Blends and Composites

Polymer blends may exhibit SM behavior irrespective of the miscibility of the blend components. One of the blend components should show the required 

Because PLA is highly brittle, it has been blended with numerous polymers to improve its toughness. A by-product of this research was the observation that some blends, in fact, showed SM feature. Lai and Lan [61] studied the SM performance of PLA/thermoplastic PU blends at 70/30 and 50/50 compositions. Thermoplastic PU was found in dispersed form at 70/30 ratio, while a bicontinuous phase structure was concluded for the PLA/PU = 50/50. After deforming the specimens at = 25,80, and 120 °C, the recovery was assessed in the temperature range T = 20-160°C. Note that the selected data are below and above that of the of the PLA (about 80 °C). Rf, 7 , and the recovery stress strongly depended on and recovery temperatures. Rf increased with increasing while an opposite trend was observed for R.  

Zhang et al. [62] demonstrated SM behavior for PLA toughened by a polyamide-12-based elastomer that was incorporated up to 30 wt%. For of the tensile- 

PLA/PCL blends in the compositions range of 100/0 to 60/40 were produced with and without additional MWCNT by Amirian et al. [64]. The phase-segregated blends exhibited two and two values. The latter increased with 

A novel approach should be credited to Luo and coworkers [65] to improve the SM performance of PCL. They prepared inclusion complexes between a-cyclodextrin and PCL. Through this host-guest complexation, a pecuUar physical network was created with naked PCL segments as switching phase and cyclodextrin-PCL inclusion complex domains as net points. Both R and R were shghtly reduced with the inclusion ratio (30-50%). The in vitro degradation of this new type of blend was faster than the reference PCL. 

Various blends, composites and block copolymers containing the isobutene moiety have been synthesized. The interest in these compounds originates from possible applications in advanced technologies. Polymers of these types are summarized in Table 6.3. 

PS/PIB/PS block copolymers can be made by controlled-living cationic polymerization. In this polymerization process, the propagating chains are in equilibrium with the dormant species. A suit- 

PIB based thermoplastic poly(urethane)s (TPU)s have been synthesized. These composites exhibit enhanced mechanical properties. Poly(tetramethylene oxide) (PTMO) has been used as a compatibi-lizer. 

PIB based block copolymers are of interest for biomedical applications due to their superior biostability and biocompatibility (30). 

In biomedical applications, a typical TPU consists of PTMO as soft segment and diisocyanatodiphenyl methane as a hard segment. Further, 1,4-butanediol is used as a chain extender (37). 

Practically, some of the above polyolefin copolymers have already been used to blend with PP in applications such as car bumpers and impact elastomeric goods. Although ethylene-propylene random copolymer has been the main component for such 

The above polyolefin copolymers have also been used to prepare conventional composites and nanocomposites. However, similar to the case of polymer blends, not too many studies have been reported thus far. Recently, Kelarakis et al. (49) have mixed 10 wt% of surface-modified carbon nanofiber (MCNF) with propylene-ethylene random copolymer (propylene 84.3%). The MCNF acted as a nucleating agent for crystallization of the a-form of PP in the matrix. During deformation at room temperature, strain-induced crystallization took place, while the transformation from the 7-phase to a-phase also occurred for both unfilled and 10 wt% MCNF-filled samples. The tensile strength of the filled material was consistently higher than that of pure copolymer. These results are illustrated in Fig. 8.27. 

However, when compared with pure copolymer, the highly stretched nanocomposite exhibited a higher amount of unoriented crystals, a lower degree of crystal orientation, and a higher amount of 7-crystals. This behavior indicated that polymer crystals in the filled nanocomposite experienced a reduced load, suggesting an effective load transfer from the matrix to MCNF. At elevated temperatures, the presence of MCNF resulted in a thermally stable physically cross-linked network, which facilitated strain-induced crystallization and led to a remarkable improvement in the mechanical properties. For example, the toughness of the 10 wt% nanocomposite was found to increase by a factor of 150 times at 55°C. Although nanofillers 

For certain applications, the properties of PPS can be adapted or improved by the fabrication of compositions. Compositions based on PPS are summarized in Table 5.3. 

PolyCphenylene sulfide) exhibits a low impact strength and hence is brittle. Attempts to improve the impact strength go back to 1983, when ethyl-ene/glycidyl methacrylate copolymers were incorporated into PPS as impact modifiers. However, the adhesion of impact modifiers to PPS at the interface is not satisfactory, and an improvement was suggested in the treatment of the PPS by aqueous acid before use, to improve the adhesion properties.  

