Physical properties and bonding quality of laminated veneer lumber produced with veneers peeled from small-diameter rubberwood logs

The peeling of small-diameter rubberwood logs from the current short-rotation practices undoubtedly will produce lower grade veneers compared to the veneers from conventional planting rotation. Hence, this raises the question of the properties of the produced laminated veneer lumber (LVL) from veneers peeled from small-diameter rubberwood logs using the spindleless lathe technology. Different thicknesses of rubberwood veneers was peeled from rubberwood logs with diameter less than 20 cm using a spindleless lathe. Three-layer LVLs were prepared using phenol formaldehyde (PF) adhesive and hot pressed at different temperatures. During the peeling of veneer, lathe checks as deep as 30–60% of the veneer thickness are formed. Owing to deeper lathe check on 3 mm rubberwood veneer, higher pressing temperature significantly increased the gluebond shear strength of the PF-bonded LVL. In addition, lathe check frequency was also shown to influence the bond strength. The presence of higher lathe check frequency on 2 mm veneer increased the wettability, thus facilitating optimum penetration of adhesive for stronger bonding. These findings stress the importance of measuring and considering the lathe check depth and frequency during the lamination process to get a better understanding of bonding quality in veneer-based products.

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The influence of lathe check depth and orientation on the bond quality of phenol-formaldehyde – bonded birch plywood

Holzforschung ◽

10.1515/hf-2012-0161 ◽

2013 ◽

Vol 67 (7) ◽

pp. 779-786 ◽

Cited By ~ 14

Author(s):

Anti Rohumaa ◽

Christopher G. Hunt ◽

Mark Hughes ◽

Charles R. Frihart ◽

Janne Logren

Keyword(s):

Shear Strength ◽

Betula Pendula ◽

Phenol Formaldehyde ◽

Adhesive Bond ◽

Wood Failure ◽

Bond Quality ◽

Laminated Veneer Lumber ◽

Lathe Check

Abstract During the rotary peeling of veneer for plywood or the laminated veneer lumber manufacture, checks are formed in the veneer that are as deep as 70–80% of the veneer thickness. The results of this study show that, during adhesive bond testing, deep lathe checks in birch (Betula pendula Roth.) veneer significantly reduce the shear strength and the percent wood failure of phenol-formaldehyde (PF) – bonded plywood. The results also show that specimens tested with the checks pulled open or closed can fail by different mechanisms. Dried rotary peeled birch veneers were sanded to create uniform surfaces with lathe check depths varying from 30% to 90% of veneer thickness. Then, 7-ply plywood was manufactured with a commercial PF resin. After the preparation of the test specimens, the check depth of each specimen was measured microscopically. Subsequently, bond quality was measured according to EN 314. The results show that veneer checking alone can bring EN 314 specimens to the brink of failure even with an excellent adhesive. These findings stress the importance of measuring the depth of lathe checks and considering the orientations of checks during the testing to get a better understanding of bond quality in veneer-based products.

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Effect of Glue Spreads on the Structural Properties of Laminated Veneer Lumber from Spindleless Rotary Veneers Recovered from Short Rotation Hevea Plantation Logs

Polymers ◽

10.3390/polym13213799 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3799

Author(s):

Pui San Khoo ◽

Kit Ling Chin ◽

Chuan Li Lee ◽

Paik San H’ng ◽

Mohd Sahfani Hafizuddin

Keyword(s):

