Application and interpretation of zero and short-span testing on nanofibre sheet materials

Abstract

Abstract This paper investigates the use of zerospan testing to measure the tensile strength of cellulose nanofibre sheets. The mechanical strength of cellulose nanofibre paper is a key property but tensile strength measurement requires a substantial amount test material, whereas a zero/short span test needs much less material. Sheets made from cellulose nanofibres, microfibrillated cellulose (MFC) and northern bleached softwood fibres were tested at spans ranging from 0 to 0.6 mm and tensile strength spans of 50 and 100 mm. For the cellulose nanofibres or the MFC sheets, strength was constant with span from 0 to 0.6 mm when tested dry and negligible when tested wet, except at zero span. The sheets made from the softwood fibres showed significant strength when tested wet at all spans from 0 to 0.6 mm. The results showed that for nanofibre materials, the zero or short span strength is measuring sheet tensile strength at a smaller sample length. The strength of the nanofibre sheets at 50 or 100 mm was smaller than at zero/short span due to sample size effects and Poisson contraction. The effects of starch and grammage on strength were also studied.