Compounding was done with a twin-screw extruder at 220Deg C,300rpmand nitrogen(1,5 bars) was used to make the compounding stepas inert as possible.HDPE powder and additives were mixed mechanically before compounding.Multiple extrusions were done with a single screw extruder under air atmosphere.

To transition from LLDPE to a material with similar os lower MI PEs(ie.,higher viscosity PEs),the expected purge time should be 10-20minutes or less.Once the product run is over,remove the LLDPE blend from the chute of the extruder's hopper,andthoroughly clean the hopper to ensure that all the material is gone.If the new PE material has much less viscosity(much higher MI) than the exsiting LLDPE,then a LDPE with an intermediate MI is recommended as an additional step.

To purge LLDPE with pigment MB out of the system,it is expected thatthe process will take about 15-45minutes,sometimes longer,depending on the pigment and the die characteristics.Once the product run is over,the operator needs to remove the LLDPE +pigment MB from theChute of the extruder's hopper,and thoroughly clean the hopper to ensure thatall the materials is clean.Purge using the "Alt-Disco"purge technique with a 1MI LLDPE or a 0.8-1 MI LDPE(depending on the next Materials) while maintaining the bubble and making sure that the temperatureprofile is maintained(sometimes lowering the temperature profile by 10-15Deg C can shorten changeover time).

To transition out of PA or EVOH,the average transition time should be about15-45minutes depending on the size and design of the die.Once the product yun is over,the operator needs to remove the PA or EVOH from the chute of theextruder's hopper and tgoroughly clean the hopper by using a vacuum to ensure that all the materials is clean.It is also an ideal time to clean the hopper's magnet by vacuum and to make sure that there are no pellets left hanging in the gravimetric system/blenders.

Even though all these polyethylenes are around 1 MI,it can be seenthat at both temperatures,the LDPE has much lower viscositiesthan those of LLDPE and mLLDPE.

Customers demand film structure versatility when purchasing extrusion lines as they arerequired to produce a variety of products.This generally means that the processors have more job changes.To handle the operation

A typical 5 -layer film structure,consits of a core layer of EVOH as a barrier layer,inner and outer layers of LLDPE,and"tie" or adhesive layers to join togetherthe otherwise incompatiable LLDPE & EVOH.This structure is ubiquitous today, and is used in many applications.For the many basic package structures,a 5-layer film obviates the need for an adhesive lamination step.Some might agrue that the modulus of oriented PP & PET films are greater than unoriented nylon films,and that laminations are superior to unoriented blown films,and that the film structure is inadequate for many packaging applications.

It has been recognized that 3-layer films have limits,such as with oxygen barrier,or print quality.To solve this issue,many 3 -layer films were used as part of anadhesive lamination to reverse-printed films to achieve higher quality structures,eigther to other 3 layer films and foil for improved bar

LDPE also has a broader molecular weight distribution(MWD).Again,a polymer with a broader MWD also exhibits a higher shear-thinning behaviour.On the contrary,mLLDPE echibits a narrower MWD,and therefore,the viscosity does not decreaseas much at higher shear rates.Comparing figures 2.and3,it is quite evident that the zero-shear viscosity of LDPE is much lower than that of mLLDPE and LLDPE.

Drying can have a major impact on the speed and operaility of a coating process.Dryer performance can also significantly alter the product quality.There are numerous factors that can affect drying that are easily overlooked oravoided because ther are seen as too complicated in the design and operation of coating Equipment.