Ethylene-butene block copolymer

Figure 3. Oxidation patterns of molded linear polyethylene (M > l(fi) and an ethylene-butene block copolymer...

THERMAL PROPERTIES OF AN ETHYLENE-1-BUTENE BLOCK COPOLYMER. 

A similar procedure affords 1,2-butene oxide-propylene oxide and l,2 -butene oxide-ethylene oxide block copolymers, both with narrow molecular weight distribution. The formation of these block copol3nners confirms the living nature of the epoxide polymerization by TPPAICI. 

Hydrogenated poly(butadiene), an ethylene-butene random copolymer, is often used as die crystallizing block, in di- and triblock copolymers. In this context the copolymer is commonly referred to as polyethylene. This nomenclature can be misleading since it carries the connotation that hydrogenated poly(butadiene) behaves as a homopolymer with respect to crystallization. In fact, it behaves as a typical random copolymer that is located within the structure of an ordered copolymer. 

The block that is usually termed ethylene is really a hydrogenated poly(butadiene), i.e. ethylene-butene random copolymer. 

Styrene-Butadiene-Styrene Block Copolymers. Styrene blocks associate into domains that form hard regions. The midblock, which is normally butadiene, ethylene-butene, or isoprene blocks, forms the soft domains. Polystyrene domains serve as cross-links. 

As opposed to the problems associated with the formation of sequential block copolymers, the preparation of relatively random copolymers is much easier and the provision of polyethylenes having a controlled degree of branching by copolymerization with propylene and butene is now a well-established commercial operation. When ethylene and propylene are employed in approximately equal proportions the ethylene-propylene rubbers are obtained. For this purpose strictly random copolymers are desirable, for which soluble vanadium catalysts are often preferred (20). With TiCls-based catalyst the propylene monomer molecule prefers to add to a propylene end unit rather than to an ethylene end unit (and vice versa). This tends to produce nonrandom blocky copolymers. Thus a recent paper by Coover ef al. (21) selects as catalysts formulations which maximize this tendency and achieve the preparation of block copolymers in a TiCl3/AlEt2Cl catalyst system in the presence of butene and propylene together. 

SEBS styrene-ethylene/butene-styrene three block copolymer... 

Figure 7.13. The experimental (points) and computed from Equation 7.80 relation between viscosity and composition for polypropylene blends with styrene-ethylene-butene-styrene block copolymer [Steller and Z uchowska, 1990].

Figure 8.14. Persistence length of crystal lamellae (A) PE (quenched), ( ) 50/50 PE/CEBC blend (T = 110°C), (A) 50/50 PE/CEBC blend (T = 75X), (O) 50/50 PE/CEBC blend (quenched). CEBC is ethylene-(ethylene-co-butene)-ethylene block copolymer [Takagi et al., 1998.

As discussed earlier, ethylene propylene rubber (EPR or EPM) has been blended with PP and PE to improve the impact strength and to render the materials softer. Recently, metallocene catalysts or postmetallocene catalysts provide new pathways to generate elastic copolymers that can replace EPR. These pathways possess cheaper manufacturing cost and generate new materials with better compatibility to PP or PE. Such new materials included ethylene-propylene random copolymers with dominant ethylene component (33-34) or propylene-dominant component (35 1), propylene-ethylene block copolymer (42), ethylene-octene copolymer (43), poly(propylene-co-ethylene) (44), ethylene-hexene copolymer (45), ethylene-butene copolymer (46), low isotactic PP (47), and stereoblock PP (48). These materials are generally compatible with PP or PE, thus can be used to tailor the toughness (or the softness) of... 

A comparative study of MAH and diethyl maleate grafting—initiated by DCP—to styrene-(ethylene-butylene)-styrene triblock copolymer (SEES) and PS blended with a random ethylene-1-butene copolymer has been described elsewhere (66). The weight ratio of PS to PO components in the block copolymer was the same as in the blend (20% PO and 80 wt% PS). The analysis of the functionalized PS/PO blend—after PS had been extracted in a solvent—showed that the monomer was grafted only to the PO component. Considering that the PS/ PO blend and SEES have quite similar phase and molecular structures, it was concluded that in styrene-containing block copolymers only aliphatic blocks become functionalized. 

The copolymerization of ethylene and 5% butene-1 or hexene-1 by the Phillips method gives a product which is resistant to stress craze corrosion. Under standard test conditions, this resistance is increased with 190 to 2000 h. A block copolymer of propylene with a small ethylene content can replace rubber-modified, unbreakable poly(propylene). 

TiCl2 Et2AlCl catalyst Using this catalyst, or a similar catalyst, block copolymers of the following monomep pairs have been prepared l-butene-ethylene(59) l-.t)utene-propylene(60) ethylene-... 

Many different block copolymers of olefins, like ethylene with propylene and ethylene with butene-1, are manufactured. Use of the anionic coordination catalysts enables variations in... 

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