Influence of phase modifiers on morphology and properties of thermoplastic elastomers prepared from ethylene propylene diene rubber and isotactic polypropylene

A series of thermoplastic elastomers (TPEs) were prepared from a binary blend of ethylene propylene diene rubber (EPDM) and isotactic polypropylene (iPP) using different types of phase modifiers. The influence of sulphonated EPDM, maleated EPDM, styrene‐ethylene‐co‐butylene‐styrene block copolymer, maleated PP, and acrylated PP as phase modifiers showed improved physico‐mechanical properties (like maximum stress, elongation at break, moduli, and tension set). Scanning electron and atomic force microscopy studies revealed better morphologies obtained with these phase modified EPDM‐iPP blends. The dependence of the phase modifier type and concentration was optimized with respect to the improvement in physical properties and morphology of the blends. Physical properties, dynamic mechanical properties, and morphology of these blends were explained with the help of interaction parameter, melt viscosity, and crystallinity of the blends. Theoretical modeling showed that Kerner, Ishai‐Cohen, and Paul models predicted the right morphology–property correlation for the prepared TPEs. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Augmenting the performance of acrylonitrile–butadiene–styrene plastics for low‐noise dynamic applications

The main objective of this study was to enhance the performance of acrylonitrile–butadiene–styrene (ABS) plastics for dynamic structural applications, including those of automobile relevance. First, ABS was modified by blending with maleic anhydride grafted styrene–ethylene–butadiene–styrene block copolymer (MA‐g‐SEBS) in various proportions. Squeaking noise characteristics were evaluated by measurement of the frictional behavior in an in‐house fabricated friction testing apparatus, and the results are explained on the basis of the change in surface energy upon modification. Detailed dynamic mechanical analyses (strain, frequency, and temperature sweep) revealed significant improvements in the damping characteristics of the modified ABS, especially that modified with 10 wt % MA‐g‐SEBS, without much sacrifice in its mechanical strength. The modulus values predicted with Kerner's model of the blends were well correlated with the morphological changes upon modification. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Construction and generation of OCDMA code families using a complete row-wise orthogonal pairs algorithm

A new code construction algorithm for incoherent Multi-Dimensional Optical Code Division Multiple Access (MD-OCDMA) for asynchronous fiber optic communication is proposed. We refer multi-dimensionality to two-dimensional (2D) wavelength–time or space–time domains and three-dimensional (3D) space–wavelength–time domains. The application of the algorithm in constructing 2D multiple pulses per row codes and 3D multiple pulses per plane codes is given. The performance of the codes is discussed. In the applications discussed, this construction ensures a maximum crosscorrelation of 1 between any two codes. The proposed codes have complete 1D code allocation, which increases the cardinality. The performance of some codes in literature is compared with the proposed codes. The analyzed performance measure is bit error rate due to multiple access interference for different numbers of active users. The performance analysis shows that the proposed 2D construction offers very low bit error rate at lower spectral efficiency when compared with other 2D constructions. A comparison of the proposed 3D construction with existing 3D constructions shows lower bit error rate for equivalent code dimension. New integrated optic designs for the generation of OCDMA codes using titanium indiffused lithium niobate technology are explored, which can enable compact encoders and decoders for computer communications.     

MWCNT reinforced Polyamide-6,6 films: preparation,characterization and properties

Composite films of Polyamide-6,6 (PA66) and multi-walled carbon nanotubes (MWCNTs) were prepared by a combination of solution casting followed by compression molding techniques. Both unfunctionalized (u-MWCNTs) and functionalized nanotubes (f-MWCNTs) were used in this study. The functionalization involved direct solvent-free amination of MWCNTs with hexamethylenediamine. Thermogravimetric analysis was used to observe the changes in the nanotubes upon functionalization and morphological features of the resulting composite films were studied using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The crystallinity changes by incorporation of the u-MWCNTs and f-MWCNTs in the PA66 matrix were studied by wide angle X-ray scattering and differential scanning calorimetry. The f-MWCNT/PA66 film showed an improvement of ∼43% in maximum tensile stress (MTS) and ∼32% in Young’s modulus over pristine PA66 film, while at a similar loading of 0.5 wt%, the f-MWCNT/PA66 film showed ∼15% increase in MTS and ∼16% increase in modulus over the u-MWCNT/PA66 film. Dynamic mechanical analysis indicated significant difference in the small-strain mechanical properties between the MWCNT-filled and unfilled PA66 at the very low MWNT loadings that were tested and supported the tensile results. The water absorption trend of the composite films showed dramatic improvement over the neat film.     

Behavior of alginate–gelatin blended gel with embedded macrovoids: Stress-induced changes and the solute release characteristics

Blending of gelatin to alginate promote cell–material interaction. However, the changes in diffusive and mechanical properties need to be ascertained. This study shows that the presence of two superposed polymer networks, where gelatin is not additionally crosslinked resulted in higher uptake and slower release of vitamin B₁₂. In the presence of gelatin, the stress is found higher for the same level of compressive deformation, and the permeability of the pore fluid during expulsion under compressive stress is found significantly lower. Also, a large residual strain at the end of each cycle in case of cyclic compression is observed, when gelatin is present. A microfluidic device is used to introduce voids uniformly across the blended gel with an objective to increase compressibility, permeability (for faster equilibration of pore pressure), and uptake of bioactive species. The results showing lower permeability and higher uptake in the presence of gelatin are discussed.     

Radioprotective effects of diltiazem on cytogenetic damage and survival in gamma ray exposed mice

Diltiazem, a calcium ion channel blocker, already in use in cardiovascular therapeutics, has been observed to protect against bone marrow damage (cytogenetic damage, cell death) and mortality in whole body irradiated mice. The micronuclei fraction in bone marrow cells of whole body irradiated (60Co gamma rays, 2.0 Gy) mice was reduced from 2.24 +/- 0.23% to about 0.74 +/- 0.33% by preirradiation administration (-20 min) of 110 mg/kg body wt. diltiazem (ip). Endogenous colony forming unit counts in spleen of mice administered 110 mg/kg body wt. (-20 min) of diltiazem before 10 Gy whole body irradiation were 6 times more than untreated irradiated controls. Pretreatment with diltiazem accelerated the recovery of radiation induced weight loss also. Diltiazem (110 mg/kg body wt, -20 min) enhanced 30 day survival to about 95% and 85% after lethal whole body absorbed dose of 9 and 10 Gy respectively and also mitigated radiation induced life- span shortening. Post-irradiation (10 Gy) administration of diltiazem (+20 to 30 min) enhanced survival from about 2 to 15% only but was highly significant (P < 0.001). Possible modes of radioprotective action of diltiazem have been discussed.     

In situ photoacoustic spectroscopic studies on heterogeneous catalysts under conditions of gas flow

An all-glass open photoacoustic cell through which gases can be passed without affecting the signal has been described. The cell has been characterized for various chopping frequencies and temperatures. Several heterogeneous catalytic reactions have been studied under conditions of gas flow at elevated temperatures and the potential application of this method in the field of heterogeneous catalysis has been pointed out. Communication No. 428 from the Solid State and Structural Chemistry Unit.