Artículos científicos

LA ESPÉCIE PINUS RADIATA ES LA MÁS IMPORTANTE PARA LA INDUSTRIA MADERERA CHILENA POR SU COMERCIALIZACIÓN EN LA FORMA DE MADERA ASERRADA, DE MADERA TRANSFORMADA EN DIVERSOS TIPOS DE TABLEROS (PANELES DE PARTÍCULAS Y DE FIBRAS, MDF Y OSB) O DE MADERA LAMINADA ENCOLADA. DURANTE EL PROCESAMIENTO MECÁNICO DEL P. RADIATA SON GENERADOS VARIOS TIPOS DE RESIDUOS QUE NO HAN SIDO EXPLOTADOS HASTA AHORA DE UNA FORMA RACIONAL. CONSTITUYÓ EL OBJETIVO DE ESTE TRABAJO INVESTIGAR EL COMPORTAMIENTO MECÁNICO DE COMPUESTOS DE DOS TIPOS DE PARTÍCULAS DE P. RADIATA (ASERRÍN Y VIRUTAS) CON UN CEMENTO DE FRAGUADO RÁPIDO. VARIOS TRATAMIENTOS FISICO-QUIMICOS FUERAN APLICADOS A LAS PARTÍCULAS VEGETALES. EN UNA SEGUNDA INVESTIGACIÓN TAMBIÉN SE EVALUÓ EL EFECTO DE DOS OTROS TIPOS DE CEMENTO (SIDERÚRGICO Y PUZOLÁNICO) EN LA RESISTENCIA DEL COMPUESTO. DE ENTRE TODOS LOS TRATAMIENTOS APLICADOS A LOS RESIDUOS VEGETALES, LOS RESULTADOS OBTENIDOS INDICARAN EL EFECTO MÁS EFECTIVO DEL CLORURO DE CALCIO (AL 2% CON RELACIÓN A LA MASA DE CEMENTO) PARA LOS TRES TIPOS DE CEMENTOS. CONFIRMANDO LOS DATOS DISPONIBLES EN LA LITERATURA, EL CEMENTO DE FRAGUADO RÁPIDO FUE MÁS EFECTIVO EN NEUTRALIZAR LA ACCIÓN DE LAS SUSTANCIA INHIBITORIAS DE LA MADERA QUE LOS CEMENTOS SIDERÚRGICO Y PUZOLÁNICO.

THIS WORK ANALYZES THE IMPACT OF RADIATA PINE (PINUS RADIATA D. DON) JUVENILE WOOD ON THE PHYSICAL AND MECHANICAL PROPERTIES OF ORIENTED STRANDBOARDS (OSB). RADIATA PINE LOGS WERE OBTAINED FROM 10 TREES OF A 26-YEAR OLD MANAGED STAND LOCATED IN THE 8TH REGION OF CHILE. THE EXPERIMENTAL DESIGN CONSIDERED THE PROPORTION OF JUVENILE WOOD AND STRAND ORIENTATION AS INDEPENDENT VARIABLES. OSB PANELS OF 0.4 M×0.4 M×12 MM WERE PRODUCED AND TESTED. THE RESULTS SHOW THAT THE JUVENILE WOOD PROPORTION HAS A SIGNIFICANT IMPACT ON THE PHYSICAL AND MECHANICAL PROPERTIES OF OSB. STRANDS ORIENTATION HAD A SIGNIFICANT IMPACT ON ALL THE PROPERTIES STUDIED WITH THE EXCEPTION OF THE MODULUS OF ELASTICITY IN BENDING. HOWEVER, THIS IMPACT WAS SMALL IN ALL CASES AND WOULD NOT CHANGE PANEL GRADE WITH THE EXCEPTION OF LINEAR EXPANSION. IN THIS CASE, PANELS MADE FROM TANGENTIAL STRANDS SHOWED A HIGHER LINEAR EXPANSION. ACCORDING TO THESE RESULTS, RADIATA PINE JUVENILE WOOD CAN BE USED FOR THE MANUFACTURING OF OSB UP TO A PROPORTION OF 70% OF THE OVEN-DRY WOOD WEIGHT WITHOUT SIGNIFICANT LOSSES OF THE PHYSICAL AND MECHANICAL PROPERTIES IF THE JUVENILE WOOD STRANDS ARE LOCATED IN THE SURFACE LAYERS.

