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All issues / Volume 1 (2007) / Issue 1 (January)

J. Karger-Kocsis, T. Czigany
Vol. 1., No.1., Pages 1-1, 2007
DOI: 10.3144/expresspolymlett.2007.1
Interfacial effects in nano-silica/polypropylene composites fabricated by in-situ chemical blowing
L. F. Cai, Y. L. Mai, M. Z. Rong, W. H. Ruan, M. Q. Zhang
Vol. 1., No.1., Pages 2-7, 2007
DOI: 10.3144/expresspolymlett.2007.2
By mixing macromolecular blowing agent grafted nano-SiO2 with polypropylene (PP) melt, the nanoparticle agglomerates can be pulled apart due to the in-situ bubble-stretching resulting from gasification of the side foaming groups on the grafted polymer. The present work evaluated the interfacial effect in the PP based nanocomposites prepared using the aforesaid technique through introducing rubbery components to the backbone of the grafted polymer chains. The results indicated that deagglomeration of the nanoparticles was not bound to yield the highest properties of the composites. The positive effect of the nanoparticles was brought into full play because of the joint contributions of particles dispersion status and interfacial interaction. An interlayer with proper flexibility ensured an overall enhancement of mechanical properties, especially impact strength, of the nanocomposites.
Effect of blend ratio on aging, oil and ozone resistance of silica-filled chloroprene rubber/natural rubber (CR/NR) blends
P. Sae-oui, C. Sirisinha, K. Hatthapanit
Vol. 1., No.1., Pages 8-14, 2007
DOI: 10.3144/expresspolymlett.2007.3
The effect of blend ratio on properties of chloroprene rubber/natural rubber (CR/NR) blends was investigated. In addition to the mechanical properties, attention was also given to the resistance to thermal aging, oil and ozone of the blends. Silica was selected as a reinforcing filler in this study due to its unique characteristic to interact with CR. The results reveal that, due to the better filler dispersion and the greater crosslink density, the silica-filled CR possesses lower compound viscosity and better mechanical properties, compared to the silica-filled NR. The aging properties, oil and ozone resistance of the silica-filled CR are also significantly better than those of the silica-filled NR. The mechanical properties and the resistance to degradation of the silica-filled CR/NR blends are mainly governed by the blend morphology. It is found that good mechanical properties in association with adequately high resistance to degradation from thermal aging and oil are obtained when CR remains the matrix in the blends. Even though the ozone cracks are found in all blends, a thorough look at the results reveals that considerable improvement in ozone resistance is achieved with increasing CR content.
A continuum damage model to simulate failure in composite plates under uniaxial compression
D. Tumino, F. Cappello, G. Catalanotti
Vol. 1., No.1., Pages 15-23, 2007
DOI: 10.3144/expresspolymlett.2007.4
Experimental investigations and numerical simulations are performed in order to numerically predict the buckling behaviour of thin composite laminated specimens. Experiments are aimed at two objectives: the first is to completely characterize the carbon/epoxy material under simple loading configurations, the second is to test this material in buckling and post-buckling situations. The data collected with the first campaign of experiments are used to obtain the strength parameters required to define a damage model based on the failure theory by Tsai-Wu. This model is implemented in a Finite Element (FE) code and numerical simulations of buckling are executed for unidirectional and cross-ply laminates; results are in good agreement with experiments both in terms of determination of the critical loads and prediction of failure during post-buckling.
Cyclic polyesters prepared by poly(oxypropylene oxymaloyl) ring-chain reactions
M. I. Ferrahi, M. Belbachir
Vol. 1., No.1., Pages 24-26, 2007
DOI: 10.3144/expresspolymlett.2007.5
The synthesis of cyclic polyesters of poly(oxypropylene oxymaloyl) from a ring-chain reaction was carried out at 40°C with 'Maghnite' an acid exchanged montmorillonite as acid solid ecocatalyst (Mag–H+). 'Maghnite' is already used as catalyst for polymerization of many vinylic and heterocyclic monomers [1]. The effect of amount of catalyst on yield and molecular weight of polymer was studied.
A typical reaction product was analyzed by gel permeation chromatography (GPC) as well as by nuclear magnetic resonance spectroscopy (1H-NMR) and the existence of cyclic species was proven.
On the friction and sliding wear of rubber/layered silicate nanocomposites
K. G. Gatos, K. Kameo, J. Karger-Kocsis
Vol. 1., No.1., Pages 27-31, 2007
DOI: 10.3144/expresspolymlett.2007.6
The dry sliding and friction behaviors of organoclay modified hydrogenated nitrile (HNBR) and ethylene/propylene/diene (EPDM) rubbers were studied using a pin (steel)-on-plate(rubber sheet) test configuration. It was found that the organoclay modification may improve or deteriorate the resistance to wear of rubbers. The resistance to wear was adversely affected by pronounced intercalation/exfoliation and two-dimensional alignment of the clay layers (i.e. normal to the moving pin). This result is in analogy with the directional dependence of the wear performance of fiber-reinforced composite laminates.
