All issues / Volume 3 (2009) / Issue 4 (April)
This is an editorial article. It has no abstract.
In order to explore the possibility of substituting an unrefined biodiesel coproduct stream (BCS) for refined glycerol as a polymer plasticizer we have prepared cast gelatin films plasticized with a simulated BCS, i.e., mixtures of glycerol and some of the typical components found in BCS (methyl linoleate, methyl oleate, linoleic acid, and oleic acid). We measured the tensile properties as a function of plasticizer composition, and analyzed the specific effect of each individual component on tensile properties. We found that it is the unrecovered alkyl esters that largely determine the tensile properties, and that BCS can be successfully used to plasticize cast gelatin films as long as the BCS contains 11 parts by weight, or less, of unrecovered alkyl esters per 100 parts glycerol.
Optimization of chlorpheniramine maleate (CPM) delivery by response surface methodology – four component modeling using various response times and concentrations of chitosan-alanine, glutaraldehyde and CPM
K. Kumari, K. Prasad, P. P. Kundu
Vol. 3., No.4., Pages 207-218, 2009
Vol. 3., No.4., Pages 207-218, 2009
The aim of the current study was to investigate the effects of formulation variables on the release of drug and to optimize the formulation of chitosan-alanine beads loaded with chlorpheniramine maleate (CPM) for controlled release using response surface methodology (RSM). Drug loaded beads of chitosan-alanine were prepared and crosslinked by using glutaraldehyde as crosslinker. The release behavior of drug was affected by preparation variables. A central composite design was used to evaluate and optimize the effect of preparation variables; chitosan concentration (X1), percentage of crosslinker (X2), concentration of drug (X3) and release time (X4) on the cumulative amount of drug release, Y in solutions of pH = 2.0 and pH = 7.4, respectively. The influence of each parameter was studied by factorial design analysis. Analysis of variance (ANOVA) was also used to evaluate the validity of the model. The statistical parameters reveal strong evidence that the constructed models for drug release in pH = 2 and pH = 7.4 are reliable.
In this work, the formation of semiconductive Sb2S3 nanoparticles inside amorphous polystyrene has been achieved by thermal degradation of the corresponding antimony dodecyl-mercaptide, Sb(SC12H25)3. The thermolysis of the dodecyl-mercaptide precursor was studied as both pure phase and mercaptide solution in polystyrene. The thermal decomposition of the antimony mercaptide precursor at 350°C, under vacuum, showed the formation of a mixture of antimony trisulfide (stibnite, Sb2S3) and zero-valent antimony (Sb) phase. X-ray Powder Diffraction (XRD) and Rietveld analysis carried out on the obtained nanostructured powder confirmed the presence of Sb and Sb2S3 phases in 10.4 wt% and 89.6 wt% amount, respectively. The same pyrolysis reaction was carried out in the polymer and the resulting nanocomposite material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS spectroscopy, and fluorescence spectroscopy. The nanocomposite structural characterization indicated the presence of well-dispersed nanoclusters of antimony and stibnite (15–30 nm in size) inside the amorphous polymeric phase. Optical measurements on the obtained nanocomposite films showed a strong emission at 432 nm upon excitation at 371 nm, probably related to the presence of Sb2S3 nanoclusters.
Effect of electron beam irradiation and poly(vinylpyrrolidone) addition on mechanical properties of polycaprolactone with empty fruit bunch fibre (OPEFB) composite
N. A. Ibrahim, S. N. A. Ahmad, W. M. Z. W. Yunus, K. Z. M. Dahlan
Vol. 3., No.4., Pages 226-234, 2009
Vol. 3., No.4., Pages 226-234, 2009
Biodegradable composites or green composites were prepared by melt blending technique using polycaprolactone and oil palm empty fruit bunch fibre (OPEFB). Since OPEFB is not compatible with PCL a binder, poly(vinyl pyrrolidone), (PVP) was used to improve the interaction between PCL and OPEFB. The composites produced were irradiated using electron beam to improve the mechanical properties. The tensile, flexural and impact strengths of PCL/OPEFB composites were improved by addition of 1% by weight of PVP and irradiated with 10 kGy of electron beam. The FTIR spectra indicate a slight increase of frequencies at C=O peaks from 1730 to 1732 cm–1 after irradiation indicates some interaction between C=O and O–H. The surface morphology of the facture surface obtained from tensile test shows no fibre pull out indicating good adhesion between the OPEFB and PCL after addition of PVP.
Binary and ternary composites of recycled poly(ethylene terephtalate) (rPET), short glass fibres (SGF) and/or impact modifier (IM) were prepared by melt compounding and injection moulding. SEM images of rPET/IM fracture surfaces indicated that IM particles of about 1–2 µm in diameter were uniformly distributed in the rPET matrix, but with a poor adhesion level. Microphotographs of PET/SGF composites evidenced brittle fracture proceeding through the matrix and strong adhesion between components. In ternary composites SGF were evenly distributed, while IM particles were no longer detectable. Tensile creep of rPET and prepared composites was investigated under short and long term testing conditions at various stress levels. Main part of the tensile creep corresponded to the elastic time-independent component, while the timedependent component was rather limited even at relatively high stresses. While SGF accounted for a significant decrease in the overall creep compliance, the incorporation of IM induced a small decrease in the compliance and a non-linear viscoelastic behavior. In ternary composites, the reinforcing effects of SGF was dominating. Under a constant stress, the logarithm of compliance grew linearly with the logarithm of time. The creep rate, which resulted to be generally very small for all tested materials, was slightly reduced by SGF and increased by IM.
Research on polymer-layered silicate nanocomposites is currently an expanding field of study because they exhibit a wide range of improved properties over their unmodified starting polymers. Polyamide 6 (PA6)/organoclay nanocomposites have been prepared by exfoliating the organoclay montmorillonite via melt mixing. The exfoliation within the nanocomposites has been monitored using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Water absorption of PA6 nanocomposites and its mechanical performance when saturated with water at temperatures ranging from 40 to 60°C were investigated. It was found that the organoclay up to 8 wt% was completely exfoliated and well distributed within PA6 matrix as observed by TEM and XRD analysis. Addition of organoclay did not affect the crystallinity of PA6, and better mechanical performances were obtained. It was found that the barrier properties of the neat PA6 exhibited both higher diffusion coefficient and higher maximum water uptake as compared to the filled polymer. For all investigated temperatures the diffusion coefficient was found to decrease as function of organoclay loading. However, the maximum uptake was found to increase without reaching that of neat PA6. A relationship between temperature and diffusion coefficient was also established.
The goal of this work was to apply several zinc chelates as activators for sulphur vulcanization of acrylonitrilebutadiene elastomer (NBR), in order to find alternatives for the conventionally used zinc oxide. In this article, we discuss the effects of different zinc complexes on the cure characteristics, crosslinks distribution in the elastomer network and mechanical properties of acrylonitrile-butadiene rubber. Zinc chelates seem to be good substitutes for zinc oxide as activators for sulphur vulcanization of NBR rubber, without detrimental effects on the crosslinking process and physical properties of the obtained vulcanizates. Moreover, application of zinc complexes allows to reduce the amount of zinc ions in rubber compounds by 40% compared to conventionally crosslinked vulcanizates with zinc oxide. It is a very important ecological goal since zinc oxide is classified as toxic to aquatic species and its amount in rubber products must be reduced below 2.5% at least. From a technological point of view it is a very important challenge.