Isolation and characterization of cellulose nanowhiskers from Acacia caesia plant

Acacia caesia (L.) Willd (soap bark) fiber is an abundant natural resource, that is rich in cellulose. The study reports the effective utilization of underutilized Acacia caesia fiber for the isolation of nanocellulose whiskers. The nanocellulose whiskers were isolated successfully from Acacia caesia fibers by following alkali, bleaching, and sulfuric acid treatment. The obtained nanocellulose whiskers were carefully investigated for its chemical composition, structure, morphology, crystallinity, and thermal stability. The chemical composition and Fourier transform infrared spectra of nanocellulose whiskers showed the elimination of the non-cellulosic parts present in the raw Acacia caesia fibers. The X-ray diffraction analysis showed an upsurge in the crystallinity of the cellulose fibers after the chemical treatments. The isolation of nanocellulose whiskers from Acacia caesia raw fiber was confirmed by electron microscopy analysis. The thermogravimetric analysis showed remarkably high char residue for the nanocellulose whiskers compared to raw fibers. Based on the properties of nanocellulose whiskers, it can be concluded that the nanocellulose whiskers produced from Acacia caesia raw fibers are potential reinforcing material for developing high-performance green composites.     

Influence of bismuth on microstructure,thermal properties,mechanical performance,and interfacial behavior of SAC305-xBi/Cu solder joints

This research sought to improve the properties of SAC305 solder joints by the addition of 1 and 2 wt.% Bi. The effects of bismuth doping on the microstructure, thermal properties, and mechanical performance of the SAC305-xBi/Cu solder joints were investigated. Bi-doping modified the microstructure of the solder joints by refining the primary β-Sn and eutectic phases. Bi-doping below 2 wt.% dissolved in the β-Sn matrix and formed a solid solution, whereas Bi additions equal to or greater than 2 wt.% formed Bi precipitates in the β-Sn matrix. Solid solution strengthening and precipitation strengthening mechanisms in the β-Sn matrix increased the ultimate tensile strength and microhardness of the alloy from 35.7 MPa and 12.6 HV to 55.3 MPa and 20.8 HV, respectively, but elongation decreased from 24.6% to 16.1%. The fracture surface of a solder joint containing 2 wt.% Bi was typical of a brittle failure rather than a ductile failure. The interfacial layer of all solder joints comprised two parallel IMC layers: a layer of Cu₆Sn₅ and a layer of Cu₃Sn. The interfacial layer was thinner and the shear strength was greater in SAC305-xBi/Cu joints than in SAC305/Cu solder joints. Therefore, small addition of Bi refined microstructure, reduced melting temperature and improved the mechanical performance of SAC305/Cu solder joints.     

Effect of modified layered silicates on the confined crystalline morphology and thermomechanical properties of poly(ethylene oxide) nanocomposites

In this work, poly(ethylene oxide) (PEO)/organoclay nanocomposites with three different types of nanoclays (Cloisite 30B, Somasif JAD400, and Somasif JAD230) were prepared by melt mixing with a laboratory kneader followed by compression molding. The nanocomposites were characterized by atomic force microscopy and scanning electron microscopy. Their crystallization behavior on a hot stage was investigated with polarized optical microscopy. The size and regularity of the spherulites of the PEO matrix were altered significantly by the incorporation of Cloisite 30B, but there was not as much variation with the other two clays. The dynamic viscoelastic behavior of the PEO/organoclay nanocomposites was assessed with a strain‐controlled parallel‐plate rheometer. The effects of clay modification on the thermomechanical and rheological properties were addressed. The reinforcing effect of the organoclay was determined with dynamic mechanical analysis and tensile testing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of surface treatment on properties of Cocos nucifera L. Var typica fiber reinforced polymer composites

Natural fibers are a powerful competitor in the polymer composite market due to their availability, sustainability, obtainability, cost, and biodegradability. The surface of natural fibers was changed to increase mechanical qualities, hydrophobicity, and bonding with polymer matrix. This study exposes the influence of several surface treatments of coconut tree peduncle fibers (CTPFs) on the thermomechanical and water absorption properties of CTPF-reinforced polymer composites. The CTPFs were treated with sodium hydroxide, benzoyl peroxide, potassium permanganate and stearic acid at a constant 40 wt% and individually reinforced in an unsaturated polyester resin matrix containing 60 wt% CTPFs. Chemically treated CTPFs improved reinforcement-matrix adhesion and enhanced composite mechanical characteristics. In addition, the scanning electron microscope fractographical study of stressed composite specimens shows improved reinforcement-matrix bonding. Moreover, the treated CTPFs have a higher cellulose wt%, which improves the composites crystalline nature, hydrophobicity and thermal stability. The potassium permanganate treated CTPF composite's maximum tensile strength of 128 MPa, flexural strength of 119 MPa, impact strength of 9.9 J/cm², hardness value of 99 HRRW and thermal stability up to 193°C make them appropriate for lightweight mobility and structural applications.     

