Technical Center Guide to urethane calculations Equivalent weight The equivalent weight (eq wt.) tells you how many grams of a product you need to have for one equivalent of reactive groups For an isocyanate, the reactive group is -N=C=O (NCO), and its concentration is measured by weight percent NCO Isocyanate equivalent weight = 4,200 g/eq NCO Example: 4,200 Isocyanate eq wt of Suprasec 5025 = = 136 g/eq 31.0 For a polyol, the reactive group is -O-H (OH) OH concentration is measured by the OH value (mg KOH/g sample): Equivalent weight of a polyol = 56,100 g/eq OH Value Example: Eq wt of ethylene glycol = 56,100 = 31.0 g/eq 1,810 While the information and recommendations in this publication are to the best of our knowledge, information and belief accurate at the time of the publication NOTHING HEREIN IS TO BE CONSTRUED AS A WARRANTY, EXPRESSED OR OTHERWISE In all cases, it is the responsibility of users to determine the applicability of such information or the suitability of any product for their own particular purpose The sale of any products referred to in this publication is subject to the general terms and conditions of Huntsman International LLC or its affiliated companies ‘Suprasec’ is a registered trademark of Huntsman International LLC The mark is registered in one or more countries, but may not be registered in all countries Copyright © Huntsman International LLC 2001 All rights reserved 07/2001 Visit our website at www.huntsman.com/pu/ace Contact us at ACE@huntsman.com Technical Center Guide to urethane calculations Molecular weight of a polyol The molecular weight (mol wt.) of a polyol is approximated by the polyol equivalent weight (eq wt.) multiplied by the nominal functionality (fn) 56,100 Polyol mol wt = (eq.wt.)(fn) = (fn) g/mole OH value 56,100 Mol wt of any diol = (2) g/mole OH value 56,100 Mol wt of any triol = (3) g/mole OH value Example: Mol wt of ethylene glycol = 56,100 (2) = 62.0 g/mole 1,810 While the information and recommendations in this publication are to the best of our knowledge, information and belief accurate at the time of the publication NOTHING HEREIN IS TO BE CONSTRUED AS A WARRANTY, EXPRESSED OR OTHERWISE In all cases, it is the responsibility of users to determine the applicability of such information or the suitability of any product for their own particular purpose The sale of any products referred to in this publication is subject to the general terms and conditions of Huntsman International LLC or its affiliated companies ‘Suprasec’ is a registered trademark of Huntsman International LLC The mark is registered in one or more countries, but may not be registered in all countries Copyright © Huntsman International LLC 2001 All rights reserved 07/2001 Visit our website at www.huntsman.com/pu/ace Contact us at ACE@huntsman.com Technical Center Guide to urethane calculations Total weight of MDI required for reaction MDI = Diphenylmethane Diisocyanate When reacting an isocyanate with one or more polyols to form a polyurethane, one NCO group reacts with one OH group When the number of NCO groups equals the number of OH groups, you have a stoichiometric NCO : OH ratio of 1.0 This ratio is commonly referred to as the index To determine the amount of MDI required to react with a given polyol blend, you must know the desired index (often 1.0), the MDI equivalent weight (MDI eq wt.), and the weight fractions (pbw) and equivalent weights of the polyols and any water present in the blend Total weight of MDI required = (index)(MDI eq wt.) pbw polyol A + pbw polyol B eq wt polyol A +………+ eq wt polyol B pbw polyol N + eq wt polyol N pbw H O eq wt H2O Example formulation: Say you have the following polyol blend and would like to determine the amount of Suprasec 5025 to add to achieve a fully reacted polyurethane with a slight excess of isocyanate (target index = 1.05) Polyol A (OH value = 490) Butane diol (BDO); (eq wt = 45) Water Suprasec 5025 (% NCO = 31.0%) 100.00 20.00 0.15 X 100 X = pbw MDI = (index)(MDI eq wt.) + eq wt polyol A X = (1.05) 4,200 100 31.0 56,100 490 + 20 45 + 0.15 Copyright © Huntsman International LLC 2001 All rights reserved 07/2001 eq wt BDO + 0.15 eq wt H2O = 190 pbw MDI While the information and recommendations in this publication are to the best of our knowledge, information and belief accurate at the time of the publication NOTHING HEREIN IS TO BE CONSTRUED AS A WARRANTY, EXPRESSED OR OTHERWISE In all cases, it is the responsibility of users to determine the applicability of such information or the suitability of any product for their own particular purpose The sale of any products referred to in this publication is subject to the general terms and conditions of Huntsman International LLC or its affiliated companies ‘Suprasec’ is a registered trademark of Huntsman International LLC The mark is registered in one or more countries, but may not be registered in all countries 20 Visit our website at www.huntsman.com/pu/ace Contact us at ACE@huntsman.com Technical Center Guide to urethane calculations Calculation for formulating a prepolymer to a specific percent NCO (or equivalent weight) To calculate an MDI prepolymer, Let N = desired NCO of the prepolymer (expressed as a fraction) Let X = equivalent weight of the diisocyanate Let Y = equivalent weight of the polyol (or average equivalent weight of the polyol blend) Total amount of MDI needed = X + N (X+Y) 42 - N X Example: Say we want a 10.0% NCO prepolymer of Suprasec 1306 (%NCO = 33.5%) with a polyol blend consisting of 95% polyol B (OH value 28) and 5% ethylene glycol (OH value 1,810) by equivalent weight: N = 0.10 X= 4,200 = 125 g/eq 33.5 Y= 56,100 28 (0.95) + 56,100 (0.05) = 1,905 g/eq 1,810 Total amount of MDI needed = 125 + 0.10 (125+1,905) = 985 pbw Suprasec 1306 42 - 0.10 125 So 1,903 pbw polyol B, 1.55 pbw ethylene glycol, and 985 pbw Suprasec 1306 would be used to produce this prepolymer at 10.0% NCO Converting to weight percents, Amount of Suprasec 1306 = Amount of polyol B = Amount of ethylene glycol = 34.09% 65.86% 0.05% While the information and recommendations in this publication are to the best of our knowledge, information and belief accurate at the time of the publication NOTHING HEREIN IS TO BE CONSTRUED AS A WARRANTY, EXPRESSED OR OTHERWISE In all cases, it is the responsibility of users to determine the applicability of such information or the suitability of any product for their own particular purpose The sale of any products referred to in this publication is subject to the general terms and conditions of Huntsman International LLC or its affiliated companies ‘Suprasec’ is a registered trademark of Huntsman International LLC The mark is registered in one or more countries, but may not be registered in all countries Copyright © Huntsman International LLC 2001 All rights reserved 07/2001 Visit our website at www.huntsman.com/pu/ace Contact us at ACE@huntsman.com ... Center Guide to urethane calculations Total weight of MDI required for reaction MDI = Diphenylmethane Diisocyanate When reacting an isocyanate with one or more polyols to form a polyurethane, one...Technical Center Guide to urethane calculations Molecular weight of a polyol The molecular weight (mol wt.) of a polyol is approximated... website at www.huntsman.com/pu/ace Contact us at ACE@huntsman.com Technical Center Guide to urethane calculations Calculation for formulating a prepolymer to a specific percent NCO (or equivalent