PSA Solutions

Our preferred method for the preparation of PSA is by deionization of a sodium silicate solution with an ion exchange resin at room temperature. In this way the PSA solution is substantially free of electrolytes and therefore more stable. 

After the first two Elan campaigns Rob Orlandi concluded that it would be necessary to improve the stability of the PSA made by ion exchange in order to obtain attrition resistant catalysts. Based on preliminary work done by John Orlan at the East Chicago Laboratory, we found that at pH 3 PSA solutions of 5 w/o Si02 could be stabilized by lowering the pH to pH 1.9-2.1. We can understand this behavior of PSA if we look at the stability curve of colloidal silica. See Figure 4.1. 

A 5 w/o Si02 PSA solution is prepared by diluting 1014 g of JM grade sodium silicate solution (300 g Si02) with 4985 g of distilled water in an 81 SS beaker. The solution is stirred for a few minutes then Altered through SLS 520 B folded filter paper to give a clear water-like filtrate. 

To a mixing bowl, four thousand four hundred and forty four gram of the 5 wt% Si02 PSA solution was added and with the mixer on low speed, 2000 g of V/P/ O comminuted catalyst precursor was added in small portions over a period of 30-45 min. The resulting slurry, containing 34.48% solids (90% V/P/O catalyst precursor and 10% SiOj), had a pH of 2.5 0.1. 

In a recent survey Cap Gemini (2005) surveyed a number of projects where PSA solutions had been used. On each solution the following four areas were... 

Their report showed that 42 per cent of PSA vendors had disappeared in the last 5 years but most of the solutions had been adopted by new vendors. Our critical observation on PSA solutions is that they are useful data management systems but the effectiveness in achieving operational excellence in projects depends on how their outputs are used for project performance improvement. The demise of 42 per cent vendors in 5 years indicates a moderate success rate of PSA solutions. 

In order to find optimal conditions for the soluble copper determination we examined the influence of electrolysis potential, electrolysis time, and the solution stirring rate on the accuracy and sensitivity of determination. We found that the optimal parameters for PSA determination of copper were electrolysis potential of -0.9 V vs. 3.5 mol/dm Ag/AgCl, electrolysis time of 300 s, and solution stirring rate of 4000 rpm. The soluble copper content in samples investigated in this study varied from 1.85 to 4.85 ppm. Very good correlation between the copper content determined by PSA and AAS indicated that PSA could be successfully applied for the soluble copper content determination in various dental materials. 

NR pressure-sensitive adhesives with a high tackifier content can be used as commercial tapes and surgical plasters. These PSA require the elimination of the gel fraction and a reduction in molecular weight to facilitate solution. 

Hot melt aerylie polymers for UV cure are generally of lower moleeular weight than their solution counterparts in order to maintain an aceeptable application viscosity. Consequently more crosslinks are needed to produce a complete network and thus peel and tack suffer to some degree. Nonetheless, several UV curable materials have been commercialized for PSA tapes and labels. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

Performs a batch solution of PSA functional equations, sequence equations and point estimates using the Big Red Button providing QA by recording analysis steps,... 

The purpose of regulation is to protect the public from the risk of nuclear power. PSA make it possible to express the risk numerically. However, NRC regulations have been pro.scriptive to achieve an unknown risk level. Clearly too much regulation that destroys the industry is not desirable and too little may fail to protect the public. A possible solution is the use of PSA in regulations. Such has been resisted because of the uncertainties on the other hand there are uncertainties in proscriptive regulation but no attempt is made to express them quantitatively. The following condenses material from Murphy (1996) to reflect NRC thinking on this subject. 

Potentiometric stripping analysis (PSA), known also as stripping potenhometry, differs from ASV in the method used for stripping the amalgamated metals (22). hi this case, the potentiostatic control is disconnected following the preconcentration, and the concentrated metals are reoxidized by an oxidizing agent [such as O2 or Hg(II)] that is present in the solution ... 

The wheat extract is acidified with 0.50 mL of HOAc and loaded on to a Cig SPE cartridge (1 -g/6-mL). The cartridge is washed with 5 mL of 0.1 % HOAc. The cartridge is then eluted with 5 mL of ACN-0.1% HOAc (3 1, v/v) into a test-tube. The eluate is diluted to 10 mL with 0.1% HOAc. The resultant solution is loaded on to a PSA SPE cartridge. The PSA cartridge is washed with 5mL of 0.1% HOAc. The PSA cartridge is eluted with 5 mL of 0.5 M NH4OH into a test-tube. Just before analysis, the sample is acidified with 0.15 mL of HOAc. 

Fig. 5. WAXD spectra for (A) BB-loaded PSA, and (B) PNA-loaded PSA. (A) BB loading is (a) 0, (b) 15, (c) 30, and (d) 45. Note that as loading increases, the spectrum shows no change for the PSA crystallinity, but crystals of BB appear, indicating that the solute and polymer are immiscible. (B) PNA loading is (a) 0, (b) 5, (c) 10, and (d) 15. Note that there are no peaks corresponding to PNA as the loading increases, however, the polymer crystallinity decreases with increased loading, indicating polymer/solute compatibility. From Shen et al. (2001a). Reprinted with permission.

Potentiometric stripping analysis (PSA) is another attractive version of stripping analysis [7]. The preconcentration step in PSA is the same as for ASV that is, the metal is electrolytically deposited (via reduction) onto the mercury electrode (usually a film). The stripping, however, is done by chemical oxidation, for example, with oxygen or mercuric ions present in the solution ... 

Paraffin-embedded prostatic tissue sections (5 xm thick) are deparaffinized and rehydrated (Scorilas et al., 2000). A 5% universal tissue conditioner (Biomeda) is applied for 10 min at room temperature to block any nonspecific binding. The sections are incubated with biotinylated monoclonal mouse antihuman PSA antibody ( 2mg/l) (Diagnostic Systems Laboratories [coded 8301]) for 1 hr at 37°C. The sections are stained with (SA)Z-(biotin)x-PVA-(BCPDA)y-Eu3+ for 25 min at 37°C. After each step, the sections are rinsed briefly with 0.5 ml/1 Tween 20 solution. The slides are dried with a stream of cold air, and the resultant fluorescence is observed with a time-resolved fluorescence microscope. 

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