Processability of LLDPE/LDPE blends: capillary extrusion studies.INTRODUCTION
The processability of linear low-density polyethylenes low-density polyethylene
n. Abbr. LDPE
A form of polyethylene having many side branches off the main carbon backbone and a less closely packed structure than that of high-density polyethylene. (LLDPEs) can be improved by blending with a small amount of a low-density polyethylene [1-3]. However, because of structural differences between resins, many undesirable effects may occur such as immiscibility im·mis·ci·ble
That cannot undergo mixing or blending: immiscible elements.
im·mis of the components and undesirable morphological mor·phol·o·gy
n. pl. mor·phol·o·gies
a. The branch of biology that deals with the form and structure of organisms without consideration of function.
b. changes [4, 5] as well as premature onset of flow instabilities [1, 6]. These effects obviously influence the economic feasibility of the processes as well as the mechanical properties of the final products [1, 7-9].
In our previous work, Delgadillo-Velazquez et al.  have studied the miscibility miscibility (miˈ·s·biˑ·l between a linear polyethylene polyethylene (pŏl'ēĕth`əlēn), widely used plastic. It is a polymer of ethylene, CH2=CH2, having the formula (-CH2-CH2-)n (Ziegler-Natta hexane hexane /hex·ane/ (hek´san) a saturated hydrogen obtained by distillation from petroleum.
n. copolymer copolymer: see polymer. of LLDPE LLDPE Linear Low Density Polyethylene ) and four branched polyethylenes (LDPEs) using differential scanning calorimetry Differential scanning calorimetry or DSC is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference are measured as a function of temperature. (DSC (1) (Digital Signal Controller) A microcontroller and DSP combined on the same chip. It adds the interrupt-driven capabilities normally associated with a microcontroller to a DSP, which typically functions as a continuous process. See microcontroller and DSP. ) and several rheological rhe·ol·o·gy
The study of the deformation and flow of matter.
rheo·log methods (the exact same blends are used in the present work). It was found that these blends are immiscible immiscible /im·mis·ci·ble/ (i-mis´i-b'l) not susceptible to being mixed.
Incapable of being mixed or blended, as oil and water. at high low density polyethylene Low-density polyethylene (LDPE) is a thermoplastic made from oil. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerisation . (LDPE LDPE
low-density polyethylene ) concentrations (typically grater than 20 wt%) and miscible miscible /mis·ci·ble/ (mis´i-b'l) able to be mixed.
Capable of being and remaining mixed in all proportions. Used of liquids. at smaller LDPE weight concentrations. The effects of long chain branching (LCB LCB Liquor Control Board
LCB Legislative Counsel Bureau (Nevada)
LCB Le Cordon Bleu (College of Culinary Arts)
LCB Linnaeus Centre for Bioinformatics (Sweden) ) on the rheology were assessed by means of parallel-plate and extensional rheometry. It was found that shear shear: see strength of materials.
A straining action wherein applied forces produce a sliding or skewing type of deformation. is insensitive in·sen·si·tive
1. Not physically sensitive; numb.
a. Lacking in sensitivity to the feelings or circumstances of others; unfeeling.
b. to additions of small amounts of LDPE into LLDPE (up to 20 wt% in many cases) particularly if the viscosity curve of LDPE is about the same or lower than that of the corresponding LLDPE. On the other hand, extensional rheometry was found sensitive to addition of only 1 wt% of LDPE into LLDPE only at high Hencky strain rates (typically greater than 5 [s.sup.-1]) and for the blends that contained the LDPE with the highest molecular weight. Such rates are not easily accessible by commercial extensional rheometers. The SER Ser serine.
smooth endoplasmic reticulum.
serine. Universal Testing Platform from Xpansion Instruments is the only known extensional rheometer rhe·om·e·ter
An instrument for measuring the flow of viscous liquids, such as blood. that can perform reliable experiments at such high Hencky strain rates [11, 12].
