EVA/organoclay nanocomposite

Li, X. and Ha, C. S. 2003. Nanostructure of EVA/organoclay nanocomposites Effects of kinds of organoclays and grafting of maleic anhydride onto EVA. Journal of Applied Polymer Science 87 1901-1909. 

Mishra, S. B. and Luyt, A. S. 2008. Effect of organic peroxides on the morphological, thermal and tensile properties of EVA-organoclay nanocomposites. eXPRESS Polymer Letters 2 256-264. 

Ardhyananta and co-workers [101] demonstrated the Young s Modulus of EVA/ organoclay nanocomposites increased as the clay loading was increased up to a value of 92%. 

In sections 9.3 and 9.4, microstructures of both the PBT/organoclay and the EVA/organoclay nanocomposites with different kinds of organoclays were discussed. It was found that the Cloisite 30B can form nanocomposites in both the PBT and the EVA-g-MAH matrix. Thus, the Cloisite 30B is selected to prepare PBT/EVA-g-MAH/organoclay ternary nanocomposites." ... 

The nanodispersed nanoadditives usually show enhanced fire performance and CCA has been the most powerful tool in analyzing the flammability of the PNs. In most cases, the PNs, as seen in Figure 11.20, show a significantly reduced peak HRR in the CCA curve. More examples of this are seen in PA-6/clay nanocomposite, which shows a 63% reduction in the peak HRR at 5% loading (Figure 11.2898 in which the heat release rate as a function of time for pure PA-6 and its clay nanocomposites is shown) and in poly(ethylene-co-vinyl acetate) (EVA)/clay nanocomposite,99 which shows a reduction of the peak HRR at about 50% at 5% organoclay loading. 

The solution-blending method was also employed by Srivastava et al. to prepare EPDM/ EVA/organoclay ternary nanocomposites [67,68]. EVA, with 45 wt% vinyl acetate (VA), and EPDM were blended in a 50/50wt/wt ratio with 2-8 wt% H3(Ci6)i organoclay in hot toluene... 

Figure 17.3 TEM micrograph for EVA/NR nanocomposites with 2 phr organoclay loading.

Figure 17.5 XRD patterns of pristine organoclay and EVA/NR nanocomposites with 8 phr organoclay loading.

The effect of different blending sequences and organoclay loading on stress at 100% elongation (MlOO) of the EVA/NR nanocomposites. 

The yield of crosslinking can be estimated from the gel fraction. The gel fraction values for EVA/natural rubber/organoclay nanocomposites are shown in Figure 17.17. An increment in organoclay loading does not show any clear influence in the gel content value of DCP vulcanizates. In the case of sulfur... 

Figure 17.17 Effect of organoclay loading on the gel content value of sulfur and peroxide EVA/NR/organoclay nanocomposite vulcanizates.

Figure 17.18 The effect of different crosslinking systems and organoclay loading on the tensUe strength of EVA/NR/organoclay nanocomposites.

In the case of EVA/natural rubber/organoclay nanocomposites, at irradiation doses of 50, 100 and 150 kGy the gel fraction yield has been significantly reduced with the increment of organoclay loading, as shown in Figure 17.20. 

Compound mixing was performed on different compounding equipment. For EVA organoclay-based nanocomposites, a laboratory twin-roll mill and an internal mixer heated to 145 °C were used. A corotating twin screw extruder from Leistritz, Germany, with a 27-mm screw diameter and an aspect ration of 40 L/D was used to generate polyethylene nanocomposites. The mass temperature was 190 °C at the extruder die. 

Table 7.1 Temperature at the maximum degradation rate of the main decomposition peak (DTG) measured by TGA under airflow at 20 °C/minfor EVA and EVA-based nanocomposites with different organoclay content...

The great improvements in flame retardancy caused by the organoclays also opened the possibility of decreasing the level of ATH within the EVA polymer matrix. The content of ATH needed to maintain 200 kW/m as a peak heat release rate could be decreased from 65 to 45 wt% by the presence of only 5 wt% organoclays within the EVA polymer matrix. Reduction in the total amount of these fillers resulted in improved mechanical and rheological properties of the EVA-based nanocomposite. 

TABLE 7.1 Maximum Temperature at the Main Degradation Peak Measured by TGA Under Airflow at 20°C/min for EVA and EVA-Based Nanocomposites with Different Organoclay Contents"... 

All compounds were melt-blended in a Brabender mixing chamber. It is evident from the results in Table 7.4 that all the filled polymers had improved flame retardant properties. For EVA and EVA-based nanocomposites containing 2.5 phr of filler, the PHRR decreased as follows EVA > organoclays purified MWCNTs. For EVA and EVA-based composites containing 5.0 phr of filler, the PHRR decreased as follows EVA > organoclays > purified MWCNTs = crude MWCNTs. Crude MWCNTs were as effective in the rednction of PHRR as purified MWCNTs Increasing the filler content from 2.5 phr to 5.0 phr caused an additional flame retardant effect that was most significant when purified or crude MWCNTs were used. 

More recently, some authors [59] and [65] have studied the effect of ternary blend morphologies on mechanical properties. Martins [65] prepared ternary nanocomposites of PP (-t-PP-g-acrylic acid)/ EVA/organoclay (60/40/5) by different blending procedures. He showed different localization of the... 

Mahmoudi et al. [74] studied the electrical and mechanical characterization of high-density poly-ethylene/ethylene vinyl acetate/organoclay nanocomposite. They found out that the electrical and mechanical properties of HDPE/EVA binary blend were enhanced significantly when OC was treated with EVA compound. The insulation material which is developed in this work can be employed to insulate the adjacent core steel sheets of a high-voltage transformer. 

---