High-load melt index

MFR defined as the ratio of the high load melt index to the low load melt index... 

Another value is also measured on the plastometer at 190 °C, but under a load of 21.6 kg (ASTM D 1238-04C Condition 190/21.6). This is called the high load melt index (HLMI) and is also reported in g/10 min or dg/min. HLMI is often used for polyethylenes that have very high molecular weights. Because it may be difficult to measure the small amount of extrudate from the standard conditions for what are called "fractional" MI products (typically resins that have Mis <1), HLMI may be a more accurate measure of molten flow. 

Relaxation time distribution breadth 2,4-dimethylpentad ienyl environmental stress crack resistance high-density polyethylene high-load melt index Janzen-Colby... 

FIGURE 39 High-load melt index and molecular weight (Mw) values of polymers made at three densities by adjusting the amounts of 1-hexene added to the reactor. The addition of comonomer tended to decrease the polymer MW (raise HLMI). 

XRF analysis0 Activity (gg 1 h ) High-load melt index (g (10 min)-1) ... 

Now let us consider the so-called polymer processability, which is represented by the MFl ratio measured at 10 and 2.16 kg loads, namely HLMI/Ml (high load melt index over melt index) (Table 17.21)... 

High-load melt index n. (1) The rate of flow of a molten resin through an orifice 2.096 mm in diameter and 8.000 mm long at 190°C when subjected to a pressure difference of 2.982 MPa. Shah V (1998) Handbook of plastics testing technology. John Wiley and Sons, New York. 

High load melt index ASTM D1238 High 34.14 23.22... 

The ethylene polymerization of this catalyst was carried out in an autoclave reactor at 221°F in isopentane as the slurry solvent in the presence of triisobutylaluminum as cocatalyst and 50 psig of hydrogen and sufficient ethylene to achieve a total reactor pressure of 550 psig. The catalyst activity was 10,540 g of PE/g of catalyst/ hr, which corresponded to an activity of 146,000 g PE/g Ti/hr. The granular polyethylene product obtained was considered suitable for a particle-form slurry process such as the Phillips slurry process. The polyethylene sample displayed a Melt Index (I value of 0.70 and a High Load Melt Index ) value (HLMI) of 3 1 with a HLMI/MI ratio of 45, which indicates tfiat the polyethylene molecular weight distribution was of an intermediate value. 

Two main types of viscometers are suitable for the determination of the viscosity of a polymer melt The rotation viscometer (Couette viscometer, cone-plate viscometer) and the capillary viscometer or capillary extrusiometer. The latter are especially suitable for laboratory use since they are relatively easy to handle and are also applicable in the case of high shear rates. With the capillary extrusiometer the measure of fluidity is not expressed in terms of the melt viscosity q but as the amount of material extruded in a given time (10 min). The amount of ex-trudate per unit of time is called the melt index or melt flow index i (MFI). It is also necessary to specify the temperature and the shearing stress or load. Thus MFI/2 (190 °C)=9.2 g/10 min means that at 190 °C and 2 kg load, 9.2 g of poly-... 

Mechanical properties of polyethylenes vary with density and melt index. Low-density polyethylenes are flexible and tough high-density products arc quite rigid and have creep resistance under load. Toughness is the primary mechanical property affected by melt index, with lower-melt-index polyethylenes having greater toughness. Under loads, polyethylene is subject to creep, stress relaxation, or a combination of both,... 

Surface area Pore volume Pore Activity Melt index High-load Ml Mol. wt., M>... 

In order to overcome the shortcomings of the melt index method, high load MI (HLMI) has been introduced to indicate the grams of polymer pushed out of the barrel under the action of a heavier weight, usually 10 kg (or 21.6 kg). The ratio of the HLMI/MI indicate how shear thinning the resin is. The higher the ratio, the more shear thinning the polymer [8]. 

As with ATH, high loadings of MGH tend to embrihle polymers. A proprietary coating can restore the mechanical properties lost by adding the hydroxide. Compatibilisers can improve adhesion between metal hydroxides and nonpolar polymers. The melt flow index is drastically reduced by MGH. 

Chlorinated FRs have been used for many years in combination with antimony oxide in polyethylenes. The optimum FR antimony oxide ratio is 1 1, but the oxide can be minimized by increasing the ratio to 2 1 and even 3 1. For a UL 94 V-0 rating, the amount of additive required depends on the melt index of the polymer high levels being required for higher loadings. 

In a compound, important evaluation criteria are fluidity and dispersion. The common fluidity evaluation in the plastic material is the MFR, carried out by a melt indexer (Figure 5.34). However, in WPG of high content of wood flour, the usual MFR measurement is difficult, as fluidity becomes low in such cases, a capillary rheometer (Figure 5.35) is suitable. On the other hand, as MFR is simple, measurement can be improved by enlarging the diameter of the orifice of the melt indexer and increasing the load applied. However, at present, this measuring method only provides relative evaluation instead of absolute evaluation. 

Figure 7 Conductivity vs. carbon-black loading for (a) low-density PE with high melt-index (b), (c) poly(methyl methacrylate) of high and low melt-index, respectively and (d), (e) poly(vinyl chloride-co-vinyl acetate) with low and high degree of polymerization respectively (after M. Sumita, H. Abe, H. Kayaki and K. Miyasaka, J. Macromol. ScL, Phys. 1986, B25,171)...

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