In this work, we study systematically the processing behavior of a LLDPE with four LDPEs that have viscosity curves which lie above, about the same and below that of the LLDPE. As discussed earlier, the same blends used by Delgadillo-Velazquez et al.  are also tested in this work. The processability of all blends is studied in detail in capillary capillary (kăp`əlĕr'ē), microscopic blood vessel, smallest unit of the circulatory system. Capillaries form a network of tiny tubes throughout the body, connecting arterioles (smallest arteries) and venules (smallest veins). rheometry to determine the effects of LCB on the onset of flow instabilities known as melt fracture. We are interested to know how the addition of various amounts of LDPE (of varying molecular weight) can affect the onset of flow instabilities such as surface, oscillating os·cil·late
intr.v. os·cil·lat·ed, os·cil·lat·ing, os·cil·lates
1. To swing back and forth with a steady, uninterrupted rhythm.
2. , and gross melt fracture. In addition, how the details of flow, particularly the magnitude and period of oscillations oscillations See Cortical oscillations. are influenced by the presence of small amounts of LLDPE. Can such flow details be used to detect small amounts of LDPE. Surprisingly, it is reported here that oscillating melt fracture flow details are extremely sensitive to such subtle changes in the structure of polymers.
Polyethylene Resins and Blends
The LLDPE resin used in this study was a Ziegler-Natta, hexene copolymer, synthesized syn·the·sized
1. Relating to or being an instrument whose sound is modified or augmented by a synthesizer.
2. Relating to or being compositions or a composition performed on synthesizers or synthesized instruments. by ExxonMobil (LL3001). The LDPE resins used in this work are LD200 by ExxonMobil, EF606A by Westlake Polymers; and finally 662I and 132I, provided by Dow Chemicals. Table 1 lists all the polymers used along with their melt indices and densities. The LDPE resins have been labeled as LDPE-I to IV in order of increasing molecular weight.
The LLDPE resin was melt blended respectively with each LDPE resin in order to create LLDPE/LDPE blends having weight compositions of 99/1, 95/5, 90/10, 80/20, 50/50, and 25/75. The blending was performed as follows: the original components were mixed and grinded in a Brabender mixer mixer, either of two electronic devices in which two or more signals are combined. In the type of mixer used in radio receivers, radar receivers, and similar systems, a signal is translated upward or downward in frequency. in order to reduce their pellet pel·let
1. A small pill; a pilule.
2. A small rod-shaped or ovoid mass, as of compressed steroid hormones, intended for subcutaneous implantation in body tissues to provide timed release over an extended period of time. sizes. Then, the mixture in the form of flakes was blended into a single screw extruder, at low processing speed See MHz. (3-4 rpm), using a screw having mixing elements near to the end of the metering zone. The produced extrudates were then pelletized for easy handling. The blend 99/1 was produced in two dilution steps, the first being the 95/5.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
Parallel-plate rheometry was performed to determine the linear viscoelastic Adj. 1. viscoelastic - having viscous as well as elastic properties
natural philosophy, physics - the science of matter and energy and their interactions; "his favorite subject was physics" properties of the pure components. Details on the linear viscoelasticity Viscoelasticity, also known as anelasticity, is the study of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like honey, resist shear flow and strain linearly with time when a stress is applied. of blends can be found elsewhere . Here we report the rheological properties of the pure components. The measurements were performed using a Rheometrics System IV (con-trolled-strain) and a Bohlin--CVOR (controlled-stress). Experiments performed at different temperatures, namely, 130, 150, 170, 190, and 210[degrees]C. Mastercurves were obtained and most results are presented at the reference temperature of 150[degrees]C.
The pure components and their blends were rheologically characterized in simple extension using an SER Universal Testing Platform [11, 12] from Xpansion Instruments. As described by Sentmanat (2003, 2004), the SER unit is a dual windup extensional rheometer that has been specifically designed for use as a fixture An article in the nature of Personal Property which has been so annexed to the realty that it is regarded as a part of the real property. That which is fixed or attached to something permanently as an appendage and is not removable. on a variety of commercially available rotational rheometer host platforms. The particular SER model used in this study, a model SER-HV-B01, was designed for use on a VOR VOR Vestibulo-ocular reflex, see there Bohlin rotational rheometer host system. Details of the experiments can be found elsewhere . Here we report only the extensional properties of the pure components.
