Study of autocorrelation function of polymer and polymer–nanocomposite solutions using dynamic light scattering method

Dynamic light scattering (DLS) of polymer and polymer–nanocomposite solutions has been performed to examine the effect in the morphology of polymer solution in presence of nanoparticles analyzing their correlation functions. The size of the nanoparticle was determined using UV–Vis absorption spectroscopy measurements. Analysis of the correlation functions of polymer solution shows existence of two modes, namely, fast and slow modes, along with the distinct values in their corresponding amplitudes and relaxation times. Interestingly, the fast mode of the solution was found to smear out, enhancing the slow mode when we grow nanoparticles into the polymer solution. Apart from the above study, the temperature variation study of both the solutions show that above and below room temperature, the polymer solution becomes more heterogeneous compared to the solution when nanoparticles are grown into it.     

Functional and reactive polymethacrylates suitable for preparation of peptide/protein–polymer conjugates

Three reactive polymers, poly(para-nitrophenoxycarbonyloxyethyl methacrylate-co-methyl methacrylate) P(p-NPCEMA-co-MMA) [rCoP1], poly(methyl methacrylate-co-butyl methacrylate-co-allyl methacrylate-co-phenoxycarbonyloxyethyl methacrylate) P(MMA-co-BMA-co-AMA-co-PCEMA) [rCoP2] and poly(methyl methacrylate-co-dimethylaminopropyl methacrylate-co-dodecyl methacrylate-co-phenoxycarbonyloxyethyl methacrylate) P(MMA-co-DMAPMA-co-DMA-co-PCEMA) [rCoP3], respectively, were prepared following two synthetic concepts. Following the first concept, p-NPCEMA and PCEMA were prepared starting with commercially available HEMA and were copolymerized via ATRP with MMA, BMA and AMA. According to the second concept phenoxycarbonyloxy decorated polymethacrylates were obtained via polymer analogous reaction of a HEMA containing functional polymethacrylate, P(MMA-co-DMAPMA-co-DMA-co-HEMA) [fCoP], obtained via a cascade reaction of enzymatic transacylation and free radical polymerization. The highly reactive poly(methacrylate)s and silk peptides, hen egg-white lysozyme and Candida antarctica lipase B were used for the preparation of protein/peptide-poly(methacrylate) bioconjugates.     

Development and characterization of a lignin–phenol–formaldehyde wood adhesive using coffee bean shell

In the present study, the possibility of development of a wood adhesive using coffee bean shell lignin (Cbsl) has been explored. Cbsl-modified phenolic adhesive has been prepared by replacing phenol with lignin at different weight percents. The optimization of weight percent lignin incorporation was carried out with respect to mechanical properties. It was found that up to 50 wt% of phenol could be replaced by Cbsl to give lignin–phenol–formaldehyde adhesive (LPF) with improved bond strength in comparison to control phenol–formaldehyde (CPF). Optimized LPF and CPF adhesives were characterized by IR, DSC and TGA. The IR spectrum of LPF showed structural similarity to CPF. Thermal stability of LPF adhesive was found to be lower as compared to that of CPF. DSC studies revealed a higher rate of curing in the LPF adhesive.     

Preparation and performance of lignin–phenol–formaldehyde adhesives

Steam explosion lignin phenol formaldehyde (SEL–PF) adhesives were prepared by ternary gradual copolymerization. The parameters for the phenolate of steam explosion lignin (SEL) and preparation of SEL–PF adhesives were optimized. Under the optimum phenolate conditions, the phenolic hydroxyl content of lignin increased by 130%, whilst the methoxyl content was reduced by 68%. The SEL–PF adhesives were used to prepare plywoods by hot-pressing. The pH value, viscosity, solid content, free phenol content and free formaldehyde content of SEL–PF adhesives were investigated. The bonding strengths of the plywoods glued with SEL–PF adhesives were determined. The maximum SEL replacement percentage of phenol reached 70 wt%, and the properties of adhesives and plywoods met the Chinese National Standard (GB/T 14732-2006) for first grade plywood.     