INTRODUCTION: THE USE OF WOOD-PLASTIC COMPOSITES (WPCS) HAS BEEN LIMITED DUE TO THEIR LOW IMPACT STRENGTH AND HIGH DENSITY COMPARED TO NATURAL WOOD. OBJECTIVE: TO CHARACTERIZE THE CELLULAR MORPHOLOGY AND DENSITY OF WPCS PREPARED WITH VIRGIN AND RECYCLED POLYETHYLENE, AND PINUS RADIATA WOOD. MATERIALS AND METHODS: THE POLYMER AND THE FOAMED WPCS WERE MANUFACTURED BY AN EXTRUSION PROCESS. THE VIRGIN AND RECYCLED HIGH-DENSITY POLYETHYLENE WAS MIXED SEPARATELY WITH P. RADIATA WOOD. THE PLASTIC/WOOD RATIOS WERE 80/20 AND 70/30, WITH AN ENDOTHERMIC FOAMING AGENT (HYDROCEROL 1700 AT 1 AND 3%), A COUPLING AGENT (LICOCENE 4351), AND A LUBRICATING AGENT (LICOLUB H12) ADDED. RESULTS AND DISCUSSION: THE DENSITY OF VIRGIN POLYMER, WITH 1 AND 3% FOAMING AGENT, WAS REDUCED BY 39 AND 20%, RESPECTIVELY, BUT IN THE RECYCLED POLYMER THE REDUCTION WAS 18 AND 23%, RESPECTIVELY. IN THE FOAMED WPCS, THE REDUCTION WAS LESS THAN 10%. THE FOAMED COMPOSITES HAD SMALLER BUBBLE DIAMETER AND HIGHER CELL DENSITY. THE VOID FRACTION WAS HIGHER IN THE VIRGIN POLYMER AT 3% FOAMING. CONCLUSION: THE USE OF A FOAMING AGENT GAVE BETTER PHYSICAL PROPERTIES TO THE COMPOSITES

THE PRESENT STUDY EXAMINES THE SUITABILITY OF PARTICLEBOARD MADE FROM GROUND MACADAMIA NUT SHELLS BONDED WITH CASTOR OIL DERIVED RESIN AS AN ENVIRONMENTALLY SUSTAINABLE SUBSTITUTE FOR CONVENTIONAL WOOD FIBER/UREA FORMALDEHYDE PARTICLEBOARDS. THE PROPERTIES OF THE MACADAMIA SHELL CASTOR OIL RESIN PARTICLEBOARD WERE COMPARED WITH THOSE OF A WOOD FIBER/CASTOR OIL RESIN PARTICLEBOARD AND A CONVENTIONAL WOOD FIBER/UREA FORMALDEHYDE PARTICLEBOARD. THE DENSITY OF THE MACADAMIA SHELL PARTICLEBOARD WAS 43% HIGHER THAN THAT OF ITS WOOD FIBER COUNTERPART, IN KEEPING WITH THE HIGHER DENSITY OF THE MACADAMIA SHELLS. WATER ABSORPTION AND WATER-INDUCED SWELLING WERE MUCH LOWER IN THE MACADAMIA SHELL PARTICLEBOARD, BEING ONLY ONE QUARTER OF THE VALUE OBTAINED FOR THE WOOD FIBER PARTICLEBOARD. THIS IS CONSISTENT WITH THE LOWER MOISTURE ABSORPTION REPORTED PREVIOUSLY FOR MACADAMIA SHELLS. THE INTERNAL BOND STRENGTH WAS SIMILAR FOR THE MACADAMIA SHELL AND WOOD FIBER PARTICLEBOARDS BONDED WITH CASTOR OIL BASED POLYURETHANE. THE MODULUS OF RUPTURE AND MODULUS OF ELASTICITY WERE HOWEVER ABOUT 50% LOWER FOR THE MACADAMIA SHELL PARTICLEBOARD THAN FOR ITS WOOD FIBER COUNTERPART. THIS IS CONSIDERED TO BE DUE, AT LEAST IN PART, TO THE LOWER CELLULOSE CONTENT OF MACADAMIA SHELLS.............

