Brzina dugotrajnoga higroskopskog debljinskog bubrenja kompozita od polipropilena i hidrotermički tretirane bukovine

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

Long-term water absorption behavior of thermoplastic composites produced with thermally treated wood

Wood plastic composites (WPCs) were produced from thermally treated beech (Fagus orientalis L.) wood and polypropylene (PP) polymer with coupling agent, by using injection molding. The wood chips were thermally treated for 30 or 120 min at three different temperatures (120 degrees C, 150 degrees C, or 180 degrees C) under saturated steam in a digester and then grounded (40-mesh size) by wood mill. Long-term water absorption kinetics of the composites were investigated with water immersion test. It was found that the water absorption decreased with increasing severity of the thermal-treatment and water immersion time as compared to the control composites. Furthermore, the composites produced with wood treated at 180 degrees C for 120 min exhibited the least water absorption. Microstructures of the composites were examined by SEM analysis to understand the mechanisms for the wood-plastic interaction which affected the water absorption. Further studies were conducted to model the water diffusion of the composites. Diffusion coefficient parameter in the models was obtained by fitting the model predictions with the experimental data. Water absorption of the studied composites was proved to follow the kinetics of a Fickian diffusion process. (C) 2016 Elsevier Ltd. All rights reserved

Mechanical Properties and Morphology of Wood Plastic Composites Produced with Thermally Treated Beech Wood

The effect of thermal-treatment severity of wood on the mechanical and morphological properties of wood plastic composites (WPCs) was investigated. Wood chips were first heat treated at 120, 150, or 180 ºC for 30 or 120 min under saturated steam in a digester. The composites were composed of thermally treated and untreated wood flour, polypropylene, and a coupling agent, produced by melt compounding and then injection molding. The thermal-treatment of the beech wood improved some mechanical properties of the WPCs, depending on the treatment-time and temperature. The SEM micrographs of the composites showed that the outer surface of the wood fiber was coated by a section of amorphous lignin. The SEM images showed that the WPCs produced from the wood treated at 150 ºC for 30 min had considerably fewer holes and many broken fiber ends embedded in the polymer matrix, indicating better compatibility between the wood flour and the polymer matrix. Based on the results of the mechanical testing of the WPCs, the optimum thermal-treatment for WPC production was 150 °C for 30 min