COLLAPSE IS ALMOST CERTAIN TO OCCUR IN THE INDUSTRIAL DRYING OF EUCALYPTUS NITENS AND, AS SUCH THIS PREVENTS THE LUMBER MANUFACTURING INDUSTRY IN CHILE FROM PRODUCING COMMERCIAL SOLID WOOD PRODUCTS FROM THIS SPECIES. THIS PROBLEM IS STILL UNSOLVED, AND DIFFERENT STUDIES TO REDUCE COLLAPSE ARE CURRENTLY UNDERWAY. IN THIS EXPLORATORY STUDY, SHRINKAGE AND COLLAPSE AFTER DRYING OF EUCALYPTUS NITENS WAS MEASURED FOR BOARDS CUT FROM DIFFERENT RADIAL LOCATIONS WITHIN THE STEM (CORE, TRANSITION, AND OUTER WOOD FROM PITH TO BARK) AND HAVING DIFFERENT ANNUAL RING ORIENTATIONS (FLAT-SAWN AND QUARTER-SAWN). THOUGH EXPLORATORY, THE RESULTS APPEAR TO CONFIRM THAT PIECES THAT WERE CUT FROM THE CENTER OF THE TREES WERE LESS SUSCEPTIBLE TO COLLAPSE THAN PIECES CUT FROM THE TRANSITION ZONE BETWEEN THE CENTER AND THE PERIPHERY. ON AVERAGE, COLLAPSE IN TRANSITION WOOD WAS APPROXIMATELY 50% HIGHER THAN THE COLLAPSE OBSERVED IN WOOD CUT FROM THE CENTRAL ZONE OF THE TREES.

THIS STUDY DEALS WITH THE EFFECT OF HEAT TREATMENT ON PINUS OOCARPA SPECIMENS FROM FOREST PLANTATIONS IN COLOMBIA. THE EFFECTS OF TWO HEAT TREATMENTS AT 170 AND 190 °C FOR 2.5 H IN SATURATED VAPOR WERE EVALUATED BASED ON THE COLOR, DIMENSIONAL STABILITY, AIR-DRY AND BASIC DENSITIES, MODULUS OF ELASTICITY (MOE), AND MODULUS OF RUPTURE (MOR) IN STATIC BENDING OF SAMPLES. THE EVALUATIONS WERE CARRIED OUT FOLLOWING THE COLOMBIAN TECHNICAL STANDARDS NTC 290 AND 663, AND THE COLOR CHANGES RESULTING FROM HEAT TREATMENTS WERE MONITORED USING THE CIE-LAB, AS WELL AS OTHER STANDARDS FROM THE LITERATURE. THE RESULTS SHOW THAT THERE WAS 2.4% AND 3.3% MASS LOSS OF WOOD MODIFIED AT 170 AND 190 °C, RESPECTIVELY. THE AIR-DRY AND BASIC DENSITIES WERE HIGHER IN 170 °C TREATMENT THAN AFTER 190 °C TREATMENT, AND THE THERMAL MODIFICATIONS APPLIED INCREASED THE DIMENSIONAL STABILITY OF THE TREATED WOOD. AFTER TREATMENT AT 170 AND 190 °C, THE LIGHTNESS TO DARKNESS (L*) WAS REDUCED BY 10% AND 22%; THE A* COORDINATE INCREASED BY 11% AND 26%, CAUSING REDNESS IN THE TREATED WOOD; THE B* COORDINATE INCREASED BY 14% AND 17%; AND THE VALUES OF THE WOOD COLOR SATURATION (C*) INCREASED BY 14% AND 18%, RESPECTIVELY. THE GENERAL COLOR CHANGE (?E*) INCREASED GRADUALLY WITH THE INCREASE IN THE TREATMENT TEMPERATURE, RESULTING IN A HIGH COLOR CHANGE TO A VERY DIFFERENT COLOR. THE BENDING STRENGTH OF THERMALLY MODIFIED WOOD WAS IMPROVED AND SIGNIFICANTLY INCREASED TO VALUES HIGHER THAN THOSE OF UNMODIFIED PINUS OOCARPA WOOD. THE HIGH AIR-DRY AND BASIC DENSITIES, IMPROVED DIMENSIONAL STABILITY AND RESISTANCE TO BENDING, AND ATTRACTIVE APPEARANCE OF THE TREATED WOOD INDICATE THAT THERMAL MODIFICATION IS A PROMISING ALTERNATIVE FOR THE TRANSFORMATION OF PINUS OOCARPA WOOD INTO A RAW MATERIAL WITH A HIGH ADDED VALUE

