Planed Surfaces Research Articles

The effect of weathering on the surface moisture conditions of Norway spruce under outdoor exposure

ABSTRACT Understanding wood surface moisture variations is fundamental to the modelling of moisture content. Exposure to sunlight, fluctuating temperature and rain leads to superficial deterioration and reduced surface hydrophobicity. Here, the effect of weathering was studied through monitoring the surface and global moisture content of axially matched pre-weathered and planed sets of specimens exposed outdoors over 18 months. The difference in surface conditions was characterised by analysing the rain-induced peaks. The results suggest that, following precipitation, weathered surfaces remain wet over a longer time period. No effect was observed through the global moisture content. After one year of exposure, the difference between pre-weathered and planed surfaces was small to insignificant. In service life modelling, it is therefore unnecessary to consider the unweathered state and simulations should target the behaviour of weathered wood. Numerical simulations were able to capture the general behaviour of the surface and global moisture content, but discrepancies over individual peaks were observed. Finally, the study demonstrates how peak analysis and signal analysis can be used for isolating subtle differences between time-series of surface moisture content. The same techniques can be used in future studies to characterise other factors influencing surface conditions, such as wood species and detailing.

Effects of helix angle and feed per knife on the surface quality of sugar maple and black spruce boards produced by planing

ABSTRACT A conventional straight knife cutterhead and three helical knife cutterheads were tested for planing sugar maple (Acer saccharum Marsh.) and black spruce (Picea mariana (Mill.) B.S.P.) woods. The effects of helix angle and feed per knife (FK) on roughness, tactical perception, and anatomical features of the planed surfaces were evaluated. Rk and Rpk parameters were found to be more descriptive in evaluating the roughness of these woods and proved to be good indicators of tactile perception. Roughness increased as the helix angle and feed per knife increased for both wood species. Sugar maple showed smoother surface than black spruce. Surfaces planed with helical knives showed a fuzzy texture resulting from cell-wall fibrillation. For sugar maple wood, the differences in roughness between straight and 40° helical knives were small. Therefore, the latter must be preferred for planing this species. Roughness of planed black spruce also increased as helix angle increased and in this case its effect depended on FK. The straight knife produced the lowest roughness, for all studied FKs. Planing with helical knives produced higher roughness as a result of cell-wall fibrillation. This defect was more pronounced than that of sugar maple, and by far more present with helical knives of 50° and 60°. Therefore, straight knives working at low FK (1.3 mm) should be preferred for planing black spruce wood when roughness is a critical concern. Possible benefits provided by rougher surfaces planed by helical knives are discussed.

Osmotic gradients and transretinal water flow-a quantitative elemental microanalytical study of frozen hydrated chick eyes.

Optical clarity and efficient phototransduction are necessary for optimal vision, however, how the associated processes of osmoregulation and continuous fluid drainage across the whole eye are achieved remains relatively unexplored. Hence, we have employed elemental microanalysis of planed surfaces of light-adapted bulk frozen-hydrated chick eyes to determine the unique intracellular elemental localization, compositions, and hydration states that contribute to maintaining osmotic gradients and water flow from the vitreous, across the retina, retinal pigment epithelium (RPE), to choroid and sclera. As expected, the greatest difference in resultant osmotic concentration gradients, [calculated using the combined concentrations of sodium (Na) and potassium (K)] and tissue hydration [oxygen-defined water concentration], occurs in the outer retina and, in particular, in the RPE where the apical and basal membranes are characterized by numerous bioenergetically active, osmoregulating ion transport mechanisms, aquaporins, and chloride (Cl) channels. Our results also demonstrate that the high intracellular Na+ and K+ concentrations in the apical region of the RPE are partially derived from the melanosomes. The inclusion of the ubiquitous osmolyte taurine to the calculation of the osmotic gradients suggests a more gradual increase in the osmotic transport of water from the vitreous into the ganglion cell layer across the inner retina to the outer segments of the photoreceptor/apical RPE region where the water gradient increases rapidly towards the basal membrane. Thus transretinal water is likely to cross the apical membrane from the retina into the RPE cells down the Na+ and K+ derived osmotic concentration gradient and leave the RPE for the choroid across the basal membrane down the Cl- derived osmotic concentration gradient that is sustained by the well-described bioenergetically active RPE ion transporters and channels.

