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Recycled Crumb Rubber in Rigid Pavements: Assessing Structural and Environmental Impact
Rubber disposal challenges include pollution from landfilling and incineration, leaching harmful chemicals, and releasing toxic emissions. This study investigates using crumb rubber in concrete to mitigate environmental impact. Crumb rubber was tested as a fine aggregate replacement at 5 - 25 % weights and treated with 10- 30 % sodium hydro- xide. Mechanical, physical, and durabi-lity tests showed that crumb rubber concrete, especially with 20 % NaOH treatment, enhances performance compared to traditional concrete. This approach supports sustainable waste management and improves concrete properties.Weiterlesen...
Zur thermischen Leitfähigkeit (Teil 2): Weichmacherzusätze in AEM-Mischungen und deren Einfluss auf die Kinetik der chemischen Vernetzungsreaktion
Im Gegensatz zum untersuchten Einfluss verschiedener Metalloxid-Pigmente auf die thermischen Eigenschaften einer peroxidisch vernetzenden FKM-Mischung (1. Teil, KGK 05/24) wird hier der Einfluss eines zunehmenden Weichmachergehaltes auf die Kinetik der chemischen Vernetzungsreaktion, auf die Temperaturleitfähigkeit, die spezifische Wärmekapazität, die Wärmeleitfähigkeit und die Wärmeeindringzahl betrachtet. Dafür kommen, neben der Laser-Flash-Analyse (LFA), auch die Dynamisch-Mechanische-Analyse (DMA) und die DDK-(DSC)-Analyse zum Einsatz. In diesem Fall werden die Zusammenhänge am Beispiel der diaminischen Vernetzungsreaktion von EACM-(Vamac)-Mischungen und einem synthetischen Weichmachertyp aufgezeigt. Die Bestimmung von Aktivierungsenergien rundet die Thematik ab.Weiterlesen...
A critical Review of the applicability of the Cox-Merz Relationship on filled Rubber Compounds
The Cox-Merz rule is one of the most important empirical rheological transfer functions with considerable practical importance in the plastics industry. In this paper, the applicability of the empirical rheological transfer function of the Cox-Merz rule to filled rubber compounds of practical relevance is investigated. Data from dynamic frequency measurements obtained using the RPA are compared with data from conventional high-pressure capillary rheometry. It is found that the Cox-Merz relationship is not fully valid for filled rubber systems. Possible reasons for the non-applicability are given.Weiterlesen...
Sustainable Recycling of EPDM Rubber: Investigation of the Aging Behaviour of recycled EPDM Waste1
This aging study examined EPDM rubber waste, devulcanized by dibenzamido diphenyl disulfide (DBD) and activated with a low molecular weight EPDM polymer (LP). The amounts of curing system, DBD, and LP were varied below 200 °C in a mixer and a twin-screw extruder. The aging behavior was evaluated by mechanical properties as well as FT-IR and NMR analyses of the soluble fractions. Depending on the parameters, surface blooming occurred after aging, attributed to DBD. Specifically, 4 wt% DBD at 160 °C significantly affected the properties before and after aging, as excess DBD increased age-related crosslinking. After adjusting the formulation and process parameters, however, the recyclate aged similarly to new material and was deemed suitable for producing seals according to DIN EN 681-1:2006.Weiterlesen...
Zur thermischen Leitfähigkeit durch Füllstoffzusätze und ihr Einfluss auf die Kinetik von FKM
Die Laser-Flash-Analyse (LFA) eröffnet temperaturabhängige Messungen zur Temperaturleitzahl. Das Verfahren ist von hohem Interesse, wenn durch den Einfluss verschiedener Rezepturbstandteile und deren Konzentrationen in der Elastomermischung die thermischen Eigenschaften verbessert und somit die Kinetik der chemischen Vernetzungsreaktion signifikant erhöht wird. Am Beispiel der Peroxidvernetzung soll aufzeigt werden, inwieweit eine direkte Korrelation zur Reaktionskinetik überhaupt besteht. Aufgrund einer zu erwartenden, thermischen Leitfähigkeitsverbesserung wird der Fokus vorrangig auf verschiedene Metalloxide in FKM-Mischungen gelegt und deren Konzentrationen gezielt variiert.Weiterlesen...
Role and Mechanisms of Coagents in peroxide Crosslinking
High performance elastomers based on peroxide cured EPDM have a wide range of applications. The aim of the investigations carried out using different EPDM-types was optimizing the elastomer properties by means of suitable combinations of peroxides and coagents and their concentration ratios, which requires a fundamental understanding of the mechanisms in the interaction of the crosslinking agents. The achievable crosslinking densities (XLD) and crosslinking efficiencies were investigated Aging studies using chemiluminescence (CL) shows, that residual peroxide (RPC) content causes a significantly lower thermal-oxidative aging resistance.Weiterlesen...
Dynamic Mechanical Analysis by Rebound Resilience – Revisiting Rebound Resilience
The rebound resilience according to Schob is a widely used test method. It delivers information about hysteretic losses in a rubber sample. Its success is not only related to the simplicity of the experiment, but also to the characteristic contact times and the type of deformation similar to those observed in tire-road contact. While the resilience value only delivers a relative value of the dissipation of the potential energy of a pendulum, the highly dynamic process of the impact contains valuable informa- tion accessible by analysis of the time derivatives of the deformation as a function of time. A new type of rebound tester according to Schob is proposed here that is able to perform a dynamic mechanical analysis of the rebound resilience within the contact time of a few milliseconds.Weiterlesen...
Study on the Impact of Tire usage on Environment
During drive Tire abrades, NSD reduces to a point when the Tire is no more safe to drive. Tire abrades – where do the worn Tire material go? Obviously to the atmosphere, rubbers and chemicals particles flow in the air which we inhale. Tread of a tire which is made of rubbers/fillers (CB, Silica), processing aids/oils/chemicals (ZnO, stearic acid, Accelerators – sulphenamides/thiurams/DPG/MBT derivatives etc., Antioxidants & Antiozonants – mostly ppd & quinoline derivatives – Resorcinol products/Cobalt naphthenate and others), waxes. These (except silica and ZnO) are all petroproducts. Tire wear particles contain a number of organic chemicals, some of which are toxic.Weiterlesen...
Comparative Advantages of different RPA-ASTM Methods for Detecting Rubber Compound Quality Differences
Over the last three decades, the Rubber Process Analyzer has evolved as the processability test instrument of choice for measuring and solving many rubber factory problems. Also, a new ASTM reflective microscope method is also commonly used. Now there is a total of nine different RPA ASTM International methods that are routinely used by the rubber industry to measure quality of raw rubber, state-of-mix differences for rubber compounds, predictions of downstream processability differences, etc. Of course, there are comparative advantages and disadvantages for each of these RPA ASTM methods, depending on the quality differences of the raw rubber and vast quality differences among factory recipes, even among compounds that are used for the same purpose. This paper uses a design of experiment to quantify some of the comparative advantages statistically for the RPA ASTM test methods.Weiterlesen...
Fraunhofer-Projekt sucht PFAS-freie Substitutionsmaterialien für Elektrolyseure
Das Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF hat das Projekt Elastolox initiiert. Darin soll die Eignung von PFAS-freien Elastomeren für den Einsatz in Elektrolyseuren und Brennstoffzellen unter oxidativ-alkalischen Bedingungen untersucht werden.Weiterlesen...