Natural rubber EPDM blend

Plastics, such as PE, PP, polystyrene (PS), polyester, and nylon, etc., and elastomers such as natural rubber, EPDM, butyl rubber, NR, and styrene butadiene rubber (SBR), etc., are usually used as blend components in making thermoplastic elastomers. Such blends have certain advantages over the other type of TPEs. The desired properties are achieved by suitable elasto-mers/plastic selection and their proportion in the blend. 

Figure 13 Location of carbon black in a blend of chlorobutyl and natural rubber EPDM.

The miscibility of natural rubber (NR) blends is one of the most important factors when designing NR products. For instance, when the NR is miscible with a dissimilar polymer on a molecular level, we may improve the properties of NR as a function of the composition of the polymer. This is significantly different from the design for immiscible NR blends, whose properties are greatly dependent upon the morphology of the blend but less so on the composition. In most cases, NR is immiscible with non-polar synthetic rubbers, i.e. NR/butadiene rubber (BR) with high c -1,4-butadiene units, NR/styrene-butadiene rubber (SBR), NR/butyl rubber (IIR), NR/silicone rubber (q)13,i4 NR/ethylene-propylene-diene rubber (EPDM). This means it is important to find miscible NR blends and to control the morphology of the immiscible NR blends in a rational way. In this chapter, properties of NR blends are described from the viewpoint of miscibility, i.e. the miscible blend of NR/BR and the immiscible blend of NR/SBR. 

Ellul [27] subjected EPDM/polypropylene and natural rubber/polypropylene blends to various halogenation treatments, namely fluorine/carbon dioxide, sodium hypochlorite/ acetic acid and bromine water. With the natural rubber blend, there was a substantial uptake of fluorine, chlorine and bromine in the surface regions as indicated by energy dispersive X-ray analysis and with all three pre-treatments the adhesion to an acrylic tape was greatly enhanced. In contrast, with the EPDM blend, fluorine was the only reagent which reacted with the rubbers and only this treatment resulted in a significant increase in adhesion to the acrylic tape. The above results can be explained in terms of the different concentrations of carbon-carbon double bonds in the two blends. Substantial incorporation of chlorine and bromine could occur with the natural rubber-polypropylene blend but not with the EPDM blend. However, fluorine gas will react readily with saturated hydrocarbons [28,29] and therefore the incorporation of fluorine into the EPDM blend is not surprising. 

Natural rubber was blended with synthetic nonpolar rubbers like styrene butadiene rubber (SBR), butadiene rubber (BR) and EPDM and polar rubbers like NBR and CR [12]. NR/SBR and NR/BR blends were compatible, while NR/EPDM, NR/NBR and NR/CR blends were incompatible. 

TPEs from blends of rubber and plastics constitute an important category of TPEs. These can be prepared either by the melt mixing of plastics and rubbers in an internal mixer or by solvent casting from a suitable solvent. The commonly used plastics and rubbers include polypropylene (PP), polyethylene (PE), polystyrene (PS), nylon, ethylene propylene diene monomer rubber (EPDM), natural rubber (NR), butyl rubber, nitrile rubber, etc. TPEs from blends of rubbers and plastics have certain typical advantages over the other TPEs. In this case, the required properties can easily be achieved by the proper selection of rubbers and plastics and by the proper change in their ratios. The overall performance of the resultant TPEs can be improved by changing the phase structure and crystallinity of plastics and also by the proper incorporation of suitable fillers, crosslinkers, and interfacial agents. 

In all the compositions, the DCP-cured blends showed better properties than the corresponding unvulcanized samples. Choudhary et al. [30] further demonstrated the use of EPDM, chlorinated PE, chlorosulfo-nated PE, maleic anhydride modified polyethylene, and blends of epoxidized natural rubber-sulfonated EPDM as compatibilizers in NR-LDPE (low-density PE) blends. 

S—EB—S (compounds) polyurethane/elastomer block copolymers polyester/elastomer block copolymers polyamide/elastomer block copolymers polyetherimide/polysiloxane block copolymers polypropylene/EPDM or EPR blends polypropylene/EPDM dynamic vulcanizates polypropylene/butyl rubber dynamic vulcanizates polypropylene/natural rubber dynamic vulcanizates polypropylene/nitrile rubber dynamic vulcanizates PVC/ nitrile rubber blends... 

As a result of its saturated polymer backbone, EPDM is more resistant to oxygen, ozone, UV and heat than the low-cost commodity polydiene rubbers, such as natural rubber (NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). Therefore, the main use of EPD(M) is in outdoor applications, such as automotive sealing systems, window seals and roof sheeting, and in under-the-hood applications, such as coolant hoses. The main drawback of EPDM is its poor resistance to swelling in apolar fluids such as oil, making it inferior to high-performance elastomers, such as fluoro, acrylate and silicone elastomers in that respect. Over the last decade thermoplastic vulcanisates, produced via dynamic vulcanisation of blends of polypropylene (PP) and EPDM, have been commercialised, combining thermoplastic processability with rubber elasticity [8, 9]. 

Investigations of polymer blends has developed an increased understanding of interphase organization. In blends two interfaces exists the interface between two matrix types and distribution of filler and its interfaces with this matrices. The interphase of carbon black in blends of natural rubber and EPDM depends on the character of carbon black (surface groups available for interaction), the viscosity,... 