Preparation of highly phenol substituted bio-oil–phenol–formaldehyde adhesives with enhanced bonding performance using furfural as crosslinking agent

Highly phenol substituted bio-oil–phenol–formaldehyde (BPF) adhesives were prepared via the phenolization-copolymerization method, in which furfural was used as a novel crosslinking agent to improve the bonding performance. The effects of bio-oil percentage, furfural content, curing temperature, and pressure on the performance of BPF adhesives have been studied in detail. A BPF adhesive with 75% bio-oil percentage and 15% furfural loading (named 75BPF_15) was synthesized, which was cured at 180 °C and 4 MPa. Compared to the conventional phenol–formaldehyde adhesive, the wet tensile strength of 75BPF_15 adhesive reached 2.84 MPa, which was significantly higher than the 1.54 MPa of PF. A possible mechanism of BPF adhesives crosslinked with furfural is proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46995.     

Wireless actuation and control of ionic polymer–metal composite actuator using a microwave link

The ionic polymer–metal composite (IPMC), a type of electroactive polymer (EAP) actuator, has created a unique opportunity to design robots that mimic the motion of biological systems due to its soft structure and operation at a low voltage. Although this polymer actuator has strong potential for a next-generation artificial muscle actuator, it has been observed by many researchers that supplying actuation voltages in multiple locations is challenging. In robotic applications, a tethered operation is prohibited and the battery weight can be critical for actual implementation. In this research, the remote unit can provide necessary power and control signals to the target mobile robot units actuated by IPMCs. This research addresses a novel approach of using a wireless power link between the IPMC and a remote unit using microstrip patch antennas designed on the electrode surface of the IPMC for transmitting the power. Frequency modulation of the microwave is proposed to selectively actuate a particular portion of the IPMC where the matching patch antenna pattern is located. This approach can be especially useful for long-term operation of small-scale locomotion units and avoids problems caused by complex internal wiring often observed in various types of biologically inspired robots.     

Characterisation and modelling of CNT–epoxy and CNT–fibre–epoxy composites

Abstract

This research presents an experimental and theoretical investigation on the effects of carbon nanotube (CNT) integration within neat epoxy resin (nanocomposites) and a carbon fabric–epoxy composite (multiscale composites). An approach is presented for the prediction of mechanical properties of multiscale composites. This approach combines woven fibre micromechanics (MESOTEX) with the Mori-Tanaka model which was used for the prediction of mechanical properties of nanocomposites in this research. Nanocomposite and multiscale composite samples were manufactured using cast moulding, resin infusion, and hand lay-up process. The CNT concentrations in the composite samples were from 0 to 5 wt-%. The samples were characterised using tensile, shear and flexural tests. The discrepancy between the theoretical predictions and the experimental observations was hypothesised to be due to dispersion and bonding issues and SEM images are presented in support of the hypothesis.     

Fast pyrolysis of a SiC-based polymer precursor using a spark plasma sintering apparatus – Effects of heating methods and pyrolysis atmosphere

The effects of heating method on the pyrolysis behavior, crystallinity and ceramic yield of a SiC-based precursor-derived ceramic (PDC) were investigated using commercial allylhydrido-polycarbosilane (AHPCS) precursors, spark plasma sintering (SPS) apparatus and tube furnace. The heating rate of SPS was ten times faster than that of tube furnace. Consequently, the total time of precursor impregnation and pyrolysis (PIP) process decreased distinctly after several PIP cycles. PDCs fabricated by SPS had higher crystallinity than those prepared by tube furnace. The crystallinity of PDCs was 70.4 and 65.1 %, respectively, after the pyrolysis using SPS and tube furnace at 1400℃ for 1h. The highest crystallinity of 82.92 % was achieved after the pyrolysis at 1500℃ for 2h using SPS. The ceramic yield of the precursor was not strongly affected by the heating method. This study provides a promising method for the pyrolysis of ceramic precursors with short processing time and improved thermal stability.     

