Introduction In this study, an investigation was carried out of the absorbent properties and the dynamics of molecular motion in the principal constituents of disposable in- continence pads. Urinary incontinence affects approximately 5% of adults in the western world [1]. Much incontinence can be cured by drug therapy, surgery, or physiotherapy but these treatments are not effective for a significant mi- nority of sufferers. For them it is important to minimise the impact urine leakage has on their quality of life, and this usually involves the use of disposable absorbent pads. Until 15 years ago, the majority of incontinence products were of very simple design, often comprising little more than a core of fluffed wood pulp fibres, contained between a water-permeable coverstock next to the body, and a polyethylene waterproof backing [2]. More recently designs have increased in sophistication, drawing on technology developed for the baby diaper market. For example, most products now include Gaby S. Pell Mark A. Landeryou Alan M. Cottenden Roger J. Ordidge NMR investigation of the nature of water in disposable incontinence pads containing superabsorbent polymers and fluffed wood pulp Received: 2 August 2002 Accepted: 31 January 2003 Published online: 20 March 2003 Ó Springer-Verlag 2003 Abstract The use of nuclear mag- netic resonance to make quantitative measurements of the absorption processes occurring in the constitu- ent materials of disposable inconti- nence pads was investigated. Modern incontinence pads often have a layered structure with the absorbent layer principally consist- ing of superabsorbent polymer (SAP) grains distributed in fluffed wood pulp. T 2 -weighted and mag- netisation transfer contrast (MTC) measurements were made using samples of SAP, fluffed wood pulp, and a mixture of 50% SAP and 50% fluffed wood pulp following the ad- dition of water and NaCl solutions. The T 2 -weighted signal always de- creased on mixing the liquid and material samples, with SAP showing the smallest magnitude of signal de- cline. The MTC change was minimal for SAP, but increased for the other samples. The small changes in the T 2 -weighted signals and the MTC observed when adding water to SAP indicate that water is not principally being tightly bound by the polymer. The absorption time-course was further evaluated by acquiring pro- ton-density-weighted 1D profiles af- ter the addition of water to the samples. In SAP, the fitted time constant was comparable to the ac- tivation energy measured by other methods. The relaxation times both declined on mixing the liquids with samples of SAP and fluffed wood pulp. The reduction in spin–spin re- laxation is sufficient to account for the T 2 -weighted signal changes. Keywords Superabsorbent polymer Æ Magnetic resonance imaging Æ Nuclear magnetic resonance Æ Fluffed wood pulp Æ Incontinence Colloid Polym Sci (2003) 281: 1127–1135 DOI 10.1007/s00396-003-0887-0 ORIGINAL CONTRIBUTION G.S. Pell Æ M.A. Landeryou (&) A.M. Cottenden Æ R.J. Ordidge Department of Medical Physics and Bioengineering, University College London, 1st Floor Shropshire House, 11–20 Capper Street, London, WC1E 6JA, UK E-mail: m.landeryou@medphys.ucl.ac.uk Tel.: +44-171-2096262 Fax: +171-2096269