COMPARTIMENTAÇÃO GEOAMBIENTAL DOS PLANALTOS RESIDUAIS DO EXTREMO OESTE POTIGUAR

A paisagem e o meio físico podem ser visualizados como um conjunto de resultados de várias alterações físicas, biológicas e antrópicas que aconteceram em outras eras. Deste modo, esta pesquisa teve o objetivo de realizar a compartimentação Geoambiental dos Planaltos Residuais do Extremo Oeste Potiguar a partir de uma análise sistêmica, pois esta área tem uma significativa importância para o interior do estado Rio Grande do Norte, apresentando a maior elevação altimétrica do estado. Para tanto, o presente estudo fundamenta-se em autores como Bertrand (1972), Sotchava (1997), Christofoletti (1999), além de outros que aplicaram a Teoria Geossistêmica, como Rodriguez (2007) e Medeiros (2016). Para a elaboração dos produtos cartográficos, utilizou-se o Software QGIS Lyon 2.14com shapefileda CPRM (2010) e dados do IBGE (2018) e do Projeto TOPODATA, os quais foram processados e recortados para área de estudo na escala na escala 1:350.000. Nas observações de campo, a metodologia utilizada foi a de Cavalcanti (2014), através do levantamento de 83 pontos amostrais distribuídos na área de estudo. A área estudada contém três Unidades Geoambientais: Alinhamentos Serranos e Maciços, Chapadas e Platôs e Superfície Aplainadas Retocadas. Espera-se que essa pesquisa subsidie futuros planejamentos ambientais e urbanos.

Performance of solvent-borne coating on red oak wood prepared by two alternative surfacing processes

The performance of varnishes applied to wood will depend on the way in which its surfaces have been prepared. Sanding has traditionally been used to prepare surfaces prior to coating. This process is one of the most expensive operations in woodworking, which produces a high level of wood dust. As a result, other surfacing processes are actually studied as alternatives to sanding for wood finishing. The effects of two alternative processes, oblique cutting and helical planing, on surface properties and coating performance of red oak wood were thus studied. Surfaces were prepared using three oblique angles (oblique cutting) and three wavelengths (helical planing) before application of an interior solvent-borne coating. Surface properties were examined by roughness parameters, scanning electron microscopy micrographs, wetting behavior, and surface energy. Coating performance was assessed by pull-off tests on aged and un-aged specimens. Oblique and helical planed surfaces at the highest oblique angle and wavelength, respectively, presented micro-torn grain, a certain level of micro-fuzziness, and higher roughness. Oblique-cut surfaces were more wettable than helical-planed surfaces. The wettability of machined surfaces decreased with increasing surface roughness within each process. Despite oblique samples had shown lower values of pull-off strength prior to aging treatment, these surfaces had statistically similar pull-off strength to those of helical-planed specimens after aging. As a result, the latter surfaces had higher loss in adhesion after accelerated aging. Results suggest that the use of oblique angles of 15° and 35° should provide a better coating performance in oblique-cut surfaces. On the other hand, no significant differences were detected between wavelengths during helical planing with respect to coating performance. Thus, a low (1 mm) or high wavelength (2.1 mm) could be used, depending on whether smoothness or productivity are required, in order to reduce sanding dependence for finishing red oak wood.

Reativação Tectônica Quaternária no Domínio Sul da Província Borborema, NE do Brasil: Integração de Dados Morfométricos, Geológicos e Geofísicos da Bacia do Rio Una

