Masterbatches for pipe and profile extrusion

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Pipe and profile extrusion

We actively collaborate with the Client throughout all stages of the process to resolve defects and improve productivity. We work closely to develop solutions that do not interfere with process conditions, exploring alternative additives and materials together that can address the primary causes of defects. The result is a synergy that significantly reduces waste and develops value in innovation starting from the expertise of both parties.

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Phase one

1. Material preparation and dosing

The raw material (granules, powders, or regrind) is stored, dried if necessary (for hygroscopic polymers such as PA, PC, PET), and dosed via volumetric or gravimetric systems. The Masterbatch is dosed in the same phase in percentages typically ranging between 1% and 5%. In this phase, the three essential conditions to monitor are:

Residual moisture verified and below the polymer limits (for potentially hygroscopic raw materials).

Gravimetric dosing of the Masterbatch with high precision to ensure colorimetric repeatability.

Separation of regrind batches and qualification of the MFI before use in production.

Phase two

2. Extrusion

The dosed material enters the hopper and is conveyed by the screw into the melting zone (barrel). The temperature profile of the barrel is divided into zones plus the extrusion head. The molten polymer is homogenized and pushed toward the die at constant pressure and flow rate. In this phase, the stability of the flow rate and pressure at the head is fundamental for the dimensional consistency of the profile. Variations in the thermal profile, wear of the screw and/or barrel, and the presence of material stagnation areas cause localized degradation, color streaks, and dimensional instability. In this phase, it is essential to manage:

A screw temperature profile optimized for the polymer being processed.

Head pressure so that it remains stable with minimal variations during production.

Maintenance of the screw and barrel so they are free of significant wear.

The main critical elements of this phase are:

Polymer speed

Polymer shear rate in the screw, which influences viscosity and frictional heat and is correlated to the plant’s flow rate.

Melt pressure

Melt pressure at the head, an indicator of process stability, must be constantly monitored.

Residence time

Residence time of the polymer in the screw, which is correlated to the risk of polymer degradation with consequent loss of aesthetic and mechanical performance.

Stagnation zones

Material stagnation zones in the screw or head where degraded polymer accumulates.

L/D technical ratio

The length/diameter ratio of the screw influences the plasticization and mixing of the recipe’s constituent components.

Instability of the extrusion flow rate with cyclic pressure oscillations.

Residence time of the polymer in the screw, which is correlated to the risk of polymer degradation with consequent loss of aesthetic and mechanical performance.

Phase three

3. Shaping through the die

The molten polymer passes through the die, which defines its cross-sectional profile. For pipes, a head with a mandrel is used, and calibration begins right in the die. The die design must ensure a balanced and uniform flow across the entire section. In this phase, flow imbalance in the die generates differential thicknesses, bow (profile curvature), and geometric deformations. Die swell (swelling of the melt at the exit) must be accounted for in the die design. Non-uniform temperatures in different zones of the die cause differential flow speeds. In this phase, the three optimal conditions to manage are:

Die designed with computerized rheological analysis (FEM/CFD) to ensure balanced flow.

Uniform die temperature across the entire section with localized heaters and dedicated thermoregulators.

Land length optimized for the polymer and profile geometry, with the possibility of fine adjustment (lip adjustment).

In process management, elements requiring attention are:

Melt swell

The swelling of the melt upon exiting the die is an elastic effect of the polymer and depends on temperature and flow rate.

Flow balancing

Flow balancing in the die is used to obtain uniform thicknesses on asymmetrical profiles.

Die length

The length of the final straight section of the die, along with temperature and flow rate, influences die swell and flow stability.

Weld line

The melt weld line that forms downstream of the mandrel in pipes is a potential weak point of the product.

Flow instability

Irregular flow with an orange-peel surface appearance due to excessive shear rates.

Phase four

4. Calibration and cooling

The profile/pipe exiting the die passes through a calibrator (vacuum-based for pipes) or a cooling bath that sets its dimensions. For complex profiles, dry calibrators with a controlled vacuum gauge are used. Cooling takes place in water tanks or with mist nozzles. The draw ratio between the extrusion speed and the haul-off speed determines the molecular orientation and final thickness. Residual stresses from non-uniform cooling cause post-process deformations. For pipes, dimensional tolerances (outer diameter, thickness) are regulated by strict standards. In this phase, the three essential conditions to keep under control are:

Haul-off speed synchronized with the extrusion flow rate to maintain the draw ratio within the optimal range.

