Flexural and creep strengthening for wood/PVC composite members using flat bar strips

This paper presents the flexural and creep performances of the strengthened wood/poly(vinyl chloride) (WPVC) composite members by using various types of flat bar strips adhered to the tension side. The WPVC composite member used was produced by an industrial-scale twin-screw extruder using the weight ratio of the wood to PVC compound of 1:1. High carbon steel (HCS) flat bar was selected a suitable material for the strengthening of WPVC composite members because of its high tensile stress, thin and light weight. For tension failure control, the flexural properties of strengthened WPVC composite member were improved with thickness and number of HCS strip used. By using one strip of HCS with 0.5 mm thickness adhered in tension side of WPVC composite member, the ultimate loads increased significantly up to 64% and 101% under flat-wise and edge-wise loading directions, respectively. Moreover, the strengthening of WPVC by using the HCS flat bar could reduce significantly the creep behavior, especially in edge-wise direction. Due to the same sustained load, the creep displacements of the strengthening WPVC composite members reduced significantly for 48% under flat-wise direction, and 11% under edge-wise loading direction. The creep displacement per sustained load and fraction deflection was found to reduce significantly by the HCS strengthening method.     

Physicochemical Properties of Sweet Potato Flour and Starch as Affected by Blanching and Processing

The effects of blanching on physicochemical properties of flours and starches prepared from two varieties of sweet potatoes (Mun‐Kai and Negro) were studied and compared. The pasting temperature and peak viscosity of starches, respectively, were 74 and 80 °C and 381 and 433 RVU. The pasting temperature (74.0‐94.8 °C) of flours was greater than that of starch, depending on the variety and blanching process. However, the peak viscosity (ca. 103‐120 RVU) of flours was lower than that of the corresponding starches. Partial gelatinization of starch granules was observed as a result of a 1‐min blanching. Composition of starch and flour was found to affect swelling power and solubility. The starch content of starches, flours from unblanched sweet potato and flours from 1‐min blanched sweet potatoes were 97; 66.3 and 74.9; as well as 36.6 and 40.4%, respectively. Amylose content of flours and starches varied from 17.2‐20.8%.     

Effects of cross‐section design and loading direction on the creep and fatigue properties of wood/PVC composite beams

The creep and fatigue properties of two wood/poly(vinyl chloride) (WPVC) composite beams were studied under flexural and cyclic deformations. The effects of cross‐section design and load direction were the main interests. The weight ratio of the wood and PVC compound used was 1:1, and the composites were produced by using an industrial‐scale twin‐screw extruder. In creep testing, the changes in WPVC beam displacement for the edgewise and flatwise directions increased with time. The WPVC composite with a greater size (thickness) and number of cores had the higher creep resistance. Testing a WPVC composite in the flatwise direction gave less time‐dependence than testing in the edgewise direction. The recommended applied loads for optimum creep resistance of the WPVC specimens were found to be 20 and 30% of the ultimate load to failure, depending on the size and number of cores for the cross‐section used. In fatigue testing, the number of cycles to failure for both WPVC composite specimens tested in the flatwise direction was greater than that for testing in the edgewise direction. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Mechanical and morphological properties for sandwich composites of wood/PVC and glass fiber/PVC layers

This work manufactured sandwich composites from glass fiber/poly(vinyl chloride) (GF/PVC) and wood/PVC layers, and their mechanical and morphological properties of the composites in three GF orientation angles were assessed. The effects of K value (or viscosity index) of PVC and Dioctyl phthalate (DOP) loading were of our interests. The GF/PVC was used as core layer whereas wood/PVC was the cover layers. The experimental results indicated that PVC with low K value was recommended for the GF/PVC core layer for fabrication of GF/WPVC sandwich composites. The improvement of PVC diffusion at the interface between the GF and the PVC core layer was obtained when using PVC with K value of 58. This was because it could prevent de‐lamination between composite layers which would lead to higher mechanical properties of the sandwich composites, except for the tensile modulus. The sandwich composites with 0° GF orientation possessed relatively much higher mechanical properties as compared with those with 45° and 90° GF orientations, especially for the impact strength. Low mechanical properties of the sandwich composites with 45° and 90° GF orientation angles could be overcome by incorporation of DOP plasticizer into the GF/PVC core layer with the recommended DOP loadings of 5–10 parts per hundred by weight of PVC components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of UV weathering and a CeO2‐based coating layer on the mechanical and structural changes of wood/PVC composites

