Have you ever come across this scenario?
Using the same resin, same equipment, and same production process, how is it possible that when using a new batch of color masterbatch, the plastic product exhibits:
Black spots, color spots
Inconsistent color
Streaks or opacity
Increased filter screen pressure
Reduction in film clarity
These defects are not due to equipment problem but color masterbatch dispersion problem.
In the plastic manufacturing process, masterbatch seems to simply be an insignificant number of "color concentrate pellets" that are used; however, it actually comprises three basic ingredients: pigment, carrier resin, and dispersant. Any poor handling of these ingredients leads to poor dispersion of color masterbatch.
This article will discuss from a practical manufacturing standpoint:
Why does masterbatch disperse poorly?
What influences pigment dispersion?
How to resolve masterbatch dispersion problems?
How to select a masterbatch supplier with high dispersion capabilities?
1. What is Masterbatch Dispersion Problem?
5. Characteristics of High Dispersion Masterbatch
Masterbatch Dispersion Problem is defined as the failure of pigment particles of masterbatch to disperse uniformly inside the plastic mixture, leading to an uneven color, particle defect, or poor performance of the end-product.
In simple terms:
Masterbatch can be compared to a glass of water with tomato juice in it.
In case the tomato juice is well-dispersed, the color will be uniformly spread throughout the glass;
If the tomato juice is not well-dispersed, then:
Pale coloration at the top
Settling of particles at the bottom
Uneven concentration in different parts
This is the same case with pigments in plastics.
Under ideal circumstances:
Particles of pigment must:
✅ Disperse evenly
✅ Combine completely with resin
✅ Avoid making clusters
But, in practical production processes, due to different reasons,
Pigments get:
Pigment agglomeration
It is also one of the primary causes of poor dispersion in masterbatches.
It is the most prevailing reason.
Pigment particles are usually very small; they usually get down to micrometer or even nanometer level.
The smaller the pigment particles:
Large surface area
Large surface energy
Easy mutual adsorption
As an illustration:
Carbon black is the case in point.
Though the high color carbon black gives better jetness, because of its small size and large specific surface area, it is more susceptible to:
Difficulties in dispersion
Increase in viscosity
Increase in filtration pressure
Thus, high performance black masterbatch does not only mean high carbon black content.
What really counts is:
The ability to disperse carbon black.
Many people assume that:
Bad dispersion of masterbatch is merely a matter of equipment.
But in reality, bad dispersion is actually due to a faulty formulation.
The main components of masterbatch are:
Pigment
Resin
Dispersant
The function of dispersant acts as "lubrication".
It will help pigment to:
Break down agglomerates
Distribute into the resin
Distribute evenly
However, different pigments need different dispersants.
Like for instance:
Inorganic pigments:
TiO₂
Iron oxide
and Organic pigments:
Phthalocyanine blue
Organic red
Their surface property is totally different.
If the dispersant used is wrong, no matter how good the equipment is, you might get the following:
Color spots
Flow marks
Strange filter readings
This is an issue that customers find easy to ignore.
Masterbatch should not be used on its own, but rather it must go into the plastic systems of the customers.
For instance:
For PP film
Recommended:
- PP Carrier Masterbatch
For PE film
Recommended:
- PE Carrier Masterbatch
For PET fiber
Recommended:
- PET Carrier Masterbatch
In case there is an incorrect carrier, the following things will happen:
- Melting problems
- Viscosity problem
- Pigment release problem
For instance:
If you try to add oil into water, no matter how you stir them, they won't blend.
Besides formulation, the production process is equally important.
Requirements for masterbatch manufacturing process include:
High speed mixing
Twin screw extrusion
Multi level shearing
It helps in breaking up agglomeration of pigments. In case:
Screw design is not proper
Low temperature
Low shear force
The pigment cannot be completely dispersed.
Result:
Appearance of black spots
Color variation
Low Temperature:
The resin will not be able to melt.
