Theoretical and experimental analyses of rheological,compatibility and mechanical properties of PVMQ/XNBR-g GMA/XNBR/GO ternary hybrid nanocomposites

Iranian Polymer Journal - Effects of graphene oxide (GO) on various properties of rubber hybrid nanocomposites based on PVMQ/XNBR-g-GMA/XNBR (phenyl-vinyl-methyl-polysiloxane/carboxylated nitrile...     

Nonisothermal cure kinetics of diglycidylether of bisphenol‐A/amine system reinforced with nanosilica particles

Epoxy‐silica nanocomposites were obtained from directly blending diglycidylether of bisphenol‐A (DGEBA)‐based epoxy and nanoscale silica (NS) and then curing with 4,4′‐diaminodiphenylamine (DDA). The effect of amount of nanosilica (NS) particles as catalyst on the mechanism and kinetic parameters of cure reaction of DGEBA/DDA system was studied. The kinetics parameters were obtained from nonisothermal differential scanning calorimeter (DSC) data using the Kissinger and Ozawa equations. The exothermic peak was shifted toward lower temperatures in DGEBA/DDA/NS system with increasing the amount of nanoslica particles. However, the existence of NS particles with hydroxyl groups in the structure in the mixture of DGEBA/DDA catalyzes the cure reaction and increases the rate constant. The activation energy of cure reaction of DGEBA/DDA system obtained from two methods were in good agreement, and showed a decrease when NS particles were present in the mixture. The mechanism of reaction of DGEBA with DDA was carried out by isothermal curing in the oven at 130°C and measuring the disappearance peak of epoxide group at 916 cm^?1 using FTIR. The diffusive behavior of two systems was investigated during water sorption at 25°C and the experimental results fitted well to Fick's law. Diffusion coefficient of cured sample from DGEBA/DDA/10% NS blend decreased in comparison with the sample without NS particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3855–3863, 2007     

Nonisothermal cure kinetics of DGEBA with novel aromatic diamine

The effect of the molar ratio of diglycidyl ether of a bisphenol‐A based epoxy (DGEBA) and synthesized 4‐phenyl‐2,6‐bis(4‐aminophenyl)pyridine (PAP) as curing agent during nonisothermal cure reaction by the Kissinger, Ozawa, and isoconversional equations was studied. The cure mechanism was studied by FTIR analysis. Kinetic analysis of the curing reaction of DGEBA at two different concentrations (42 and 32 phr) of the curing agent was studied by using DSC analysis. With an increasing PAP content, the pre‐exponential factor increased by increasing collision probability between epoxide and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of crosslink density. The activation energies obtained from three equations were in good agreement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3076–3083, 2007.     

Synthesis and properties of organosoluble polyimides based on novel flourene‐ring containing diacetamido‐diamine

A new diacetamido‐diamine monomer, N′‐[7‐(acetyl‐4‐aminoanilino)‐9,9‐dioctylflouren‐2‐yl]‐N′‐4‐aminophenyl) acetamide (ADOAc), with flourene‐based structure was prepared from the reaction of 4‐aminoacetanillide with 2,7‐dibromo‐9,9‐dioctylfluorene in the presence of 10 mol % CuI, 20 mol % N,N′‐dimethylethylene diamine as catalyst and K₂CO₃ as base. Two new flourene‐ring containing polyimides were prepared from the reaction of ADOAc with aromatic dianhydrides such as pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) via chemical imidization of poly(amic acid). The new diamine and the related polyimides were characterized by using conventional methods such as FT‐IR, NMR, and elemental analysis. The polyimides obtained from the reaction of ADOAc with PMDA (PIa) and of ADOAc with BTDA (PIb) had inherent viscosity of 0.49 and 0.58 dL/g respectively, and showed excellent solubility in a variety of organic solvents. The polyimides of PIa and PIb showed excellent thermal stability with 10% weight loss in nitrogen atmosphere at temperatures of 418°C and 407°C and T_g of 172°C and 167°C, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of novel photoactive polyamide derived from substituted fluorene by copper (I) catalyst

