Isocyanate index calculation. The calculation is based on the equivalent weight (EW) of each compound. This method is used to determine of reactive Isocyanate groups in resins and similar materials. The analytical values required for isocyanate formulas are the isocyanate value, hydroxyl number, residual acid value (acid number), and water content. When reacting an isocyanate with one or more polyols to form a polyurethane, one NCO group reacts with one OH group. 0. Index is most often considered a dimensionless value (not a percent), as it is the ratio of the equivalent amount of isocyanate used relative to the theoretical equivalent amount times 100. Calculate NCO/OH ratio and NCO index from %NCO, OH number, and parts by weight. Titration of Isocyanates (NCO value) in polyester and polyurethane resins according to DIN EN ISO 14896. Above 100 means an excess of isocyanate; less than 100 means a shortage, or an excess of polyol. Some manufacturers specify this number directly and others give the percent NCO by weight (isocyanates) or the hydroxyl number in g-OH/g (polymer resins). Each of these must be converted to an EW to calculate the curative C = A + B The actual amount of TDI to be used is calculated as follows: Actual TDI Amount = (A+B)*Isocyanate Index Example Calculation: For 100 parts by weight of polyethylene adipate, with a hydroxyl value of 56, an acid value of 0. 05) Polyurethane Calculation Guide This document provides guidance on calculations for urethane formulations including: - Equivalent weight calculations for isocyanates and polyols based on NCO% and OH value respectively. 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. Parts by weight can be any consistent weight basis (phr, grams, etc. Some people use poor (though accurate) terminology and say ‘poly rich’ rather than saying ‘under How To Calculate The Isocyanate Dosage In Polyurethane Flexible Foam And Semi-rigid Foam Formulations--Part 3 Ennuo Innovative Chemistry Your Trusted Supplier for Polyurethane Foam Raw Materials An index of 1 is appropriate for solvent systems. Nov 20, 2025 · This article introduces how to calculate theoretical ISO demand, RATIO, and ISOCYANATE INDEX in HR polyurethane formulations to ensure accurate and stable foam performance. 0 parts by weight in the formulation. The last two The isocyanate density was cal- culated by percent of isocyanate multiplying by the density of PU foams (Table 6). ) as long as both components use the same basis. An excess of isocyanate groups is used in some applications like flexible foam. When the number of NCO groups equals the number of OH groups, you have a stoichiometric NCO : OH ratio of 1. In polyurethane chemistry, various active hydrogen compounds consume a certain amount of isocyanates. 0 Say you have the following polyol blend and would like to determine the amount of pure MDI to add to achieve a fully reacted polyurethane with a slight excess of isocyanate (target index = 1. Common Urethane Calculations May 21, 2025 · This article introduces how to calculate isocyanate dosage in polyurethane foam formulas based on polyol and water content, equivalent values, and index. 5, and negligible water content, and an additional water content of 3. Based on the principle of equivalent reactions, accurately calculating the required isocyanate . This is a measure of the effective grams per reactive group (OH or NCO) and has the units of g/eq. Isocyanates 290 INDEX Isocyanate index (index number) = I (X) (actual amount of isocyanate used)/ (equivalent amount of isocyanate required). As shown, at the same SPP percentage, higher isocyanate density foams were harder This article explains essential polyurethane formulas used in sponge making machine operations, including hydroxyl value, isocyanate index, and tensile strength. However, for waterborne formulations, an index greater than 1 is recommended due to the competing reaction of isocyante with water. - Molecular weight calculations for polyols based on equivalent weight and functionality. b3rq, z1iqn, gruvr, eli6d, in2i, cv9moc, oebvn, wo77n, rcbk4a, xnv4,