Processing and characterization analysis of pyrolyzed oil rubber (from waste tires)‐epoxy polymer blend composite for lightweight structures and coatings applications

In this experimental investigation, the authors have fabricated and characterized composites made from pyrolysis oil rubber and epoxy resin. As the dumping of waste scrap tires poses a serious environmental threat, the pyrolysis oil rubber was extracted from these waste tires only. The prepared blend having pyrolysis oil with various weight percentages (wt%) was examined on the basis of various physical, microstructural, mechanical, and thermal tests. The microstructural tests (scanning electron microscopy and X‐ray diffraction) analysis complemented with the mechanical tests (tensile, compression, flexural, hardness, and impact) results and confirmed that the 4.4 wt% of pyrolysis oil in epoxy resin sample exhibited the best results in toughening of the polymer network. Furthermore, the thermal analysis (differential thermal analysis and thermogravimetric analysis), electrical conductivity, density, water absorption, gas chromatography–mass spectroscopy, and Fourier‐transform infrared tests for the composites were also performed. Low density and high tensile strength than neat epoxy resin makes this composite a potential candidate for fabricating lightweight structures and in polymer coatings for automotive industries. POLYM. ENG. SCI., 59:2041–2051, 2019. © 2019 Society of Plastics Engineers     

Antibacterial and thermomechanical properties of composites of polylactic acid modified with capsicum oleoresin-impregnated nanoporous silica

Biodegradable composite films of poly(lactic acid) (PLA) modified with varying amounts of capsicum oleoresin (CO)-impregnated nanoporous silica (SiCO) were prepared. The antimicrobial and thermomechanical properties of the PLA composites were carefully investigated. The Gram-positive pathogenic bacteria (Staphylococcus aureus and Bacillus) and the Gram-negative pathogenic bacteria (Escherichia coli and Salmonella enterica) tests established excellent antimicrobial properties of the composites even at small concentrations of SiCO. The microscopic (scanning electron micrograph) and spectroscopic (energy-dispersive X-ray) investigations manifested the uniformity of particle distribution. Although the addition of CO slightly decreased the thermal stability of the composite films, it marginally enhanced the mechanical properties and crystallinity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47825.     

Effects of antimony on the microstructure,thermal properties,mechanical performance,and interfacial behavior of Sn–0.7Cu–0.05Ni–xSb/Cu solder joints

Journal of Materials Science: Materials in Electronics - We investigated a new, lead-free solder alloy to replace traditional lead-based solder alloys. A Sn–0.7Cu–0.05Ni solder alloy...     

Mechanical and stress relaxation behavior of Santoprene® thermoplastic elastomer/boehmite alumina nanocomposites produced by water-mediated and direct melt compounding

Thermoplastic dynamic vulcanizate (TPV) was filled with synthetic boehmite alumina (BA) via water-mediated (WM) and direct melt compounding (DM) techniques. According to the WM an aqueous BA dispersion was injected into the molten TPV in a twin-screw extruder to prepare the related nanocomposite with 5 wt.% BA content. In DM the BA powder was mixed to the TPV granules in the hopper of the extruder. The dispersion of the BA was studied by atomic force microscopy (AFM), and discussed. The mechanical and thermo-mechanical properties of the composites were determined in uniaxial static tensile, dynamic-mechanical thermal analysis (DMTA), and short-time stress relaxation tests (performed at various temperatures). It was found that the WM technique yielded a finer BA dispersion in TPV than the DM one. Incorporation of BA increased the stiffness, elongation at break and relaxation modulus compared to the neat TPV. Effect of the BA incorporation route was most pronounced for the stress relaxation results. Master curves, displaying the relaxation modulus vs. time, were constructed by applying the time–temperature-superposition principle. It was established that the Williams–Landel–Ferry equation (WLF), and the generalized Maxwell model are fairly applicable to the stress relaxation results.     

Dynamic mechanical thermal analysis of all-PP composites based on β and α polymorphic forms

All polypropylene (all-PP) composites were manufactured by exploiting the polymorphic forms of PP, in which alpha (α)-PP tapes worked as reinforcement and beta (β)-PP served as matrix. The mechanical performance of the composite was investigated in a range of frequencies and temperatures using dynamic mechanical thermal analysis (DMTA). The volume fractions of matrix and reinforcement were estimated using optical microscope images. Both the DMTA and the static flexural bending tests revealed that the α-PP tapes act as an effective reinforcement for the β-PP matrix. Time–temperature superposition (TTS) was applied to estimate the stiffness of the composites as a function of frequency (f = 10⁻⁹...10²³) in the form of a master curve. The Williams–Landel–Ferry (WLF) model described properly change in the experimental shift factors used to create the storage modulus versus frequency master curve. The activation energies for the α and β relaxations were also calculated by using the Arrhenius equation.     

Comparative Evaluation of Hot-Air and Superheated-Steam Impinging Stream Drying as Novel Alternatives for Paddy Drying

An investigation was conducted on impinging stream drying of moist paddy using hot air and superheated steam as the drying media. Drying experiments were divided into two parts: namely, one-pass and two-pass drying. The volumetric water evaporation rate, volumetric heat transfer coefficient, and specific energy consumption of the drying system at various conditions were assessed; in the case of superheated-steam drying, the effect of steam recycle was also assessed. The quality of dried paddy was evaluated in terms of color, head rice yield, and degree of starch gelatinization. In the case of one-pass drying, an increase in the drying temperature led to a significant increase in the volumetric water evaporation rate and volumetric heat transfer coefficient. On the other hand, in the case of two-pass drying, an increase in the drying temperature led to a significant decrease in the volumetric heat transfer coefficient; the volumetric water evaporation rate was not significantly affected, however. The specific energy consumption decreased with an increase in the drying temperature. At the same temperature, using superheated steam as the drying medium led to lower specific energy consumption; higher level of steam recycle also led to more energy conservation. The color of the dried paddy was not affected by the change in the drying temperature; superheated-steam-dried paddy was redder and more yellow than the hot-air-dried paddy. An increase in the drying temperature led to decreased percentage of head rice yield. Superheated-steam drying helped enhance the level of starch gelatinization in comparison with hot-air drying at the same temperature. Nevertheless, drying at the highest tested temperature led to a lower level of starch gelatinization.