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Organotin-free Catalysts for Silane Curing Polyolefin Elastomer/Linear low Density Polyethylene Blends via reactive Extrusion
A compound of crosslinking polyolefin elastomer (POE)/ linear low-density polyethylene (LLDPE) blend, as a class of thermoplastic elastomer family, was prepared through a two-step silane grafting method (Sioplas process) using twin-screw extruder. The silane grafted compound was used as wire and cable coatings. New regulations require replacement of versatile catalysts with organotin-free candidates as a sulphonic acid-based catalyst with a long alkyl chain attached. This study was investigated the effect of different amounts of dodecyl-benzene sulphonic acid (DDBSA) as catalyst on properties of the compound.Weiterlesen...
Does nonlinear Viscoelasticity inherently exist in Rubber?
This study investigates the transition from linear to non-linear viscoelastic behavior in polymers and rubber compounds under cyclic sinusoidal shear deformation. The stress response is analyzed through Fourier series decomposition, enabling the definition of the generalized elastic modulus, G0' (γ0) and viscous modulus. These parameters are critical for characterizing the complex viscoelastic properties. It is shown that G0' (γ0) comprises two distinct contributions: the first harmonic, corresponding to the linear elastic response, and the non-linear modulus GN′L (γ0 ) which arises from all higher harmonic components. The study further examines the effect of carbon black fillers on nonlinear viscoelasticity, revealing significant nonlinearity induced by the fillers.Weiterlesen...
Investigation of the Post- Hardening Effect in a Silica filled NR-Compound
Storage hardening is an effect that commonly occurs in unvulcanized natural rubber (NR) compounds. In this study, the increase in hardness during storage of a vulcanized NR compound filled with silica was investigated. An increase in hardness during storage at room temperature and at 60 °C was observed. It was expected that this post-hardening effect was caused by the increasing formation of mono- and disulfidic bonds created out of broken polysulfidic bonds. However, Temperature Scanning Stress Relaxation (TSSR) and the thiol-amine method showed an unexpected increase in polysulfidic bonds for the stored compounds. This formation of additional polysulfidic bonds is likely enhanced by the residual MBT formed during the vulcanization process accelerated with CBS.Weiterlesen...
Wie ein Polymerkristall Strom leitet
Von einem internationalen Forscherteam wurde ein zweidimensionales leitendes Polymer entwickelt, das eine außergewöhnliche elektrische Leitfähigkeit und metallisches Ladungstransportverhalten besitzt. Erfahren Sie weitere Details.Weiterlesen...
Zum Einfluss der thermischen Eigenschaften von FKM-Mischungen auf die Ausprägung des nichtisothermen Gough-Joule-Effektes
Die Ausprägung des nichtisothermen GJ-Effektes wird entscheidend von dem erzielten Ausmaß der Entropieverringerung bei der Deformation eines elastomeren Profils bestimmt. Aber auch die thermischen Eigenschaften des Elastomerwerkstoffes beeinflussen mit, inwieweit eine aufrechterhaltene Entropieverringerung bei Wärmezuführung durch einen Spannungszuwachs sichtbar wird. Neben der Temperaturabhängigkeit ist auch der Einfluss einer zu-nehmenden Materialdeformation auf bestimmte thermische Eigenschaften von Bedeutung, in welchem Anteil zugeführte Wärmeenergie in mechanische Arbeit umgewandelt werden kann. Am Beispiel eines FKM-Werkstoffes werden alle analytischen Untersuchungen durchgeführt.Weiterlesen...
Mechanical Investigation of Fiber-Reinforced Epoxy Composite Implants for Femur Fractures
Femur fractures, often resulting from trauma or osteoporosis, pose significant challenges due to their impact on mobility and quality of life. Metallic implants like titanium and stainless steel, despite their strength and biocompatibility, present issues related to stress shielding, altered biomechanics, and limitations in diagnostic imaging. This study explores the use of epoxy composites reinforced with Kevlar fibers (KF), carbon fibers (CF), hybrid fibers, and flax fibers as potential alternatives to metallic implants. The biomechanical performance of these composites under tensile and flexural stresses was evaluated. Kevlar fiber composites demonstrated superior mechanical properties.Weiterlesen...
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...