Flat-pressed composites using linear low-density polyethylene (LLDPE) and rapeseed waste were made by hot pressing. This study investigated the effects of filler loading on the flexural and physical properties of rapeseed-filled thermoplastic polymer composite panels. The modulus of elasticity and flexural strength were mainly influenced by the filler content. The flexural strength was shown to decrease significantly with an increase in the filler content, while the flexural modulus increased insignificantly. With the increase of the filler content, the water absorption and the thickness swelling were increased significantly due to the strong hydrophilicity of lignocellulosic filler. Water absorption was proved to follow the kinetics of a Fickian diffusion process. The swelling model presented by Shi and Gardner [(2006). Hygroscopic Thickness Swelling Rate of Compression Molded Wood Fiberboard and Wood Fiber/polymer Composites, Composite Part A Applied Science and Manufacturing, 37(9): 1276-1285] provided a very good prediction of the hygroscopic swelling process of rapeseed/LLDPE composite panels.
Iran is facing a severe lack of fibrous raw materials for paper production. Kenaf (Hibiscus cannubinus L.) is a superior complement to wood as a source of fiber. Kenaf bast fibers are excellent for making pulp and paper of various grades due to the presence of high alpha cellulose (56.43), holocellulose (77.71), and ultimate fiber length (2.77 mm). Fiber length is an important factor in the development of tear and tensile properties. The aim of this work is to study the effect of charge alkali (20 and 25% oven dried, as NaOH) and cooking time (30, 60, 90, 120, 150, and 180 min) of kenaf bast fiber on soda and soda-anthraquinone (AQ) pulp yield, kappa number, rejects, and strength properties of their handsheets. Results indicated that alkali charge and cooking time had significant influence on kappa number, yield, and rejects of pulps, whereas PFI revolution had only a minimal effect, especially at higher cooking times. The soda method was modified by adding 0.2% anthraquinone, and the resultant pulps displayed an increase in pulp yield and reduction in both kappa number (by 6 to 9 units) and screening rejects. The strength properties obtained with the two cooking processes used were compared, and those provided by soda-AQ process were found to be best. Regarding handsheet properties, a significant improvement in tensile index could be obtained by the soda-AQ process, compared to the soda process.
Fiber dimensions, chemical composition, and soda and soda-AQ pulping of tobacco stalks were examined to assess if they were suitable for pulp and paper production. The results showed that the morphological characteristics of tobacco stalks were similar to those of nonwoods and hardwoods. The average values of length, diameter, and cell wall thickness of tobacco stalks fibers were determined as 1.23 mm, 24.31 μm, and 8.93 μm, respectively. The holocellulose and alpha-cellulose in tobacco stalks were lower than those of hardwoods and common nonwoods. In addition, lignin content of tobacco stalks was lower than that of hardwood. The holocelluloses, alpha-cellulose, lignin, and ash contents of tobacco stalks were examined to be 67.79, 39.20, 18.90, and 6.86 wt%, respectively. The optimum cooking conditions for a bleachable pulp of tobacco stalks were found to be as follows: active alkali 25%, temperature 165°C, cooking time 180 min, and 0.2% anthraquinone. Addition of anthraquinone resulted in lower screening rejects and lower kappa number, higher screen yield, and higher brightness. The bleaching of tobacco stalk pulp did not respond very well. The brightness of pulp made by tobacco stalks reached about 73.06% on DED and 78.2% on DEDD bleaching sequences.
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