The methods of preparation and formation of supermolecular structures in quiescent and sheared melts and the properties of the β-modification of isotactic polypropylene (β-iPP) are reviewed. The introduction of selective β-nucleants is the most reliable method for preparation of samples rich in β-modification or of pure β-iPP. The advantages and drawbacks of the known β-nucleating agents are summarized. It is emphasized that pure β-iPP can be prepared under laboratory and processing conditions in the presence of highly active and selective β-nucleants. Nevertheless, there are no literature data—apart from that of the author's groups—which evidenced unambiguously the formation of pure β-iPP. It hints at the insufficient selectivity of β-nucleants used or at the inappropriate crystallization or melting conditions applied by other scientists. The structure formation during the high-temperature hedritic crystallization is discussed comprehensively and illustrated by polarized light microscopy and scanning ele...

β-MODIFICATION OF ISOTACTIC POLYPROPYLENE: PREPARATION, STRUCTURE, PROCESSING, PROPERTIES, AND APPLICATION

Structure and morphology of poly(propylenes): a molecular analysis

Coatings for implantable devices or endoluminal prosthesis, such as stents, are provided, including a method of forming the coatings. The coatings can be used for the delivery of an active ingredient or a combination of active ingredients.

Coating for Implantable Devices and a Method of Forming the Same

The crystalline structure, spherulitic crystallization and melting behaviour of isotactic polypropylene (iPP) is comprehensively reviewed, illustrated and discussed. It is demonstrated and summarized how the nucleation, development and growth of the different spherulites depend on the crystallization and melting conditions both in quiescent and sheared melt. Based on the results the microtexture development during real processing conditions is elucidated for selected examples. Several subjects of intense debate on the above topics are clarified using evidence from polarized optical micrography and differential scanning calorimetry.

Supermolecular structure of isotactic polypropylene

Polymorphism and isomorphism in biodegradable polyesters

La cristallisation donne les 2 formes cristallines a conformation plane en zig zag. Influence de la vitesse de refroidissement, de la forme cristalline du materiau de depart, de la temperature maximale de l'etat fondu et de son temps de residence a cette temperature sur le polymorphisme

Polymorphism in melt crystallized syndiotactic polystyrene samples

Polymorphism in isotactic polypropylene

The crystal structure of the emptied clathrate form (δe form) of syndiotactic polystyrene, obtained by removing the guest molecules from different clathrate δ forms, is presented Chains in s(2/1)2 helical conformation are packed in the monoclinic unit cell with axes a = 174 A, b = 1185 A, c = 770 A, and γ = 117° according to the space group P21/a The crystalline density of the emptied clathrate form (0977 g/cm3) is lower than that of the amorphous phase (1055 g/cm3) The differences between the structures of the emptied clathrate form and clathrate δ forms are discussed by the analysis of X-ray diffraction patterns and packing energy calculations

Vittorio Petraccone

Papers

Polymorphism in melt crystallized syndiotactic polystyrene samples

Polymorphism in isotactic polypropylene

Crystal Structure of the Emptied Clathrate Form (δe Form) of Syndiotactic Polystyrene

On the crystal structure of the orthorhombic form of syndiotactic polystyrene

Crystal structure of the clathrate δ form of syndiotactic polystyrene containing 1,2-dichloroethane