THE OBJECTIVE OF THE PRESENT STUDY WAS TO OBSERVE THE MORPHOLOGY AND CHARACTERIZE THE MECHANICAL PROPERTIES OF WOOD PLASTIC COMPOSITE FOAMS. RECYCLED HIGH DENSITY POLYETHYLENE WAS MIXED WITH PINUS RADIATA D. DON (RADIATA PINE) WOOD FIBER OF 60 MESH. THE FIBER CONCENTRATIONS WERE 15 AND 25% BY WEIGHT. THE COMPOUNDS WERE FOAMED WITH A CHEMICAL AGENT ACA (AZODICABONAMIDE) AND MAPE (EPOLENE E-20) WAS USED AS A COUPLING AGENT. THE COMPOSITES WERE OBTAINED BY TWIN? SCREW EXTRUSION. THE RESULTS SHOWED THAT THE COUPLING AGENT HAD A POSITIVE EFFECT ON THE ADHESION OF THE RECYCLED POLYMER AND WOOD FIBER. THE DENSITY OF THE COMPOUNDS DECREASED WITH BLOWING AGENT AND THE MECHANICAL PROPERTIES OF HARDNESS, IMPACT, MODULUS OF ELASTICITY IN BENDING AND TENSION WERE HIGHER FOR UNFOAMED COMPOSITES. IT WAS CONCLUDED THAT INCREASING THE CONCENTRATION OF FIBER INCREASES THE MECHANICAL PROPERTIES WITH THE EXCEPTION OF IMPACT RESISTANCE OF THE COMPOUNDS THAT BY INCORPORATING THE BLOWING AGENT DECREASED SLIGHTLY.

USING NANOINDENTATIONS AND ULTRASTRUCTURE ANALYSIS, WE DEVELOPED A METHODOLOGY TO EXPLORE FACTORS THAT MAY CONTRIBUTE TO FAILURES IN EUCALYPTUS NITENS (DEANE ET MAIDEN) DUE TO GROWTH STRESSES. TWO TYPES OF WOOD WERE ANALYZED; NORMAL WOOD AND WOOD WITH MESO-CRACKS. FACTORS CONTRIBUTING TO CRACKING INCLUDED THE VESSEL FREQUENCY AND MECHANICAL PROPERTIES OF THE S2 LAYER MEASURED WITH NANOINDENTATIONS. MICRO AND MESOCRACKS PROPAGATED THROUGHOUT THE MIDDLE LAMELLA AND S1 LAYER DUE TO AN INCREASED STRESS CONCENTRATION THAT WAS MAINLY

IN THIS RESEARCH, THE USE OF PEACH PITS IN POLYPROPYLENE-BASED COMPOSITES HAS BEEN INVESTIGATED. SPECIMENS MANUFACTURED WITH 50% AND 60% PEACH PITS WERE EVALUATED AND COMPARED WITH A CONTROL SAMPLE MANUFACTURED WITH 60% RADIATA PINE WOOD AND POLYPROPYLENE. BOTH COMPOSITES FILLED WITH PEACH PITS PRESENTED IMPROVED PHYSICAL PROPERTIES, AND HIGHER POROSITY THAN RADIATA PINE WOOD-BASED COMPOSITES. IN ADDITION, THE PEACH PITS-BASED COMPOSITES SHOWED LOWER MECHANICAL PROPERTIES THAN THOSE MADE FROM PINE PARTICLES. THIS DIFFERENCE INCREASED WHEN ADDING HIGHER AMOUNTS OF PEACH PITS TO THE COMPOSITES. THE LOWER MECHANICAL PROPERTIES WERE ATTRIBUTED TO THE HIGHER AMOUNT OF EXTRACTIVES OF THE PEACH PITS COMPARED WITH PINEWOOD.

NOWADAYS, THERE IS GREAT INTEREST IN DEVELOPING ADHESIVES THAT DO NOT GENERATE FORMALDEHYDE EMISSIONS. THE OBJECTIVE OF THIS WORK WAS TO PREPARE ADHESIVES BASED ON YEAST PROTEIN EXTRACT FROM RHODOTORULA RUBRA (RR) TO MAKE PARTICLEBOARDS (PBS). THE ADHESIVES WERE CHARACTERIZED, AND THE PHYSICAL AND MECHANICAL PROPERTIES OF THE PBS WERE EVALUATED. THE RESULTS WERE COMPARED WITH THOSE OBTAINED USING A COMMERCIAL UREA-FORMALDEHYDE ADHESIVE (UF). ADHESIVES VISCOSITY VARIED FROM 420 TO 600 CP, WITH PH RANGING FROM 4.35 TO 4.73, AND SOLID CONTENT OF AROUND 50%. THE UF HAD A VISCOSITY OF 305 CP, PH OF 7.53 AND SOLID CONTENT OF AROUND 65%. DYNAMIC MECHANICAL ANALYSIS SHOWED THAT THE WOOD-ADHESIVE USING PROTEIN EXTRACT RR WITH REINFORCING AGENT GAVE A GOOD PERFORMANCE AND STIFFNESS, COMPARABLE TO THAT USING UF. THE INTERNAL BOND STRENGTH VALUES OF PBS VARIED FROM 0.36 TO 0.46 N/MM(2), WHILE SWELLING THICKNESS REACHED VALUES OF 24 AND 38%, RESPECTIVELY. DENSITY VALUES OF THE PBS FLUCTUATED BETWEEN 682 AND 693 KG/M(3). THE FORMALDEHYDE EMISSION OF THE PBS MANUFACTURED WITH RR EXTRACT BASED ADHESIVE HAD VALUES BETWEEN 0.2 AND 0.3 MG/100 G, WHILE FORMALDEHYDE EMISSION FOR UF PARTICLEBOARD WAS 6.8 MG/100 G. PROPERTIES OF THE PB MADE OF RR BASED ADHESIVES PRESENTED SIMILAR PROPERTIES TO PARTICLEBOARD MANUFACTURED WITH UF, BUT WITH LOWER LEVEL OF FORMALDEHYDE EMISSIONS. THE RESULTS FROM THIS RESEARCH VALIDATE THE MANUFACTURE OF PARTICLEBOARDS WITH RHODOTORULA RUBRA YEAST PROTEIN EXTRACT BASED ADHESIVES. THESE PBS MAY HAVE THE SAME APPLICATIONS AS THE TRADITIONAL PBS, WITH THE ADVANTAGE OF BEING ABLE TO FULFILL THE HIGH STANDARDS OF FORMALDEHYDE EMISSION DEMANDED BY THE SUSTAINABLE MARKET.

