Sulfur strength development

One of the most conspicuous advantages of sulfur concrete compared with cement concrete, besides its chemical resistance, is its strength development (Figure 1). Even with very strong and thus early-setting cements, cement concrete requires about 28 days for hydration in order... 

Figure I. Strength development of sulfur concrete and cement concrete as function of concrete age and moisture supply...

The investigation of sulfur-infiltrated concrete at this laboratory included three major areas of study strength development and retention, resistance to freezing and thawing, and stability in various aqueous media. It was hoped that some conclusions could be drawn regarding practical manufacturing limitations, long-term durability in physically or chemically hostile environments, and potential usefulness of such concrete. 

Some evidence for two types of reactivity at the elastomer end comes from rate measurements. The experimental method for following peel strength development as a rate process was described in a 1970 paper. In Figure 4 a sulfur-cured EPDM of the commercial Nordel... 

An acid dipping operation for metal parts involves the use of a 75% strength sulfuric acid solution. Develop recommendations for the Maximum Achievable Control Technology for controlling the air emissions from such an operation. Hint Take some time to look at the EPA Web sites dealing with MACT standards and pollution prevention. 

The prevulcanization of natural rubber in latex form has also been a subject of much investigation. The cross-linking mechanism is not yet fully understood, but the water apparently plays a major role in it. Irradiation results in the cross-linking of the rubber molecules and in coarsening of the latex particles. A process of cross-linking of natural rubber latex has been developed to the point that it can be used for an industrial-scale application. The irradiation is performed in aqueous media by electron beam without a prorad (sensitizer) at a dose of 200 kGy (20 Mrad) or in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur cured (vulcanized) film. As an alternative, the addition of a variety of chloroal-kanes makes it possible to achieve a maximum tensile strength with radiation doses of less than 5 Mrad (50 kGy). ... 

The main constraints on ARO at this time are highly concentrated, oxidative solutions like chromic acid, nitric acid and peroxy-sulfuric etchant. Their process rinses can be recovered and metals separated but, reconcentrating to near (40-70% of) bath strength, achievable with other solutions, shortens membrane life. WTI is working to develop membranes and operating procedures to improve system economies. Right now a life of 4-6 months is typical in most applications. 

---