Ke-Chang Hung

Mechanical and interfacial properties of plastic composite panels made from esterified bamboo particles

In this study, different extents of acetylated and butyrylated bamboo particle/plastic composites (BPPC) were produced by the flat-platen pressing process. The effect of esterification on mechanical and interfacial properties of BPPC was evaluated by a universal testing machine, X-ray diffractometer (XRD), 13C CP/MAS nuclear magnetic resonance (NMR) spectrometer, and scanning electron microscope (SEM). The results showed that the internal bond (IB) and wood screw-holding strength of BPPC were significantly increased after acetylation, even though the weight gain of acetylated bamboo particles was only 2%. In addition, SEM micrographs revealed that acetylated bamboo particles were effectively trapped by the polymeric matrix on the IB-fractured surface of BPPC. These results indicate that the interfacial interaction between the bamboo particle and the polymeric matrix can be enhanced through acetylation.

Effects of polymeric matrix on accelerated UV weathering properties of wood-plastic composites

Abstract The purpose of this work is to compare the weathering properties of different types of wood-plastic composites (WPCs) based on high-density polyethylene (HDPE), recycled high-density polyethylene (rHDPE-I and rHDPE-II), low-density polyethylene (LDPE), polypropylene (PP), recycled polypropylene (rPP), polystyrene (PS), and recycled polystyrene (rPS). The modulus of rupture (MOR) and modulus of elasticity (MOE) of all WPCs decreased with increasing exposure time of weathering. Of these, the rHDPE-II-based composite exhibited the highest MOR and MOE retention ratios after 2000 h of accelerated ultraviolet (UV) weathering, while the PS-based WPC had the lowest values. In addition, the carbonyl index difference (CID) of various WPCs increased significantly as a function of exposure time. Among them, the PS-based WPCs exhibited the most severe degradation due to photo-oxidation on the surface, while the degradation of PE-based WPCs was the mildest. These results are consistent with the change in the surface cracking and flexural properties of the composites. The PS-based WPCs also exhibited higher moisture diffusion coefficients. The mechanical behavior of WPCs after weathering is influenced by a combination of factors, such as surface oxidation, morphology changes, and moisture absorption.

Comparison and Characterization of the Antioxidant Potential of 3 Wild Grapes-Vitis thunbergii, V. flexuosa, and V. kelungeusis

UNLABELLED This study considers a laboratory examination of the antioxidant performance of methanolic extracts from the leaves and stems of 3 common wild grapes (Vitis thunbergii, V. flexuosa, and V. kelungeusis) by various in vitro methods. It also seeks to identify the specific antioxidant constituent. Results revealed that, of these specimens, stem extracts of V. thunbergii exhibited good 1,1-diphenyl-2-picrylhydrazyl radical-scavenging and superoxide radical-scavenging performance and ferrous ion-chelating ability, as well as the highest total phenolic content (179.5 mg of GAE/g). The principal antioxidant, (+)-lyoniresinol-2a-O-β-D-glucopyranoside, was isolated from the stem extracts of V. thunbergii and identified. Removal of this compound from the extracts caused an approximate 2- to 5-fold decrease in antioxidant performance. This showed that (+)-lyoniresinol-2a-O-β-D-glucopyranoside is the primary antioxidant in wild grapes. Results also indicated that the antioxidant performance of (+)-lyoniresinol-2a-O-β-D-glucopyranoside was stronger than its lignan aglycone, (+)-lyoniresinol. PRACTICAL APPLICATION Of the 3 common wild grapes-Vitis thunbergii, V. flexuosa, and V. kelungeusis, the extracts or phytochemicals, derived from the V. thunbergii stems have excellent antioxidant properties, so they have great potential as a basis for natural health products that seek to prevent diseases caused by the overproduction of radicals.

Effects of Heat-Treated Wood Particles on the Physico-Mechanical Properties and Extended Creep Behavior of Wood/Recycled-HDPE Composites Using the Time–Temperature Superposition Principle

This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements of the flexural properties or the wood screw holding strength were observed, except for the internal bond strength. Additionally, creep tests were conducted at a series of elevated temperatures using the time–temperature superposition principle (TTSP), and the TTSP-predicted creep compliance curves fit well with the experimental data. The creep resistance values of composites with heat-treated wood particles were greater than those having untreated wood particles due to the hydrophobic character of the treated wood particles and improved interfacial compatibility between the wood particles and polymer matrix. At a reference temperature of 20 °C, the improvement of creep resistance (ICR) of composites with heat-treated wood particles reached approximately 30% over a 30-year period, and it increased significantly with increasing reference temperature.