Mechanical Properties ◽

Small Diameter ◽

Physical And Mechanical Properties ◽

Longitudinal Axis ◽

Modulus Of Rupture ◽

Spread Rate ◽

Minimum Requirement ◽

Laminated Veneer Lumber ◽

Short Rotation ◽

Laminated Panels

Unproductive young rubber trees (15 years old) with smaller diameters (15 to 18 cm) compared to conventional rubber logs, harvested at the age of 25 years old, were selected for the production of laminated panels. Spindleless rotary veneer peeling was applied to logs from short-rotation rubber forest plantations to produce veneers for structural purposes. This raises questions about the utilization of these small-diameter logs with respect to its effect on the quality of veneer and laminated panels produced. This study examines the effect of the glue spread rates on the physical and mechanical properties of rubberwood laminated veneer lumber (LVL). Analysis of variance shows that the application of a 280 g/m2 glue spread rate significantly improved the density, water absorption and dimensional stability of rubberwood LVL. The mechanical properties of rubberwood LVL produced with a 200 g/m2 glue spread rate met the minimum requirement for the 2.1E-3100F stress class; 91.05 MPa for the modulus of rupture in the flatwise direction and 50.23 MPa for compressive strength parallel to the longitudinal axis. The modulus of elasticity in the flatwise direction of 11,189.55 MPa reached the minimum requirement for the 1.5E-2250F stress class.

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Effect of veneer side wettability on bonding quality of Eucalyptus globulus plywoods prepared using a tannin?phenol?formaldehyde adhesive

Bioresource Technology ◽

10.1016/s0960-8524(02)00230-4 ◽

2003 ◽

Vol 87 (3) ◽

pp. 349-353 ◽

Cited By ~ 16

Author(s):

G VAZQUEZ

Keyword(s):

Eucalyptus Globulus ◽

Phenol Formaldehyde ◽

Bonding Quality

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The Influence of the Roll-Laminating Process on the Bonding Quality of Polymer-Coated Steel Interface

Coatings ◽

10.3390/coatings11040472 ◽

2021 ◽

Vol 11 (4) ◽

pp. 472

Author(s):

Jiyang Liu ◽

Qingdong Zhang ◽

Boyang Zhang ◽

Mingyang Yu

Keyword(s):

Bonding Strength ◽

Coated Steel ◽

Interface Bonding ◽

Relevant Research ◽

Bonding Quality ◽

Bonding Area ◽

New Type ◽

Lamination Process ◽

Bonding Rate

Polymer-coated steel (PCS) is a new type of metal packaging material under development, which has better performance in saving resources, energy, and environmental protection. The lamination process has an important influence on the bonding quality of the PCS interface. PCS samples under different lamination temperatures and lamination speeds were prepared through experiments. A binding rate is defined to represent the real bonding area of the PCS interface. The micro-scratch tester and scanner are used to study the influence of the lamination process on the bonding rate and bonding strength of the PCS interface. It is proposed that the bonding rate and bonding strength of the PCS interface increases with the increase of lamination temperature and increases with the decrease of lamination speed. The PCS interface bonding rate and bonding strength are positively correlated. SEM and DSC experiments revealed the cause of bubbles on the PCS surface. It is proposed that controlling the uniformity of the TFS surface temperature can reduce the quality defects of PCS surface bubbles. Relevant research results bring guiding significance for the formation of enterprises.

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Effects of Selected Parameters on the Bonding Quality and Temperature Evolution Inside Plywood During Pressing

Polymers ◽

10.3390/polym12051035 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1035 ◽

Cited By ~ 2

Author(s):

Pavlo Bekhta ◽

Ján Sedliačik ◽

Nataliya Bekhta

Keyword(s):

