Re: ShopTalk: Cure Temperature/Time

[Bernie Baymiller]

Title: RE: ShopTalk: Cure Temperature/Time

Brian,   >I know that at 77* the 24 cure epoxy is supposed to cure in 24 hrs, but I also remember people using hot boxes to speed cure time.  A few questions, 1.  Does a higher temperature reduce the strength of the epoxy?    To my knowledge, after reading some data sent in by a Shoptalker several years ago, a temperature of about 140° will strengthen the bond. I've been curing GS 24-hour epoxy with a heating pad on high for several years and have had no problems. Other epoxies may vary.   >2.  How much does a higher temperature speed up the cure time?   I've hit my heat-cured heads in as little as 4 hours. It'll set up so you can't move the head in about 1-1/2 hours.    >3.  Is there a maximum temperature?   I'm sure there is, but don't know what it is. The table below might give you some idea.   Here is some of the GS information on heat curing epoxy that I saved:   "Date: 10-DEC-99 Author: Golfsmith Technical Dept. (Golfsmith) Subject: Re: Re: Epoxy and cold weather Dave: Here is some information we obtained from the our epoxy supplier. "All room temperature (ambient) cured epoxies can be accelerated by moderate heat (66C-82C) to speed the reaction between the epoxy resin and hardener. However, curing these systems at very high temperatures may adversely effect bond strength because of the following: The heat from the reaction exotherm combined with the externally supplied heat may char the epoxy system or cause outgassing and bubble formation, resulting in poor strength. Premature system gelation or interlocking of molecules restricts mobility of the molecules within the matrix and may result in an incomplete reaction. On the other hand, most room-temperature, cured epoxy systems give better bond strength at moderate heat cure as compared to room-temperature cure. This is because of the better "wetting" of the substrate because the surface energy of the mixed epoxy is lower and the viscosity is lower." Our standard 24 hour shafting epoxy cures to a shear strength of 3500 PSI at 18 hours at 25 C. When the temperature is increased to 82C (180f) for one hour, the strength is 3650 psi. At 66C (150f) for two hours the strength is increased to 3800psi. As a table (DMT added): Temp*C Temp*F Cure Time Shear Strength 25 77 18 hr 3500 psi 66 150 2 hr 3800 psi 82 180 1 hr 3650 psi I hope this helps. Mark Ehly " I think the Admiral uses a couple of 100 watt bulbs in a box...is that correct, Al? Shoptalker Chris Burns uses a couple of those portable work lights for a heat source. When I finally get to build myself a real clubmaking shop, hot work lights sound like the best way to go. Here's what he says about the light positions: "When I use the large light, I'd say it is about 12" from the clubs. I've used a thermometer and measured the temperature in the area to be about 120°.  It's always worked fine and I've never had any problems. The clubs get hot enough to begin to be uncomfortable to touch with your hand.  They never get hot enough to affect a ferrule, for example." Hope this helps. Bernie Writeto: [EMAIL PROTECTED]