An integration of data in different scales was built aiming to identify possible effects of tectonic reactivations of Cenozoic origin (post-rift), related to the continental basement adjacent to the coastal zone of Pernambuco marginal basin, over which was formed the hydrographic basin of the Una River. The study was based in the integration of morphometric parameters of the Una River channel modeled with satellite radar imagery, geological data, and 2D multichannel shallow seismic data acquired over the river channel in the proximities of Barreiros and Palmares cities. Morphometric analysis comprised the calculation of the length-gradient index along the longitudinal profile of the Una River. Geological data were collected from basement outcrops near the cities of Barreiros and Palmares. Barreiras Formation outcrops located in the coastal basin, near the city of Sao Jose da Coroa Grande were also investigated. Analysis of longitudinal profile showed that the Una River channel was established over three planed surfaces, created by successive events of uplift and erosion of Borborema Plateau which controlled the compartmentation of this hydrographic basin. The calculation of length-gradient index showed the occurrence of first order anomalies in the middle course, and second order anomalies in the middle and low course of the river profile. Anomalies of first and second order are located over the main shear zones of the Pre-Cambrian basement, trending NE-SW. These anomalies are also related to younger fractures and faults trending NW-SE. Interpretation of seismic sections showed a series of high angle faults within the basement which affected Quaternary and holocenic deposits. The investigation also found faults in deposits of Barreiras Formation (Miocene) located in the coastal zone near the border of the Pernambuco Basin. Faults in basement rocks and in sedimentary deposits formed flower-like structures, which indicates the actuation of a transcurrent regime in the continental margin, with a maximum compression trending E-W and extension trending N-S. This regime affected the morphology of the Una River profile and the sedimentary deposits formed in its drainage basin.

Stability of planed and precision planed solid wood surfaces due to wetting

The upper cell layers of machined solid wood surfaces will usually be damaged and compacted due to cutting forces. The deformation zone may be instable due to temperature and moisture variations as a consequence of artificial surface treatment or environmental interaction. Therefore, an evaluation method of surface stability in this respect would be desirable. In the frame of the new developed surface roughness evaluation method an individual wetting procedure has been developed, whilst surfaces have been characterized by 3D roughness measurement. The stability of surfaces is characterized by appropriate roughness ratios measured before and after wetting. The core depth Sk of the Abbott parameters is the most sensitive indicator to any changes in the deformation zone. Different machining processes may produce surfaces with different stability but wood species have also definite influence on the surface stability, probably due to their density and moisture conduction properties. Latter is supported by the fact that the half-time of moisture evaporation from surfaces may differ considerably. In these experiments, planed and precision-planed surfaces were compared. According to the working principle of the precision planers the planing tool is held stationary whilst the work piece does the feeding motion, thus the blade produces a very thin slice. Using this machine, the machining roughness can be reduced to minimum as it is possible to avoid formation of cycloid arcs (like in case of traditional planing) and also possible to avoid dust formation (like in case of sanding). Investigations were conducted on Norway spruce (Picea abies), larch (Larix decidua), scots pine (Pinus sylvestris), sessile oak (Quercus petraea), black locust (Robinia pseudoacacia), aspen (Populus tremula) and beech (Fagus sylvatica). Black locust and the sessile oak have had most stable surfaces by both machining methods. The deformation zone of precision planed surfaces has been proven to be more stable than the one of planed surfaces for all wood species. Keywords: Cutting parameters, deformation zone, planed surface, roughness, surface stability

Stability of thermosmoothed and precision planed solid wood surfaces

The outer cell layers of a machined solid wood surface usually collapse and compact during processing due to the cutting forces. This layer is called deformation zone. The deformation zone is excessively instable, varies with temperature and MC variation of the environment. Usual surface investigations like surface roughness or surface tension measurements provide only few and indirect information about the status of the deformation zone, although this is the layer to adhere. Suggestion is made to consider the behaviour of the deformation zone during wetting instead of single parameters, in order to better characterize the status of the surface and its expected reaction when treated with water based materials. In this research, the focus has been on describing the behavior of the deformation zone of precision planed and thermosmoothed solid wood surfaces during wetting with distilled water. An individual wetting procedure has been developed, whilst surfaces have been characterized by 3D roughness measurement. The evaluation has been performed after defining the convenient roughness parameter as indicator of surface topography changes of the deformation zone due to wetting. Based on indicators sequence has been set among wood species and machining types regarding the answer given by their deformation zone to wetting. Although the two cutting methods offer the smoothest machined surface, their stability to wetting with water differs considerably. The deformation zone of precision planed surfaces has been proven to be more stable than the one of thermosmoothed surfaces. Black locust preserved its stability even when thermosmoothed.

