Fractionated crystallization copolymers

Figure 1 shows the DSC cooling scan of iPP in the bulk after self-nucleation at a self-seeding temperature Ts of 162 °C (in domain II). The self-nucleation process provides a dramatic increase in the number of nuclei, such that bulk iPP now crystallizes at 136.2 °C after the self-nucleation process this means with an increase of 28 °C in its peak crystallization temperature. In order to produce an equivalent self-nucleation of the iPP component in the 80/20 PS/iPP blend a Ts of 161 °C had to be employed. After the treatment at Ts, the cooling from Ts shows clearly in Fig. 1 that almost every iPP droplet can now crystallize at much higher temperatures, i.e., at 134.5 °C. Even though the fractionated crystallization has disappeared after self-nucleation, it should also be noted that the crystallization temperature in the blend case is nearly 2 °C lower than when the iPP is in the bulk this indicates that when the polymer is in droplets the process of self-nucleation is slightly more difficult than when it is in the bulk. In the case of block copolymers when the crystallization is confined in nanoscopic spheres or cylinders it will be shown that self-nucleation is so difficult that domain II disappears. 

The data of Table 4 clearly indicate that the PEO block within PB-fo-PI-fo-PEO triblock copolymers exhibits fractionated crystallization when it constitutes a minority component. BnI70EOi9 and B24I56EO20 show only one crystallization exotherm, whereas B17I57EO26 has two crystallization exotherms. 

Several alternative methods proposed for lithium recovery from seawater use ion exchange after solar evaporation and fractional crystallization of NaCl, CaS04 and KCl MClj. In these instances, polymeric ion exchangers, such as highly cross-linked Dowex 50 (16% DVB) [110] or Retardion Ag II, A8 (copolymer of styrene and acrylic acid cross-linked... 

Avella M, MartusceUi E, Raimo M (1993) The fractionated crystallization phenomenon in poly(3-hydroxybutyrate)/poly(ethylene oxide) blends. Polymer 34 3234-3240 Avella M, Matruscelli E, Raimo M (2000) Properties of blends and composites based on poly(3-hydroxy)butyrate (PHB) and poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) copolymers. J Mater Sci 35 523-545... 

Abundant reaction of the reactive copolymer with the PA6 seems to reduce the mobility of PA6 chain segments, leading to an increased fractionated crystallization in the PA6 droplets. 

Fig. 5.11 Melting temperature of rapidly crystallized fractions of copolymers of ethylene as determined by differential scanning calorimetry hydrogenated poly(butadiene) (A), ethylene-vinyl acetate ( ), diazoalkane copolymer with propyl side groups (A), ethylene-butene copolymer ( ), ethylene-octene copolymer ( , a).(74)...

Abstract The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial research. One consequence of the development of new tailor-made polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass, molecular topology and chemical composition distribution. This review presents different new and relevant techniques for polyolefin analysis. The analysis of copolymers by combining high-temperature SEC and FTIR spectroscopy yields information on chemical composition and molecular topology as a function of molar mass. Crystallization based fractionation techniques are powerful methods for the analysis of short-chain branching in LLDPE and the analysis of polyolefin blends. These methods include temperature-rising elution fractionation, crystallization analysis fractionation and the recently developed crystaUization-elution fractionation. 

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