Publications (2)1.29 Total impact
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Article: The enhancement of the mechanical properties of a high‐density polyethylene
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ABSTRACT: This paper describes the process optimization in injection molding of high-density polyethylene (HDPE). Both conventional injection molding and shear controlled orientation (SCORIM) were employed in processing. The process optimization was based on design of experiments and complemented with analysis of variance. Mechanical characterization was carried out by tensile testing. Wide-angle X-ray diffraction and differential scanning calorimetry were used for the structural characterization of the moldings. High-density polyethylene exhibits 7.2 GPa Young's modulus and 155 MPa of ultimate tensile strength following the application of SCORIM processing. These results account for a fourfold increase in Young's modulus and a fivefold increase in ultimate tensile strength compared to conventional injection molding. The maintenance of toughness while enhancing stiffness and strength of the SCORIM moldings is attributable to an oriented morphology developed during shear flow, i.e., shish-kebab structure. The frequency of shearing action has the strongest influence on the morphology development. It is also demonstrated that the studied parameters are very much interdependent. It is possible to achieve substantial gains in mechanical properties of HDPE in SCORIM processing without causing a substantial increase in cycle time. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2473–2483, 1999Journal of Applied Polymer Science 09/1999; 73(12):2473 - 2483. · 1.29 Impact Factor -
Article: Chemical modification of starch based biodegradable polymeric blends: effects on water uptake, degradation behaviour and mechanical properties
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ABSTRACT: The main disadvantages of biodegradable polymers obtained from renewable sources are their dominant hydrophilic character, fast degradation rate and, in some cases, unsatisfactory mechanical properties particularly under wet environments. One possible solution to this problem is to reduce the water-uptake ability of these materials and to enhance the respective mechanical behaviour by chemical modification. In this work, three based starch blends with: (i) a copolymer of ethylene and vinyl alcohol (SEVA-C), (ii) cellulose acetate (SCA), and (iii) poly-ε-caprolactone (SPCL); were chemically modified by chain crosslinking. This modification is based on the reaction between the starch hydroxyl groups and tri-sodium tri-meta phosphate. The obtained compounds were characterized by FTIR and the respective properties were assessed and compared to the original materials by means of the hydration degree, the degradation behaviour, contact angle measurements and mechanical testing. The results show that the water-uptake of these blends could be reduced up to 15% and that simultaneously stiffer materials with a less pronounced degradation rate can be obtained.Polymer Degradation and Stability.
