R-TPOs

In addition to the two-phase TPEs, two new technologies have emerged. They are the metallocene-catalyzed polyolefin plastomers (POPs, the name given to Exxon s EXACT product line) and polyolefin elastomers (POEs, DuPont Dow Elastomer s ENGAGE), and reactor-made thermoplastic polyolefin elastomers (R-TPOs). These new types of TPEs are often called metallocene elastomers-TPEs (MEs-TPEs) [87]. The new POPs and POEs are essentially very low-molecular-weight-Unear low-density PEs (VLMW-LLDPE). These new-generation TPEs exhibit mbber-like properties and can be processed on... 

The first reactor-type thermoplastic polyolefin (R-TPO) was LLDPE/PP [Yamazaki and Eujimaki, 1970, 1972]. The three-component R-TPO s (PE with PP and EPR) soon followed [Strametz et al, 1975]. PE was also polymerized in the presence of active catalyst and an olefinic copolymer [Morita and Kashiwa, 1981]. Blending amorphous co-polyolefins with crystalline PO s (HDPE, LLDPE, PP), and a filler resulted in moldable blends, characterized by excellent sets of properties [Davis and Valaitis, 1993, 1994]. Blends of polycycloolefin (PCO) with a block copolymer (both polymerized in metallocene catalyzed process) and PE, were reported to show outstanding properties, viz. strength, modulus, heat resistance and toughness [Epple and Brekner, 1994]. 

Reactor-blends PE with PP and EPR reactor- thermoplastic polyolefin, R-TPO Yamazaki Eujimaki, 1970... 

Rheopexy Ribbon blenders Rigid-rod polymers Rockwell hardness Rotating disc mixer R-TPO (Reactor-type TPO) SAA (Styrene-co-acrylic acid)... 

Ziegler-Natta catalyst makes it possible to polymerize a-olefins into elastomers with controlled degree of crystallinity and cross-likability. The first EPR s were manufactured in 1960, 3 years later, the first EPDM. It is advantageous to produce block copolymers with PP being the rigid and PE the soft block. A direct sequential polymerization of propylene and ethylene-propylene mixture leads to the reactor blends (R-TPO) (Cecchin and Guglielmi 1990). 

A patent on reactor-blended thermoplastic olefinic elastomer, R-TPO, was disclosed. Thus, PE was polymerized in the presence of an active catalyst and an already polymerized olefinic copolymer (e.g., ethylene-co-1-butene) or the sequence was reversed. The blend had superior resistance to environment stress cracking, and the blown film showed few fish eyes... 

Semicrystalline polyolefin blends were prepared by mixing two different random copolymers of propene with 4-lOC alpha-olefin at a ratio from 1 3-1 1. The first copolymer contained 1-10 wt% of C4 io alpha-olefin (1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene), whereas the second 15 0 wt% of the same comonomer. The mixing was carried out in reactors, polymerizing the monomers in the presence of stereospecific catalysts supports on active magnesium dihalides, in at least two sequential stages. The resulting R-TPOs showed limited... 

Polypropylene, PP, was reactor blended with polyethylene, PE, and ethylene-q>ropyltaie copolymer, EPR, to give high impact stnaigth R-TPO, especially at low temperature... 

The first patent on reactor-blended thermoplastic olefinic elastomer, R-TPO, was disclosed. 

Keywords blends, alloys, miscibility, compatibilization, crystallization, nucleation, polyethylenes (PE, LDPE, LLDPE, HOPE, UHMWPE), EPR, EPDM, ethylenevinylacetates (EVAc), EVAl, EVAc-VC, PB, PIB, styrenics (SBS, SEBS), PVC, PDMS, TPO, R-TPO, metallocene grades. 

Polyolefins, PO. First impact modification of PO, by addition of elastomers, was patented independently by Bayer A.-G. and Standard Oil Co. in 1937. The isotactic polypropylene, PP, was commercialized in 1957, and its first blends (with polyisobutylene, PIB, and polyethylene, PE) were patented in 1958. In 1960, du Pont started manufacturing ethylene-propylene, EPR, and three years later ethylene-propylene-diene, EPDM, copolymers [Gresham and Hunt, I960]. The first patent on impact modification of PP by addition of EPR dates from 1960. Direct reactor blending of PE/PP/EPR resulting in a thermoplastic polyolefin, R-TPO, dates from 1979. The newest (introduced in 1992) single-site metallocene catalysts generate polymers with controlled tacticity, co-monomer sequences, molecular... 

Performance of EFM attached to a singe-screw extruder, SSE, was evaluated examining its suitability for 1. Dispersion of viscous polymer in low viscosity matrix (where X > 4) 2. Impact-modification of engineering resins 3. Elimination of gel particles from either R-TPO or EVAc reactor powders 4. Dissolution of UHMWPE in HDPE, etc. For comparison, the blends were also pr ared using a co-rotating, intermeshing twin-screw extruder, TSE, equipped with high dispersion screws [42, 43 ]. 

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