Abstracts of the VKRT meetings of Plastic and Rubber sector      

  

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Abstract of Lezingenmiddag, WICC - 2001     2001

Hi Tech multifunctional additives - high performance with mall dosages

The use of processing additives in the various steps of rubber processing has a long traditon. Well known effects like improved filler dispersion, better blending of polymers, fast and smoother extrusion etc. are highly welcome, but there is concern about possible adverse effects in the finished article.

Consequently a series of high performance multifunctional additives has been developed and tested. The goal was to overcome several processing problems with minimum impact on cured properties. Dependping on the polymer/filler/curative system effects like improved filler dispertion, better extrusion and better mould release can be obtained using just one additive.

In "difficult" polymers like FKM it is possible to improve the flow properties and reduce mould fouling with additive dosages lower than 1 phr.

The HT-additives give sigificant improvements of various processing charateristics with less impact on compression set.

For the whole series the infuences on cured properties was carefully evaluated. Generally lower dosages result in less influence on the crosslink density of the rubber matrix. Normally, no fller level correction is required when Hi Tech multifunctional additives are used.
During the investigation an interesting effect in tensile testing was found.

Many promising developments in rubber compounding have been cancelled in the past because of an undesired drop of the modulus in the presence of detergent type processing additives.

Non Black Fillers and Combinations of Carbon Black and Non Black Fillers in EPDM Rubber

The main part of EPDM is used in extrusion. For non black filled compounds it is difficult to get good results in extrusion. Both, surface quality and productivity in extrusion may be improved by the use of Neuburg Siliceous Earth. In the present paper the results of a comparative study are discussed. Mechanical values, hot air ageing results and qualitative as well as quantitative results in extrusion of a variety of compounds filled with non black fillers are presented.
In the second part of the paper combinations of carbon black with a choice of non black fillers are discussed. Particularly in profiles for automobiles it is imperative to reduce electrical conductivity. This may be obtained either by the use of high priced carbon blacks or combinations of carbon black with mineral fillers. Here also Neuburg Siliceous Earth helps to improve extrudability and to reduce raw material costs without modifying too much mechanical properties.

Optimal Filler Choice for Radiator Hoses according to Volkswagen TL 52361

The Volkswagen Norm TL 52361 requires extremely high material performances for low temperature flexibility and for resistance to heat, oil cooling liquids and ozone. With respect to possible electrochemical corrosion a high electrical resistivity is additionally required. The use of an insulating filler is necessary for this reason. In the present paper the influence of Aktisil VM 56 (a vinylsilane coated version of Neuburg Silicious Earth) on material properties related to the requirements of Volkswagen TL 52361 was investigated. Particularly the combination of Aktisil VM 56 with the carbon black Durex O fulfills the requirements for the inner layer and forms a basis for an optimization of the material for the outside layer.

Vulcuren KA 9188 - A New Possibility to Improve Productivity and Performance of Rubber Vulcanizates

Improved productivity or improved performance of rubber articles are a challenge for all compounders. One possibility to improve productivity is to increase the vulcanization temperature to reduce vulcanization time, but this has normally a strong negative effect on rubber properties due to changes in the crosslink density and crosslink structure. These alteration of sulphur crosslinks is known as reversion and occurs also during service at elevated temperatures or under anaerobic conditions, i.e. long cure times at high temperatures. A reduction or elimination of reversion in vulcanisates, particularly NR vulcanisates, has beside economic advantages also technical advantages in that service life of tyres running under severe conditions can be extended.
Thiol-amine swelling technique for the determination of crosslink density and sulphur crosslink strucrure and model vulcanization with 2,3-dimethylbutene-2 (DMB) as a model was used to show that 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexan (Vulcuren