Teng-Chun Yang

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.

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.

Effects of a layered structure on the physicomechanical properties and extended creep behavior of bamboo-polypropylene composites (BPCs) determined by the stepped isostress method

Abstract A layered bamboo-plastic composite (BPC) consisting of bamboo (Phyllostachys makinoi) particles and polypropylene was investigated. The influence of the layering conditions, including the thickness and bamboo content in various layers, was the focus in terms of the physicomechanical and creep properties of the BPCs. The results showed that a three-layered BPC (BPC3L) with a 1:3:1 thickness ratio and with top/bottom layer containing 40% bamboo exhibited the best specific flexural properties. An accelerated creep test approach was applied, known as the short-term stepped isostress method (SSM), to predict the long-term creep behavior of BPC3L. The results indicated that the creep master curves, which are constructed from different SSM testing parameters, agree well with the long-term experimental creep data and that the creep resistance of homogeneous single-layered BPC was better than that of BPC3L.

Methodology of accelerated weathering test through physicochemical analysis for polymeric materials in building construction

Abstract Physicochemical analysis in the microscopic sense is a critical assessment of monitoring the polymeric materials under a weathering test, and it links the accelerated laboratory test with the outdoor performance results for a long-term durability. Here, by taking an experimented example for vinyl siding after an outdoor weathering test in Okinawa, Japan for 17 years and a QUV accelerated weathering test for 2880 hours, it was observed that there were entirely different results on the functional groups and the surface image with the atom concentration measured by the attenuated total reflectance Fourier transform infrared and scanning electron microscopy with energy dispersive spectroscopy, respectively. Furthermore, the optimal conditions of a specified accelerated weathering test based on a replication of the natural weathering characteristics are deliberated, thus correcting the deterioration factors configuration in consideration for the physicochemical degradation of a specific material. The aim of this study places an emphasis on the crucial points for improving the accelerated weathering test through a physicochemical analysis.

Improvement of Accelerated Weathering Test through Physicochemical Analysis for Polymeric Materials in Building Construction

In civil engineering, the long-term service life of buildings as environmental measures is one of important performances being comparable to structure and fire safety, and it is demanded to improve durability of materials in building construction. This improvement of material durability is highly associating with lifetime of building, and so as not to reach the limit state of building components. It is imperative to determine a specific means and method in order to identify the surrounding environment on the deteriorating effect for building components and materials, as well as predicting a process of degradation phenomena and the limit state of buildings. As part of building materials, polymeric materials become widespread in civil engineering because of taking advantage of excellent property, such as lightweight, high corrosion resistance, and good formability. However, we should look ahead the lifecycle cost in order to have effective application of this material, so it is necessary to understand the lifecycle of such material. In weathering, outdoor weathering test is the surest way to clarify exactly how a material, component, or products degrade by environmental stresses in an acceptable timeframe, but it usually takes few years to decades to obtain a useful or referable result. Meanwhile, accelerated weathering test methods have been proposed as a method to obtain the results in a short period of time than outdoor weathering test. However, the method of estimating a material durability in the actual environment from these obtained data has not yet been established.In this section, it would be showing some attentions for comparison of the results from outdoor and accelerated weathering test. Then the need for investigating weatherability of polymeric materials through physicochemical analysis are emphasized to improve the relevance and precision of durability under field and laboratory weathering test. Lastly, introducing the design of accelerated weathering method based on natural weathering characteristics.