Xencast P6 - porosity / bubbles

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Xencast P6 - porosity / bubbles

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cliveso	cliveso posted 8 Years Ago HOT Topic Details
Group: Forum Members Posts: 2, Visits: 15	Hello all, I have recently purchased some Xencast P60 and have cast some pieces with 5% polyurethane pigment. Unfortunately I'm getting lots of tiny bubbles stuck to the surface of the pieces and sanding makes them stand out even more. I'm wondering whether it's air introduced during mixing or gas generated during curing due to moisture contamination. If it's the latter case, could someone recommended a moisture scavenger or some other solution? Attached are pictures of an unprocessed piece and a finely sanded piece (1000 grit). Many thanks for your advice. Attachments DSC_0256.JPG (762 views, 716.00 KB) DSC_0255.JPG (737 views, 696.00 KB) Edited 8 Years Ago by cliveso
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Matt (Staff)	Matt (Staff) posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 680, Visits: 1.9K	Hi Clivesco, Thanks for the message; I've moved this to our technical support area. This definitely looks like a moisture reaction. Xencast P6 does have some effective moisture scavengers in already but in order to get the very best flow and mechanical properties from the resin the amount of moisture scavenger is less than our previous Fast Cast product. This means that if you're casting into a moisture rich substrate or mould then the moisture scavenging ability of the resin can be overwhelmed and you can encounter the foaming that your pictures show. It's not clear from the pictures; what type of mould are you casting into? Thanks, Matt Matt Statham Easy Composites / Carbon Mods - Technical Sales Tags bubbles foaming p6 silicone xencast
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cliveso	cliveso posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2, Visits: 15	Hi Matt, Thanks very much for your response. The mould I'm pouring into is made of condensation-cure RTV silicone from DWR Plastics. The mould itself is made by pouring into a CNC-milled Sikablock purchased from your site. The surface finish of the silicone mould is naturally somewhat rough. I'm only using PU pigment pastes purchased from your site; no filler is added. For mixing, I use ordinary plastic cups and wooden sticks (tongue depressors). I've tried microwaving the sticks before use but there are still bubbles. I've had the same problem with the now-terminated Fast Cast PU resin, but switched to the new resin for its greater strength. Could the silicone mould hold enough moisture to cause this? The pictures in my last message are the fifth casting made using the same mould. Should I try drying the silicone mould by heat? Thanks again. Clive
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Matt (Staff)	Matt (Staff) posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 680, Visits: 1.9K	Hi Clive, Condensation Cure silicone does harbour moisture and although it should be perfectly possible to use condensation silicone with the Xencast P6 it could be possible that either this particular silicone is holding more moisture than usual. We've tested Xencast P6 with a range of silicones but of course we've not been able to test it with them all. Is the silicone mould new or has it already made a few parts? - Also, do you wash the mould out (soapy water for example) before use? - If you do, this would be a prime candidate for a problem. It's strange that you had the same problem with the previous FastCast too; that resin has high levels of moisture scavenger in which made it very insusceptible to moisture reactions so I'm thinking there might be an issue with the process somehow. One last thing, the 'sediment' in the Part A is the moisture scavengers. Are you thoroughly shaking Part A to disperse the sediment before use? --Matt Matt Statham Easy Composites / Carbon Mods - Technical Sales
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