ABS can be processed by any process suitable for thermoplastic molding compounds.

Predrying

Under unfavorable storage or transport conditions, ABS can absorb small amounts of moisture. This can cause surface faults during processing which are visible on the finished article. To avoid these, predrying to a residual moisture content of <0.1% is generally sufficient. This can be achieved using, for example, dry air driers, vacuum driers or circulating driers; from 2 to 4 hours at 80°C is usually sufficient.  Depending on temperature, humidity and the proportion of fresh air, circulating driers require longer drying times.  If a vented screw with adequate venting capability is used, predrying is unnecessary, as long as the pellets have not become excessively moist during storage.

Compatibility with other thermoplastics

ABS is incompatible in the melt with most thermoplastics, such as polyolefins, polystyrenes and polyamides. Delamination occurs and the moldings have low strength.

Recycling

If its previous processing has not involved contamination or thermal degradation, ABS can be reused in the form of regrind. Since the surface area of regrind is higher than that of pellets, regrind can absorb moisture more rapidly and usually has to be dried before reprocessing.  It is normally advisable to use virgin granules for moldings which are subject to high quality requirements.

Injection molding

ABS can be processed on any commercially available injection-molding machine.  ABS’ wide processing range, good thermal stability, low mold shrinkage and low tendency to warp make injection molding relatively easy. The moldings generally have surfaces with good luster. The highest surface gloss is achieved at high injection rates and the highest possible mold surface temperature, insofar as molding and gate geometries permit.

Gate and mold design

In general, any of the known types of gate may be used.
Gating systems should be adequately dimensioned; narrow gates require excessively high melt temperatures and injection pressures, with the resultant possibility of streaking on the surface of the molding, or gas burning. Too rapid freezing of the melt at the gate can lead to voids and sinks in the molding, since the contraction of the melt during the hold pressure phase cannot be sufficiently compensated.

Draft angles and ejectors

The favorable surface slip properties of ABS grades mean that injection moldings made from them are easy to demold, and even complicated moldings can be produced with success.  Draft angles of from 0.5 to 1° are generally sufficient. In the case of textured surfaces, the draft angles must be larger.
The ejector or stripper plates should have as large a surface as possible, so that the molding is not punctured or distorted during demolding.

Mold temperature control

The gloss, shrinkage and, within certain limits, the mechanical and thermal properties of the molding are influenced by the mold surface temperature. Higher mold surface temperatures give higher gloss, better weld line strengths and lower intrinsic stresses, and as a consequence a lower tendency to warp. Mold surface temperatures up to 80°C have proven successful in practice. Even at temperatures in the upper part of this range, ABS grades harden rapidly, because of their high heat resistance.  Even under these conditions, therefore, short cooling times resulting in more cost-effective cycle times are achievable.

Processing temperature

ABS is usually processed at melt temperatures from 230 to 260°C. The melt temperature should be monitored with a needle pyrometer.

Feed characteristics

Even at high screw rotation rates, plasticating of ABS molding compounds proceeds smoothly and without thermal degradation.  It is frequently possible to set the individual heating zones of the plasticizing cylinder to the same temperature. For processing temperatures at the upper end of the range and/or for long cycle times, the temperature of the first heater band (near to the feed hopper) should be set somewhat lower, in order to prevent premature melting of the granules in the feed zone (bridging).

Shrinkage

The processing shrinkage is usually no greater than 0.7%. The post-shrinkage is usually negligible. Although the shrinkage is primarily a property of the material, it is also influenced by the shape of the molding and by the processing conditions. The shrinkage in different regions of a molding can therefore vary greatly. In zones subject to, for example, a high holding pressure, a value of close to 0% can be achieved.

Special injection molding processes

ABS is especially suitable for use in multi-component injection molding, e.g. hard-soft combinations or combinations of several colors or of different products at least partially compatible with one another, such as Luran (SAN), Luran S (ASA), other styrene copolymers or certain thermoplastic polyurethanes.
ABS can also be used in the gas assisted injection molding process. Back filling onto textiles or films in a single process is also possible: in-mold labeling and in-mold decoration.

Machining

Semifinished products made from ABS are easy to machine, i.e. die-punch, saw, drill, mill, turn etc., using conventional metal- and woodworking equipment.
Tools used for machining brass and bronze may be used. Because heat dissipation is slow, water cooling is frequently necessary, even at low cutting speeds.

Adhesive bonding and welding

ABS moldings can be bonded easily to one another using solvents, such as methyl ethyl ketone, acetone, ethyl acetate, dichloroethylene or cyclohexanone.  ABS moldings can also be bonded to moldings made from Luran S (ASA), Luran 378 P or 388 S (SAN), by the same method.  If adhesion problems occur, we advise you to seek information from the adhesives industry, which offers a wide variety of suitable special adhesives.  Semifinished products and moldings made from ABS can be welded by hot-plate welding, spin welding, vibration welding and ultrasonic welding.  Since the quality and the appearance of the welded joint can be strongly influenced by machine parameters, as well as by material properties and the type of joint surface, exploratory experiments are essential in each individual case.  Ultrasonic welding can also be used to bond ABS moldings to moldings made from related thermoplastics (SAN, ASA, PVC and PMMA).

Painting, printing and vacuum metalizing

ABS may be easily and permanently printed, flocked, embossed, painted or vacuum metallized.
In painting, the applied layer should not be too brittle; otherwise the impact strength of the finished article is greatly reduced.  Solvents used in surface coating systems have to be specially chosen to avoid stress cracking of the substrate.  Detailed information on surface-coating processes is available from the manufacturers of such coatings.

Laser marking

Compared with conventional processes for marking, laser marking gives high flexibility and speed, wear resistance and security against counterfeiting. A particular advantage is that moldings can be marked without contact and while in motion. Usually, no pretreatment is necessary.  For flexible laser marking, Nd:YAG lasers are most frequently used. Mask laser marking, using an excimer laser source or certain CO2 laser sources, is suitable for marking ABS.  Pale colors are easily laser-marked, but even dark colors can be marked, using a light-colored marking for example.  The quality of the marking (contrast, uniformity, definition) depends mainly on the pigment formulation and the degree of homogeneity.

Please refer to the Material Safety Data Sheet (MSDS) of the corresponding ABS grade.
Further information concerning the MSDS as well as other information regarding safety and ecological aspects can be viewed under the menu Styrolution website, www.styrolution.com.