Tensile modulus modeling of carbon‐filled liquid crystal polymer composites

Electrically and thermally conductive resins can be produced by adding conductive fillers to insulating polymers. Mechanical properties, such as tensile modulus, are also important. This research focused on performing compounding runs followed by injection molding and tensile testing of carbon‐filled Vectra liquid crystal polymer. The two carbon fillers investigated were Thermocarb synthetic graphite particles and Fortafil carbon fiber at varying filler amounts. The tensile modulus experimental results were compared to results predicted by several different models. It was found that the Halpin Tsai 2D Randomly Oriented fiber model provided the best fit to the experimental data. The degree of filler‐polymer adhesion was also studied with nanoscratch tests for synthetic graphite and carbon fiber fillers in three polymers: Vectra, nylon 6,6, and polycarbonate. The adhesion trends seen in the nanoscratch tests showed qualitative agreement with the tensile modulus, and should be considered in formulating advanced tensile modulus models. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Water vapor adsorption and volumetric swelling of melt‐impregnated wood–polymer composites

Wood–plastic composites were prepared through impregnation of solid wood with polyethylene. A resolution IV screening design of 16 runs for seven factors at two levels was adopted. The seven factors tested were ratio of maleated polyethylene in formulations, ratio of polyethylene of different molecular weights, four process factors (vacuum, pressure, time, and temperature), and wood species (red maple and aspen). Moisture adsorption content and volumetric changes as a function of time were investigated. This study also examined the effects of impregnation parameters and impregnants on water vapor adsorption and dimensional stability. The process parameters (pressure and temperature), polymer impregnants (polyethylene of different molecular weights), and wood species contributed significantly to the equilibrium moisture content (EMC), whereas the moisture adsorption rate was mainly affected by the polymer impregnants (polyethylene of different molecular weights). The EMC was inversely proportional to polymer retention. However, none of the variables significantly contributed to volumetric swelling; the volumetric swelling rate was mainly affected by wood species, the molecular weight of the polyethylene, and impregnation vacuum. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2668–2676, 2006     

Predictions of young's modulus of inorganic fibrous particulate‐reinforced polymer composites

In this study, the factors affecting the Young's modulus of inorganic fibrous particulate‐reinforced polymer composites were analyzed, and a new expression of the Young's modulus was derived and was based on a simplified mechanical model. This equation was used to estimate the composite Young's modulus. The estimated relative Young's modulus increased nonlinearly with increasing filler volume fraction. Finally, we verified the equation preliminarily by quoting the measured Young's modulus values of poly(butylene terephthalate)/wollastonite, polypropylene/wollastonite, and nylon 6/wollastonite composites reported in the literature. Good agreement was shown between the predictions and the experimental data of the relative Young's modulus values for these three composite systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2957–2961, 2013     

Synthesis of a glycosaminoglycan polymer mimetic using an N‐alkyl‐N,N‐linked urea oligomer containing glucose pendant groups

The synthesis of a glycosaminoglycan polymer mimetic is reported. An isopropylidene protected glucose methacrylate monomer was copolymerized under reversible addition fragmentation chain transfer polymerization control with an azido‐containing comonomer to a molecular weight of 29 000 g mol^?1 with polydispersity of 1.21. The comonomer ratio was determined to be 15:1 based on ¹H NMR spectroscopy. This copolymer was coupled to sugar‐functionalized N‐alkyl‐N,N‐linked urea oligomers using a copper catalyzed alkyne/azide cycloaddition reaction. The reaction efficiency was 100% as monitored by ¹H NMR spectroscopy. The isopropylidene protecting groups on the polymer and N‐alkyl‐N,N‐linked urea oligomers were removed using acid hydrolysis to give the final polysaccharide mimetic. It is expected that these polymers will have applications in a variety of future therapeutic applications. © 2013 Society of Chemical Industry     

Development of simplified Tandon‐Weng solutions of Mori‐Tanaka theory for Young's modulus of polymer nanocomposites considering the interphase