[FIGURE 3 OMITTED]
Capillary extrusion measurements were conducted at 150 and 190[degrees]C using a capillary die having a diameter equal to 0.762 mm and a length-to-diameter ratio, L/D L/D Labor and Delivery
L/D Lethal Dose
L/D Lift/Drag (ratio)
L/D Low Dynamic
L/D Loading / Discharging Rate (shipping) , equal to 16. The onset of melt flow instabilities (melt fracture) was determined for the pure resins and their blends. The surface of the extrudates was analyzed an·a·lyze
tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es
1. To examine methodically by separating into parts and studying their interrelations.
2. Chemistry To make a chemical analysis of.
3. with an Olympus MIC-D microscope. Selective images of the extrudates are presented here.
RESULTS AND DISCUSSION
Rheological Characterization A rather long and fancy word for analyzing a system or process and measuring its "characteristics." For example, a Web characterization would yield the number of current sites on the Web, types of sites, annual growth, etc. of Pure Resins
Figure 1 depicts the complex viscosity of all polymers listed in Table 1 as a function of frequency for the pure resins at 150[degrees]C. For the case of LLDPE (LL3001), the viscosity curve approaches its zero-shear viscosity value at small frequencies and exhibits a certain degree of shear thinning A pseudoplastic material is one in which viscosity decreases with increasing rate of shear (also termed shear thinning). This property is found in certain complex solutions, such as ketchup, whipped cream, blood, paint, and nail polish. at higher ones. The zero-shear viscosity of the four LDPEs was not reached experimentally, as can be seen from Fig. 1, but were calculated by determining their relaxation spectrum of these resins using the linear viscoelastic master-curves at the reference temperature of 150[degrees]C. The values are listed in Table 1. Note that while LDPE II (EF606), LDPE-III (662I), and LDPE-IV (132I) possess a higher zero-shear viscosity than that of LL3001, the presence of LCB causes significant shear thinning and thus their viscosity becomes considerably smaller at high frequencies. Such behaviors are typically observed in the shear rheology of polyolefins [13-15].
The extensional rheological behavior of all resins is depicted de·pict
tr.v. de·pict·ed, de·pict·ing, de·picts
1. To represent in a picture or sculpture.
2. To represent in words; describe. See Synonyms at represent. in Fig. 2 at 150[degrees]C. In all cases the tensile stress tensile stress
See under axial stress. growth coefficient coefficient /co·ef·fi·cient/ (ko?ah-fish´int)
1. an expression of the change or effect produced by variation in certain factors, or of the ratio between two different quantities.
2. , [[eta].sub.E.sup.+], is plotted as a function of time for three different Hencky strain rates (although data are available for several other Hencky strain rates), namely 0.1, 1, and 10 [s.sup.-1]. For the sake of clarity, the material functions [[eta].sub.E.sup.+] have been multiplied by an appropriate factor (for convenience powers of 10 was used), as indicated on the plot. It can be observed that the LLDPE (LL3001) does not exhibit any degree of strain hardening hardening, in metallurgy, treatment of metals to increase their resistance to penetration. A metal is harder when it has small grains, which result when the metal is cooled rapidly. at any extension rate, an observation consistent with polymers of linear architecture [15-17]. In fact, it displays very little deviation from the linear viscoelastic envelope (LVE LVE Low Volume Exemption (EPA)
LVE Live Video Extension
LVE Linear Variable Etalon
LVE Linux Video Editor ), 3[[eta].sup.+]. The latter material function (3[[eta].sup.+]) has been determined independently from linear viscoelastic shear rheology measurements, plotted as a dashed line in Fig. 2. On the other hand, the four LDPEs show significant strain hardening (deviation from the LVE, 3[[eta].sup.+], also indicated for all resins by dashed lines) which is typically an indication of the presence of long branches [13, 15, 16].
[FIGURE 4 OMITTED]
The flow curves of the pure components and those of their blends, were determined at 150 and 190[degrees]C by means of the capillary rheometer as described earlier. For the first set of blends, LLDPE (LL3001.32)/LDPE (LD200), the results are shown in Fig. 3. First, a significant viscosity mismatch mismatch
1. in blood transfusions and transplantation immunology, an incompatibility between potential donor and recipient.
