Blends of polyolefins: Characteristic melting and crystallization data

Haghighat, Siavash; Birley, A. W.

doi:10.1002/adv.1990.060100207

Cited by 12 publications

(6 citation statements)

References 2 publications

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“…1995 American Chemical Society " For HDPE-D the Mw was calculated as if it contained H-atoms rather than D-atoms. 6 For LDPE, Mws were obtained using a SEC-intrinsic viscosity procedure as described previously.1 * Branches containing > 8 carbon atoms (via 13C NMR). d Branches containing < 8 carbon atoms (via 13C NMR).…”

Section: Introductionmentioning

confidence: 99%

Morphology of Blends of Linear and Long-Chain-Branched Polyethylenes in the Solid State: A Study by SANS, SAXS, and DSC

Wígnall¹,

Londono²,

Lin³

et al. 1995

Macromolecules

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Differential scanning calorimetry (DSC), small-angle neutron scattering (SANS), and X-ray scattering (SAXS) have been used to investigate the solid-state morphology of blends of linear (high density) and long-chain-branched (low-density) polyethylenes (HDPE/LDPE). The blends are homogeneous in the melt, as previously demonstrated by SANS using the contrast obtained by deuterating the linear polymer. However, due to the structural and melting point differences (~20 °C) between HDPE and LDPE, the components may phase segregate on slow cooling (0.75 °C/min). For high concentrations (

0.5) of HDPE, relatively high rates of crystallization of the linear component lead to the formation of separate stacks of HDPE and LDPE lamellae, as indicated by two-peak SAXS curves. For predominantly branched blends, the difference in crystallization rate of the components becomes smaller and only one SAXS peak is observed, indicating that the two species are in the same lamellar stack. Moreover, the phases no longer consist of the pure components and the HDPE lamellae contain up to 15-20% LDPE (and vice versa). Rapid quenching into dry ice/2-propanol (-78 °C) produces only one SAXS peak (and hence one lamellar stack) over the whole concentration range. The blends show extensive cocrystallization, along with a tendency for the branched material to be preferentially located in the amorphous interlamellar regions. For high concentrations ( > 0.5) of HDPE-D, the overall scattering length density (SLD) is high and the excess concentration of LDPE between the lamellae enhances the SLD contrast between the crystalline and amorphous phases. Thus, the interlamellar spacing (long period) is clearly visible in the SANS pattern. The blend morphology is a strong function of the quenching rate, and samples quenched less rapidly (e.g., into water at 23 °C) are similar to slowly cor'ed blends. The combination of SANS, SAXS, and DSC techniques allows us to interpret morphological differences in the solid state of these blends.

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Section: Introductionmentioning

confidence: 99%

Morphology of Blends of Linear and Long-Chain-Branched Polyethylenes in the Solid State: A Study by SANS, SAXS, and DSC

Wígnall¹,

Londono²,

Lin³

et al. 1995

Macromolecules

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“…From this plot, it is evident that the yield strength decreases with increasing levels of mLLDPE, whereas the yield strength of the film blends of LLDPE with LDPE increases with the addition of LLDPE [17]. The latter observation may be due to the heterogeneous short-chain branching distribution of LLDPE [4] and has also been shown to be the case for other conventional LLDPE/LDPE film blends [33,34].…”

Section: Slow-rate Small Deformation Mechanical Propertiesmentioning

confidence: 89%

The Effect of Downgauging on the Physicomechanical Properties of Film Blends of Linear Low-density Polyethylene with Low-density Polyethylene

Cran

Bigger

2005

Journal of Elastomers & Plastics

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Two series of film formulations are investigated comprising blends of a metallocene-catalyzed linear low-density polyethylene (mLLDPE) or a conventional linear low-density polyethylene (LLDPE) with a low-density polyethylene (LDPE). The physicomechanical and optical properties are studied at various gauge lengths to investigate the effects of downgauging the films, particularly those containing mLLDPE. The potential for downgauging is found to be optimum at higher levels of mLLDPE with the best results achieved for a film containing 40 wt.% mLLDPE at 60 mm. This formulation has significantly better properties than an analogous blend containing 40 wt.% LLDPE at 100 mm. The potential materials and cost savings associated with downgauging films is also briefly investigated.

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“…In the HDPE-LDPE mixture, phase separation often occurs in the crystalline phase [1,11,[17][18][19][20][21][22][23][24], since crystals of different sizes melt at different temperatures and those with different structures and materials create different crystal modifications. That is why the slower the blend is crystallized by cooling, the more the differences between the crystal structures appear, and the more it segregates [24,25].…”

Section: Introductionmentioning

confidence: 99%

Crystallinity and Oscillatory Shear Rheology of Polyethylene Blends

Nagy,

Weltsch

2023

Materials

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Crystallinity and rheological behavior are significant for processing semi-crystalline polymers with fine mechanical properties. There is always an economical need to create a less expensive new material with better properties. Non-isothermal crystallization and oscillatory shear rheology of different branch-type polyethylene–polyethylene blends were investigated. Samples of high-density and low-density polyethylene (HDPE/LDPE) (20/80, 40/60, 60/40 and 80/20 weight ratios) and two types of high-density and linear low-density polyethylene (HDPE/LLDPE) (40/60 and 60/40 weight ratios) were prepared via extrusion. The materials were tested by differential scanning calorimetry (DSC) at several cooling rates (5, 10, 20, 30 and 40°/min) and by oscillation rheometry (ARES G2) at low angular frequency range to prove their miscibility or immiscibility. It was found that the one-peak melting endotherm of the 80–20% HDPE-LDPE blend could indicate miscibility in the solid phase, while the other HDPE-LDPE blends with two-peak curves are partially or not miscible. In contrast, all the HDPE-LLDPE blends indicate co-crystallization, but the 40–60% HDPE-LLDPE butylene blend is probably immiscible. It was revealed that complex viscosity decreases with angular frequency: linearly for HD-LD blends and not linearly for HD-LLDPE blends. The complex viscosity shows linear behavior with composition for HD-LLDPE blends, while there is a positive–negative deviation for HD-LD blends. In the liquid phase, according to rheological measurements, the HDPE-LDPE blends are not or partially miscible, while the HDPE-LLDPE blends are probably miscible.

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Blends of polyolefins: Characteristic melting and crystallization data

Cited by 12 publications

References 2 publications

Morphology of Blends of Linear and Long-Chain-Branched Polyethylenes in the Solid State: A Study by SANS, SAXS, and DSC

Morphology of Blends of Linear and Long-Chain-Branched Polyethylenes in the Solid State: A Study by SANS, SAXS, and DSC

The Effect of Downgauging on the Physicomechanical Properties of Film Blends of Linear Low-density Polyethylene with Low-density Polyethylene

Crystallinity and Oscillatory Shear Rheology of Polyethylene Blends

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