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A capillary rheometer is used to measure a material's flow properties at high shear rates. The results can be used for both material development and to predict a suitable processing window in extrusion, injection moulding, or fibre spinning.

Capillary rheometry is relevant for anyone interested to evaluate and/or develop polymeric materials for processing in the melt or in high viscosity solution.

In a capillary rheometer, the material is placed in a cylindrical chamber to be extruded through a smaller capillary, while measuring the inlet pressure. The temperature in the chamber can vary from room temperature to 300°C, and possible shear rates range from 0.1 s-1 to 100,000 s-1.

Our Netzsch Rosand RH10 rheometer has two parallel cylinders and is equipped with haul-off, so that besides viscosity, it can measure melt strength as a function of take-up speed.

Approximately 100 grams of material are required for a test.

The instrument is suitable for testing according to ISO 11443.

Report containing:

• Viscosity curves as a function of shear rate and temperature.

• Melt strength as a function of extrusion and collection speed.

A small amount of collected filament on a spool, during melt strength testing.

ISO 11443

Man-made fibers produced using solution spinning are collected and processed as filament or staple fibers depending on the desired application. RISE has equipment and knowledge to develop these two types of fibers that can be further converted into yarns and threads.

Solution spinning of fibers results in tows, in other words bundles of multiple fibers packed in the longitudinal direction. The number of fibers in the tow is determined by the number of capillaries in the spinnerets used for extrusion. The tow is processes throughout coagulation, washing, stretching, spin finish application, drying, where fibers stay packed together, as extruding single fibers is not economically feasible. Depending on the intended application, the tow can be processed as filament or staple fibers, suitable for yarn and thread manufacturing.

We perform research trials aimed at the development of both filament and staple fibers.

Filament fibers

Filaments are continuous and unbroken fibers that can be used in their original form as they emerge from solution spinning or can be twisted to form yarns and threads. The number of fibers in filament yarn is determined by the number of spinneret capillaries employed during the dope extrusion. 

Staple fibers

Filaments can be transformed into staple fibers using a cutting operation. Typically, crimping is also performed to aid in the yarn spinning process by creating interlocking points for the fibers to grip onto each other. Moreover, spin finish plays a crucial role in yarn spinning of staple fibers and thus requires careful optimization. When aiming for staple fibers, the number of spinneret capillaries used for extrusion is not restricted by the yarn thickness, allowing for solution spinning of very thick tow. The tow can be cut into staples and used for yarn spinning, with yarn thickness subsequently controlled through such operations as carding, drawing, roving, and ring or open-end spinning.

Characterization of fibers

We perform the following testing of fibers:

• Mechanical testing (e.g. dry and wet tenacity).
• Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS).
• Degree of polymer orientation (birefringence).
• Specific surface area (BET).
• Crystallinity (CP/MAS NMR and SAXS/WAXS).

We have knowledge and equipment to develop and optimize solution spinning processes to produce filament and staple fibers, yarns and threads. Deliverables may include optimized process parameters summarized in a report or actually produced fibers. Please contact us for more information.

Air-gap (dry-jet wet) spinning is a method used for man-made fiber production. In this method, a polymer solution is extruded through a spinneret and travels through an air gap before entering the coagulation bath. Air gap allows better polymer orientation prior to its solidification compared to wet spinning, resulting in higher fiber strength.

We offer trials at bench- or laboratory-scale, enabling the development of air-gap spinning process. The trials can include exploring new polymer solvents, raw materials, and production techniques.

With our expertise and know-how, we conduct research trials, enabling feasibility studies for air-gap spinning process development.

Bench-scale equipment for air-gap spinning:

• Two lines for air-gap spinning.
• Flexible equipment with possibilities of inline coagulation, stretching and washing, spin finish application, drying and winding.
• A library of spinnerets with different number of holes, hole diameters, L/D etc.
• Dope volumes: from 15 mL to 350 mL.
• Capacity: 1-50 g dry fiber per day.

Our goal is to provide air-gap spinning services that serve the specific needs of each customer. Deliverables may include optimized process parameters summarized in a report or actually produced fibers with specific properties. For further details, please feel free to reach out to us.

An essential step in solution spinning is the development of spinning dopes (polymer solutions) with optimal properties. Precise control over dope properties is essential for ensuring proper extrusion and coagulation, thereby laying the foundation for a well-functioning solution spinning process for man-made fiber production.

Spinning dope is a homogeneous solution made from a polymer dissolved in a solvent. The polymer can originate not only from virgin raw materials but also from polymer fractions for example to be extracted during textile recycling. The composition of spinning dope, molecular weight of the polymer, polymer concentration, dope temperature etc. can be tuned to allow polymer dissolution while limiting its degradation and providing reasonable dope properties, such as viscosity and storage stability. Getting right dope properties is crucial for enabling correct extrusion of filaments through spinneret capillaries into the coagulation bath, especially when multifilament spinning is required. There are also great opportunities to add functionality to the wet-spun fibers through targeted dope formulations.

We develop spinning dopes suitable for multifilament solution spinning. Our capabilities include:

• Equipment for polymer dissolution in different scales, including reactors, kneaders and high-shear mixers.
• Filtration in various scales.
• Deaeration.

We characterize dopes using methods such as:

• Filterability.
• Rheology.
• Microscopy.
• Particle analysis.
• Polymer dissolution state and solvent-polymer interactions using SAXS/ WAXS.

Please contact us for more information for the delivery time and price.