TO EVALUATE EVOLUTION OF PHYSICAL AND MECHANICAL PROPERTIES DUE TO DRYING AND HEAT MODIFICATION, A LOAD OF RADIATA PINE WOOD WAS SELECTED AND PROPERTIES WERE MEASURED AFTER EACH DRYING PROCESS. THE RESULTS REVEALED INTERESTING CORRELATIONS BETWEEN INTRINSIC FACTORS AND PROPERTIES; THE VALUES OF DENSITY WERE HIGHLY DISPERSED AFTER DRYING OR THERMAL TREATMENT AND UNCORRELATED WITH OTHER PARAMETERS, BUT THE MINIMUM DENSITY VALUES WERE KEPT CONSTANT AFTER HEAT TREATMENT. MOREOVER, WEIGHT LOSS (WL) AND MOISTURE CONTENT (MC) WERE DECREASING PROPORTIONALLY TO THE TREATMENT INTENSITY, DUE TO WOOD?WATER INTERACTIONS, CELL WALL CHANGES, AND THERMAL DEGRADATION OF WOOD FRACTIONS. WL AND MC WERE REASONABLY CORRELATED WITH THE DIMENSIONAL STABILITY, IMPROVING THE DIMENSIONAL STABILITY AFTER DRYING TREATMENTS, BUT KEEPING THE SAME ORDER OF ANISOTROPY. REGARDING THE WOOD STIFFNESS (MODULUS OF ELASTICITY, MOE), IT WAS UNAFFECTED BY THE DRYING TEMPERATURE, AND THE CORRELATIONS BETWEEN MOE AND MC OR WL APPEAR TO BE ACCEPTABLE, AND THE VALUES OF MC OR WL DID NOT ADVERSELY AFFECT THE MOE. HOWEVER, THE MODULUS OF RUPTURE WAS DROPPED DURING THE DRYING PROCESS, OBTAINING THREE DIFFERENTIATED GROUPS WITH A DECREASE IN AROUND 59% AFTER THERMAL MODIFICATION.

COLLAPSE AND DRYING STRESSES ARE CURRENTLY INDUCED DURING THE DRYING OF EUCALYPTUS NITENS IN SOLID WOOD PRODUCTS. THE PURPOSE OF THIS STUDY WAS TO INVESTIGATE THESE DRYING STRESSES BY MEASURING HYGROMECHANICAL STRAINS DURING THE DRYING OF EUCALYPTUS NITENS BOARDS. SMALL SAMPLES OF EUCALYPTUS NITENS WOOD WERE ORIENTED IN THE RADIAL AND TANGENTIAL DIRECTIONS AND TESTED TO DETERMINE THE HYGROMECHANICAL STRAINS DURING THE DRYING PROCESS. THIS EXPERIMENTAL WORK CONSISTED OF CANTILEVERED BENDING TESTS CONDUCTED UNDER VARIABLE RELATIVE HUMIDITY CONDITIONS. TESTS WERE PERFORMED IN A CONDITIONING CHAMBER AT 30 °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

IN THIS STUDY, THE EFFECTS OF THE WOOD QUALITY USED FOR THERMAL MODIFICATION ON THE PHYSICAL AND MECHANICAL PROPERTIES OBTAINED AT TWO TREATMENT TEMPERATURES COMMONLY USED AT THE INDUSTRIAL LEVEL WERE EVALUATED IN ORDER TO VALIDATE EXPERIMENTALLY THE PILOT SCALE PROCESS FOR ITS FUTURE INDUSTRIAL SCALING. THE QUALITY OF THE INPUT RADIATA PINE REFERS TO THE PRESENCE OF NATURAL DEFECTS OF WOOD, AS WELL AS THE AMOUNT OF JUVENILE WOOD. SELECTED THERMALLY MODIFIED SAMPLES WERE USED TO MEASURE SOME QUALITY MARKERS (PHYSICAL, MECHANICAL, OPTICAL) AND TO FIND THEIR CORRELATIONS DUE TO QUALITY OR TREATMENT, SO AS TO OBTAIN THE BEST CHARACTERISTICS OF THE HEAT-TREATED PRODUCTS. THE RESULTS INDICATED THAT THE QUALITY OF THE INPUT WOOD WAS ONLY RELEVANT TO THE MILD TREATMENT (190 °C), FINDING AN ACCEPTABLE CORRELATION BETWEEN THE WEIGHT LOSS AND THE QUALITY USED (FIRST QUALITY). AFTER BOTH TREATMENTS, THE ORDER OF ANISOTROPY WAS KEPT AND THE DIMENSIONAL CHANGES WERE SIGNIFICANTLY REDUCED; THUS, THE WEIGHT LOSS DURING TREATMENT DID NOT DRAMATICALLY AFFECT ITS ANATOMICAL STRUCTURE. CLUSTERING THE DATA BY STATISTICAL PROCEDURES WAS POSSIBLE TO OBSERVE THAT SAMPLES OF LOWER QUALITY WERE ORDERED ACCORDING TO THE TREATMENT TEMPERATURE, INDICATING A STRONG INFLUENCE OF THE TREATMENT ON THE PROPERTIES OBTAINED. THE MECHANICAL PROPERTIES REVEALED THAT UP TO 190 °C THE CHEMICAL CHANGES THAT OCCUR ON WOOD AFFECTED POSITIVELY THE VALUES (MOE INCREASED BY ABOUT 15?32% AND MOR SLIGHTLY DECREASED?

