Metallocene plastomers

The need to paint the blends has also resulted in new painting systems. Recently, a nonpolar color coat based on a hydrogenated polybutadiene diol and melamine resin for TPO bumper fascia was invented. The breakthrough technology allows the elimination of the TPO pretreatment step such as adhesion promoter, flame, or plasma during manufacturing. The paintability of two different types of E-plastomers was evaluated. The olefinic white paint was found to provide excellent paint adhesion for both types of metallocene plastomers. Paint peeling was not observed in any of the test... 

Wilkinson and Lamb 1999). The use of DEHP in domestically produced teethers and rattles has been discontinued (Consumer Product Safety Commission 1999d). DEHP is also no longer used as a plasticizer in plastic food wrap products (Mannsville Chemical Products Corporation 1999). In addition, some applications, like automobile upholstery, might switch from DEHP to linear phthalates because of their superior performance and low toxicity, which will put further downward pressure on DEHP use (Mannsville Chemical Products Corporation 1999). Finally, in the future, polyolefin metallocene plastomers might replace flexible applications for PVC altogether because they provide flexibility without the need for plasticizers. 

POEs or metallocene plastomers in pellet form are easier to handle and process than standard rubbers. They have displaced about 70% of the traditional EPDM modifiers used in TPOs, though EPDM-modified materials still have advantages for low-temperature impact applications. Still, metallocene/POE technology is probably the most important impact-enhancing technology developed over the last 20 years. 

Impact-modifying additives designed to inaease the drop impaa resistance of rigid PP containers, for example, may also be chosen for how they affea darity. PO bottles require low-temperature drop-impact properties in particular, which can be enhanced with additions of metallocene plastomer modifiers. However, these modifiers can create haze if they have shown large enough differences in refractive index with the base resin. Specifically, in tests of HDPE bottles, plastomers with lower densities ( 0.900) were found to affea darity very little (20%-24% haze), whereas a 0.910-density plastomer produced "noticeable" haze (37%) [10-22]. 

Compounders responded by developing new TPOs based on elastomer-modified ICP copolymers. Recently, resin suppliers have introduced even higher elastomer content reactor products called reactor TPOs (RxTPOs) (7). The result has been an ever broadening array of product types and continually improving performance in a variety of applications. The advent of metallocene plastomers (8) for PP modification represents the latest step in this continuous improvement process. 

Metallocene plastomers are plastomers made using metallocene single-site catalysts. Other polyolefins exist in this composition range made with conventional catalysts Dow ATTANE (10), Union Carbide FLEXOMER (11), and Mitsui TAFMER products (12). These are generally called very-low-density poly-ethylenes (VLDPEs) and ultra-low-density polyethylenes (ULDPEs), and are not discussed in this chapter. 

Six companies currently market metallocene plastomers. Exxon Chemical manufactures and markets ethylene-butene and ethylene-hexene copolymers under the EXACT tradename. Dex-Plastomers, a joint venture of Exxon Chemical and DSM, manufactures ethylene-octene copolymers under the EXACT tradename, which are sold by both partners. Dow Chemical and DuPont Dow Elastomers offer ethylene-octene copolymers. Their tradenames are, respectively, AFFINITY and ENGAGE. Japan Polychem manufactures and markets ethylene-hexene copolymers under the KERNEL tradename. Mitsui Petrochemical manufactures propylene, butene, and octene copolymers sold under the TAFMER tradename, along with nonmetallocene plastomers. 

Physical properties of metallocene plastomers span the range between plastics and elastomers. Compared with LLDPE, plastomers are lower in density, tensile strength, fiexural modulus, hardness, and melting point. They exhibit higher elongation and toughness. They are exceptionally clear, with very low haze values... 

One significant deficiency of clarified RCP containers is poor low temperature impact strength. This shortcoming limits the use of RCP in applications such as containers for chilled fruit juices, because containers may fail if dropped when being taken out of the refrigerator. The addition of a metallocene plastomer has been shown to sufficiently toughen containers to minimize this problem while... 

One of the most important applications for impact-modified PP is automotive TPO, commonly used for automotive bumper fascia, external body cladding, and interior trim. Compounds are typically three-component blends of ICP with talc and an impact modifier such as a metallocene plastomer or EPR. The impact modifier provides low temperature toughness but softens the matrix. The talc particles restore the stiffness of the compound but detract from impact strength. The objective of TPO compounding is to select the combination of the three components that provides an optimum balance of stiffness and impact strength. 

The experiment described below was carried out to illustrate the effects of metallocene plastomer and talc on the properties of a TPO composition. Experiments were designed around a typical automotive bumper composition of 60 wt% ICP, 30 wt% impact modifier, and 10 wt% talc (29). 

The response contour surfaces for several key properties were generated using the mixture polynomial to highlight the performance differences of plastomer versus conventional EPR. The metallocene plastomer and EPR provided very similar impact enhancement in both notched Izod and instrumented Impact tests (Figs. 7.25 and 7.26). In all four cases, impact strength depended primarily on the impact modifier and less on the talc content. Flexural moduli were similar for plastomer and EPR compounds (Fig. 7.27). The plastomer formulations showed... 

Metallocene plastomers are already widely used as PP impact modifiers and are positioned to become the leading modifier type in the near future, displacing EPR and EPDM. Plastomers provide equivalent impact enhancement (including at low temperatures) with additional performance advantages including easier dispersion, superior impact in high flow PP resins, and low haze in clarified RCP resins. 

Exact Metallocene plastomer, Exxon Exceed Metallocene linear low-density PE, Exxon... 

Increased hexene content provides lower densities that reportedly yield unparalleled performance from metallocene plastomers. Food-compliant Exact plasto-mers are now offered with densities less than 0.895, and melting points 5-10°C lower than metallocene-based 20 wt% octene copolymers. 

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