Rubber blends thermal properties

The reactive extrusion of polypropylene-natural rubber blends in the presence of a peroxide (1,3-bis(/-butyl per-oxy benzene) and a coagent (trimethylol propane triacrylate) was reported by Yoon et al. [64]. The effect of the concentration of the peroxide and the coagent was evaiuated in terms of thermal, morphological, melt, and mechanical properties. The low shear viscosity of the blends increased with the increase in peroxide content initially, and beyond 0.02 phr the viscosity decreased with peroxide content (Fig. 9). The melt viscosity increased with coagent concentration at a fixed peroxide content. The morphology of the samples indicated a decrease in domain size of the dispersed NR phase with a lower content of the peroxide, while at a higher content the domain size increases. The reduction in domain size... 

Jha A. and Bhowmick A.K., Thermoplastic elastomeric blends of nylon 6/acrylate rubber Influence of interaction of mechanical and dynamic mechanical thermal properties. Rubber Chem. TechnoL, 70, 798, 1997. 

The static and dynamic mechanical properties, creep recovery behaviour, thermal expansion and thermal conductivity of low-density foams made of blends of LDPE and EVA were studied as a function of the EVA content of the blends. These properties were compared with those of a foam made from a blend of EVA and ethylene-propylene rubber. A knowledge of the way in which the EVA content affects the behaviour of these blend foam materials is fundamental to obtaining a wide range of polyolefin foams, with similar density, suitable for different applications. 9 refs. 

Mixing process Technical rubbers are blends of up to about 30 different compounds like natural rubber, styrene-butadiene rubber, silicate and carbon-black fillers, and mobile components like oils and waxes. These components show a large variety of physical, chemical, and NMR properties. Improper mixing leads to inhomogeneties in the final product with corresponding variations in mechanical and thermal properties (cf. Figure 7.4). 

Polypropylene is also used in a number of blends, some of them with applications in rubber industry, automotive industry, home constructions, etc. Some of the copolymers and blends used in rubber industry are vulcanized. Studies on thermal properties and pyrolysis of these copolymers and blends are common in literature [97, 105,110-118]. 

Nakason, C., Panklieng, Y., and Kamesamman, A. 2004. Rheological and thermal properties of thermoplastic natural rubbers based on poly (methyl methacrylate)/epoxidized-natural-rubber blends. Journal of Applied Polymer Science 92(6) 3561-3572. 

Nakason, C., Tobprakhon, A., and Kaesaman, A. 2005. Thermoplastic vulcanizates based on poly(methyl methacrylate) /epoxidized natural rubber blends Mechanical, thermal, and morphological properties. Journal of Applied Polymer Science 98 3) 1251-1261. 

Mina, M. R, Alam, A. K. M. M., Chowdhury, M. N. K., Bhattacharia, S. K., and Balta Calleja, R J. 2005. Morphology, micromechanical, and thermal properties of undeformed and mechanically deformed poly (methyl methacrylate) /rubber blend. Polymer Plastics Technology and Engineering 44(4) 523-537. 

Abbate M, MartusceUi E, Ragosta G, Scarinzi G (1991) Tensile properties and impact behaviour of poly(D(-)3-hydroxybutyrate)/rubber blends. J Mater Sd 26 1119-1125 Abe H, Doi Y (2002) Side-chain effect of second monomer units on crystalline morphology, thermal properties, and enzymatic degradability for random copolyesters of (R)-3-hydroxybutyric add with (R)-3-hydroxyalkanoic acids. Biomacromolecules 3 133-138 Abe C, Taima Y, Nakamura Y, Doi Y (1990) New bacterial copolyester of 3-hydroxyalkanoates and 3-hydroxy-co-fluoroalkanoates produced by Pseudomonas oleovorans. Polym Commun 31 404 06... 

S. Goyanes, C.C. Lopez, G.H. Rubiolo, F. Quasso, A.J. Marzocca, Thermal properties in enred natural rabber/styrene butadiene rubber blends, European Polymer Journal, ISSN 0014-3057 44 (5) (May 2008) 1525-1534. htq> //dx.doi.org/10.1016ij.enrpolymj.2008.02.016. 

R. Giri, K. Naskar, G.B. Nando, Effect of electron beam irradiation on dynamic mechanical, thermal and morphological properties of LLDPE and PDMS rubber blends. Radiation Physics and Chemistiy, ISSN 0969-806X 81 (12) (December 2012) 1930-1942. http //dx.doi.0rg/lO.lOl6/jjadphyschem.2Oi2.O8.OO4. 