Optimization and simplification of polymer–fullerene solar cells through polymer and active layer design

Polymer–fullerene bulk heterojunction (BHJ) solar cells have consistently been at the forefront of the growing field of organic photovoltaics (OPV). The enduring vision of OPV is the promise of combining a simple, low-cost approach with an efficient, flexible, lightweight platform. While efficiencies have improved remarkably over the last decade through advances in device design, mechanistic understanding, and evolving chemical structural motifs, steps forward have often been tied to a loss of simplicity and a deviation from the central vision of OPV. Within the context of active layer optimization, our focus is to target high efficiency while maintaining simplicity in polymer design and active layer processing. To highlight this strategy, this feature article focuses on our work on random poly(3-hexylthiophene) (P3HT) analogs and their application in binary and ternary blend polymer–fullerene solar cells. These random conjugated polymers are conceptually based on combining simple monomers strategically to influence polymer properties as opposed to the synthesis of highly tailored and synthetically complex monomers. The ternary blend approach further exemplifies the focus on device simplicity by targeting efficiencies that are competitive with complex tandem solar cells, but within the confines of a single active-layer processing step. These research directions are described within the broader context of recent progress in the field of polymer–fullerene BHJ solar cells.     

Micro–macro characterisation of DGEBA-based epoxies as a preliminary to polymer interphase modelling

Reactive polymer adhesives in contact to substrates are known to form so-called interphases, a notion comprising the domain within which the polymer, compared to its bulk, exhibits structural inhomogeneities and gradients in material properties. Induced by the interface between substrate and polymer the formation of such interphases is usually ascribed to processes like segregation or phase separation of polymer components, selective adsorption, steric hindrance, orientation effects or curing shrinkage. Quantitative information on mechanical interphase properties is obtainable only by considerable efforts since interphases belong to the class of buried layers, i.e. they are located between bulk polymer and substrate, which impedes a majority of experimental techniques.Within this contribution, a two-component epoxy-based model polymer (DGEBA/DETA) is examined by methods on different scales and with respect to the effects that both the resin/hardener mixing ratio and the chemical structure of the hardener exert on the mechanical bulk properties. By means of these variations the above mentioned processes disturbing the polymer network formation in the vicinity of the substrate are emulated within the bulk. Macroscopic tension tests, nanoindentation and calorimetric methods (DSC) are applied to obtain relations between structural variations and material behaviour. Inversely identifying the governing parameters of suitable constitutive laws from experimental data will later conclude the first step towards a quantitative interphase model.It is demonstrated that modifications of the resin/hardener mixing ratio and the hardener formulation lead to variations in mechanical bulk properties which are quantitatively determinable by methods on different scales and do lie in ranges similar to those of property profiles that have been observed within interphases.In future work, the local mechanical behaviour of adhesive joints under load will then be investigated by a microscale videoextensometry. The resulting data will be compared to the structure–property relations from step one to conclude on the local polymer structure within the interphase.     

Mathematical modelling of a hydrocyclone for the down-hole oil–water separation (DOWS)

In this study, a mathematical model is developed to predict the efficiency of a down-hole oil–water separation hydrocyclone. In the proposed model, the separation efficiency is determined based on droplet trajectory of a single oil droplet through the continuous-phase. The droplet trajectory model is developed using a Lagrangian approach in which single droplets are traced in the continuous-phase. The droplet trajectory model uses the swirling flow of the continuous-phase to trace the oil droplets. By applying the droplet trajectory, a trial and error approach is used to determine the size of the oil droplet that reaches the reverse flow region, where they can be separated. The required input for the proposed model is hydrocyclone geometry, fluid properties, inlet droplet size distribution and operational conditions at the down hole. The model is capable of predicting the hydrocyclone hydrodynamic flow field, namely, the axial, tangential and radial velocity distributions of the continuous-phase. The model was then applied for some case studies from the field tested DOWS systems which exist in the literature. The results show that the proposed model can predict well the split ratio and separation efficiency of the hydrocyclone. Moreover, the results of the proposed model can be used as a preliminary evaluation for installing a down-hole oil–water separation hydrocyclone system in a producing well.     

