PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 5, Number 2, 2019
WOOD PANEL Gypsum-Based Boards Made from Mixtures of Waste Cellulosic Sources: Part 1. Physical and Mechanical Properties, Halil Şahin & İlkhan Demir , European Journal of Science and Technology , Issue 16, 2019, pp.567-576. It was realized that post- consumer waste paper, old corrugated container (OCC) and secondary fiber addition (cellulosic additives) to gypsum in panel structure negative impact on Thickness Swelling (TS) values in water. However, highest TS values of 23.32% (A6) in A-type, 12.76 (B6) in B-type and 7.79% (C6) in C-type experimental boards found at similar proportions (50:50 w/w) of gypsum and cellulosic additives while the lowest with control sample that was only 1.88%. Moreover, the boards produced by secondary fiber/gypsum mixture (C type boards) under similar ratios (w/w) were found to higher IB strength than others. The highest IB strength value of 0.60 N/mm 2 found for C3 board while the ratio of the secondary fiber in the mixture to be more than 20% negative effects on IB values to a certain extent. The addition of all three cellulosic sources to the gypsum structure increases the bending strength properties some level. At 10% (A2: 6.59 N/mm 2 ) and 50% (A6: 6.44 N/mm 2 ) proportion levels, A-type boards show higher bending strengths than the B- and C-type boards. In all manufacturing conditions and board types, the natural weathered boards have always shown lower hardness properties than counterpart control samples. Thermomechanical surface instability at the origin of surface fissure patterns on heated circular MDF samples, Andrea Ferrantelli et al, Fire & Materials , 43 (6), pp.707-716 . When a flat sample of medium density fibreboard (MDF) is exposed to radiant heat in an inert atmosphere, primary crack patterns suddenly start to appear over the entire surface before pyrolysis and any charring occurs. Contrary to common belief that crack formation is due to drying and shrinkage, it was demonstrated for square samples that this results from thermomechanical instability. In the present paper, new experimental data are presented for circular samples of the same MDF material. The sample was exposed to radiant heating at 20 or 50 kW/m 2 , and completely different crack patterns with independent eigenmodes were observed at the two heat fluxes. We show that the two patterns can be reproduced with a full 3 Ǧ D thermomechanical surface instability model of a hot layer adhered to an elastic colder foundation in an axisymmetric domain. Analytical and numerical solutions of a simplified 2 Ǧ D formulation of the same problem provide excellent qualitative agreement between observed and calculated patterns. Previous data for square samples, together with the results reported in the present paper for circular samples, confirm the validity of the model for qualitative predictions and indicate that further refinements can be made to improve its quantitative predictive capability. Tailoring of oxidized starch's adhesion using crosslinker and adhesion promotor for the recycling of fiberboards, Muhammad Adly Rahandi Lubis et al, Journal of Applied Polymer Scienc e, 136 (38), article 47966. The growing interest in recycling waste medium density fiberboards (MDFs) is driving the development of new adhesives that provide sufficient adhesion, and allow disintegration of the waste MDFs. Described in here is the preparation of adhesives based on oxidized starch (OS) in combination with blocked Ǧ polymeric 4 Ǧ 4 diphenylmethane diisocyanate (B Ǧ pMDI) as a crosslinker and poly(vinyl alcohol) (PVA) as an adhesion promotor for the recycling of waste MDFs. The – COOH groups of OS were reacted with – NCO groups of B Ǧ pMDI to form amide linkages, and the – CHO groups were reacted with – OH groups of PVA through hydrogen bonding. Further, when applied as an adhesive, the OS formed ester linkages with – OH of MDF fibers. As the results, MDF bonded with 1% B Ǧ pMDI/15% PVA/OS adhesive had an internal bonding strength of 0.13 MPa, 0.01 mg L − 1 of formaldehyde emission (FE), and
Technical Abstracts
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