gained by drying for 24 hours on any of the samples (two of the systems actually had higher strengths at 12 hours). Does this mean that drying for 24 is a waste of time? Not necessarily. When parts are to be steam dewaxed, any residual moisture can be detrimental to the shell because of the large expansion that occurs when water is turned into steam. Drying for longer times may not increase strength, but it reduces the potential for autoclave-related cracking. Also, it should be remembered that the samples run here do not correspond to normal production parts in size or complexity.
Figure 5: MOR versus inter coat dry time (24 Hour Dry Time) Conclusions
Under the drying conditions used in this study, it was found that dry times of four hours between dips produced maximum or near maximum green and fired modulus of rupture strengths. There was no real difference in strength when samples were dried for 12 or 24 hours after the sealcoat was applied, though it should be noted that the configuration tested, MOR bars, represent a wide open, relatively easy to dry sample. When insufficient dry time is used (in this experiment, one or two hours between dips), shell strength will be very low. Increasing the final dry time does not make up for the lack of bond strength lost by dipping too rapidly.
Figure 6: Percentage change in strength with 24-hour final dry time
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Information and recommendations based on research and technical data believed to be reliable. Offered free of charge for use by persons with technical skills, at their own discretion and risk, without guarantee of accuracy REMET makes no warranties, express or implied, and assumes no liability as to the use of its products or of any information pertaining thereto. Nothing herein is intended as a recommendation to infringe any patent.
Figure 7: Comparison of all MOR Data June 2020 ❘ 25 ®
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