Polypropylene (PP) is one of the world’s most versatile thermoplastics. But for manufacturers, the value isn’t just in the material itself—it’s in the processing capabilities.
Whether you are producing high-concentration filler masterbatches, reinforcing PP with glass fiber, or upcycling post-consumer waste, the quality of your end product depends entirely on your extrusion technology.
At Useon, we move beyond the basics. Drawing from decades of experience in manufacturing twin-screw extruders for the global market—from Turkey to India—we provide the technology to turn raw PP resin into high-performance products.
Part 1: PP Applications & Recommended Machinery
Processing Polypropylene requires precise matching of machine torque, screw geometry, and processing technology. Based on our extensive project portfolio, we have matched specific PP applications to their ideal machine configurations below:
1. High-Performance Compounding (Fillers, Colors & Reinforcements)
Includes: PP+80% CaCO3, Glass Fiber Reinforced PP, Color Masterbatch
The Challenge:
- High Fillers: Wetting and dispersing up to 80% powder (CaCO3/Talc) without agglomeration.
- Reinforcement: Preventing fiber breakage to maintain impact strength in glass-fiber reinforced grades.
Useon Solution: High-Torque & Modular Screw Design.
We use a split-feeding strategy (Side Feeders) to introduce abrasive fillers/fibers downstream. This protects the melting zone from abrasion and allows for higher output rates.
Recommended Machine: SAT Series Twin Screw Extruder
- Best Models: SAT52, SAT65, SAT75, SAT95 (depending on output needs).
- Specific Torque: up to 10.3 Nm/cm³, optimized for high-loading PP compounds.
- L/D Ratio: 44-48 provides the optimal residence time for dispersive mixing.
- Wear Protection: Bimetallic barrels specifically chosen to resist abrasion from fillers.
2. Reinforced PP (Glass Fiber / Carbon Fiber)
Includes: Short Glass Fiber (SGF), Long Fiber (LFT), Carbon Fiber Reinforced PP
The Challenge:
Fiber Breakage: The goal is to improve stiffness, but aggressive shear breaks the fibers, drastically reducing the impact strength of the final product.
Useon Solution: Gentle Shear Configuration.
- Screw Profile: We utilize specialized “distributive mixing elements” (toothed blocks) instead of aggressive kneading blocks.
- Downstream Feeding: Fibers are introduced via a Side Feeder near the end of the barrel to minimize their residence time under shear, preserving the Average Fiber Length (AFL).
Recommended Machine: SAT Series Twin Screw Extruder
- Best Models: SAT52, SAT65, SAT75.
- Key Config: Modular Screw Design allows you to switch to a “Gentle Mixing” profile specifically for fiber reinforcement.
3. Eco-Friendly Bio-Composites (PP + Starch/Wood)
Includes: Biodegradable Compounds, Wood Plastic Composites (WPC)
The Challenge:
- Thermal Degradation: Natural fibers (Corn Starch, Wood Flour, Straw) burn and carbonize easily at standard PP processing temperatures.
- Moisture: Bio-fillers often contain high moisture, leading to bubbles.
Useon Solution: Low-Temperature Compounding.
- Temperature Control: We optimize the screw profile to generate minimal shear heat, maintaining a melt temperature below the degradation point of starch/wood.
- Degassing: Intense Multi-stage Vacuum Degassing removes the inherent moisture from natural fibers.
Recommended Machine: SAT Series Twin Screw Extruder
- Best Models: SAT65, SAT75.
- Key Config: High Torque is required to process the material at lower temperatures (colder melt = higher viscosity).
4. Reactive Extrusion (TPE / TPV Elastomers)
Includes: PP-based Elastomers, Dynamic Vulcanization
The Challenge: Intense Mixing & Reaction.
Producing TPV requires continuous, intense shear to thoroughly vulcanize the rubber phase within the PP matrix while strictly controlling the melt temperature.
Useon Solution: High-Speed Reaction System.
Recommended Machine: SAT Series High-Speed Extruder
- Best Models: SAT65, SAT75, SAT95.
- Speed: Ultra-High RPM (600-900+) provides the necessary shear energy for dynamic vulcanization.
- Configuration: Equipped with precise Liquid Injection Ports for dosing oil extenders and curing agents directly into the process section.
5. PP Recycling & Upcycling
Includes: BOPP Film, Battery Separators, Post-consumer Flakes
The Challenge: Moisture & Bulk Density.
Light, fluffy film scraps bridge in standard hoppers, and moisture or inks in recycled waste lead to bubbles in the final pellets.
Useon Solution: Integrated Degassing & Compaction.
Recommended Machine: SAT Series Recycling Configuration
- Best Models: SAT110, SAT135
- Degassing: Features an Extended L/D (48-52) with Multi-stage Vacuum Degassing (2-3 ports) to completely strip volatiles and solvents.
