Effective Functionality and Intramolecular Reactions of Polyisocyanates and Polyols

Gel point prediction of metal‐filled castor oil‐based polyurethanes system

“…Flory and Stockmayer have defined the gel point as an extent of critical reaction and the conditions for the critical gel point have already been expressed [15,16,25,26], which shows that the gelation phenomenon in the present system is dependent on the polyol functionality. The conversion calculated by the above equation differs widely from the experimental conversion.…”

“…A similar trend was found at 40, 50, and 60°C. The gel point conversion for the unfilled system was calculated from the following relationship [25,26]:…”

Sophorolipid-Based Oligomers as Polyol Components for Polyurethane Systems

“…However, because f LSL is larger than two, crosslinking is substantial and thus the point of gelation must be considered when different stoichiometric NCO/OH ratios (indices) are applied. The point of gelation can be calculated applying the Flory–Stockmayer relation (1) [ 44 , 45 , 46 ]. with p OH and p NCO = conversion of OH and NCO groups, respectively, and f OH and f NCO = functionality of the OH and the NCO component.…”

“…In contrast, complete conversion of all OH groups leads to significant crosslinking and therefore to a thermosetting material. Considering the Flory–Stockmayer relation [ 44 ], the degree of crosslinking and thus the nature of the thermosetting material can be tailored to a certain extent, e.g., by appropriate choice of the NCO/OH ratio (index) [ 44 , 45 , 46 ]. In summary, SL provide a high number of potential reaction sites with different reactivity toward NCO groups and should therefore be suited as crosslinking agent and potentially as a linear building block [ 32 ].…”

Curing theory of the Aai–Bbj type polycondensation. (I) intramolecular cyclization and gelation equations

“…Since then, many investigations have been published on solving the problem of cyclization of non-linear polymers.' - 6 In recent years, the authors have investigated in detail the ringshain competition in non-linear polycondensations and obtained a series of important results by use of the molecular model of branching trees and the basic principles of probability and conformation theories7 In this paper, we deal with a more complicated system, Aai-Bbj type polycondensation.…”