These may be used for low hardness compounds in areas where impact abrasion is predominant. EPDM is at times referred as crackless rubber5 since it has high tear resistance. For producing high hardness compounds blends with natural rubber, styrene-butadiene rubber (SBR) and high styrene resins are recommended. 

Polyblends with Soft Matrix. Polyblends in which both phases are soft are mixtures of different rubbers. Treads of automobile tires are made of polyblends of SBR with either natural rubber or cts-polybutadiene. Co vulcanization of EPDM with various rubbers is discussed in the chapter of M. E. Woods and T. R. Mass. Relaxation behavior of blends of EVA rubber with styrene/ethylene-butylene/styrene block copolymer and of poly (ethylene oxide) with ethylene oxide/propylene oxide/ethylene oxide block copolymer were studied by M. Shen, U. Mehra, L. Toy, and K. Biliyar. 

However, the difference in olefin concentration of EPDM and natural rubber results in a cure-rate misbatch leading to an incompatible blend. This has been recognized to cause both inferior static and dynamic mechanical properties such as poor tensile strength, fatigue resistance, and high hysteresis in the rubber blend (17). 

The basic materials used for the preparation of blends are EPDM and natural rubber. The structure and general characteristics of EPDM and NR are given in Pig. 15.1(31) and Table 15.1. 

Figure 15.3 Scanning electron micrographs of tensile fractured surfaces of the vulcanizates cured at 160°C (a) 75 25 unsaturated natural rubber-ethylene-propylene-diene (NR-EPDM) blend (one-stage) at 500 x (b) 75 25 NR-EPDM blend (two-stage) at 500 x (c) 50 50 NR-EPDM blend (one-stage) at 750 x (d) 50 50 NR-EPDM blend (two-stage) at 750 x. (From Reference 32 with permission from John Wiley Sons.)...

Chapter 15 Ethylene-Propylene-Diene Rubher/Natural Rubber Blends 465 Table 15.7 Ozone Resistance of NR/EPDM Blends. 

Olefinic thermoplastic elastomers are block copolymers or blends of polyolefins — commonly, polypropylene, which forms the hard crystalline block, and another olefin block, most commonly ethylene or EPDM. Some less common soft segments include natural rubber, nitrile rubber, and EVA. Olefinic thermoplastic elastomers exhibit better processability than neoprene and have excellent resistance to oils. Therefore, they offer attractive replacements for neoprene in oil-resistant wire and cable insulation. 

Knappe [10] described the use of DMA to check the plasticizer level of polybutadiene/natural rubber blends. DMA can also be used to look at coatings on elastomer parts, an example being a polyurethane coating on an EPDM (ethylene propylene diene monomer) bumper part, where the low temperature storage modulus can be a key to component toughness. 

There is a relatively large range of different types of rubbers that are used in different components in the food industry that can get in contact with the food. The most important of these are natural rubber (NR ds-l,4-polyisoprene), nitrile rubber (i.e., acrylonitrile-butadiene copolymer), ethylene-propylene rubber (EPR), rubbers of ethylene-propylene monomer (EPM) and EPDM, SBR, fluorocarbon rubber, silicone rubber, polybutadiene rubber (BR), polychloroprene rubber, and TPE. In addition, there is the use of rubber blends, i.e., blends of NR and N Rr with SBR [19]. 

The addition of rubber to the iPP gives rise to differences in the nucleation density of the spherulites. The number of spherulites per unit area (N/S) depends on the chemical nature and molecular mass of the elastomer, on T and composition. For iPP/EPDM blends, N/S... 

Ethylene propylene diene terpolymers (EPDM) can be used to improve the ozone resistance of bromobutyl/natural rubber binary polymer blends, eliminating the need for chemical antiozonants. Addition of 10 phr of EPDM (with a high ethylidene norbornene, ENB, content of9%) to a 50/50 bromobutyl rubber/natural rubber blend results in a compound vdth good static and dynamic ozone resistance. EPDM with a 5.7% ENB level is another suggested grade of polymer. 

Volnme resistivities have been reported on phenol-formaldehyde [37], carbon fibre reinforced ABS terpolymer [35], natural rubber [38], polystyrene (PS) [35], HDPE-natnral fibre composites [34], carbon black filled PP-epoxy-glass fibre composites [5], XLPE [32], nanoclay reinforced EPDM-g-TMEVS [31] and epoxy resin/PANI blends [33]. 

The objects of study were selected mixture of low-density polyethylene (LDPE) with wood flour (WF), natural rubber (NR) and ethylene-propylene rubber (EPDM). WF content is 40 wt.%. Rubber injected at 10 and 20 masses %. As composite materials based on LDPE blending performed on a laboratory mixer at a temperature of 140°C for 5 minutes and then get the film samples in a laboratory press. The sample thickness was 100 10 microns. 

Development of TPEs with various types of elastomers and polyolefins has been extensively reported by many researchers. Ethylene-propylene-diene monomer (EPDM) or its modified form is used as the elastomer in most polyolefin TPEs. Natural rubber (NR) and thermoplastic blends have become an area of interest only recently. These materials are known as thermoplastic natural rubber (TPNR). The development of TPNR was principally based on the criteria set by EPDM blends with thermoplastics. Two types are known, one belonging to the TPO class and the other belonging to the TPV class. 

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