2. one or more nucleotides in one of the double strands in a nucleic acid molecule without complementary nucleotides in the same position on the other between the LLDPE (LL3001) and LDPE-I (LD200) can be observed (also seen in Fig. 1 from their complex viscosities). Because of this, addition of up to 20% of LDPE-I into LLDPE does not seem to have a significant effect on its viscosity. The flow curves seem to overlap. Differences can clearly be seen only at concentrations as high as 50 wt% of LDPE. Similar observations for this system were made by Delgadillo et al. .
The processability in capillary extrusion of the individual components and their blends are determined in terms of the onset of melt fracture phenomena, i.e. the critical shear rates Shear rate is a measure of the rate of shear deformation:
For the simple shear case, it is just a gradient of velocity in a flowing material. and stresses at which extrudate distortions appear. In general, there are three types of instabilities which might occur in the capillary extrusion of polyolefins . First, there is a critical shear stress shear stress
A form of stress that subjects an object to which force is applied to skew, tending to cause shear strain. at which small amplitude amplitude (ăm`plĭtd'), in physics, maximum displacement from a zero value or rest position. periodic distortions appear on the extrudate surface and these phenomena are known as surface melt fracture or sharkskin shark·skin
1. The skin of a shark.
2. Leather made from the skin of a shark.
3. A rayon and acetate fabric having a smooth, somewhat shiny surface. . At higher apparent shear rate values and in spite of the fact a fixed volumetric volumetric /vol·u·met·ric/ (vol?u-met´rik) pertaining to or accompanied by measurement in volumes.
Of or relating to measurement by volume. flow is used, the pressure and thus the shear stress oscillates between two extreme values because of a combination of wall slip and melt compressibility com·press·i·ble
That can be compressed: compressible packing materials; a compressible box.
com·press . This phenomenon is known as stick-slip or oscillating melt fracture . At higher shear stress values the flow becomes again steady, although gross distortions appear on the surface of the extrudate. The latter phenomena associated with gross extrudate distortions are collectively known as gross melt fracture .
[FIGURE 5 OMITTED]
As discussed earlier, the results for the first set of blends are plotted in Fig. 3. For pure LLDPE, the onset of sharkskin was observed to occur at a critical wall shear stress value of 0.19 MPa, a value consistent with other reported values in the literature [22, 23]. Table 2 lists all critical shear rate and stress values for the onset of all three types of instabilities at 150[degrees]C. It is noted that sharkskin and stick-slip phenomena does not occur in the case of pure LDPE-I, again consistent with previous reports . Addition of up to 20 wt% of LDPE into LLDPE does not seem to change the critical values for the onset of surface melt fracture behavior, which completely disappears at amounts of LDPE higher than 50 wt%. The onset of stick-slip phenomena was found to gradually disappear with increasing amount of LDPE and this is discussed later into more detail. Finally, the onset of gross melt fracture of blends seems to shift to smaller critical shear stress values with increase of LDPE amount, an observation consistent with the critical shear stress values of the pure components. Similar results were obtained at 190[degrees]C as can be seen from the second part of Table 2.
[FIGURE 6 OMITTED]
Figure 4 plots the flow curves of the pure components and their blends in system II, LL3001/EF606. Again, because of significant viscosity mismatch, no effect on the flow curve can be seen up to addition of 20 wt% of LDPE-II (EF606). Table 3 lists the critical shear rate and stresses for the onset of gross melt fracture phenomena. The results are similar to those reported for blend system I discussed earlier. First, sharkskin is not eliminated with the addition of small amounts of LDPE (i.e. no effect up to 20%). The effect on stick-slip is evident even at small amounts of LLDPE i.e. the amplitude of the oscillations gradually decrease even at amounts as low as 1 wt% LDPE. Finally, the onset of gross melt fracture of blends seems to shift to smaller critical shear stress values with increase of LDPE amount
Figures 5 and 6 depict de·pict
tr.v. de·pict·ed, de·pict·ing, de·picts
1. To represent in a picture or sculpture.
2. To represent in words; describe. See Synonyms at represent. the flow curves of blends of system III (LL3001/662I) and system IV (LL3001/132I). Viscosities of the two pure components in both these blend systems are closer, however, the effect of the addition of LDPE into LLDPE on their processability are similar to those reported above for the other two blend systems. The critical shear rate and shear stress values for the onset of melt fracture phenomena are listed in Tables 4 and 5, respectively. It is noted that the onset of gross melt fracture for the LDPE III (662I) and LDPE-IV (132I) occur at very low rates, less than 15 [s.sup.-1] for both resins.
