Unit cell dimensions in model ethylene‐butene‐1 copolymers

Howard, Paul R.; Crist, Buckley

doi:10.1002/polb.1989.090271109

Cited by 75 publications

(58 citation statements)

References 26 publications

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“…At low contents of poly(BPOCPA), the polar graft units of the coproducts were probably forcing the PE chains apart laterally and thus expanding the a and b unit cell dimensions. The similar structural changes were reported for oriented [25] and branched polyehthylene, depending on the type, distribution and content of the branches [26,27]. The frequent conclusion given for these expansions is that the branches are included into the crystalline regions, compelling the chains in laterally expanded unit cell dimensions.…”

Section: Characterization Of the Products By Dsc And Xrdsupporting

confidence: 65%

Reinforcement of high density polyethylene with a side chain LCP by graft copolymerization—thermal, mechanical and morphological properties

Soykan

Çetin

2015

J Polym Res

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In this study, high density polyethylene (PE) has been reinforced with a side chain LCP by graft copolymerization of p-benzophenoneoxycarbonylphenyl acrylate (BPOCPA). The mechanical and thermal behavior of the graft coproducts were investigated in relation to the structural changes (in unit cell parameters) of PE matrix. The crystalline melting temperature of PE, varying consistently with the poly(BPOCPA) content in the coproducts, significantly increased (from 131°C to 132-138°C). The unit cell dimensions, a and b, of the orthorhombic structure, the ab basal area and particle size of PE crystals initially expanded, and then consistently contracted with the graft content. The c parameter, however, remained relatively unchanged. Remarkable improvements were achieved in the tensile properties of the material; with the maxima of 38 % increase in tensile strength and 67 % increase in Young's modulus with the coproduct comprising 9.3 % poly(BPOCPA). These developments were found to be explained by the advances in the orientation and alignment of PE chains, conduced by greater chain mobility in the larger ab basal area and intensifying cohesive forces arising from the glassy nematic structured graft units.

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Section: Characterization Of the Products By Dsc And Xrdsupporting

confidence: 65%

Reinforcement of high density polyethylene with a side chain LCP by graft copolymerization—thermal, mechanical and morphological properties

Soykan

Çetin

2015

J Polym Res

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“…The dilation of the unit cell for such copolymers is well established. 51 For the hydrogenated poly(butadienes), random ethylene-butene copolymers, c varies from 1.00 g/cm 3 for the homopolymer to 0.976 g/cm 3 for a copolymer containing 7.3 mol % branch points. Higher values of (1Ϫ) d will be obtained when the c values of the dilated unit cell are used.…”

Section: Resultsmentioning

confidence: 99%

The degree of crystallinity of monoclinic isotactic poly(propylene)

Isasi

Mandelkern

Galante

et al. 1999

J. Polym. Sci. B Polym. Phys.

103

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The degree of crystallinity of a set of monoclinic (alpha) isotactic poly(propylenes), prepared by a metallocene‐type catalyst, were determined at room temperature. Three different methods were used: density, enthalpy of fusion, and wide‐angle X‐ray scattering, and the results compared. The relation between the heat of fusion and the specific volume of these poly(propylenes) was found to be nonlinear, thus precluding any linear extrapolation to obtain the heat of fusion of the pure crystal (ΔHu). The value of ΔHu obtained from depression of the melting temperature by diluents is used. Based on the unit cell density of monoclinic crystals formed from a low defected fraction, the density obtained crystallinity levels were found to be between 0.l5–0.25 higher than those calculated from the heat of fusion. This relatively large difference holds for the isothermally crystallized and quenched isotactic poly(propylenes), and reflects the contribution of the interphase to the density determined crystallinity, which does not contribute to the heat of fusion. Paralleling results found in other systems, the crystallinity levels obtained from wide‐angle X‐ray scattering agree with those obtained from density, indicating a significant contribution of the partially ordered phase to the total diffraction. Emphasis is given on the need to account for the large differences in the crystallinities of poly(propylene) measured by different techniques when evaluating the dependence of properties on this quantity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 323–334, 1999

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“…39 The intrinsic crystallinity of this PE is limited to about 40% by these branches. 27,40 Variation of the ordered mesophase structure of the block copolymers allowed us to establish how changes in the microdomain geometry and connectivity influence crystallization of the PE component. In addition, variation of chain architecture permitted us to examine the influence of free PE chain ends on crystallization, through comparison of singly tethered PE chains in EV diblocks to doubly tethered chains in VEV triblocks.…”

Section: Introductionmentioning

confidence: 99%