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If one of the monomers in a copolymerization has a functionality greater than 2, a branched copolymer can be formed. It is also possible for the branches to react and create cross-links. In this way, “infinite” polymer networks called gels are made. Definitions: PA = probability that A reacts PB = probability that B reacts NAo = original number of A groups (@ t = 0) NBo = original number of B groups (@ t = 0) r=NAo/NBo Assuming A can only react with B: NAoPA = NBoPB and rPA = PB For gelation to occur, q, the fraction of all monomer units in the sample that form cross-links, must be greater than qc, the critical value of q: qc =1/(f-1) and q=(PAPBp)/(1-PAPB(1-p)) where f is the number of functional groups on the molecule with highest functionality. Additionally, only the highest functionality molecule reacts and causes branching, so another factor, p, must be considered. p = (functionality of branched molecule * number of moles)/(sum(functionality * number of moles of all molecules of that type)) For example, if 0.5 moles of trifuctional A, 1 mole of difunctional A, and 2 moles of difunctional B molecules were reacted: p = (3 *0.5 moles)/(2 *1 mole+3 *0.5 moles) = 1.5/3.5 = 0.43 The limiting reactant in this situation is A because NAo = 3.5 mol < NBo = 4 mol. Solving for PA gives the fractional conversion of limiting reagent required to react for gelation to occur.〔Rudin, Alfred and Choi, Phillip. ''The Elements of Polymer Science and Engineering, 3rd Edition''. 2012. Elsevier Science. p 410. ISBN 9780123821782〕 ==See also== *Pour point *Cold filter plugging point *Petroleum 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gel point」の詳細全文を読む スポンサード リンク
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