Figures 7-10 show images of the typical extrudate appearances for the four blend systems at selected apparent shear rates (15, 100, 350, and 1000 [s.sup.-1]). In all blend systems similarities can be observed. Smooth extrudates are obtained at 15 [s.sup.-1] in most cases, shark-skinned extrudates at 100 [s.sup.-1], stick-slip or oscillating melt fractured extrudates at 350 [s.sup.-1], and finally gross melt fractured extrudates at 1000 [s.sup.-1].
[FIGURE 7 OMITTED]
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[FIGURE 15 OMITTED]
Stick-Slip Flow Regime
As discussed earlier, pressure oscillations were obtained in the capillary extrusion of LLDPE and LLDPE with the addition of LDPE up to about 10 wt%. In all blend systems (I-IV) these stick-slip or oscillating instabilities were eliminated with the incorporation of 20 wt% of LDPE. It is noted that pure LDPE does not exhibit such a flow regime. It was also noted that the addition of even large amounts of LDPE have little effect on the sharkskin and gross melt fracture behavior of LLDPE. Strikingly, the addition of only 1 wt% of LDPE into LLDPE has a significant effect on the oscillating melt facture fac·ture
The manner in which something, especially a work of art, is made: "the gummy surfaces, spectral smudges and woozy contours that . . . of LLDPE as can be seen in Figs. 11-14. The amplitude of the oscillations gradually decreases with increasing amounts of LDPE starting from even 1 wt%.
Figure 15 plots the amplitude of the oscillations as a function of the LDPE wt% addition. In all blend systems the amplitude decreases with increasing amount of LDPE (wt%). At 20 wt% of LDPE no pressure oscillations exist as these have been eliminated because of the presence of long branches.
Such effects at small LDPE concentrations could not be detected in shear rheology . For example, the blends with 1 wt% LDPE essentially shows the exact same shear behavior with the pure LLDPE in both capillary and parallel-plate rheometrical tests. Small differences could only be seen in extensional rheology only at high extensional rates i.e. greater than 5 [s.sup.-1] and only for the blends that include the LDPEs with the highest molecular weights. This is clearly illustrated in Fig. 16. Therefore, the oscillating flow regime is very sensitive to the presence of long chain branching. Since stick-slip is a phenomenon due to the combined effects of wall slip and compressibility , it seems that long branches suppress slip effects to a certain extend.
The processing behavior of a number of LLDPE/LDPE blends with emphasis on the effects of long chain branches was studied extensively in this work. A Ziegler-Natta, linear low-density polyethylene was blended with four low-density polyethylene LDPE's having distinctly different molecular weights. Capillary extrusion experiments revealed that the onset of sharkskin and gross melt fracture are slightly influenced with the addition of LDPE into LLDPE. However, it was found that the amplitude of the oscillations in the stick-slip flow regime, scales well with the weight fraction of LDPE. Amounts as low as 1% LDPE has a significant effect on the amplitude of pressure oscillations. These effects are clearly due to the presence of LCB. Since stick-slip is a phenomenon due to combined effects of wall slip and compressibility, the presence of LCB certainly suppresses wall slip effects. Furthermore, it was observed that the onset of this flow regime was shifted to higher shear rates with increase of LDPE content.
[FIGURE 16 OMITTED]
On the other hand, it was observed that shear rheology is not sensitive enough to detect the addition of small levels of LDPE. Extensional rheology (uniaxial uniaxial /uni·ax·i·al/ (u?ne-ak´se-al)
1. having only one axis.
2. developing in an axial direction only.
1. having only one axis.
2. developed in an axial direction only. extension) can detect levels of LDPE as small as 1 wt% only at high Hencky strain rates (typically greater than 5 [s.sup.-1]) and only for certain blends, particularly those with LDPE of high molecular weight (blend systems III and IV) It is suggested that the magnitude of oscillations is a sensitive method capable of detecting low levels of LCB and therefore can possibly be used for this purpose.
