Laboratory scale fabrication of unidirectional flax/paper reinforcement

Flax yarn winding machine

By turning the handle of winding machine , one is able to lay down flax yarns adjacent to one another (side by side) to finally end up with a continuous UD flax ply . Distance between yarns is controlled by the number of yarns laid down per inch. To ensure a uniform yarn distribution and consequently repeatable surface density of the UD flax layer, screws with desired number of threads per inch are used at the two ends of winding plate and the threads roots are used to lay down and guide the yarns.

Obviously, the higher the number of yarns per inch and the lower the distance between yarns result in higher surface density reinforcement. Three types of tex 200 UD flax layers used in this study consist of UD flax layers of 16, 20 and 24 yarns per inch, which are fabricated with 1/16″, 1/20″ and 1/24″ pitch screws.

Once the UD flax layer is made, it is wetted and left overnight for drying. This allows fragile polar bonds to develop between the fibers, which ease handling of the layer during fabrication of the hybrid flax/paper reinforcement.

Dynamic sheet former machine

s the manually controlled dynamic sheet former (DSF) machine of Allimand® Company, utilized in this study to fabricate paper sheets. In the figure, the central cylindrical container is where the sheets are made on a plastic forming fabric installed upon a perforated centrifugal drum . In order to develop a paper sheet, first some stock slurry with the desired consistency (usually between 0.1 -1.0 %) is stored in the on board tank at the right hand side of the central container. Then a wall of water is built on the forming fabric by projecting water on it while it is spinning to provide an even distribution of Kraft fiber. Next,  the prepared stock slurry is evenly distributed across the width of the forming fabric through a spraying nozzle moving upward and downward with a constant speed while the drum is still spinning. There is always a minor loss of pulp in the process of paper fabrication with the dynamic sheet former machine. However, since the machine’s parameters have been kept constant at all times (80 rpm for the pump) it is assumed that the portion of pulp loss is constant for all series of paper fabrication. The paper surface densities were measured after fabrication of paper layers , they have small standard deviation signaling consistency of process.

Actually, the dynamic former is devised to simulate the headbox and forming table of the pilot paper machine   using nozzle and forming fabric, respectively. Although the dynamic former is not identical to pilot machine and its parameters differ from those of the pilot machine, an analogy can be made between the two groups of parameters to make them comparable to each other [98]. Moreover, among different laboratory former machines, the dynamic former produces paper sheets having characteristics (such as non-uniformities and anisotropies) comparable to papers made on the pilot paper machines.

Some important parameters of dynamic former which could affect the paper formation quality include the stock volume put in the machine, stock flow rate through the nozzle, water wall thickness, rotational speed of forming fabric, fabric type, dewatering rate, nozzle linear speed as well as nozzle-to-fabric speed ratio which controls the cross direction to machine direction fiber orientation ratio. The specifications of the machine employed in this study are shown in appendix D.

Sheet press 

Three main functions of paper pressing include: dewater the paper, consolidate the fiber web and reduce the surface roughness. After formation in the dynamic former, the wet pressing of paper sheet involves pressing the sheet between press rollers while the sheet is sandwiched between the plastic forming fabric kept underneath and a blotter paper placed on top.

Sheet dryer

the sheet dryer consisting of a heated drum over which the sheet of paper, maintained in place by a plastic fabric, rotates during drying. The dryer is a product of Adirondack Machine Corporation, Formax™ model. This standard dryer is specifically designed to evenly dry pulp and paper products and is equipped with a scaled hand-turning switch allowing for drum temperature adjustment. Another hand turning switch allows adjustment of the drum rotating speed.  A digital thermometer from OMEGA Instruments   using a type K chromium-Aluminum thermocouple is used to manually measure and adjust the drum surface temperature.