N.Z. Noriman, H. Ismail, The effects of electron beam irradiation on the thermal properties, fatigue life and natural weathering of st5trene butadiene rubber/recycled acryloni-hile-butadiene rubber blends. Materials Design, ISSN 0261-3069 32 (6) (June 2011) 3336-3346. http //dx.doi.Org/10.1016/j.matdes.2011.02.020. 

NR is primarily utilized in the tyre industry because of its ideal properties. However, it has poor stability due to the existence of many double or unsaturated bonds. To improve the ambient stability of NR, synthetic rubber was chosen for blending. Zhang and coworkers blended and vulcanized NR and chloroprene rubber at a weight ratio of 75/25 by using a two-roll mill. The NR/ chloroprene rubber blends had improved mechanical properties in terms of their elongation strength and Shore A hardness. Moreover, the vulcanized chloroprene rubber blends had excellent oil resistance, thermal stability, selfextinguishing ability and ozone resistance. 

The thermal properties of NR based polar synthetic rubber blends is expected to affect the application range of these vulcanizates. Degradation, glass transition and crystallization temperatures determine the service conditions of each blend. Additionally, the existence of single or multiple shifted or not glass transition temperatures of each blend supplies evidence for the miscibility of the components involved. " Nevertheless, in many cases further analysis might be required to determine miscibility. 

Furthermore, the C=C bonds in the natural rubber structure might induce poor thermal and oxidative resistance in the natural rubber blends. Thus, Thawornwisit and coworkersproposed the preparation of hydrogenated natural rubber, which is one of the chemical modifications available to improve the oxidation and thermal resistance of diene-based natural rubber before blending with poly(methyl methacrylate-co-styrene). The poly(methyl methacrylate-co-styrene) was resistant to the outdoor environment and had excellent optical properties with a high refractive index, but it was extremely brittle and had low impact strength. Hydrogenated natural rubber could, however, be used as an impact modifier, as well as to improve its thermal and oxidative resistance for these acrylic plastics. 

Furthermore, the rubber can improve other characteristics such as hydro-philicity and adhesion, leading to wider applications. Many techniques, i.e. morphological, mechanical, thermal, rheological and dielectric studies can be used to investigate the properties of natural rubber blends and IPNs with dilferent types of acrylate polymers. Due to the interesting properties of natural rubber blends and IPNs with acrylate polymers, they can reach applications in many industrial fields such as automotive, household appliances, medical devices, electrical cables, and headphone cables. 

Bhatt et al. created blends of medium chain length PHA (mcl-PH A) with NR as well as other types of rubber, and they found that in addition to altering the thermal properties, the blending can also affect the biodegradable properties of PHA and NR. The blend films were effectively degraded by Pseudomonas sp. 202, the degradation ratio of which can be tailored by adjusting the rubber/ PHA ratio. ... 

Natural rubber based-blends and IPNs have been developed to improve the physical and chemical properties of conventional natural rubber for applications in many industrial products. They can provide different materials that express various improved properties by blending with several types of polymer such as thermoplastics, thermosets, synthetic rubbers, and biopolymers, and may also adding some compatibilizers. However, the level of these blends also directly affects their mechanical and viscoelastic properties. The mechanical properties of these polymer blended materials can be determined by several mechanical instruments such as tensile machine and Shore durometer. In addition, the viscoelastic properties can mostly be determined by some thermal analyser such as dynamic mechanical thermal analysis and dynamic mechanical analysis to provide the glass transition temperature values of polymer blends. For most of these natural rubber blends and IPNs, increasing the level of polymer and compatibilizer blends resulted in an increase of the mechanical properties until reached an optimum level, and then their values decreased. On the other hand, the viscoelastic behaviours mainly depended on the intermolecular forces of each material blend that can be used to investigate the miscibility of them. Therefore, the natural rubber blends and IPNs with different components should be specifically investigated in their mechanical and viscoelastic properties to obtain the optimum blended materials for use in several applications. 

Natural rubber/cw-1,4-polybutadiene (NR/BR) blends (70/30 mass ratio) have been widely used in the tire industry. Many nanocomposites based on organo-montmorillonite (OMMT)/rubber blends have been investigated. However, relatively little attention had been paid to binary rubber hybrids/ montmorillonite nanocomposites, and according to Zheng Gu et ah, no studies existed dealing with OMMT/NR/BR nanocomposites. So, the authors described the preparation of OMMT/NR/BR nanocomposites by direct mechanical blending and determined the cure characteristics, static mechanical properties, dynamic mechanical properties, and thermal stability of the nanocomposites. OMMT/NR/BR nanocomposites had exactly the same onset decomposition temperature and lower thermal degradation rate as the NR/BR blends. 

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