Semicrystalline polymers thermoplastics

Figure 13.3 compiles the main variables and parameters that define a semicrystalline thermoplastic polymer matrix that, in combination with the processing steps, optimize thermophysical and mechanical behavior of the material to be useful for any purpose. This is the well-known structure-processing-properties dynamic triangle. 

Thermoplastic polymers are synthetic polymers that become plastic on heating and harden on cooling. PE, iPP, PET, and polyamides, among others, are typical examples of this type of polymers. Depending on the chemical and molecular structure and processing variables, they may or may not crystallize. Thermoplastic polymers that are able to crystallize have a significant amount of amorphous material, and therefore they are known as semicrystalline thermoplastic polymers. 

Guan X and Pitchumani R (2004) A micromechanical model for the elastic properties of semicrystalline thermoplastic polymers, Polym Eng Sci 44 433-451. 

Surveying the literature one recons that nanofillers are less used for amorphous glassy compared to semicrystalline thermoplastic polymers. Moreover, only few reports deal with effects of nanofillers on the toughness of amorphous thermoplastics. The possible reason for this will be disclosed later. 

High-performance semicrystalline thermoplastic polymers such as aromatic poly-etherketones are ideal candidates as matrices in nanocomposite materials dne to their unique combination of high glass transition temperature (Tg), stiffness, strength, tongh-ness, chemical and solvent resistance, thermo-oxidative stability, flame retardancy, low... 

In the case of poly(alkoxyphosphazenes) (IV) or poly(aryloxyphos-phazenes) (V) a dramatic change in properties can arise by employing combinations of substituents. Polymers such as (NP CHjCF ) and (NP CgH,).) are semicrystalline thermoplastics (Table I). With the introduction of two or more substituents of sufficiently different size, elastomers are obtained (Figure 4). Another requirement for elastomeric behavior is that the substituents be randomly distributed along the P-N backbone. This principle was first demonstrated by Rose (9), and subsequent work in several industrial laboratories has led to the development of phosphazene elastomers of commercial interest. A phosphazene fluoroelastomer and a phosphazene elastomer with mixed aryloxy side chains are showing promise for military and commercial applications. These elastomers are the subject of another paper in this symposium (10). 

A truncation of the term thermoplastics. Generally organic materials which in the manufacturing stage are caused to flow by the application of heat and pressure and thus take up a desired shape, which shape is retained when the applied heat and pressure are removed. Plastics are high polymers and are classified into amorphous and semicrystalline thermoplastics and thermosetting materials. 

Semicrystalline polymers, 20 351, 352, 588 toughness of, 20 354 Semicrystalline resins, 19 537 Semicrystalline thermoplastics, melting temperature of, 19 538t Semiefficient (semi-EV) sulfur... 

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. 

The phenomenological ordering of polymers projected for use as constructing materials is not an easy matter. Sometimes the temperature stability is used as a criterion, i.e., the temperature up to which the mechanical properties remain more or less constant. Another attempt for classification, uses the E modulus or the shape of the curve of stress-strain measurements (see Sect. 2.3.5.1). In general one can say that semicrystalline thermoplastics are stiff, tough, and impact-resistant while amorphous thermoplastics tend to be brittle. Their E... 

The time needed for polymer chains of amorphous thermoplastics above Tg and semicrystalline thermoplastics above Tm to diffuse across the interface and randomize is relatively short compared with the time needed for resin flow. It is believed, therefore, that diffusion bonding is completed immediately after the two molten surfaces merge, and that the microstructure of the contact zone is also assumed to be identical to that of the intraply sections [12,13],... 

Following the requests to increase toughness by keeping a high Tg, for several applications (the aerospace industry in particular), high-Tg or semicrystalline thermoplastics (TP) can be used instead of rubbers to modify thermosetting polymers (Hedrick et al., 1985 Pearson, 1993 Hodgkin et al., 1998 Pascault and Williams, 2000). 

The speed at which crystalline structures grow depends on the type of polymer and on the temperature conditions. Table 1.3 shows the maximum growth rate for common semicrystalline thermoplastics as well the maximum achievable degree of crystallinity. 

Linear non-thermoplastic polymers, 28 Linear thermoplastic semicrystalline polymers, 29 Liquid crystalline polymers, 35, 38,176,177, 350, 581,582, 634 melts, 581... 

Gaymans RJ (2000) Toughening semicrystalline thermoplastics. In Paul DR and Bucknall CB (eds) Polymer Blends, Vol 2. Wiley, New York p 177... 

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