XtraSoft™ is the result of using Intellimold to combine two
or more materials that are simultaneously injected into the mold cavity to
produce a core and skin affect. The core and the skin are bonded together
through boundary layers that contain both materials. Unlike co-injection, the
two materials do not form totally separate layers. There is a partial physical
infiltration of the skin into the core resulting in a stronger bond between the
layers. When the melt enters the cavity, it begins to cool from the outside
inwards, but the stiffer material freezes first. As it does so, it shrinks away
from the mold wall, leaving a gap around 70 microns across. The still-liquid
softer polymer is squeezed out of the mix, filling the gap just created.
Intellimold is able to injection mold "non-mixable"
materials compared to conventional molding. Non-mixable materials refers to
materials that are not more than partially soluble within each other,
substantially retain their identity when mixed, and do not chemically degrade or
decompose each other. By using the Intellimold process control, a substantial
Internal Melt Pressure builds within the molten material (i.e. the mixture of
non-mixable materials). The material with the highest modulus will begin to
solidify faster, with stronger shrinkage forces squeezing out and separating the
lower modulus material that is still liquid.
Only by having total control of the mold internal pressure
can this unmixing phenomenon be consistently reproduced. The counter-pressure
creates a situation in which the liquid is all at the same pressure, so the
stiffer material will stay in the center of the mold, wrapped up in a uniform
layer of the softer material.
XtraSoft
requires multiple polymers that are chemically compatible, are partially miscible, do
not degrade each other, have similar melting points, but have differences in
flex modulus of at least 150,000 psi. Material separation depends on the relationship
between flex modulus and temperature. When the melt hits the cavity wall and begins
to cool, the two materials quickly separate "like water separating from oil."
The one with the higher modulus forms the core because it freezes first it goes
through glass transition state and
begins to shrink, squeezing out the lower modulus material, which forms the
skin. While the process is ideally suited to combinations of polypropylene and a
thermoplastic elastomer like AES’s Santoprene™, it can be used with a wide
variety of materials and material combinations.
Xtrasoft can be used to make parts with cores made in
low-cost regrind and a higher-cost skin. The ratio of the two materials should
be unlimited. It is even possible to process more than two materials together.
Since XtraSoft provides true soft touch application, it replaces soft touch
paint, co-injection or two-shot molding in many applications.
The photo on the right highlights how the internal melt
pressure squeezes the lower modulus santoprene material to the surface. The larger
“building blocks” or heavier flex mod material forms the core.
XtraSoft
requires multiple polymers that are chemically compatible, are partially miscible, do
not degrade each other, have similar melting points, but have differences in
flex modulus of at least 150,000 psi. Material separation depends on the relationship
between flex modulus and temperature. When the melt hits the cavity wall and begins
to cool, the two materials quickly separate "like water separating from oil."
The one with the higher modulus forms the core because it freezes first it goes
through glass transition state and
begins to shrink, squeezing out the lower modulus material, which forms the
skin. While the process is ideally suited to combinations of polypropylene and a
thermoplastic elastomer like AES’s Santoprene™, it can be used with a wide
variety of materials and material combinations.