Determination of natural rubber in GR-S - natural rubber vulcanizates by infrared spectroscopy

melts, are susceptible to attack by metals such as lead and arsenic that can drastically reduce the life of the crucible. Either graphite crucibles (#A2260 Fusion Crucible, Ultra Carbon Corp., Bay City, Mich.) or vitreous carbon crucibles (#170 Crucible, Beckwith Carbon Corp., 16140 Raymer St., Van Nuys, Calif.) are well suited for this flux-fusion technique. Vitreous carbon crucibles are employed when reduction of sample components is a problem or when melts tend to wet graphite crucibles. Although vitreous carbon crucibles are rather expensive, 20 to 25 melts can be made in one crucible before it is destroyed by oxidation.Mixtures consisting of 90 wt % flux and 10 wt % sample give good characteristic X-ray yields for the lighter elements. The flux/sample ratio can be changed within reasonable limits to suit particular needs. All samples should be ground to pass at least -100 mesh.Preparation of Flux-Fusion Glasses. After mixing the flux and sample, the mixture is transferred to the proper crucible and fused according to the schedule depicted in Figure 1. An initial 5-minute fusion at 1100 °C will completely dissolve all but the most refractory samples, in which case the initial fusion time may be increased or the melt swirled in the crucible to promote solution of the sample. A mediumsized muffle furnace is satisfactory for either single or multiple fusions. After the initial fusion, a short carbon rod is placed on top of the melt to flatten the surface and an additional 5-minute heating period is begun (no carbon rod is used with vitreous carbon crucibles.) The crucible, melt, and flattening rod are then removed from the furnace intact and are cooled for 10 or 15 minutes to room temperature. The glass disks can be removed easily by lifting off the flattening rod and tapping the inverted crucible against a flat surface. Machining about a 2°t aper on graphite crucibles which

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“…Other infrared spectrophotometric studies have been made but no quantitative measurements were reported (3)(4)(5)(6).…”

Section: Resultsmentioning

confidence: 99%

Potentiometric titrations of sulfate using an ion-selective lead electrode

Ross¹,

Frant²

1969

Anal. Chem.

103

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“…SBR/NR. Further study (94) of pyrolysis followed by infrared measurement (148) showed that the absorbance ratio of bands at 889 and 909 cm.-1 was a function of the vulcanization recipe when pyrolysis was done at 550°C. However, when the temperature was increased to 950°C ., six different curing systems gave variations of only ±1.3% (94).…”

Section: Determination Of Polymers In Polymer Mixtures and Constituen...mentioning

confidence: 99%