445-nm diode laser-assisted debonding of self-ligating ceramic brackets

This study determined the influence of irradiation on aesthetic ceramic brackets with a novel 445-nm diode laser prior to debonding on the bracket failure mode. Thirty ceramic brackets (In-Ovation® C, GAC) were standard-bonded to the oral and buccal planed and polished enamel surfaces of 15 caries-free human 3rd molars. Prior to study-blinded debonding, the brackets in the laser group were irradiated with the diode laser (SIROLaser Blue®, Sirona), while the irradiation was simulated within the conventional group. To determine the degree of enamel fractures and the adhesive remnant index (ARI) before debonding (T0), after debonding (T1) and after removal of the remaining composite using a rotating fraise (red ring, Comet) (T2), micrographs of the enamel surface at 10-fold and 20-fold magnifications were taken. Additionally, the enamel surface was investigated using seven randomly chosen samples from each group at every time point by SEM at 200-fold and 500-fold magnifications. In the laser group, the ARI-score was statistically significantly reduced (p<0.05) at 10-fold and 20-fold magnifications compared to the conventional group, while enamel fractures were not found at any magnification in either group at T1. Enamel fractures and grinding marks were increasingly found in the conventional group by SEM at T2. Irradiation with the novel diode laser prior to debonding of ceramic brackets significantly changes bonding failure in terms of less remaining adhesive. This is of clinical importance as the risk of enamel fractures and chair time can be reduced.

Influence of enamel matrix derivative on healing of root surfaces after bonding treatment and intentional replantation of vertically fractured roots.

The objectives of this study were to histopathologically evaluate cementum regeneration on root surfaces when an enamel matrix derivative (EMD) was used to bond a vertically fractured root and to evaluate the effectiveness of EMD in inhibiting root resorption. A total of 40 roots from 24 maxillary premolars in beagles were used. The root was vertically fractured using a chisel and mallet. Super-Bond was then used to bond the fractured root. In the experimental group, the root surface was treated with ethylenediaminetetraacetic acid and an EMD. The control group received no treatment. The root was then replanted in its original location. Histopathological observation and measurement using image-analyzing software were carried out after 8 weeks. In the experimental group, shallow resorption cavities developed on the root planed surfaces with new acellular cementum appearing over them. In the control group, no new cementum was seen on the planed surfaces, and there was connective tissue joining the roots. In some of the samples, resorption and multinucleated giant cells were seen. The experimental group showed a significantly larger volume of cementum formation (P < 0.001), and the volume of root resorption was significantly smaller (P = 0.004). When bonding and replanting tooth roots after a vertical fracture, the application of EMD was effective in regenerating cementum on root surfaces from which periodontal ligament had been lost in the area around the fracture line and in reducing the incidence of root resorption.

Морфотектоніка Мізоцької височини

The aim of this work is the interpretation results of morphotectonic analysis of Myzotska Upland for investigation its neotectonic history and identifying regional morphotectonic differences. We used planed surface reconstruction method and stream gradient index (SL index). We recognized that Myzotska Upland consist of several blocks with differentiated neotectonic movements. Northwest and western ledges of upland have tectonic origin but northeast, northern and southern ledges have erosional origin. Northern and eastern parts have tectonic structure that more similar to Rivnenska Upland than to other territories of Myzotska Upland. Parts of Myzotska Upland have similar geomorphological structure but different tectonic history. Key words: morphotectonics, neotectonic movements, stream gradient index (SL index), faults, planed surfaces, Volynska Upland, Myzotska Upland.

