Antimicrobial properties of copper plasma-modified polyethylene

Copper plasma immersion ion implantation is utilized to produce an antibacterial surface on polyethylene. XPS analysis of the plasma-treated materials reveals that a relatively large amount of copper, about 11% relative to carbon, is implanted into the near surface region. At the same time, about 3% copper is found to be also deposited on the surface. The implanted copper is observed to have the zero valence state indicating that the implanted Cu does not bind chemically with the atoms in the polymer. On the other hand, the copper atoms close to the surface are found to have the divalent state due to surface oxidation. Formation of CC bonds is also observed due to dehydrogenation following copper plasma implantation. Based on the results of atomic force microscopy and contact angle measurements, the surface hydrophilicity and roughness are not significantly altered. Our antibacterial experiments indicate that the copper implanted polyethylene exhibits excellent antibacterial effects against Escherichia coli and Staphylococcus aureus, and the effectiveness is 96.2% and 86.1%, respectively.     

New model phthalonitrile resin system based on self-promoted curing reaction for exploring the mechanism of radical promoted-polymerization effect

The reaction mechanism and product properties of radical promoted-polymerization effect of phthalonitrile (PN) were further studied in this article. Different from the previous blending model system, this work provided a structurally symmetrical self-promoted PN model compound [di-imide PN model monomer (DAIM-PN)], which was more conductive to study the polymerization mechanism. Combination of “in situ” infrared, proton nuclear magnetic resonance, and matrix-assisted laser desorption/ionization time of flight mass spectrometry offered a clearer picture of polymerization mechanism. The results indicated that DAIM-PN formed isoindoline and its cyclized tetramer of phthalocyanine selectively during the curing process. This work also demonstrated that the aliphatic chain participated in the reaction of nitrile group and provided more evidence for the reaction site (secondary carbon). Besides, high performance polymers with good processing properties, excellent thermal stability (overall char yield >74% at 800 °C, N₂), and heat resistance (T_g > 470 °C) were obtained by blending and copolymerizing DAIM-PN with 1,3-bis(3,4-dicyanophenoxy)benzene. The effectiveness and application potential of the reaction mechanism were confirmed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48134.     

Curing kinetics of bio‐based epoxy resin based on epoxidized soybean oil and green curing agent

New thermoset with a high bio‐based content was synthesized by curing epoxidized soybean oil (ESO) with a green curing agent maleopimaric acid catalyzed by 2‐ethly‐4‐methylimidazole. Non‐isothermal differential scanning calorimetry and a relatively new integral isoconversional method were used to analyze the curing kinetic behaviors and determine the activation energy (E_a). The two‐parameter ?esták–Berggren autocatalytic model was applied in the mathematical modeling to obtain the reaction orders and the pro‐exponential factor. For anhydride/epoxy group molar ratio equal to 0.7, E_a decreased from 82.70 to 80.17 kJ/mol when increasing the amount of catalyst from 0.5 to 1.5 phr toward ESO. The reaction orders m and n were 0.4148 and 1.109, respectively. The predicted non‐isothermal curing rates of ?esták–Berggren model matched perfectly with the experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 63: 147–153, 2017     

Effect of molecular weight of curing agents on properties of nanocomposites based on epoxy resin and organoclay with reactive modifier

Nanocomposites of epoxy resin and clay modified with half neutralized salt of Jeffamine D400 were prepared by curing separately with three polyetheramines curing agents of different molecular weights and reactivity. The molecular weight of curing agents and their structural similarity with modifier played an important role in deciding the curing behavior, thermomechanical, and morphological properties of epoxy/clay nanocomposites. Morphological analysis carried out by X‐ray diffraction (XRD) and transmission electron microscope (TEM) clearly show that the dispersion of clay layers in epoxy matrix decreases with decreasing molecular weight of the curing agents. Curing study done by using temperature modulated differential scanning calorimetry (MDSC) demonstrates that extragallery reaction rate increases with decreasing molecular weight of curing agents. Dynamic mechanical analysis (DMA) of epoxy/3 wt % modified clay composite prepared by curing with curing agent of higher molecular weight shows around 270% improvement in storage modulus (glassy) as compared with its neat epoxy network. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44595.     

Plasticizing effect of biodegradable dipropylene glycol bibenzoate and epoxidized linseed oil on diglycidyl ether of bisphenol A based epoxy resin

Major limitation for use of epoxy thermosets in engineering applications is its sudden brittle failure. In the present study dipropylene glycol dibenzoate (DPGDB) based plasticizer is used to modify diglycidyl ether of bisphenol A (DEGEBA) based epoxy resin system via simple blending technique. Bio-based epoxidized linseed oil was also used to modify epoxy resin system and compared with DPGDB modified resin. For DPGDB modified resin storage modulus and loss modulus of the epoxy system modified with 10% plasticizer increased by 7.54% and 12.24%, respectively. The primary mechanism responsible for such behavior is improved crosslinking density. With 5% plasticizer loading, flexural strength increased by 21%. There was an improvement of 312.74% in strain at failure for 10% plasticizer loading, while preserving its mechanical strength. It was found that DPGDB based modification was better than epoxidized linseed oil modification.     

