| Author: IMS |
| Changes
In Mold Releases |
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| Mold release is not as simple as it used to be. The
days of an operator spraying a can of CFC-based mold release are gone. Formerly
simple mold release decisions now require more information than ever before. |
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| CFCs and now most HCFCs have been banned as Ozone
Depleting Substances (ODSs). Substitutes are either a non-ozone-depleting
(non-ODS) aerosol or a non-aerosol bulk product. Application can still be
manual, or can be by robot or other automated equipment. Each alternative has
its positives and negatives. |
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| Aerosol Cans and Tanks (Cylinders) |
| Non-ODS aerosols use materials that are either more
flammable, more toxic, more aggressive against plastics, more expensive or
slower to evaporate than the old formulas. Selecting a formula is a matter of
deciding which of those attributes can be tolerated and which cannot. |
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| For hand-held cans, most molders determine that fast
evaporation is critical and that attack on their parts is unacceptable. Most
settle on mildly flammable formulas containing a halogenated hydrocarbon and
dimethyl ether. They are fast evaporating, low in toxicity and unlikely to
affect plastics. Cheaper formulas are available, but at greater risk. |
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| For tanks (also called cylinders), the issue is more
complex. Finding the right aerosol became particularly difficult a couple years
ago when HCFC-141b was banned. |
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| The problem is that complete non-flammability is
legally required by the DOT for shipping, and is certainly advisable in the
plant. With a flammable gas, great potential exists for fire damage or injury
if a hose were to break or a solenoid were to stick. Beware of any mold release
tank that contains dimethyl ether – a flammable gas. |
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| Making the formula non-flammable requires either a
very expensive formula or a cheap, chlorinated solvent such as
trichloroethylene – which is slow to evaporate, and poses health risks to
workers and chemical attack risks to some plastics. Normal propyl bromide (nPB)
once carried great promise, but has proven to be expensive without avoiding the
downsides of trichloroethylene. |
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| IMS has settled on two tank (cylinder) formulas. The
inexpensive A4 series uses trichloroethylene, and many molders have
successfully switched to it. The recently introduced Speed Mist series is
trichloroethylene-free. It is expensive, but it nearly matches 141b formulas in
performance. Though the per-spray cost is much higher than for old formulas,
the molder’s cost per part is minimally affected, and the plastic parts are not
jeopardized. |
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| Non-Aerosol Bulk Products |
| Non-aerosol bulks are low in direct purchase cost,
but carry hidden costs in labor and compressed air. More importantly, they
cannot achieve the spray quality of the aerosols. Even assuming that the
release agent is thin enough to be sprayed and that it is well atomized into
tiny droplets, 100% of each droplet is deposited on the mold. That is a far cry
from aerosols, where the vast majority of the droplet evaporates – leaving the
thinnest of films on the mold. The evenness of the mold release film easily
affects product quality. |
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| Any solvent added to the bulk release agent to
achieve better spray capability is going to bear one or more of the negatives
of the aerosols – flammability, slower evaporation, toxicity, attack on
plastics or high price. Bulks also cause higher labor costs, because the
material has to be purchased in a large container and poured or pumped into a
small container. In manual applicators, there is a very real risk of repetitive
motion injuries. |
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| Whatever method or formula of mold release, there is
no such thing as a free lunch. The advantages and disadvantages must be weighed
before the decision is made. |
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| Products related to this article: |
Mold Release, Aerosol Cans |
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Mold Release, Aerosol Tanks |
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Mold Release, Bulk Containers |