Extruder plastomer

Because of their high shear-thinning and melt elasticity, plastomers and POEs disperse well in the PP matrix yielding fine elastomer domain dispersions leading to the better properties. POEs are easier to handle as they are available in pellet form, whereas EPDM is typically baled and needs additional equipment for feeding into the extruder compounding process. POEs also offer improved melt flow in TPO blends compared to EP copolymer-type elastomers. Currently, POEs account for about a third of the elastomer volume used in the compounded TPOs. 

Plastomer modification of PP continues to progress. Current work in many development laboratories focuses on modification of reactor TPOs to make soft flexible compounds for extruded or calendared sheet. In many such applications flexible PP sheets would replace plasticized polyvinyl chloride (PVC) or PVC blends, chlorinated polyethylene, or EPDM. 

This property is measured by a melt flow index extrusion plastomer, which measures the weight of polymer extruded through a standard orifice in 10 minutes (see Table 16.1). Alternatively, a multi-functional extrusion plastomer that measures melt flow rate resistance to thermal degradation is available. 

Experiments were run with natural and synthetic rubber by using an internal mixer, roll mills, and an extruder. As the gelation is a mechano-chemical process, independent of the elastomer structure, the reaction was applied to plastomers masticated while in the viscoelastic state [188]. The reaction takes place with poly(methyl methacrylate), poly(vinyl acetate), and polyethylene. No evidence for the cross-linking of polystyrene was observed. The addition of aluminum isopropoxide aids the formation of block copolymer. This technique was applied to the system polyethylene-poly(vinyl acetate). 

Table 25 shows typically worst-case torque requirements for four extruder sizes. The range of screw speed represents plastomers at the low end and LDPE at the high end. The specific torque value can be simply mul-tiphed by the maximum screw speed to determine the recommended drive size. The transition from LDPE to plastomers is the most severe. When running LDPE and plastomers on the same machine, field weakening must be used to satisfy the increased screw speed and lower torque requirements of LDPE. The processing performance of narrow MWD, branched, unimodal and bimodal metallocene polymers is illustrated in Fig. 56. 

Extruder Typical screw speed, rev/min LDPE, kW Cast/(rpm) LLDPE, kW/(rpm) mLLDPE kW/(rpm) Plastomer, kW/(rpm)... 

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