Polyethylene characterization

General Description TPOs are resin blends of polypropylene with rubber (EPDM or EP) and polyethylene. Characterized by high-impact strength, low density, and good chemical resistance, they are used when durability and reliability are primary con-... 

E.J. Bastarrachea, L.A. McEandsborough, M. Peleg, J.M. Goddard, Antimicrobial N-halamine modified polyethylene characterization, biocidal efficacy, regeneration, and stability. J. Food Sci. 79, 887-897 (2014)... 

Goldman M., M. Lee, R. Gronsky, and L. Pruitt. 1997. Oxidation of ultrahigh molecular weight polyethylene characterized by Fourier Transform Infrared Spectrometry. / Biomed Mater Res 37 43-50. 

This blend contains polyolefins as both components. Polyethylene used here is a low density polyethylene characterized by relatively high branching (density of crystalline phase is 1000 kg/m whereas amorphous phase is 860 kg/m ). Density of blend is in the middle of this range and similar to the density of low density polyethylene used for blend preparation. INVENTOR... 

Gel permeation chromatography (GPC) is another important tool in the polyethylene characterization process. Although the Melt Flow Ratio (MFR) value obtained with an experimental sample of polyethylene... 

Goldman M, Lee M, Gronsky R, Pruitt L.Oxidation of Ultrahigh Molecular Weight Polyethylene characterized by Fourier Transformation Infrared Spectrometry. J Biomed Mater Res. 1997 37(l) 43-50. 

Keller and Till, single crystals of polyethylene characterized... 

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

Polymerization processes are characterized by extremes. Industrial products are mixtures with molecular weights of lO" to 10. In a particular polymerization of styrene the viscosity increased by a fac tor of lO " as conversion went from 0 to 60 percent. The adiabatic reaction temperature for complete polymerization of ethylene is 1,800 K (3,240 R). Heat transfer coefficients in stirred tanks with high viscosities can be as low as 25 W/(m °C) (16.2 Btu/[h fH °F]). Reaction times for butadiene-styrene rubbers are 8 to 12 h polyethylene molecules continue to grow lor 30 min whereas ethyl acrylate in 20% emulsion reacts in less than 1 min, so monomer must be added gradually to keep the temperature within hmits. Initiators of the chain reactions have concentration of 10" g mol/L so they are highly sensitive to poisons and impurities. 

Polyethylene and polypropylene are semitransparent plastics made by polymerization. They are produced from ethylene and propylene in a variety of grades. Their mechanical properties are determined mainly by density (degree of crystallinity) and molecular weight, characterized by the Melt Index (MI). 

Transparent polyethylene is characterized by an enhanced freeze- and heat-aging resistance, and also by a... 

Dielectric relaxation measurements of polyethylene grafted with acrylic acid(AA), 2-hydroxyethyl methacrylate (HEMA) and their binary mixture were carried out in a trial to explore the molecular dynamics of the grafted samples [125]. Such measurements provide information about their molecular packing and interaction. It was possible to predict that the binary mixture used yields a random copolymer PE—g—P(AA/HEMA), which is greatly enriched with HEMA. This method of characterization is very interesting and is going to be developed in different polymer/monomer systems. 

The effect of thermal aging on polyethylene and isotactic polypropylene have been studied by Konar et al. [49]. They used contact angle, contact angle hysteresis, and XPS to characterize the modified surfaces of the polymers. Hysteresis increased with aging temperature. In the case of polyethylene, thermal aging led to a significant increase in adhesion strength of polyethylene with aluminium, but the increase in the case of polypropylene was much less marked. 

The type of interaction along the interface will exert a great influence on the various properties of the composite materials. Therefore, to improve the performance of a composite material, it is absolutely necessary to characterize the structures of the interface. Some of the methods for analysis of the interface are ESCA, AES, IR-FTIR, SIMS, and SEM, etc. At present, ESCA is widely used in the surface analysis of elements and the qualitative analysis of functional groups. Figure 11 shows the ESCA spectrum of polyethylene treated with... 

The most important olefins used for the production of petrochemicals are ethylene, propylene, the butylenes, and isoprene. These olefins are usually coproduced with ethylene by steam cracking ethane, LPG, liquid petroleum fractions, and residues. Olefins are characterized by their higher reactivities compared to paraffinic hydrocarbons. They can easily react with inexpensive reagents such as water, oxygen, hydrochloric acid, and chlorine to form valuable chemicals. Olefins can even add to themselves to produce important polymers such as polyethylene and polypropylene. Ethylene is the most important olefin for producing petrochemicals, and therefore, many sources have been sought for its production. The following discusses briefly, the properties of these olefmic intermediates. 

High-density polyethylene is characterized by a higher crystallinity and higher melting temperature than LDPE due to the absence of branching. 

In principle, it is possible to obtain ECC in the absence of molecular orientation if the crystallization is carried out very slowly at high temperatures close to the melting temperature. Thus, Mandelkern obtained polyethylene crystals similar to ECC in their thermodynamic characteristics by a 40 days crystallization of an isotropic melt28. These experiments also characterize one of the possible paths of the generation of order in polymers order through fluctuations 29 (see below). 

Figure 14 shows the displacement of the distribution function towards high / , i.e. the uncoiling of molecules under the influence of stretching for polyethylene (A = 3 x 10-9 m, N = 100 and T = 420 K). This displacement will be characterized by the position of the maximum of the distribution curve, the most probable value of / , i.e. j3m, as a function of x (Fig. 15). Figure 15 also shows the values of stresses a that should be applied to the melt to attain the corresponding values of x (o = xkT/SL, where S is the transverse cross-section of the molecule). 

In this review the definition of orientation and orientation functions or orientation averages will be considered in detail. This will be followed by a comprehensive account of the information which can be obtained by three spectroscopic techniques, infra-red and Raman spectroscopy and broad line nuclear magnetic resonance. The use of polarized fluorescence will not be discussed here, but is the subject of a contemporary review article by the author and J. H. Nobbs 1. The present review will be completed by consideration of the information which has been obtained on the development of molecular orientation in polyethylene terephthalate and poly(tetramethylene terephthalate) where there are also clearly defined changes in the conformation of the molecule. In this paper, particular attention will be given to the characterization of biaxially oriented films. Previous reviews of this subject have been given by the author and his colleagues, but have been concerned with discussion of results for uniaxially oriented systems only2,3). 

The present review is devoted to recent advances, mainly concerning the characterization of semicrystalline polymers, specifically polyethylene (PE) by means of microindentation hardness. The author has chosen to organize the chapter as follows ... 

Since the reactivity ratios of ethylene-polar monomer pairs are quite different, the preparation of copolymers with precisely the same comonomer composition can be a challenging endeavor. Earlier in this chapter, we described the synthesis and characterization of precisely placed methyl groups on a polyethylene... 

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