It may be possible to develop a thermoplastic elastomer by blending
ground scrap tire rubber with either virgin or recycled polypropylene
(PP), according to a new technical report released by the Chelsea
Center For recycling and Economic Development. The report is
based on research conducted by H.S. Liu, C.P. Richard, J.L.
Mead, and R.G. Stacer at the Univ. of Massachusetts Lowell Department
of Plastics Engineering.
These blends may have properties
similar to those of dynamically vulcanized blends, the research
theorized. Dynamically vulcanized blends are commercial products
prepared by crosslinking raw rubber, such as ethylene propylene
diene rubber (EPDM) or other rubber during melt mixing with
molten plastic, generally polypropylene. The resulting dynamically
vulcanized blend has small particles of crosslinked rubber imbedded
in a matrix of polypropylene.
The focus of the research was
to develop blends of ground scrap rubber with PP to develop
materials with a useful range of properties for new markets.
In addition to laboratory development of plastic/rubber blends,
an analysis of the market was performed to determine potential
applications for the new material. The cost effectiveness of
the blends in potential market applications was also assessed.
For the study, researchers tested
rubber derived by cryogenic grinding and ambient grinding methods.
Erickson Materials, Woburn, MA was the industry partner in the
research and provided ambiently ground Micropowder® for
the study. Erickson Materials closed their operations in late
1999. Similar material is available in Massachusetts from Rouse
Polymerics which purchased Erickson's technology and equipment.
In order to investigate the difference
between cryogenically ground rubber and Erickson's Micropowder®,
experiments were performed by preparing blends using 40% by
weight of each type (cryogenically prepared and ambiently prepared
Micropowder®) styrene-butadiene (SBR) (80 mesh) rubber and
60% polypropylene with a 12 Melt Flow Index. Some blends were
prepared by adding maleated PP to make the elements more compatible.
The rubber's surface was not treated prior to blending in this
test set.
The overall research concluded
that recycled ground rubber could be blended with PP to form
new material that can be used in applications such as sports
surfaces. By proper selection of the components and compatibilization
techniques, the blends can be tailored for specific applications.
The results of this work can be used to guide manufacturers
in the proper selection of materials and techniques to use recycled
rubber in blends for a variety of product applications.
The full report is available
from the Chelsea Center (617) 887-2300 phone; (617)887-0399
fax; or can be downloaded from the Center's website: www.chelseacenter.org
under "Publication."