Composite samples (WPVCs) of poly(vinyl chloride) (PVC) and wood flour were prepared in the PVC:wood weight ratio of 1:1, and the mechanical and structural changes of the composites were assessed in terms of UV aging time and condensation temperature. Acrylic coating containing cerium dioxide as a UV absorber was used for moderation of the mechanical and structural changes of PVC in the WPVC composites. The experimental results indicated that the tensile and flexural properties of the composites monotonically decreased when the aging time was increased, the effect being more pronounced at high condensation temperatures. It was observed that the polyene and yellowness indexes of the WPVC composites increased with UV aging time. The hydrophilicity of the WPVC was quantified by contact angle results and found to increase with increasing UV aging because of hydrogen bonding between ? OH groups on the wood surfaces and water molecules. The acrylic coating containing CeO₂ proposed in this work was sufficiently effective for maintaining the levels of hydrophilicity and mechanical properties of the WPVC composites. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Isoflavone content in soy germ flours prepared from two drying methods

Isoflavone glucosides and aglucons in various soybean varieties (Chiang Mai‐60, S.J.‐5, Chiang Mai‐2, Srisumrong‐1, and Nakhonsawan‐1) harvested from dry vs. rainy seasons were quantified. Isoflavone contents of all soy germs ranged from 16.5 to 30.6 μmol g^?1. Regardless of varieties, isoflavone contents in germ of seeds from dry season were higher (P < 0.05) than those from rainy season. The Chiang Mai‐60 germ, having the highest isoflavone content (30.6 μmol g^?1), was selected for germ flour production. Freeze‐dried germ flour contained higher isoflavone aglucons (17.72 μmol g^?1 daidzein; 6.48 mg g^?1 glycitein; 4.28 μmol g^?1 genistein) than those (15.07; 5.59; 3.41) of drum‐dried germ flour. However, isoflavone glucoside contents in freeze‐dried germ flour (3.27 μmol g^?1 daidzin; 1.86 μmol g^?1 glycitin; 1.41 μmol g^?1 genistin) were lower than those (5.22; 3.15; 1.89) of drum‐dried germ flour. Total isoflavone contents of drum‐dried and freeze‐dried germ flours were comparable (34.32 vs. 35.02 μmol g^?1) but more than that (30.16 μmol g^?1) of unprocessed germ flour.     

Trimethylsilyl‐substituted triazole‐based ligand for copper‐mediated single‐electron transfer living radical polymerization of methyl methacrylate

The tripodal ‘click’ compound tris(4‐trimethylsilylmethyl‐1,2,3‐triazolylmethyl)amine (TTTA) was prepared and investigated as a ligand for copper‐catalysed single‐electron transfer living radical polymerization of methyl methacrylate (MMA). Bulk polymerizations catalysed by Cu⁰/CuBr₂/TTTA with a molar ratio of [MMA]₀/[ethyl‐2‐bromoisobutyrate]₀/[CuBr₂]₀/[TTTA]₀ = 200:2:1:1 and a 1.0 × 1.0 cm² Cu⁰ sheet were fast and well controlled (76% conversion with M_w/M_n = 1.19 after 3.5 h). Greater amounts of added air generally gave slower polymerizations although M_w/M_n remained low (<1.3) even when the polymerization was carried out under aerobic conditions. Decreasing initial concentrations of the Cu⁰/CuBr₂/TTTA catalyst system or polymerization temperatures also resulted in slower polymerizations and yielded polymers with broader dispersity. Kinetic studies in the temperature range 40–90 °C revealed an apparent activation energy of 22.6 kJ mol^?1. © 2014 Society of Chemical Industry