Demolding aid

Flat parts with sufficient draft angle on the side do not require additional demolding aids. Flexible and semirigid integral skin foam parts can be ejected using compressed air. Rigid PUR integral skin foam products are ejected with mechanically or... 

Add wood furnish (384 g, moisture content 6.02%) to the bowl of a rotary blade paddle mixer (such as a Kitchen-Aid KSM90) and agitate at the lowest speed setting. Add Mondur 541 (7.39 g, 1.9% w/w, a polymeric diphenylmethane diisocyanate of 31.5% NCO, Bayer) dropwise over a 5-min period using a disposable syringe. Continue blending for an additional 10 min and then transfer the blend to an 8 x 8 x 2 -in. metal form at the bottom of which is a metal plate which fits inside. The resin-coated furnish is evenly spread inside the form and another metal plate is placed on top. All parts of the form and plates are presprayed with mold release. The completed form assembly is placed into a hydraulic press (such as a model PW-22 manufactured by Pasadena Hydraulics) with platens heated at 350°F. The furnish is then pressed between the two form plates to a thickness of j in. Press controls are used to ensure consistency of board thickness. The assembly is heated for 4 min. before demolding the cured wood panel. 

As with other mold operation process mold release agents are usually required because the plastic melt can adhere to the surface of the mold cavity. Molds with very little or no draft usually require a release agent. Like other molding operations, a textured cavity can provide a textured product surface. Most texturing of cavities is by chemical etching so it is important to use the appropriate mold material to create a particular texture. An effective release is needed at the parting line to aid in demolding. 

For Hifax PP/EPDM blends, a general purpose screw is recommended. The clamping pressure increases with part size. The nozzle should be as short as possible with orifice larger than usual. All tools should be vented trapped air may cause localized burning, surface sinks and voids. Keeping the moving half of the mold cooler than the stationary part aids demolding. 

Necessary demolding and ejection aids (for example, slide mold, split mold, etc.)... 

Small areas can also be demolded with negative draft angles (undercuts). During this process, the molded part can be deformed or stretched. When overstressing, traces can be found on the finished part (e.g., stress whitening). (Bigger undercuts can he demolded with the aid of loose parts). 

Attention must be given to the volatility of the processing aid when selecting one for FKM fluorinated rubber. A good example is dioctyl phthalate (DOP) since the inclusion of 2.00-3.00 pphr of DOP will result in volatilization of it during demolding and oven post-cure. The finished parts will be undersized, hence the mold cavities must be cut to allow for the increased shrinkage. 

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