Blends of Amorphous and Semicrystalline Polymers

For some blends containing one or more amorphous polymers together with one or more semicrystalline polymers, the phase distribution and the interface are demonstrated using electron microscopic techniques in combination with different preparation methods. Additionally, deformation and fracture structures are presented  

LDPE/PS blend, grafting styrene via y irradiation onto PE [7]  

PS/LDPE (75/25) blend, polymerization of styrene in LDPE with PS particles in an LDPE network, fracture surface [8, 9] see Figs. 4.32 and 4.33  

---

As a route for improving the melt-elongational properties of semicrystalline polymers, Siripurapu et al. [7] proposed the blending of amorphous and semicrystalline blends of PS and PVDF nevertheless, their approach showed only limited success. In contrast, Reichelt et al. [29] successfully developed blends of HMS-PP and PP-fe-PE block copolymers. As could be shown, the melt strength increases with the HMS-PP content, while blends rich in HMS-PP also show the lowest densities. 

Novel Composites from Blends of Amorphous and Semicrystalline Engineering Thermoplastics with Liquid-Crystalline Polymers... 

The crystallization of blends tends to depend on the level of mutual miscibility of the components. In miscible blends, the general result is that suppression or otherwise of crystallization with miscibility is dependent on the relative glass transition temperatures of both phases [33, 34]. For example, in a blend of an amorphous and semicrystalline polymer, if the amorphous material has the higher Tg, the miscible blend will also have a higher Tg than that of the semicrystalline homopolymer and, at a given temperature, the mobility and thus the efficacy of the semicrystalline phase molecules to crystallize is reduced. The converse is often true if the amorphous phase has a lower glass transition. Effects such as chemical interactions and other thermodynamic considerations also play a role and the depression of the melting point in a miscible blend can be used to determine the Flory interaction parameter x [40]. 

Polymer blends, including blends of amorphous polymers, amorphous and semicrystalline polymers, semicrystalline polymers, and rubber blends... 

Practical problems associated with infrared dichroism measurements include the requirement of a band absorbance lower than 0.7 in the general case, in order to use the Beer-Lambert law in addition infrared bands should be sufficently well assigned and free of overlap with other bands. The specificity of infrared absorption bands to particular chemical functional groups makes infrared dichroism especially attractive for a detailed study of submolecular orientations of materials such as polymers. For instance, information on the orientation of both crystalline and amorphous phases in semicrystalline polymers may be obtained if absorption bands specific of each phase can be found. Polarized infrared spectroscopy can also yield detailed information on the orientational behavior of each component of a pol3mier blend or of the different chemical sequences of a copoljnner. Infrar dichroism studies do not require any chain labelling but owing to the mass dependence of the vibrational frequency, pronounced shifts result upon isotopic substitution. It is therefore possible to study binary mixtures of deuterated and normal polymers as well as isotopically-labelled block copolymers and thus obtain information simultaneously on the two t3q>es of units. 

Engberg and coworkers [14,98] investigated the blends of thermotropic PLCs with fully amorphous polymers polyethersulfone (PES), polycarbonate (PC) and aromatic poly (ester carbonate) (APEC) [98] and semicrystalline polymers like polybutylene terephthalate (PBT) [14]. aL was calculated according to the Takayanaga model [101] as follows ... 

---