Paleosols in low-order streams and valley heads in the Araucaria Plateau – Record of continental environmental conditions in southern Brazil at the end of MIS 3

The Araucaria Plateau is a geomorphological unit that occupies approximately three-quarters of the terrain in the southern region of Brazil. The plateau displays different altitudinal levels (600 to <1400 m a.s.l.) that are locally recognized as remnants of planed surfaces (S8–S1). These surfaces are maintained by basic (S3–S8) and acidic (S1 and S2) volcanic flows from the Neocretaceous period of the Paraná Basin. The largest extent of this plateau is located in a humid subtropical climate zone. Colluvial, colluvial–alluvial, alluvial sediments and paleosols (Ab diagnostic horizons) occur predominantly in S2. The paleosols are located in low-hierarchical-order fossil valleys (first- to fourth-order in Strahler's stream classification) and valley heads, which are referred to as paleovalleys in this paper. We employed these paleosols as stratigraphic level markers of the pedogenesis of the regional Upper Quaternary and propose their importance as records of the paleoenvironmental conditions of the Araucaria Plateau in areas above 1200 m a.s.l. These paleosols were dated by 14C and show ages between 23.8 ± 0.05 kyr BP (28.06–29.08 kyr cal. BP) and 41.16 ± 0.48 kyr BP (44.13–45.58 kyr cal. BP). The calibrated ages are related to Marine Isotope Stage 3 (MIS 3), in which the last period of global warming occurred (approximately 60–25 kyr cal. BP). We integrated the morphological, pedogeochemical, clay fraction mineralogy, micromorphological and δC-13 analyses of five paleosols from S2 to verify the paleoenvironmental conditions of the Araucaria Plateau and its correspondence with the paleoclimatic phenomena that were identified on a global scale during MIS 3 in the Southern Hemisphere. We obtained the following conclusions: a) the properties of paleosols reflect pedological processes that are adjusted to the paleoenvironmental conditions at the end of MIS 3 and the transition to MIS 2 (Last Glacial Maximum); b) aplasmogenic partial acidolysis was the predominant pedogeochemical process during MIS 3; c) during this period, the water regime was sufficiently humid to develop hydromorphic horizons in the valley bottoms of the entire drainage network to the valley heads; d) regional change toward a drier hydric regime occurred in MIS 2, when erosion of the paleosols predominated; and e) in MIS 1 (current Holocene interglacial), burial of the paleosols and relief inversion occurred, which resulted in fossilization of the valleys.

Effect of Densification Temperature and Some Surfacing Techniques on the Surface Roughness of Densified Scots Pine (Pinus sylvestris L.)

The effects of densification temperature, planing, circular sawing, and sanding on the surface roughness of densified Scots pine using the open-system thermodynamic method were studied. Densification was applied to Scots pine at 6 MPa pressure and at temperatures of 120 °C, 140 °C, and 160 °C. A total of 1040 specimens (160 × 50 × 10 mm) were prepared using the surfacing techniques of planing, circular sawing, and sanding. The surface roughness of the specimens were measured in conformance with the TS 2495, EN ISO 3274, and the TS 6212 EN ISO 4288 standards, and the results were subjected to statistical analysis. The surface roughness of the planed surfaces was 26% lower, of the surfaces cut circularly was 38% lower, and of the sanded surfaces was 32% lower in densified Scots pine compared to undensified Scots pine. According to the densification temperature, while the lowest roughness was obtained in the densified specimens at 140 °C, raising the temperature to 160 °C increased the roughness. An increase in the number of blades in planing, the tooth number in circular sawing, and the grit number in planing decreased the surface roughness. Furthermore, the roughness was less in tangential surfaces compared to radial surfaces.

Pedogeochemistry and micromorphology of oxisols – A basis for understanding etchplanation in the Araucárias Plateau (Southern Brazil) in the Late Quaternary

