Acrylonitrile–butadiene–styrene (ABS) and acrylonitrile–styrene, more commonly called styrene–acrylonitrile (AS or SAN), are thermoplastics used in cosmetic packaging. Although ABS contains a SAN matrix, dispersed polybutadiene rubber particles give it substantially greater impact resistance. Consequently, the two materials are suitable for different perfume-cap designs.
ABS offers good impact strength, rigidity, dimensional stability, colourability, and a high-quality surface finish. These properties make it suitable for complex caps that must withstand repeated removal, accidental dropping, or strong snap-fit forces. A general-purpose ABS grade such as Terluran GP-22 combines mechanical strength with good heat-distortion resistance and injection-moulding flowability (INEOS Styrolution, 2026.-b). ABS can also be painted, vacuum-metallised, electroplated, or coated to create gold, silver, matte, and soft-touch finishes. Therefore, it is particularly useful when the cap requires an opaque or metallic luxury appearance.
The main limitation of ABS is that it cannot provide the crystal-clear appearance available from AS. Its polybutadiene phase is also vulnerable to ultraviolet degradation. Prolonged light exposure can cause yellowing, surface embrittlement, and reduced impact strength (Searle et al., 1989). These problems can be reduced by incorporating ultraviolet absorbers and hindered-amine light stabilisers, applying an opaque or UV-resistant coating, and avoiding unnecessary outdoor exposure. A PP inner insert can isolate the ABS shell from leaked perfume and carry the snap-fit load, reducing chemical attack and residual stress.
AS provides better transparency, surface hardness, stiffness, and chemical resistance than many general-purpose styrenic plastics. Luran 358N, for example, has light transmission above 89%, haze below 1%, a tensile modulus of approximately 3,700 MPa, and is specifically identified for cosmetic-packaging applications (INEOS Styrolution, 2026.-a). These characteristics make AS suitable for transparent or coloured-transparent caps with a clean, glass-like appearance.
However, AS is considerably more brittle than ABS, particularly around sharp corners, weld lines, and snap-fit features. Research shows that SAN can develop crazes and cracks when mechanical stress is combined with an aggressive environmental substance (Cho et al., 1998). AS can also undergo photo-oxidation, with oxidation of its styrene units contributing to discoloration (Mailhot & Gardette, 1994). These risks can be managed by using generous corner radii, uniform wall thickness, low-stress gate positions, and a separate PP insert for functional attachment. UV absorbers, protective coatings, and accelerated compatibility tests using the actual perfume formula should also be employed.
Both materials are normally injection moulded. ABS GP-22 is typically dried for two to four hours at approximately 80°C and processed at melt temperatures of about 218–260°C. AS 358N requires similar drying but is generally moulded at 220–260°C with a mould temperature of 40–80°C (INEOS Styrolution, 2026.-a, 2026.-b). Proper drying, short residence times, controlled injection pressure, and polished mould surfaces help prevent silver streaks, yellowing, internal stress, and visible flow marks.
Overall, ABS is preferable for durable, opaque, painted, or metallised caps, whereas AS is more appropriate for transparent, rigid designs. In both cases, a PP inner component and perfume-specific compatibility testing provide the most reliable protection against cracking and chemical exposure.