Constant and uniform cooling water temperature to avoid asymmetrical residual stresses.

In-line thickness monitoring with ultrasonic sensors and an automatic feedback system.

In this final phase, the critical issues to manage are:

Draw ratio

The DR has an effect on molecular orientation and consequently on mechanical properties.

Vacuum management

In the specific case of pipes, vacuum calibration is fundamental for continuous vacuum control.

Ovalization

Ovalization of the pipe can occur due to non-uniform cooling or insufficient calibration pressure.

Thickness variation

Thickness variation along the circumference of the pipe must be monitored, often with an ultrasonic system.

Phase five

5. Thickness adjustment and cutting

Through automatic feedback loops, any dimensional deviations are corrected by adjusting the haul-off speed or the extruder pump flow rate. The profile/pipe is then cut to the nominal length with orbital blade cutters or saws. Cutting tolerance affects downstream assembly operations. Hot cutting causes burrs and deformations. In-line measurement systems must be calibrated periodically. Slow process drift requires frequent adjustments. In this phase, the three winning technologies are:

The in-line measurement system with adequate sampling frequency and controlled calibration.

Automatic feedback acting on haul-off speed and/or flow rate for real-time correction of deviations.

The cold cutting system with sharp tools to ensure flat and burr-free cutting surfaces.

In this final phase, the strategic steps are:

Closed-loop control

Automatic feedback control system for profile dimensions.

Measurement

Non-contact in-line measurement systems for diameter and thickness.

Markets

Markets for profile and pipe extrusion

Success in profile and pipe extrusion is based on the ability to respond to the specific needs of each sector. Solutions capable of guaranteeing high productivity, dimensional stability, and regulatory compliance stem from an engineered approach, calibrated to the specific final application – from melt viscosity management to geometric precision, from resistance to external agents to compatibility with industry standards. Our expertise and specialized products are at the service of your most critical needs across a wide range of high-tech and regulated industrial sectors.

Products

Product line for profile and pipe extrusion

Rifra works alongside processors who produce profiles and pipes for technical, industrial, and regulated applications, where process continuity, geometric precision, and performance stability are essential conditions. Deep knowledge of the typical criticalities of this technology allows for the development of color Masterbatches and additives that do not merely satisfy aesthetic or functional requirements but contribute directly to process regularity and the final quality of the product. Each solution is designed to optimize productivity, dimensional reliability, and performance over time, with constant attention to sustainability and the circular economy.

Color Masterbatches

Our design rules for color formulations

Rifra has always chosen not to focus on the production of standard formulas, but on ad hoc developments that maximize color performance and enhance the product in its specific intended use. In profile and pipe extrusion, the formulation of the color Masterbatch is not a simple chromatic choice, but a technical intervention that must integrate with the entire rheological and thermal balance of the process. Pigment dispersion, compatibility with the polymer matrix, thermal stability during residence time, and the absence of interference with calibration, flow, and surface finish are determining factors for ensuring consistent quality and repeatability of the result.

Regulated and high-performance sectors	Values for manufactured products	How to obtain value from Rifra formulas
Automotive	Profiles for gaskets, cable sheaths, technical pipes for vehicles. Resistance to oils, onboard fluids, thermal shocks, and vibrations.	REACH and RoHS compliant pigments. High thermal stability. Formulations validated not to alter the mechanical properties of the polymer and to ensure performance even at high temperatures.
Electrical / Electronic	Cable ducts, cable sheaths, corrugated pipes for protecting electrical and fiber optic cables. Mandatory IEC color codes, FR resistance.	Correspondence with IEC 60446 color codes. Process-compatible FR formulations. UV stability for outdoor installations.
Medical	Medical tubes, device sheaths, profiles for hygienic environments. Chemical purity, absence of migration, regulatory compliance.	Rigorous selection of raw materials with guaranteed traceability for every formulation.

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Sectors with high aesthetic impact and durability	Value for manufactured goods	How to obtain value from Rifra formulas
Indoor furniture	Decorative profiles for furniture, edges, handles, strips. High aesthetic quality required with chromatic consistency from batch to batch.	Metamerism control. High pigment dispersibility for glossy extrusion surfaces free of streaks.
Outdoor furniture	Window and door profiles. High aesthetic quality and resistance to light and weathering.	Accurate selection of outdoor pigmentations, with the possibility of complex formulations with specific anti-UV and antioxidant agents.

