ISO 16365-3:2014

Overview

ISO 16365-3:2014 - Plastics - Thermoplastic polyurethanes (TPU) for moulding and extrusion - Part 3 - specifies a practical laboratory method to distinguish ether and ester thermoplastic polyurethanes by determining the ester group content. The standard provides an alkaline hydrolysis and titration procedure that requires no sophisticated instrumentation and is applicable to all linear polyurethanes based on 4,4′-diphenylmethane diisocyanate (MDI). It is designed for routine quality control, characterization of TPU mixtures, and to minimize long-term microbial- or hydrolysis-resistance testing.

Key topics and technical requirements

• Principle: Alkaline hydrolysis of TPU in dimethylsulfoxide (DMSO) followed by titrimetric determination of hydrolysable groups. Ester content is obtained by subtracting urethane-derived acid value from the total hydrolysable acid value (E = total hydrolysable − hydrolysable urethanes).
• Reagents and conditions: Uses analytical-grade reagents including DMSO, methanol, 0.5 mol/L KOH (in methanol), 0.5 mol/L H2SO4 (aqueous) and phenolphthalein indicator. Specified sample size (0.5 g), reflux hydrolysis for about 5 hours, and blank determinations are required.
• Apparatus: Standard laboratory glassware and equipment (centrifugal mill, Soxhlet for extraction of phosphorous plasticizers, reflux cooler, automatic burette or titrator).
• Sample preparation: Powdering to ~2 mm; optional Soxhlet extraction for samples containing phosphorous plasticizers (which can raise apparent ester content).
• Calculation and reporting: Results expressed as mg KOH/g (ester content and acid values). Reports must reference ISO 16365-3 and include method details (indicator vs potentiometric titration), material identification and test date.

Practical applications

• Rapidly classify TPU as ether- or ester-based for formulation control and supply-chain verification.
• Screening tool to reduce or avoid lengthy microbial-resistance and hydrolysis testing when assessing material suitability for end-use environments.
• Characterization of TPU blends and recyclates where ester/ether composition affects hydrolytic stability, processing and end‑use performance.
• Routine QC in manufacturing, incoming inspection, and product development labs.

Who should use this standard

• TPU manufacturers and compounders
• Polymer testing and quality-control laboratories
• Materials scientists and R&D teams working on TPU formulations
• Procurement and compliance professionals needing assurance of TPU type

Related standards

• ISO 16365-1 (designation system and specifications) and ISO 16365-2 (test specimen preparation and property determination)
• ISO 3696 (water for analytical laboratory use)
• Other referenced glassware and titration standards noted in the ISO document

Keywords: ISO 16365-3:2014, thermoplastic polyurethanes, TPU, ester content, ether TPU, ester TPU, MDI, alkaline hydrolysis, titration, quality control, hydrolysis resistance.