A method for preparing extensible paper on the laboratory scale

Extensibilityisan important propertyfor papers undergoing large deformations in converting or end use application (e.g. industrial bags). Industrially, high extensibility iscreated by compactingthe moist paper webin machine direction (MD) using anextensible unitsuchas the Clupak or Expanda methods.In this study, amethod was developed to produceextensible paperon thelaboratoryscale. The Clupakunit was simulated using a purpose-builtMDcompactionapparatus. Apaper sheetis placedbetween two stretched rubbers which arerecoiledunder perpendicular pressure to createsufficientfriction between paper and rubber.The laboratory methodfor producing extensible papersufficiently corresponds tothe industrial process, i.e. strain increased while tensile stiffness index and tensile indexdecreased.Increased solids content during rubber recoilingenhancedthe sigmoidal shape of thespecific stress versus strain curves whereas tensile index remained unchanged. Thereproducibility of the methodisat agood leveland thusthe developed method offers a feasible way to study the production of extensible paper on thelaboratoryscale