Stability 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... 

Cure Characteristics. Methods of natural rubber production and raw material properties vary from factory to factory and area to area. Consequentiy, the cure characteristics of natural mbber can vary, even within a particular grade. Factors such as maturation, method and pH of coagulation, preservatives, dry mbber content and viscosity-stabilizing agents, eg, hydroxylamine-neutral sulfate, influence the cure characteristics of natural mbber. Therefore the consistency of cure for different grades of mbber is determined from compounds mixed to the ACSl formulation (27). The ACSl formulation is as follows natural mbber, 100 stearic acid, 0.5 zinc oxide, 6.0 sulfur, 3.5 and 2-mercaptobenzothiazole (MBT), 0.5. 

Neoprene AC (1947). This polychloroprene was developed to provide better viscosity stability and resistance to discolouration, but it cures much more slowly at room temperature. It is a fast crystallizing grade and contains about 90% trans-, 4 structure. 

For rosins and rosin esters, the produets having high aeid numbers are the most susceptible to oxidation and have inferior viscosity stability and colour stability in adhesive formulations. Thus, when stability properties are essential in adhesives, rosin esters rather than high aeid number rosins are used. However, the high acid number resins are polar and display better adhesion to polar elastomers and polymeric surfaces. 

Polychloroprene elastomer. Neoprene AC and AD are the most commonly used, mainly Neoprene AD because of its superior viscosity stability. For difficult-to-bond substrates, graft polymers Neoprene AD-G or AF) show better performance. For sprayable adhesives or high-viscosity mastics, the Neoprene AG offers excellent results. When specific properties (e.g. increase tack, improve wetting, increase peel strength) need to be met, blends of Neoprene AC or AD with Neoprene AG provide adequate performance. 

Elbel, J.L. Thomas, R.L. "The Use of Viscosity Stabilizers in High Temperature Fracturing," SPE Paper 9036, 1980 SPE Rocky Mountain Regional Meeting, Casper, May 14-16. 

Glass, J.E. Soules, D.A. Ahmed, H. "Viscosity Stability of Aqueous Polysaccharide Solutions", SPE paper 11691, 1983 California Regional Meeting, Ventura, March 23-25. 

As described in Section 7.1, applications for liquid crystals are very demanding with respect to temperature range, adequate response to an electric field, viscosity, stability, and so on. The desired properties do not occur in a unique liquid crystal and consequently all the industrial devices use mixtures. In the field of metallomesogens, these are usually limited to binary mixtures. 

Hydroxyethylstarch is widely used with synthetic latexes in the surface sizing of paper and as a coating binder. For these uses, the hydroxyethylstarch is acid-thinned, oxidized, or dextrinized. Hydroxypropylstarch is used in foods to provide viscosity stability and to ensure water-holding during low temperature storage. 

Starch acetates [9045-28-7] are made by reaction of starch with acetic anhydride. Starch acetates are used in foods to provide paste clarity and viscosity stability at low temperatures. A waxy maize starch acetate is most commonly used. Waxy maize starch acetates for food use are often cross-linked. Acetylated starches are also widely used in warp sizing of textiles. 

Figure J. Viscosity stability of polyvinyl chloride-o-pkthalate ester compositions...

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... 

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

Other Plasticizers. Acetyl tributyl citrate is an outstanding nontoxic plasticizer for polyvinyl chloride in food packaging Plastisol formulations containing this ester have exceptional viscosity stability. Acetyl triethyl citrate is a good plasticizer for the cellulosics and acetyl trioctyl citrate shows promise with vmylidene chloride polymers. Other compounds of diverse nature find application as plasticizers. These include tetra-w-butyl thiodisuceinate, camphor, o-nitrobiphenyl and partially hydrogenated isomeric terphenyls... 

Formulations are optimized with additives to control granule strength, dissolution, chemical stability, viscosity, stability on storage, or fungal growth. They can also contain toning dyes and auxiliaries to improve their efficiency in a given application. 

It is clear that in order to produce a low initial viscosity plastisol with good viscosity stability, the drying conditions need to be optimized for two factors ... 

Production of well fused agglomerates for good viscosity stability through the appropriate choice of temperature and atomization. 

While most studies of particle swelling have dealt with emulsion polymers containing high acid levels, we have restricted our attention to latexes containing relatively low incorporated acid (ca.2-3%) to avoid substantial solubilization of the particles. Questions under current consideration are related to the location of incorporated carboxyl groups within the latex particles, the morphology of expanded particles, and the detailed mechanism of expansion. Information of this type is valuable not only from a fundamental standpoint but is essential in the investigation of very practical problems such as the viscosity stability of latex formulations. 

Table 2.7. Performance of synthetic and mineral lubricant oils. Relative evaluation of viscosity, stability (thermal, oxidation, hydrolytic, volatility), lubricity (wear protection and fatigue) and environmental impact...

Acid-hydrolyzed (thinned) starches are produced through depolymerization by hydrochloric or other acids.18,19 Their low viscosity stability restricts their utilization in paper mills. They are used primarily for surface sizing at the size press or at the calender stack. 

Com, tapioca, potato and wheat starches are the most commonly used starches in the US and Europe. In the US, 95% of the starch is made from corn, an amount representing 3.4% of the total com crop, excluding that wet-milled to make sweeteners (see Chapter 22) and alcohol11124 (see Chapter 2). In Europe, about 60% of the starch produced is made from com and about 20% each from potato and wheat.12 In select regions, rice, sorghum, arrowroot, sago and other starches are also used. The relative utility of these starches in foods is a function of differences in viscosity, stability to... 

FIGURE 9.7 Melt viscosity stability of polyamide 6,6 containing Firebrake ZB vs. antimony oxide (PyroChek 68PBI is a brominated PS). 

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