Thermal and mechanical behavior of natural rubber latex‐silica aerogel film

A major problem in most natural rubber latex (NRL) commonly encountered like other polymer is susceptibility to mechanical properties and thermal degradation; particularly in thin film due to the presence of double bonds in the main chain. Therefore, it is desirable to seek for ways of improving these properties. Silica aerogel is a material with extraordinary properties was believed to have potential enhance properties in NRL films because of its high specific surface area. Therefore, based on the unique character of silica aerogel, NRL‐silica aerogel film was developed by latex compounding and dry coagulant dipping to form thin film where silica aerogel acts as filler. Silica aerogel, synthesized from rice husk was dispersed in a ball‐mill using distilled water for NRL compounding. Results indicate that increasing silica aerogel loading enhances the mechanical properties of the NRL‐silica aerogel film. Effects of postvulcanization processes were also investigated, whereby the best reinforcing effect was obtained at 4 phr silica aerogel loading with leaching postvulcanization condition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

We report on a recycling project in which α-Al₂O₃ was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H₂SO₄ solution to form an Al₂(SO₄)₃ solution. The Al₂(SO₄)₃ salt was contained in a white semi-liquid solution with excess H₂SO₄; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al₂(SO₄)₃·18H₂O. The Al₂(SO₄)₃·18H₂O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C/min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al₂(SO₄)₃·18H₂O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al₂O₃ at high temperatures. The X-ray diffraction results indicated that the α-Al₂O₃ phase was realized when the calcination temperature was at 1200 °C or higher.     

Preparation and characterization study on maleic acid cross-linked poly(vinyl alcohol)/chitin/nanocellulose composites

In the quest on improving composite formulations for environmental sustainability, maleic acid (MA) cross-linked poly(vinyl alcohol) (PVA)-α-chitin composites reinforced by oil palm empty fruit bunch fibers (OPEFB)-derived nanocellulose crystals (NCC) had been successfully prepared. Based on the Fourier transform infrared (FTIR) spectroscopic analysis, it was proven that molecular interactions of the cross-linker to the polymeric networks was through conjugated ester linkage. Differential scanning calorimetry (DSC) showed that the influence of MA was minimal toward crystallization in the PVA/chitin/NCC composite. Maximum tensile strength, elongation at break and Young's modulus of the respective PVA/chitin/NCC composites were achieved at different content of MA, dependent on the PVA/chitin mass ratio. Among all compositions, a maximum Young's modulus was achieved at 30 wt% MA loading in PVA/chitin-30/NCC, amounting to 2,413.81 ± 167.36 MPa. Moreover, the mechanical properties and selected physicochemical properties (swelling, gel content, and contact angle) of the PVA/chitin/NCC composites could be tailored by varying the chitin content (10–30 wt%) and MA content (10–50 wt% based on total mass of composite). In brief, this chemically cross-linked PVA-based biocomposites formulated with sustainable resources exhibited tunable physicochemical and mechanical properties.     

Photoelectrochemical cells based on a novel porphyrin containing light harvesting conducting copolymer

A copolymer of anti-5,15-bis([2′,2″:5″,2″′-terthiophene]-3″-yl)-2,8,12,18-tetra-n-butyl-3,7,13,17-tetramethylporphyrin (1) with 2,2′:5′2″-terthiophene (2) was successfully electrosynthesised and was then characterised by cyclic voltammetry, UV-Vis spectroscopy, four-point probe conductivity measurement, and scanning electron microscopy. This novel light harvesting conducting copolymer was then incorporated into photoelectrochemical cells using a liquid electrolyte and tested for photovoltaic responses. The effect of zinc incorporation into the porphyrin cavity was also investigated, and the best device generated an open circuit voltage of 185 mV, short circuit current of 881 μA cm⁻² with a fill factor of 0.36 and energy conversion efficiency of 0.12% under a halogen white light intensity of 500 W m⁻².     

Machining and Ceramic/Ceramic Joining to Form Internal Mesoscale Channels

Ceramics and semiconducting materials with internal channels are crucial in a variety of diverse technologies such as "lab on a chip," fuel cell applications, and cooling of microelectronics. In this paper, techniques for fabricating internal channels in brittle materials first are reviewed. Then, the mechanical machining of surface channels in 99.99% pure alumina partially sintered at 600°C and 700°C is discussed. After machining, the partially sintered alumina is sintered to a density of about 97% of theoretical and then joined to 96% pure alumina to convert the surface channels into internal channels.     

Mild functionalization of carbon nanotubes filled epoxy composites: Effect on electromagnetic interferences shielding effectiveness

The effect of nitric acid mild functionalized multiwalled carbon nanotubes (MWCNTs) on electromagnetic interference (EMI) shielding effectiveness (SE) of epoxy composites was examined. MWCNTs were oxidized by concentrated nitric acid under reflux conditions, with different reaction times. The dispersion of MWCNTs after functionalization was improved due to the presence of oxygen functional groups on the nanotubes surface. Functionalization at 2 h exhibits the highest EMI SE and electrical conductivity of MWCNTs filled epoxy composites. However, EMI shielding performance of MWCNTs filled epoxy composite declined when the functionalization reaction time was prolonged. This was due to extensive damage on the MWCNT structure, as verified by a Raman spectroscope. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42557.     

The studies of physical properties of dimeric fatty acid-modified thiodiphenyl epoxy resins

A thermally stable thiodiphenyl epoxy resin was modified with a dimeric fatty acid at an epoxy resin:fatty acid molar ratio of 4:1. The thermal and mechanical properties of the modified epoxy resin were studied by preparing an epoxy composition with an amine curing agent and a catalyst, followed by curing at 170 °C to produce a neat plastic epoxy resin. The tensile and impact strengths of the resin indicated improved flexibility and toughness compared to other epoxy resins. Enhanced toughness was confirmed by the increased lap shear strength in single lap joints prepared with steel substrates attached by the resin.     

Effects of LiF on the Structure and Properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 Lead‐Free Piezoelectric Ceramics

Preparation of Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) lead‐free piezoelectric ceramics with different amounts of LiF (BCZT‐xLiF) was done, and the effects of the LiF doping on the phase transition behavior and the electrical properties of the resulting ceramic were investigated. The experimental results showed that the polymorphic rhombohedral‐tetragonal phase transition temperature was found shifted toward room temperature with the Li doping. The study showed that BCZT lead‐free piezoelectric ceramic with improved performance properties at room temperature can be achieved by shifting the polymorphic phase transition point nearer room temperature through the addition of LiF.