Characterization of Wood-Plastic Composites Made with Different Lignocellulosic Materials that Vary in Their Morphology, Chemical Composition and Thermal Stability

In this study, four kinds of lignocellulosic fibers (LFs), namely, those from Chinese fir (Cunninghamia lanceolata), Taiwan red pine (Pinus taiwanensis), India-charcoal trema (Trema orientalis) and makino bamboo (Phyllostachys makinoi), were selected as reinforcements and incorporated into high-density polyethylene (HDPE) to manufacture wood-plastic composites (WPCs) by a flat platen pressing process. In addition to comparing the differences in the physico-mechanical properties of these composites, their chemical compositions were evaluated and their thermal decomposition kinetics were analyzed to investigate the effects of the lignocellulosic species on the properties of the WPCs. The results showed that the WPC made with Chinese fir displayed a typical M-shaped vertical density profile due to the high aspect ratio of its LFs, while a flat vertical density profile was observed for the WPCs made with other LFs. Thus, the WPC made with Chinese fir exhibited higher flexural properties and lower internal bond strength (IB) than other WPCs. In addition, the Taiwan red pine contained the lowest holocellulose content and the highest extractives and α-cellulose contents, which gave the resulting WPC lower water absorption and flexural properties. On the other hand, consistent with the flexural properties, the results of thermal decomposition kinetic analysis showed that the activation energy of the LFs at 10% of the conversion rate increased in the order of Taiwan red pine (146–161 kJ/mol), makino bamboo (158–175 kJ/mol), India-charcoal trema (185–194 kJ/mol) and Chinese fir (194–202 kJ/mol). These results indicate that the morphology, chemical composition and thermal stability of the LFs can have a substantial impact on the physico-mechanical properties of the resulting WPCs.

Characterization and Thermal Stability of Acetylated Slicewood Production by Alkali-Catalyzed Esterification

This study was compared and characterized two different alkali (potassium carbonate (PC) and potassium acetate (PA))-catalyzed acetylations of slicewood with vinyl acetate (VA) by a vapor phase reaction. The results revealed that the esterification reaction between VA and the hydroxyl groups of slicewood could be improved by using PC or PA as a catalyst. Additionally, a significant weight percent gain was obtained after VA acetylation with 5% of catalyst. Furthermore, the reactivity of the cellulose hydroxyl groups for VA acetylation was more pronounced at the C2 reactive site compared to acetylation with acetic anhydride. On the other hand, the apparent activation energy of thermal decomposition between 10% and 70% conversion is 174–183, 194–200, and 183–186 kJ/mol for unmodified slicewood and VA-acetylated slicewood with PC and PA, respectively. Accordingly, the thermal stability of the slicewood could be effectively enhanced by VA acetylation, especially for using the PC as a catalyst.

Comparison of physical and thermal properties of various wood-inorganic composites (WICs) derived by the sol-gel process

Abstract The physical properties and thermal decomposition kinetics of wood-inorganic composites (WICs) were in focus, which were prepared from methyltriethoxysilane (MTEOS), tetraethoxysilane (TEOS) and titanium (IV) isopropoxide (TTIP) by the sol-gel process. The hydrophobicity and dimensional stability of the composites were better than those of unmodified wood (Wcontr), but the performance of SiO2-based WICs (WICSiO2) was the best. The SEM-EDX micrographs show that silica is only distributed within the cell wall of the WICSiO2. By contrast, titania was deposited principally in the cell lumens of the WICTiO2. The thermal decomposition kinetic experiments show that the average apparent activation energies with conversion rates between 10% and 70% were 156–168 (Wcontr), 178–180 (WICMTEOS), 198–214 (WICTEOS) and 199–204 (WICTTIP) kJ mol−1 at the impregnation level of 20% weight gain. The reaction order values calculated based on the Avrami theory were 0.51–0.57, 0.39–0.51, 0.36–0.47 and 0.28–0.51 in the same order of species indicated above. Accordingly, the dimensional and thermal stability of the wood could be enhanced effectively by the sol-gel process with silicon- and titanium-based alkoxides.

