Correlations Between Polyethylene Properties

The way in which some PE properties vary with density, MFR, and MWD is presented in Table 3.24. 

Viscosity, rate of change with shear rate + 

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Another motivation for measurement of the microhardness of materials is the correlation of microhardness with other mechanical properties. For example, the microhardness value for a pyramid indenter producing plastic flow is approximately three times the yield stress, i.e. // 3T (Tabor, 1951). This is the basic relation between indentation microhardness and bulk properties. It is, however, only applicable to an ideally plastic solid showing no elastic strains. The correlation between H and Y is given in Fig. 1.1 for linear polyethylene (PE) and poly(ethylene terephthalate) (PET) samples with different morphologies. The lower hardness values of 30-45 MPa obtained for melt-crystallized PE materials fall below the /// T cu 3 value, which may be related to a lower stiff-compliant ratio for these lamellar structures (BaM Calleja, 1985b). PE annealed at ca 130 °C... 

Generally, there is a certain correlation between density, on the one hand, and flexural strength and modulus, on the other, for many other materials, and that correlation is not related to porosity. For example, there is a strong correlation (R = 0.984) between density of all 38 polyethylene materials, listed in Table 7.49 of Chapter 7, including LDPE, LLDPE, HDPE, and their flexural modulus (Figure 6.1). Besides, mineral fillers in WPC materials increase density of the final product and also increase its flexural modulus. However, this chapter is mainly concerned about relationships between density and properties of WPC having the same formulation but produced at different regimes. 

With a Raman instrument, measurement of these low lying bands is fairly straightforward. If the elastic Rayleigh scattering can be removed (for example the use of iodine gas filters (56) to selectively absorb the Rayleigh line), very low frequency vibrations in the range of a few cm can be observed. Based on the imit cell parameters of polyethylene, a set of Raman active lattice vibrations has been observed for polyethylene and paraffins (57). Rotatory modes are seen in traras-l,4-polybutadiene (49). With analysis of these low lying vibrations in a quantitative fashion, a correlation between molecular and macroscopic properties such as heat capacity, thermal pressure, thermal expansion, P-V-T relations, and stress-strain behavior can all be established (58). 

In this section, the correlation between IR/Raman frequencies of functional groups relevant to polymer analysis and polymer microstructures is described. The functional groups considered are the C=C double bond and substituted benzenes. The microstructure featuring the C=C double bond is important because the physical properties of materials such as polybutadiene and related polymers depend on the double-bond content of the overall structure. Also, a small percentage of residual C=C double bonds are formed in polyethylene chains as a result of side reactions. Substituted benzene compounds are used as starting materials such as bis-phenol A, phthalates, and benzoates. 

The effect of annealing on the properties of ultra-high modulus linear polyethylene has been studied. There was a good correlation between the modulus and lamellae thickness irrespective of annealing temperature. On drawing, annealing, and rapid quenching to room temperature there is an immediate fall in... 

Kriston I, Orban-Mester A, Nagy G, Staniek PR, Foeldes E, Pukanszky B. Melt stabilisation of Phillips type polyethylene. Part II correlation between additive consumption and polymer properties. Polym Degrad Stab 2009 94(9) 1448-56. 

Han, C.D., Kim, Y.W. Studies on melt spinning. 5. Elongational viscosity and spinnability of two-phase systems , J. Appl. Polym. Sci. 18(9) (1974), 2589-2603 Munstedt, H., Steffi, T., Malmberg, A. Correlation between rheological behaviour in uniaxial elongation and film blowing properties of various polyethylenes , Rheol. Acta 45(1) (2005), 14-22... 

The orientation and properties of polyethylene films produeed by the blown-film technique have been studied by many researehes in literature [2-6]. The correlation between orientation and morphology of oriented polyethylene (mostly blown film) has been studied thoroughly as well [7-10]. Mechanieal and viseoelastic properties of biaxially oriented films produeed by double bubble method were also investigated [11-13]. 

In order to investigate the correlation between tensile drawing data and Reversed Charpy results, true stress vs. true strain properties of PE are measured at several strain rates and temperatures [6]. Each stress-strain curve is represented using a Haward-Thackray [7] spring-dashpot model, whose applicability to polyethylene has been established empirically by a number of previous studies [5, 7] although the physical basis for the model remains... 

The objective of this work is to evaluate the fracture behavior of a series of commercial Medium Density Polyethylenes by the EWF technique and find correlations between the fracture parameters and the polymer properties (comonomer content, crystallinity, molecular weight and their distribution) for neat and annealed samples. 

Abstract The fracture properties and microdeformation behaviour and their correlation with structure in commercial bulk polyolefins are reviewed. Emphasis is on crack-tip deformation mechanisms and on regimes of direct practical interest, namely slow crack growth in polyethylene and high-speed ductile-brittle transitions in isotactic polypropylene. Recent fracture studies of reaction-bonded interfaces are also briefly considered, these representing promising model systems for the investigation of the relationship between the fundamental mechanisms of crack-tip deformation and fracture and molecular structure. 

Yoon, Smith, and Matsuda, on the other hand, compared two approaches, using a united-atom model and a fully atomistic model.Stochastic dynamics and MD simulations of w-tridecane (C13H28) were used to study polyethylene. Besides studying the bulk melt, the authors examined confined melts between solid surfaces. Chain conformations, chain packing orientational correlations, and self-diffusion were among the properties studied. In regard to chain confer-... 

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