No abstract

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. Lichtenecker) of 0-3 composites. In order to assess the correlation of the experimental data with the theoretical models, the experimental data obtained from PZT/PA composites were also included.Confidential: not for distribution.

The extensive utilization of rubber in a wide variety of products causes a problem in terms of waste. Reclaiming of end-of-life products or production scrap is a potential solution. A high quality reclaim would preferably be obtained by devulcanization, to leave the polymer chains intact. Reclaiming of natural rubber is common practice, although the fundamental knowledge about de- and re-crosslinking is rather limited. EPDM-based rubber is even more unexplored in terms of reclaiming and re-utilization. This paper gives a mechanistic insight into the thermal reclaiming of two differently vulcanized EPDM compounds, using hexadecylamine (HDA) as devulcanization agent. Reclaim from conventionally vulcanized EPDM, mainly polysulfidic of nature, shows the largest decrease in remaining crosslink density with increasing HDA concentration and at lower reclaim temperatures. After reclaiming at the lower limit of the experimental temperature window applied: 225 °C, the concentration of remaining di- and polysulfidic crosslinks is higher than the concentration of monosulfidic bonds, while at the upper temperature level: 275 °C, the concentration of monosulfidic bonds is highest. For efficiently vulcanized EPDM with primarily monosulfidic crosslinks, HDA again has a positive effect on the reclaim efficiency at low applied reclaiming temperatures of max. 225 °C. At higher temperatures, the crosslink density increases with increasing concentrations of HDA. Application of a treatment proposed by Horikx shows, that conventionally vulcanized EPDM devulcanizes to a larger extent by crosslink scission compared to the efficiently vulcanized material, which primarily shows main-chain scission. Both reclaimed materials can be added up to 50 wt% to a virgin masterbatch, with limited decrease in properties. This is a high amount compared to max. 15 wt% of ground powder rubber, commonly known to be the practical limit.

No abstract

Disc type reinforced piezoelectric composite bimorphs with series connection were designed and the performance was investigated. The composite bimorphs (PZT/PA and PZT/PDMS (40/60 vol%)) were successfully fabricated by a compression molding and solution casting technique. The charge developed at an applied force of 150 N is 18150 pC (PZT/PA) and 2310 pC (PZT/PDMS), respectively. Electric force microscopy (EFM) is used to study the structural characterization and piezoelectric properties of the materials realized. A clear inverse piezoelectric effect was observed when the bimorphs were subjected to an electric field stepped up through 2, 6 and 10 V, indicating the net polarization direction of the different ferroelectric domains. The as-developed bimorphs have the basic structure of a sensor and actuator, and, since they do not use any bonding agent for bonding, they can provide a valuable alternative to the present bimorphs where bonding processes are required for their realization that can limit their application at high temperature.