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DCP Concentration (dcp + concentration)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Preparation and properties of heat-shrinkable cross-linked low-density polyethylene

ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2003
J. Morshedian
Abstract In this work, heat-shrinkable characteristics of a polyethylene compound were obtained by blending mixtures of low-density polyethylene with varying amount of peroxide. These were then extruded and molded to the required shape and then cross-linked by chemical means, followed by heating and stretching and then cooled to "freeze-in" the oriented polymer structure (elastic memory). A decrease in the melting point and heat of fusion (,Hf), as determined from the DSC melting enthalpies, was observed with an increase in the dicumyl peroxide (DCP) concentration. Tests on the heat shrinkablity of the samples showed that the stretching temperature has a large effect on the shrinkage temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. The elongation at break decreased with an increase in the DCP concentration. Increasing the temperature in lightly cross-linked samples (low percent DCP) resulted in a reduction in the elongation at break. Increasing the cross-linking density (DCP content) gave an opposite effect. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 112,119, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10041 [source]

Tailoring viscoelastic and mechanical properties of the foamed blends of EVA and various ethylene-styrene interpolymers

POLYMER COMPOSITES, Issue 3 2003
I-Chun Liu
Foamed materials (EVA/ESI) have been prepared from blends of ethylene-vinyl acetate copolymer (EVA) and ethylene-styrene interpolymers (ESI) in the presence of various amounts of dicumyl peroxide (DCP). Four ESIs of different compositions were employed in this study; their styrene contents ranged from 30 to 73 wt% and their Tg ranged from ,2 to 33°C. It has been found that microcellular morphology, degree of crosslinking and expansion ratio were strongly affected by the DCP concentration and the type of ESI employed. A minimum degree of crosslinking was required for making good foams and the same degree of crosslinking could be achieved by employing a smaller amount of DCP for an EVA/ESI blend having a higher styrene content. In contrast to other EVA blends, such as EVA/LDPE, these EVA/ESI blends exhibited no existence of any optimum DCP concentration, and the , glass transition temperatures of the foams varied with the ESI type, covering a wide span from 0°C to 37°C. Therefore, it was possible to tailor the Tg of an EVA/ESI blend by choosing an appropriate type of ESI. Furthermore, by correctly tailoring the Tg, the EVA/ESI foam could be made into a rubbery material with a custom-designed damping factor. Tensile strength and modulus of the EVA/ESI foams increased generally with an increase in the styrene content, with the exception that ESIs with very low styrene content will confer on the blend a high modulus at small strain and a large elongation at break. [source]

Grafting of maleic anhydride onto linear polyethylene: A Monte Carlo study

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2004
Yutian Zhu
Abstract Monte Carlo simulation was used to study the graft of maleic anhydride (MAH) onto linear polyethylene (PE-g-MAH) initiated by dicumyl peroxide (DCP). Simulation results revealed that major MAH monomers attached onto PE chains as branched graft at higher MAH content. However, at extremely low MAH content, the fraction of bridged graft was very close to that of branched graft. This conclusion was somewhat different from the conventional viewpoint, namely, the fraction of bridged graft was always much lower than that of branched graft under any condition. Moreover, the results indicated that the grafting degree increased almost linearly to MAH and DCP concentrations. On the other hand, it was found that the amount of grafted MAH dropped sharply with increasing the length of grafted MAH, indicating that MAH monomers were mainly attached onto the PE chain as single MAH groups or very short oligomers. With respect to the crosslink of PE, the results showed that the fraction of PE-(MAH)n -PE crosslink structure increased continuously, and hence the fraction of PE-PE crosslink decreased with increasing MAH concentration. Finally, quantitative relationship among number average molecular weight of the PE, MAH, and DCP contents was given. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5714,5724, 2004 [source]