IT WAS STUDIED THE VARIABILITY IN MORPHOLOGICAL, PHYSICAL AND THERMAL PROPERTIES OF FIBER BARK OF EUCALYPTUS NITENS (DEANE & MAIDEN) COMING FROM TWENTY FOUR TREES, TWO SITES AND SIX FAMILIES; USING TECHNIQUES SUCH AS CONVENTIONAL LIGHT MICROSCOPY, ELECTRON MICROSCOPY (SEM) AND THERMO-GRAVIMETRIC ANALYSIS (TGA). SUCH PROPERTIES ARE RELEVANT FOR A LIGNOCELLULOSIC FIBER TO HAVE A POSSIBLE INDUSTRIAL APPLICATION AS REINFORCEMENT MATERIAL IN A THERMOPLASTIC MATRIX. SIGNIFICANT STATISTICAL DIFFERENCES WERE DETECTED IN THE FIBER PROPERTIES BY ANALYZING THE SITE OF ORIGIN OF THE SAMPLES, FAMILY AND STEM HEIGHT. STANDING OUT IN THE RESULTS OF PHYSICAL PROPERTIES, THE AVERAGE THICKNESS OF THE BARK LAYER (4.4 MM), ITS SPECIFIC GRAVITY (0.757), ITS MORPHOLOGICAL PROPERTIES SUCH AS LENGTH/DIAMETER OF FIBER (LF/DF= 69.14) AND FIBER PRESENCE (45%) IN THIS MATERIAL. THE THERMAL STABILITY OF THIS NATURAL FIBER TO 200ºC AND LOW MELTING TEMPERATURE OF THERMOPLASTICS SUCH AS HIGH DENSITY POLYETHYLENE (HDPE); INDICATE THAT THE BARK FIBERS OF THIS SPECIES ARE A GOOD OPTION TO APPLY AS A REINFORCEMENT MATERIAL IN THERMOPLASTICS MATRICES.

A PRELIMINARY INVESTIGATION WAS MADE OF WOOD ADHESIVES BASED ON RHODOTORULA RUBRA YEAST PROTEIN EXTRACT REINFORCED WITH RESORCINOL AND GLYOXAL. ADHESIVES WERE PREPARED, CHARACTERIZED AND EVALUATED BY FT-IR AND DMA. THE SHEAR STRENGTH OF ADHESIVE BONDS, INCLUDING DRY AND WET STRENGTH, WAS ALSO EVALUATED. FT-IR SPECTRA OF ADHESIVES WITH REINFORCING AGENTS HAVE FUNCTIONAL GROUPS WHICH INCREASE THE REACTIVITY OF THE ADHESIVES. DMA RESULTS SHOWED THAT ADHESIVE WITH REINFORCING AGENTS HAD GOOD PERFORMANCE, COMPARABLE TO UF. THE SHEAR STRENGTH OF THE ADHESIVE UNDER HUMID AND DRY CONDITIONS INCREASED AND WAS SATISFACTORY. RESULTS INDICATED THAT YEAST PROTEIN EXTRACTS OF RHODOTORULA RUBRA REINFORCED WITH RESORCINOL AND GLYOXAL MAY BE USED IN THE WOOD ADHESIVES INDUSTRY.