Reinforcement effect of poly (methyl methacrylate)-<Emphasis Type="Italic">g</Emphasis>-cellulose nanofibers on LDPE/thermoplastic starch composites: preparation and characterization

The effect of cellulose nanofibers (CNFs) and poly [methyl methacrylate (MMA)]-grafted cellulose nanofibers (CNF-g-PMMA) on mechanical properties and degradability of a 75/25 low density polyethylene/thermoplastic starch (LDPE/TPS) blend was investigated. Graft copolymerization on CNFs was performed in an aqueous suspension by free radical polymerization using MMA as an acrylic monomer. In addition, a LDPE/TPS blend was reinforced by different amounts of CNFs (1–5 wt%) and CNF-g-PMMA (1–7 wt%) using a twin-screw extruder. A 61% grafting of PMMA on the surface of CNFs was demonstrated by gravimetric analysis. Moreover, after modification the X-ray photoelectron spectroscopy analysis showed a 20% increase of carbon atoms on the surface of CNFs and a 22.6% decrease in the oxygen content of its surface. The mechanical properties of the CNFs-modified composites were significantly improved compared to the unmodified nanocomposites. The highest tensile strength and Young’s modulus were obtained for the composites reinforced by 3 and 7 wt% CNF-g-PMMA, respectively. The degradability of cellulose nanocomposites was studied by water absorption and soil burial tests. Surface modification of CNFs lowered water absorption, and soil burial test of the LDPE/TPS blend showed improvement in biodegradability by addition of CNF-g-PMMA.     

A multidisciplinary approach to understanding of structure–property correlations in polyamide‐layered silicate nanocomposites: Expectations and challenges

Layered silicate‐incorporated polyamide 6 (PA6) nanocomposites were studied to undertake correlations between morphological, rheological, permeability, and mechanical characteristics. The microstructure of nanocomposite specimens was seen through X‐ray diffraction, atomic force microscopy, and transmission electron microscopy measurements. In addition, impact, tensile, and permeability data were analyzed combining the theoretical and experimental analyses to draw a convincing conclusion on the state of exfoliation and intercalation of layered silicates throughout the PA6 matrix. The results provided support for the fact that introduction of silicate nanofiller brings about some advantages like higher impact and modulus, at the same time some drawbacks arising from the improper dispersion of nanoplatelets. It was also revealed that microscopic studies do not necessarily agree with each other regarding filler dispersion state. The correlations between microstructure and experimental data from mechanical and permeability tests were checked by some well‐established theoretical models. The trends in the test results were somewhat dependent on the state of filler dispersion. The role of the crystalline areas in achieving higher permeability resistance was also discussed, in a short review, to be comprehensively discussed in a future work. J. VINYL ADDIT. TECHNOL., 23:35–44, 2017. © 2015 Society of Plastics Engineers     

Enhancement of the Power Conversion Efficiency in Organic Photovoltaics by Unveiling the Appropriate Polymer Backbone Enlargement Approach

Optoelectronic properties, supramolecular assemblies, and morphology variation of polymeric semiconductors are governed by six fundamental chemical features. These features are molecular weight, bond length alternation (BLA), planarity, aromatic resonance energy, substituents, and intermolecular interactions. Of these features the specific role of BLA in determining the performance of a polymeric semiconductor in practical technological applications is so far unknown. This study investigates this question and reports the novel finding that the optoelectronic, microscopic (supramolecular packing), and macroscopic (morphology variation and device performance) properties of model semiconducting polymers depend on the conjugated polymer backbone enlargement, which is directly related to the BLA. Extensive studies are performed in both single‐component polymer films and their blends with fullerene derivatives. Understanding the specific structure‐properties relations will lead to significant advancement in the area of organic electronics, since it will set new design rules toward further optimization of polymer chemical structures to enhance the device performances.     

Multi-Hop WiMAX Networks: A New Opportunistic Algorithm Using AMC and PUSC Mode for Different Mobility Users

Resource allocation algorithms play the main role in provisioning high throughput in broad band wireless communications. The previous studies in WiMAX networks have considered either AMC or PUSC techniques for the resource allocation algorithms. In this way, AMC based algorithms have presented high throughput for low speed users. Conversely, PUSC based algorithms have not been affected by users’ speed, whilst the throughput is low. To date, the importance of presenting proportional fair and maintaining the network throughput for the users with different speeds has not been acknowledged yet. This paper presents a novel opportunistic algorithm which is suitable for the users with different mobility speeds. The new algorithm uses two modes of AMC and PUSC simultaneously. The simulation results reveal that in comparison to similar algorithms, the proposed algorithm presents more proportional fair throughput when there are both high and low speed users.     

Evaluation of bonding effectiveness of a self-etch and an etch-and-rinse adhesive resin to un-treated and Er:Yag laser treated dentin using mini-interfacial fracture toughness test

The aim of current study was to assess interfacial bonding effectiveness of self-etch and etch-and-rinse dental adhesives to untreated and Er:YAG laser-treated dentine using mini-interfacial fracture toughness (mini-iFT) test. 32 selected non-carious third molars were divided into two groups: untreated and Er:YAG laser treated. The laser-treated specimens were subjected to Er:YAG laser with energy density of 25.82?J/cm². Both groups were further assigned to two groups based on adhesive systems: self-etch and etch-and-rinse. The teeth were sectioned perpendicular to the adhesive/dentine interface to obtain 1.5?×?2?mm wide longitudinal rectangular sections. A single notch then was prepared at the adhesive-dentine interface. The mini-iFT test was done via a 4-point bend testing until failure and the KIC was calculated. All specimens were observed using a, scanning electron microscope (SEM). The data were analysed using two-way analysis of variance (ANOVA) at a significant level of 0.05. Weibull parameters including Weibull modulus and characteristic strength also were calculated for each experimental group. Two-way ANOVA showed both variables (the type of adhesive system and laser treatment) significantly influenced the mini-iFT values of specimens (p?≤?0.001). The self-etch and laser-treated group showed lower mini-iFT than the etch-and-rinse and untreated samples. SEM observations revealed that the fracture region was located at the adhesive-dentine interface in most of the specimens. The Er:YAG laser treatment may adversely affects the bonding effectiveness of the dentine/adhesive interface. The mini-iFT method can be used as a discriminative and valid method for the evaluation of bonding effectiveness at the adhesive-dentine interface.