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~nitrogenes fter experimenting a bit with some fresly made methylricinoate I come to believe that the hydrophillic moment of the plasticizer is very import in determining the "stickyness" and "stiffness" of the plastique, especially with low % plasticizer, high density plastique... Whereas using motoroil alone as plasticizer gives an almost rocksolid plastique at 5-10% plasticizer, replacing 60-70% of the oil by methylricinoate makes it perfectly kneedable while not sticky, even at very small particle sizes. It is no coincidence that all plasticizers contain some hyrophillic groups. My theory is that the reppellant action of these groups towards the hydrophobic environment allows for a much better separation of the long chain molecules of the polymer to be plasticized, giving them far better mechanical properties. I noticed though that above a certain percent of methylricioate the plasticizer mix seems to become cloudy, probably due to some precipitation, or emulsification, of the PIB. Adding some oil, analogous to the C4 composition can overcome this and makes the plastique stiffer... Anayway, I'm quite pleased to have made 12% plasticizer plastique at 1.60-1.62 g/cc which has better mechanical properties than plah-doh. You can press it with your fingers to 0.5 mm thick without any cracking or tearing! 
---------------------------------------------------------- next post After drying the milled crystals, I add about 2.8% PIB and 6% plasticizer containing 60% methylricinoleate and 40% motoroil in gasoline as a solvent. The gasoline solvent must be completely evaporated before your start rolling the plastique. At this point the mixture deliberately contains too little plasticizer, because the stiffer the plastique is, the better is the crystal shaving you mentioned and erosion process upon rolling. Smooth surface to roll on is a must, I use a glass bottle filled with water for rolling on a glass cutting board. The rolling has to be continued for a VERY long time, and this is really not the fun part. I reckon for industrial manufacture this is done by mechanical means, but since this is out of reach for most amateurs there is no other option than to roll by hand.  As you keep on rolling the plastiqye, you will see it becoming more brittle in the beginning. This is due too an excess of air that works as a plasticizer, that is removed from the plastiqe, but after prolonged rolling you will notice that very gradually the plastique will become more cohesive again, due to rouding of the crystals by abbrassing against eachother. The longer you roll, the more pliable it will become... When all of that is done, (and you have probably put more energy in working on the plastique than is in the plastique itself  ) You add another 3.5-4% of methylricinoleate, depending on the crystal size, to make
it really pliable...ps: Methylricinoleate can be replaced by ethylricinoleate (or better, even higher alcohols) For transesterification I found the PDF attached very helpfull. (Tried to link to it, but didn't work )[EDIT]: For all clarity, ricinoate esters are derived from ricinoleic acid, which makes up 90% of the fatty acids from castor oil. The rapeseed oil PDF was just a guideline for the proper transesterification reaction conditions... [Edited on 22-12-2006 by nitro-genes] Attachment: EthylEsterofRapeOil.pdf (666kB) This file has been downloaded 327 times |
Quote: Originally posted by Bot0nist  |
| <a href="http://www.sciencemadness.org/talk/viewthread.php?tid=6151">Read this for a start.</a> A great thread. Reminds you that crystal
structure plays a significant role in effective plasticizing. Some tit-bits to get the mouth watering. In the future please use the forum search engine or "Google site: search" SciMad, so as to not seem like you want a spoon-feeding. Your next stop should also be the forum library. Lots of good publications. Good luck and be safe. [Edited on 11-2-2012 by Bot0nist] |
