Mitsubishi Engineering-Plastics's XANTAR® Polycarbonate is a versatile thermoplastic resin that is suitable for a wide range of applications and can be converted using all common melt-processing techniques.
Blending of XANTAR® polycarbonate with ABS has a variety of effects on the properties of the blend, resulting in a new class of XANTAR® C materials, that incorporates specially developed high purity ABS and offers an improved property profile compared to other PC/ABS blends. One of the synergetic effects is for instance the lower melt viscosity under typical injection moulding conditions.

To ensure the translation from optimal material choice to optimal product, adequate processing is essential. XANTAR® Polycarbonate & Blends can be easily processed using standard processing equipment. There are several factors however that can affect the outcome of the processing, which comprise for instance:

  • Pre-drying
  • Machine layout
  • Processing conditions
  • Secondary operations

Please consult the Additional Information in the menu to the left for further detailed information on each topic.
In case of any question or issue, please do not hesitate to contact your local Account or Technical representative or our Technical Centre for further assistence.

Processing guidelines of each XANTAR® grade can be found via the Quicklink on the left.
Select the right grade, and subsequently select the Injection Molding Recommendations in the General / Processing tabs as indicated:


XANTAR® polycarbonate can absorb moisture from ambient air. The moisture content of the granulate should be kept below 0.03% to prevent hydrolytic decomposition during processing.

XANTAR® grades should be pre-dried at the temperature indicated in the processing guidelines of the respective grade, either in a vacuum dryer or in an air-circulation oven. In the latter case, the granulate should be spread out on trays to a maximum thickness of 3 cm. The drying time as indicated should be followed. In general, drying times should not exceed the recommended drying times largely, because part performance may be lowered.

Typical drying time for XANTAR® and XANTAR® C grades is 4 hours. XANTAR® E requires typically 6 hours. The exact drying temperature varies per grade, and typically ranges from 90-120°C.
For impact modified PC grades, Xantar® LDS, Xantar® XRM and other specialties, different drying conditions may however apply.

Please observe that the values depicted here are purely indicative. Always consult the corresponding processing guideline of the particular grade you are using.

To prevent the granulate from reabsorbing moisture, fill the hopper with an amount of material sufficient for a maximum of 20 to 30 minutes production only. The hopper should be closed at all times to prevent reabsorption of moisture. Alternatively, a hopper dryer can be used.


XANTAR® can be processed on conventional injection moulding machines. A low compression screw is recommended with:

  • a L/D ratio of 20:1,
  • a compression ratio of 1:2 to 1:2.5,
  • a sliding ring check on the screw tip

Before starting production it is important to clean the plasticizing equipment properly. At the processing temperature of polycarbonate most thermoplastics decompose. Insufficiently cleaned machinery may result in delamination, black specks, or even degradation, and the mechanical properties of the article is likely to be influenced negatively.

An open nozzle is preferred to minimize resistance to the melt flow. However, if drooling occurs, the temperature of the nozzle should be lowered to 10°C below the temperature of the preceding cylinder zone. Drooling can also be prevented by decompression at the end of the plasticizing cycle. Grooved feeding zones in the barrel or mixing elements on the screw shall not be used.

Optimum injection moulding results have been obtained using the machine settings and instructions listed below:

  • Effective injection pressure: 1000 - 1800 bar
  • Hydraulic back pressure: 5 - 10 bar
  • Holding pressure: 50 - 70 % of injection pressure
  • Shot weight: 50 - 80 % of maximum cylinder volume
  • Injection speed: medium to high

Please observe that the values depicted here are purely indicative. Reality may require deviations from these settings. Please do not hesitate to consult our Technical Centre for further assistence with respect to the processing conditions of XANTAR® Polycarbonate & Blends.


Melt temperatures

Please observe the temperature settings as given in the Processing Guidelines. Generally, the barrel profile temperature settings increase gradually going from the hopper/back to the front, with slightly decreased temperature at the nozzle again. The actual melt temperature should, under normal conditions, not exceed the maximum indicated. If restrictions in part design require a higher melt temperature, the temperature may be slightly increased providing the residence time is kept as short as possible. If the melt temperature and residence time are kept in balance, no material degradation or colour changes will occur.