Effect:
Pigments cannot be dispersed
Insufficient Dispersion
High Temperature:
Can cause:
Resin Decomposition
Discoloration of Pigments
Additives Failure
Thus, a good masterbatch designer is not only concerned with temperature but should also design on the basis of:
Carrier
Pigments
Additives
In case of demanding applications like films and fibers:
Filtration efficiency is extremely important.
When the masterbatch has:
Undispersed pigments
Impurities
Gel particles
It leads to problems such as:
Screen blockage
Fiber breakage
Film surface defects
Thus, many customers check for:
Dispersion grade
Pressure value of filtration
Screen pack efficiency
Once the issues regarding masterbatch dispersion have been identified, the typical initial response from many organizations is:
"Would switching machines help solve the issue?"
However, from our experience in manufacturing, most masterbatch dispersion issues do not arise from one simple reason.
To solve such issues effectively, all four aspects must be optimized simultaneously:
Raw Materials
Formulation
Manufacturing Process
Application Environment
Below, we will analyze based on the actual manufacturing logic.
Pigment is the core factor affecting masterbatch dispersion performance.
There are significant differences between different pigments:
For example:
Benefits:
Bright colors
High tinting power
But:
High surface energy
Tendency to agglomerate
For instance:
Titanium dioxide
Iron oxide
Features:
Stable
Resistant to weather conditions
But:
Large particles
Likely to cause particulate issues
The most common type of hard to disperse material is carbon black.
In particular,
High Jetness Black Masterbatch
It must satisfy at the same time all these requirements:
High jetness
High dispersion
Low filter pressure
That is why good black masterbatch manufacturers usually spend considerable efforts on:
Selection of carbon black
Its surface treatment
Dispersing technologies
etc.
Most dispersion problems associated with masterbatch can be blamed on:
compatibility of carrier resin.
Ultimately, the masterbatch needs to be able to incorporate into the customer's plastics.
For instance:
| Customer Resin | Recommended Carrier |
|---|---|
| PP | PP carrier |
| PE | PE carrier |
| PET | PET carrier |
| PA | PA carrier |
| ABS | ABS carrier |
In case of improper selection of carrier:
Even though the pigment has been evenly dispersed in the masterbatch,
after incorporating into the customer's product:
It won't disperse readily.
End result:
Color unevenness
Inadequate concentration
Surface defects
Dispersion agent is the core ingredient for enhancing dispersion in master batch.
Functions of Dispersion Agent:
1st
Decrease interaction between pigments
To prevent:
Agglomeration of pigments
2nd
Increase compatibility between pigment and resin
So that pigment can:
"Go into the plastic"
Instead of:
"Stick together".
A good dispersion system can provide:
Less dose
Stable color
Good filtration effect
Manufacturing masterbatch is more than "just mixing the pigment with the plastic".
It involves:
Mixing of raw materials
↓
Melting
↓
Dispersion
↓
Extrusion
↓
Cooling
↓
Pelletizing
Every step influences the dispersion quality.
Based on:
Type of pigment
Viscosity of carrier
Dosage
Design shear zones.
Have to be assured of:
Complete melting of the resin,
Without:
Thermal decomposition
Alteration in color
Too little time:
Insufficient dispersion.
Too much time:
Could result in:
Resin degradation
Additive consumption
While buying masterbatch, customers always consider only:
"What is the price of the masterbatch?"
However, the factor that actually determines the cost is:
Production efficiency in the end.
A cheap but poor dispersing masterbatch will result in:
Higher product rejection rate
Frequent filter screen changing
Machine idle time
Thus, while choosing high dispersion masterbatch, it is advisable to consider the following factors.
Good masterbatch shall guarantee:
Among various batches:
Minimal difference in color
Consistency in concentration
In particular for:
Film
Fiber
Automotive interiors
It is highly crucial to maintain color consistency.
