Ramie yarn was purchased from Hunan Huasheng Dongting
Ramie Textile Co. Ltd., China. Tin (II) octoate (99%), triphenyl phosphite
(TPP), 1,6-hexane diisocyanate (HDI), 4,40-diphenylmethane
diisocyanate (MDI) and isophorone diisocyanate (IPDI) were purchased
by Sinopharm Chemical Reagent Co. Ltd.,