Results 1 - 10 of 3023
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[en] Highlights: • A new process to produce flax/PP tape for AFP is described, using calendering between rollers. • Microstructure analysis shows surface polymer and good impregnation. • AFP forming process allows manufacture of temperature sensitive natural fibres. • Mechanical properties comparable to those for compression moulded plate specimens. Automated fibre placement (AFP) has been used to manufacture flax/polypropylene biocomposites for the first time. This required preparation of tape with a calibrated width from impregnated fibre sheets. The unidirectional tapes showed polymer-rich zones on the surface. During manufacture the polypropylene (PP) is melted locally with a laser. A consolidation step in a hot press is then required to reduce void content. The flax fibres, composed of polysaccharides, have limited thermal resistance so optimization of the thermal cycle is necessary, but subsequent characterization of mechanical behaviour showed no evidence of property loss in spite of an additional melting cycle. AFP appears to be a promising manufacturing method for biocomposites.
[en] To compare quality of scar after subcuticular stitches between Polypropylene (Prolene), a non-absorbable suture, with Polyglactin 910 (Vicryl), an absorbable suture after thyroid surgery. Study Design: Randomized controlled trail (RCT). Place and Duration of Study: Department of Surgery Combined Military Hospital and Military Hospital Rawalpindi from 1 Jan 2007 to 31 Dec 2007. Material and Methods: Sixty patients undergoing elective thyroid surgery were included and randomly divided into two groups using random number tables. Informed written consent was obtained from each patient. The neck wound was closed by subcuticular suturing technique and the suture material was used according to the sampling technique. The patients were followed up in OPD on tenth post operative day and twelve weeks after surgery for the quality of scar. Results: After 10 days, 1 patient in each of the Polypropylene group (3.3%) and Polyglactin 910 group (3.3%) had a bad scar (p = 1.000). After twelve weeks of surgery, 2 patients in the Polypropylene group (6.7%) and 3 patients in the Polyglactin 910 group (10.0%) had bad scars (p = 1.000). Conclusion: There is no significant difference between the frequency of bad scar formation in the Polypropylene and Polyglactin 910 group. It is thus recommended that absorbable Polyglactin 910 sutures should be used for wound closure after thyroid surgery as it does not require suture removal and thus prevents patient anxiety and discomfort and also saves surgeon and staff's time. (author)
[en] During the last few years several research groups have focused on the fabrication of artificial gecko inspired adhesives. For mimicking these structures, different polymers are used as structure material, such as polydimethylsiloxanes (PDMS), polyurethanes (PU), and polypropylene (PP). While these polymers can be structured easily and used for artificial adhesion systems, the effects of repeated adhesion testing have never been investigated closely. In this paper we report on the effect of repeated adhesion measurements on the commercially available poly(dimethylsiloxane) polymer kit Sylgard 184 (Dow Corning). We show that the adhesion force decreases as a function of contact cycles. The rate of change and the final value of adhesion are found to depend on the details of the PDMS synthesis and structuring.
[en] An adult male had a penetrating injury of the chest resulting in cardiac tamponade. The injury resulted as a consequence of a detached iron piece from an iron bar in a steel mill. Emergency sternotomy and percardiotomy revealed blood in the pericardial cavity and full thickness penetration of the right ventricle. The defect was repaired following the removal of the iron fragment. Postoperative recovery was uneventful. (author)
[en] It was found that, using Kocosol 150 solution of Alamine 336(tri-capryl amine) as a mobile carrier of reactive liquid membrane supported in porous polypropylene film (Celgard 2500), the concentration of uranium from acidic aqueous solution to Na2CO3-buffered alkaline stripping solution could be achieved by the carrier-mediated facilitated transport process. The effects of concentration of uranium and pH in feed solution and carrier concentration in liquid membrane on the flux of uranium were discussed by the proposed mechanism and assumptions and the derived theoretical equation. (Author)
[en] Study of drawn fibres prepared from an isostatic polypropylene modified by an ethylene aminoalkylacrylate copolymer has been done using the broad line of 1H NMR. NMR spectra were measured on the set of fibres prepared with a draw ratio λ from 1 to 5.5 at two temperatures, one of them corresponding to the onset of segmental motion and the other one is the minddle of the temperature interval as determined by decrease of the second moment M2. Decomposition of the spectra into elementary components related to the amorphous, intermediate and crystalline regions of partially crystalline polymers has been made. The drawing of the fibres was found to enhance the chain mobility in the amorphous region and to restrain the molecular motion in the intermediate region. Such behaviour well supports conclusions predicted in the earlier study based on the spin-lattice relaxation time T1 and dynamic mechanical data treated using the WLF theory. (Authors)
[en] Gamma radiation degradation of an ethylene-propylene copolymer crosslinked and added with an antioxidant has been studied by IR spectroscopy. The well evidenced irradiation effects are the absorbance changes in the 300-3700 cm-1 and 1650-1700 cm-1 regions that are usually ascribed to the stretching of -OH and C=O respectively. Quantitative estimations of the C=O integrated absorbance band at different conditions have been obtained in previous papers. In this paper the irradiation effects on the 300 cm-1 region have been analyzed and appeared to consist of two different components. The behavior of the 3300-3600 cm-1 region as a function of atmosphere, dose rate, absorbed dose, at different percentage of antioxidant and of the irradiation experimental conditions has been quantitatively studied