For：
BOPP Film
PET Fiber
Spunbond nonwoven
Performance in filtration process is highly crucial.
Good masterbatch will not cause rapid:
Increase in filter pressure
Screen blockage
Excellent masterbatch shall be compatible with:
Injection molding
Blow molding
Film extrusion
Fiber spinning
Different processing methods.
Different products have different dispersion requirements.
This industry demands the use of masterbatches in a relatively strict manner.
Issues include:
Black spots
Fish eyes
Color streaks
Reduced transparency
Suggested solutions:
It is advisable to select:
High dispersion color masterbatch
Carrier resin
Low filter pressure masterbatch
Particularly:
BOPP、CPP、PE film
Demand
For example:
PET fiber
PP fiber
BCF yarn
The fiber making rate is very fast.
When the masterbatch dispersion becomes poor, it leads to:
Fiber breaking
Blockage of spinneret
Change in colour
Thus, fiber-grade masterbatch typically needs:
Higher filtration grade
More stable melt flow
Even though the injection molded products have lower filtration demands,
these have higher demands for:
Surface quality
Color consistency
high requirements.
For example:
Automotive components:
If the following occur:
Cloud patterns
Color spots
It will directly affect appearance.
Masterbatch is not a simple color product.
It is actually:
A combination of material science + formulation engineering + processing technology.
A professional masterbatch manufacturer needs to have:
Based on:
Resin
Application
Process
Design solutions.
Including:
Pigment selection
Carrier selection
Additive compatibility
Excellent suppliers will not only provide:
TDS.
They should also test:
Injection molding
Film extrusion
Fiber spinning
To verify real performance.
During actual production, we discovered that:
The problem of many customers is not "lack of awareness on the need for masterbatch",
but rather, they do not know:
The type of masterbatch that would suit their production process.
Standard Polymer is concerned with:
Color Masterbatch
Functional Masterbatch
Custom Masterbatch solutions
Based on customer needs, we start from:
Select suitable:
Organic pigment
Inorganic pigment
Carbon black
Match:
PP
PE
PET
PA
ABS
PC
and other carriers.
Targeting:
Film
Fiber
Nonwoven
Injection molding
Provide customized solutions.
Our goal is not simply to provide color,
but to help customers:
Reduce production problems,
Improve product stability.
If your product shows:
Color spots
Black spots
Color difference
Filter pressure increase
We suggest testing in the following sequence:
Step 1:
Verify the suitability of the pigment.
↓
Step 2:
Verify compatibility of carrier resin.
↓
Step 3:
Tune the dispersant system.
↓
Step 4:
Modify process conditions.
↓
Step 5:
Select a masterbatch manufacturer with good dispersion capacity.
To improve masterbatch dispersion, you need to simultaneously optimize:
pigment choice
carrier resin
dispersing agent
extrusion process
Modification of one parameter alone may not be able to help in this regard.
Main causes include:
pigment agglomeration
poor dispersion
incompatible carrier resin
insufficient mixing
We recommend checking the masterbatch dispersion grade first.
No.
Higher pigment content may bring:
Higher tinting strength
But it may also lead to:
Dispersion difficulty
Processing performance decrease
Excellent formulations require balance.
We recommend focusing on:
Whether they have practical processing test capability
Whether they provide application data
Whether they understand different resin systems
Whether they can provide customized solutions
Not recommended.
Because:
Although PP and PE are both polyolefins,
But:
Melting point
Flowability
Molecular structure
There are differences.
It is best to choose products with matching carriers.
Common causes:
carbon black loading too high
unsuitable dispersant
poor carrier compatibility
insufficient shear mixing
Black masterbatch especially requires attention to carbon black dispersion capability.
In choosing the masterbatch, do not just consider its color appearance. It is the dispersion technology used to achieve the color that decides the quality of your product.
For more information about our masterbatch manufacturer with stable color, excellent dispersion performance and professional technical support, please feel free to contact us for sample test and technical evaluation.
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