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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Post time: 12-23-2016