Improving the abrasion resistance of “green” tyre compounds

Since the introduction of “Green Tyres” in the early 90’s, the use of silica as a reinforcing filler, along with a silane coupling agent, has spread and grown worldwide. The greatest advantage of using silica over carbon black as a reinforcing filler in a tyre tread compound is that a lower rolling resistance is achieved, while maintaining good wet traction. However, a previous study has shown that the wear resistance of a silica filled epoxidised natural rubber (ENR) compound was not as high as those of conventional Oil Extended Styrene Butadiene rubber (OESBR) and NR/BR compounds used in passenger car and truck tyre treads. In this work, with the aim of improving abrasion resistance, the effect of blending Butadiene rubber (BR) into a silica filled ENR compound was studied. Blends with 0 to 30 phr BR were prepared in a Polylab Haake internal mixer. The rheological properties of the compounds were measured using a Mooney viscometer and Oscilating Disc Rheometer. The hardness, tensile strength and DIN abrasion resistance were also measured. The results showed that the ENR/silica compound properties such as tensile strength and hardness were as good as those of the conventional compounds. However, the most important finding was that abrasion resistance increased significantly with BR content, exceeding that of the conventional compound at BR:ENR ratios of greater than 20:80

Printability of elastomer latex for additive manufacturing or 3D printing

Additive manufacturing, sometimes referred to as 3D printing is a new, rapidly developing technology which has the potential to revolutionize fabrication of certain high value, complex products. Until now conventional elastomers have not been widely used in the additive manufacturing process. The goal of our work was to determine the feasibility of additive manufacturing using ink jet printing of elastomeric latex materials. Particle size, viscosity, and surface tension were measured for five different latex materials—poly(2-chloro-1,3-butadiene), carboxylated styrene-butadiene rubber, carboxylated butadiene-acrylonitrile copolymer, natural rubber, and prevulcanized natural rubber. The XSBR latex was predicted as the one most likely to be printable. Printing trials carried out with the XSBR as the ink proved it to be printable, although technical problems of agglomeration and print head clogging need to be addressed and both the material and process need to be optimized for consistent printing to be achieved

Oxo-degradable plastics: degradation, environmental impact and recycling

This paper summarises the results of a study to assess the environmental impact of oxo-degradable plastics. These plastics are mainly based on polyethylene and contain additives that cause the plastic to undergo oxidative degradation by a process accelerated by light and/or heat. The approach used in the study has been to review the published research on oxo-degradable plastics, assess other literature available in the public domain, and also to engage with stakeholders throughout the life cycle of the product. The main purpose of the study was to assess what happens at the end of life of the plastics and whether this has a beneficial effect. The study concluded that incorporating additives into petroleum-based plastics to accelerate their degradation does not improve their environmental impact and potentially gives rise to certain negative effects. In particular there is concern that these plastics are neither suitable for conventional recycling methods, due to the presence of degradation accelerators, nor suitable for composting, due to the lack of biodegradability. There is also concern about the fate of oxo-degradable plastic fragments in the environment

Fibres from blends of epoxidized natural rubber and polylactic acid by the electrospinning process: compatibilization and surface texture

Fibres were electrospun from blends of an epoxidized natural rubber (ENR) with a minor amount of a crystalline grade of polylactic acid (PLA), using a graft copolymer compatibilizer (ENR-g-JM) produced by reaction processing of a mixture of PLA and monoamine terminated polypropylene glycol (Jeffamine M600). The incorporation of PLA into the elastomer spinning solution in the form of a blend was necessary to obtain the required solution properties and to establish the appropriate operational conditions for the successful electrospinning of fibres. The addition of a small quantity of compatibilizer to the ENR/PLA blend reduced the severity of surface roughness of the fibres. Moreover, the use of monoamine terminated polypropylene glycol alone, as a plasticizer, was also found to exert a control on the development of surface texture during electrospinning. The rate of solvent induced crystallization in the swollen fibres jet was identified as the factor determining the surface topography

Cure efficiency of dodecyl succinic anhydride as a cross-linking agent for elastomer blends based on epoxidized natural rubber

Blends of a highly epoxidized natural rubber (ENR50) with unmodified natural rubber (NR) and ethylene propylene elastomers (EPDM) were produced to evaluate the mixing and curing characteristics. Dodecyl succinic anhydride was used to cross-link the ENR50 component and the reactivity was assessed by monitoring the evolution of the torque in an oscillatory co-axial cylinder rheometer, as well as by DSC thermal analysis. A physical model was used to obtain a single parameter for the reactivity of the system, which corresponds to the rate constant for first order curing reactions. Although the blends were thermodynamically immiscible, displaying no significant change in Tg, the components were well dispersed at microscopic level. Better mechanical properties were obtained for blends with EPD

Improving the Abrasion Resistance of “Green” Tyre Compounds

Since the introduction of “Green Tyres” in the early 90’s, the use of silica as a reinforcing filler, along with a silane coupling agent, has spread and grown worldwide. The greatest advantage of using silica over carbon black as a reinforcing filler in a tyre tread compound is that a lower rolling resistance is achieved, while maintaining good wet traction. However, a previous study has shown that the wear resistance of a silica filled epoxidised natural rubber (ENR) compound was not as high as those of conventional Oil Extended Styrene Butadiene rubber (OESBR) and NR/BR compounds used in passenger car and truck tyre treads. In this work, with the aim of improving abrasion resistance, the effect of blending Butadiene rubber (BR) into a silica filled ENR compound was studied. Blends with 0 to 30 phr BR were prepared in a Polylab Haake internal mixer. The rheological properties of the compounds were measured using a Mooney viscometer and Oscilating Disc Rheometer. The hardness, tensile strength and DIN abrasion resistance were also measured. The results showed that the ENR/silica compound properties such as tensile strength and hardness were as good as those of the conventional compounds. However, the most important finding was that abrasion resistance increased significantly with BR content, exceeding that of the conventional compound at BR:ENR ratios of greater than 20:80

Effect of SiO₂ particles on the relaxation dynamics of epoxidized natural rubber (ENR) in the melt state by time-resolved mechanical spectroscopy

The rheological behavior of an epoxidized natural rubber (ENR) nanocomposite containing 10 wt.% of silica particles was examined by time-resolved mechanical spectroscopy (TRMS), exploiting the unique capability of this technique for monitoring the time-dependent characteristics of unstable polymer melts. The resulting storage modulus curve has revealed a progressive evolution of the elastic component of the composite, associated with slower relaxations of the ENR macromolecular chains. Two major events were identified and quantified: one is associated with the absorption of the epoxidized rubber macromolecules onto the silica surface, which imposes further restrictions on the motions of the chains within the polymer phase; the second is related to gelation and the subsequent changes in rheological behavior resulting from the simultaneous occurrence cross-linking and chain scission reactions within the ENR matrix. These were quantified using two parameters related to changes in the storage and loss modulus components