LABORATORY SCALE EXPERIMENTS ARE PERFORMED IN ORDER TO CHARACTERIZE THE ARTIFICIAL WOOD DRYING OF PINUS RADIATA AT CONVENTIONAL TEMPERATURES AND ACCELERATED TEMPERATURES. THE EXPERIMENTAL DATA ALLOW DETERMINING THE WOOD THERMAL CONDUCTIVITY THROUGH INVERSE METHODOLOGY. THE COMPARATIVE ANALYSIS SHOWS THAT THE IMPLEMENTATION OF THE DEVELOPED INVERSE METHODOLOGY IS CONSISTENT WITH INFORMATION AVAILABLE IN THE SPECIALIZED LITERATURE; WHICH MEANS INCREASED THERMAL CONDUCTIVITIES WITH INCREASED HUMIDITY AND TEMPERATURE, WHOSE VALUES OSCILLATE BETWEEN 0,34 AND 0,56 (W/M K) TO MOISTURE VARIATIONS BETWEEN 22% AND 64%; AND TEMPERATURES BETWEEN 70°C AND 90°C, RESPECTIVELY.

THE THERMAL MODIFICATION OF WOOD IS A POTENTIAL ALTERNATIVE METHOD FOR IMPROVING WOOD DIMENSIONAL STABILITY AND INCREASING THE RESISTANCE OF WOOD TO DECAY. HOWEVER, DURING THERMAL MODIFICATION, MORPHOLOGICAL CHANGES OCCUR WITHIN THE MICROSTRUCTURE OF THE CELL, AND THESE CONFER DIFFERENT PROPERTIES TO THE WOOD. THIS STUDY INVESTIGATED THE EFFECTS OF THE THERMAL MODIFICATION PROCESS ON THE MICROSTRUCTURE OF RADIATA PINE JUVENILE WOOD. THEREFORE, ANATOMICAL MEASUREMENTS WERE PERFORMED VIA OPTICAL MICROSCOPY IN SELECTED EARLYWOOD AND LATEWOOD SAMPLES AFTER EACH TREATMENT, AND THE RESULTS WERE COMPARED TO UNTREATED WOOD SAMPLES. IN THIS STUDY, TWO TEMPERATURES (190 °C AND 210 °C) WERE CONSIDERED FOR THE THERMAL MODIFICATION PROCESS. THE RESULTS SHOWED THAT THE LEVEL OF TEMPERATURE OF MODIFICATION AFFECTED TO MICROSTRUCTURE OF CELL WALL. THE CELL WALL THICKNESS DECREASED AS TREATMENT TEMPERATURE INCREASED, WHEREAS THE AVERAGE LUMEN DIAMETER INCREASED SLIGHTLY AS TEMPERATURE INCREASED. THERMALLY MODIFIED RADIATA PINE SHOWED SIGNS OF DAMAGE (CRACKS, BROKEN CELLS AND DEFORMATIONS IN THE WOOD CELL WALL). THE PROPORTION OF DESTROYED AREA INCREASED AS TEMPERATURE INCREASED, AND SIGNIFICANT DIFFERENCES WERE EVIDENT FOR THE THERMAL TREATMENT AT 210 °C.

IN THIS WORK THE TOTAL HEATING TIME WAS STUDIED USING RADIO FREQUENCY TO STERILIZE WOOD PACKAGING MATERIAL OF PINUS RADIATA, THROUGH THE CONDITIONS 56 ° C AND 60 ° C FOR 30 AND 1 MINUTES RESPECTIVELY, ACCORDING TO INTERNATIONAL PHYTOSANITARY NORMS. THE EXPERIMENTAL TESTS WERE CARRIED OUT IN A LABORATORY RADIOFREQUENCY EQUIPMENT OF 3 M3 CAPACITY. THE HEATING TIME WAS DETERMINED AND PREDICTION MODELS WERE DEVELOPED, DEPENDING ON THE THICKNESS, PLAQUE SEPARATION AND WOOD LOADING VOLUME, WITH CONFDENCE LEVELS ABOVE 90%. THE RESULTS SHOWED THAT THE TOTAL TIME OF RADIOFREQUENCY STERILIZATION WAS GREATER IN THE SURFACE OF THE PILE AND WERE STATISTICALLY SIMILAR UNDER BOTH TREATMENT CONDITIONS.