Approximately five years ago, the Working Group on Ancient Surfaces and Long-Term Landscape Evolution was created to raise planed surfaces in Brazil, Argentina, Uruguay and Paraguay with the aim of establishing regional correlations of planed surfaces after the formation of the Gondwanan rocks in South America. In Brazil, planed surfaces were recognized and classified between 1940 and 1960 and were given various designations and different age estimates based on regional morphostratigraphic correlation attempts. In the last twenty years, the assumptions of those attempts began to be questioned on a large scale by studies in which empirical observations, mediated by the use of new methodologies, did not indicate such a direct relationship between the paleosurfaces and their long-term erosive origin. We identified eight staggered surfaces in the Araucárias Plateau, Southern Brazil, between the Iguazu and Uruguay Rivers. Initially, we attempted to understand the planed surfaces as classic pediplains, but we found weathering profiles of different thicknesses with oxisols downstream of the knickpoints, instead of correlative deposits. We understand these surfaces as planed surfaces or paleosurfaces without erosive interrelation between them, resulting from the action of etchplanation processes. This idea contradicts the classical perspective of Brazilian geomorphology that attributes the cyclical alternation of Quaternary paleoclimates to the evolution of the model of the subtropical landscapes. The hypothesis begins from the assumption that the model evolved from the binomial morphogenesis/pedogenesis in phase with the glacial/interglacial cycles. In this study, we attempt to demonstrate that the climactic controls on morphogenesis/pedogenesis are mediated by the responses of the weathered mantle on the scale of its chemical and microstructural organization, which does not always validate previous theoretical assumptions. In this article, we use the chemical composition, weathering indices, iron, mineralogy of the clays and micromorphology of the oxisols of surface 6 to propose a first approximation of the evolution of the planed surfaces regarding etchplanation in southern Brazil. The surfaces' pedogeochemical and micromorphological properties reveal the following: a) hydrolysis is the main process of geochemical loss of geomorphic surfaces; b) geochemical erosion is more intense in the glacial periods, when the decreased temperature favors slower weathering in a more continuous manner; c) the pedobioclimatic imbalance generated by the input in interglacial periods favors mechanical erosion of the ground surface due to the substitution of the structure in blocks by microaggregates, which reduces the cohesiveness of the mantles of alteration; d) morphogenesis is most important in interglacial periods, promoting the truncation of oxisols; e) the oxisols from the remnants of the planed surfaces are actually renewed profiles younger than 500 Ky BP; f) models of long-term chemical denudation must take into consideration short-duration changes (≤25 Ky) in the pedogeochemical and structural processes of the solum.

REVISÃO DOS CONHECIMENTOS SOBRE O RELEVO DO PLANALTO ATLÂNTICO BRASILEIRO: INCÓGNITAS QUE AINDA PERSISTEM

This paper attempts to outline the current state o knowledge on the importance of the Brazilian Atlantic Plateau, through an extensive review of the literature on studies conducted since the 1930s to the present day. In this review, it is possible to observe the development of a true school of Brazilian geoscientific thought. Firstly, there is a line of erosive geomorphological models with tectonic implications. Secondly, it is possible to find another strain with morphoclimatic approach based on Quaternary climate change. Thirdly, there is a sequence of research that is not primarily geomorphological, but whose focus is mainly associated with tectonic geomorphic elements. And lastly, there are studies highlighting the formation through geochemical processes and even the geomorphic features of planed surfaces built up between the major compartments of regional reliefs (Serra do Mar and Mantiqueira). The conclusion is that none of these lines alone is able to fully explain the geomorphic genesis of the Plateau, remaining unknowns that challenge old approaches. New questions arise and old ones persist, across period to period and school to school.

Evolution of the Driftless Area and Contiguous Regions of Midwestern USA Through Pleistocene Periglacial Processes~!2009-09-27~!2009-12-09~!2010-03-26~!

In the Driftless Area region and contiguous regions (Paleozoic Plateau and Iowan Erosion Surface) within the U.S.A., there are a variety of northwest to southeast oriented landforms. They are interpreted to have been formed by periglacial nival and cryoplanation erosion processes during the Pleistocene. It is proposed that the oriented landforms are initiated by erosion focused along the edges of northwest-southeast trending snow dunes. Over time, cryopedimentation/cryoplanation widens some of the landforms into broad pediments or planed surfaces. These processes left other landforms standing as narrow, northwest-southeast trending, isolated ridges (paha and rock paha). Oriented valleys were carved in bedrock in some areas and were also carved in loess or loess underlain by till within other areas. An overall regional northeast to southwest trend of increasing amounts of pre-Illinoian till cover is interpreted to form by different degrees of widespread nival erosion. The Pleistocene wind was an important, indirect cofactor in the development of both the till pattern and the previously mentioned landforms. Determining these events not only helps us to formulate an evolutionary model for all three regions as a unit but also justifies speculation that the Driftless Area may have been glaciated during pre-Illinoian times.

