Raw jute of Bangladesh white B grade was collected from Bangladesh Jute Research Institute. All chemicals used were of reagent grade provided by Menonite Central Committee, Dhaka. Four sets of experiments were performed using Rosin and alum as internal additives, MCC as external additive and raw jute as fiber reinforcement to find the optimum additives for enhanced hydrophobicity and strength.
2.1 Fiber Sample Preparation: The collected jute fibers were cleaned carefully and cut into small pieces of 1.27 cm -2.54 cm (0.5 -1 inch) size.
2.2 Pulp Preparation: 2.2.1Boiling and beating: The raw fibers were boiled in alkaline solution to remove impurities soluble in mild alkalis at moderately high temperature as well as to soften and condition the fiber. 300 gms of the fiber samples were boiled in NaOH (18g) solution in water (10 liter). The water level was constantly maintained at 10 liters and the boiling process was continued for 4 hours. The boiled fibers were washed with water until the fiber stock was clean enough with minimum fiber loss. The washed jute fibers were beaten in an open vessel of beater in 70 kg of fresh water for 2.25 to 2.5 hours. The resulting pulp was kept standing for 17.25 hoursand washed to neutral pH.
2.2.2 Internal Sizing: 500gm of rosin powder was dissolved in hot caustic solution (50gm NaOH in 1l water) and the solution was boiled for 30 mins. 4.5gm Rosin solution (1.5% of weight of washed pulp sample) was further diluted with hot water before application to pulp. The rosin solution was applied to the pulp and stirred for 5 mins then rested for 30 mins followed by application of 3% alum solution with 5 mins stirring. For another set of experiment the rosin solution was applied with 5 minute stirring, then the pulp was rested for 30 mins. 0.75% emulsion was introduced to the pulp and stirred for 5 mins followed by application of 3% alum solution with 5 minsstirring.
The pulp was rested for 20 mins after internal sizing application. For easy liquid drainage the pulp was kept on a net and washed thoroughly to achieve neutral pH. The pH of the pulp showing the degree of acidity or alkalinity was measured by standard pH paper.
2.2.3 Lifting: 1 litre of 0.05% polyimide solution mixed with 20 litre of water in a lifting vat. The Pulp was suspended uniformly in the water of the lifting vat and lifted in sheet form from the lifting vat and kept on a bed table using cloth separators.
2.3 Fiber Reinforcement: Jute fiber filaments from carded sliver of BTB jute were used as reinforcement between two layers of pulp manually keeping a distance of 2.54 cm between fibers (both vertically and horizontally).
2.4 Sheet formation and drying: Hydraulic press of 10 ton capacity was used to press the pulps in lap form for 15 minutes to produce paper sheet. These sheets were sundried followed by calendaring.
2.5 External sizing: Paper sheets were soaked in 0.5% MCC suspension for 1 minute, then dried in sunlight. Another batch of paper sheets were soaked in 0.5% wax emulsion for 1 minute and dried in sunlight.
2.6 Characterization: The physical properties of paper were measured for each experimental group as per TAPPI standard test methods. For each property representative samples were taken from all the samples. The following physical properties were tested. 2.6.1 Thickness: The thickness of the paper sheets was measured by venire calipers according to TAPPI T441om-97 method. 10 samples (10cm x 10cm) for each experiment were taken and five readings from each sample were recorded in mm. 2.6.2 GSM: The weight of the samples were taken by electronic balance and converted to Grams per Square Meter (GSM).
2.6.3 Cobb Water Absorptivity: Three representative samples (12.5cm x 12.5cm) from each experiment were used to test the water absorptivity according to TAPPI T 441om-98 method. The samples were weighed to the nearest 0.01g. A dry rubber mot was placed on the metal plates then the sample was placed on it and the metal ring was placed on the sample and fastened firmly in place with crossbar to prevent leakage. 100 ml water of room temperature was poured into the ring as rapidly as possible creating a head of 1.0 x 0.1cm. The water was quickly removed from the ring after 110seconds. The crossbar and the metal ring were removed carefully and quickly and the sample was placed with its wetted area for the predetermined test period (2 minutes), a sheet of blotting paper was rolled back and forward forth once over the pad without exerting any additional force on the roller. The sample was folder with the wetted area in side and was re-weighted immediately and the absorbed water was calculated by the following formula,
Weight of water absorbed (Gm/m2 )= {Final wt. (g)- Conditioned wt (g)} x 100
Water Absorption Index= W1/GSM
Where W= Weight of water absorbed in GM/ M2, GSM= Weight paper in Gm/M2.