Heating Rate ◽

Phenol Formaldehyde ◽

Temperature Evolution ◽

Efficient Production ◽

Pressing Pressure ◽

Bonding Quality ◽

Pressing Time ◽

Temperature Time ◽

Required Quality

This research optimizes the process of plywood production to determine its effectiveness in reducing energy and adhesive consumption for more efficient production with the required quality. The influence of selected parameters including veneer treatment (non-densified and densified), plywood structure, temperature, time and pressure of pressing, on the bonding quality and temperature evolution within the veneer stacks during hot pressing was investigated. Rotary-cut, non-densified and densified birch veneers and phenol formaldehyde (PF) adhesive were used to manufacture plywood samples. The effect of pressure and time of pressing on bonding quality of the plywood was determined. Bonding quality was evaluated by determining the shear strength of the plywood samples. The temperature evolution inside the veneer stacks was measured for birch veneers for different pressing temperatures and pressures for different numbers of veneer layers. The heating rate of the veneer stacks increased as the pressing temperature increased and decreased markedly with an increasing number of veneer layers. At a high pressing pressure, the heating rate of the densified veneer stacks was faster than that of non-densified veneers at the same pressure. The use of densified veneers for the production of plywood can lead to a shorter pressing time (17–50% reduction), lower glue consumption (33.3% reduction) and a lower pressing pressure (22.2% reduction) without negatively impacting the bonding strength of the plywood.

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Influence of natural surface ageing on bonding quality of thermally modified oak and beech wood

Drvna industrija ◽

10.5552/drvind.2019.1918 ◽

2019 ◽

Vol 70 (3) ◽

pp. 273-278

Author(s):

Vjekoslav Živković ◽

Gustav Gabrek ◽

Goran Mihulja

Keyword(s):

Contact Angle ◽

Shear Strength ◽

Wood Species ◽

Contact Angles ◽

Bonding Quality ◽

Natural Surface ◽

Lamination Process ◽

Thermally Modified Wood ◽

Modified Wood

This paper presents the influence of natural surface ageing in indoor conditions on bonding quality of thermally modified wood used in structural laminated products. Two unmodified and thermally modified wood species were used for the experiment: oak and beech. Samples were planed and glued with MUF adhesive 2 hours, 1, 2, 6, 10, and 18 days after planing. Properties of laminated beech and oak beams, namely shear strength, delamination and contact angle, were measured in order to detect 1) suitability of wood species for lamination process and 2) influence of extended storage time after planing on properties of laminated wood. Generally, both native and thermally modified beech exhibited better results of shear strength and delamination and had lower contact angles compared to oak and thermally modified oak. Results of the delamination test (total delamination) indicate time dependence of surface ageing. Both unmodified and thermally modified beech may be successfully laminated at least up to 2 days after planing, whereas neither oak nor thermally modified oak are suitable for lamination process due to excessive delamination. Results of delamination may be related to contact angle measurements. Shear strength of glue lines did not show any influence on natural surface ageing. However, whereas beech and thermally modified beech samples exhibited almost the same values of the shear strength regardless of the duration of surface ageing, there is an obvious difference in shear strength of oak and thermally modified oak samples.

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Production of plywood panels from Pinus taeda using veneers of differing densities and phenol-formaldehyde resin with high and low molecular weights

CERNE ◽

10.1590/s0104-77602013000200016 ◽

2013 ◽

Vol 19 (2) ◽

pp. 315-321

Author(s):

Graciela Ines Bolzon de Muniz ◽

Setsuo Iwakiri ◽

Lívia Cássia Viana ◽

Mário Andrade ◽

Cristiane Weber ◽

...

Keyword(s):

Molecular Weight ◽

Pinus Taeda ◽

Cold Water ◽

Phenol Formaldehyde ◽

Water Immersion ◽

Line Strength ◽

Formaldehyde Resin ◽

Low Molecular Weight ◽

Bonding Quality

This study aimed to evaluate the bonding quality of plywood panels from Pinus taeda using low and high molecular weight phenol-formaldehyde resin and veneers from three different density classes. The experiment consisted of six treatments, each of which produced three panels (replicates). Tests were conducted to evaluate glue line strength to shear stress after two boiling cycles and after 24 hours of cold water immersion. Also determined was the percentage of defects in wood samples. Results indicated that the density classes being assessed differed statistically. However, no significant difference was found between panels produced with high and panels produced with low molecular weight resin as to the mean values of glue line strength, whether subjecting them to two boiling cycles or after 24 hours of cold water immersion. Interactions between different density classes and adhesive formulations were found not significant either. Low molecular weight resin (BPM) and panels produced with higher density veneers were found to have better behavior, regarding both bonding strength and percentage of defects. It was concluded that the bonding quality of plywood panels from Pinus taeda was satisfactory after using different densities of veneer and also high and low molecular weight phenolic resins. All treatments were found to comply with minimum requirements established in European standard EN 314-1/1993, which addresses bonding quality of plywood panels.