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Specialized high-stress sectors	Value for manufactured goods	How to obtain value from Rifra formulas
Agriculture	Drip and sprinkler irrigation pipes, fertigation pipes. Profiles for greenhouses and tunnels. Multi-season open-field products.	High outdoor color fastness. Balanced UV/HALS based on the base polymer (PE, PP). Formulations with carbon black for black pipes.
Construction	Pipes for drinking water, gas, drains, and rainwater. Profiles for windows and doors, thresholds, windowsills, technical profiles for insulation and roofing.	Formulations that do not alter melt viscosity, ensuring dimensional stability of the profile. Thermostable pigments for process temperatures.

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Additive Masterbatches

Our long-standing additive solutions

When it is necessary to provide the product with specific characteristics, Rifra studies dedicated solutions by collaborating with active ingredient suppliers and verifying with Clients the best balance between the amount of active ingredient in the finished product and the desired performance.

Value for manufactured products	Benefits for the process	Properties
Profile with constant section and uniform thickness without undulations.	The rheology modifier stabilizes melt viscosity in the flat die, reducing flow variations and the surging phenomenon that causes dimensional oscillations.	RHEOLOGY MODIFIER PROCESS AID (PPA)
Profile with a smooth, glossy surface free of melt fracture defects.	The PPA forms a lubricating film on the metal surfaces of the die, reducing operating pressure and temperature, and drastically extending cleaning times.	PROCESS AID ADDITIVE (PPA)
Pipe or profile with mechanical resistance preserved after extrusion.	Antioxidant protection prevents thermal degradation of the polymer during its stay in the barrel and head, maintaining molecular weight and long-term properties.	ANTIOXIDANT
Outdoor profile with stable color and mechanical properties preserved over time.	The appropriate selection of UV absorbers and HALS minimizes die build-up from stabilizer condensation on the die lips and ensures long-term solar protection.	UV STABILIZER HALS
Pipe with optimal internal flow properties (low internal roughness).	The addition of internal slips reduces the friction coefficient of the internal pipe wall, improving hydraulic flow rate at the same pressure.	INTERNAL SLIP AGENT
Flame retardant profile with fire reaction classification.	The compatibility of the FR system with lubricants and stabilizers avoids compromising the process window and surface quality.	FLAME RETARDANT SYSTEM
Pipe or profile with antistatic characteristics.	The dissipative antistatic system eliminates electrostatic charges during the profile’s advancement in the calibrator, reducing dust attraction and electrical risks.	ANTISTATIC

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Complex Masterbatches

Our best formulations: the COMPLEX range

As in all well-made things, the best result is achieved by working as a team. Rifra translates this motto into a preference for solutions that combine color formulation with the most high-performance chemistries, providing “all-in-one” additivated structures directly in the plant.

Rifra solutions	Synergistic advantage	Guaranteed efficiency
RIFRACHEM CX PPA + ANTIOX	Colored profile with a perfectly smooth surface and non-degraded polymer. The PPA reduces die pressure and die build-up; the antioxidant protects the polymer from thermal degradation in the barrel.	Reduction in downtime for die cleaning, maintenance of lot-to-lot MFI, surface free of melt fracture defects.
RIFRACHEM CX PPA + UV	Colored profile for outdoor use with a smooth surface and integrated solar protection. The PPA/UV synergy ensures both extrusion quality and the durability of mechanical properties in external environments.	High aesthetic quality surfaces without additional interventions. Outdoor color stability for windows, facade profiles, and agricultural profiles.
RIFRACHEM CX ANTIOX + UV	Colored pipe or profile with double protection: thermal during processing and solar during use. Formulation studied for every polymer combination on products with long-term aging requirements.	Maintenance of mechanical properties after accelerated aging. Validated solution for outdoor use.
RIFRACHEM CX FR + PPA	Profile additivated with flame retardant agents with an optimal extrusion surface. FR/PPA compatibility prevents the flame retardant load from increasing die pressure and generating surface defects.	Fire reaction classification maintained without sacrificing aesthetic quality. Reduction of machine downtime for cleaning even with high-load FR formulations.
RIFRACHEM CX ANTISTATIC + PPA	Profile or sheath with a smooth surface and controlled surface resistivity. The combination eliminates charges during calibration and ensures the continuity of the antistatic function across the entire extruded surface.	Stable surface resistivity. No surface defects from antistatic/die interaction. Ideal for cable ducts and cable sheaths.

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