The modification of PPS with silicone rubber and aminosilane improves the mechanical properties. It is believed that the aminosilane functions as a type of compatibilizer between the silicone rubber and PAS. It has been found that PAS resins lacking an aminosilane additive and containing a functionalized silicone rubber have different impact and elongation characteristics compared to PAS resins containing a non-functional-ized silicone rubber and an aminosilane. It is believed that the aminosilane, non-functionalized silicone rubber, and PAS components undergo a reaction in the melt.  

Another method is to improve the impact strength by using terpoly-mers composed from ethylene, ethyl acrylate, and glycidyl methacrylate and terpolymers composed from ethylene, butyl acrylate, and maleic an- 

In electrical and electronic applications, such as circuit breakers, multipole rods, and breaker bulbs, a material must be available which combines heat resistance with good electrical properties. Namely, tracking cvurent resistance and arc resistance are necessary. PPS as such exhibits good heat resistance. The electrical properties can be improved by a formulation containing PA and magnesium hydroxide. In addition, the composite is reinforced by glass fibers (GF)s.  

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J. A. Manson and L. H. Sperling, Polymer Blends and Composites, Plenum Press, New York, 1976. 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Viscosities of the blends and composites were measured in shear flow with a Gottfert Rheograph 2002 capillary viscosimeter. The shear rate was investigated from 100-10000 s" . The L D ratio of the capillary die was 30 mm 1 mm. Rabinowitch correction was made to the measurements, but Bagley correction was not applied. 

Table 2 Tensile Properties of Extruded Blends and Composites...

The tensile properties of the extruded blends and composites are presented in Table 2. Compared to the neat PP, a clear reinforcement was achieved after twin-screw blending. The reinforcing effect was even more pronounced with the higher take-up speed (H), evidently due to the extremely fibrillar morphology, as seen in Fig. 3. 

The mechanical properties of the injection molded blends and composites are shown in Table 3. 

In both the blends and composites, the addition of LCP reinforced the PP matrix considerably. On the basis of the fibrillar morphology throughout the specimens, even better mechanical properties were expected for the composites than for the blends. The poorer than expected reinforcement was primarily due to the lack of adhesion between fiber and matrix. 

The rheological behavior of the blends and composites was totally different. Addition of LCP reduced the... 

Manson JA, Sperling LZ (1976) Polymer blends and composites Plenum Press, London, Ch 13... 

Dawsey TR (1994) In Gilbert RD (ed) Cellulosic Polymers, Blends and Composites. 

Manson, J.A. Sperling, L.H. "Polymer Blends and Composites" Plenum New York, 1976. 

S. Patachia, Blends based on poly(vinyl alcohol) and the products based on this polymer , in Handbook of Polymer blends and composites , C. Vasile and A.K. Kulshreshtha (eds.), Chap. 8, RAPRA Technology LTD., England, Chap.8. 2003. p. 288-365. 

All of the examples of PEMs discussed within Section 3.3 unhl now have been composed of only one polymer system without any other compounds present—be they small molecules, polymers, or solid-state materials. A wide variety of different polymer blend and composite PEMs has been made. However, in this section, only a brief overview highlighting some of the more interesting examples that have been reported in the literature will be presented. Eor discussion, these types of PEMs have been divided into three categories polymer blends, ionomer-filled porous substrates and reinforced PEMs, and composite PEMs for high-temperature operation and alternative proton conductors. 

Keywords Biodegradability Blends and composites Poly(propylene carbonate) Thermal properties Viscoelastic properties... 

Monasse B, Haudin JM (1995) In Karger-Kocis J (ed) Polypropylene structure, blends and composites, vol 1. Chapman HaU, London, p 5... 

Janeschitz-Kriegel H, Fleischman E, Geymayer W (1995) Processing-induced structure formation. In Karger-Kocsis J (ed) Polypropylene structure,blends and composites, vol 1. Chapman Hall, London, chap 10, p 295 Fujiyama M, Wakino T (1991) J Appl Polym Sci 43 97 Fujiyama M, Wakino T (1991) J Appl Polym Sci 42 9 Fyjiyama M, Wakino T (1991) J Appl Polym Sci 43 57 Kolarik J, Lednicky F, Jancar J.Pukanszky B (1990) Polym Commun 31 201 Kolarik J, Jancar J (1992) Polymer 33 4961... 

Pukanszky B (1995) In Karger-Kocsis J (ed) Polypropylene. Structure, Blends and Composites, vol 3. Chapman and Hall, London, p 1... 

Manson, J. A., Sperling, L. H. Polymer blends and composites. New York Plenum Press 1976... 

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