Improved Mold Release Advantages: with Zinc …

1 Table 1: EPDM mold Release 1 2 3 4 5 6 7 NORDEL 1040 100 100 100 100 100 100 100 N762 BLACK 100 100 100 100 100 100 100 SUNPAR 2280 50 50 50 50 50 50 50 zinc OXIDE 5 5

2 5 5 5 5 5 STEARIC ACID 1 1 1 1 1 1 1 RESIN D 1 1 1 1 1 1 1 DICUP 40KE SR633 2 2 2 2 2 2 2 zinc STEARATE 0 1 2 4 10 LAP SHEAR ADHESION, CRS 320 F/20 MIN 310 330 270 170 130 100 15 mold Release Fail Fail Fail Fail/Pass Fail/Pass Pass Pass HARDNESS 50 50 50 50 50 52 52 TENSILE STRENGTH PEAK, PSI 1000 1030 960 960 1050 1030 1080 ELONGATION, % 980 1000 840 910 920 990 1060 MODULUS100.

3 PSI 130 130 130 140 140 140 130 Improved mold Releasewith zinc StearateDescription:Cray Valley Company offers a variety of metalliccoagents for peroxide curing elastomers. SR633 iszinc diacrylate, SR634 is zinc dimethacrylate,SR709 is zinc monomethacrylate and SR636 iscalcium diacrylate. These coagents offer improvedmechanical properties in the cured elastomers, suchas tensile strength, tear resistance, higher elongationand Improved rubber to metal is this Improved rubber to metal adhesion thatcauses problems with mold sticking forapplications not requiring good has been found that formulations can be modifiedwith zinc stearate to reduce mold sticking withoutadversely affecting physical properties.

4 Externalmold Release spray systems can still be used inconjunction with the internal zinc stearate moldrelease : Tailor zinc Stearate to Coagent Concentration No Loss in Properties for EPDM Use with External Release Agents Low Cost Works in Most Elastomers Reduces Mooney Viscosity Non Blooming Replace Other Fillers with zinc StearateMold Release MeasurementsMold Release was measured by two methods. Lapshear adhesion (ASTM D816-55) to cold rolledsteel was used as a laboratory test to quantify theadhesion characteristic of the varying zinc stearateconcent-ration. This measurement was checkedagainst the subjective mold Release of the 75 milplaque mold . In all cases, the two methodscorrelated making it possible to graph the Properties: EPDMThe effect of varying zinc stearate on mold releaseand properties using SR633, zinc diacrylatecoagent, is shown in Table 01/10 APPLICATION BULLETINO aklands Corporate Center, 468 Thomas Jones Way, Suite 100, Exton, PA 19341 Toll Free 877-871-2729 Formulation: EVAT able 2 shows the effect of zinc stearate on moldrelease at PHR SR633 in ethylene vinyl acetatecopolymer Elvax 240.

5 EVA optimum results wereachieved at 5 phr zinc stearate. mold Release at thisconcentration was good and above this zinc stearatelevel, properties appear to diminish as shown inFigure 2 Table 2: EVA mold Release PHR SR633 Increasing the zinc stearate concentration from 0to 10 PHR resulted in a progressive improvementin mold Release . At the same time, tensilemodulus100 remained constant as shown in Figure1. In the range of 5-10 phr zinc stearate, moldrelease was considered 1 ELVAX 240 100 100 100 100 HISIL 230 25 25 25 25 zinc OXIDE 3 3 3 3 STEARIC ACID 3 3 3 3 TOTM 3 3 3 3 PERKADOX 1440 2 2 2 2 SR633

6 zinc STEARATE LAP SHEAR ADHESION, CRS 320 F/25 MIN 640A 240A 150A 125A mold Release Fail Fail Fail/Pass Pass ODR, 320 F ML, IN-LB TS, MIN TC(90) MIN MH, IN-LB MH-ML, IN-LB EVA: Alternate CoagentsSimilar mold Release responses were obtained withzinc dimethacrylate, (SR634) and calciumdiacrylate, (SR636).

7 For SR636, the calciumstearate was used to maintain the same metal recommended zinc stearate (for SR634) andcalcium stearate (for SR636) levels again are 5 is postulated that the zinc stearate competes withthe zinc ion in the cured zinc diacrylate network toreduce the number of high energy sites availablefor bonding at the metal surface. As the metal sur-face energy is reduced, mold Release is obviouslyimproved. The metallic stearates work with anymetallic PrecautionsMaterials in this formulation can cause eye and skinirritation and have potential to cause skin sensiti-zation in susceptible individuals. Proper industrialhygiene practices should be utilized. Consult theappropriate MSDSs before using any chemical inthis information in this bulletin is believed to be accurate, but all recommendations are made without warranty since the conditions of use are beyond Cray Valley Company'scontrol.

8 The listed properties are illustrative only, and not product specifications. Cray Valley Company disclaims any liability in connection with the use of the information,and does not warrant against infringement by reason of the use of its products in combination with other material or in any process.