The use of different mineral material types and contents in medium density fiberboard (MDF) production was investigated. Three different minerals (sepiolite, dolomite, and perlite) and five different ...ratios (3%, 6%, 9%, 12%, and 15%) were used according to the oven-dry wood fiber weight. These minerals were homogeneously added as powder between the wood fibers. Some physical, mechanical, limit oxygen index (LOI), and thermogravimetric analysis (TGA) tests of the boards were conducted. The mineral fillers negatively affected the physical properties such as water absorption (WA), thickness swelling (ThS), and mechanical properties such as modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB). However, LOI and TGA test results showed a positive effect on combustion resistance depending on the type and rate of mineral fillers.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In this study, it is aimed to produce wood plastic composite material with eggshell additives and to investigate the mechanical properties of these materials. Mechanical properties such as tensile ...strength and modulus of elasticity, elongation at break, flexural strength and modulus of elasticity and impact resistance of new materials produced by adding eggshell to wood plastic composite at different rates were investigated. It was determined that tensile strength values gradually decreased due to the increase in the amount of eggshell in the composites produced. The modulus of elasticity of the composite material in tensile strength increases with the increase in the amount of eggshell in the mixture. With the increase of the eggshell ratio used, the elongation values of the plastic composite at break are reduced. The eggshell material used in wood plastic composite reduces the bending strength of the material. The eggshell reduces the modulus of elasticity of the composite material in bending. The eggshell composite material did not cause a significant change in impact resistance.
This study focused on the potential use of hazelnut husk (HH) flour, agricultural by-product, as filler in the PLA biocomposite films. The tensile strength and elongation at break of the ...biocomposites films decreased with the increasing content of the HH flour. As the amount of the HH flour in the PLA was increased by 10 wt%, the tensile strength decreased from 33 to 26.3 MPa. A sharp decrease in the tensile strength (6.33 MPa) of the specimens was determined as the amount of the HH flour was increased by 20 wt%. There was no significant difference in the tensile strength as the HH content increased from 20 to 40 wt%. The main reason for the lower tensile strength was mainly attributed to them due to the weak interfacial bond between HH flour with higher polar surface and the PLA with lower polar surface. The hydrophilic nature of the HH leads to a tendency for HH fibers to mingle or form agglomerations, which resulted in the lower tensile strength, especially at high HH filler loadings. The increase in the filler content improved the thermal stability of biocomposites.
The assessment of self-regulation, which is important for the geometry learning area and can be associated with the stages of the ACE cycle, is important for success. The study was conducted to ...determine the effect of the ACE cycle-based learning process on students’ geometry self-efficacy beliefs in the 7th grade polygons learning area. Quasi-experimental design with pretest-posttest control group, one of the quantitative research methods, was preferred in the study. The study group consisted of a total of 46 students, 24 in the control group and 22 in the experimental group, studying in the seventh grade of a middle school in the eastern Anatolia region of Turkey. In the 4-week implementation, the lessons were conducted according to the ACE learning cycle in the experimental group, while no intervention was made in the control group. In this study, the Self-Efficacy Scale for Geometry was used as a data collection tool and independent sample t-test and dependent sample t-test were used to analyze the data. The results showed that the instruction shaped according to the ACE learning cycle was more effective on students' geometry self-efficacy beliefs in the related learning domain.
This study investigated the tensile properties and thermal behavior of virgin and hot press molded HDPE composites filled with different particle size and content of used beverage cartons which were ...the Tetra Pak® cartons. The mechanical properties of the composites were positively influenced by particle size of the used beverage carton, such that the smallest particle size gave the highest tensile strength and tensile modulus. The tensile strength of the specimens decreased with increasing filler content (40 to 70 wt%), while the tensile modulus rose. Furthermore, the filler size and its content affected the thermal behavior of the specimens. Calorimetry analysis of composite specimens showed that melting temperature and enthalpy values of virgin HDPE and recycled-HDPE decreased with increasing Tetra Pak® content. In all composite groups produced by adding Tetra Pak®, the degree of crystallinity decreased as a function of Tetra Pak® addition compared to the pure HDPE. Increasing particle size adversely affected the crystallization degree, which decreased with increasing particle size while the HDPE maintained its crystalline form. As for the recycled-HDPE composites, the degree of crystallization was reduced by increasing the Tetra Pak® content, but this was still noticeably higher than that of the HDPE.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The technological, thermal, and antimicrobial properties of biocomposite films produced from polylactic acid (PLA) and thermally treated wood flour with in situ generated nanosilver particles (AgNPs) ...using a bio-reduction method. The extracts of fresh leaves of the phenolic-rich Oriental sweetgum (
Liquidambar orientalis)
tree were used as the reducing agent for silver ions. Six different formulations of the mixed raw materials were extruded in the co-rotating twin screw extruder. The PLA bicomposite films at the 5 and 10 wt% loading levels of wood flour were produced by a hot press method from the following six formulations: (a) thermally treated wood + leaf extract + AgNO
3
, (b) untreated wood + leaf extract + AgNO
3
, (c) thermally treated wood + AgNO
3
, (d) untreated wood + AgNO
3
, (e) thermally treated wood, (f) untreated wood, and (g) neat PLA. All biocomposite films produced with the untreated/treated wood flour at 5 and 10 wt% loading levels of wood flour showed better tensile modulus than the neat PLA specimens. In general, the tensile strength of the biocomposites was negatively affected by the increased content of the wood flour. The spectra obtained from scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) showed the silver nanoparticles in the wood particles. The results showed that the biocomposite films produced with PLA and wood flour modified using silver nitrate and leaf extract had the highest tensile modulus. It was observed that the leaf extract treatment had a positive effect on the tensile properties of the biocomposite films at 10 wt% content of wood flour. The remarkable antimicrobial results was obtained by the prepared biocomposites treated with gram positive and gram negative clinical pathogens at maximum zone of clearance 2.6 mm treated with
E.
coli
bacteria.