Preparation and properties of nano ZnO toughed phenol–urea-formaldehyde foam

Urea formaldehyde (UF) and phenol formaldehyde (PF) foam possess outstanding flame-retardant properties, excellent insulation, and low thermal conductivity. These properties make them suitable for thermal insulation in buildings. However, the mechanical properties still need to be improved. In this study, orthogonal test was designed to optimize the level components of PF/UF composite foam first, then nano ZnO was added to the PF/UF composite foam to improve its toughness. The effects of nano ZnO on the morphology, apparent density, pulverization rate, thermal conductivity and thermal degradation property, flame retardancy, and mechanical properties of the ZnO/PF/UF nanocomposite foam were studied. The addition of nano ZnO improved the bending and compressive strength and decreased the pulverization rate of the composite foam significantly. The ZnO/PF/UF nanocomposite foam also presented better flame retardant properties than PF/UF composite foam. The largest oxygen index values of ZnO/PF/UF nanocomposite foam could reach 39.31%, while the thermal conductivity and the maximum rate of weight loss temperature were increased to 0.036 W/(m∙K) and 279°C, respectively. Moreover, ZnO/PF/UF nanocomposite foam showed low apparent density property (0.27 g/cm³).     

Preparation and controlled release of degradable polymeric ketoprofen–saccharide conjugates

A facile and efficient enzymatic and polymerization process was used to prepare polymeric prodrugs of ketoprofen with saccharide side chains. The chains included branches that included glucose, mannose, galactose, and lactose, and these were synthesized through free radical reaction. The prodrugs were characterized by FT-IR, NMR, and GPC and drug-loading capacity was influenced by varying the ratios of initiator and monomers (range 32.13 and 68.56% w/w). In vitro release characteristics of the polymeric drugs were systematically evaluated over the pH range 1.2–8.0 and the release profiles indicated that the hydrolytic nature of polymers were strongly depended on the variation in saccharide content, carbon chain length, and pH. The outcomes from this study demonstrate the importance of carbohydrate structures and how these are linked to drug release.     

Oxidative carbonylation of phenol to diphenyl carbonate catalyzed by Pd–pyridyl complexes tethered on polymer support

Various Pd–pyridyl complexes tethered on polystyrene were investigated as novel immobilized Pd catalysts for the direct synthesis of diphenyl carbonate (DPC) by oxidative carbonylation using phenol, carbon monoxide, and air. These Pd catalysts showed reasonably high efficiencies in the absence of ammonium halide. The best efficiencies were obtained by using Pd–biquinoline complex tethered on polystyrene 1, Pd–bipyridyl complex tethered on polystyrene 3, and Pd–methylpyridyl complex tethered on polystyrene 7 where TOF reached about 4 (mol-DPC/mol-Pd h), respectively. Their efficiencies were higher than those of the Pd complex catalyst tethered on conventional polymer support and PdBr₂ under similar conditions.     

Palygorskite and SnO2–TiO2 for the photodegradation of phenol

The photocatalytic removal of phenol was studied using palygorskite-SnO₂–TiO₂ composites (abbreviated as Paly-SnO₂–TiO₂) under ultraviolet radiation. The photocatalysts were prepared by attachment of SnO₂–TiO₂ oxides onto the surface of the palygorskite by in situ sol–gel technique. The products were characterized by XRD, TEM and BET measurements. SnO₂–TiO₂ nanoparticles, with an average diameter of about 10 nm, covered the surface of the palygorskite fibers without obvious aggregation. Compared with palygorskite-titania (Paly-TiO₂), palygorskite-tin dioxide (Paly-SnO₂), and Degussa P25, Paly-SnO₂–TiO₂ and SnO₂–TiO₂ exhibited much higher photocatalytic activity. The photodecomposition of phenol was as high as 99.8% within 1.5 h. The apparent rate constants (k_app) for Paly-SnO₂–TiO_2, TiO₂, and P25 were measured. Paly-SnO₂–TiO₂ showed the highest rate constant (0.03435 min^?1). The chemical oxygen demand (COD) of the phenol solution was reduced from 220.2 mg/L to 0.21 mg/L, indicating the almost complete decomposition of phenol. Reusability of the photocatalyst was proved.     

