ABS plastics: styrene/copolymer blends; ABS copolymer; ABS terpolymer 4. Some Suppliers 5.Trade Names or Trade Marks
A Schulman Inc. Polyman ABS
Ashley Polymers Inc. Ashlene
BASF Terluran
Bayer Novodur
Chi Mei Corp Polylac
ComAlloy International Corp. Comalloy ABS
Daicel Polymers Cevian
Dow Carbide Magnum
DSM (Dutch State Mines) Ronfalin
Elf Atochem S.A. Arrhadur
EniChem Sinkral
Ferro Corp Starflam ABS (ABSFR)
General Electric Co. - see G.E. Plastics
G.E. Plastics Cycolac
G.E. Plastics (Fr.) Ugikral Hoechst Daicel Polymers Cevian Industrial Resistol Epolan
Lati Lastilac
LG Chemicals LG ABS
LNP Engineering Plastics Thermocomp (ABS-30%GF)
Monsanto Lustran
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Monsanto Lustran Ultra ABS ABS Alloys - other Material(s) Not Known Hoechst Daicel Polymers Novalloy ABS/PA Alloys
DSM (Dutch State Mines) Stapron M DSM (Dutch State Mines) Staloy N ABS/PBT
DSM (Dutch State Mines) Stapron C ABS/PSU
USS Chemicals Arylon T
ABS/PVC
DSM (Dutch State Mines) Ronfaloy V 6. Material Properties
ABS plastics were originally made by blending a lightly cross-linked nitrile rubber (NBR) into an styrene-acrylonitrile (SAN) copolymer.
These materials are now commonly produced by polymerizing styrene and acrylonitrile, in the presence of polybutadiene (BR), in the latex form. This process results in a product consisting of BR grafted with styrene-acrylonitrile (SAN) copolymer. The grafted BR phase (the rubbery phase) is then melt com-pounded with rigid (SAN) material to give ABS. Also added at this stage are additives such as stabilizers, lubricants and colorants. The plastic phase, which is usually called the “rigid” phase, is SAN which comprises more than 70% of the total composition. The grafted polybutadiene phase, which has a high rubber content, may also be used as an impact modifier for other plastics such as polyvinyl chloride (PVC).
By varying the monomer ratios, the way in which they are com-bined, the size (and the amount) of the rubber particles, the cross-link density of the rubber particles, and the molecular weight of the SAN, it is possible to produce a wide range of materials. These variations lead to materials that may differ in their impact strength, ease of flow, color, etc. In general, as the mole-cular weight of the SAN is increased, the strength and rigidity of the ABS increases. As the rubber content increases the impact increases, but the strength, hardness, heat resistance and rigidity of the ABS decrease. This fam-ily of materials can be divided into injection molding grades and extrusion grades. In turn, each of these two major divisions can be sub-divided into medium, high and very high impact grades. There are also other grades such as high heat, plating and flame retardant grades.
In general, ABS is a hard, tough material with good resistance to impact, even at low temperatures. It has low water absorption and is a good electrical insulator. The electrical properties are unaffected by changes in humidity. It is usually available in opaque colors, although translucent material
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se ction 8: guides for the foll o w ing ma terials
and colors are available. The moldings can have a high gloss, are dimension-ally stable and give good reproduction of the mold surface. The molded sur-face is resistant to scuffing, but the material has poor weathering properties.
It has superior heat resistance and impact strength compared to TPS. It has a higher flexural modulus than PP, which often permits lower wall thickness, and, as it is an amorphous material, it is faster cycling. It is not as notch sen-sitive as PC and PA.
The highest gloss levels are achieved with moderate melt tempera-tures, high mold temperatempera-tures, fast filling speeds and moderate packing pres-sure. For electroplating applications, it is necessary to produce injection mold-ings with low levels of internal stress. For a given material, the levels of resid-ual stress are governed by the molding conditions employed. In general, dur-ing injection molddur-ing, the lowest levels of residual (internal) stress are pro-duced by using high melt temperatures, high mold temperatures and slow cooling rates. If relatively small gates are employed, the use of fast injection speeds may result in low levels of internal stress. If large gates are employed, the use of slow injection speeds is usually recommended. Melt and mold tem-peratures should be as high as possible and the packing pressure moderate.
The use of such conditions will also minimize warping.
By blending ABS with other plastics, it is possible to extend the range of use. For example, the use of PC or SMA improves the heat distortion temperature, while the use of PVC improves flame retardancy. These alloys have higher viscosities than standard ABS. Typically the ratio of ABS:PVC is 80:20. By blending ABS with chlorinated polyethylene (CPE), a type of ther-moplastic elastomer (TPE) may be produced, which has improved tear and abrasion resistance (compared to the unmodified material). The addition of approximately 10% of a liquid polybutylene (polybutenes are viscous, non-drying liquids) to an ABS, can double its impact strength at both room tem-peratures and -40EC/-40EF. This type of blend can have melt viscosities and heat deflection temperatures similar to the unmodified material. There may be a modest decrease, however, in tensile and flexural properties.
If, during polymerization, part or all of the styrene is replaced by α-methylstyrene (AMS), a high heat grade, with increased heat resistance, is produced. Alloys with styrene-maleic anhydride (SMA) also give high heat grades that have a lower melt viscosity at a reasonable cost. Clear ABS grades may be made by using methyl methacrylate (MMA) as a fourth monomer and/or, by blending ABS with PMMA; this improves the transparency, as it helps to match the refractive index of the other materials. When low levels of polymerization emulsifier are used during manufacture, grades are produced that offer up to approximately 80% light transmission and a haze level of 10%. Other properties are similar to those of medium impact, standard ABS materials.
By the incorporation of CPE into SAN, ABS-type materials known as ACS result. These have better flame retardancy, heat resistance, weather-ability and resistance to dust deposition than ABS, but they have poorer pro-cessing stability. Olefin modified SAN results from the incorporation of olefin elastomers into SAN. They have properties similar to ABS, but have better weathering properties.
Styrene plastics are not naturally flame resistant although their flame resistance can be improved by the use of flame retardant additives, such as a bromine compound and antimony trihydrate (ATH). Octabromo diphenyl oxide (OBDPO) is often suggested for use in ABS, although high lev-els may be required (for example, 15 parts per hundred of resin (phr) of bromine may be needed). The bromine content of ABS compounds needs to be approximately 50% higher than those based on HIPS. Compounds based 152
on 1,2-bis-(2,4,6-tribromo phenoxy) ethane (TBPE) are preferred where rea-sonable light stability is required, although mixing/dispersion is often poor and the FR compound has relatively poor thermal stability compared to OBDPO.
Because of the level of use, and the relatively stiff flow behavior of ABS, FR additives that ease the flow are to be preferred. ABS/PVC blends are flame retardant, but the PVC reduces the processing stability relative to ABS.