High load melt flow rate

MDPE has an average molecular weight of between 200 and 300 kg/mol and a broad molecular weight distribution (MWD). MDPE film raw materials have a high load melt flow rate (HLMFR) of between 10 and 25 g/10 min. 

HLMFR High load melt flow rate... 

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. 

A peroxide concentrate for polypropylene has been developed as an alternative to liquid peroxide for melt flow modification of recyclate and oflf-grade PP material by Polyvel. It is safe to touch, with 20% active peroxide level, which is constant until used. A high level of active peroxide is said to make the material very economical a 1% loading can increase the melt flow rate of standard PP to over 150 g (10 min). ... 

Copolymer type and melt flow rate also influenee the creep behaviour. Copolymer grades of PP have substantially lower ereep modulus than the homopolymer grades. PP has a similar modulus to high density PE, but its resistance to creep is much better and, at a equivalent time under similar load, the creep modulus of PP is more than that of high density PE. However, the ereep resistance of amorphous plastics is much better than the semi-crystalline plastics such as PP and PE. Creep resistance of PP could be further improved by addition of fillers or reinforcements. The creep behaviour of moulded artefacts is affected by the residual stress or orientation effect in the moulded article. 

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-... 

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