What does Amodel® "PPA" mean?

PPA is the acronym for Polyphtalamide, a semi-crystalline polyamide with aromatic chemical building blocks which provide a unique combination of properties and advantages to the polymer range.

What is the typical color of Amodel® PPA NT grades?

The color of naturally colored Amodel® PPA grades can be described like milky white and depending on the amount and type of filler in the compound, it can vary from off-white to greenish white.

Why does my Amodel® NT part have a different color than it had one year age?

Amodel® parts will absorb moisture over time and depending on the amount it has absorbed, a natural colored NT grade can change in color to a more greenish shade. The color change is a reversible process though and after drying the part, it will return to its initial color under the assumption that the surface has not been oxidized due to the drying process.

Is it possible to color Amodel® PPA grades?

Naturally colored Amodel® PPA products can be colored by means of color masterbatches. Colorbatches with a PA66 carrier for example can be blended at the hopper of the molding machine to result into a colored molded part. It is important however to be aware that the molding process can be influenced by adding such masterbatches and that mechanical properties of the final part can be different than for the original PPA part. Also the color stability will depend on the carrier and pigments that are used in the masterbatch. Colorbatches with a PPA carrier are available on the market which result in a better compatibility with Amodel® PPA resins.

Why do Amodel® PPA grades require different mold temperatures ranging from 80°C up to 160°C – 176°F to 320°F ?

Amodel® PPA compounds are available with different base resins which are based on a different chemical molecule structure. This results into products with different properties, not only for their chemical resistance for example but also for the crystallization speed when transitioning from the molten to the solid phase. Faster crystallizing products don’t require this high mold temperature compared with slower crystallizing grades. The optimum mold temperature therefore depends on the part wall thickness but also on the product type.

Please read our Amodel® processing guide for further detailed information about molding Amodel® resins, and the technical data sheets for detailed information of each grade.

How can I dissolve a Amodel® PPA part?

PPA compounds can be dissolved in several solvents like m-Cresol or P-TCE (60/40 Phenol / 1,1,2,2 Tetra-Chlor-Ethane) which are described in the ISO 307 or ASTM D2857 or D5225 norms for determining solution viscosities of polymers. Due to the hazardousness of these solvents, also very strong acids like highly concentrated sulphuric acid or formic acid are frequently used for dissolving PPA resins.

How can I obtain Amodel® PPA resin pellet and molded samples for testing purposes?

Samples pellets for molding trials and several shapes of molded articles can be supplied for testing purposes. There is a wide range of products and sample types available. Stock shapes or other thick walled semi-fabricates for machining prototype parts for example, are not offered due to the complexity of the practical aspects to cool such parts fast enough and prevail the material from being degraded at the inner core of thick sections.

What is crucial for molding Amodel® PPA parts?

Molding Amodel® PPA parts requires a couple of basic preparations and equipment which are key to the quality of molded parts. Proper measures need to be taken related to drying the resin and keeping it dry before processing, as well as selecting a suitable size of the molding machine with respect to the shot volume and the total residence time of the polymer in the machine. A frequently underestimated aspect is the tool design and venting aspects, which should be big enough machined in order to obtain a long maintenance and cleaning interval of the tool.

Please read our Amodel® processing guide for further detailed information about molding Amodel® resins.

Why do I need to dry Amodel® PPA resins before processing?

Amodel® PPA resins need to be dried before they are processed. The Amodel® resins are processed at an elevated temperature which is close to its degradation limit and slight amounts of moisture at this high temperature, lead to a hydrolysis reaction (polymer chain scission) which results into a loss of mechanical properties. Besides the influence on the mechanical performance, it also has an effect on the generation of volatile components which sublimate onto the surface leading to mold & vent deposits in the tool.

Please read our Amodel® processing guide for further detailed information about molding Amodel® resins, and the technical data sheet for detailed information of each grade.

What can I do to reduce the mold deposits, if any, in my tool?

To avoid and reduce the formation of mold deposits in the tool and tool vents, it is recommended to sufficiently dry the resin according to the product recommendations and to apply sufficiently large and well-designed vents. Also the recommended melt temperature as indicated on the product datasheet should be taken into account.

Please read our Amodel® processing guide for further details on vent design and dimensions.

How and when should I purge the barrel and screw?

To avoid excessive degradation of Amodel® PPA resins, it is recommended to purge the screw and barrel of the molding machine if an interruption of several minutes occurs. For short interruptions or standstills of the molding machine, a purge of the screw is sufficient. For longer interruptions or material switchovers, a purging cycle with a cleaning agent is recommended.

Further details related to the purging procedures can be found in the Amodel® processing guide under the “Purging” section.

Are there any food or water contact approved Amodel® PPA grades?

Solvay Specialty Polymers has developed Amodel® compounds with fillers and additives that are suitable to match several food and water contact regulations.

For more information, consult the technical data sheets of DW and FC grades.

Is it possible to use Amodel® PPA with hot runner systems?

The use of high temperature engineering polymers in combination with hot runner systems requires some special attention with respect to the material residence time and thermal house holding of the hot runner system. It's best to consult one of our Specialty Polymers experts. 

Is there data existing for simulation software?

A series of Amodel® PPA grades are characterized to be able to make rheological and mechanical analyses of injection molded parts. Data is openly available in most of the commercial rheological software (Moldflow, Moldex, CADFlow...). Many Digimat data as well as stress-strain curves can be obtained.

Are Amodel ® PPA resins suitable for parts with undercuts and a forced ejection from the tool?

Solvay Specialty Polymers has a range of products which is particularly suited for such forced ejections from the tool. By taking specific design recommendations into account, it is possible to eject the part from the tool without a failure or complete deformation of the part, which is frequently required for automotive applications.