milling part P84

P84 moulding powder for high-performance parts

TECAPOWDER P84 HCM grades are used to make high-performance polyimide stock shapes and finished parts. They are heat aged in vacuum so that high quality stock shapes can be moulded without the need for post curing. Large billets can be moulded without cracking. HCM grades are available unreinforced, or with fillers such as graphite powder for compression moulding, or ram-extrusion into stock shapes or direct formed into finished parts.

TECAPOWDER P84 is a fully imidized polyimide with no need for post curing (based on P84® by Evonik).

Outstanding properties

Excellent thermal resistance makes TECAPOWDER P84 HCM parts useful in many markets. Depending on the fillers, the outstanding properties can be customised to suit the application.


TECAPOWDER P84 for speciality markets

TECAPOWDER P84 HCM grades are available in virgin grades and blended grades, custom formulations can be readily made.

TECAPOWDER P84 HCM blends contain various fillers based on the end use application. Graphite filled grades are excellent for bearings or bushings that require high wear resistance, often without lubrication. Glass filled TECAPOWDER P84 HCM is useful in the metal spinning industry. Rollers made with glass fiber filled TECAPOWDER P84 HCM produce a smooth finish on metal parts.

All TECAPOWDER P84 compounds are widely available and custom formulations can be readily made.


Processing Guidelines

  • Hot compression moulding is the sintering of the material at temperatures above the glass transition temperature under a pressure of 35 MPa (5,000 psi). Moulding temperature is 350 °C (662 °F). The necessary equipment is a press which is able to maintain 100 metric tons over a 15 hour cycle, and a top and bottom heated mould with heater-band.

    Example: the production of a 20 cm (8 in) diameter 5 cm (2 in) high billet.

    A suitable release agent is recommended. Before filling the mould, the powder must be dried to eliminate the equilibrium moisture. Drying can be done at 100 °C (219 °F) over 2 hours for a 1.8 kg (4 lb.) loading. At the filling step, the mould should be preheated to 250 °C (480 °F) and the powder should be transferred directly out of the oven into the mould. The first compression up to 17 MPa (2,500 psi) should remove the air from the loading. After this step the heating starts with a ramp up to 300 °C (572 °F). At this temperature the first dwell time with 1 hour is necessary. Then the full pressure of 35 MPa (5,000 psi) is applied and the ramp up to 340 °C (647 °F) starts.

    Moulding cycle hot compression moulding of TECAPOWDER P84

    Reaching this temperature, a dwell time of 4 hours is needed to get uniform heat penetration. At the end of this program a slow cooling ramp starts to reduce temperature within 4 hours down to 250 °C (480 °F) under the full pressure. After reaching this temperature the part should be released.

    Fillers/Reinforcement materials:

    Graphite

    Ensinger tested most available graphite types to choose the best material for TECAPOWDER P84. The following properties are significant for use:

    • For a homogeneously machined surface fine particle size is needed.
    • For high wear resistance, a good incorporation of the graphite in the matrix is needed, the surface morphology is important.
    • For improving the mechanical properties, the particle size of filler should be roughly the same as of matrix-resin, the matrix material must be coating the filler-surface after blending.
    • For blending: the function of blending time and filler-coating is very important. Premixes are necessary.

    PTFE

    To get a uniform matrix and best friction and wear properties the use of very fine PTFE particles is necessary. Also, the melting point of the additive material should be at the same level as the matrix materials Tg.

    MoS2

    The lubrication of MoS2 is based on surface-smoothing through material transfer. In this respect it is very important to have very fine particles as a filler and the right percentage in composition. For being able to process MoS2 at approximately 345 °C (650 °F) Ensinger offers a special grade of TECAPOWDER P84.

  • This process is used to make smaller stock shapes of TECAPOWDER P84 resins. The diameters are limited by the handling possibilities of the moulds. Common mould sizes have outside diameters of 20-25 cm (8-10 in). The moulds have to be able to maintain pressures up to 69 MPa (10.000 psi) at 400 °C (752 °F). This indicates the use of high wall thicknesses and hot working steels to be used for the tools. Sintering can be done in a simple air circulation furnace which can maintain temperatures up to 400 °C (572 °F).

    The following steps will describe how to mould and sinter during this process.

    1. The predried powder over several hours is filled into the mould and compacted for 5 minutes for degassing.
    2. The closed mould is placed in a preheated oven (350 °C (662 °F)) and kept for several hours, depending on the size. After each full hour it has to be taken out and compacted again with 35 MPa (5000 psi) for 5 minutes. Then placed again in the oven.
    3. When the calculated end of the dwell time is reached, the mould is placed in the press, loaded with 55 MPa (8000 psi) and cooled to 250 °C (480 °F). At this temperature the part can be released.

    The calculation for the sintering time (dwell time) should be approximately 1.5 hours/2.5 cm (1 in) wall thickness.

