Processing Rilsan® PA11
Rilsan® PA11 processes very well in each of the major thermoplastic processing technologies thanks to a wide range of viscosities.
- Injection molding
- Extrusion (e.g. cast film, blown film, sheet, tube, blow molding)
- Assembly process (e.g. overmolding, coextrusion)
- 3D printing
Storage & handling
For unopened bags, resin is ready-to-use without re-drying.
- Storage temperature should be less than 40-50ºC and avoid high humidity
- Store bags in the workshop 24 hours prior to processing to avoid condensation
- Shelf life is 2 years from the date of delivery
- Avoid using pellets from bags that have been open for longer than 2 hours
- Manually close the bags after feeding the hopper to avoid moisture uptake
- After a one-day trial, reseal the bag before re-using the next day
Pellets exposed to atmospheric conditions for more than 2 hours should be dried before processing.
Place the granules onto a clean flat metallic tray for efficient drying. Arkema highly recommends using vacuum drying ovens because the absence of oxygen allows for higher temperatures which saves time. Desiccant dryers are also efficient with regularly changed filters. Risk of oxidation is increased with forced-air circulation ovens. Raising the temperature above recommended parameters does not significantly reduce drying time and can also increase the risk of oxidation.
Recommended parameters: 4—8 hours at 80—90ºC
The rheological behavior of Rilsan® polyamide 11 allows for:
- A wide range of processing temperatures compared to other thermoplastic elastomers
- Ability to inject extremely thin parts
- Short cycle times
- High recyclability
- Accurate dimension control
- Screw: Standard 3 zone with a non-return valve
- Injection nozzle: Shut-off nozzles
- Compression rate: ≥ 2.5
- L/D: ≥ 15
Injection molding conditions
Melt temperature (ºC):
Whichever Rilsan® PA11 grade is used, the temperature should rise from the upstream feed zone to the downstream zone to produce a sufficiently homogeneous melt.
*The outstanding thermal stability of Rilsan® PA11 allows much higher temperatures to be used (up to 300°C). However, these temperature levels should be used only when needed.
Mold temperature (ºC):
The use of temperature-regulated tooling is highly recommended for the injection molding of Rilsan® PA11. By controlling mold temperatures, one can affect the appearance of the finished article, the ease of filling, mold release, and shrinkage.
Except for a few specific cases, non-glassfiber-reinforced Rilsan® PA11 grades require cold molds (30 – 40°C). However, when injection molding thin-walled articles, or with large surface areas or intricate shapes, higher temperatures can be used to fill the mold cavity more easily.
Glass fiber-reinforced grades require hot molds (90 – 100°C) to produce an even
and glossy surface finish.
The specific temperature profile required can vary considerably from one machine to another. The following information is therefore given as an indication. It will also depend on the extrusion speed and the specific Rilsan® PA11 grade chosen, i.e whether lubricated or not. For example, non-lubricated grades require higher temperatures, especially in the first zone of the extruder.
Melt temperature (°C):
|Hopper||Feeding Zone||Compression Zone||Metering Zone||Extrusion Head||Die|
|BESNO P40 TL||60||175||220||235||230||220|
|BESNO P20 TL||60||180||225||240||230||220|
Extrusion (film & pipe)
For extrusion, it is essential to use Rilsan® PA11 granules with a moisture level below 0.1%, to prevent bubbles and other defects in the wall section, and to ensure a steady feed of the granules and a constant mechanical energy absorbed by the material.
Screw: functions and profiles
Screws suitable for the processing of Rilsan® PA11 should fulfill the following
- Consistent feed of granules
- Efficient melting and de-gassing of the product
- Excellent homogenization of the melt through sufficient back-pressure
Screws with a long compression zone help minimize variations in the pressure
reached at the end of this zone and any resulting variations in the flow rate.
Together with the compression rate, the clearance between the screw and the barrel
is the most important parameter when choosing the right screw for Rilsan® PA11.
The extrusion of Rilsan® PA11 tubing requires a water tank whose two main functions are to form the shape of the tube in a calibrator under vacuum and to efficiently cool the pipe through continuously circulating water in the tank. The level of vacuum can be varied from 50 to 400 mbars and is used to adjust the outer diameter of the tube. Rilsan® PA11 features unique extrusion properties compared to PA12, due to its viscosity kick during the extrusion process. This is a key benefit for large diameter extrusion, where its melt strength is a real advantage.
The rheological properties (fluidity) of Rilsan® PA11 make it suitable for applications
using the rotomolding technique and in particular the manufacture of articles which
include metal inserts.
Rotational molding does not induce residual stress in the material such as that found
in injection molded articles. This is because during the rotomolding process, the material is not subjected to the intense mixing and compacting experienced in an extrusion screw or an injection molding machine. Rotomolding is also much more suitable for parts with larger dimensions than injection molding.
The rotomolding of specific Rilsan® PA11 grades requires molds of a traditional construction (e.g. steel, aluminum, copper plate) and it is important for vents to be present. Although removing finished Rilsan® PA11 parts from the mold is easy, it is advisable, where problems do occur, to treat the surface of the mold cavity, either by applying a fluorinated coating or a thermoset varnish or by spraying the walls of the mold cavity with silicone or other similar products.
To achieve optimum molding of Rilsan® PA11 parts, it is preferable to heat the
product to between 260°C and 300°C. The duration of the heating is governed by the temperature of the oven, the thickness and thermal conductivity of the mold, and the desired wall thickness of the final part.
The mold rotation speed along the two axes is based on the dimensions and design of the mold. The choice of these parameters governs the consistency of the material thickness. They should be determined on a case-by-case basis.
Cooling conforms to the same parameters as heating time (temperature of air and water, thermal conductivity and thickness of the mold). In order to prevent distortion or surface defects on the articles, the temperature should not be allowed to drop too quickly in the first phase. For this reason, preliminary cooling with air is advisable. An air-water-air cooling cycle generally gives the best results. Additionally, it ensures longer life for the molds by preventing excessively sudden thermal shocks.
Coloration, machining, recycling, ...
For more information about coloration, machining, recycling, bonding, welding, or any other processing techniques for Rilsan® PA11 download our comprehensive brochure and/or contact our team of experts today.