Latex nanocomposites

Recently a lot of attention is being given to the field of latex-based nanocomposites. Various organoclays as well as pristine clays have been intercalated in aqueous medium with NR latex, SBR latex, NBR latex, as well as carboxylated nitrile mbber (XNBR) latex [184—187], to achieve a good degree of dispersion. 

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The aspect ratio calculated using the Cussler model is much higher than that calculated using the Neilsen model. This model will agree with a very low clay loading and a better homogeneous dispersion in polymer matrix as a model fit. However, it is not suitable for the latex nanocomposite system. ... 

A. Mohamed, A.K. Anas, S.A. Bakar, T. Ardyani, W.M.W. Zin, S. Ibrahim, M. Sagi-saka, P. Brown, J. Eastoe, Enhanced dispersion of multiwall carbon nanotubes in natural rubber latex nanocomposites by surfactants bearing phenyl groups. Journal of Colloid and Interface Science, ISSN 0021-9797 455 (October 1, 2015) 179-187. http //dx.doi. org/10.1016/j.jcis.2015.05.054. 

A.B. Suriani, M.D. Nmhaflzah, A. Mohamed, I. Zainol, A.K. Masrom, A facile one-step method for graphene oxide/natural rubber latex nanocomposite production for supercapacitor applications. Materials Letters, ISSN 0167-577X 161 (December 15, 2015)... 

Latex is a colloidal dispersion of polymer in an aqueous solvent. This method is more suitable for those polymers that can be prepared via emulsion polymerization or those that have the ability to form emulsion. It consists of an aqueous dispersion/ stabilization of filler using a surfactant followed by the addition of the dispersed filler into the polymer latex. Nanocomposites can be obtained after freeze-drying the above mixture followed by melt processing. The latex method has several advantages including no requirement for organic solvent, reliability, ease of processing, and improved dispersion of the filler in the viscous polymer matrix [70]. 

On the contrary, it has been found that the rheological properties of silica-latex nanocomposites are a result of matrix properties and of their modification in the presence of silica filler. The filler structure of the nanocomposites is governed by the... 

Banc Amelie, Genix Anne-Caroline, Chirat Mathieue, et al. Tnning strnctnre and rheology of silica-latex nanocomposites with the molecular weight of matrix chains A coupled SAXS-TEM-Simulation Approach. Macromolecules. Al no. 9 (2014) 3219-3230. 

Mballa Mballa MA, Ali SI, Heuts JPA, van Herk AM (2012) Control of the anisoUopic morphology of latex nanocomposites containing single montmorillonite clay particles prepared by conventional and reversible addition-fragmentation chain transfer based emulsion polymerization. Polym hit 61 861-865... 

Nanocomposites have been prepared with this polymer and mechanical and barrier properties and ffacmre behavior have been studied [74—76]. The latex of this mbber has also been used for the same [77]. Sadhu and Bhowmick [78-81] have studied the preparation, stmcmre, and various... 

Core-shell nanocomposite of Mg(OH)2/PMMA with an average particle size of ca. 500nm where Mg(OH)2 is the core and PMMA is the shell was successfidly prepared by the emulsion polymerization of MMA in the presence of surface modified Mj OH)2. The grapelike ( re-shell microspheres with PMMA nodules could he obtained as stable latex. 

Silicone co-polymer networks and IPNs have recently been reviewed.321 The development of IPNs is briefly described, and the definitions of the main (non-exclusive) classes of the IPNs are cited. Examples of latex IPNs, simultaneous and sequential IPNs, semi-IPNs, and thermoplastic IPNs are provided. The use of silicone-silicone IPNs in studies of model silicone networks is also illustrated. Networks in which siloxane and non-siloxane components are connected via chemical bonds are considered co-polymer networks, although some other names have been applied to such networks. Today, some of the examples in this category should, perhaps, be discussed as organic-inorganic hybrids, or nanocomposites. Silicone IPNs are discussed in almost all of the major references dealing with IPNs.322-324 Silicone IPNs are also briefly discussed in some other, previously cited, reviews.291,306... 

Figure 7 shows the representative bright field HRTEM images of nanocomposites of NR and unmodified montmorillonite (NR/NA) prepared by different processing and curing techniques. It is apparent that the methodology followed to prepare the nanocomposites by latex blending facilitates the formation of exfoliated clay structure, even with unmodified nanoclays. It has been reported in the literature that hydration of montmorillonite clay leads to extensive delamination and breakdown of silicate layers [94, 95]. It has also been shown that NA disperses fully into the individual layers in its dilute aqueous dispersion (clay concentration <10%)... 

This is truly reflected in the morphology of the uncured clay preexfoliated rubber nanocomposite films (NLu NA) prepared by the latex blending method (Fig. 7a). Curing the NR/NA nanocomposites in situ prevulcanization (No>NA) does not alter the arrangements of dispersed clay layers greatly, as seen from the... 

Fig. 7 Bright fiefd HRTEM images showing the deveiopment of morphoiogy in 4 phr NA-filled NR nanocomposites under different processing and curing conditions a latex-biended uncured NC (NLUNA) b prevuicanized NC (NLPNA) and c conventionaliy cured NC (NMNA). d X-ray diffractograms of NA and its nanocomposites...

Morphology evolution is thus found to be dependent on the processing technique applied to disperse the nanoparticles. The latex-blended and prevulcanized nanocomposites show predominant exfoliation with some intercalation, especially in uncured and prevulcanized samples. In conventionally cured but latex-blended nanocomposites, realignment of NA particles is visible, with a greater tendency of NA platelets towards agglomeration. In solid state mixing, the dispersion is still poorer. XRD studies also corroborate the above observations. 

Fig. 39 Plots showing the effect of surface area factor on the extent of property improvement. Symbols represent experimental values, and the lines are their apparent fitting. Encircled data points are taken from unpublished research work on NR latex-based NA nanocomposites. Vertical dotted line indicates the critical point...

At the steps before the elaboration of carbon nanotube nanocom-posites, wet-STEM can be used for the characterization of nanotubes dispersed in a liquid (see Figure 3.18), and for polymer latex/ nanotubes mixing (before evaporation or freeze-drying to elaborate polymer/carbon nanotube nanocomposites). 

Several main synthesis methods widely applied to produce carbon nanotube-polyurethane nanocomposites were summarized above. In addition, latex technology (27), thermally induced phase separation (28), electrospinning (29,30) and many other methods also show their own advantages and promises, however, these methods will not be discussed here. 

Fig. 2 Different paths to obtain hybrid materials from molecular sources. Path A Sol-gel routes (Al conventional route for hybrid nanocomposites, A2 molecularly homogenous hybrids). Path B Assembly of nanobuilding blocks (ANBB), of prefunctionalized or postfunctionalized clusters or nanoparticles. Route C or D involve the use of templates capable of self-assembly, giving rise to organized phases. Path E involves integrative synthesis combining precedent paths from A to D and other processes, such as the use of lithography, casting, organogels or latex beads as templates, controlled phase separations, or external fields. (From Ref. l) (View this art in color at www.dekker.com.)...

Luna-Xavier, J.L., Guyot, A., and Bourgeat-Lami, E., Synthesis and characterization of silica/polyjmethyl methacrylate) nanocomposite latex particles through emulsion polymerization using a cationic azo initiator, J. Colloid Inteif. Sci., 250. 82, 2002. 

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