The known Tandon‐Weng model originated from Mori–Tanaka theory commonly underestimates the Young's modulus of polymer nanocomposites containing spherical nanofillers. This phenomenon is attributed to disregarding the nanoscale interfacial interaction between polymer and nanoparticles, which forms a different phase as interphase in polymer nanocomposites. In this paper, the simplified Tandon‐Weng model is developed assuming interphase and the predictions of the developed model are compared with the experimental data. The calculations of the developed model completely agree with the experimental results at reasonable levels of interphase properties. Additionally, the effects of main material and interphase properties on the predictions of modulus are evaluated. The developed model predicts that a high‐content, thick, and strong interphase creates a high modulus in polymer nanocomposites. These logical observations demonstrate the correctness of the developed model for Young's modulus of polymer nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43816.     

Palladium‐Catalyzed N‐Arylation of N,N‐Dialkylhydrazines with Aryl Chlorides

N,N‐Dialkyl‐N′‐arylhydrazines have been prepared usually in high to excellent yields via the reaction of N,N‐dialkylhydrazines with aryl chlorides in the presence of Pd₂(dba)₃, Xphos and NaO‐t‐Bu in dioxane at 120 °C. With ortho‐substituted aryl chlorides best results have been obtained by using 2‐(2′,6′‐dimethoxybiphenyl)dicyclohexylphosphine (ligand d) as the ligand.     

Unidirectional fiber–polymer composites: Swelling and modulus anisotropy

The solvent swelling of unidirectional rubber–fiber composites was studied. The amount of matrix swelling was constrained to the extent that would be predicted from the thermodynamic theories of elasticity and polymer–solvent interaction. The geometry of swelling was found to be orthotropic in nature. A simple trigonometric function was derived to relate linear deformation due to swelling to the angle which the direction of its measurement makes with the fiber direction. The validity of the derivation was demonstrated experimentally. Considering swelling to be the imposition of tensile forces of equal magnitude in all directions, and considering a swelling-induced linear deformation to be analogous to a tensile compliance, a simple set of relationships between elastic parameters and their direction of measurement was derived: where E_θ, G_θ, v_θ, and η_θ are Young's modulus, shear modulus, Poisson's ratio, and the shear coupling ratio measured in a longitudinal transverse plane at an angle with the fiber direction, respectively, and E_L, G_LT, and θ_LT are the longitudinal Young's modulus, the longitudinal transverse shear modulus, and the longitudinal transverse Poisson ratio, respectively. Further simplifying the case of combined transverse isotropy and special orthotropy was the conclusion that 1/G_LT = 1/E_T + (1 + 2v_LT)/E_L. The relationships for G and E were experimentally demonstrated.     

Synthesis and Properties of N‐Alkyl–N,N‐Dimethyl‐N‐(o‐Hydroxymethyl)Benzylammonium Chlorides

A series of N‐alkyl–N,N‐dimethyl‐N‐(o‐hydroxymethyl)benzylammonium chlorides surfactants (DHBA‐m) were synthesized using o‐chloromethylbenzyl alcohol and N‐alkyl–N,N‐dimethyl tertiary amine as raw materials. The structure of the products was confirmed by FT‐IR, ¹H NMR, ¹³C NMR and MS. DHBA‐m surfactants exhibit low Krafft points and high surface activities. The process of micellization of DHBA‐m is spontaneous, exothermic, and entropy‐driven. The hydroxymethyl substitution increases hydrophobicity of DHBA‐m, thus making micellization more favorable compared with that of N‐dodecyl–N,N‐dimethyl‐N‐benzylammonium chlorides (DDBAC‐m). The bactericidal activity of DHBA‐m is stronger on E. coli than that of DDBAC‐12, and DHBA‐16 shows strong bactericidal activity on Salmonella, S. aureus, and Streptococcus.     

