High-density polyethylene viscosity

The homopolymer finds a variety of uses, as an adhesive component, as a base for chewing gum, in caulking compounds, as a tackifier for greases, in tank linings, as a motor oil additive to provide suitable viscosity characteristics and to improve the environmental stress-cracking resistance of polyethylene. It has been incorporated in quantities of up to 30% in high-density polyethylene to improve the impact strength of heavy duty sacks. 

FIGURE 11.22 Variation of melt viscosity with shear rate for GR high-density polyethylene (HDPE). (From Yanez-Flores, G., Ramos De-Valle, F.F., and Rodriguez-Femandez, O.S., Proceedings of the Society of Plastics Engineers Annual Technical Conference, 1997, p. 381.)... 

HDPE= high density polyethylene PPLv= polypropylene with low viscosity PPhv= polypropylene... 

Most high density polyethylene processing technologies require the melting of HDPE. Typical HDPE melt viscosities are between 1,000 and 100,000 Pa s( 10,000 10 P) the melt viscosity of HDPE strongly... 

For example, Figs. 2.43 and 2.44 present the measured [55] viscosity and first normal stress difference data, respectively, for three blow molding grade high density polyethylenes along with a fit obtained from the Papanastasiou-Scriven-Macosko [59] form of the K-BKZ equation. A memory function with a relaxation spectrum of 8 relaxation times was used. 

For polymer melts where the low shear rate limiting viscosity value is r ), r 3t]0 (14). Examples of extensional viscosity growth, either to a steady t](i ) value or to a strainhardening-like mode, are shown in Fig. 3.6 for the linear nonbranched polystyrene (PS), a high density polyethylene (HDPE) that is only slightly branched with short branches, and a long chain-branched low density polyethylene (LDPE) (15). 

Example 9.2 The Design of a HDPE Pelletizing Extruder Design an 18,000-lb/hr pelletizing extruder for high-density polyethylene (HDPE) melt at 450°F to generate 2500 psi head pressure. Assume a constant channel depth extruder with an axial length of 60 in. The melt density is 54 lb/ft3, the viscosity is 0.15 lbfs/in2, and the specific heat is 0.717 Btu/lb°F. 

Abbreviations y x AFM AIBN BuMA Ca DCP DMA DMS DSC EGDMA EMA EPDM FT-IR HDPE HTV IPN LDPE LLDPE MA MAA MDI MMA PA PAC PB PBT PBuMA PDMS PDMS-NH2 interfacial tension viscosity ratio atomic force microscopy 2,2 -azobis(isobutyronitrile) butyl methacrylate capillary number dicumyl peroxide dynamic mechanical analysis dynamic mechanical spectroscopy differential scanning calorimetry ethylene glycol dimethacrylate ethyl methacrylate ethylene-propylene-diene rubber Fourier transform-infra-red high density polyethylene high temperature vulcanization interpenetrating polymer network low density polyethylene linear low density polyethylene maleic anhydride methacrylic acid 4,4 -diphenylmethanediisocyanate methyl methacrylate poly( amide) poly( acrylate) poly(butadiene) poly(butylene terephtalate) poly(butyl methacrylate) poly(dimethylsiloxane) amino-terminated poly(dimethylsiloxane)... 

Accordingly, die swell increases with increasing flow rate and decreases with increasing length of the capillary. Both effects are depicted in Fig. 15.33 for high-density polyethylene (Han et al., 1970). This is also in agreement with Fig. 15.34, where die swell and viscosity of polystyrene are plotted vs. shear rate (Greassley et al., 1970). Die swell decreases with... 

Another effect of the variation of the extensional viscosity is the maximum extend-ibility. For polymers like high-density polyethylene, the rapid increase of the extensional viscosity during the spinning process limits the obtainable spin-draw ratio that is the ratio between the winding velocity and the velocity in the orifice. Examples can be found in an article of Han and Lamonte (1972). 