Planation of the relief of terrestrial surface

Some problems related to the evolution of relief with the formation of planed surfaces are considered. Target-oriented classifications of planed surfaces are suggested. The paper raises the question concerning tectonic planation of relief, and the relationship of the processes of planation and formation of weathering crusts. The distinctive features of equiplanation in the Earth's northern and southern hemispheres, and the importance of aeolian processes in them are discussed. Attention is drawn to the studies of the planation processes of the relief in the regions under the ice and of the bottom of the World Ocean. The article underlies the need for perfection of the conceptual-terminological body of the theory of planation surfaces.

The influences of log storage and kiln drying climate on the colour of non-steamed beech (Fagus sylvatica L.) wood

Discolouration during the drying of non-steamed beech is a major industrial concern. The generally preferred yellow-white colour can easily develop a reddish or dull grey appearance during drying. In this study, the influences of log storage time and kiln drying climate on the colour of non-steamed sawn beech have been investigated and quantified. Samples 27×87 mm in cross section were dried in laboratory kilns and the average colour, in CIELAB colour space was measured on dry planed surfaces using a photoelectric colorimeter. Log storage for 13 weeks under low-temperature conditions had no visible effect. The reddish discolouration is mainly temperature related while the greyish discolouration is mainly controlled by the equilibrium moisture content (EMC) during the initial drying. Within the investigated climate interval, the EMC was twice as important as temperature for the final colour. Regression models developed show that, as long as the EMC is kept below 15%, a temperature of up to 37°C can be allowed without any visually detectable discolouration.

Effects of cutting parameters on surface quality of paper birch wood machined across the grain with two planing techniques

Helical planing and face milling were applied across the grain to surface paper birch wood prior to coating application. Three feed speeds and three cutting depths were evaluated for face milling while three cutting depths were studied for helical planing. The roughness and wetting properties of wood as well as pull-off strength of a solvent-borne coating after aging were evaluated. For helical planing, no significant effects of the cutting depth on roughness and wetting properties were found. For face milling, the cutting depth had no significant effect on the surface roughness while it had a significant impact on the wetting properties. The feed speed affected significantly both parameters. Furthermore, none of these parameters had a significant effect on the pull-off strength. However, helical planing produced smoother surfaces with equivalent wetting properties and higher pull-off strength than face milling. Scanning electron microscopy showed more exposed cell lumina and sound cells for helical planed surfaces, which enhanced their wetting and adhesion properties.

Shear strength of calabrian pine (Pinus brutia Ten.) bonded with polyurethane and polyvinyl acetate adhesives

AbstractIn this study, the change in shear strength on radial and tangential surfaces of Calabrian pine (Pinus brutia Ten.) wood having different roughness values as the result of sawing with a circular ripsaw, planning, and sanding, and bonded with polyurethane (PU) and polyvinyl acetate (PVAc) adhesives at the pressure levels of 3, 6, and 9 kg f/cm2 were studied. A total of 360 specimens of each, prepared with the objective of being able to determine the effect of the variables on bond performance, were subjected to the shear test in the universal test machine in accordance with the ASTM D 905–98 standard. The values obtained were analyzed statistically and the results were interpreted. The highest shear strength (11.83 N/mm2) for plane of cut was obtained on the tangential surface after sanding and applying PVAc adhesive with a pressing pressure of 9 kg f/cm2. The lowest shear strength (6.01 N/mm2) was obtained in the joinings made on the planed surfaces by using PU adhesive and a pressing pressure of 3 kg f/cm2. The highest shear strength (9.10 N/mm2) on the radial surface was obtained after sanding and applying PVAc adhesive and pressing with a pressure of 6 kg f/cm2. The lowest shear strength (3.76 N/mm2) was obtained in the specimens whose surfaces were sanded and by using PU adhesive and with a pressing pressure of 3 kg f/cm2. In general, in the radial surfaces, just like in the tangential surfaces, the specimens bonded with PVAc produced a higher shear strength compared to those glued with PU. According to these results, it is definitely necessary to sand the surfaces prior to the bonding process to have a higher shear strength. The bonding process should be made on the tangential surfaces with higher pressures. The PVAc adhesive should be preferred instead of the PU adhesive. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4856–4867, 2006