Blending section

In all polymer plants, the polymer pellets show a slight fluctuation in properties. In this section, the SPS pellets are blended and transferred to homogeneous lots. 

The SPS pellets are sent to the pellet blend silo (V-700A,B) and are blended. After blending, the SPS pellets are sent to the pellet silo. 

The polymeric solution subsequently goes to a blending section comprising storage vessels of different sizes. Batches are blended following plant specific blending rules. Obviously product analyses are essential in this process in order to check whether the batches are on specification. Product additives like stabilisers and extender oils can also be added in this section. 

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This chapter is organized as follows. Section 6.2 is concerned with experiments on binary block copolymer/homopolymer blends, Section 6.3 deals with experiments on ternary blends containing a block copolymer and in Section 6.4 experiments on binary blends of block copolymers are reviewed. Theory for the corresponding type of blend is discussed successively in Sections 6.5 to 6.7. Finally, experiments on thin films are discussed in Section 6.8, separately from the work on bulk blends, in keeping with earlier chapters. 

From the microhardness behaviour during the strain-induced polymorphic transition of PBT, differences were found for the three above described systems. The common characteristic feature among PBT (Section 6.2.1), its copolymer PEE (Section 6.2.2) and the PBT/PEE blend (Section 6.2.3) is the relatively sharp (within 2-4% of deformation) stepwise decrease in H (typically by 20-30% of starting H value). This drop appears at different deformation intervals for PBT the sharp decrease occurs between 5-8% (Fig. 6.2), for PEE it appears between 25-30% (Fig. 6.5), while for the blends one observes two sharp decreases with increasing strain (Fig. 6.8). The first 20% decrease in the starting H value coincides with the deformation interval... 

If one of the component polymers has a third spin other than and H, several cross-relaxation experiments become possible. Since spin diffusion occurs a few 10 nm before the polarization decays, only a small amount of the spins near the interface must be detected for immiscible blends. Section... 

The melting behavior of miscible crystallizable blends (section 3.3.5) is often complex, revealing multiple DSC endotherms, which can be ascribed to several causes such as recrystallization, secondary crystallization, liquid-liquid phase separation (3.3.6), etc. 

A discussion of the ABS/PC blends comparing with other ABS blend, may be found under the ABS blends section. The properties of the ABS/PC blends, primarily the DTUL and impact strength, are determined by the ratio of ABS to polycarbonate. The morphology is also dictated by the blend ratio. In blends containing > 50% polycarbonate, the continuous phase is formed by the polycarbonate with ABS as the dispersed... 

PPE/HIPS blends filled the price-performance gap between the styrenic resins (HIPS, ABS) and the engineering resins such as polycarbonate, polyarylate and polysulfones. The technology and applications of PPE/HIPS blends have already been discussed under the styrenic resin blends section (Table 15.3). 

The crosslinking reaction may be catalyzed by a small amount of suitable organometalUc catalysts. The blends typically contain ca. 5-20% silicone. Injection molded or extruded parts are further heat-treated to complete the curing reactions. There is, of course, a significant level of phase separation. In the thermoplastic molding compounds such as glass-filled PA and PBT, addition of the silicone semi-IPN in small amounts (ca. 5-10%) is reported to reduce the mold shrinkage, improve mold release, and increase wear and friction resistance. Polyamide-silicone blends have already been discussed under PA blends section. 

We begin in Section 9.2 with the morphology in binary blends of iPP and various rubbery olefin copolymers where we remark the interrelation between the miscibility and dynamic mechanical properties. Section 9.3 describes the molecular orientation behavior under tensile deformation of iPP-based blends, and we compare the differences in deformation behavior between miscible and immiscible blends. Section 9.4 contains the solidification process in iPP-based blends where the effects of miscibility in the molten state on the crystallization of iPP matrix are discussed. 

Since the early discovery of miscibility between the low-cost polystyrene and PPE, several commercial grades of PPE/HIPS have been developed, which offer a wide choice of heat resistance (DTUL), impact strength, and melt processability (Cizek 1969 Fried et al. 1978). This versatility of PPE/HIPS blends led to their unparalleled commercial success, accounting for nearly 50 % of market volume of all engineering polymers commercial blends. PPE/HIPS blends filled the price-performance gap between the styrenic resins (HIPS, ABS) and the engineering resins such as polycarbonate, polyarylate, and polysulfones. The technology of PPE/HIPS blends has already been discussed previously under the styrenic blends section (Sect. 19.3), and the typical blend properties are shown in Tables 19.6 and 19.32. 

Commercial PPE/P A blends were developed by the motivation to combine the high heat resistance characteristics of PPE with the chemical resistance characteristics of the crystalline polyamide polymers (PA-66 and PA-6). Because of the inherent incompatibility between PPE and polyamides, suitable methods of compatibilization and toughening have not been developed until recently. The technology of compatibilized, impact-modified PPE/PA blends have already been discussed under polyamide blends section (Sect. 19.7). Commercial PPE/PA blends are based primarily on the lower-cost polyamide (PA6 and PA66) and most often include a rubbery impact modifier as the third blend compraient, added for a desired level of toughness (Tables 19.25 and 19.32). 

In the polymer blend section, we considered mixtures of homopolymers and/or random copolymers. However, the combination of homopolymers and block copolymers is equally important. Suitable block copolymers at the interface between two incompatible polymers will lower the interfadal tension and, thus, improve the dispersion of one polymer in the other (see Reference 49 and references therein). For practical applications, the critical issues are the synthesis of suitable block copolymers and the concentration of the block copolymers at the interface. In practice, compatibilization is, therefore, often achieved by forming block or graft copolymers in situ during blend preparation by, for example, interfadal reactions. 

Feed and transfer section—valves, piping, tanks, solids feeders, compressor Blending section—additive blenders, homogenizer Extrusion section—extruder, pelletizer, pipes, valves, pumps Drying section—dryer, classifier... 

Figure 3.9 Masterbatch natural polymer blend section based on a microtomed xlOO photomicrograph. Reproduced with permission from M. Penny, Roller Bearing Mixer for Extrusion of Carbon Black with Polyolefines, Rapra Members Report NoA5, Rapra Technology, Shawbury, Shrewsbury, UK, Figure 3.10.

The SPS process is divided into eight sections. They are monomer purification section, catalyst section, polymerization section, styrene removal from SPS, deactivation section, pelletizing section, blending section, and shipping section. Each section will be explained from the patent information. 

Figure 12.11 shows the flow diagram of the blending section. 

In this chapter, we have described the behavior of ternary systems. This includes ternary low molecular weight systems (Section 6.2). Polymers with two low molecular weight liquids (Section 6.3) binary polymer blends with a low molecular weight liquid (Section 6.4), binary polymer blends with amphiphilic molecules or block/graft copolymers (Sections 6.5 through 6.7), high impact polystyrene (Section 6.8) and ternary polymer blends (Section 6.9). 

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