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PMC724 Moldmaking Urethane

DESCRIPTION:  PMC724 is an exceptional jewelry molding rubber  for wax  injection.  It pours easily,  and cures (without heat) to a tough durable rubber that is easy to cut, and yet soft enough to allow removal of waxes without breakage.  Part A  is a brown liquid and Part B is a white syrup.  Part A & B must be proportioned, by weight, in a 10A to 100B ratio using a scale, and then thoroughly mixed.  After mixing, PMC724 will remain pourable for at least 20 minutes.  Molds can be used the next day. Physical properties (after 72 h cure at 72°F):

                Specific Volume, cubic in./lb.             20

                Hardness                                               40 A

                Ultimate Tensile Strength                   600 psi

                Elongation at break                              700 %

                Linear Shrinkage                                  Negligible

MODEL PREPARATION:   Normally, PMC724 can be poured against the glass/aluminum frame and the ring pattern without fear of adhesion. But where there is a question of compatibility or adhesion, a test cure should be made to insure complete curing and good release.  In some cases, #200 EaseRelease has been used to assist the release.    

MIXING AND CURING:  Part B should be stirred before use as it may settle from storage.  Both parts tend to absorb atmospheric moisture, and should be kept away from steam and water.  During storage, the lids should be kept tightly  sealed and protected from humidity.


The mixing ratio of 10 parts A  to 100 parts B by weight is critical.  Proportioning errors will affect the physical properties of the cured rubber.  Part B should be weighed into a clean metal, glass or plastic container, then the appropriate amount of part A can be weighed into the same container.  Do not use wood or paper mixing tools as they can introduce moisture.

While mixing, scrape down the sides of the mixing container several times to insure thorough mixing of both components.  Vacuum degassing will help to provide void-free molds but is usually not necessary.  Allow to cure overnight (16 hours minimum) at room temperature of 72°F before demolding.  Ultimate properties are reached in 3 days.  Curing in a warm location, up to 150°F will greatly accelerate the curing speed.

STORAGE:  PMC724 will remain usable for at least six months from date of manufacture in unopened containers stored in a cool, dry place.  Cured molds will slowly soften with age due to absorption of humidity.  The best way to store cured rubber is in tightly sealed plastic bags (to seal out moisture) and place in a cool, dry, dark place.  With proper care molds should not soften appreciably for 4 or 5 years.                  

PMC724 is available in the following sizes:

                                Pint kit                    1 lb                                         

                                Gallon kit               9.9 lb      

                                5 Gallon kit            49 lb

                                55 Gallon Kit        

 Warning:  Uncured product may cause respiratory or skin irritation with possible sensitization. Use only with adequate ventilation. If skin contact occurs, wash thoroughly with soap and water. In case of eye contact, flood with water and call a physician. Use of gloves and face shield is recommended.  This product should not be used near food or where prolonged skin contact may occur.


Disclaimer:  This information is based on sources that we believe to be accurate. It is offered in good faith, but without guarantee, since conditions of use are beyond control. All  risk of use are assumed by the user.


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