When using epoxy or polyester for molds ?

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When using epoxy or polyester for molds ?

When using epoxy or polyester for molds ?

Author	Message
Zorongo	Zorongo posted 10 Years Ago HOT Topic Details
Group: Forum Members Posts: 40, Visits: 330	Hi all. I'm making small size epoxy parts, but sometimes I've made them whith polyester. Room temperature curing, hand lay up with small presure over the laminate (counter mold) I had demolding problems with a polyester mold and someone told me a "rule of thumb": Use polyester molds for polyester parts and epoxy molds for epoxy parts. (I'm actualy using PE molds for epoxy parts without any problem) So, the question is: Whe should I use epoxy molds ? An epoxy mold seems to be better fron the dimensional stability point of view.. It also seems logical to make the molld similar to the part if high temp increases are expected (prepregs, exotherms ?) to reach a similar diatation / contraction on both and avoiding stresses.... Could you please share your experience ? Thanks in advance
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biker_kev	biker_kev posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 5, Visits: 85	Hi, Your post shows you have had first hand experience of why you use epoxy tooling for epoxy mouldings and polyester tooling for polyester mouldings. If you mix the two resin types you will have great trouble demoulding your parts, to the extent you will probably end up scrapping them. Regards Kevin
	Reply Like 3
Matthieu Libeert	Matthieu Libeert posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 955, Visits: 3.4K	here are some tips and tricks I can give you. polyester wont stick to epoxy (low) epoxy will stick to polyester (hard) epoxy will stick to epoxy (medium) polyester will stick to polyester (medium) So If you apply this on a mould: Epoxy mould with polyester part OK polyester mould with epoxy part NOT OK BUT! if you postcure your polyester moulds and give them some time to let them evaporate the styrene and use some good release agent or in this case even better PVA you should be ok with it. polyester moulds are cheaper to make, can use chopped strands but are less stable at higher temperatures and will have more shrinkage. Vinylester gelcoat is a good alternative, compatible with epoxy and polyester sure other might correct me, or have some more information Matthieu Libeert Founder MAT2 Composites X Sports website: www.mat2composites.com
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baja_patient	baja_patient posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 135, Visits: 1.6K	all of the above! ^^ Rightly said, if you let all the styrene outgas from the part then it should be okay. Would I do it? no, probably not. I will use the unimold system which utilizes a vinylester gelcoat. cheers
	Reply Like 3
Zorongo	Zorongo posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 40, Visits: 330	Thanks for the answers. I didn't pay attention to the styrene matter. I've been using PE molds for Epoxy parts and normally without any problem. So I thought it was more a question of the release agent as following same process one wax gave me best results than other. I was thinking on PVA a a phisycal barrier, too.... Probabily I'll go to VE for next ones. And maybe postcuring to evaporate styrene. (And maybe also a layer of PVA "jaust in case"?) Thanks again !
	Reply Like 2
Warren (Staff)	Warren (Staff) posted 10 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 8.5K	PVA is a good barrier release agent for issues like this with "green" moulds. The styrene can still cause problems with waxs and chemical release agents. It is common practice with traditional moulds made in polyester to either wait for the mould to season a little, or use PVA for the first few pulls to get around any issues with styrene still being present. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
	Reply Like 3
Zorongo	Zorongo posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 40, Visits: 330	OK, thanks all !
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kidpaint	kidpaint posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 99, Visits: 676	not to thread jack but I have a question along these lines. My uncle has some motorcycle fender molds he no longer uses and they will work good with my bike. The molds are over 10 years old but still in good shape as they were made thick and with braces to stop as much warping as possible. I am wanting to use epoxy resin to make some carbon fiber fenders, but the molds were made with PE resin. If I use PVA on the molds and since they are old. WIll this be a problem? I am only producing these for myself and would like to avoid mold making costs if at all possible. I am wanting to infuse the fenders. If it will be, then I will make new molds. These are universal chopper fenders and there could be a call for more if I marketed them to help with mold costs, but im terrible with that stuff lol
	Reply Like 3
Matthieu Libeert	Matthieu Libeert posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 955, Visits: 3.4K	should work fine! if you are not sure, you can apply release and try a small piece with fiberglass and polyester and see if the demoulding goes well and if the mould is still ok Matthieu Libeert Founder MAT2 Composites X Sports website: www.mat2composites.com
	Reply Like 3
fgayford	fgayford posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 433, Visits: 1.2K	Zorongo (11/02/2015) Hi all. I'm making small size epoxy parts, but sometimes I've made them whith polyester. Room temperature curing, hand lay up with small presure over the laminate (counter mold) I had demolding problems with a polyester mold and someone told me a "rule of thumb": Use polyester molds for polyester parts and epoxy molds for epoxy parts. (I'm actualy using PE molds for epoxy parts without any problem) So, the question is: Whe should I use epoxy molds ? An epoxy mold seems to be better fron the dimensional stability point of view.. It also seems logical to make the molld similar to the part if high temp increases are expected (prepregs, exotherms ?) to reach a similar diatation / contraction on both and avoiding stresses.... Could you please share your experience ? Thanks in advance I use polyester gelcoat and resin for my molds all the time. I use a chemical release like easylease and have never had a sticking problem when using epoxy in them. I even once used prepreg in a polyester mold in my oven and had no issues at all. The key is to apply the release as in the instructions and not as one assumes it should be used. Here is a priceless tip for you to use. After you polish your mold stick down a 5 inch piece of masking tape onto the mold surface. Now peel the tape off and notice how hard it resists coming off. Now apply as instructed a few coats of chemical release. Do the tape test again. Notice how much easier it comes off. Now complete your coats of chemical release the tape should practically fall off. You now know for sure how active your surface is and your ready to go. I would never dare to risk a mold unless I first checked the surface with tape. This technique should not be used on PVA as it will pull the PVA layer off. Hope this helps. Fred
	Reply Like 2