- Feeding: Integrated with large-volume Side Feeders or Compactor units to force low-bulk-density fluff into the extruder efficiently.
6. Direct Extrusion: XPP Foam & Sheet
Includes: Expanded PP Foam, Thermoforming Sheets, Bio-Composites (PP+Starch)
The Challenge: Melt Stability.
Foaming and sheet extrusion require an extremely stable pressure output and precise temperature control, which standard compounding extruders often struggle to maintain.
Useon Solution: Tandem & Single Screw Technology.
Recommended Machine:
- Best Models: TDD120, TDD150, TDS52/TDD120 Tandem
- For XPP Foam: Tandem Line. The Primary Twin Screw melts and mixes the gas (CO2/N2); the Secondary Single Screw gently cools the melt to preserve cell structure.
- For Sheet: Single Screw (TDD). Uses a grooved feed bush to ensure constant pressure for uniform sheet thickness.
Part 2: The Useon Advantage: Engineered for PP Compounding
Standard extruders often struggle with the specific challenges of PP—such as its tendency to degrade under thermal stress or the difficulty of dispersing high filler loadings. Here is how Useon’s technology makes the difference:
1. High-Torque Gearbox for Maximum Throughput
Processing high-viscosity PP or high-loading masterbatches demands immense power.
- Standard Performance: Our SAT Series features a robust specific torque of 10.3 Nm/cm³, ensuring stable operation for most compounding tasks.
- Ultimate Performance: For the most demanding applications, our U Series (Super High Torque) pushes the limit to 15 Nm/cm³.
This industry-leading torque capability allows for higher screw speeds and throughput rates at lower melt temperatures, preventing the “thermal degradation” common in standard machines and preserving the PP’s mechanical properties.
2. Superior Mixing with Modular Screws
Polypropylene applications vary widely. Our modular screw design allows you to customize the geometry for every job. Use kneading blocks for aggressive dispersive mixing of pigments, or switch to toothed mixing elements for gentle distributive mixing of glass fibers. You get the flexibility of multiple machines in one.
3. Advanced Wear Protection
PP compounding often involves abrasive additives like glass fiber, talc, and calcium carbonate. To extend machine life, Useon barrels are lined with premium bimetallic alloys (Ni-based or Co-based), significantly reducing wear and maintenance downtime compared to standard nitrided steel barrels.
Part 3: Deep Dive – What is Polypropylene?
Polypropylene (PP) is a semi-crystalline thermoplastic polymer belonging to the polyolefin group. It is produced via chain-growth polymerization from the monomer propylene.
It is widely known for its combination of properties: tough, heat-resistant, chemical-resistant, and translucent. It does not present stress-cracking problems and offers excellent electrical insulation.
The Three Main Types of PP
Understanding the molecular structure is crucial for selecting the right resin for your product:
1. Homopolymer Polypropylene (PPH)
- Structure: Contains only propylene monomer in a semi-crystalline solid form.
- Properties: High stiffness, high strength, excellent heat resistance.
- Applications: Textiles, packaging films, pipes, and automotive components.
2. Random Copolymer Polypropylene (PPR)
- Structure: Produced by polymerizing propylene with small amounts of ethene (typically up to 6%).
- Properties: Better transparency, lower melting point, and improved flexibility compared to PPH.
- Applications: High-clarity packaging, medical devices, and hot water pipes.
3. Impact Copolymer (Block Copolymer) (PPB)
- Structure: A heterophasic structure where an ethylene-propylene rubber phase is dispersed within a PP homopolymer matrix.
- Properties: Superior impact strength, even at low temperatures.
- Applications: Heavy-duty industrial parts, automotive bumpers, and luggage.
Key Properties of Polypropylene
- Chemical Resistance: Highly resistant to diluted bases and acids.
- Elasticity: Tough and flexible, making it ideal for “living hinges” (like on flip-top bottles).
- Fatigue Resistance: Retains shape after a lot of torsion or bending.
- Melting Point: Typically ranges from 160°C to 170°C (320°F to 338°F), making it suitable for hot-fill containers.
PP vs. PE (Polyethylene): What’s the Difference?
While both are polyolefins, they have distinct differences:
- PP is stiffer, stronger, and lighter than PE.
- PP has a higher melting point and better heat resistance.
- PE generally has better wear resistance and impact strength at very low temperatures.
FAQs
Yes, PP is 100% recyclable. However, the quality of recycled pellets depends heavily on the extrusion filtration and degassing technology used to remove contaminants like inks and moisture.
For standard compounding, 300-600 RPM is typical. However, for shear-intensive applications like TPV/TPE reactive extrusion, Useon SAT series extruders can run at up to 900 RPM to ensure complete dynamic vulcanization. Conversely, for glass-fiber reinforcement, lower speeds are recommended to preserve fiber length.