Toughness semicrystalline matrix

Poly(phenylene sulfide) (PPS) is another semicrystalline polymer used in the composites industry. PPS-based composites are generally processed at 330°C and subsequently cooled rapidly in order to avoid excessive crystallisation and reduced toughness. The superior fire-retardant characteristics of PPS-based composites result in appHcations where fire resistance is an important design consideration. Laminated composites based on this material have shown poor resistance to transverse impact as a result of the poor adhesion of the fibers to the semicrystalline matrix. A PPS material more recently developed by Phillips Petroleum, AVTEL, has improved fiber—matrix interfacial properties, and promises, therefore, an enhanced resistance to transverse impact (see PoLYAffiRS containing sulfur). 

Toughened Polymers with Semicrystalline Matrix. It is well known that toughness of semicrystalline polymers such as PA (polyamide) and PP can be increased similar to the amorphous poljuners by the addition of relatively small amounts of rubber particles such as EPR or EPDM. As in HIPS and ABS, the modifier particles act as stress concentrators, initiating a plastic deformation of matrix strands between the particles as the main energy absorption step. In impact-modified PA and PP at room temperature, plastic deformation takes place through shear deformation (mechanism of multiple shear deformation). 

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. 

The above outlined microstructural efficiency proved to be a valuable tool for upgrading the fracture toughness of short fibres reinforced semicrystalline plastics (SFRPs) by means of evaluation both of matrix and fibres - related failure mechanism [1267]. 

The effect of matrix strand yielding occurs only below a critical interparticle distance which is dependent on the matrix polymer and the temperature and is similar to the concepts of critical interparticle distance and critical thickness seen in rubber-toughened semicrystalline polymers see Chapter 5. Small interparticle distances below the critical size and, therefore, optimum conditions for good toughness are easier to realize with small particles, in particular with nanoparticles [6]. 

The adduced results have shown that loosely packed matrix of devit-rificated amorphous phase and disordered in deformation process crystalline phase part are structural components, defining impact energy dissipation and hence, impact toughness of semicrystalline polymers. The fractal analysis allows correct quantitative description of processes, occurring at HDPE impact loading. It is important, that the intercommunication exists between polymer initial structure characteristics and its changes in deformation process [2, 3]. 

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... 

---