Next-generation laminated wood composites were produced using waste poplar (Populus deltoides) veneer and polyvinyl acetate adhesive. Four experimental groups and one control group were created. ...Ten-layer laminated wood veneer samples were reinforced with natural rubber (Group A), linoleum (Group B), felt (Group C), and elastomeric sponge (Group D); these materials were used in the fifth adhesive layer (middle layer). The sound absorption coefficients of the control and experimental groups were tested via the impedance tube method, according to ASTM standard E1050 (2006). Attention was paid to the acoustic behavior at low frequencies (63 Hz to 250 Hz), mid frequencies (250 Hz to 2000 Hz), and high frequencies (2000 Hz to 6300 Hz). It was determined that the sound absorption coefficient of the experimental groups considerably increased. It can be suggested that the experimental groups be used as sound absorbing acoustic panels and the control group as sound reflective acoustic panels.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The fire properties of particleboard coated with calcite and a variety of fire-retardants (FR) was investigated. Four different chemicals, boric acid (BA), borax (BX), dolomite (DOL), and melamine ...(MEL), were added at the concentration of 1.0%, 3.0%, and 5.0% by oven-dry weight of calcite. The particleboard panels were tested according to the ASTM-E 69 standard to investigate their fire-retardant properties. The determination of weight loss, temperature, and the release of O2, CO, and NO by the samples was measured and recorded over 30 s intervals during combustion of the materials. The results indicated that the BA coatings exhibited better thermal stability than the other chemicals. Consequently, the lowest weight loss and temperature was found for specimens treated with 5.0% BA. These chemicals were effective relative to the fire properties of coated particleboard surfaces, depending on the type and ratio of the chemicals to the calcite.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Long-term hygroscopic thickness swelling rate of polypropylene (PP) composites filled with thermally treated wood flour was investigated. The beech wood chips were heat treated at 120 °C, 150 °C or ...180 °C for 30 or 120 min using saturated steam in a digester. The composites based on PP, beech wood flour (BF), and coupling agents (PP-g-MA) were made by melt compounding and injection molding. The weight ratio of BF to PP was controlled at 50/47 for all blends. The amount of coupling agent was fixed at 3 wt.% for all formulations. Further study was conducted to model thickness swelling of the composites, a swelling rate parameter (KSR). The thickness swelling of thermally-treated samples at 120 ºC for 30 min and at 150 ºC for 30 min were lower than that of control samples, followed by thermally-treated samples at 180 ºC for 120 min, at 180 ºC for 30 min, at 120 ºC for 120 min, and at 150 ºC for 120 min, respectively. Furthermore, the thickness swelling of the BF/PP composites decreased with increasing time and temperature of the thermal-treatment. In addition, at 120 ºC for 30 min, the composites showed a lower swelling rate than control samples. The KSR of the composites was influenced both by the time and temperature of thermal treatment.
U radu je istražen dugotrajni stupanj higroskopskoga debljinskog bubrenja polipropilenskih (PP) kompozita punjenih toplinski obrađenim drvnim brašnom. Iverje od bukovine bilo je toplinski tretirano na 120, 150 ili 180 °C tijekom 30 ili 120 minuta uz pomoć zasićene pare u digestoru. Kompoziti na bazi PP-a, brašna od bukovine (BF)-a i veziva (PP-g-MA) izrađeni su taljenjem i injekcijskim prešanjem. Maseni je omjer BF/PP za sve smjese bio 50/47. Količina veziva za sve formulacije bila je na 3 wt.%. Nadalje, provedeno je modeliranje debljinskog bubrenja kompozita i parametra brzine bubrenja (KSR). Debljinsko bubrenje uzoraka toplinski tretiranih 30 min na 120 ºC i 30 min na 150 ºC bilo je niže nego na kontrolnim uzorcima, zatim slijede uzorci toplinski tretirani 120 min na 180 ºC, 30 min na 180 ºC, 120 min na 120 ºC, odnosno 120 min na 150 ºC. Nadalje, debljinsko bubrenje BF/PP kompozita smanjivalo se s povećanjem vremena i temperature toplinskog postupka. Osim toga, kompoziti su pri 30 min na 120 ºC pokazali niži parametar brzine bubrenja od kontrolnih uzoraka. Na parametar brzine bubrenja kompozita utjecali su vrijeme toplinskog tretmana i temperatura.
ABSTRACT Water resistance, mechanical properties, and limiting oxygen index (LOI) of wood plastic composites (WPCs) and neat polypropylene filled with different amounts (3, 6, and 9% by weight) of ...dolomite powder and wood flour (15 and 30 by weight) were investigated. Wood flour, dolomite powder, polypropylene, and wax were dry-mixed in a high-intensity mixer to produce a homogeneous blend. This blend was then compounded in a laboratory-scale single screw extruder. Test specimens were produced by injection moulding process from the pellets dried to moisture content of 1%. The thickness swelling and water absorption of the dolomite polypropylene composites (DPCs) and WPCs slightly increased with increasing dolomite powder content but the differences were not significant. The flexural modulus and tensile modulus of the WPCs and DPCs increased with increasing dolomite powder content while the flexural strength and tensile strength slightly decreased. The LOI of the WPCs and DPCs increased with increasing dolomite powder content, which extended the times to ignition of WPC and polypropylene. Based on the findings obtained from the present study, it can be said that 6 wt% dolomite powder is the optimum amount in the manufacture of WPC and DPC.
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