Synthesis of a self‐emulsifiable waterborne epoxy curing agent based on glycidyl tertiary carboxylic ester and its cure characteristics

A novel self‐emulsifiable waterborne amine‐terminated curing agent for epoxy resin based on glycidyl tertiary carboxylic ester (GTCE) was synthesized through three steps of addition reaction, capping reaction, and salification reaction of triethylene tetramine (TETA) and liquid epoxy resin (E‐44). The curing agent with good emulsifying and curing properties was gradually obtained under condition of the molar ratio of TETA: E‐44 as 2.2: 1 at 65 °C for 4 h, 100% primary amine capped with GTCE at 70 °C for 3 h, and 20% salifiable rate with glacial acetic acid. The curing agent was characterized by Fourier transform‐infrared spectroscopy (FT‐IR). The curing behavior of the E‐44/GTCE‐TETA‐E‐44 system was studied with differential scanning calorimetry (DSC) and FT‐IR. Results showed that the optimal mass ratio for E‐44/GTCE‐TETA‐E‐44 system was 3 to 1, and the curing agent showed a relatively lower curing temperature. The cured film prepared by the self‐emulsifiable curing agent and epoxy resin under the optimal mass ratio displayed good thermal property, hardness, toughness, adhesion, and corrosion resistance. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44246.     

Dynamic mechanical investigations of the effects of water sorption and physical ageing on an epoxy resin system

After immersion (3 months) in distilled water, the epoxy-amine (diglycidyl ether of Bisphenol A-4,4′-methylene bis[3-chloro-2,6-diethylaniline], DGEBA-MCDEA) samples were mounted on the dynamic mechanical analyser where the thermal ageing treatment was performed. The influence of both hydrothermal and physical ageing on the viscoelastic properties of DGEBA-MCDEA network was investigated.Three relaxational processes were evidenced on the mechanical spectra (at 1 Hz) of the samples: the main relaxation (α) at higher temperatures, the secondary relaxation (β) at lower temperatures, and the intermediate ω-relaxation between 300 and 350 K.The β-relaxation mode was found bimodal, mainly affected by the water sorption, and unconcerned by the structural recovery following the thermal ageing treatment. On the opposite, the viscoelastic characteristics of the ω-relaxation were significantly affected by each step of both hydrothermal and thermal ageing treatments.     

Development of rubber pressure molding technique using butyl rubber to fabricate fiber reinforced plastic components based on glass fiber and epoxy resin

A rubber pressure molding (RPM) technique is developed to prepare fiber reinforced plastic components (FRP) using glass fiber and epoxy resin. The technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. A split steel die and rubber punch were designed and fabricated to prepare the FRP components. The same split die was also used to cast the rubber punch. Butyl rubber was used to prepare a rubber punch in this investigation. Burn test, coin test, scanning electron microscopy and mechanical tests like interlaminar fracture toughness, interlaminar shear test, tension test, etc were carried out to know the fiber content, void content, presence of delamination, bonding between fiber and resin, microstructure, and mechanical properties of the composite materials. These properties were also compared with FRP components made by the conventional technique to evaluate its performance in the structural applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1095–1102, 2006     

Synthesis and effects of MDT silicone resin on PMPS‐based ablative composites

A novel methylphenyl silicone resin, with M, D, and T units, was synthesized by cohydrolysis and cocondensation method from dimethyldimethoxysilane (Me₂Si(OMe)₂), phenyltrimethoxysilane (PhSi(OMe)₃), hexamethyldisiloxane, and 1,3‐divinyl‐1,1,3,3‐tetramethyldisiloxane in toluene/water mixture catalyzed by hydrochloric acid and trifluoromethanesulfonic acid. The vinyl end‐capped MDT silicone resins were chosen for reinforcement filler to enhance the mechanical properties of silicone‐based ablative composites. The effects of resins with various R/Si ratios, vinyl content, and loadings on mechanical properties of PMPS rubbers were investigated. It was revealed that on the premise of good fluidity and processing performance, MDT resin showed excellent reinforcing effect and thermal stability compared with silica. MDT reinforced ablative composite showed satisfactory mechanical and antiablative properties. The linear ablation rate was 0.01 mm/s, which maybe associated with high yield of charred residue in thermogravimetric analysis results. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41571.     

