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Articles by Yalcin Copur
Total Records ( 4 ) for Yalcin Copur
  Yalcin Copur
  This study compares the modified kraft process, polysulfide pulping, one of the methods to obtain higher pulp yield, with conventional kraft method. More specifically, the study focuses on the refining effects of polysulfide pulp, which is an area with limited literature. Physical, mechanical and chemical properties of kraft and polysulfide pulps (4% elemental sulfur addition to cooking digester) cooked under the same conditions were studied as regards to their behavior under various PFI refining (0, 3000, 6000, 9000 revs.). Polysulfide (PS) pulping, compared to the kraft method, resulted in higher pulp yield and higher pulp kappa number. Polysulfide also gave pulp having higher tensile and burst index. However, the strength of polysulfide pulp, tear index at a constant tensile index, was found to be 15% lower as compared to the kraft pulp. Refining studies showed that moisture holding ability of chemical pulps mostly depends on the chemical nature of the pulp. Refining effects such as fibrillation and fine content did not have a significant effect on the hygroscopic behavior of chemical pulp.
  Yalcin Copur and Hannu Makkonen
  The aim of this study was to test the measurement precision and accuracy of the Kajaani FS-100 giving attention to possible machine error in the measurements. Fiber length of pine pulps produced using polysulfide, kraft, biokraft and soda methods were determined using both FS-100 and FiberLab automated fiber length analyzers. The measured length values were compared for both methods. The measurement precision and accuracy was tested by replicated measurements using rayon stable fibers. Measurements performed on pulp samples showed typical length distributions for both analyzers. Results obtained from Kajaani FS-100 and FiberLab showed a significant correlation. The shorter length measurement with FiberLab was found to be mainly due to the instrument calibration. The measurement repeatability tested for Kajaani FS-100 indicated that the measurements are precise.
  Mehmet Akgul , Yalcin Copur , Cengiz Guler , Ayhan Tozluoglu and Umit Buyuksari
  The objective of this study was to investigate the suitability of oak (Ouercus robur L.) wood fibers from Turkey as a raw material for medium density fiberboard. In this study, some of the oak wood parts that are especially not suitable for other forest industries was utilized to produce fiberboards in laboratory environment. Test panels of varying densities (0.6, 0.7 and 0.8 g cm-3) were produced at 18 mm thickness using urea-formaldehyde adhesive. Mechanical, water resistance and dimensional stability properties of the test panels were determined according to Turkish standards. The results indicated that laboratory MDF panels produced using oak fibers resulted in mechanical properties that exceed (except panel type A) levels specified in the appropriate existing standards for the general propose fiberboards.
  Cengiz Guler , Yalcin Copur , Mehmet Akgul and Umit Buyuksari
  The aim of this study was to determine some chemical, physical and mechanical properties of juvenile wood from black pine (Pinus nigra Arnold) plantations. Black pine, one of the important softwood species covers the most of the plantations in Turkey. Black pines that naturally grow in Duzce were 20-23 years old with the dimensions of 13-17 cm utilized in this study. Specimens were prepared and tested according to Turkish standards. The physical properties were measured and air and oven dry wood densities were found to be 0.464 and 0.431 g cm–3, respectively. The volume weight was 0.383 g cm–3. The radial, tangential and volumetric shrinkage values were 4.05, 6.19 and 10.24%, respectively. The radial, tangential and volumetric swelling values were also found to be 3.69, 7.79 and 11.5%, respectively. The mechanical tests resulted in that the static bending and compression strengths were 79.1 and 42.4 N mm–2, respectively. In addition juvenile wood had higher lignin and lower holocellulose content compared to the mature wood. Conclusively, the physical and mechanical properties of juvenile pine wood examined in this study were observed to be lower compared to the mature pine wood.
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