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Technology
Brief APPLIED
ENGINEERING TOOLS FOR |
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Technology
Brief APPLIED
ENGINEERING TOOLS FOR |
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This technology brief introduces an applied engineering tool for
designing and conducting trials to evaluate the conversion of secondary
crumb into conventional compression molded rubber products.
The use of recycled rubber is becoming more important because of
stockpiles of spent tires, mandates from large industrial customers,
governmental agencies, and consumer demand for recycled content products. In fact, six million scrap tires were ground
into crumb for beneficial reuse in 1995.
Fortunately, crumb technology has granted a cost-effective means of
utilizing spent tires and rubber scrap.
The tool provides essential background information on issues related to
compression molding with crumb rubber.
Additionally, a structured technique provides guidelines on how to
design and conduct trials to evaluate the usability of crumb in compression
molded rubber products.
Material and process parameters are both important considerations for
converting to crumb content formulations.
Material issues addressed in the tool include:
·
Formulating
rubber compounds containing crumb.
·
Compatibility
of different rubber compounds, such as Styrene-Butadiene Rubber (SBR), Natural
Rubber (NR), Isobutylene-Isoprene (Butyl), Polychloroprene (CR), Nitrile Rubber
(NBR), and Ethylene Propylene Diene Monomer (EPDM).
·
Crumb
specifications such as particle size distribution, loose contamination (e.g.,
metals, fiber, other), extract content, ash content, bulk density, carbon black
content, moisture content, additives and surface treatment.
·
Mixed
compound specifications such as viscosity and scorch.
·
End-product
material properties such as tensile strength, elongation, hardness, tensile
strength, modulus, tear strength and potential other properties.
Equipment and processing issues addressed in the tool include:
·
Processing
crumb from recycled rubber sources.
·
Mixing
the crumb-content stock.
·
Aging
and reworking mixed stock.
·
Molding
and curing
·
Expected
benefits affects of crumb on processing, such as reduced shrinkage, reduced
mold sticking and reduced curing time.
·
Process
and equipment requirements to compensate for increased compound viscosity, and
potential decreased flex and tear strength.
Logsheets are provided to facilitate evaluation of
the trial data and comments that were documented during the trials. Troubleshooting recommendations are provided
based on deficiencies in required properties of the end-product.
The tool suggests use of each trial result in
planning subsequent trials. The
findings of these documented and controlled trials should result in the optimum
crumb content and processing conditions to produce an acceptable compression
molded product.
To order a copy of the tool, or request more
information on converting to recycled crumb in compression molding, contact Joe
Divinigracia, ReTAP Research Engineer, at (206) 587-4221.
This technology brief was prepared by the Clean
Washington Center. The Clean Washington
Center is the Managing Partner of the Recycling Technology Assistance Partnership (ReTAP). ReTAP’s mission is to advance industry’s use
of recycled materials through technology extension services. ReTAP is an affiliate of the national Manufacturing
Extension Partnership (MEP), a program of the U.S. Commerce Department's National
Institute of Standards and Technology. ReTAP is also funded by the U.S. Environmental
Protection Agency and the American Plastics Council.
Report Dated: April 1997
Fact Sheet Issue Date: April 1997