Crystallisation behaviour of high density polyethylene blends with bimodal molar mass distribution 1. Basic characteristics and isothermal crystallisation

Krumme, Andres; Lehtinen, Ari; Viikna, Anti

doi:10.1016/j.eurpolymj.2003.10.005

Cited by 45 publications

(45 citation statements)

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“…The calculated results are collected in Table I. It was reported that the additivity rule was valid for M w of PE blends, and the calculated and measured M w values fit quite well with each other according to Krumme et al 40 The Cross model was used to fit g* to obtain g 0 , and as shown in Figure 2, this model gave a reasonably good fit to our experimental data:…”

Section: Rheological Propertiessupporting

confidence: 54%

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Rheological behavior and mechanical properties of high‐density polyethylene blends with different molecular weights

Bai

Yang

2010

J of Applied Polymer Sci

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ABSTRACT:The dynamic rheological and mechanical properties of the binary blends of two conventional highdensity polyethylenes [HDPEs; low molecular weight (LMW) and high molecular weight (HMW)] with distinct different weight-average molecular weights were studied. The rheological results show that the rheological behavior of the blends departed from classical linear viscoelastic theory because of the polydispersity of the HDPEs that we used. Plots of the logarithm of the zero shear viscosity fitted by the Cross model versus the blend composition, Cole-Cole plots, Han curves, and master curves of the storage and loss moduli indicated the LMW/HMW blends of different compositions were miscible in the melt state. The tensile yield strength of the blends generally followed the linear additivity rule, whereas the elongation at break and impact strength were lower than those predicted by linear additivity; this suggested the incompatibility of the blends in solid state.

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Section: Rheological Propertiessupporting

confidence: 54%

“…Experiments were carried out under dry nitrogen. The samples were heated to 160 C rapidly, held at 160 C for 5 min, and then cooled to 40 C at a rate of 10 C/min. They were then heated from 40 to 160…”

Section: Dscmentioning

confidence: 99%

Rheological behavior and mechanical properties of high‐density polyethylene blends with different molecular weights

Bai

Yang

2010

J of Applied Polymer Sci

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“…Avrami equation is taking into consideration a constant nucleation rate and constant linear growth in 1-3 dimensions (Lorenzo et al, 2007). The Avrami equation was developed to describe isothermal conditions of crystallization processes (Supaphol, 2001;Krumme et al, 2004) but as it turns out it can be also applied to the description of non-isothermal processes and analytical data (Di Lorenzo & Silvestre, 1999;Martin, 2010). According to Málek (1995), the description of non-isothermal processes is possible only in a limited number of special cases.…”

Section: Crystallization Processmentioning

confidence: 99%

“…So far, crystallization kinetics has been widely studied in research on polymers (Lu et al, 1998;Martins & Cruz Pinto, 2002;Krumme et al, 2004), alloys (Vázquez et al, 2000;Liu et al, 2002), kaolinite (Fiore et al, 2011), oil-in-water emulsion (Khalil et al, 2012) or even milk fat fraction and chocolate (Herrera et al, 1999;Fernandes et al, 2013). The general Avrami equation was applied in the process of crystals formation of any shape and uses substitute spherical diameters.…”

Section: Crystallization Processmentioning

confidence: 99%

Using Avrami equation in the studies on changes in granulometric composition of algal suspension

Kuśnierz

Łomotowski

2015

Hydrobiologia

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In recent years, it has been recognized that the laser diffraction gives valuable information on particle size distribution for all types of dry inorganic or even organic materials. With use of the laser diffraction and the laser granulometer, this paper presents the changes occurring in the granulometric distribution of algal agglomerates and the changes in values of percentiles 10, 50 and 90%, determined basing on volume distribution. While assessing the granulometric composition, the existence of a proportional relationship between the diameter values corresponding to the percentile of 10, 50 and 90% was observed. What is more, the obtained results give insight into the possibility of application of the general Avrami equation to describe the granulometric composition of the algal suspension through the analogy of crystals formation from saturated solutions. The analysis shows that the model described by the modified Avrami equation adequately matched the regression to the experimental data on the granulometric composition of algal suspensions. The values of the correlation coefficients were close to 1, which proves that the regression model explained nearly all cases by the dependent variable V i = F(d i ).

