Ntxiv paraformaldehyde rau cov kua dej urea (thawj feem), cua sov rau 60 degree, thiab kho cov pH rau 7 siv sodium hydroxide. Reflux qhov sib tov rau 20 feeb, kho cov pH rau 5 nrog formic acid, thiab reflux rau lwm 30 feeb. Tom qab ntawd, tshem tawm cov sib tov nrog 40% sodium hydroxide tov, ntxiv urea (thib ob feem), thiab kho cov pH rau 5.8 siv cov tshuaj formic acid. Thaum kawg, kub hauv qab reflux kom txog thaum lub viscosity nce mus txog 11.5 cP (ntawm 20 degree) kom tau cov nplaum.
Txhawm rau siv cov nplaum, ua ntej roughen cov khoom sib txuas siv lub tshuab roughening lossis ntawv xuab zeb. Tom qab ntawd, siv cov nplaum rau ntawm qhov chaw yuav tsum tau sib txuas; Tom qab lub sijhawm luv luv, koom nrog ob qhov chaw ua ke thiab nias lawv kom ruaj khov siv cov khoom hnyav.
