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Herrmann V.,Studiengang Kunststoff und Elastomertechnik | Nass F.,Hochschule fur Angewandte Wissenschaften | Lemmich S.,Hochschule fur Angewandte Wissenschaften | Wachter F.,Hochschule fur Angewandte Wissenschaften
Gummi, Fasern, Kunststoffe | Year: 2013

Cure time reductions being enabled by a injection press equipped with an EFE system were evaluated on the basis of a thick-walled rubber cylinder. Different procedures (based on cure kinetics and cure simulation) were used for the calculations needed. Depending on how the cure time reduction was determined, the resulting reductions amounted from 40 to 50 % for the maximum throttle position disregarding the quality of the cylinders. However, a detailed inspection of the cylinders revealed bubbles in the centre of the part for the cure times tested. When calculating the cure time reductions taking the common safety margins into account the reduction decreases for a small percentage. NMR imaging of the cross section of the samples indicates the crosslink density gradient within the cylinders. It could be clearly shown that using the throttle of the EFE system allows both the cure time reduction and the opportunity to adjust a more uniform crosslink density profile within the cylinder. This was verified by cutting the cylinders and measuring the hardness of the inner and outer sections. In addition to that the effect of a decreasing surface reversion of a sul phur crosslinked natural rubber part is being discussed. Source


Herrmann V.,Studiengang Kunststoff und Elastomertechnik | Nass F.,Studiengang Kunststoff und Elastomertechnik | Lemmich S.,Studiengang Kunststoff und Elastomertechnik | Wachter F.,Studiengang Kunststoff und Elastomertechnik | Hartel V.,Hochschule fur Angewandte Wissenschaften
Gummi, Fasern, Kunststoffe | Year: 2013

In addition to the studies presented in the first part the second part at hand deals with the production of cylinders depending on the throttle position of the EFE system having been used and the practically relevant investigation of their proper functioning. Apart from testing the mechanical properties the focus has been on verifying the absence of bubbles in the centre of the article. The maximally attainable cure time reductions have been determined for different production parameters (mould temperature, injection speed). Depending on these parameters cure time reductions up to 41 % can be achieved. However, additional NMR investigations revealed, that especially for lower cure time reductions (< 25 %) more uniform crosslink density profiles over the cross section of the part can be obtained. Major cure time reductions by adjusting the throttle position are to the disadvantage of a more homogeneous crosslink density profile, although changes in mechanical properties have not yet been observed. This will be the object of the third part of the investigation, still to follow. Source


Herrmann V.,Studiengang Kunststoff und Elastomertechnik | Nass F.,Studiengang Kunststoff und Elastomertechnik | Lemmich S.,Studiengang Kunststoff und Elastomertechnik | Wachter F.,Studiengang Kunststoff und Elastomertechnik | Riedelbauch H.,Studiengang Kunststoff und Elastomertechnik
Gummi, Fasern, Kunststoffe | Year: 2013

Following the investigations of the cure time reductions, part 1 and 2 of the present study, the third part focuses on how the throttle influences selected properties of the cylinders being produced. The additional shear energy for the maximal throttle effect has been found to be 0.03 kWh/kg. In comparison to the shear energy being generated during mixing in an internal mixer a mastication of the natural rubber is scarcely to be expected when the compound passes the throttle. However, with the throttle being in operation a weak influence of the shear forces on the dispersion of the elements silicon and aluminium has been found implying a better dispersion of the kaolin filler. Regarding the element sulphur a slightly improved dispersion could be detected in one case related to the use of the throttle. In general no effect of the throttle on quasistatic (compression, hysteresis, relaxation) as well as on dynamic mechanical (complex modulus, damping factor) properties could be found for all tests and this being independent of the type of carbon black used. Source

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