Rubber nanoparticles

The observed improvement in the technological properties of the NR mix containing 2 phr of nano-ZnO is attributed to its larger surface area of the nanoparticles which enable better dispersion and rubber-nanoparticle interaction. 

The larger surface area of nano-ZnO particles enables better dispersion of the particles in the rubber matrix and improves the rubber-nanoparticle interaction. This results in the improvement of technological properties of NR compounds containing nano-ZnO. 

H. Zhou, H. Wang, H. Niu, A. Gestos, X. Wang and T. Lin. Fluoroalkyl silane modified silicone rubber/nanoparticle composite A super durable, robust superhydrophobic fabric coating. Adv. Mater, 24,2409-2412 (2012). 

Rothon and Hancock (1995) observed that it is widely assumed that fillers are cheap and that polymers are expensive. Conversely, for nanoparticles it is widely assumed that nanoparticles are expensive and that polymers are cheap. This is not necessarily the case. As the nanoparticle manufacturing industry expands, nanoparticles are increasingly available in large (i.e., tonne) quantities. The prices of expensive nanoparticles such as carbon nanotubes are also being reduced. The price of nanoparticles varies greatly with the type, as well as with the purity of the material. For example, silica nanoparticles supplied dispersed as a masterbatch in epoxy cost about 20/kg (Nanoresins 2008), and core-shell rubber nanoparticles similarly dispersed cost approximately 12/kg (Kaneka 2008). Nanoclays can cost as little as 7/kg (SigmaAldrich 2008). However, a kilogram of carbon nanotubes cost between 400 and 98,000 in Autumn 2009 (CheapTubes 2009). 

ZnO nanoparticles possess greater surface/volume ratio. When used in carboxylated nitrile rubber as curative, ZnO nanoparticles show excellent mechanical and dynamic mechanical properties [41]. The ultimate tensile strength increases from 6.8 MPa in ordinary rabber grade ZnO-carboxylated nitrile rubber system to 14.9 MPa in nanosized ZnO-carboxylated nitrile mbber without sacrificing the elongation at failure values. Table 4.1 compares these mechanical properties of ordinary and nano-ZnO-carboxylated nitrile rubbers, where the latter system is superior due to more rubber-ZnO interaction at the nanolevel. 

Bis(alkyldithio-/selenocarbamates) of Zn(ID and Cd(II) have previously been used in many applications including the rubber industry 1 and in analysis,382 as well as for single-molecular precursors in the growth of II VI thin films by CVD, as described earlier.181,383 They have also been shown to be good precursors for the preparation of II VI nanoparticles, in a process that involves their decomposition in a high-boiling donor solvent such as tri-n-octylphosphine oxide or 4-ethylpyridine (Figure 47). 

In order to produce high-performance elastomeric materials, the incorporations of different types of nanoparticles such as layered silicates, layered double hydroxides, carbon nanotubes, and nanosilica into the elastomer matrix are now growing areas of rubber research. However, the reflection of the nano effect on the properties and performance can be realized only through a uniform and homogeneous good dispersion of filler particles in the rubber matrix. 

The last few years have seen the extensive use of nanoparticles because of the small size of the filler and the corresponding increase in the surface area, allowing to achieve the required mechanical properties at low filler loadings. Nanometer-scale particles including spherical particles such as silica or titanium dioxide generated in-situ by the sol-gel process (4-8), layered silicates (9-12), carbon (13) or clay fibers(14,15), single-wall or multiwall carbon nanotubes (16,17) have been shown to significantly enhance the physical and mechanical properties of rubber matrices. 

The use of antimicrobial additives has been mentioned in section 12.7.2, but another route has also been investigated, the deposition of silver nanoparticles, under formaldehyde-radio frequency plasma conditions, onto food-grade silicone rubber. The bacteriocidal properties of the silver-coated surfaces were investigated by exposing them to Listeria monocytogenes, with no bacteria being detected after exposure times of 12 to 18 hours. 

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