Hybrid tensile strength

Nylon-6. Nylon-6—clay nanometer composites using montmorillonite clay intercalated with 12-aminolauric acid have been produced (37,38). When mixed with S-caprolactam and polymerized at 100°C for 30 min, a nylon clay—hybrid (NCH) was produced. Transmission electron microscopy (tern) and x-ray diffraction of the NCH confirm both the intercalation and molecular level of mixing between the two phases. The benefits of such materials over ordinary nylon-6 or nonmolecularly mixed, clay-reinforced nylon-6 include increased heat distortion temperature, elastic modulus, tensile strength, and dynamic elastic modulus throughout the —150 to 250°C temperature range. 

The data provided by Toyota Research Group of Japan on polyamide-MMT nanocomposites indicate tensile strength improvements of approximately 40%-50% at 23°C and modulus improvement of about 70% at the same temperature. Heat distortion temperature has been shown to increase from 65°C for the unmodified polyamide to 152°C for the nanoclay-modified material, all the above having been achieved with just a 5% loading of MMT clay. Similar mechanical property improvements were presented for polymethyl methacrylate-clay hybrids [27]. 

Figure 3.17 shows the mechanical properties of the ACM-silica and ENR-silica hybrid composites synthesized from various pH, reproduced from the data reported by Bandyopadhyay et al. [36]. As morphology indicates, all the samples prepared within the pH range 1.0-2.0 are transparent, contain nanosilica particles, and are superior in tensile strength and modulus... 

Silanol-terminated PDMS and hexadecyltrimethylammonium-exchanged clay were used to prepare PDMS-clay nanocomposites via melt intercalation [90]. The melt intercalation nanocomposites did not achieve as high a reinforcement as the aerosilica silicone hybrid, but the nanocomposite formed from solution had a nearly identical reinforcing effect on tensile strength as the aerosilica composite. 

Note UTS=ullimate tensile strength, X=in-plane 0°, Y=in-plane 90°, Z = through thickness, Vpfibcr volume fraction, M=mat VGCF, H=hybrid VGCF, S=short staple VGCF, P=P-55 fiber, E=cpoxy, CER=cyanate ester resin. 

Functionalized, liquid polybutadiene derivatives have also been developed as hybrid flexiblizers for epoxy resins. Carboxyl-terminated butadiene/acrylonitrile polymers, butadiene homopolymers, and maleic anhydride-amino acid grafted butadiene homopolymers have been used as flexibilizers to impart good low-temperature strength and water resistance to DGEBA-based epoxy adhesives. An epoxy system toughened by polybutadiene with maleic anhydride is claimed to provide a hydrophobic backbone, low viscosity, softness, and high tensile strength and adhesion (Table 7.10). 

Table 14.6 illustrates typical improvements noted in epoxy hybrid formulations with vinyl chloride, acrylic, and styrene butadiene lattices. Tensile strengths of cured, latex-saturated paper substrates are listed in absolute numbers while those of latex-epoxy hybrids are listed as percent increases in tensile strength over that of the latex alone. The mechanisms believed responsible for these improvements are (1) cocuring of the epoxy group with carboxyl and amine functional groups present on the latex backbone and/or (2) homopolymerization of the epoxy catalyzed by the tertiary amine included in some hybrid formulations. 

In one example, the tensile strength of polyamide 6 was increased by 55% and the moduli by 90%, with the addition of only 4wt% of delaminated clay. The enhanced tensile property of PCN suggests that nanocomposite performance is related to the degree of clay delamination, which increases the interaction between the clay layers and the polymers. Several explanations, based on the interfacial properties and the mobility of the polymer chains, have been given for this reinforcement. Kojima et al. reported that the tensile modulus improvement for polyamide 6-clay hybrid originated from a constrained region, where the polymer chains have reduced mobility. The dispersion and delamination of the clay were the key factors for the reinforcement. The delaminated nanocomposite structure produces a substantial increase in modulus. 

Lan and Pinnavaia [6] showed that hybrid organic-inorganic composites exhibited mechanical properties superior to those for their separate composites. Dependence of tensile strength and modulus of epoxy nano-clay composites on the chain length of the clay-intercalated alkylammonium ions is shown in Fig. 28. The presence of the organoclay substantially increased both the tensile strength and modulus relative to the pristine polymer. The mechanical properties increased with any exfoliation in the order ... 

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