Masterbatch is added to plastic through a dosing and mixing process during plastic manufacturing. Here’s how it typically works:
1. Preparation of Masterbatch
- Masterbatch comes in pellet, granule, or powder form, with pigments or additives highly concentrated in a carrier resin.
- It is designed to mix easily with the base polymer (like PE, PP, ABS, PVC, etc.).
2. Feeding into the Processing Machine
There are two main ways to introduce masterbatch into plastics:
a) Dry Blending (Premixing)
- Masterbatch pellets are pre-mixed with natural polymer pellets in a specific ratio (e.g., 2–5% masterbatch to 95–98% base polymer).
- This blend is then fed into the hopper of an extruder, injection molding machine, blow molding machine, or film blowing line.
b) Automatic Dosing
- A gravimetric or volumetric dosing machine automatically meters the right amount of masterbatch and mixes it with the polymer at the hopper inlet.
- This ensures precise color consistency and additive distribution, especially in large-scale production.
3. Melting and Dispersion
- Inside the machine (extruder, injection press, etc.), heat and shear force melt the polymer and disperse the masterbatch evenly throughout the molten plastic.
- The pigment or additive becomes uniformly distributed, giving the final product the desired color or functional property (UV resistance, flame retardancy, anti-fogging, etc.).
4. Shaping into Products
- The molten blend is processed into the final form: film, sheet, fibers, injection-molded parts, blow-molded bottles, or extruded profiles.
✅ In short: Masterbatch is added to plastic either by premixing it with the base polymer or by using dosing equipment, then melted and dispersed during processing to achieve consistent color and performance.
How to Calculate and Add the Right Amount of Masterbatch to Plastic:
? 1. General Dosage Range
- Color masterbatch: usually 1–5% of the total weight of polymer (sometimes up to 10% for very strong colors).
- Additive masterbatch (UV stabilizers, flame retardant, anti-fog, etc.): typically 2–10%, depending on the required property.
- Filler masterbatch: can be 10–50% or more, since the goal is cost reduction or property modification rather than color.
? 2. Basic Calculation Formula
The formula for calculating the required masterbatch is:
Example:
- You want to produce 100 kg of plastic products.
- The required masterbatch dosage is 3%.
100 kg × 3% = 3 kg of masterbatch
So you’ll mix 97 kg polymer + 3 kg masterbatch.
? 3. Using Let-Down Ratio (LDR)
In industry, dosing is often described as a let-down ratio (polymer:masterbatch).
Formula:
LDR = Weight of Polymer ÷ Weight of Masterbatch
Example:
- A 2% dosage corresponds to an LDR of 50:1 (50 parts polymer : 1 part masterbatch).
- A 5% dosage corresponds to an LDR of 19:1.
? 4. Factors Affecting Dosage
- Pigment strength – Strong pigments (like carbon black) need less masterbatch (0.5–2%), while weak pigments (like white TiO₂) may need more (3–8%).
- Polymer type – Some plastics disperse pigments more easily (PE, PP), while others need higher dosage.
- Application – Outdoor products need higher additive masterbatch dosage (UV stabilizers, flame retardants).
? 5. Practical Method
- Small batches: Pre-mix polymer pellets and masterbatch manually or with a tumble mixer.
- Large batches: Use an automatic gravimetric dosing system to ensure precise masterbatch feeding.
✅ Quick Reference Table (typical usage):
| Masterbatch Type | Dosage Range | Example Application |
|---|---|---|
| Color masterbatch | 1–5% | Packaging, toys, films |
| White masterbatch (TiO₂) | 2–8% | Pipes, bottles, sheets |
| Black masterbatch | 0.5–3% | Agricultural films, cables |
| Filler masterbatch | 10–50% | Cost reduction, stiffness |
| UV masterbatch | 2–5% | Outdoor furniture, films |
| Flame retardant MB | 5–10% | Electrical parts, building materials |