Linear ethylene/octene copolymer

Figure 19 (a) Peak melting temperature as a function of the branch content in ethylene-octene copolymers (labelled -O, and symbol —B (symbol, ) and -P (symbol, A) are for ethylene-butene and ethylene-propylene copolymers, respectively) and obtained from homogeneous metallocene catalysts show a linear profile, (b) Ziegler-Natta ethylene-octene copolymers do not show a linear relationship between peak melting point and branch content [125]. Reproduced from Kim and Phillips [125]. Reprinted with permission of John Wiley Sons, Inc. 

The effect of blending LDPE with EVA or a styrene-isoprene block copolymer was investigated (178). The properties (thermal expansion coefficient. Young s modulus, thermal conductivity) of the foamed blends usually lie between the limits of the foamed constituents, although the relationship between property and blend content is not always linear. The reasons must he in the microstructure most polymer pairs are immiscible, but some such as PS/polyphenylene oxide (PPO) are miscible. Eor the immiscible blends, the majority phase tends to be continuous, but the form of the minor phase can vary. Blends of EVA and metallocene catalysed ethylene-octene copolymer have different morphologies depending on the EVA content (5). With 25% EVA, the EVA phase appears as fine spherical inclusions in the LDPE matrix. The results of these experiments on polymer films will apply to foams made from the same polymers. 

Figure 10.15 The decay of the transverse magnetisation (points) for ethylene-octene copolymer at different temperatures [136]. The decay was measured using the solid-echo pulse sequence. The solid lines represent the result of a least-squares adjustment of the decay using a linear combination of Weibull and exponential functions. The dotted lines represent the relaxation component with a long decay time. In the experiments the sample was heated from room temperature to 343 K (70 °C)...

In a similar manner, the ethylene-octene copolymer crystallized directly via the orthorhombic phase without the intervention of the anticipated hexagonal phase as would be anticipated in linear polyethylenes at these high pressures and temperatures (at approximately 3.8 kbar and around 200 °C). At 100 °C, see Fig. 15, the d values for (110) and (200) orthorhombic reflections are 4.08 A and 3.71 A. When the sample is cooled below 100 °C, a new reflection adjacent to the (110) orthorhombic peak appears at 80 °C. The position of the new reflection is found to be 4.19 A and so corresponds to a new phase. No change in the intensity of the existing (110) and (200) reflections is observed, however the intensity of the amorphous halo decreases, which suggests that the appearance of the new reflection (d = 4.19 A) is solely due to the crystallization of a noncrystalline component. On cooling further as the new reflection intensifies, the (110) and (200) orthorhombic reflections shift gradually. However, at 50 °C, the (100) monoclinic reflection appears with a concomitant decrease in the intensity of the (110) orthorhombic reflec-... 

FIGURE 39.3. Secondary nucleation plot for linear polyethylene (LPE) and ethylene-octene copolymers (isothermal data-filled symbols rapid cooling data-open symbols). For copolymers, L and H indicated low and high MW, respectively, and the number following the letters represents the number of hexyl side chains per 1,000 carbon atoms. Reproduced from [Polymer] (2001) [19] with permission from Elsevier. 

In the USA Exxon Chemical and Dow Plastics were the leaders in the metallocene technology. While Exxon explored both mono- and bis-cyclopentadienyl metallocenes, Dow focused on constrained geometry catalysts based on Ti-monocyclopentadienyl metallocenes. Exxon first produced metallocene-based polymers with its Exxpol catalysts in 1991. Dow uses its INSITE technology to make ethylene-octene copolymers, introduced in 1993. Copolymers with up to 20 wt% octene are sold as AFFINITY plastomers, competing with specialty polymers in packaging, medical devices, and other applications. Dow, producing its own catalyst, considers that it leads to the uniform introduction of comonomers and long-chain branches that improve processability of otherwise linear polymers. 

Ling, Q. Sun, J. Zhao, Q. Zhou, Q. Microwave absorbing properties of linear low density polyethylene/ethylene-octene copolymer composites filled with short carbon fiber Mater. Sci. Eng., B 2009, 162, 162-166. 

Fig. 10.21 Plot of In G against AT for linear polyethylene and a set of ethylene-octene copolymers of comparable molecular weight and varying comonomer content. Linear polyethylene. Copolymers o M = 23 600, 0.42 mol% branches T Mw = 18 120,1.1 mol% branches V Af = 17 500, 2.2 mol% branches. (Data from Lambert and Phillips (8))...

In this study, two kinds of base material were used a prevailingly linear neat PP (PP DM55pharm) and a thermoplastic polyolefin elastomer (Engage 8407), supplied by Borealis and Dow Chemical, respectively. Specific material data can be found on the manufacturers homepages [6, 7]. Engage 8407 is an ethylene-octene copolymer (EOC) with a monomer-ratio of 60% to 40% for ethylene and octene, respectively. It contains untreated talc particles of 1 /an (ave.) in size. Engage 8407, when blended with PP or polyethylene, can improve the overall impact performance and can also act as a melt flow enhancer to aid processing. 

Instead of block copolymers, the use of pseudo-random linear copolymers of an aliphatic a-olefin and a vinyl aromatic monomer has been reported [20], where the styrene content of the polymer must be higher than 40 wt%. Preferred are styrene and ethylene copolymers. These blends may contain, amongst other things, an elastomeric olefinic impact modifier such as homopolymers and copolymers of a-olefins. Presumably the styrene-ethylene copolymer acts as a polymer emulsifier for the olefinic impact modifier. Using 5 wt% of an ethylene-styrene (30 70) copolymer and 20% of an ethylene-octene impact modifier in sPS, a tensile elongation (ASTM D638) of 25 % was obtained. 

For the production of ethylene/l-octene copolymers, metallocenes in combination with oligomeric methylalumoxanes or other compounds are now used [31, 63]. Half-sandwich transition metal complexes such as [(tetramethyl- / -cyclopentadienyl) (A-/-butylamido)dimethylsilyl]titanium dichloride are applied to synthesize linear low-density copolymers and plastomers, called constrained geometry catalysts [31]. Ethylene and styrene can be copolymerized to products ranging from semicrystalline mbber-like elastomers to highly amorphous rigid materials at room temperature [64]. 

HOPE, LDPE, and LLDPE are the three main types of commercial polyethylenes with a combined global consumption of >80 Mt/year. HDPE is a strictly linear homopolymer while LDPE is a long-branched homopolymer because of the different methods of polymerization. LLDPE, on the other hand, is a linear ethylene copolymer with small amounts of a-olefin comonomers such as butene, hexene, or octene. Traditionally, polyethylenes are classified according to the densities. The density of polyethylene decreases as the branching and/or comonomer content increases. The crystallinity and the properties associated with crystallinity, such as stiffness, strength, and chemical resistance, progressively decrease from HDPE to LDPE/LLDPE to POE grades. 

Further work has resulted in ADMET copolymer models of ethylene/l-hexene [141], and ethylene/l-octene [142]. Commercial ethylene/1-octene copolymers represent a significant portion of the linear low-density PE market however, the ADMET model polymers, with hexyl branches on every 9th, 15th, or 21st carbon, displayed much better thermal profiles than those seen with ethylene/l-octene copolymers produced by other methods. Additionally, the thermal properties of these hexyl-branched ADMET polymers were similar to those of their methyl-branched ADMET polymer analogs. This observation points to the possible... 

Table 10.14 Areas of the main iso-alkane peaks in the pyrograms of linear polyethylene, ethylene - butene-1, ethylene - hexene-1 and ethylene - octene-1 copolymers. ...

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