Semicrystalline thermoplastic matrix

In semicrystalline thermoplastic matrix composites, the nucleation and growth of a transcrystalline interface around the reinforcing fiber is thought to have a critical influence on the improvement of the stiffness and tensile strength [63-65]. The rheological behavior of in situ microfibrillar HDPE/PET and HDPE/polycarbonate (PC) polymer blends was investigated in a recent study [66,67]. For both HDPE/PET and HDPE/PC microfibrillar blends, the viscosity increased with PET and PC microfibrils concentration. In another study, Xu et al [68] reported that the flexible microfibrils of PET reduced the melt elasticity and viscosity of HDPE/PET microfibrillar blends. 

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. 

Thus, a brief survey of the current understanding of the molecular and super-molecular structures of common thermoplastics is presented first. This review starts with a brief description of the current state-of-the-art knowledge of the constitution, configuration, conformation and supermolecular structure of common glassy and semicrystalline thermoplastics. Later in this chapter, specific features of the structure-property relationships are discussed in greater detail for the most frequently filled thermoplastics. Effects of fillers on the structural variables in polypropylene, considered the most commercially important matrix, are especially emphasized. 

The aim of this work is to study the influence of particle size, interparticle distance, particle volume content, and local stress state on the toughening mechanism in several dispersed systems. The systems consist of a matrix of an amorphous or semicrystalline thermoplastic (see Figure 1). It is necessary to determine whether the particle diameter or the interparticle distance is of primary importance. But it is difficult to check the influence of both parameters because there is an interrelation between D, the average minimum value of A, and the particle volume content, t>P ... 

Materials Studied. The materials investigated are listed in Table I. Different amorphous and semicrystalline thermoplastics were used as matrix materials, which were modified with several types of rubber. The volume content of the rubber and the rubber-particle diameter were changed to enable A... 

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. 

PROPERTIES OF SPECIAL INTEREST Mostly synthesized as flexible semicrystalline thermoplastic, PBT has outstanding resilience and toughness. High toughness and resilience is due to improved chain flexibility derived from the four methylene units. Used in thermoplastic matrix composites for gears, machine parts, small pump housings, and insulators. 

A general statement that should be kept in mind before the individual additives are described is as follows Common to all additives is the fact that their effects depend on their solubility in the specific polymer [29, 30, 33]. The relative parameters are their chemical structure, the temperature, and the crystallinity of the matrix. Additives can only be dissolved, for instance, in the amorphous phase of semicrystalline thermoplastics, in which the additive concentration is increased during cooling from the molten state [33]. This is advantageous in terms of stabilization, since oxygen and solvent atoms are only capable of permeation through the increased lattice vacancies of the amorphous phase with its many defects. 

Ternary nanocomposites contain three components therefore, coimtless combinahons of materials and compositions are encountered in the literature and in practice. Polyolefins are almost always encoimtered as a component in nanocomposite blends, being the matrix, the dispersed phase, or both. Generally, semicrystalline thermoplastics such as polypropylene (PP) and polyethylene (PE) are very popular as the matrix component, while the dispersed phase consists of either another thermoplashc [15-17] or an elastomer [5,18-23]. Polyolefin-based thermoplashc elastomers, such as ethylene/propylene rubber, and other ethylene-based... 

In particulate-filled thermoplastics, the matrix is the load-bearing component and all deformation processes take place in the matrix. Particulate fillers are, in most cases, not capable of carrying any substantial portion of the load due to the absence of interfacial friction as the means of stress transfer. This is evidenced by the lack of broken particles on the surfaces of fractured filled thermoplastics. Hence, it seems appropriate to start this volume with a brief overview of the basic structural levels and manifestation of these levels in governing the mechanical properties of semicrystalline thermoplastics used in compounding. 

The improvements in tensile elongation and toughness of glassy and semicrystalline thermoplastics reinforced with low loadings of functionalized carbon iianotubes are very impressive. An important issue for toughening in functionalized CNT-reinforced polymer composites is the natme of the interface between the iianotube and the matrix as discussed above. The high flexibility and large... 

For instance, crystalline lamellae in an amorphous matrix (semicrystalline polymer materials), hard domains in a soft matrix (thermoplastic elastomers)... 

The model PBZT/ABPBI molecular composite system is limited since the rod and the matrix do not possess glass transition temperatures for subsequent post form consolidation. In an effort to improve the processability for molecular composites, thermoplastics were used as the host matrix. Processing from acidic solvents requires the thermoplastic host to be soluble and stable in meth-anesulfonic add. Thermoplastic matrices were investigated including both amorphous and semicrystalline nylons [71,72], polyphenylquinoxaline (PPQ) [73] and polyetheretherketone (PEEK) [74], Table 5 shows the mechanical properties obtained for various processed PBZT thermoplastic molecular composite systems. As an example, the PBZT/Nylon systems showed 50-300% improvement over uniaxially aligned chopped fiber composite of comparable compositions. However, the thermally-induced phase separation during consol-... 

For instance, crystalline lamellae in an amorphous matrix (semicrystalline polymer materials), hard domains in a soft matrix (thermoplastic elastomers) several sharp peaks of colloidal crystals are observed in the SAXS, the unit cell can be determined. In this case peak profile analysis can be carried out using the methods discussed in Sect. 8.2.5... 

Similarly, in the absence of any phase mixing, the hard phase is a hydrogen-bonded glassy or semicrystalline polymer. Experience of other polymers suggests that Gh i 000 MPa at room temperature [135], But this is a typical value for a macroscopic sample of polymer. In the thermoplastic PUs it must represent an upper bound on Gh, since in this case the hard segments are confined to such small domains that a large fraction of them reside at the particle surfaces, adjacent to the more mobile matrix, again as shown previously in Section 2.3.1. So a lower value is expected for Gh-... 

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