Nanoclays surface treatment

However, the simple melt mixing of polyolefins with natural clays, does not guarantee a sufficient level of dispersion of the nanoparticles, which are often present in the form of micron-size agglomerates. In order to overcome this problem, two main strategies have been followed surface functionalization of needle-like clays (usually by alkyl-silanes) or addition of a third polymeric phase (usually maleic anhydrite modified PP PP-g-MA), which acts as a compatibilizer between the matrix and nanofiller. Both methods tend to modify the surface energies of the nanocomposite system, in order to reduce the interparticle interaction and improve the dispersion. In the case of a reactive surface treatment only, the polymer-day interaction is expected to be enhanced, along with better nanoclay dispersion, which is very important for the final mechanical properties. 

Surface treatment of nanoclays, which typically involves cation exchange, promotes delamination of the clay sheets in the matrix. The cation, or alternatively the intercalated media between the clay layers, determines the interlayer space, the gallery, and the cation exchange capacity [11]. 

Cost is the key point to fabricate PUN products for engineering concerns. The addition of nanofillers in PUs can be achieved with slight modification to the current commercial process. High cost of nanofiller is still the barrier to develop PUN products. The nanofillers from natural sources such as nanoclay, nanographite, and natural nanotubes are cheaper than CNTs and POSS, which should have more chance to be used in PUNs. The effort should also be placed on developing the simple and effective methods for surface treatment with scaling-up potential. 

ATH and MH are used primarily in wire and cables in poly( vinyl chloride) (PVC), polyethylene, and various elastomers. There is also some limited application of MH in polyamide-6. To pass flame retardancy tests, 35 to 65 wt% of metal hydroxide is required. Decreasing the loading of metal hydroxides will result in a significant gain in physical properties, especially low-temperature flexibility therefore, combinations with red phosphorus, sUicones, boron compounds, nanoclays (treated montmorillonites), and charring agents have been explored. Surface treatment of metal hydroxides also helps to improve physical properties and sometimes improves flame retardancy, due to better dispersion. 

The thermal degradation behavior of nanoclay-modified epoxy has been studied, and is closely linked to the fire performance. Nanoclay has little effect on this behavior, and may even reduce the temperature at which degradation starts due to the relative instability of tbe surface treatment (Brnardic et al. 2008). The addition of carbon nanofibers to an amine-cured epoxy polymer had no effect on the decomposition temperature of epoxy (Zhou et al. 2007), but single-walled nanotubes have been shown to degrade the thermal stability (Puglia et al. 2003). 

Nanosheets, Nanofibers, NS-Ti02, Sol-gel process. Nanoclays, Doped-Ti02, Hydrothermal process. Photocatalysis, Electrocatalysis, Solar cell. Lithium batteries. Antibacterial surfaces. Self-cleaning surfaces, Photocatalytic cancer treatment, H2 production. Environmental remediation. Immobilized 7702. 

Fire retardancy behavior of PP/PA66 blends compatibilized with PP-g-MAH and modified with untreated and treated nanoclays was studied (Kouini and Serier 2012). It was found that the intercalation, exfoliation of nanoclays of nanocomposites, and the flame retardancy properties were improved significantly. In addition a good balance of impact strength and flame retardancy was obtained for PP/PA66 nanocomposites in the presence of PP-g-MA compatibilizer. The presence of the clay led to an increase in the flammability time. In addition, the treatment made a more pronounced effect. A 23 % increase was observed only when 4 wt% nanoclay was added and a longer flammabiUty time was noticed with treated clay. This was attributed to the stacking of nanoclay which created a physical protective barrier on the surface of the material. Similar behavior has been reported by earlier workers (Kocsis and Apostolov 2004). 

Organotitanates, aluminates, zirconates and zircoaluminates can also act like silanes as adhesion promoters. They perform similar functions, but unlike silanes there is no need for water molecules to be eliminated. These other treatments bond the polymer to the filler surface by a chemical bond involving proton co-ordination, and they can also be used with fillers that are not receptive to silanes, such as calcium carbonate, carbon black and barium sulfate, as well as barium ferrite, magnesium hydroxide, aluminium trihydroxide, titanium dioxide, talc and the nanoclays. 

Figure 1. The SEM images of (a) large undispersed nanoclay aggregates. The excerpt shows the surface structural features laminar fine structure can be seen on the aggregate surfaces, (b) spincoated nanoclay platelets after dispersing with the ultrasonic microtip, and (c) spincoated nanoclay platelets after high pressure fluidizer treatment.

Hossain et al. [45] studied the effects of surface modification of jute libers and nanoclay on jute-Biopol green composites. Four subsequent chemical treatments including detergent washing, dewaxing, alkali treatment, and acetic acid treatment were performed to facilitate better bonding between the fiber and matrix. The scanning electron microscopy and Fourier transform infrared spectroscopy study confirmed improved fiber surfaces for better adhesion with matrix after final treatment. Enhanced thermal... 

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