Investigation of rheological,mechanical, and thermal properties of nanocomposites based on nitrile rubber-phenolic resin reinforced with nanographene

In this study, nanocomposites of acrylonitrile butadiene rubber (NBR)/phenolic resin/graphene nanoparticles (GNPs) were prepared using a two-roll mill. According to the results, the addition of GNPs increased the scorch time, vulcanization time, and viscosity of the blends. By adding phenolic resin and in the presence of a higher percentage of acrylonitrile, the modulus and tensile strength increased and the elongation at break decreased. The mechanical properties of the nanocomposites improved with increasing the amount of nanoparticles. The addition of 1.5 phr GNP to the blends containing NBR with 33% and 45% acrylonitrile increased the tensile modulus by 56% and 49%, respectively. The tensile properties of the nanocomposites were also investigated at 50, 25, and 75°C. It was observed that with increasing the amount of nanoparticles, the deterioration of the mechanical properties at elevated temperatures was reduced. Also, thermal stability increased with increasing the amount of nanoparticles in all the samples.     

Investigation of the relationship between morphology and tribological properties of an epoxy resin based on tetraglycidyl 4,4′‐diaminodiphenylmethane modified with polyetherimide oligomers

In this paper, polyetherimides (PEI) with two different calculated number‐average molecular weights (M_n) of 5000 and 10,000 g/mol were synthesized and used to modify tetraglycidyl 4,4′‐diaminodiphenylmethane. Three different morphologies (separated phase, bi‐continuous phase, and phase inversion structure) were obtained by controlling molecular weights and content of PEI. Thermal and mechanical characterizations showed that addition of PEI resulted in an increase in thermal stability and tensile strength. Tensile strength of samples with bi‐continuous phase was higher than those with separated phase or phase inversion structure. Influence of morphologies on tribology properties were studied by a ring‐on‐block wear tester. Higher wear resistance was achieved from samples with bi‐continuous phase. It was found that wear life of samples with bi‐continuous phase was almost 100% higher than that of samples with separated phase. This is clearly related to the change in thermal and mechanical properties caused by the change of morphologies. Scanning electron microscope observations of worn surfaces and wear debris of the tested samples showed that tribological behaviors and wear mechanisms were heavily dependent on morphologies. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39863.     

Synergistic effects of zirconium- and aluminum co-doping on the thermoelectric performance of zinc oxide

This work aims to explore zirconium as a possible dopant to promote thermoelectric performance in bulk ZnO-based materials, both within the single-doping concept and on simultaneous co-doping with aluminum. At 1100–1223 K mixed-doped samples demonstrated around ～2.3 times increase in ZT as compared to single-doped materials, reaching ～0.12. The simultaneous presence of aluminum and zirconium imposes a synergistic effect on electrical properties provided by their mutual effects on the solubility in ZnO crystal lattice, while also allowing a moderate decrease of the thermal conductivity due to phonon scattering effects. At 1173 K the power factor of mixed-doped Zn_0.994Al_0.003Zr_0.003O was 2.2–2.5 times higher than for single-doped materials. Stability tests of the prepared materials under prospective operation conditions indicated that the gradual increase in both resistivity and Seebeck coefficient in mixed-doped compositions with time may partially compensate each other to maintain a relatively high power factor.     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

A mechanism study of chloride and sulfate effects on Hg reduction in sulfite solution

This paper studied the effects of sulfate and chloride ions on bivalent mercury (Hg²⁺) absorption and reduction behaviors in a simulated WFGD system. The aqueous mercuric ion-sulfite system reduction behaviors were monitored and investigated using a UV-visible spectrum. Thereafter, the mechanism of Hg²⁺ reduction in the presence of sulfate and chloride ions was proposed. Experimental results revealed that both sulfate and chloride ions had inhibition effects on aqueous Hg²⁺ reduction to Hg⁰. The inhibition was assumed due to the formation of (in the presence of ) and / (in the presence of Cl⁻). And it was found that complex was more stable than in excess of Cl⁻. The formation of the above-mentioned complexes in the presence of and Cl⁻ would damp the formation of HgSO₃, whose decomposition was assumed to be the key step of Hg²⁺ reduction.     

A review on the mechanical and electrical properties of graphite and modified graphite reinforced polymer composites

Carbon materials particularly in the form of sparkling diamonds have held mankind spellbound for centuries, and in its other forms, like coal and coke continue to serve mankind as a fuel material, like carbon black, carbon fibers, carbon nanofibers and carbon nanotubes meet requirements of reinforcing filler in several applications. All these various forms of carbon are possible because of the element's unique hybridization ability. Graphene (a single two-dimensional layer of carbon atoms bonded together in the hexagonal graphite lattice), the basic building block of graphite, is at the epicenter of present-day materials research because of its high values of Young's modulus, fracture strength, thermal conductivity, specific surface area and fascinating transport phenomena leading to its use in multifarious applications like energy storage materials, liquid crystal devices, mechanical resonators and polymer composites. In this review, we focus on graphite and describe its various modifications for use as modified fillers in polymer matrices for creating polymer-carbon nanocomposites.