Each type of additive masterbatch has some special properties to improve the end plastic product.



Polymer Processing Aids (PPA) are additives combined with the base polymer to improve the production process ability and processing characteristics of the material as well as improve the quality of the final product. More specifically, they improve the melt process ability and handling of high molecular weight polymers to improve the appearance of the final product by removing flow marks and die lines.
Polymer processing aid help in increasing blown film transparency, improving smoothness, product appearance and mechanical properties. The use of PPA facilitates to improve the surface quality of products, eliminate melt fractures and reduce die deposits.
Furthermorethe optimum utilization of PPA can reduce the defects (fish eye, shark skin, etc) observed in PE films during the process and it is economically beneficial as it helps in reducing the production costs of polymers due to enhanced efficiency and high quality of product.
Our PLAST PPA pertains to next generation extrusion process aides that improves product quality & operational efficiency of extrusion & blown film production lines. It comprises of high performance fluoro elastomers used in processing of low MFI extrusion grades of LLDPE and HDPE.
They function by continuously coating the die with a lubricating fluoro polymer which aids in processing of polymers which are highly susceptible to melt fracture due to die stress they undergo at the die exit. During polymer extrusion, the surface of the product is uneven above a critical shear stress (approx 20 N/cm2 ) which leads to “Shark skin” effect and this phenomenon is better known as “Melt Fracture”.

Effect of PPA & the phenomenon occurring inside the extruder

Rheology of polymers is complex, has it’s own quality problems that are often seen in the final product. Prior to describing how the PPA helps in manufacturing, let’s understand the root cause of the problem for surface flow disturbances such as gel formation, high working pressures with limiting output, die buildup, uneven thickness and many more.
The best option to deal with flow related problems is by carefully choosing the right source of raw materials & optimization of right process parameters. In spite of making these attempts, flow disturbances are bound to occur and additional
read moremeasures must be adopted to overcome and reduce them. This is where PPA plays a vital role in it. This is based on fluoro elastomers and fluoro polymers that contain fluorine (F), with greater affinity to metal than the poly olefin matrix. Thus, PPA cling to the machine’s walls, the screw barrel, and the die lips, significantly reducing flow disturbances and their results.
When the polymer flows on a stationary surface, the metal walls of the screw barrel and the die is subjected to great shear stresses and exhibits resistance to flow. Thus, the portion near the walls has a slow flow velocity,
read moredifferent from the flow velocity at the center of the melt. When the material reaches the die lips and is detached from them, there is no longer a fixed surface that impedes its flow. Over a short period of time and at a short flow distance, the outer layer of the polymer must “catch up” and increase its flow velocity to match the velocity of the rest of the melt as given in the figure below .

Illustration of the flow gaps between the melt velocity (V0) and the velocity along the die walls (V1).

After exiting the die, these velocities must even out. When the flow resistance of the material is high and the gap between the shear stresses and the melt velocity reaches a critical value, the polymer chains are overstretched, cannot cope with the velocity gap and “tear”. This phenomenon, also called melt flow disturbance, creates visual defects on the surface, PPA facilitates to overcome the same.
It has been well proven that work should begin with 15 minutes of rinsing with PPA processing at a high concentration (between 1.5% – 2%) in the outer layers. This makes it possible to rapidly get a good pre-coating of the extruder and the die walls. After continuous production for a day, PPA is added to the outer layer at a lower concentration (between 0.5% – 1%) thereby it is intended to preserve the initial layer created and maintain it in its entirety.

Additional features of PPA

The concentrates of PPA in a matrix of LDPE or LLDPE, usually have an additional synergistic component for enhanced activity. They are suitable for a wide range of temperatures, even at high temperature of 310 ºC. Some are even suitable for challenging MLLDPE-rich compositions known for their limited flow capabilities. It has excellent dispersion of the active material within the polymer matrix given in the figure:

Significant advantages of PPA

To reduce the friction between the melting/ molten polymer & the metal surface of barrel of extruder, providing a smoother production process throughout by improving flow characteristics such as viscosity, allowing the melt to slip through the die without sticking.
It eliminates melt fracture and shark skin effect while reducing die buildup, back pressure and increases output with reduced operating temperatures. This facilitates material flow in narrow die gap equipment and reduced gel formation with the polymer.
Results in yielding finished products with improved smoothness, gloss , transparency, surface aspects , aesthetic appeal , clarity by removing flow marks and die lines.
PPA reduces line shutdowns for cleaning, allows lowering work temperature and saving energy, and the presence of gels in the final product diminishes. Another advantage is that PPA is also work as additives to improve cleanliness and facilitates to exit faster from a color in production.
Even at very low addition rates @ 1% or ppm range, PPA gives consistent quality with improved mechanical properties & substantial output as well.
They are very effective for use in the production of high viscosity, high molecular weight polymers such as LDPE, LLDPE, LDPE, HDPE, PP, PS, and others.
Continuous usage of PPA results in higher productivity , lower operating costs due to lower cycle times and reduced operational down time due to longer continuous production runs in between cleaning and maintenance.
Facilitates energy savings due to lower friction between the equipment and the polymer that allows for lower operating pressure and motor torque within the extruder.
PPA is approved for food contact applications and deliver benefits across various applications viz., Blown Film , Cast films, Pipe extrusion , Wire & Cable, Blow molding, Fiber spinning and so on.

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