Mold temperature

Mold temperatures between 50 and 120°C are recommended, see Processing Guidelines for each grade for more details. Higher mould temperatures help to improve surface appearance, aid mould release and, in addition, reduce any residual mould-in stresses.
XANTAR® Polycarbonate & Blends can be effortlessly combined with hot & cool technology, MuCell technology and used with thermal blowing agents for structural foam.

Plasticizing time

The plasticizing time should be as long as the required cooling time will allow, to keep the screw speed low and thus minimize heat due to friction.


The melt cushion should be set in such a way that only a small amount of material (typically 2-6mm) remains in the cylinder in front of the screw tip after injection.


Production interruption

If processing is temporarily interrupted, the plastisizing unit should be emptied and the screw placed in the forward position. Cylinder temperatures must be lowered to 180-200°C to prevent decomposition of the remaining material. Before restarting production, raise the cylinder temperatures to normal and purge the cylinder.

Production stop

Polycarbonate can adhere so strongly to metal surfaces, when cooling below 160°C, that metal particles may be loosened from the surface during a following plasticizing process. The plasticizing unit should therefore never be shut down with Xantar® remaining in the unit. A thorough purge prior to shut down is absolutely necessary.


After the production cycle has been completed the plasticizing unit is emptied, followed by a purge with high viscosity HDPE at temperature settings used during the previous production run. The cleaning process is completed when the melt leaving the machine nozzle is clear. In severe cases of contamination, variations in temperature settings as well as screw revolutions can be used to improve the cleaning process. Only in extreme cases it may be necessary to take the plasticizing unit apart to complete the cleaning operation manually.


Despite optimal material choice and optimal processing, processing issues may still occur. Possible causes of three of the most common problems encountered whilst moulding polycarbonate are discussed below:


Material discolouration (yellowish brown tint in transparent material, and/or black speck contamination) are usually caused by material degradation. Common causes are dead spots, too long residence time or tailing, too high temperature settings, too high screw- and/or injection speed. Moisture content of the material should also be investigated.

Bubbles or voids

Bubbles are usually an indication of moisture in the material. Moisture bubbles show most clearly during purging or moulding without holding pressure. Material drying temperature and time should be investigated (check moisture content).

Alternatively, bubble-like inclusions sometimes occur in thick sections caused by voiding as a result of shrinkage. This is an intrinsic phenomenon of plastics, and will naturally be easier observed in transparent materials. The problem is NOT related to the shape of the granulate. When voids occur in the molded part, molding conditions/design should be checked. Usually, optimization of the switch over point and/or optimization of the holding pressure will resolve this issue.


Streaks are usually the result of material decomposition due to overheating. This may be caused by too high melt temperature, high screw speed, too high (local) shear rate (injection speed) or a non-optimal gating system. Moisture content of the material should also be investigated. In general, PC/ABS is more sensitive to streaks due to the aforementioned facors. Do not hesitate to consult the Technical Centre for discussing the most optimal settings for your configuration.


XANTAR® polycarbonate is suitable for a wide range of applications and can be converted using all common processing techniques including extrusion. The XANTAR® product line consists of both general purpose grades and special grades for extrusion, such as high viscosity polycarbonate extrusion grades, especially developed for twin wall sheet. They contain an additive system that is tuned for easy and smooth calibration and has a UV-stabilisation system to provide a good weatherability performance.


XANTAR® polycarbonate can be processed on single screw as well as on twin screw extruders. When twin screw extruders are used, only co-rotating screws are suitable. Because of the high melt viscosity of polycarbonate, starve feeding might be necessary.

Screw design

For a normal three zone extruder below mentioned values are valid. To improve the output consistency, sometimes melt pumps are used.

  • Transport zone: 6-10 D
  • Compression zone: 3-8 D
  • Metering zone: 4-7 D
  • Total: 20-25 D

Normal compression ration is appr.1 : 2.5.



As in general for PC, predrying is necessary: 4 hours at 120°C. However when a devolatilisation section is installed, predrying does not have to be carried out, dependent on the devolatilisation efficiency.

Normal temperature settings are between 270 and 300°C, with somewhat lower settings at the feeding section. The die can also be set towards somewhat lower settings (250°C) to obtain enough melt strength and to avoid too much adhesion to the calibration unit. The melt temperature should not be above 300°C to prevent degradation of the polymer.

Shut down procedure

In order to prevent damage to the screw, the temperature should not pass below 180°C. In case of shut down, cleaning is advised with HDPE or PP, starting at 180 °C and then at lower temperatures with HDPE.

