Morphology and properties of highly filled iPP/TiO2 nanocomposites

Nanocomposites based on isotactic polypropylene (iPP) and titanium dioxide (TiO₂) nanoparticle containing 1–15 vol% (4.6–45.5 wt%) of the nanoparticle were prepared by the melt blending process. The effect of an anhydride‐modified polypropylene as a compatibilizer on dispersion of TiO₂ nanoparticles was assessed using SEM. TGA and DSC analysis were performed to study the thermal properties of the nanocomposites. Crystalline structures of iPP in the presence of TiO₂ were analyzed by XRD. Mechanical properties of the nanoparticles were measured and a micromechanical analysis was applied to quantify interface interaction between the polymer and particle. SEM results revealed improvement of TiO₂ particle dispersion by adding the compatibilizer. It was shown that the thermal stability and crystalline structure of the nanocomposite are significantly affected by the state of particle dispersion. TiO₂ nanoparticles were shown to be strong β‐nucleating agents for iPP, especially at concentrations less than 5 vol%. Presence of the β‐structure crystals reduced the elastic modulus and yield strength of the nanocomposites. Micromechanical analysis showed enhanced interaction between organic and inorganic phases of the compatibilized nanocomposites. POLYM. ENG. SCI., 54:874–886, 2014. © 2013 Society of Plastics Engineers     

Static and dynamic compressive properties of polypropylene/zinc oxide nanocomposites

The effect of strain rate is widely recognized as an essential factor that influences the mechanical properties of polymer matrix composites. Despite its importance, no previous work has been reported on the high‐strain rate behavior of polypropylene/zinc oxide nanocomposites. Based on this, static and dynamic compression properties of polypropylene/zinc oxide nanocomposites, with particle contents of 1%, 3%, and 5% by weight, were successfully studied at different strain rates (i.e., 0.01 s^?1, 0.1 s^?1, 650 s^?1, 900 s^?1, and 1100 s^?1) using a universal testing machine and a split Hopkinson pressure bar apparatus. For standardization, approximately 24 nm of zinc oxide nanoparticles were embedded into polypropylene matrix for each of the tested polypropylene/zinc oxide nanocomposites. Results show that the yield strength, the ultimate strength, and the stiffness properties, of polypropylene/zinc oxide nanocomposites, were greatly affected by both particle loading and applied strain rate. Furthermore, the rate sensitivity and the absorbed energy of all tested specimens showed a positive increment with increasing strain rate, whereas the thermal activation volume showed a contrary trend. In addition, the fractographic analysis and particle dispersion of all composite specimens were successfully obtained using a field emisission scanning electron microscopy. POLYM. ENG. SCI., 54:949–960, 2014. © 2013 Society of Plastics Engineers     

Dynamic mechanical behavior and nanostructure morphology of hyperbranched‐modified polypropylene blends

Polypropylene (PP) was modified utilizing two types of polyesteramide‐based hyperbranched polymers (amphiphilic PS and hydrophilic PH). A maleicanhydride‐modified PP (PM) was used as a reactive dispersing agent to enhance the modification by grafting the hyperbranched polymers onto the PP chains. Pure PP, two different non‐reactively modified samples, i.e. excluding PM, and two different reactively modified samples, i.e. including PM, were studied. Investigating the morphology of the samples was performed by scanning electron microscopy. To follow the effect of the modification on the dynamic mechanical properties, dynamic mechanical analysis experiments both in the melt (rheometric mechanical spectrometry) and in solid state (dynamic mechanical thermal analysis) were carried out. In the next step, the nanocrystalline structure of the samples was studied by small angle X‐ray scattering (SAXS) in two different modes, i.e. static and recrystallization. Hundreds of SAXS patterns were analyzed automatically using procedures written in PV‐WAVE image‐processing software. The chord distribution function (CDF) was calculated and the long period (l_p) of the crystal lamellae was extracted from the CDFs. The rheometric mechanical spectrometry results show that both hyperbranched polymers decrease complex viscosity η^* and enhance liquid‐like behavior. This happens more significantly when PM is included. The dynamic mechanical thermal analysis results reveal that T_g decreases when PS and PH are added. In the reactively modified samples this reduction is compensated most probably because of the crosslinked structure formed through the grafting reaction between the hyperbranched polymers and PM. Such structure is confirmed by SAXS data and calculated CDFs in the recrystallization mode. Static SAXS data also show enhancement in the crosshatched morphology of the crystalline lamellae of PP for reactively modified samples compared with non‐reactively modified samples. © 2013 Society of Chemical Industry     

Impact of a Stereocentre Inversion in Cyclic Lipodepsipeptides from the Viscosin Group: A Comparative Study of the Viscosinamide and Pseudodesmin Conformation and Self‐Assembly

The viscosin group covers a series of cyclic lipodepsipeptides (CLPs) produced by Pseudomonas bacteria, with a range of biological functions and antimicrobial activities. Their oligopeptide moieties are composed of both L ‐ and D ‐amino acids. Remarkably, the Leu5 amino acid—centrally located in the nonapeptide sequence—is the sole residue found to possess either an L or D configuration, depending on the producing strain. The impact of this D /L switch on the solution conformation was investigated by NMR‐restrained molecular modelling of the epimers pseudodesmin A and viscosinamide A. Although the backbone fold remained unaffected, the D /L switch adjusted the segregation between hydrophobic and hydrophilic residues, and thus the amphipathicity. It also influenced the self‐assembly capacity in organic solvents. Additionally, several new minor variants of viscosinamide A from Pseudomonas fluorescens DR54 were identified, and an NMR assay is proposed to assess the presence of either an L ‐ or D ‐Leu5.     