Surface properties of latex film and solvent-borne film resulted from fluorinated acrylate copolymers prepared by emulsion polymerization
W. Zhang, H. G. Ni, X. P. Wang
Vol. 1., No.1., Pages 32-36, 2007
DOI: 10.3144/expresspolymlett.2007.7
The fluorinated acrylate copolymer, poly (BMA-co-DFHMA), was prepared by emulsion polymerization using a preemulsified monomer addition process. The FTIR and 1H –NMR were used to characterize the copolymer structure. The contact angle of water on the solvent-borne film increased dramatically and reached an equilibrium value (103°) when the PDFHMA content in the copolymer was only 0.97 mol%. However, the contact of water on the latex film increased slowly, and reached the equilibrium value of 99° until the fluorinated component content was as highly as 9 mol%. A similar result was observed for the oil contact angle on the two types of films. XPS results showed that when the F/C ratio on film surfaces reached equilibrium, the required content of fluorinated component in the copolymer for the solvent-borne film was much lower than that for the latex film.
Application of percolation model on the brittle to ductile transition for polystyrene and polyolefin elastomer blends
Z. Guo, Z. Fang, L. Tong
Vol. 1., No.1., Pages 37-43, 2007
DOI: 10.3144/expresspolymlett.2007.8
The percolation model was applied in the study of brittle to ductile transition (BDT) of polystyrene (PS) and polyolefin elastomer (POE) blends. Based on the interparticle distance and percolation model, stress volume (Vs) can be expressed by volume fraction (Vr) and ratio of the diameter of stress volume and the diameter of the domain (S/d). The percolation threshold (Vsc) varied from π/6 to 0.65. From the results of the Charpy impact strength of the blends, the percolation threshold for the brittle to ductile transition of PS/POE blend is 14 wt% POE, corresponding to Vsc~0.5, which is consistent with the calculated value of π/6. Morphology observations show that the percolation point is correlated with the phase inversion of the blend.
Miscibility and specific interactions in blends of poly[(styrene)-co-(cinnamic acid)] with poly(methyl methacrylate) and modified poly(methyl methacrylate)
N. Bouslah, F. Amrani
Vol. 1., No.1., Pages 44-50, 2007
DOI: 10.3144/expresspolymlett.2007.9
The miscibility behavior of poly(styrene-co-cinnamic acid) (PSCA) with poly(methyl methacrylate) (PMMA), poly[(methyl methacrylate)-co-(4-vinylpyridine)] (PMMA4VP) and poly[(methyl methacrylate)-co-(2-vinylpyridine)] (PMMA2VP) was studied. DSC measurements indicated that PSCA23 containing 23 mol% of carboxylic acid units was miscible with PMMA, PMMA2VP and PMMA4VP as established from the observation of a single composition dependent glass transition temperature. Miscibility was induced via hydrogen bonding as evidenced by IR frequency shifts of the hydroxyl stretching vibrations of the acid copolymer in the blends. Interpolymer hydrogen bonding formation within the binary systems was also investigated by viscosimetric study of dilute solutions in toluene. For PMMA/PSCA5 blends the viscosity of the mixtures was close to the weight average viscosities of the individual polymer while for blend solutions of PSCA5 with PMMA2VP and PMMA4VP, the interactions were sufficiently strong to form interpolymer complexes with a decrease in viscosity in comparison to the additivity rule.
Peroxydisulfate initiated synthesis of potato starch-graft-poly(acrylonitrile) under microwave irradiation
V. Singh, A. Tiwari, S. Pandey, S. K. Singh
Vol. 1., No.1., Pages 51-58, 2007
DOI: 10.3144/expresspolymlett.2007.10
Potato starch-graft-poly(acrylonitrile) could be efficiently synthesized using small concentration of ammonium peroxydisulfate (0.0014M) in aqueous medium under microwave irradiation. A representative microwave synthesized graft copolymer was characterized using Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy and Thermogravimetric Analysis. Under microwave conditions oxygen removal from the reaction vessel was not required and the graft copolymer was obtained in high yield using very small amount of ammonium peroxydisulfate, however using the same amount of ammonium peroxydisulfate (0.0014M) on thermostatic water bath no grafting was observed up to 98°C (even in inert atmosphere). Raising the concentration of the initiator to 0.24 M resulted into 10% grafting at 50 °C but in inert atmosphere.
The viscosity/shear stability of the grafted starch (aqueous solution) and water/saline retention ability of the microwave synthesized graft copolymer were also studied and compared with that of the native potato starch.
Published by:

Budapest University of Technology and Economics,
Faculty of Mechanical Engineering, Department of Polymer Engineering