Evaluation of dynamic modulus measurement for C/C-SiC composites at different temperatures

The determination of elastic properties at application temperature is fundamental for the design of fibre reinforced ceramic composite components. An attractive method to characterize the flexural modulus at room and high temperature under specific atmosphere is the nondestructive Resonant Frequency Damping Analysis (RFDA). The objective of this paper was to evaluate and validate the modulus measurement via RFDA for orthotropic C/C-SiC composites at the application temperature. At room temperature flexural moduli of C/C-SiC with 0/90° reinforcement were measured under quasi-static 4-point bending loads and compared with dynamic moduli measured via RFDA longitudinally to fibre direction. The dynamic modulus of C/C-SiC was then measured via RFDA up to 1250°C under flowing inert gas and showed an increase with temperature which fitted with literature values. The measured fundamental frequencies were finally compared to those resulting from numerical modal analyses. Dynamic and quasi-static flexural moduli are comparable and the numerical analyses proved that bending modes are correctly modeled by means of dynamic modulus measured via RFDA. The nondestructive RFDA as well as the numerical modeling approach are suitable for evaluation of C/C-SiC and may be transferred to other fibre reinforced ceramic composite materials.     

Preparation of thermosensitive and superabsorbent polymer hydrogels from trialkyl‐4‐vinylbenzyl phosphonium chloride‐N‐isopropylacrylamide‐N,N′‐methylenebisacrylamide copolymers and their properties

Thermosensitive and superabsorbent polymer hydrogels were synthesized by copolymerization of three kinds of tri‐n‐alkyl vinylbenzyl phosphonium chlorides (TRVB) with different lengths of alkyl chains, N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide (MBAAm). The water‐absorption ability and antibacterial activity of the hydrogels against Staphylococcus aureus (S. aureus) were investigated. The water content of TRVB–NIPAAm–MBAAm copolymers decreased with increasing temperature and increased with increasing phosphonium groups in the copolymers, while it decreased with increasing chain length of the alkyl groups in the phosphonium groups as well as with an increasing degree of crosslinking in the copolymers. The TRVB–NIPAAm–MBAAm copolymers with a higher TRVB content in the copolymers exhibited higher antibacterial activity against S. aureus, but decreased with increasing chain length of alkyl groups in phosphonium groups. The TRVB–NIPAAm–MBAAm copolymers exhibited the highest antibacterial activity at 30°C against S. aureus in deionized water. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 115–124, 2001     

Synthetic Procedures Yielding Targeted Nitro and Nitroso Derivatives of the Propellant Stabilisers Diphenylamine,N‐Methyl‐4‐nitroaniline,and N,N′‐Diethyl‐N,N′‐diphenylurea

Synthetic methodologies have been developed which yield a variety of diphenylamine (DPA) and 1,3‐diethyl‐l,3‐diphenylurea (ethylcentralite or EC) propellant stabiliser degradation derivatives in high yield. The N‐alkyl nitroanilines (N‐methyl‐2,4,6‐trinitroaniline; N‐methyl‐2,4‐dinitroaniline; N‐ethyl‐2,4,6‐trinitroaniline; N‐ethyl‐2,4‐dinitroaniline; N‐ethyl‐4‐nitroaniline; N‐ethyl‐2‐nitroaniline) have been obtained either by reaction of the parent aniline with the required alkyl halide under mild conditions or via Ullmann type chemistry. A robust and high yielding approach for the synthesis of di, tri and tetranitrodiphenylamines (2,2′,4,4′‐tetranitrodiphenylamine; 2,4,4′‐trinitrodiphenylamine; 2,2′,4‐trinitrodiphenylamine; 2,4,6‐trinitrodiphenyl‐amine; 2,4‐dinitrodiphenylamine) is reported which involves passing the nitroanilines and chloronitrobenzenes down a base activated alumina column. The N‐nitroso‐N‐alkyl compounds (N‐nitroso‐N‐ethyl‐4‐nitroaniline; N‐nitroso‐N‐ethyl‐2‐nitroaniline; N‐nitroso‐N‐Methyl‐4‐nitroaniline; N‐ethyl‐N‐nitrosoaniline; N‐nitroso‐2‐nitrodiphenylamine) have been synthesised using nitrosyl acetate in acetic acid as the N‐nitrosating agent.     

