Dynamically vulcanized natural rubber

DVNR dynamically vulcanized natural rubber EDD engineering design database... 

Bahruddin, A. Ahmad, A. Prayitno, R. Satoto, Morphology and mechanical properties of Palm based fly ash reinforced dynamically vulcanized natural rubber/polypro-pylene blends, Procedia Chemistry, ISSN 1876-6196 4 (2012) 146-153. http //dx.doi. org/10.1016/j. proche.2012.06.021. 

Luo W, Hu X, Wang C, Li Q (2010) Frequency- and stiain-amplitude-dependent dynamical mechanical properties and hysteresis loss of CB-filled vulcanized natural rubber. Int J Mech Sci 52 168-174... 

The specimen was prepared by the following method. After mixing HAF carbon black (50 phr) with natural rubber (NR) in a laboratory mixer, carbon gel was extracted from unvulcanized mixture as an insoluble material for toluene for 48 h at room temperamre and dried in a vacuum oven for 24 h at 70°C. We made the specimen as a thin sheet of the carbon gel (including carbon black) by pressing the extracted carbon gel at 90°C. The cured specimen was given by adding sulfur (1.5 phr) to the unvulcanized mixture and vulcanized for 30 min at 145°C. The dynamic viscoelastic measurement was performed with Rheometer under the condition of 0.1% strain and 15 Hz over temperatures. 

The compound was made of scrap rubber from truck tires, essentially natural rubber, and sulfur. This compound is poor and vulcanization necessitates rather high pressure so as to compact the mixture. Nevertheless the final materials exhibit rather good mechanical properties measured either under static or dynamic conditions, as well as interesting qualities for absorption of impact noises [11]. 

S. Utara, P. Boochathum, Novel dynamic vulcanization of polyethylene and ozonolysed natural rubber blends Effect of curing system and blending ratio. J. Appl. Polym. Sci. 120, 2606-2614 (2011)... 

M. Kahar A. Wahab, H. Ismail, N. Othman. Effects of dynamic vulcanization on the physical, mechartical, and morphological properties of high-density polyethylene/(natural rubber)/(thcamoplastic tapioca starch) dlends. Journal of Vinyl Additive Technology 2012 18 192-197... 

TEM (refer to Figure 1) is used whenever a more in-depth study (when domain sizes are less than 1 micron or so) is required on polymer phase morphologies such as dynamically vulcanized alloys and Nylon/EP filler location as in carbon black in rubber compounds and also in the morphology of block copolymers. Thin sections are required and take anywhere from one hour to one day per sample depending on the nature of the sample. They must be 100 nm in thickness and are prepared usually by microtoming with a diamond knife at near liquid nitrogen temperatures (-150° C). The same contrasting media for SEM apply to TEM. In addition, PIB backbone polymers scission and evaporate in the TEM which helps... 

Now dynamically vulcanized rubber-plastic blends are poised to enter the realm of automobile tires. A TPV comprising a PA thermoplastic phase with isobutylene-co-p-methylstyrene (BIMSM) rubber can be used as an innerliner, outperforming either historical butyl rubber or the more classical halobutyl and its blend with natural rubber. These and future developments are targeting down-gauging of the barrier film thickness to simultaneously reduce both tire weight and reduced air permeation. A five-to-tenfold reduction in the latter is claimed to be feasible along with improved tire performance (Tsou 2007). 

Uneven distribution of carbon black can be observed, particularly in the first two instances, with a potential loss in material mechanical properties. Eurthermore, during processing and when the compound is in the uncured state, carbon black can migrate from the polymer with a low affinity for carbon black to one with a high affinity. This can be partially prevented by use of the concept of dynamic vulcanization where initial pre-vulcanization can lock carbon black into a particular phase. It would now be appropriate to describe the impact two specific polymer blends have on compounded material properties. Addition of polybutadiene to natural rubber can result in ... 

Thermoplastic Elastomers from High-Density Polyethylene Natural Rubber j Thermoplastic Tapioca Starch Effects of Different Dynamic Vulcanization... 

The poly(methyl methacrylate) molecules were dispersed in the natural rubber matrix, or vice versa, to form spherical droplets, as observed by optical photographs or scanning electron microscopy. The compatible natural rubber/poly(methyl methacrylate) blends had been made by the addition of the graft copolymer of natural rubber-gr t-poly(methyl methacrylate) as the compatibilizing agent due to its ability to enhance the interfacial adhesion between the two homopolymers. Moreover, Nakasorn and coworkers reported that natural rubber-gr i -poly(methyl methacrylate) could be blended with poly(methyl methacrylate) via a dynamic vulcanization technique with a conventional sulfur vulcanization system. The natural rubber-gra/t-poly(methyl methacrylate) was synthesized by a semi-batch emulsion polymerization technique via different bipolar redox initiation systems, i.e. cumene hydroperoxide and tetraethylene pentamine. ... 

FIG. 18-14. Dynamic bulk storage and loss compliances of natural rubber vulcanized by sulfur, reduced to 0°C and 1 atm pressure by equation 6 and plotted against logarithm of reduced frequency, var.p (McKinney, Belcher, and Marvin. )... 

Some of the key properties of PAREL elastomer vulcanizates are summarized in Table I. They have excellent low teiqierature properties excellent dynamic properties, which are much like those of natural rubber good ozone resistance and good heataging resistance. This interesting combination of properties is leading to substantial specialty markets in such applications as automotive engine mounts. Vulcanization and stabilization studies on PAREL elastomer, as well as additional specific properties of PAREL elastomer, are reported in this book by Boss. 

Parel elastomer, a copolymer of propylene oxide and allyl glycidyl ether, has a combination of properties that make it very useful in many rubber applications. It can be vulcanized with a conventional mixture of sulfur and accelerators. The cured elastomer has a low glass transition temperature (approximately -55 to -60 C.), and the excellent dynamic properties of natural rubber. It can be made very stable to high temperature oxidative degradation, and is better than neoprene in this respect, when NBC is added as a stabilizer. 

The length of the sulfide crosslinks formed during vulcanization will affect rubber properties. Mono- and disulfide crosslinks are more stable (less prone to scission) than polysulfide links and so promote better thermal and aging characteristics. Polysulfide links, on the other hand, provide somewhat better molecular flexibility. This can result in better dynamic fatigue resistance. Physical properties aside, the more stable crosslinks are often preferred to provide reversion resistance. Reversion is the cleavage of sulfide crosslinks during vulcanization which results from extending the cure beyond the time required to obtain the desired optimized balance of vulcanizate properties. When overcured in this way, certain elastomers, particularly natural rubber, will revert to the soft, more plastic, less elastic condition characteristic of the uncured compound. 

DV was applied to different systems, e.g., a diene rubber (EPDM, butyl rubber or natural rubber) is associated with a polyolefin (polyethylene or polypropylene) or an acrylonitrile-butadiene rubber (NBR) sample is associated with a polyamide. The high incompatibility between the elastomer and the plastic may be an important obstacle in the preparation of a dynamically vulcanized material, since the properties of the latter depend on the quality of the dispersion. The dispersity of NBR in polyolefins is very low and a polymeric compatibilizer must be added, which often requires grafting and coupling processes. 

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