A method for preparing extensible paper on the laboratory scale

Abstract Extensibility is an important property for papers undergoing large deformations in converting or end use application (e.g. industrial bags). Industrially, high extensibility is created by compacting the moist paper web in machine direction (MD) using an extensible unit such as the Clupak or Expanda methods. In this study, a method was developed to produce extensible paper on the laboratory scale. The Clupak unit was simulated using a purpose-built MD compaction apparatus. A paper sheet is placed between two stretched rubbers which are recoiled under perpendicular pressure to create sufficient friction between paper and rubber. The laboratory method for producing extensible paper sufficiently corresponds to the industrial process, i.e. strain increased while tensile stiffness index and tensile index decreased. Increased solids content during rubber recoiling enhanced the sigmoidal shape of the specific stress versus strain curves whereas tensile index remained unchanged. The reproducibility of the method is at a good level and thus the developed method offers a feasible way to study the production of extensible paper on the laboratory scale.