Dual lower critical solution temperature polymer networks based on block,laminate, and interpenetrating network structures composed of N‐alkylacrylamides and N,N‐dialkylaminoethyl methacrylates

Novel materials that display two lower critical solution temperatures (LCSTs) were developed by forming block copolymers, laminate structures, and interpenetrating networks of crosslinked polymer systems that displayed temperature sensitivity independently. A number of LCST polymers and copolymers were investigated, including those based on N‐isopropylacrylamide, N,N‐diethylacrylamide, N,N‐diethylaminoethyl methacrylate, and N,N‐dimethylaminoethyl methacrylate. The polymer structure was found to profoundly influence the thermal sensitivity, as polymer formulation techniques led to materials with varying degrees of temperature sensitivity. Random and block copolymerization, along with interpenetrating networks and laminate systems, were studied, with only the structures having the greatest physical separation between pendent chains of different types having the ability to separate temperature transitions. Experiments were conducted to characterize the equilibrium swelling behavior and thermal transitions in the polymer systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2974–2981, 2003     

Synthesis and properties of PVC‐bound N,N‐dialkylaminopyridine

A linear poly(vinyl chloride) (PVC)‐supported dialkylaminopyridine was prepared through PVC treated with N‐methylaminopyridine and NaH in tetrahydrofuran. The properties of this PVC‐bound catalyst were examined by acetylation of linalool and 5‐FU. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1067–1069, 2002; DOI 10.1002/app.10391     

Bearing strength of pin‐connected polymer composites subjected to dynamic loading

In this study, static load bearing strength of pin‐connected carbon fiber‐reinforced polyphenylenesulphide (PPS) composites that have [(0°/90°)]_3s stacking sequence was investigated. Firstly, the samples were loaded dynamically, and then the same samples were loaded statically. The results obtained from this sequential experiment were compared with the results obtained from samples that were loaded only statically. In addition, the fatigue life and failure mechanisms were investigated with respect to the selection of the geometrical parameters. Dynamic and static loading experiments were performed according to the ASTM STP 749 and ASTM D953 standards, respectively. To obtain optimum load bearing values, the ratio of distance between the edge and hole center to hole diameter (E/D) and ratio of sample width to hole diameter (W/D) has been systematically changed. According to the experimental results, maximum load bearing values have been obtained when E/D ratio was equal to 2. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Redox polymer with N,N‐dichlorosulfonamide functional groups as arsenite oxidant in aqueous solutions

A macroporous, styrene‐divinylbenzene polymer with N,N‐dichlorosulfonamide functional groups (? SO₂NCl₂), containing two chlorine atoms with oxidation number +1, have been prepared through the chemical modification of a commercial sulfonic cation exchanger (Amberlyst 15, Rohm and Haas). Obtained product was used as the heterogeneous oxidant of As(III) in aqueous solutions. The polymer's oxidizing capacity, determined as part of the batch studies, amounted to 193.29 mg As(III) g^?1 (pH = 7.7) and 206.03 mg As(III) g^?1 (pH = 2.0). The suitability of the redox polymer for long‐lasting operation in the aqueous environment was confirmed in the column study conducted using a solution with a concentration of 10 mg As(III) dm^?3 at a flow rate of 6 bed volumes (BV) h^?1. The concentration of As(III) in the effluent reached the value of 0.01 mg As(III) dm^?3 only after 8 weeks of continuous operation when 7930 BV of the solution had passed through the bed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41552.     

