Viscosity is a measurement of the resistance of a material to flow.A material that can flow eaily has a low viscosity whereas a material that can notflow easily has a high viscosity.Quantitatively,it is defined as:u(y)=r/yWhere u is the shear viscosity in pasec,r is shear stress in Pa and y is the shear rate in 1/sec.Polymers exhibit shear-thinning behaviour in suc a way that as the shear rate increases,the shear viscosity decreases as indicated in figure 1.

The purging time for any system varies depending on several factors:1.The type of materials that need to be purged. For example,transitioning from a LDPE to a LLDPE is much faster than going from a LLDPE to a Nylon.

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.

Pouches with an outer layer made of paper are a big trend.The favourable haptics and the better envoiremental friendly reputation of paper might be the main causes for this.The question is does the latter contest the substantive truth of the facts,and how to recycle such products?

These days,imposing bans on plastic bags seems to be a common reflex action among politicians when fishing for votes.There is a suspicion that the bans are not only counterproductive for the environment,but also have very negative effects on the economy.

Customers are demanding more sustainable film products made from less materials,while at the same time they demand higher performance.To master this balancing act,a joint project of suppliers has developed an approach to down gaugefilms while increasing their properties.