A novel polyamide has been successfully prepared through the reaction of 2,7‐dibromo‐9,9‐dioctylfluorene with 2,5‐dipiperazinedione in the presence of CuI, N,N′‐dimethylethylene diamine (DMEDA) and K₂CO₃ as base mixture and as catalyst. The structures of the monomer and the resulting model compound, as well as the structure, solution viscosity, solubility, molecular weights, thermal behavior, thermal stability, and light absorption and emission spectra of the resulting polyamide were characterized by means of FTIR, elemental analysis, ¹H‐NMR, ¹³C‐NMR, DSC, TGA, GPC and UV–visible absorption, and fluorescence emission spectrophotometers. The polyamide possesses excellent solubility in organic solvents such as tetrahydrofuran (THF), N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), ethylacetate, acetone, ethanol, pyridine, chloroform, and toluene at room temperature. The polyamide had inherent viscosity of 0.65 dL/g, and molecular weights of M_n= 4.25 × 10⁴ and M_w= 5.99 × 10⁴ g/mol. The polyamide had glass transition temperature (T_g) of 138°C, and 10% weight loss at 350°C in nitrogen. The polyamide showed strong UV absorption and blue emission in solution and in solid state. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

Synthesis of polyamides from substituted fluorene and diamides in the presence of a copper(I) catalyst

2,7‐Dibromo‐9,9‐dioctylfluorene was synthesized by a two‐step reaction from fluorene and n‐octylboromide. This was reacted with benzamide for the preparation of a model compound and with terephthalamide, isophthalamide, and adipamide for the preparation of polyamides in the presence of a mixture of 10 mol % CuI and 20 mol % N,N′‐dimethylethylenediamine as a catalyst and K₂CO₃ as a base. The monomer and the model compound were characterized with Fourier transform infrared, proton nuclear magnetic resonance, and elemental analysis. The prepared polyamides were characterized with Fourier transform infrared, proton nuclear magnetic resonance, differential scanning calorimetry, thermogravimetric analysis, and solubility and viscosity measurements. The obtained polyamides possessed excellent solubility in common organic solvents, and they exhibited inherent viscosities in the range of 0.93–1.19 dL/g. According to the differential scanning calorimetry analysis, the glass‐transition temperatures of the polyamides were in the range of 84–154°C. Thermogravimetric analysis indicated that a 2% weight loss of the polyamides occurred in the temperature range of 218–253°C under a nitrogen atmosphere. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of the epoxy functionalization of multiwall carbon nanotubes on the nonisothermal cure kinetics and thermal properties of epoxy/multiwall carbon nanotube nanocomposites

Multiwall carbon nanotubes were functionalized with epoxy groups by chemical modification in four stages. At each stage, the compound was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). Epoxy composite samples were prepared by mixing diglycidyl ether of bisphenol A‐based epoxy resin and synthetic epoxy‐functionalized multiwall carbon nanotube (E‐MWCNT) with different percentages (1, 3, 6, 9, 12, and 15%) in acetone. Ultrasonic dispersion was used to produce homogenous blends. The optimum ratio of the reacting components (9%) was investigated by total enthalpy of the curing reaction from differential scanning calorimetry (DSC) thermograms. The kinetics of the curing reaction for epoxy composites with 4,4′‐diaminodiphenylsolfon as a curing agent was studied by means of a DSC nonisothermal technique. The kinetic parameters such as activation energy, pre‐exponential factor, and rate constant were obtained from DSC data. The structure ofthe nanocomposites and dispersion of the E‐MWCNTs in the nanocomposites were observed using SEM, and the thermal properties were studied by thermogravimetric analysis. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effects of two types of nanoparticles on the cure,rheological, and mechanical properties of rubber nanocomposites based on the NBR/PVC blends

The effects of graphene nanoplatelet (GNP) and organoclay montmorillonite (OMMT) on the curing, relaxation, and the mechanical properties of acrylonitrile-butadiene rubber/polyvinyl chloride (NBR/PVC) nanocomposites were investigated. Scorch and cure times of nanocomposites reinforced with GNP increased, while these parameters for nanocomposites reinforced with OMMT decreased. Maximum torque and cure rate increased after adding the nanoparticles. In the relaxation curves, with increasing nanoparticle and acrylonitrile (ACN) content, both the slopes of short- and long-term regions, raised. Cured compounds have the significantly higher initial and final modulus, the greater elastic slope, and lower viscous slope than the uncured ones. The results of the relaxation test showed that the relaxation percentage in the uncured samples was much higher than the cured ones. Also, with the addition of both GNP and OMMT, this parameter had an upward trend. DG_S/DG_L parameter increased with the addition of nano-reinforcements in the uncured state while decreasing in the cured state. For example, the blend containing N3 reinforced via GNP showed an 11% increase in the uncured state, whereas 14% reduction in the cured state. Tensile strength, elastic modulus, and hardness were improved by incorporating nanoparticles, while the effect of GNP was more intense. The similar trend observed in samples with NBR type of higher ACN content. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47550.