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“…Many investigators have pointed out that the amount and distribution of SCB are significant factors in determining the physical properties of bimodal HDPE resins. [3][4][5][6][7][8][9] Hubert and coworkers 3 considered that more complicated molecular architectures make crystallization of regular chain folding difficult, and that inter-and intra-molecular heterogeneity of the comonomer distribution are efficient means of generating tie molecules and random chain folding at the expense of regular chain folding. As a result, bimodal HDPE resins have a higher degree of comonomer incorporation for a given crystallinity compared with unimodal HDPE resins.…”

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confidence: 99%

Characterization of the Microstructure of Bimodal HDPE Resin

et al. 2009

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In this work, two industrial bimodal high density polyethylene resins, resin A and resin B, having similar molecular weight (M w ), molecular weight distribution (M wD ), and short-chain branching (SCB) content but different mechanical properties, were fractionated through cross-fractionation. The fractions were further characterized by GPC, 13 C NMR, DSC and FT-IR techniques. These two resins were firstly fractionated into two fractions, i.e., high-temperature and low-temperature fractions, via preparative solution crystallization fractionation. Resin A with much better mechanical properties contains more hightemperature fractions with longer crystallizable sequences. The SCB content in the low-temperature fraction of resin A is lower than that of resin B. Both low-temperature fractions were then further fractionated using solvent gradient fractionation (SGF). The characterization of SGF fractions indicates that most of the branches fall into the high molecular weight chains in both low-temperature fractions. However, the high molecular weight chains in the low-temperature fraction of resin A contain less SCB than that of resin B.KEY WORDS: Polyethylene (PE) / Fractionation of Polymers / Microstructure / Bimodal high density polyethylene (HDPE) resins benefit from their bimodality by having the strength and stiffness of HDPE, whilst retaining the high-stress-crack resistance and processability of a unimodal medium density polyethylene. 1Such bimodal HDPE resins are ideally suited to the application demands of pipes for gas and water distribution.Bimodal HDPE resins are produced by tandem processes that use reactor combinations of loop, slurry, and gas-phase by themselves or in combination with one another. In the first reactor, high amounts of hydrogen are fed with ethylene. This process leads to the formation of low-molar-mass polyethylene. The second reactor is loaded with much less hydrogen to form a high-or very high-molar-mass polyethylene.2 This process allows for further essential product modification, specifically the incorporation of comonomer in the long polymer chains within the second reactor. There is also a reversed mode wherein the high-molar-mass component is produced firstly, followed by a low-molar-mass component. These products build up a polymer alloy in solid state with crystalline and amorphous regions in between. The crystalline regions are mainly formed by low-molar-mass homo-polyethylene. The high-molar-mass copolymers form the amorphous regions and act as tie molecules that connect the crystal lamellae ( Figure 29 in ref 2). These tie molecules that possess short-chain branching (SCB) effectively hinder the pullout of the polymer chains from the crystallites. In this manner, the strength and resistance to slow crack growth of the resin are greatly improved finally.Recently, there has been an emphasis in developing relations between microstructure and end-use physical/mechanical properties of bimodal HDPE resins. Many investigators have pointed out that the amount and distribution of S...

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Crystallisation behaviour of high density polyethylene blends with bimodal molar mass distribution 1. Basic characteristics and isothermal crystallisation

Cited by 45 publications

References 46 publications

Rheological behavior and mechanical properties of high‐density polyethylene blends with different molecular weights

Rheological behavior and mechanical properties of high‐density polyethylene blends with different molecular weights

Using Avrami equation in the studies on changes in granulometric composition of algal suspension

Characterization of the Microstructure of Bimodal HDPE Resin

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