Rotational moulding prototype moulds

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#1

Hi There,
I’m trying to develop a fibre glass mould to make a run of prototype roto moulded plastic kayaks.

We’ve had limited success so far getting about 3 boats before the heat destroys the fibre glass mould. The lay up we are using at the moment is neo gel gelcoat, standard polyester resin with 2 layers of 1.5 ounce chop strand matt and extra 2 layers of 1.5 around the flange.

Obviously the heat of the oven the mould is going into is the main problem. Anyone know of heat resistant fibre glass materials?

Does anyone have any ideas or know of anyone out there who is currently doing this with more success? I have seen claims on the net of up to 50 boats before the mould is unusable.

Really appreciate any thoughts people might have out there.
Phil

#2

I’d use an Isopthalic resin if I were you. ISO can handle at least 260 in my experience.

#3

Epoxies. Huntsman Aradlite (sp?) has a 355f service epoxy. MY721 I think. Stuff is thicker than cold cornsyrup at RT though :-/

#4

Start by reading the technical datasheets…

A good start is to let us know the temperature of the oven…

#5

Thanks for the input so far.
The Oven is running at 160 degrees C

#6

In that case there are several options, among them Momentive 04434, but also Huntsman systems that can be laminated decently. Make sure the Tg is 180+. This does require an elaborate postcure, with ramp rated and dwell times. Make sure you can control and influence your oven.

#7

Thanks Herman,

We’re wanting as low a time investment as possible so we’re trying to avoid post curing if we can. have you had any experience of using Isopthalic polyester in this area?

#8

Forget 180C without postcuring. You are better of chasing unicorns.

All iso resins I have will not meet 180C. Actually no polyester will. I did some searching for you: I checked HDT values of Polynt, Ricco, Scott Bader and Reichhold resins. Highest is some 128 degrees C or so. (after postcure)

For Tg 180 degrees C (the minimum for a high quality mould) you need either Momentive 04434 or Huntsman 8615 (Hand laminating). At least that is what I would recommend my clients.
For infusion you could use similar products, like Huntsman LY8615 resin with XB5173 hardener. (Tg 200-207C)

Yes, these come with an elaborate curing cycle, but saving on that seems really daft.

Fiddling with these temperatures leaves very little margin for error or cutting corners.

#9

Thanks Herman,
I really appreciate the effort you went to.
It’s people like you that make forums the valuable resource that they are.

#10

Do you have any recommendations for the cloth used to lay up? (material, weight, number of layers)
On average a mould would be about 7ft x 3ft x 1.5ft