DIR Return Create A Forum - Home
       ---------------------------------------------------------
       Chemistry:The Central Science
  HTML https://kolathechemist.createaforum.com
       ---------------------------------------------------------
       *****************************************************
   DIR Return to: Organic Laboratory Chemistry
       *****************************************************
       #Post#: 205--------------------------------------------------
       preparation of melamine-methanal resin
   DIR By: Michel
       Date: May 21, 2012, 12:46 am
       ---------------------------------------------------------
       apparatus: methanal solution, 40% bench NaOH solution,
       melamine, dilute HCl, universal indicator paper, water bath,
       thermometer.
       Method
       Measure 12cm3 methanal solution into a boiling tube. Add bench
       NaOH solution drop by drop until it is just alkaline. The
       universal indicator paper should turn dark green.
       Stir the solution, add 4g melamine. Inside a fume chamber, heat
       the mixture to 80'C on a water bath. Stir continuously until a
       syrup is produced.
       Add dilute HCl in drops until the reaction mixture becomes just
       acidic. The universal indicator should turn to buff color. Pour
       out the mixture on to a tin lid and heat to 160'C in an oven.
       The syrup forms a gel first, and then forms a brittle resin as
       polymerization and cross-linking proceeds. The brittle resin is
       crushed to produce pellets for moulding
       *****************************************************
       Page 1 of 1