Molecular Characterization of α- and β-Thalassaemia among Malay Patients

Both α- and β-thalassaemia syndromes are public health problems in the multi-ethnic population of Malaysia. To molecularly characterise the α- and β-thalassaemia deletions and mutations among Malays from Penang, Gap-PCR and multiplexed amplification refractory mutation systems were used to study 13 α-thalassaemia determinants and 20 β-thalassaemia mutations in 28 and 40 unrelated Malays, respectively. Four α-thalassaemia deletions and mutations were demonstrated. −−^SEA deletion and α^CSα accounted for more than 70% of the α-thalassaemia alleles. Out of the 20 β-thalassaemia alleles studied, nine different β-thalassaemia mutations were identified of which β^E accounted for more than 40%. We concluded that the highest prevalence of (α- and β-thalassaemia alleles in the Malays from Penang are −−^SEA deletion and β^E mutation, respectively.     

Stabilization loop of a two axes gimbal system using self-tuning PID type fuzzy controller

The application of inertial stabilization system is to stabilize the sensor's line of sight toward a target by isolating the sensor from the disturbances induced by the operating environment. The aim of this paper is to present two axes gimbal system. The gimbals torque relationships are derived using Lagrange equation considering the base angular motion and dynamic mass unbalance. The stabilization loops are constructed with cross coupling unit utilizing proposed fuzzy PID type controller. The overall control system is simulated and validated using MATLAB. Then, the performance of proposed controller is evaluated comparing with conventional PI controller in terms of transient response analysis and quantitative study of error analysis. The simulation results obtained in different conditions prove the efficiency of the proposed fuzzy controller which offers a better response than the classical one, and improves further the transient and steady-state performance.     

Mechanical, rheological, and thermal behavior assessments in HDPE/PA-6/EVOH ternary blends with variable morphology

Visco-elastic and dielectric spectra of multiwalled carbon-nanotube reinforced silicon elastomer nanocomposites were used to study relaxation behavior. SEM photomicrographs shows well dispersion of MWCNT in elastomer matrix. In visco-elastic analysis primary relaxation was studied as a function of temperature (?100 to 100 °C) at frequency 1Hz and strain 1 %. The effect of MWCNT loadings on storage modulus, loss modulus, and loss tangent has been studied. The non-linearity in loss tangent, storage modulus and loss modulus was explained on the basis of MWCNT-elastomer interaction and the inter-aggregate attraction of MWCNT. The secondary β relaxation was studied using dielectric relaxation spectra in the frequency range of 0.1 Hz to 10⁶ Hz. The effect of MWCNT loadings on the complex and real parts of impedance was distinctly visible which has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium and relaxation dynamics of polymer chains in the vicinity of fillers. The dielectric formalism has been utilized to further investigate the conductivity and relaxation phenomenon. The ‘percolation limit’ of the MWCNT in the silicon elastomer was found to be in the range of 4 phr loading.     

Synthesis,Characterization and Evaluation of the Surface Active Properties of Novel Cationic Imidazolium Gemini Surfactants

New imidazolium gemini surfactants were synthesized by reaction of epichlorohydrin with long chain fatty alcohols furnishing products 2-(alkoxymethyl)oxirane followed by their subsequent treatment with imidazole resulting in the formation of 1-(1H-imidazol-1-yl-3 alkoxy)propane-2-ol which on subsequent treatment with 1,2-dibromoethane and 1,3-dibromopropane resulted in the formation of title gemini surfactants:1,2-bis(1(3-alkoxy-2-hydroxypropyl)-1H-imidazol-3-ium)ethane bromide (7), 1,3-bis(1(3-alkoxy-2-hydroxypropyl)-1H-imidazol-3-ium)propane bromide (8), 1,2-bis(1(3-alkoxy-2-hydroxypropyl)-1H-imidazol-3-ium)ethane bromide (9), 1,3-bis(1(3-alkoxy-2-hydroxypropyl)-1H-imidazol-3-ium)propane bromide (10), 1,2-bis (1(3-alkoxy-2-hydroxypropyl)-1H-imidazol-3-ium)ethane bromide (11) and 1,3-bis (1(3-alkoxy-2-hydroxypropyl)-1H-imidazol-3-ium)propane bromide (12). Their identification was based on IR, ¹H-, ¹³C-NMR, DEPT, COSY and mass spectral studies. Their surface active properties were also evaluated on the basis of surface tension and conductivity measurements.