Nucleation of polypropylene

Galeski A (1995) Nucleation of polypropylene. In Karger-Kocsis J (ed) Polypropylene structure, blends composites, vol 1. Chapman Hall, London, p 116... 

Attempts to add fillers to polymer blends produced interesting results. Carbon black was added to a polymer blend containing polycarbonate and polypropylene. Carbon black is known to act as a nucleating agent in polypropylene, however, no increase in the temperature of crystallization was observed. Morphological studies showed that carbon black was preferentially located in the polycarbonate phase therefore it did not affect the nucleation of polypropylene. 

B.R Grady, F. Pompeo, R.L. Sbambaugh, and D.E. Resasco, Nucleation of polypropylene crystallization by single-walled carbon nanotubes, J. Phys. Chem. B, 106, 5852-5858 (2002). 

Further, this chapter provides a survey about the formation of a transciystalline layer in the composite system. The occurrence of transcrystallization was found to strongly depend on the type of chemical treatment of the fiber surface. Predominant nucleation ability was found for unmodified fibers. However, chemical modification of fiber surface slightly depressed the nucleation of polypropylene matrixes. 

Common red quinacridone dye nucleating agent is preferably used for nucleation of polypropylene for light weight polypropylene nets." Dye is added in quantity of 10 to 100 ppm." The same solution was patented for manufacture of polypropylene grids.""... 

Salts synthesized by reacting potassium hydroxide with carboxylic acids are suitable for nucleation of polypropylene compositions. Potassium phenyl borate is a nucleating agent used for this nucleation process. ... 

Galeski, A. (1995) Nucleation of polypropylene, in Polypropylene Structure, Blends and Composites, Vol. 1, (ed. J. Karger-Kocsis), Chapman HaU, London, pp. 116-139. 

Fujiyama, M., Wakino, T., Role of filler particles on nucleation of polypropylene,/. Appl. Polym. Sci. 42 (1991) 2739-2742. 

Grady BP, Pompeo F, Shambaugh RL, Resasco DE. Nucleation of Polypropylene Crystallization by Single-WaUed Carbon Nanotubes. J Phys Chem B 2002 106(23) 5852-8. 

Figure 7. Nucleation of isotactic polypropylene right unnucleated sample.

EFFECT OF TALC ON CELL NUCLEATION IN EXTRUSION FOAM PROCESSING OF POLYPROPYLENE WITH CARBON DIOXIDE AND ISOPENTANE... 

Addition of small amounts of nucleating agents influence the spherulitic crystallization of polypropylene and improve transparency (Sect. 1.3.3.3 and Example 3-20). 

Table 6 Comparison of some relevant properties in tbermoforming between -nucleated PP and other classes of polypropylene. 0 means identical to PP-homopolymer without nucleating agent + means good, ++ very good, - bad, - very bad. The data provided for PP block and random copolymers deal with classical resins. Data taken from Wolfschwenger et al. [49]...

A novel idea for the production of water is by the combination of MD and membrane crystallization [ 139], where the salt is concentrated on the feed side to a point close to super-samration, thereby inducing nucleation of crystals. Recently Gryta and Morawski [140] performed experiments using polypropylene capillary membranes with pore diameters ranging between 0.2 and 0.6 p.m, and 70% porosity. They found crystallization to occur at the membrane surface, but by increasing the distillate temperature to 328 K, the problem was eliminated and stable flux restored. 

Figure 7.18 shows how crystalline structure is affected by the presence of fiber. Here, bamboo fiber was used for polypropylene reinforcement. A nucleation occurs on the surfaces of fiber. Spherulites grow from the fiber surface. Such growth results in transcrystallinity. The maleation of polypropylene increases interaction because of reactivity with OH groups on the fiber surface. This organization contributes to the reinforcement. 

The final example of SCF comminution is a comparison of polypropylene particles out of the bottle and after supercritical fluid nucleation. Instead of carbon dioxide, supercritical propylene at 241 bar (3,500 psia) and 140°C is used to dissolve the sample of polypropylene. Figure 12.5a is a high-magnification SEM of a single parent particle. As shown in figure 12.5b, a very different particle size and shape results from the supercritical fluid process. 

Table 3.28. Overview of the phenomena influencing heterogeneous primary nucleation in polypropylene based immiscible blends (after Bartczak et al., 1995).

The crystallization peak temperature increased when epoxy resin was added to polypropylene, that is, the uncured and cured epoxy particles acted as effective nucleating agents and accelerated the crystallization of PP in the blends. When cured dynamically, the smaller epoxy particles in the blends resulted in the increase in the number of nucleating agents and hence accelerated the crystallization of polypropylene. Blending polypropylene with epoxy resin resulted in the decrease of crystallinity of polypropylene and increased the melting temperature T of polypropylene than those of pure polypropylene. 

The spherulites of polypropylene crystals (80 pm) were larger than those of polypropylene/epoxy blends. This is because epoxy resin particles acted as nucleating sites, increased the number and decreased the size of PP spherulites in the blends. The normalized dynamic DSC cooling curves of polypropylene/epoxy blends are shown in Fig. 21.7 and the data from the DSC studies are summarized in Table 21.5. 

The Effect of Nucleating Agents on the Morphology and Crystallization Behavior of Polypropylene... 

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