The influence of bamboo fiber content on the non-isothermal crystallization kinetics of bamboo fiber-reinforced polypropylene composites (BPCs)

Abstract Bamboo fiber (BF)-reinforced polypropylene (PP) composites (BPCs) have been investigated and it was shown by differential scanning calorimetry (DSC) that BF is a nucleation agent and accelerates the crystallization rate of the PP matrix. Numerical analyses according to Avrami, Avrami-Ozawa, and Friedman described well the nucleation mechanism, the crystallization rate and the activation energy for the non-isothermal crystallization behavior of BPCs, respectively. The Avrami approach indicated that BF as a reinforcement significantly changed the crystal growth mechanism of PP matrix during the cooling process. Based on the Avrami-Ozawa method, a lower cooling rate can achieve a certain relative crystallinity degree within a time period. According to the Friedman method, the activation energies of BPCs were lower than that of neat PP below a relative crystallinity of 35%, when the BF content was more than 60%.

The Effect of Maleated Polypropylene on the Non-Isothermal Crystallization Kinetics of Wood Fiber-Reinforced Polypropylene Composites

The influence of maleated polypropylene (MAPP) on the non-isothermal crystallization behavior of wood fiber (WF)-reinforced PP composites (WPCs) was investigated by a differential scanning calorimeter (DSC). The results showed that MAPP as a nucleation agent accelerated the crystallization rate of the PP matrix in WPC under the cooling process. The corresponding crystallization kinetics and activation energy were further analyzed using the Avrami method, Avrami–Ozawa method, Kissinger method, and Friedman method. The results demonstrated that MAPP significantly changed the crystal growth mechanism of the PP matrix to heterogeneous nucleation for acicular and tabular crystal growth during the annealing step. A remarkably lower cooling rate can achieve a certain relative crystallinity degree at the unit crystallization time for WPC with 3 wt % MAPP (WPCM3). Similarly, the lowest crystallization activation energy was observed for the WPCM3 among all WPCs by the Kissinger method. Furthermore, based on the Friedman method, the addition of MAPP easily caused the PP matrix to crystallize in the WPC at the initial stage of relative crystallinity.

Effect of SiO2 Content on the Extended Creep Behavior of SiO2-Based Wood-Inorganic Composites Derived via the Sol–Gel Process Using the Stepped Isostress Method

In this study, methyltrimethoxysilane (MTMOS) was used as a reagent to prepare SiO2-based wood-inorganic composites (WICSiO2) via the sol-gel process, and subsequently, the extended creep behaviors of WICSiO2 with weight percent gains (WPGs) of 10%, 20%, and 30% were estimated using the stepped isostress method (SSM). The results revealed that the density of all samples ranged from 426 to 513 kg/m3, and no significant difference in the modulus of elasticity (MOE) was noted among all of the samples (10.5–10.7 GPa). However, the MOR of WICSiO2 with a WPG of 20% (102 MPa) was significantly greater than that of untreated wood (87 MPa). In addition, according to the result using the SSM, the SSM-predicted creep master curve fitted well with the experimental data for the untreated wood and WICSiO2. This result demonstrated that the SSM could be a useful method to evaluate long-term creep behaviors of wood and WICSiO2. Furthermore, the activation volume (V*) of the specimens was calculated from the linear slope of Eyring plots, and the resulting V* of all of the WICSiO2 (0.754–0.842 nm3) was lower than that of untreated wood (0.856 nm3). On the other hand, the modulus reduction of untreated wood showed 39%, 45%, 48%, and 51% at 5, 15, 30, and 50 years, respectively. In contrast, the modulus reduction of the WICSiO2 with a WPG of 10% decreased to 25%, 31%, 35%, and 38% at 5, 15, 30, and 50 years, respectively. Similar trends were also observed for other WICSiO2 with different WPGs. Of these, the WICSiO2 with a WPG of 20% exhibited the lowest reduction in time-dependent modulus (31%) over a 50-year period. Accordingly, the creep resistance of the wood could be effectively enhanced under the MTMOS treatment.