Ethylene-octene copolymer curves

Figure 5.12 represents a compilation of melting temperature relations for rapidly crystallized ethylene copolymers with a set of 1-alkenes and norbomene as comonomers.(74-76,78) The melting temperatures of ethylene copolymers with bulkier side-group comonomers such as 1-decene, 4-methyl-1-pentene, cyclopen-tadiene and dicyclopentadiene follow the same curve as in Fig. 5.12.(78a) The plot clearly indicates that the melting points are independent of co-unit type under these crystallization conditions. Since observed melting temperatures of copolymers are known to depend on chain length the results shown have been limited to molecular weights of about 90000.(21) Studies of ethylene-octene copolymers with much higher comonomer content indicate a continuation of the curve shown in Fig. 5.12...

FIG. 7 Stress-strain curves in yield region for specific copolymers (a) ethylene-octene copolymers (b) ethylene-hexene copolymers (c) ethylene-butene copol5mers (d) schematic representation. Core level of crystallinity indicated with each curve. (From Ref. 9.)... 

FIG. 17 Stress-strain curves in yield region as a function of indicated draw rates at 25°C. Several of the curves slightly displaced for purposes of clarity, (a) ethylene-octene copolymer = 79,000, = 2.0, = 0.4 (b) ethylene-butene copolymer = 108,000, M /M = 2.1,... 

Plane strain compression hi a channel die is kinematically very similar to drawing the sample is extended and its cross-section decreases accorduigly. However, the possibility of void formation is limited due to the compressive component of stress. It means that the differences in true stress-true strain dependencies of drawn and plane strained polymers should be attributed to the formation and development of cavities. Slopes of the elastic region of true stress-true strain curves are similar in tension and in plane strain compression. The difference in mechanical properties of polymers sets in at yielding in tension. The scale of difference depends on the particular polymer the yield in drawing for POM, PA 6, PP and HDPE takes place at a much lower stress than in plane strain compression. For polymers with low crystal plastic resistance, such as LDPEs and ethylene-octene copolymer (EOC), the stresses at selected deformation... 

Fig. 22. Comparison of Crystaf profiles and Stockmayer s distributions for a series of ethylene/l-octene copolymers. Experimental Crystaf curves are indicated with syrmbols and the solid curves are the respective Stockmayer s distributions. Sample A sample D A sample H. Molecular weights of samples A = 29 600 D = 38 000 H Mn =...

Figure 18.4 Effect of shear rate on melt viscosity at 275° C of PA6, PE, and PA6/PE blend compatibi-lized by PE-g-MAH containing 0.27 wt% of grafted MAH. Ciphers on curves stand for compatibilizer concentration in wt%, PE stands for LDPE/LHDPE (88 12) blend LHDPE is copolymer of ethylene and octene. Reproduced from Reference (66) with permission from John Wiley Sons. Inc.

One of the main difficulties for the quantification of Crystaf is the nonimiver-sality of its calibration curves. Even for a series of ethylene/a-olefin copolymers, the calibration curves will vary as a function of comonomer type, as illustrated in Figure 15. The general rule of thumb for these copolymers (from propene to 1-octene) is, the longer the a-olefin, the lower the crystallization temperature for a given a-olefin molar fraction. This has been explained by several authors on the basis of the difference in the degree of inclusion of the a-olefin in the crystalline lattice shorter a-olefins are more likely to cocrystallize with ethylene and therefore depress the crystallization temperature to a lesser extent. 

Fig. 15. Crystaf calibration curves for ethylene/l-butene (EB-01) and ethylene/l-octene (EO-01) copolymers. EB-01 o EO-01. From Ref 17. Copyright (2000) Wiley-VCH.

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