Ethylene blocks

Polylphenylene oxide) Styrene-ethylene block copolymer... 

The observed reversal in the thermal stability of the copolymer at a critical composition, which appears to be between 30 and 40 mol% of ethylene, may be explained on the basis of the emergence of phase-separation between the nonpolar ethylene and polar vinyl chloride blocks. Although crystallization of the ethylene blocks in the copolymer is only observed when more than 70 mol% ethylene units are present, the possibility of phase-separation occurring at lower contents of ethylene units cannot be excluded. Also, round about the critical copolymer composition, the Tg of the copolymer may be reduced to a level that would facilitate separation between the unlike phases by increased molecular mobility within the polymer matrix. As has been discussed earlier, occurrence of phase-separation in the copolymer would not only make the mechanism of stabilization due... 

Composition of the terpolymers as expressed in mole%, of course, must be kept in the range that yields good elastomeric properties. E-E polymers of higher ethylene content naturally result in higher tensile strength as a consequnece of formation of partial crystallinity due to short ethylene blocks (f ). of EEDMs studied in this work all abide by the usual EEDM requirements. ... 

Mean-field lattice theory proved to be capable of predicting the phase behaviour of the ternary block copolymer polyethylene-b-poly(propylene oxide)-b-poly(ethylene oxide), PE-b-PPO-b-PEO in the selective solvent water [164], The ethylene block is known to be highly hydrophobic, and its hydrophobicity does not depend strongly on temperature. The difference in hydrophobicity between PPO and PEO, on the other hand, is moderate... 

Polyallomer Ethylene block copolymers Eastman Chemical... 

Styrene-butadiene block copolymer Styrene-isoprene block copolymer Styrene-ethylene block copolymer Styrene-butylene block copolymer... 

Chiu, H.-T. Chiu, W.-M. The toughening behavior in propylene-ethylene block copolymer filled with carbon black and styrene-ethylene butylene-styrene triblock copolymer. Mater. Chem. Phys. 56, 108-115 (1998). 

Commercial polymer with an overall CTFE-to-ethylene ratio of 1 1 contains ethylene blocks and CTFE blocks of less than 10 mol% each. The modified copolymers also produced commercially exhibit improved high-temperature stress cracking. Typically, the modified copolymers are less crystalline and have lower melting points.88 Modifying monomers are hexafluoroisobutylene (HFIB), perfluorohexylethylene, and perfluoropropylvinyl ether (PFPVE).89... 

The copolymerization of ethylene and chlorotrifluoroethylene is performed as a free radical suspension process in aqueous media at low temperatures. Lowering the temperature reduces the number of ethylene blocks in the polymer backbone that are susceptible to thermal degradation. A commercial polymer with an overall CTEE-to-ethylene ratio of 1 1 contains ethylene blocks and CTFE blocks in the proportion lower than 10 mol% each [85], Reaction pressure is adjusted to give the desired copolymer ratio [86]. Typical pressures during the process are on the order of 3.5 MPa... 

Even at high styrene incorporation, the co-polymers are formed by ethylene blocks and isolated styrene units.627 Half-sandwich titanium complexes such as 35-39 have also been reported to be active in the ethylene/styrene co-polymerization. The performance of the MAO-activated complex 35 is highly dependent on the Al/Ti ratio. At a ratio of 100, a co-polymer composed of polyethylene blocks with essentially isolated styrene units could be fractionated from the homopolymers. By contrast, at Al/Ti ratios of 1000, a co-polymerization at the same feed ratio resulted in the production of only homopolymers, or co-polymers composed of long PE and sPS blocks at most.628 Subsequent 13C NMR analysis of the co-polymers obtained at 20°C indicated that up to 36 mol% of styrene was incorporated.629 However, under very similar conditions, only formation of the homopolymers was reported.630,631 This may be reasonable since catalytic systems 35/MAO and 36/MAO give rise to several active species with different catalytic properties. Thus, remarkably different results can be obtained with small differences in the experimental procedure. 

The complex is also active in ring-opening metathesis polymerization of 1,5-cyclooctadiene (COD), where the ruthenium—carbene bond is now the initiating point. Therefore, a mixture of MMA and COD undergoes a dual or tandem living polymerization of both monomers to generate block copolymers of COD and MMA, which can be converted into ethylene-block-MMA copolymers on subsequent hydrogenation, also catalyzed by the complex. 

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.

Poly( Af- isopropylacrylamide) - poly [ N-acetylimino)ethylene] block copolymer (80 wt% Af-Isopropylacrylamide)... 

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... 

Poly(ethylene-CO-vinyl alcohol) is a thermoplastic used extensively in laminates for food containers due to its excellent film forming and oxygen barrier properties. Limited evidence for the disappearance of the polymer was provided [93]. Whether or not the copolymer is biodegradable is apparently related to the size and distribution of the ethylene blocks. 

Propylene/ethylene block copolymer, 10% ethylene, 416 Novolen 3200 HX... 

Synonyms Ethylene glycol/propylene glycol block copolymer POE/POP copolymer Polyor hylene/polyoxypropylene copolymer Polyoxypro-pylene/polyo) ethylene block polymer Polyoxypropylen polyoxyeth-ylene copolymer POP/POE copolymer Frnnula (CjHsO CjHjO),... 

Hossain, M.K., Hinata, S., Lopez-Quin-tela. A., and Kunieda, H. (2003) Phase behavior of poly(oj ethylene) poly(oxypropylene) poly(oj ethylene) block copolymer in water and water-C12E05 systems./. Dispersion Sci. Technol, 24,441 22. 

The presence of starch improves the biodegradation rates of these synthetic polymers, where a fundamental role is also played by size and distribution of ethylene blocks. Attempts to speed up the biodegradation rate by modification of EVOH copolymers with carboxyl groups have been pursued but the degradation rate of thermoplastic starch and EVOH composites is too slow to consider them compostable according to international test standards. 

Blends comprising polypropylene, 50-97 wt% PP [or a PP block copolymer with ethylene block], and 50-53 wt % of an ethylene/4-18C alpha-olefin copolymer [a-olefin content = 10-60 wt%, p < 913 kg m obtained by using a metallocene catalyst and aluminoxane] were found useful as automobile trims and trims of electrical instruments. They showed high moldability, improved impact resistance at room and low temperature, and balance of rigidity and impact resistance... 

Blends comprising polypropylene, 50-97 wt% PP [or a PP block copolymer with ethylene block], and 50-53 wt% of an ethylene/C ig alpha-olefin copolymer [a-olefin contenr = 10-60 wt%, p <... 

The four modifiers are Halar [66], SM-1 [67], SM-2 [68], and SM-3 [69]. Halar-modified diaphragms are called HAPP diaphragms (i.e.. Hooker Asbestos Plus Polymer) [70]. These contain about 5% of a predominantly alternating E-CTFE copolymer. The commercial resin melts at about 245°C and contains 82% alternating units, 8% ethylene blocks, and 10% chlorotrifluoroethylene blocks [71]. SM-1 is an extruded PTFE fiber... 

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