WOOD DRYING IS AN IMPORTANT PROCESS FOR ADDING VALUE AND MANUFACTURING INNOVATIVE PRODUCTS. EUCALYPTUS NITENS WOOD IS INHERENTLY DIFFICULT TO DRY BECAUSE OF ITS NATURAL PROPENSITY FOR CHECKING AS WELL AS COLLAPSE AND SHRINKAGE. LUMBER RECOVERY AFTER INDUSTRIAL DRYING OF EUCALYPTS IS ALSO VERY LOW. THIS STUDY MEASURED THE WOOD QUALITY OF E. NITENS JUVENILE WOOD (13 MM THICKNESS) AFTER RADIO-FREQUENCY VACUUM (RFV) DRYING AND WOOD DRIED IN A CONVENTIONAL KILN DRYER (KD). DRYING CYCLES WERE PERFORMED USING A RADIO FREQUENCY VACUUM DRYER WITH A 3 M3 OF CAPACITY AND CONVECTIVE KILN-DRYER EQUIPMENT WITH A 3.5 M3 OF CAPACITY. THE RESULTS SHOWED THAT THE DRYING TIME USING THE RADIO FREQUENCY VACUUM METHOD WAS REDUCED BY 47% WHEN COMPARED TO CONVENTIONAL KILN DRYING. THE SHRINKAGE WAS SIGNIFICANTLY LOWER IN THE RFV THAN IN THE CONVENTIONAL KD. THE VOLUMETRIC COLLAPSE DECREASED BY APPROXIMATELY 60% IN THE RFV DRYING. RFV DRYING OF E. NITENS JUVENILE WOOD IMPROVES THE WOOD QUALITY FOR SOLID WOOD PRODUCTS BECAUSE THE INTENSITY OF SURFACE CHECKING AND COLLAPSE ARE REDUCED.

RADIATA PINE WOOD PACKAGING NEEDS TO BE STERILIZED ACCORDING TO INTERNATIONAL PHYTOSANITARY STANDARDS. IN THIS WORK THE HEAT STERILIZATION TIME OF GREEN RADIATA PINE PACKAGING MATERIAL STACKED WITHOUT SEPARATORS WAS STUDIED ON AN INDUSTRIAL SCALE, CONSIDERING AS VARIABLE FACTORS THE STEAM TEMPERATURE (80, 90 AND 100) °C, THE THICKNESS OF THE WOOD (16, 38 AND 53) MM AND THE HEIGHT OF THE WOOD PILE (150, 200 AND 400) MM. THE PILOT EXPERIMENT WAS CONDUCTED IN A 40 M3 INDUSTRIAL OVEN. SUBSEQUENTLY THE EXPERIMENT WAS SCALED TO 100 M3OVENS. THE RESULTS SHOWED THAT THE HEAT STERILIZATION TIME IN THE ANALYZED TEMPERATURE RANGE DEPENDS SIGNIFI-CANTLY ON THE THICKNESS AND HEIGHT OF THE STACK. THE MINIMUM TIME TO OBTAIN HEAT STERILIZATION CONDITIONS OF RADIATA PINE PACKAGING MATERIAL VARIED FROM 123 MIN TO A MAXIMUM OF 2275 MIN

A TREATMENT IS PROPOSED TO SANITIZE WOOD FOR EXPORT PACKAGING USING RADIO FREQUENCY EQUIPMENT THAT IS CAPABLE OF TREATING WOOD. THIS WAS ACHIEVED BY OPTIMIZING THE SANITIZATION PROCESS AND DEVELOPING AN EQUATION TO PREDICT THE TOTAL SANITIZATION TIME. STATISTICAL ANALYSIS DETERMINED THAT THE SEPARATION OF PLATES AND THE POWER DENSITY OF THE EQUIPMENT SIGNIFICANTLY INFLUENCED THE DURATION OF A SANITIZATION PROCESS USING RADIO FREQUENCY HEATING, WHEREAS THE THICKNESS OF THE MATERIAL WAS NOT AS INFLUENTIAL FOR THE OVERALL PROCESS. FURTHERMORE, THE SANITIZATION PROCESS DID NOT INFLUENCE THE QUALITY OF THE WOOD; THEREFORE, THE PROPOSED SANITIZATION PROTOCOL PROVIDED A BALANCE BETWEEN DURATION AND THE QUALITY OF THE FINISHED RADIATA PINE PACKAGING MATERIAL.