Friction between a surrogate skin (Lorica Soft) and nonwoven fabrics used in hygiene products

Incontinence pad wearers often suffer from sore skin, and a better understanding of friction between pads and skin is needed to inform the development of less damaging materials. This work investigated friction between a skin surrogate (Lorica Soft) and 13 nonwoven fabrics representing those currently used against the skin in commercial pads. All fabrics were found to behave consistently with Amontons' law: coefficients of friction did not differ systematically when measured under two different loads. Although the 13 fabrics varied considerably in composition and structure, their coefficients of friction (static and dynamic) against Lorica Soft were remarkably similar, especially for the ten fabrics comprising just polypropylene (PP) fibres. The coefficients of friction for one PP fabric never differed by more than 15.7% from those of any other, suggesting that the ranges of fibre decitex (2.0–6.5), fabric area density (13–30 g m−2) and bonding area (11%–25%) they exhibited had only limited impact on their friction properties. It is likely that differences were largely attributable to variability in properties between multiple samples of a given fabric. Of the remaining fabrics, the one comprising polyester fibres had significantly higher coefficients of friction than the highest friction PP fabric (p < 0.005), while the one comprising PP fibres with a polyethylene sheath had significantly lower coefficients of friction than the lowest friction PP fabric (p < 10−8). However, fabrics differed in too many other ways to confidently attribute these differences in friction properties just to the choice of base polymer

An experimental study of friction between wet and dry human skin and nonwoven fabrics

Many people who have urinary incontinence manage it with the use of absorbent hygiene products, such as pads. Long-term use of these products can lead to abrasion by friction between the topsheet (a nonwoven fabric) and the skin, and is exacerbated when the skin is wet. However, the nature and mechanisms of friction between skin and nonwovens are poorly understood, hindering progress to improve products. Most work on skin friction to date has involved the use of skin surrogates or real skin in the dry state only. Moreover, only a narrow range of different nonwoven fabrics have been investigated. The work described in this thesis aimed to improve understanding of friction between nonwoven fabrics and human skin, and was divided into four main blocks. In the first, friction was measured between a skin surrogate (Lorica Soft) and 13 different nonwoven fabrics, varying in structure, fibre material and manufacturing techniques. Amontons’ law was closely obeyed for all nonwovens (that is, coefficients of friction were independent of normal force) and the data were used to select a representative subset of five nonwovens for subsequent work. In the second block of work, an in vivo study of friction was conducted between the subset of (five) nonwovens and the dry volar forearm skin of 19 female volunteers (aged 20-95 years). It was found that Amontons’ law also held for all of these measurements, despite the general viscoelastic nature of human skin, the range of skin types (from smooth and firm to wrinkled and flaccid) and the difference in ages. The coefficient of friction for a given fabric varied considerably between participants (an increase of up to 101% of the lowest coefficient value), but the fabrics were generally ranked in the same order for all volunteers. The third block of work involved the measurement of wet friction between the subset of five nonwovens and volar forearm skin of five of the study participants. In general, the coefficient of friction increased with skin wetness/hydration by up to a factor of thirteen until the skin was damp/moist. The relationship for very wet skin (with surface water) – thought to be lubricated – was unclear and varied between participants and between nonwovens. However, further work would be required to locate and quantify the excess water in and on the skin, in order to more accurately evaluate the contribution of water to friction. Finally, in the fourth block of work, the fibre footprints of nonwovens against a surrogate skin surface (glass microscope slide) were examined, providing insight into how friction is mediated by the interface. Total fibre contact length was always extremely low (typically 0.3-1.6 mm · mm-2) and increased linearly with the log of pressure, usually due to an increase in the number of contacts and sometimes because of an increase in the lengths of existing fibre contacts

The Impact of Microclimate on Skin Health With Absorbent Incontinence Product Use An Integrative Review

This integrative review considers the role of skin occlusion and microclimate in incontinence-associated dermatitis (IAD), with a particular focus on disposable, body-worn, absorbent incontinence products. Although the mechanisms are not fully understood, the primary causes of IAD are well-established: occluded skin, in prolonged contact with urine and/or feces and exposed to abrasive forces, is more likely to be affected, and each of these factors can be influenced by wearing absorbent incontinence products. Studies comparing the effect of various absorbent products on skin health have been hindered by the many differences between compared products, making it difficult to clearly attribute any differences in performance to particular materials or design features. Nevertheless, the large and significant differences that have sometimes been found invite further work. Breathable back sheets can significantly reduce the temperature of occluded skin and the humidity of the adjacent air, and several treatments for nonwoven top sheet materials (used next to the skin) have been shown to impart antimicrobial properties in the laboratory, but an impact on IAD incidence or severity has yet to be demonstrated directly. Recent work to introduce sensing technology into absorbent incontinence products to reduce the exposure of skin to urine and feces, by encouraging prompt product changing, seems likely to yield measurable benefits in terms of reducing incidents of IAD as the technology develops. Published work to date suggests that there is considerable potential for products to be engineered to play a significant role in the reduction of IAD among users