Grantee Research Project Results

Final Report: A Novel Method for Converting a Negative Value Waste into a Commodity Chemical

EPA Contract Number: 68D01056
Title: A Novel Method for Converting a Negative Value Waste into a Commodity Chemical
Investigators: Denvir, Adrian J.
Small Business: Lynntech Inc.
EPA Contact: Richards, April
Phase: II
Project Period: September 1, 2001 through September 1, 2003
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Waste , Small Business Innovation Research (SBIR)

Description:

There is a growing need to turn waste materials into valuable commodities. Scrap tires are an excellent example of a waste material with a guaranteed, renewable supply that has found several niche markets. One such market is the use of crumb rubber as an asphalt additive to increase its rheological characteristics, improving the ability of asphalt to withstand the high rates of stress and strain on roads and pavement. This market will benefit infinitely from increased surface activity of the crumb rubber produced from scrap tires. Finding an effective method to process and treat large volumes of crumb rubber will generate better products. Better products will have more market power, and eventually will help solve a difficult waste management situation.

Treatment of crumb rubber with an oxidant has been shown to improve the applicability and usefulness of crumb rubber in a number of applications. These applications, therefore, will benefit immeasurably from advancements in the treatment of crumb rubber to increase its surface oxidation. Increasing the surface oxidation of the crumb rubber modifies its rheological properties, makes the material mix better, and creates a better final product regardless of the application.

Summary/Accomplishments (Outputs/Outcomes):

Lynntech, Inc., has worked to develop an application that has been proven to increase the surface oxidation of crumb rubber, making it more amenable to recycling. Using proprietary ozone generation technology, an integrated unit was created to process crumb rubber in a field-portable unit to prepare it for mixing into asphalt. The design of this unit has been optimized to improve the throughput and efficacy of the treatment.

Extensive testing of the surface modified crumb rubber was performed by the Center for Asphalt and Materials Chemistry at Texas A&M University. Treated samples were blended into asphalt (to create crumb rubber-modified asphalt) and tested to determine the effect, if any, of the surface modification on the asphalt mixture produced. The effect of curing time and temperature on the sample's rheological properties was studied. As was the effect of ozone treatment on average particle size.

Conclusions:

After compiling and evaluating the data, a number of conclusions were drawn. The curing temperature and curing time of the crumb rubber-modified asphalt directly impact its rheological properties. Both factors also affect the particle size, which in turn affects the rheology of the ozonated crumb rubber-modified asphalt mixture. The treatment is most effective at the surface of the particles and is limited in its penetration. It was observed that there is an asymptotic decrease in particle size that correlates to an increase in homogeneity. Furthermore, there is an optimum curing time for crumb rubber at which the viscoelastic properties of the crumb rubber-modified asphalt do not increase but rather decrease. Increasing the curing temperature made the mixture behave in a more homogenous manner by making it more elastic in nature and less viscous. In conclusion, it was established that the treatment of crumb rubber with ozone prior to mixing with asphalt greatly enhances the quality of the asphalt mixture for application in surface treatment of roads and pavement.

Supplemental Keywords:

waste materials, scrap tires, crumb rubber, asphalt, paving, roads, pavement, oxidant, surface oxidation, rheological properties, recycling, ozone treatment, viscoelastic properties, surface treatment, small business, SBIR., RFA, Air, Scientific Discipline, Waste, Hazardous, Chemical Engineering, Municipal, Environmental Chemistry, Engineering, Chemistry, & Physics, Chemistry and Materials Science, Hazardous Waste, Environmental Engineering, recycled waste products, waste recovery, municipal waste, recycling, treatment, reuse, municipal solid waste landfills, tires, solid waste, crumb rubber