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Proteinase and phospholipase activities and development at different temperatures of yeasts isolated from bovine milk

Journal of Dairy Research ◽

10.1017/s0022029911000434 ◽

2011 ◽

Vol 78 (4) ◽

pp. 385-390 ◽

Cited By ~ 6

Author(s):

Priscilla A Melville ◽

Nilson R Benites ◽

Monica Ruz-Peres ◽

Eugenio Yokoya

Keyword(s):

Dairy Products ◽

Room Temperature ◽

Bovine Milk ◽

Raw Milk ◽

Pathogenic Potential ◽

Proteinase Production ◽

Different Temperatures ◽

Quality Of Milk ◽

Means Of Transmission

The presence of yeasts in milk may cause physical and chemical changes limiting the durability and compromising the quality of the product. Moreover, milk and dairy products contaminated by yeasts may be a potential means of transmission of these microorganisms to man and animals causing several kinds of infections. This study aimed to determine whether different species of yeasts isolated from bovine raw milk had the ability to develop at 37°C and/or under refrigeration temperature. Proteinase and phospholipase activities resulting from these yeasts were also monitored at different temperatures. Five genera of yeasts (Aureobasidium sp., Candida spp., Geotrichum spp., Trichosporon spp. and Rhodotorula spp.) isolated from bovine raw milk samples were evaluated. All strains showed one or a combination of characteristics: growth at 37°C (99·09% of the strains), psychrotrophic behaviour (50·9%), proteinase production (16·81% of the strains at 37°C and 4·09% under refrigeration) and phospholipase production (36·36% of the isolates at 37°C and 10·9% under refrigeration), and all these factors may compromise the quality of the product. Proteinase production was similar for strains incubated at 37°C (16·81% of the isolates) and room temperature (17·27%) but there was less amount of phospholipase-producing strains at room temperature (15·45% of the isolates were positive) when compared with incubation at 37°C (36·36%). Enzymes production at 37°C by yeasts isolated from milk confirmed their pathogenic potential. The refrigeration temperature was found to be most efficient to inhibit enzymes production and consequently ensure better quality of milk. The viability of yeasts and the activity of their enzymes at different temperatures are worrying because this can compromise the quality of dairy products at all stages of production and/or storage, and represent a risk to the consumer.

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A Comparative Study of Soldering Temperatures and Materials on the Reliability of Photovoltaic Modules

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.562-564.188 ◽

2012 ◽

Vol 562-564 ◽

pp. 188-191

Author(s):

Keh Moh Lin ◽

Yang Hsien Lee ◽

Wen Yeong Huang ◽

Po Chun Hsu ◽

Chin Yang Huang ◽

...

Keyword(s):

Comparative Study ◽

Lead Free ◽

Automatic Process ◽

Lead Free Solder ◽

Snagcu Solder ◽

Photovoltaic Modules ◽

Soldering Process ◽

Different Temperatures ◽

Free Solder

To find out the important factors which decisively affect the soldering quality of photovoltaic modules, solar cells were soldered under different conditions (different temperatures, PbSn vs. SnAgCu solder, manual vs. semi-automatic). Experimental results show that the soldering quality of PbSn under 350°C in the semi-automatic soldering process was quite stable while the soldering quality of lead-free solder was generally unacceptable in the manual or semi-automatic process under different temperatures. This result indicates that the soldering process with lead-free solder still needs to be further improved. It was also found that most cracks were formed on the interface between the solder and the silver paste and then expanded outwards.

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