EXTRUDING XANTAR®: Calibration techniques

The quality of the extruded profile or sheet depends on the selection of the correct calibrating technique. The length of the calibration unit, its surface quality and the cooling technique applied are of particular importance. With indirect cooling and small wall thickness profiles (< 1.5 mm) it can be assumed that calibration is completed after a contact length of about 150 to 300 mm in the calibration unit. High take-off rates have a favourable effect on the surface in profile extrusion, they should be above 2 m/min.

For simple geometry profiles (rectangular, triangular or round), the sizing technique used is vacuum quench tank calibration. Intensive cooling is obtained by direct water cooling. A water film is formed between the calibration discs and the profile. This film protects the surface from scratching by the unit. Problems with the melt sticking to steel is also greatly reduced, giving smooth slip in the calibrating unit.

Production of geometrically complex profiles like twin wall sheet is done by using a conventional vacuum calibrating unit. The surfaces of the calibrating elements should be chrome-plated. Vacuum slots are preferable to holes, because slots draw the profiles more uniformly. The distance between the vacuum slots should be about 10 to 15 mm, particularly in the front section of the calibration unit. Lengths of about 250 to 300 mm are sufficient for calibration units at about 100°C for PC. Take-off rates of 2 to 5 m/min are possible with profile wall thicknesses between 0.3 and 0.5 mm, for thicknesses from 1 to 1.5 mm the take-off rate is about 1 to 1.5 m/min. The distance between the extruder and the calibration unit should be as short as possible and never longer than a few millimetres. Its temperature should be fluid-controlled.

Small solid profiles are calibrated by means of sliding blocks, which in a vacuum quench tank sizing unit may be submerged in water. They are best mounted in a quench tank that allows the application of a vacuum, if required. This technique enables production of profiles virtually free from marks, at high take-off rates (8 to 12 m/min). The coolant forms a slip film between the profile surface and the calibration tool. This film also greatly reduces the risk of sticking. A short distance (5 to 20 mm) is necessary between the die and the sizing unit, and the calibration cross section should be adjusted to 0.2 mm above the desired wall thickness of the profile. The individual calibration blocks have a length between 40 and 50 mm. In the case of U-section profiles, the two arms are best extruded downwards. Calibration can be carried out by temperature controlled low-friction devices or by means of plates. The sizing plate method normally starts from the profile preformed in the die. A series of metal plates from which the desired shape of the profile has been cut out are arranged one behind the other in a cooling through or similar device. The profile passes trough the openings in these plates and is cooled with the air as it is drawn off.


XANTAR® engineering structural foam parts are best manufactured using a mixed-in chemical blowing agent. Working with a pure blowing agent (usually a fine powder) is not convenient, not always accurate, and needs more precautions than working with granulates. XANTAR MX 1051 is the denomination of MEP's blowing agent masterbatch suitable for the foaming of XANTAR® SF polycarbonate. The resulting chemical reaction during the injection moulding process is exothermic and the decomposition product that causes the internal pressure and provokes the foam is nitrogen.
The foam moulding cycle in principle consists out of three stages:

  • Plasticizing
  • Injection
  • Foaming

Plasticizing is performed rather similar to the same step in the conventional injection moulding process. There is however the danger of premature foaming inside the cylinder. This is prevented by two (hardware) modifications of the machine setup: a nozzle shutt-off prevents drooling from the nozzle and 'active back pressure' prevents expanding of the buffer.

After plasticizing, injection of the molten polymer takes place. The nozzle shutter is opened and the melt is injected into the mould at high speed. The mould is filled only partially to allow for the volume-increase, caused by the foaming process, that follows injection.

After injection, the nozzle is shut and within the cylinder, the plasticising for the following shot may start. In the cavity the melt is now subjected to atmospheric pressure and the blowing agent starts to release nitrogen gas. Because the injected melt volume is smaller than the cavity volume, the melt expands and bubbles are formed. This is called the foaming phase. No holding pressure is allowed, since completion of the mould filling is taken care of by the foaming process. Parts produced with this process have very low internal stress and are free from sink marks. After 1 to 3 minutes of cooling, the part can be removed from the mould. The cooling time depends on part thickness, melt temperature and mould temperature. If not cooled sufficiently, products will show post-blowing: expanding of the part after removal from the mould. Very thick parts, with a high heat capacity, are usually kept in water just after extraction from the mould to allow for the cooling to be completed.