NBR blends

An ethylene propylene diene monomer/poly (ethylene-co-vinyl acetate) (EPDM/ EVAc) blend has also been proven to exhibit the above observations in systems with benzene, toluene and xylene as probe molecules [64]. The reduction in solvent uptake was prominent when the EVAc content was increased, and the compositions became less rubbery or more plastic-like due to the semicrystalline nature of EVAc. The liquid sorption characteristics of sulfur- and peroxide-cross-linked 40/60 EPDM/EVAc blends can be explained by the nature of the S—S and C—C chemical bonds. 

The barrier properties of 70/30 acrylonitrile-butadiene mbber/ethylene propylene diene monomer rubber (NBR/EPDM) vulcanizates, when loaded with carbon black fillers [e.g., I SAP (intermediate super-abrasion furnace), HAF (high-abrasion furnace) and SRF (semi-reinforcing furnace)] and using benzene, toluene and xylene as penetrants, have been examined with reference to the type of filler employed [66]. The filled samples were found to exhibit a better resistance to uptake of the three organic solvents when compared to the respective unfilled blends for any given blend ratio. With regards to the three types of carbon black used, solvent uptake was in the order SRF- HAF- ISAF-filled samples. The reason for this order was attributed to the better filler reinforcements and enhanced crosslink densities of the matrix as the size of the carbon black particles used was decreased. A similar behavior was also identified for NR/EVA composites [52]. 

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Table 10 Effect of Short-Time Aging on Mechano-Chemical Properties of PVC-NBR Blend...

Compatibility of immiscible PP-NBR blends was improved by the reactive compatibilization technique using various modified polypropylenes. In this study. 

However, a substantial improvement in impact energies of PP-NBR blends with GMA or IPO functionalized PPs is observed. The PP-NBR blends went through a brittle-ductile transition as the concentration of the functionalized PPs in the matrix phase reached a leveling off at 13 wt% in the case of IPO functionalized PP and 25 wt% in the case of GMA functionalized PP. Up to a ten-fold improvement in impact energy was observed when the brittle-ductile transition was reached. 

Figure 10 Effect of different functionalized PPS on the impact energy of PP-NBR blends, B-HPMA, -GMA, A-TBAEMA, D-HEMA, O-IPO, and A-DMAEMA. Source Ref. 73.

Figure 11 Force displacement curves of a-PP, b-nonreac-tive PP-NBR blend, c-reactive blend containing 13 wt% GMA functionalized PP, and d-reactive blend containing 25 wt% GMA functionalized PP. Source Ref. 73.

Coran and Patel [74] investigated the reactive com-patibilization of PP-NBR and HDPE-NBR blends using phenolic modified polyolefin, maleic anhydride modified polyolefin, and amine terminated nitrile rubber as reactive components. Dynamic vulcanization was also inves-... 

The reactive compatibilization of HDPE-NBR and PP-NBR blends has been studied by Thomas and coworkers [75,76]. The maleic anhydride modified polyolefins and phenolic modified polyolefins are used as com-patibilizers. The effect of the concentration of these compatibilizers on the compatibility of these blends was investigated in terms of morphology and mechanical properties. It was found that in these blends an optimum quantity of the compatibilizer was required to obtain maximum improvement in properties, and after that a leveling off was observed. The domain size of the dispersed NBR phase in these blends is decreased up to a certain level and then increases (Fig. 12 and 13). The reduction in domain size is attributed to the increase in... 

Figure 12 Scanning electron micrographs of 70 30 HDPE-NBR blend with (a) 0 wt%, (b) 1 wt%, (c) 5 wt%, and (d) 10 wt% maleic anhydride modified polyethylene. Source Ref. 75.

Scheme 5 Reaction scheme for the formation of graft copolymer in PP-NBR blends in the presence of phenolic modified PP.

Figure 15 Effect of phenolic modified PP concentration on tensile strength and tear strength of 70 30 PP-NBR blend. Source Ref. 76.

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

Furnace black-reinforced EPDM and NBR blends were compounded with different concentrations of azodicarbonamide foaming agent to produce EPDM and NBR foamed composites. All the mechanical parameters measured were found to decrease as the foaming agent concentration and/or temperature increased. The stress-strain results were discussed with reference to the continuum mechanics theory for compressible materials. 16 refs. 

The representative IR spectra for PVC and NBR blends [31] are shown in Figures 5.10 and 5.11 [31]. Neat PVC shows two sharp absorbance peaks at 1734 and 1590 cm"1 which are due to the carbonyl groups formed during the manufacturing stage [33] and the polymer backbone defect [34],... 

Figure 5.11 Infrared spectra of 50/50 PVC/NBR blends after mixing (a) for 5 minutes, (b) for 60 minutes (stabilised with tribasic lead sulfate) at 180 °C, (c) at 160 °C, (d) at...

PVC/NBR blends have been developed in the 1940 s as an alternative to natural rubber. In addition, the blend provided improved processability and high resistance to oxidation, a notorious drawback for the natural rubber wire coatings. 

More recent research investigates possibility of obtaining blends of PVC with conductive polymers. Figure 3.33 shows that concentration of conductive polymer is essential for conductivity. Optimal conductivity is obtained at a certain range of PVC concentration. The blends of poly(ethylene oxide), PEO, poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate), PEDOT-PSS, and PVC were designed to maximize thermal stability and conductivity. The thermal stability of the blend is increased by PEO and conductivity is increased by increasing concentration of PEDOT-ESS." Conductivity of PVC-NBR blends can be increased by addition of polyaniline-DL-camphor sulfonic acid, PANI-CSA. The conductivity of the blend increases linearly with the amount of PANI-CSA." ... 

Figure 3.28. EfTect of AN content in NBR on Charpy impact strength of PVC/NBR blends. Impact resistance reaches a maximum in the semicompatible region. Room temperature, 25°C PVC/NBR = 100/15. (Matsuo, 1968.)...

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