We thank DOW Chemicals (S. Costeux) for the materials supplied and valuable comments. One of the authors (D-V.O.) would like to acknowledge CONACyT for financial support in the form of a scholarship.
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A large molecule composed of thousands of atoms.
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Those methods used to convert plastics materials in the form of pellets, granules, powders, sheets, fluids, or preforms into formed shapes or parts. . Theory and Applications, Van Nostrand Reinhold, New York New York, state, United States
New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of (1990).
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O. Delgadillo-Velazquez, S.G. Hatzikiriakos
Department of Chemical and Biological Engineering, The University of British Columbia Locations
The Vancouver campus is located at Point Grey, a twenty-minute drive from downtown Vancouver. It is near several beaches and has views of the North Shore mountains. The 7. , Vancouver, British Columbia British Columbia, province (2001 pop. 3,907,738), 366,255 sq mi (948,600 sq km), including 6,976 sq mi (18,068 sq km) of water surface, W Canada. Geography
Correspondence to: Savvas G. Hatzikiriakos; e-mail: email@example.com
Contract grant sponsor: NSERC NSERC Natural Sciences and Engineering Research Council (Canada)
NSERC Naval Systems Engineering Resource Center , CONACyT.
TABLE 1. Properties of polyethylene resins used. Melt index Density (g/10 min) (g/cc) [[eta].sub.0] (Pa s) Resin (190[degrees]C) (25[degrees]C) 150[degrees]C LLDPE (LL3001.32) 1 0.917 24,557 LDPE I (LD200) 7.5 0.915 8,272 LDPE II (EF606A) 2.2 0.919 44,234 LDPE III (662I) 0.47 0.919 72,780 LDPE IV (132I) 0.22 0.921 132,065 TABLE 2. Critical shear rates and stresses for blend system I (LL3001/ LD200) at 150 and 190[degrees]C. Sharkskin MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) Critical shear rates and stresses for blend system I (LL3001/LD200) at 150[degrees]C LLDPE (LL3001) 0.19 50 1% LDPE 0.19 50 5% LDPE 0.19 50 10% LDPE 0.18 50 20% LDPE 0.17 50 50% LDPE 0.16 80 75% LDPE -- -- LDPE-I (LD200) -- -- Critical shear rates and stresses for blend system I (LL3001/LD200) at 190[degrees]C LLDPE (LL3001) 0.17 90 1% LDPE 0.17 100 5% LDPE 0.17 100 10% LDPE 0.17 100 20% LDPE 0.16 100 Stick-slip Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) Critical shear rates and stresses for blend system I (LL3001/LD200) at 150[degrees]C LLDPE (LL3001) 0.40-0.31 230 1% LDPE 0.37-0.28 250 5% LDPE 0.34-0.26 300 10% LDPE 0.33-0.27 350 20% LDPE -- -- 50% LDPE -- -- 75% LDPE -- -- LDPE-I (LD200) -- -- Critical shear rates and stresses for blend system I (LL3001/LD200) at 190[degrees]C LLDPE (LL3001) 0.42-0.39 850 1% LDPE 0.41-0.39 950 5% LDPE 0.42-0.41 950 10% LDPE -- -- 20% LDPE -- -- Gross MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) Critical shear rates and stresses for blend system I (LL3001/LD200) at 150[degrees]C LLDPE (LL3001) 0.42 700 1% LDPE 0.42 800 5% LDPE 0.41 700 10% LDPE 0.40 550 20% LDPE 0.46 700 50% LDPE 0.23 180 75% LDPE 0.14 100 LDPE-I (LD200) 0.13 400 Critical shear rates and stresses for blend system I (LL3001/LD200) at 190[degrees]C LLDPE (LL3001) 0.41 1100 1% LDPE 0.42 1100 5% LDPE 0.41 1100 10% LDPE 0.42 950 20% LDPE 0.41 950 TABLE 3. Critical shear rates and stresses for blend system II (LL3001/ EF606) at 150 and 190[degrees]C. Sharkskin MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) Critical shear rates and stresses for blend system II (LL3001/EF606) at 150[degrees]C LLDPE (LL3001) 0.19 50 1% LDPE 0.19 50 5% LDPE 0.17 50 10% LDPE 0.18 50 20% LDPE 0.17 50 50% LDPE 0.17 80 75% LDPE -- -- LDPE-II (EF606) -- -- Critical shear rates and stresses for blend system II (LL3001/EF606) at 190[degrees]C LLDPE (LL3001) 0.16 90 1% LDPE 0.16 90 5% LDPE 0.16 90 10% LDPE 0.15 90 20% LDPE 0.15 90 Stick-slip Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) Critical shear rates and stresses for blend system II (LL3001/EF606) at 150[degrees]C LLDPE (LL3001) 0.40-0.31 230 1% LDPE 0.39-0.35 350 5% LDPE 0.40-0.37 350 10% LDPE 0.41-0.40 450 20% LDPE -- -- 50% LDPE -- -- 75% LDPE -- -- LDPE-II (EF606) -- -- Critical shear rates and stresses for blend system II (LL3001/EF606) at 190[degrees]C LLDPE (LL3001) 0.42-0.39 850 1% LDPE 0.41-0.39 900 5% LDPE 0.40-0.39 900 10% LDPE -- -- 20% LDPE -- -- Gross MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) Critical shear rates and stresses for blend system II (LL3001/EF606) at 150[degrees]C LLDPE (LL3001) 0.42 700 1% LDPE 0.44 900 5% LDPE 0.42 700 10% LDPE 0.44 600 20% LDPE 0.48 600 50% LDPE 0.19 100 75% LDPE 0.15 80 LDPE-II (EF606) 0.10 90 Critical shear rates and stresses for blend system II (LL3001/EF606) at 190[degrees]C LLDPE (LL3001) 0.41 1100 1% LDPE 0.41 1100 5% LDPE 0.41 1100 10% LDPE 0.40 950 20% LDPE -- 950 TABLE 4. Critical shear rates and stresses for blend system III (LL3001/ 662I) at 150[degrees]C. Sharkskin MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) LLDPE (LL3001) 0.19 50 1% LDPE 0.19 50 5% LDPE 0.19 50 10% LDPE 0.19 50 20% LDPE 0.19 50 50% LDPE 0.19 50 75% LDPE 0.17 50 LDPE-III (662I) -- -- Stick-slip Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) LLDPE (LL3001) 0.40-0.31 230 1% LDPE 0.37-0.30 300 5% LDPE 0.36-0.32 300 10% LDPE 0.37-0.34 300 20% LDPE -- -- 50% LDPE -- -- 75% LDPE -- -- LDPE-III (662I) -- -- Gross MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) LLDPE (LL3001) 0.42 700 1% LDPE 0.42 700 5% LDPE 0.39 700 10% LDPE 0.43 700 20% LDPE 0.40 300 50% LDPE 0.17 40 75% LDPE 0.13 25 LDPE-III (662I) 0.09 15 TABLE 5. Critical shear rates and stresses for blend system IV (LL3001/ 132I) at 150[degrees]C. Sharkskin MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) LLDPE (LL3001) 0.19 50 1% LDPE 0.18 50 5% LDPE 0.18 50 10% LDPE 0.19 50 20% LDPE 0.19 50 50% LDPE 0.20 50 75% LDPE 0.17 50 LDPE-IV (132I) -- -- Stick-slip Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) LLDPE (LL3001) 0.40-0.31 230 1% LDPE 0.39-0.35 350 5% LDPE 0.45-0.41 350 10% LDPE 0.40-0.36 300 20% LDPE -- -- 50% LDPE -- -- 75% LDPE -- -- LDPE-IV (132I) -- -- Gross MF Polymer [[sigma].sub.w] (MPa) [dot.[gamma].sub.A] ([s.sup.-1]) LLDPE (LL3001) 0.42 700 1% LDPE 0.43 700 5% LDPE 0.42 700 10% LDPE 0.40 500 20% LDPE 0.41 300 50% LDPE 0.23 70 75% LDPE 0.16 30 LDPE-IV (132I) 0.10 15