Soft resins analysis

Hard and soft acid and base (HSAB) principle, 16 780 Hard blacks, 21 775 Hard-burned quicklime, 15 28 Hard coals, 6 703 classification, 6 712 Hard copper alloys, 7 723t relief annealed, 7 723t Hard copy systems, 9 513-514 Hard core repulsion, 23 93 Hard-elastic olefin fibers, 11 242 Hardenability, of steel, 23 283—284 Hardened MF resins, analysis of,... 

The total resins and the total soft resins are to be determined by methods recommended by the German Commission for Brewing Analysis [5]. Agreed procedures are necessary because differences based on solvent solubility are not absolutely clear cut and some constituents may distribute between the two fractions. The provision that the total resins should be soluble in cold methanol is included to distinguish between the resins and wax. Hop wax, a mixture of long chain alcohols, acids, esters, and hydrocarbons, together with p-sito-sterol [6], will slowly crystallize from a cold methanolic solution but the process is not quantitative [7]. 

A modified method for Wollmer analysis of hop extracts is given by the EBC [25]. This method gives values for total resins and soft resins (and hard resins by difference). The a-acid content can be determined by conductometric lead titration of the soft resin which, when deducted from the soft resin figure, gives a value for the -fraction. 

Fourier transform infrared spectroscopy was applied to the study of lac resin, a complex natural resin of insect origin, and some of its derivatives. The results obtained by this method are compared with those from earlier studies that used classical methods of chemical analysis. Experiments include the preparation of hard and soft resins, dewaxed lac, ammoniated lac, lac acetal, halogenated lac, hydrolysed lac, rebuilt lac (rebulac), and the preparation of lac metal salts. It is found that FTIR has several advantages over classical methods, but that FTIR data requires supplementing by other instrumental techniques such as FT-Raman spectroscopy and solid state nuclear magnetic resonance. 21 refs. 

Figure 7.1. HPLC analysis of carbohydrates (simple sugars) in soft drink using resin column and refractive index detection. HPLC conditions column BioRad Aminex HPX-87C (300 x 7.8mmi.d.) injection volume 10 pL mobile phase water, flow rate 0.6mL/min at 85°C detection refractive index. Chromatogram courtesy of PerkinElmer, Inc.

Thermal analyses of other dental polymers have also been reported. The compositions of waxes have been studied by differential thermal analysis (DTA) [64-66] and DMA [67], Conventional DSC and DMA recently showed the superiority of microwave-processed denture base resins to those processed by the slower traditional dental laboratory heating regimen [68], In contrast, comparisons of Tg and other relevant properties for a soft denture liner that was processed by the dental laboratory procedure and a more convenient chairside procedure indicated that both procedures yielded equivalent results [69],... 

It is well known that adhesives need to be low-modulus elastomers, so that the resin formulation has to be designed to give, after UV-curing, a soft material with a low glass transition temperature (Fg). Fig. 3 shows some typical elastic modulus E) and tan S profiles recorded by dynamic mechanical analysis for a UV-cured polyurethane-acrylate which is suitable for adhesives applications, based on its E and Tg values. It is quite soft, as shown by its Persoz hardness value of 50 s, on a scale that goes up to 400 s for glassy materials. 

Therefore, before a final wall structure can be selected, it is necessary to conduct a combined strain analysis in both the longitudinal and hoop directions. This analysis will consider thermal contraction strains, the internal pressure, and the pipe s ability to bridge soft spots in the trench s bedding. In order to do this we must know more about the inherent properties of the material we are dealing with— a laminate made up of successive layers of continuous filament-wound fiberglass strands embedded within a resin matrix. We must know the modulus of the material in the longitudinal direction and the hoop direction, plus the material s allowable strain. 

The objective of this work was the utilization of some recently developed techniques that may be of value in the characterization of the adhesive process between a titanium alloy and a variety of polylmide resin systems. The techniques utilized were electron spectroscopy for chemical analysis (ESCA), specular reflectance infrared spectroscopy, and scanning electron microscopy. Contact angles of various liquids on the titanium alloy were also measured. Specifically, the question arises to what extent are any of these techniques of value in the characterization of the interface and in the determination of interactions for the titanium 6-4/polyimide resin systems. Dwight and Riggs (5) successfully used ESCA, soft X-ray spectroscopy, contact angle hysteresis and electron microscopy to examine fluoropolymer surfaces. 

SMA resins swell and eliminate carbon dioxide when heated at 200 C. The resultant soft, brown-colored resins are soluble in acetone, as well as hydrocarbons, to which it imparts a brilliant white fluorescence under ultraviolet light. Pyrolyzed polymer also dissolves in aqueous potassium hydroxide to produce a fluorescent solution.Sequence analysis and microstructure of SMA-type resins can be studied by pyrolysis/gas chromatography (PGC). Styrene yields are generally extremely low by the PGC technique. In a truly alternating copolymer it might be expected to be zero. For a copolymer showing 51.5 wt. % styrene, the styrene yield was 3.6%. 

Evaluation of hops was and is still carried out on smell and appearance of selected small samples. To improve objective assessment, determination of soft and hard resins, by dissolving experiments, was at one time a generally applied method. Today the most important analytical determination for hop evaluation is the quantitative analysis for the alpha acids. This is discussed fully in chapters 15 to 17. 

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