Numerical simulation of the effect of nanotube orientation on tensile modulus of carbon‐nanotube‐reinforced polymer composites

By correlating the curvature of carbon nanotubes to the orientation of fibers in a polymer, the effect of the curvature of nanotubes on the tensile modulus of carbon‐nanotube‐reinforced polymer composites was investigated with a numerical simulation method. The simulation results showed that the tensile modulus of a nanotube‐reinforced composite drops sharply when the nanotubes diverge from their orientation in the axial direction, and the presence of curved nanotubes in the polymer matrix significantly decreases the modulus of the composite. This finding could explain, partly, why in most cases, the predicted tensile modulus of a carbon‐nanotube‐reinforced composite, based on the assumption that the nanotubes are fully isolated and aligned in the polymer matrix, is much higher than the value obtained from experiments. Copyright © 2004 Society of Chemical Industry     

Hydrodynamic properties for N,N,N′,N′‐tetraalkyl diglycolamides dissolved in n‐dodecane system

N,N,N′,N′‐tetraoctyl diglycolamide (TODGA) and N,N,N′,N′‐tetra(2‐ethylhexyl) diglycolamide (T2EHDGA) have been identified as promising extractants for actinide partitioning from high‐level nuclear waste. These extractants are proposed to be used along with suitable phase modifiers, viz. N,N‐dihexyl octanamide (DHOA), tri‐n‐butyl phosphate (TBP) and 2‐decanol dissolved in n‐dodecane. Hydrodynamic parameters, viz. density, viscosity and interfacial tension (IFT) are important for optimisation of hydrometallurgical process to ensure that there is no emulsion formation and to achieve desired phase disengagement rate. Densities and viscosities of the two extractants, viz. TODGA and T2EHDGA along with different phase modifiers have been measured over different range of compositions and temperatures (298–333 K). The viscosity data have been used to calculate the activation energy for viscous flow for each composition of solvents. The IFT values have also been measured for different solvent compositions. The viscosity and IFT data of TODGA and T2EHDGA with 2‐decanol as phase modifier appears suitable under hydrometallurgical conditions proposed for actinide partitioning. © 2011 Canadian Society for Chemical Engineering     

Highly Active and Diastereoselective N,O‐ and N,N‐Yttrium Complexes for Intramolecular Hydroamination

The intramolecular hydroamination of aminoalkynes and unactivated aminoalkenes catalyzed by yttrium N,O‐ and N,N‐complexes has been investigated. The N,N‐yttrium complexes are highly active, catalyzing the conversion of a wide range of terminal aminoalkenes at room temperature, and internal aminoalkenes at elevated temperature, to yield pyrrolidine and piperidine products in high yields. A high diastereoselectivity of up to 23:1 is observed at 0 °C with 1‐methyl‐4‐pentenylamine as substrate.     

Application of raman microscopy to the analysis of high modulus polymer fibres and composites

Raman microscopy has been used to study the deformation of carbon fibres and an experimental grade carbon-fibre/PEEK composite prepreg. It has been found that the peak position of the Raman-active bands in the fibres are sensitive to the level of applied strain. Examination of the peak positions from the carbon fibres near the surface of the prepreg shows that the fibres are subjected to a residual compressive strain. The application of a tensile stress to the composite causes the fibre strain to become tensile although significant scatter is found in the measurements. The scatter is thought to be due to variations in the local carbon-fibre strain at the 1 μm level. It is demonstrated that residual compressive strain is expected from differential shrinkage between the fibres and matrix on cooling the composite from the processing temperature to room temperature.     

Syntheses and Analyses of N,N′‐Dinitrourea

N,N′‐Dinitrourea was prepared through nitration of urea at low temperature in mixed acids in 67 % yield. The prepared material was pure and found to be stable at room temperature. The properties of N,N′‐dinitrourea were analysed by: TG, DSC, ignition test in Wood's metal bath, NMR, MS, FT‐IR, gaspycnometry and BAM impact and friction sensitivity tests. N,N′‐Dinitrourea was found to have a very high density and positive oxygene balance. It was, however, found to be sensitive both to impact and friction.