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Why need fillers?

 
 
Save Cost

Fillers are used to displace more-expensive resin and provide cost savings to customers.
Calcium carbonate (CaCO3), being one of the most abundant minerals in nature, is traditionally used in plastics as a filler to reduce the cost of expensive polymers. In addition, these minerals will often have lower heat capacities than polymers, meaning they are more readily heated and cooled, further affecting cooling cycle time. This, combined with reduced material cost, can be a great productivity boon to producers.


Reinforce
The major proportion of plastics used for the technical application is thermoplastics (PE/PP/PS/PET). However, they commonly are relatively weak, low stiffness, limiting the wider application.By filling with rigid particles, the stiffness, modulus of elasticity, hardness tensile stress at break, melt viscosity are ameliorated significantly.

Types of fillers

 
 
What kind of materials can be used as fillers? 
think about why we use fillers:
 
→easy to obtain: availability in nature and cheap
 
→with good mechanical properties: stiffness/ tensile strength/ impact strength
 
 

Classification of fillers

 

 
Properties
Application
Minerals
CaCO3 reinforcing , water and gas barrier
Package:PE-base film,PP woven  sacks,biodegradable bags
PS refrigerator liners
Talc hydrophobic,softest ,increasing HDT , rigidity and wear resistance Automotive(used with PP):bumper
household appliances,engineering plastic hard ware
Anti-block additive
Kaolin/clay non-reinforcing, good electrical properties,increasing
heat preservation
PE greenhouse film
Improve the flow properties of glass-reinforced compounds
Mica reinforcing,increasing tensile strength, flexural modulus, and HDT Automotive(usually with PP):Motor fan blades
BaSO4 increasing acid,alkali resistance and opacity
increasing the density
Automotive :used with PP/PS  in proportions up to 70%
Fibers
natural coir/palm/bamboo/sisal/asbestor… Building application etc; 
Synthetic glass/carbon/ceramic/boron… Engineering plastic: glass fiber used with PA
 
 

Challenges for processing filler masterbatch

 
 
 
Feeding with high filler loading
When feeding low-bulk density filler particles, feed limitations are often encountered. 
It is necessary to remove a large volume of air in order to efficiently feed the material more easily, as it tends to be too easily fluidized. Feeding limitations are also encountered ,reducing the output .Second ,when the loadig of filler is high,filler tends to agglomerate in the kneading units.To solve the problem as best as possible, we provide two alternative paths to feed the polyolefins with fillers and additives according to the formula, application and expected output:
 
Premix: Before fed throug hopper, the carrier resin,fillers and additives are pre-mixed in a high speed mixer
Split-feed :materail fed into twin screw extruder through sevaral Loss-in-weight dosing units
 
Distribution and Dispersion of the filler particles into polymer matrix
For reinforcement to be effective, Minerals,fibers,depending on their structure, need to be distributed and/or dispersed. This is the basis for high quality final product.To achieve a good level of distrubution and dispersion, two steps are essential:
 
     Surface modification of filler
Increase adhesion of matrix/filler,prevent void coalescence, which would affect physical properties thermal behavior and mechanical properties
Decrease of particle-particle interaction,prevent particle agglomerate,which would cause dispersion and performance problems
 

    Compounding the martix on twin screw extruder 

The co-rotating twin-screw extruder has long been the equipment of choice for such compounding functions. The high compounding capacity  of twin screw extruder will make up for the unsufficient surface modificaiton and adhesion of matrix/filler. The extrusion equipment coulde be designed  to meet  requiremnets for different application scenarios.
 
 
Cooling and pelletizing 
   Cooling:
   water-cooling:water-ring, underwater, water bath
   air-cooling:die-face,convey belt
  Pelletizing:
  strand  cut: water bath,air convey-belt
  die-face cut:underwater, water-ring
 
When PE is used as the carrier resin, it is suitable to choose the air-cooling die face hot cut. For application in blowing film, the shape and size of the particles are  generally with a diameter of 3 ~ 5mm round sheet ,the thickness of about 1mm. This allows  a quick melting and easy mixing with the matrix resin material in a short time when blowing.
 
However,when the diameter of the extruder is large (such as the diameter of Φ72mm or more) and the output is higher than 300kg/h, the die head for  is difficult to  handle  well.As a result, the temperature is not easy to control.The particles can not cool down and easy to stick. At this time, it is appropriate to use the conveyer belt cooling method, and this method is suitable for the production of various filled masterbatches or modified special materials, but it requires a larger site to layout the lines.
 
In a word , the choice of pelletizing system depends on applicaiton, formulation,and output.

Benefits of JIEYA twin screw extrusion systems 

 
High filler loading
 Enhanced feeding systems allows high loading of low-bulk-density mineral filler and still maintain an economically viable production rate.

High dispersion 
Mechanical shearing by two co-rotating screws with segmented elements faciliate dispersion and distribution of filler particles into polymers.

Accurate control
Modular designed barrels with heat/cool systems enable accurate control of temperature, pressure ,residence time in different processing units,ultimately affecting dispersion of the composites.
 
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