structure of using a free radical scavenger in the formulation was also studied. The gel yield and crosslink density in the gel increased with increasing TAC concentration in the plastisol, while the... 

Plastisol Fusion—This property is a function of temperature, time, and solvating power of the plasticizer. This property may be measured by determining the clear point, that is, the temperature at which a clear solution is obtained when a low concentration of resin is suspended in a plasticizer and heated at a constant rate. 

ISO 3219. 1993 (75], covers polyester resins as liquids, emulsions, or dispersions using a rotational viscometer, coaxial cylinder viscometer, and cone and plate system. ISO 2555 (76] refers to the Bookfield viscometer. ASTM D1824 [77] covers the use of this instrument for the measurement of apparent viscosity of plastisols and organisols at low shear rates. For high shear rates. ASTM D1823 (78] describes a method using a Burrell Severs A-120 viscometer. ISO 1628 (79] covers determinations of viscosity number and limiting viscosity for PVC, polyolefins, polycarbonate, thermoplastic polyester, and methyl methacrylate polymers, in parts 2 to 6 respectively. 

The method and type of equipment used also vary with the type of adhesive. As an example, the viscosity of electrically conductive adhesives is measured according to ASTM D1824, Apparent Viscosity of Plastisols and Organosols at Low-Shear Rates by Brookfield Viscosity The viscosity of typical electrically conductive die-attach adhesives is measured with a Brookfield HBT viscometer with Spindle TB and Speed 5. For higher-viscosity conductive adhesives and for underfill adhesives, a Brookfield RVT or RVF viscometer is used with Spindles 6 or 7 at speeds of 4—10.4 rpm. Another Brookfield viscometer, the Cone-and-plate viscometer with a CP-51 spindle is used for low-to-intermediate viscosity adhesives. Finally, the Brookfield HAT and HBT instruments are used for the high-viscosity (1-2 million cP at 1 rpm) adhesives typically used in SMT applications. ... 

Extrusion viscometer operated under high shear rates is used to determine viscosity of organosols and plastisols. A sample conditioned to proper temperature is placed in an extrusion chamber, and the extrasion pressure and the rate of flow through the orifice are measured and used for result calculations. The orifice has the inside diameter of 3.17 nun... 

Viscosity can alternatively be measured by Brookfield viscometer according to ASTM D 1824 but results will differ because of the differences in shear rates and non-Newtonian properties of plastisols and organosols. 

Figure 9.2. Schematic behavior of elastic modulus and viscous modulus for plastisols with different concentration of plasticizer Cj < Cj < Cj. [Reprinted from European Polymer Journal, Vol. 34, Marcilla A., Garcia J.C., Qualitative Model for Viscoelastic Measurements during Gelation and Fusion of PVC Plastisols, p. 1341-1348, 1998, with permission from Elsevier Science].

The method and type of equipment used also vary with the type of adhesive. As an example, the viscosity of electrically conductive adhesives is measured aeeording to ASTM D1824, Apparent Viscosity of Plastisols and Organosols at Low Shear Rates by Broolfield ViscosityThe viseosify oftypieal electrically conductive die-attach adhesives is measured... 

According to Eq. (2.8) or (2.10) the concentration dependence of has two parameters, [rj and 0m- Both are measures of a specific physical quantity (respectively, shape and packing) and may be independently determined, for example, [rj] from viscosity of diluted suspensions and 0m from dry packing of solid particles. For anisometric particles, the magnitude of these parameters may also be theoretically predicted see the rheological summary in a quite recent monograph [64]. Once [rj] and 0m are known, Eq. (2.8) will correctly describe the rjr versus 0 dependence for complex industrial systems, for example, PVC (poly(vinyl chloride)) emulsions and plastisols, mica-reinforced polyolefins, and sealant formulations [44,65]. However, in some suspensions and blends, r] and 0m may vary with composition [66]. 

Initial viscosity n. A term used in the vinyl plastisol industry to denote the viscosity measured immediately after the plastisol has been mixed. The viscosity normally rises at a declining rate after mixing. 

Rotational viscometer n. An instrument for measuring the viscosity of pourable liquids, slurries, plastisols, and solutions. Most are of the bob-and-cup type. In these, the bob is a polished, accurate cylinder that is immersed in the liquid contained in the cup. Either the bob or cup is rotated and the torque on one or the other is measured, as is the rotational velocity. From these and the dimensions, the viscosity can be inferred, either directly by calculation from principles or indirectly by calibration with standards of known viscosity. An instrument widely used in the plastics industry is the Brookfield viscometer. 

Brookfield viscometer The Brookfield viscometer is the most widely used instrument for measuring the viscosity of liquids, plastisols, and other materials that have a thixotropic nature. The instrument measures shearing stress on a spindle rotating at a definite, constant speed while immersed in the sample. The degree of spindle lag is indicated on a rotating dial. This reading, multiplied by a conversion factor based on spindle size and rotational speed, gives a value for viscosity in centipoise. 

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