Melt-mixed composites

Figure 7.2 Melt-mixed composites based on different polymer matrices and types of MWCNTs. Light microscopy images of thin sections, including the composition, values of the agglomerate area ratio and the thickness of the thin sections. ...

Relation Between SME, CNT Dispersion, CNT Length, and Electrical Properties of Melt Mixed Composites... 

In previous studies, macrodispersion was improved with increasing SME during the processing of melt mixed composites based on polyamide 6 and At the same time, the relation between electrical resistivity and SME showed a minimum which was found in both of the examples mentioned at approximately 1400-1800 J cm (0.4-0.5 kW h kg ). Further increases in SME resulted in increasing electrical resistivity values, even if the macrodispersion improves with SME or levels off at low values of Ap, Thus, a certain... 

To investigate the relation between SME, CNT dispersion, CNT length, and electrical properties of melt mixed composites in a more detailed way, three studies on composites based on PCL and different PCs were performed. 

In another study by Sdrobis et al. [57], the effect of modification on cellulose pulp fibers in LDPE was reported. They used unbleached and bleached kraft cellulose pulp fibers modified with oleic acid in cold plasma conditions as reinforcements. The melt-mixed composites contain up to 10 wt% of untreated and modified cellulose pulp fibers with LDPE. They reported that interfacial adhesion between cellulose and matrix could be improved through modification and most of the properties have been improved when the modified pulp fibers were incorporated into composite matrix. Variation of complex viscosity function of angular frequency for composites is shown in Fig. 11.11. 

Potschke, P., Abdel-Goad, M., Pegel, S Jehnichen, D., Mark, J.E., Zhou, D., and Heinrich, G. (2009) Comparisons among electrical and rheological properties of melt-mixed composites containing various carbon nanostructures. J. Macromol. Sci. A, 47, 12-19. 

Processing methods have different effects on the mechanical properties of sisal fiber-reinforced polypropylene (SF/PP) composites. Under optimum mixing conditions, melt-mixed composites showed better tensile properties than those of solution-mixed composites. The effect of different chemical treatments on the properties of sisal/PP composites was investigated and it was found that the tensile properties of the composites were enhanced considerably [145]. 

Rubber blends with cure rate mismatch is a burning issue for elastomer sandwich products. For example, in a conveyor belt composite structure there is always a combination of two to three special purpose rubbers and, depending on the rubber composition, the curatives are different. Hence, those composite rubber formulations need special processing and formulation to avoid a gross dissimilarity in their cure rate. Recent research in this area indicated that the modification of one or more rubbers with the same cure sites would be a possible solution. Thus, chlorosulfonated polyethylene (CSP) rubber was modified in laboratory scale with 10 wt% of 93% active meta-phenylene bismaleimide (BMI) and 0.5 wt% of dimethyl-di-(/ r/-butyl-peroxy) hexane (catalyst). Mixing was carried out in an oil heated Banbury-type mixer at 150-160°C. The addition of a catalyst was very critical. After 2 min high-shear dispersive melt mix-... 

In another case where the twin-screw extruder was used, the rubber and plastic were melt mixed with all ingredients in a similar manner as described in blend compositions for static vulcanizations. The product was then dumped, cooled, and granulated. The premixed granules were then fed into a twin-screw extruder where a very narrow temperature profile was maintained with a relative high compression (2 1), and the screw speed was adjusted depending on the final torque and the flow behavior of the extruded stock. The stock was cured by shear force and temperature enforced by the twin-screw extruder. The dynamically crosslinked blend was taken out in the form of a strip or solid rod to determine the... 

The TLCP used was a widely investigated one, Vectra A950, manufactured by Hoechst-Celanese. The PC was produced by Enichem under the tradename Sinvet 303. Table 3 lists the main properties of these materials according to the manufacturers. The materials were dried in a vacuum oven at 120°C for 4 h before processing. Prior to injection molding of the composite samples, two components were melt mixed by a ZSK, W P, Stuttgart, extruder with a constant weight ratio of PC-TLCP = 80 20 [23]. 

The melt mixed 80/20 PS/iPP blend displays a set of exotherms, where the amount of the iPP component that was heterogeneously nucleated is substantially reduced as indicated by the decrease of the crystallization enthalpy in the temperature region where the iPP crystallizes in bulk, i.e., at 109-111 °C (exotherm labeled A). This effect is due to the confinement of iPP into a large number of droplets. If the number of droplets of iPP as a dispersed phase is greater than the number of heterogeneities present in the system, fractionated crystallization occurs. The number of droplets for this composition is known (by scanning electron microscopy observations) to be of the order of 1011 particles cm-3 and polarized optical microscopy (POM) experiments have shown that this iPP contains approximately 9 x 106 heterogeneities cm-3. In fact, it can be seen in Fig. 1 that the fractionated crystallization of the iPP compon-... 

Composition D-2, This composition consists of a mixture of desensitizing wax 84, lecithin 2 Nitrocellulose 14%. It is prepared by melting mixing the ingredients in the above amounts When the mixture is uniform and free from any visible impurities, it is cast in the form of slabs not more than 2 inches thick, or in the form of pellets not more than 2 "x 2 " in size. Composition D-2 is used to emulsify desensitize solid explosives or mixtures of explosives. The detailed US Military requirements of Composition D-2 are given in Ref 2, where the tests are also described... 

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