Novel dispersion analysis and selective quantification of particulate components in graphene nanoplatelets–polymer–polymer hybrid composites

Up until now, no standard procedure to analyze and quantify the dispersion of particles in the polymer matrix exists. From the conductive hybrid polymer–polymer–graphene nanoplatelets composites we developed, this article attempts to showcase methodologies to analyze and quantify particle with the use of scanning electron microscopy images and collection of the elemental maps of carbon, oxygen, and nitrogen by energy dispersive spectroscopy (EDS) analysis. Image analysis was performed on the resulting map to extract the area and location data of graphene particles by subtracting elemental maps. Shadowing or charging problem in the images acquired from EDS was overcome by the polished surface and analyzing a sample twice using a novel approach of 180° opposed. Merging the data from the two elemental maps, taken 180° opposed, can be an alternative to the use of polished samples. From these different dispersion analysis approaches, it was possible to quantify different particles and their effects on the properties of the composites.     

Synthesis of porous silicon nitride using silica/carbon composite derived from phenol–resorcinol–formaldehyde gel

Mesoporous silicon nitride (Si₃N₄), which is one of the most promising structural materials for applications in high-temperature filtration, was synthesized from the carbothermal reduction and nitridation of a pyrolyzed silica-containing phenol-resorcinol-formaldehyde (PRF) gel. The PRF gel was synthesized by combining sol–gel and polymerization of phenol, resorcinol and formaldehyde using sodium carbonate as a catalyst. Silica was incorporated into the gel by addition of 3-aminopropyl trimethoxysilane (APTMS) as a silica precursor. After aging and being freeze-dried, the silica/PRF composite was pyrolyzed under nitrogen gas to convert it into porous silica/carbon composite. The combination of phenol-formaldehyde (PF) and resorcinol-formaldehyde (RF) gels into PRF gel, allows further enhancement in porosity of the silica/carbon composite via pre-calcination in the range of 400–500 °C, since carbon derived from PF gel and that from RF gel have different thermal stability. The final product obtained after final calcination to remove residual carbon has a surface area as high as 194 m²/g, which is significantly much higher than the conventional Si₃N₄ granules. Specific surface area of the product is affected by molar ratio of phenol-to-resorcinol, molar ratio of silica-to-carbon, and the pre-calcination temperature.     

Structural and compositional characterization of 6H–SiC implanted with N+ and Al+ ions using optical methods

Using plane-view and cross-sectional Raman spectroscopy, polarized infra-red spectroscopy and photothermal spectroscopy, the structure, composition and internal stress of 6H–SiC crystal implanted sequentially with N⁺ and Al⁺ ions to form a (SiC)_1−x(AlN)_x solid solution were studied non-destructively and self-consistently. The optimum implantation temperature for the synthesis of a (SiC)_1−x(AlN)_x solid solution with a 6H structure was found to be 600 °C.     

Effect of ZrC content on the properties of biomorphic C–ZrC–SiC composites prepared using hybrid precursors of novel organometallic zirconium polymer and polycarbosilane

A novel organometallic zirconium polymer was synthesized through the copolycondensation using n-butyllithium, 1,4-diethynylbenzene, phenylacetylene and zirconium tetrachloride as raw materials. Then biomorphic C–ZrC–SiC composites were fabricated from corn stover templates by precursor infiltration and pyrolysis process using hybrid polymeric precursors containing the organometallic zirconium polymer and polycarbosilane. The microstructure, mechanical properties and oxidation resistance of the composites were investigated. With ZrC content increasing, the mechanical properties of the composites were enhanced due to dispersion strengthening and grain fining of the homogeneously dispersed ZrC nanoparticles. The oxidation behavior of C–SiC–ZrC indicated that the oxidation resistance of the composite was reduced at 1000 °C but improved at 1500 °C with the increase of ZrC content. The improved oxidation resistance was mainly attributed to a proper ZrC content, the formation of ZrSiO₄ layer on the surface of the composite, and its matrix microstructure characterized by a nano-sized dispersion of ZrC–SiC phases.