Impact modifiers TPVs

Obviously, there exists severe interplastics competition, e.g. PP vs. ABS, clarified PP vs. PS, PA, PVC, HDPE and PS (Table 10.7). A wide range of cross-linked and thermoplastic elastomer applications, from footware to automotive parts and toothbrushes, are adopting new metallocene-catalysed polyolefin elastomers (POEs). These low-density copolymers of ethylene and octene were first accepted as impact modifiers for TPOs, but now displace EPDM, (foamed) EVA, flexible PVC, and olefinic thermoplastic vulcanisates (TPVs). Interpolymer competition may also result from... 

A final word in this short summary of impact modification concerns the amount of imagination compounders and polymer scientists continue to invest in the development of rubber-modified compoimds. Efforts are being made to decrease their compounding costs, to enhance their paintability, and to formulate them to replace more competing materials such as ABS, thermoset rubber, and PVC—thereby allowing more recyclable "aU-olefin" automotive interiors, for example. Recent efforts have even been made to incorporate ground vehicle tire rubber or other "ultrafine rubber particles into PP to create vulcanized elastomeric thermoplastics that cost less than half as much as standard TPVs. Similar concepts will continue to push impact-modified POs into new applications [7-26, 7-27, 7-28]. 

This section discusses elastomeric materials such as thermoplastic elastomers (TPEs), TPVs, and other rubber systems such as thermoset elastomers/rubbers (TSRs) invoked in automotive applications apart from their use as impact modifiers in polymer blends. If one starts from nnder the hood, elastomers are used primarily in belts and hoses, bellows, and gaskets. At the separation between engine compartment and the interior, elastomers are used for sound management. Inside the car, they are used in floors, instrument panel skins, instrument panels for soft touch, gaskets for side mirrors, and so on. Outside the car, they can be fonnd in tires (base tire, treads, side walls) and, finally, they are used in wire and cables and coatings in almost aU parts of the car as needed. 

Polyamides such as PA6 are engineering thermoplastics with high heat and solvent resistance properties and hence make ideal thermoplastic matrix candidates of choice to make high-performance TPVs with dynamically vulcanized mbber blends. Although nylon blends with low rubber content have been known for a long time as impact-modified nylons, as discussed under Sect. 19.7.1, elastomeric TPV blends of polyamide with high rubber content (>60 %) have not been commercially available until recently. Because of their higher thermal and chemical resistance performance, the polyamide-based TPVs have often been called super-TPVs (Leaversuch 2004). 

Among the various other types of PA-TPVs investigated in the literature, PA/EPDM mbber-based TPV is interesting. As will be discussed in more detail, under impact-modified polyamides section (Sect. 19.7.1.1), binary blends of PA6 of EPDM mbbers can be compatibilized via reactive extmsion... 

Santoprene applications of note are a nylon-bondable grade for the General Motors GMT 800 truck air-induction system driveshaft boot in Ford-F Series trucks, giving easier assembly, lighter weight, and higher temperature resistance than the material it replaced and Santoprene cover and intermediate layers of tubing assembly for hydraulic oil hose. Nylon-bondable Santoprene TPV is coextruded with an impact modified (or pure) nylon 6 inner layer. 

The POE/TPV family represents a relatively new class of polymers. They bridge the gap between impact-modified polyolefins (such as toughened PP) and other TPE. They are available in a broad range of hardnesses, with varying levels of stiffness and elongation. As polyolefins, they have excellent chemical resistance to acids, bases, and other aqueous media. Exposure to hydrocarbons can cause swelling due the EPDM component. 

In order to test this idea through numerical simulation first, a modified geometry is generated. Figure 4 shows the position of the flow leader whereas the inlet sections of the polyamide and the TPV are not altered. Figure 5 illustrates the impact of the flow leader onto the flow pattern. Large velocities are locally observed in the TPV inlet channel before the flow leader. Trajectories shown in Figure 6 reveal that particles flow around the flow leader. This distributes the flow of materials in a more balanced manner across the conical section of the die. 

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