I have equivalent weights of polyols and isocyanate used in polyurethane resin and I want to know the cross-link density theoretically.
Thanks in advance.
Regards,
Raviteja.
Dear Raviteja Polyurethanes are a bit special. In principle, if you use only diols (polyols and chain extenders) you will get only linear molecules. If you use in part triols either as polyol or as chain extender and/or triisocyanates, you can calculate the crosslink densitiy using the Flory Stockmayer theory (https://en.wikipedia.org/wiki/Flory-Stockmayer_Theory). There are side reactions, however, (http://www.nkmetal.com.cy/images/pages/company_academy_research/BME.pdf) which cannot be neatly predicted and may distor the calculations. In order to prepare purely linear PUR special conditions are necessary. Most PUR-s a re slightly or heavily crosslinked.
Dear Raviteja Polyurethanes are a bit special. In principle, if you use only diols (polyols and chain extenders) you will get only linear molecules. If you use in part triols either as polyol or as chain extender and/or triisocyanates, you can calculate the crosslink densitiy using the Flory Stockmayer theory (https://en.wikipedia.org/wiki/Flory-Stockmayer_Theory). There are side reactions, however, (http://www.nkmetal.com.cy/images/pages/company_academy_research/BME.pdf) which cannot be neatly predicted and may distor the calculations. In order to prepare purely linear PUR special conditions are necessary. Most PUR-s a re slightly or heavily crosslinked.
Dear Gyorgy, Thanks a lot for adding the answer. That really helped in advancing forward in my understanding.
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