I have pellets of Nylon-12, and I am looking to form flat sheets. The published glass transition temperature is 41C and the melting point is around 180C. I am putting ~1g of pellets in a heat press at 120C under 500 lbs of force, and they are barely deforming, let alone merging to for a flat sheet. Why might this be? I wold assume that I am high enough over the Tg that they should still compress. Is Nylon still too hard after softening?
Ideally, I am looking for a polymer that experiences significant softening at around 40-45C. If this nylon is not appropriate, is there an other polymer that might be compatible with this application?
Hello dear, the nylon is not appopiated for it, since it has high melting temperature, but you can looking for HDT values of differents polymers, because the comoon thermoplastic polymers have not HDT values so low.
You have a semi-crystalline material. This means while the non-crystalline parts of your material will become softer above Tg the crystalline parts will not soften that much as long as the crystall structure is not molten.
However, you will have a chance of deforming the material if your forces are high enough and they just are not. 500 lbs are about 2.5 kN? You will surely find a press with much higher maximum force (or use just one pellet). Of course it is nice, if the press can be heated to a certain temperature, but if this is not the case you will probably succeed if you heat up the pellets before pressing.
Your "pressed" sheets will probably have worse mechanical and optical properties than sheets produced by casting them on a flatfilm line or blowing them since the pellet's interfaces will be weak spots in sheet.
If making this sheet by pressing is not your main goal and you just need a sheet with certain properties (which?) you can probably just buy it ;) Or - depending on the amounts you require - ask a manufacturer for some discarded/scrap material.
Also: A lot of packaging materials for food have a thin PA-layer inside - you might have the right material already at your hands ;)
Thanks for the information, Matthias. I am trying to modify the PA with filler material before I press it into sheets (which I have been doing by mixing it with a solvent), so unfortunately, I cannot simply buy it. It seems that this material is too crystalline for my purposes since in my desired application, I need significant softening to occur in the sheet, so I will look into the alternatives. Your post was very elucidating!
You also have a chance of producing an amorphous (or at least mor amorphous) material from your PA. If you melt it and quench it quickly, the crystall growth is reduced or sometimes even completely eliminated. You probably have a DSC at hand: you can try this quenching by running a melting procedure (1st heating cycle) and remove the hot pan/probe manually and put it on something rather cold. If you perform another heating cycle with this material, you should observe a recrystallisation before your melting temperature which means you have reduced your crystallization ratio by quenching.
For semi-crystalline polymers at tg, polymer chain end moves and pressing film requires "bulk movement of chains" which occurs above the Tm. No matter how high the pressure is at 120 C, Nylon 12 will not melt at 120 C if Tm is 180 C. As said above, it is highly crystalline material and would soften only close to their Tm. There are some low Mw materials that may form a sheet at 45 C. I do not know of any thermoplastic polymer which will melt at 45 C and is thermally stable over long period. Your other option is to use thermoset (polyester or like) cast film from solution or monomer (e.g. in PU, MMA). You can also look at copolymers but again that will not reduce Tm to 45 C !
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