Pre-Expansion and Aging
The raw material resin used to manufacture EPS is received in the form of small
beads ranging from 0.5 to 1.3mm in diameter. These small beads are formulated and manufactured
by the suppliers to contain a small percentage of the naturally occurring
gas pentane. This gas is impregnated throughout the body of each small bead. The pre-expansion
phase of manufacturing is simply the swelling of the small bead to almost 50 times its original size
through the heating and rapid release of the gas from the bead during its glass transition phase.
R-Control uses very sophisticated technology and equipment in its pre-expansion
processes. By utilizing a computer controlled weighing system, a measured amount of beads are
introduced into the expansion equipment. Steam is introduced into the vessel and an agitator mixes
the expanding beads as the heat in the steam causes the pentane to be released from the beads. A
level indicator tells the computer when the desired specified volume has been reached. After a
pressure equalization phase, the expanded beads are released into a bed dryer and all condensed
steam moisture is dried from the surface. The pre-expansion is complete and another cycle is
ready to run. This process takes approximately 200 seconds to finish.
After the expanded beads have been dried they are blown into large open storage bags for the aging process. The beads
have been under a dynamic physical transformation that has left them with an internal vacuum in the millions of cells created.
This vacuum must be equalized to atmospheric pressure otherwise this delicate balance may result in the collapse, or implosion,
of the bead. This process of aging the expanded beads allows the beads to fill back up with air and equalize. This aging can
take from 12 hours to 48 hours, depending on the desired expanded density of the bead. After the aging is finished, the beads are then ready for molding into blocks.
Molding of Blocks
The molding process involves taking the loose expanded beads and forming them into a solid block
mass. R-Control's blocks are formed using a state of the art, vacuum assisted, block
mold. By utilizing a system of load cells, the computer is capable of controlling the exact weight of
beads introduced into the mold cavity. Once the cavity is filled, the computer uses a vacuum
system to evacuate residual air from the cavity. The vacuum is relieved by live steam which flows
over the entire mass of beads in the cavity. This vacuum rinsing process softens the polymer
structure of the bead surface and is immediately followed by the pressurization of the mold cavity
with more live steam. The latent heat from the steam and subsequent pressure increase cause the
beads to further expand. Since this is a confined environment, the only way the beads can expand
is to fill up any voids between them causing the soft surfaces to fuse together into a polyhedral type
solid structure. The computer releases the pressure after it reaches its predetermined set point. The
loose beads are now fused into a solid block.
R-Control's high tech
molding equipment goes one step further
after the pressure is released by submitting
the newly formed block to a partial
vacuum which allows for a faster cooling
period. This added step pulls residual
moisture from the block resulting in a
drier, better fused block of EPS. The
block is ejected from the mold and
another cycle is ready to run
Curing
Heat curing is the next step of our process. This not only accelerates the curing process of the freshly molded blocks, but also
assures that the material is dimensionally stable and provides a completely dry material for best fabrication results. We have
developed unique heat rooms for this purpose which are designed for efficient inventory transitions. This is one of the reasons
we feel we are able to offer the highest level of service and shortest response times possible, even during the busiest times of
the construction season.
Fabricating
R-Control quality molded
blocks are used for many applications, most
of which require the blocks to be trimmed
and cut to a desired dimension. R-Control utilizes
a series of thermal hot wire cutting tools to
accomplish a smooth surface cut while still
maintaining strict quality control dimensional
tolerances. These tools heat the wires
electrically and their resistance
characteristics cause them to reach heat levels
from 400 F to 800 F. The wires are drawn
down through the block to achieve the
length and width cuts and then the blocks
are pushed through the hot wires via a
conveyer to achieve the desired thickness
Download a PDF file of our EPS brochure.