Figure 3.39 Uniaxial extensional viscosity rj as a function of time following start-up of steady uniaxial extension at the extension rates e indicated. Data are shown for an unbranched polystyrene (PS I), a high-density polyethylene with short, unentangled side branches (HOPE I), and two low-density polyethylenes (LDPE III and lUPAC A), with long side branches. (From Laun 1984, with permission from the Universidad Nacional Autonoma de Mexico.)------------------------------...

Fig.l Molecular-weight-distribution (MWD) and viscosity-law plots for NIST PE1475 high-density polyethylene (dashed lines) and NIST PE1476 low-density polyethylene (solid lines). The curves are (1) MWD, (2) observed viscosity, (3) fitted viscosity for linear polyethylene, (4) extrapolated fitted viscosity for polyethylene with short-chain branches only, and (5) fitted viscosity for branched polyethylene. 

Figure 3.66 shows the steady-shear viscosity for a polymer system at three molar masses. Note the plateau in viscosity at low shear rates (or the zero-shear viscosity). Also note how the zero-shear viscosity scales with to the power 3.4. (This is predicted by Rouse theory (Rouse, 1953).) Figure 3.67 shows the viscosity and first normal-stress difference for a high-density polyethylene at 200 C. Note the decrease in steady-shear viscosity with increasing shear rate. This is termed shear-thinning behaviour and is typical of polymer-melt flow, in which it is believed to be due to the polymer chain orientation and non-affine motion of polymer chains. Note also that the normal-stress difference increases with shear rate. This is also common for polymer melts, and is related to an increase in elasticity as the polymer chain motion becomes more restricted normal to flow at higher shearing rates. 

High Density Polyethylene (HDPE). The preferred method of evaluating HDPE was found to be the time to cross link at 220 0 using the Brabender apparatus, as is made evident by the rapid increase in torque. Determining melt viscosity by multiple extrusion showed only small differences compared to the base polymer. 

Eor the typical commercial polypropylene copolymer systems the viscosity of the matrix phase is quite high, and the molecular diffusion and solubility of the minor phase component in the matrix phase are relatively high. These factors tend to favor the evaporation/condensation, that is, Ostwald ripening, mechanism and suppress the coalescence mechanism in these systems. Mirabella and coworkers studied a series of multiphase systems, including a hiPP (30), a high density polyethylene (HOPE)/ hydrogenated polybutadiene (HPB) blend, (31) and an unbranched PE molecular... 

In order to improve properties and compatibility of PP/EPDM blends, ternary blends and composites are sometimes prepared from the PP/EPDM blends. For instance, Sanchez et al. (10) prepared ternary blends of PP, high density polyethylene and EPDM with several blending ratios and investigated the melt rheological behaviors. They discussed the effect of the shear rate on the viscosity and flow curve in terms of the exponent of low power for a non-Newtonian liquid. They showed that addition of an elastomer to the polyolefin blends changes the shape of the viscosity-composition curve, and they discussed it in terms of the possible morphology of the blend. Similar works have been also reported by Ha et al. (11,12). 

The indicated above importance of polymer melts viscosity causes the appearance of a considerable number of theoretical treatments, describing this property on the basis of either representations, mainly fiom the point of view of free volume [3], In the present chapter polymer melts viscosity is treated within the framework of fractal analysis [5]. This is due to the fact, that the macromolecular coil in polymer solutions and melts is a fiactal [6] that creates prerequisites for the polymer melt viscosity prediction quite at the synthesis stage. The authors of Ref [7] demonstrated the possibility of polymer melts viscosity description and prediction within the fiamework of fiactal analysis on the example of two polymers of different classes—aromatic poly-ethersulfonoformals (APESF) and high-density polyethylene (HOPE). MFI values were determined on the automatic capillary viscometer IIRT-A at temperatures and loads, listed in Table 1. The fiactal dimension of a macromo-... 

Malamatov, A. Kh. Kozlov, G. V Burya, A. I. Kudina, E. R Mikitaev, A. K. The melt viscosity of nanocomposites on the basis of high density polyethylene. Bulletin... 

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