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 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Relationships Between the Changed Apparent Density of Recycled Handsheets and Their Mechanical and Physical Properties) ผู้เขียน: ดร.สมหวัง ขันตยานุวงศ์, รองศาสตราจารย์ ,  Supharp Keawmanee, Alisa Chusri สื่อสิ่งพิมพ์:pdf AbstractRelationships between the changed apparent density of recycled handsheets and their mechanical and physical properties were demonstrated. Recycled handsheets with decreased apparent density possessed decreased mechanical properties such as folding endurance, modulus of elasticity, and tensile strength. Changes in the brightness and opacity of recycled handsheets were consistent with the effect of the changed apparent density of paper on its brightness and opacity due to beating and wet pressing. This was possibly because the decreased apparent density meant there were lots of air voids in the handsheet structure due to the loss in conformability and flexibility of less-swollen-recycled fibers as well as the lost mass of handsheets during recycling. The loss in swelling capability of wet fibers with recycling could be determined by light microscopy and the WRVs of the fibers. In this study, it seemed that handsheets produced from softwood bleached kraft pulp fibers could considerably retain some of their mechanical properties and opacity with good brightness when recycling not more than twice without additional chemical and mechanical treatments. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Water Absorptiveness of Handsheets Produced with Various pH Levels of Pulp Suspension, AKD Dosages and Mixing Times) ผู้เขียน:ดร.สมหวัง ขันตยานุวงศ์, รองศาสตราจารย์, Atipong Wattanayingyongkul, Weerapol Mingkwan สื่อสิ่งพิมพ์:pdf AbstractThe objectives of this study were to determine the effects of high pH levels of pulp suspension and high dosages of alkyl ketene dimers (AKD) on the water absorptiveness of handsheets. Various mixing times were applied for the pulp suspension-AKD mixing conditions and analyzed for their effects. Handsheets were produced with various pH levels (pH 8, 9 and 10) of pulp suspension, AKD dosages (0.25, 0.50, 0.75 and 1.00% oven-dry weight (o.d.wt.) of pulp fiber) and mixing times (1, 5 and 10 min). The results indicated that the water absorptiveness of handsheets produced with 0.25% o.d.wt. of pulp fiber of AKD at any pH level of pulp suspension or prepared with any dosage of AKD in the pulp suspension at pH 8 was lower with a mixing time of 5 min, while that of handsheets produced with 0.50% to 1.00 % (o.d.wt. of pulp fiber) of AKD in the pulp suspension at pH 9 and 10 was higher with a mixing time of 5 min. This was possibly because the higher dosages of AKD could ensure sufficient AKD-oligomers were retained in the handsheets to promote good sizing, while the number of ?-keto ester bonds established between the AKD and the surfaces of pulp fibers and fines was insufficient after a short mixing time of 1 min. Although some AKD could also be hydrolyzed with a long mixing time of 10 min, the excess amount of AKD could still react with the surfaces of pulp fibers and fines with ?-keto ester bonds and the remaining AKD would also be retained in the handsheets as oligomers to promote good sizing. In addition, the stronger basic conditions would favor the formation of ester bonds. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Effects of the Various Mixing Ratios of Recycled Pulp on the Physical and Optical Properties of Handsheets and their Curl due to Laser Printing) ผู้เขียน:ดร.สมหวัง ขันตยานุวงศ์, รองศาสตราจารย์, Phornwilai Nithisoonthornphong, Warakorn Thunyakhunakornsakool, ดร.สาวิตรี พิสุทธิ์พิเชฎฐ์, ผู้ช่วยศาสตราจารย์ สื่อสิ่งพิมพ์:pdf AbstractThe objectives of this study were to determine the physical and optical properties of handsheets and also to ascertain the behavioral phenomena of their curl due to laser printing. Handsheets were separately produced from beaten hardwood, softwood and recycled pulp and also from various mixing ratios of the beaten pulp. The recycled pulp was derived from white wood-free shavings (WWFSs) and washed-WWFSs pulp slurries. The results demonstrated that hardwood and softwood pulp mixed with washed-WWFSs recycled pulp could produce higher apparent density handsheets than those mixed with WWFSs recycled pulp, even though the increased amount of WWFSs and washed-WWFSs recycled pulp used for making handsheets decreased the apparent density and tensile strength of handsheets. Most of the various ratios of WWFSs recycled pulp mixed with hardwood and softwood pulp could give slightly higher brightness and opacity handsheets than most of those of washed-WWFSs recycled pulp mixed with the same hardwood and softwood pulp. With laser printing, handsheets printed on their bottom side were curlier than those printed on their top side. This is possibly because a greater amount of inorganic materials, which was demonstrated in terms of ash content, derived from fillers and coating pigments were retained in the top side of the handsheets. The increase in ash content of handsheets also decreased the amount of curl. In this study, it is especially noteworthy to demonstrate that without any inorganic materials retained in handsheets, both the handsheets printed on the top and the bottom side had the same amount of curl. |
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