Abstracts of the VKRT meetings of Plastic and Rubber sector      

  

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Abstract of Stretched Solutions for the Rubber Industry This seminar is a joint initiative of the Alpha Technologies, DSM Elastomers, TNO Industrial Technology, Rubber Technology Group University Twente and the VKRT      2004

How to (Re)solve analytical rubber problems?

DSM Resolve is the former analytical department of DSM Research in Geleen (NL). Plastics and rubber analysis is one of the major tasks. It is shown what is needed to be able to solve analytical rubber problems. Furthermore it is discussed -with practical examples- how small and big analytical problems with respect to rubber are tackled.

Influence of silica filler distribution on properties of tire rubber treads, as related to silica characteristics

Objective: Silica has grown substantially over the last decade as reinforcing filler for rubber tire treads, for reason of lower rolling resistance compared to carbon black reinforcement. So-called highly dispersible silicas are being used. The objective was to identify the primary silica characteristics, influencing the performance in tire treads. Experimental approach: The effect of rubber mixing conditions on macro- as well as on microdispersion of silica was studied, using conventional till highly dispersible silicas with different BET-surfaces and Structure. Macro-dispersion was studied by optical means, micro-dispersion with Atomic Force Microscopy (AFM). Summary of results: The macro- and microdispersion vary with difference in silica samples, particularly with various DBP-structures. Low structured silicas show poor macrodispersion, vs. medium structured/semi dispersible and very good microdispersion for highly structured/highly dispersible silicas. Microdispersion measurements show an increased level of primary silica particles for higher structured silicas, where these are primarily dispersed to the microdispersion level, with only 15-20% remaining in the macrodispersion regime. The dynamic mechanical properties of a tire tread primarily depend on the microdispersion level. Too large filler-filler interactions, causing poor dynamic mechanical properties, are mainly due to aggregates with a size over 600 nm. Also the tensile properties are primarily influenced by the presence of aggregates with diameters larger than 600 nm.

Rapid QA for Natural & Synthetic Polymers using the RPA

FT-Rheology has been proven to be a very sensitive tool for LCB quantification in polyolefins and commercially available elastomers such as EPDM's and BR's. This technique has been extended to NR gums from different origins. Large differences in LCB content have been measured on NR's from different countries as well of different plantations from the same country. These NR's with different LCB level have been mixed with Carbon Blacks (CB). It has been found the CB incorporation time depends more on LCB content than on viscosity. Higher level of LCB provides faster CB incorporation, consistent with previous knowledge for synthetic rubbers. In addition, it was shown that mastication can increase NR gums LCB content depending upon NR type although it decreases viscosity for all types. Mixing various origin NR

Rheological Meaurement & Control in the Rubber Factory

Traditionally, compound testing has taken place in centralized quality control laboratories, although this set-up usually imposes a delay in compound release due to the time required for sample transfer from the production line and test programming. Additional advantages have been recognized of moving the point of testing into the production area, where results can be generated more quickly and efficiently, and where production personnel are able to respond faster to the test data produced. Considerable benefits are derived from transferring compound control testing to the production line. Samples can be tested with less delay and a reduced labour requirement, while test results are obtained earlier, meaning faster release of compound, and earlier forewarning of quality trends and problems. Increasingly the value of more discriminating process data to give better control over downstream conversion processes is recognized. Effective process ability testing requires measurements to be made at temperatures and strains representative of the production process. The recently introduced Production Process Analyser (PPA) combines the benefits of the Production MDR with the enhanced process ability of the Rubber Process Analyser to bring more powerful, cost-effective compound analysis to the factory floor. Test instruments must satisfy new requirements to function efficiently in a production environment, most notably robustness and ease-of-use. The range of production-based instruments produced by Alpha Technologies incorporates all features required for reliable and simple operation. Improved efficiency, lower costs and higher quality are the benefits.

Sealing problems - Solutions in product design and choice of material

Seals are often seen as a necessarily bad thing in constructions. Therefore, many times, the design of the seal is delayed until the rest of the construction is developed. As a result the boundary conditions for the seal are such that a proper and easy design is no longer possible. In cases where insufficient sealing is discovered during testing of the prototypes it is difficult to get a solution within the time limits set for the product development. Also there are several cases known were the malfunctioning of the seal was discovered even after the product was taken in practical use. What also means after making the molds and taking the product in production. At that time only costly solutions are possible because they are likely to lead to adjustments of the total product design. Insufficient knowledge of the product designer of rubber properties, especially the long term behavior, and not enough asking about the real application of the producer or supplier of the rubber seals, is mostly the basis of these problems. This means that such problems are, in almost every case, possible to avoid. In case of discovering the problems during prototype testing it might be possible by redesigning the seal and its material to avoid adjustments to the other product characteristics. This means that sometimes it is possible to stay within the time limits for first delivery. Although in this stage small adjustments to the product might well be possible in order to improve the solution. In case the malfunctioning is discovered after the product is actually taken in use, problems become more complicated. Especially were sophisticated machines are involved, the solution should fit in the same space were the original, wrong, seal was located. Otherwise all machines marketed already have to be replaced. Failure at this stage is mostly the result of underestimating the long term behavior of rubber, like stress relaxation properties.

Stretched experimentation & prototyping using the semi-production vulcanization lines at DSM Elastomers

DSM Elastomers has the capability in Geleen to do continuous vulcanization on semi-production scale using e.g. UHF, Hot Air, High Speed Hot Air and/or a Salt bath. In a 30 min. slide show the capabilities will be presented.

The influence of the mixing parameters on the efficiency of the silanisation reaction in an internal mixer

The replacement of carbon black by silica in tread compounds results in a better performance of the tire in terms of wet-grip, abrasion resistance and rolling resistance, the latter resulting in a reduced fuel consumption of the car. The most important characteristic of a silica-filled cured rubber is the network formed between filler and polymer with the aid of a coupling agent, commonly bis(triethoxysilylpropyl)tetrasulfide (TESPT). The first step in the internal mixer, the reaction of the silanol groups of the filler with the ethoxy-groups of the coupling agent, is an equilibrium reaction. The efficiency hereof is improved by removing ethanol generated during the silanisation reaction. This can be achieved by efficient ventilation of the mixing chamber in order to avoid condensation of ethanol and input of mechanical energy in order to facilitate evaporation of the alcohol out of the rubber material. An efficient cooling of the compound allows to work close to the upper temperature limit of the TESPT and to avoid scorch. The analysis of the uncured compounds was done with a Rubber Process Analyzer (RPA) as it allows direct measuring of the Payne-effect, a property related to the rolling resistance of the tire tread. During a strain sweep measurement the breakdown of the remaining filler-filler network is monitored giving an indication of the degree of silanisation. [Acknowledgement] This investigation was done in the framework of the EEC project SATPRO. Further participants in this project are: Prof. Dr. A. Limper, K.-U. Kelting, University of Paderborn, Institute of Plastics Engineering, Fb10KTP, 33095 Paderborn, Germany Dr. H. Keuter, T. Boettcher, Krupp Elastomertechnik GmbH, Gummimischtechnik, P.O.Box 1180, 57258 Freudenberg, Germany G. Nijman, C. v. d. Pol, Vredestein Banden B.V., P.O. Box 27, 7500 AA Enschede, The Netherlands W. Matzke, Austrian Automobile-, Motorcycle- and Touring Club (

The Keltan

Recently DSM Elastomers has decided to optimise its Keltan