  • This method for moulding finished parts is possible if metal-moulding equipment is available. Changes in mould and feeder are necessary. The mould needs heater cartridges (see drawing) to be able to maintain temperatures up to 250 °C (480 °F). The feeder needs to be heated by oil or electrical heating to maintain temperatures above 200 °C (400 °F). Moulding pressure is approximately 345 MPa (50,000 psi). Dwell times have to be calculated to 30 g/s. The addition of 0,5 to 1 % PTFE (lubricant type) as a release agent is necessary. Ensinger is offering finished blends ready for moulding. Sintering must be done in an oven with nitrogen or inert-gas flow following the temperature curve shown underneath. The sintering causes dimension changes on the moulded parts. In the mould direction they are approximately +10 %, in the cross-mould direction -5 %. The obtained density is approximately 95 % of the hot compression moulded shapes. The mechanical properties obtained are 80% of compression molded values.
    Blended formulations containing graphite, graphite/PTFE, glass/PTFE and molybdenum disulfide are available.

    Sinter cycle for direct moulded parts

    P84 sinter cycle
  • Hot compression moulded or ram extruded P84 can easily be machined to narrow tolerances by using standard metal working equipment. It is recommended to use carbide tooling if a long tool life is particularly important. High-speed steel can also be used for short runs on multiple-point tools.

    When machining TECAPOWDER P84 the following rules should be adhered to:

    • Use the maximum positive rake angle possible and sharp cutting edges.
    • Avoid high cutting pressures and subsequent overheating.
    • Use low feed rates.
    • Plastics have a higher thermal expansion than metals. Allow the workpiece to cool before finishing.
    • Avoid deflection caused by the clamping pressure. It is recommended to use O.D. or 1.D. collets. If a chuck is to be used, provide for soft jaws. A higher number of jaws helps distributing the holding force. Reduce the clamping pressure.
    • Cool the workpiece with air, water or coolant.

    The cutting depth has no influence on the surface quality. In order to achieve very close tolerances, it is recommended to rough turn the part and allow it to cool before finish turning. In case of threading, the depth of feed should be lower than 0,0127 cm (0,005 inch) to prevent the threads from chipping. To avoid chattering deflection of long workpieces with small diameters, it is recommended to support them by means of moving collar.

      Cutting Speed
    Feed 

      feed/min mm/R in/R 
     Rough turning 300-450 0,25-0,5
    0,01-0,02
     Finish turning 450-550 0,05-0,15 0,002-0,006
     Parting 240-300

    0,05-0,08

    0,002-0,003

    Turning

    P84 parts machine easily using standard turning equipment. It is recommended to use carbide-tipped tools. For rough and finish turning operations use a cutting geometry similar to that used for aluminum, for turning on a numerically controlled lathe. The nose radius of the cutting tip should be between 0,1 and 0,2 mm (0,004 and 0,008 in) to guarantee a good surface finish. It is important the cutting tip be level to the center of the piece to be turned. Sharp cutting edges allow high cutting speeds use low feed rates. 

    Lathe tool

    Milling

    TECAPOWDER P84 parts can be machined with all standard HSS or carbide-tipped milling equipment. Multiple-point milling cutters are preferably used. To avoid edge chipping, we recommend the milling be performed from the outside of the block towards the center and use small exit angles. Cutting speed should be between 6,35 and 10 cm/min (2,5 and 4 in/min) and feed rates lower than 0,7-0,15 mm (0,03-0,006 in). The lower the feed rate, the better the surface finish. Lubricating or cooling is not required.

    Conventional milling

    Drilling

    SS drills (point angle 90 °C) or carbide drills (point angle 90-120 °C) can be used to drill holes into P84 parts. If the drill diameter is more than 2 cm (0.8 in), reduce the web thickness. Work at drilling speeds of 2,3-2,8 m/s (450-550 ft/min) and feed rates lower than (0.004 in). To avoid local heating in the workpiece, provide for good chip removal.

    Parting

    TECAPOWDER P84 materials can be cut with circular or band saws. If you use hard metal tipped blades, tool life will be longer. Saw speed for circular saws should be 2-3 m (80-120 in), for band saws 0,3-0,4 m (12-16 in). If plates are to be cut with circular saws, adjust the blade height in such a way that the blade breakthrough is within 2-3 mm (0,08-0,12 in) to the surface to avoid edge chipping.

    Grinding

    P84 parts can be ground to close tolerances with surface grinders used for metal working. Round bars and tubes are ground on centerless grinders. Use double-coated tape to fix the material to the table and cool with water. Table surface speed should be about 0,3 m/s (60 ft/min) for rough grinding and 0,18 m/s (35 ft/min) for finish grinding.

  • For more information please contact [obfemailstart]UDg0QGVuc2luZ2VycGxhc3RpY3MuY29t[obfemailend].

     


Product datasheets, safety documents and certificates

For further information, please contact: [obfemailstart]UDg0QGVuc2luZ2VycGxhc3RpY3MuY29t[obfemailend]