Reasons for ABS plastic aging

The aging of ABS plastic (Acrylonitrile Butadiene Styrene Copolymer) is caused by a combination of environmental factors and inherent characteristics of the material, mainly including the following reasons:

1. Thermal oxidative aging

High-temperature accelerated degradation: long-term exposure to high temperatures (> 60 ° C), the butadiene phase (rubber phase) in ABS is easy to react with oxygen, resulting in molecular chain breakage, the material becomes brittle.

Performance: yellowing of the surface, loss of gloss, significant reduction in mechanical properties (e.g. impact strength).

2. Ultraviolet (UV) radiation
Photo-oxidation: UV light triggers free radical reactions in styrene and butadiene chain segments, destroying the polymer structure.

Performance: surface chalking, color fading (especially dark ABS), cracks ("cracking" phenomenon).

Protection: need to add UV stabilizers or carbon black and other shading agents.

3. Hydrolysis
Moisture sensitivity: The acrylonitrile component in ABS is easy to absorb moisture, long-term exposure to high humidity environment (especially high temperature and high humidity) will trigger hydrolysis.

Performance: molecular weight decrease, tensile strength and modulus decrease, silver grain may appear.

4. Chemical corrosion
Solvent erosion: ABS is not resistant to strong polar solvents (such as ketones, esters, some halogenated hydrocarbons), which can lead to swelling or stress cracking.

Performance: sticky surface, deformation, or even localized dissolution.

5. Mechanical Stress Fatigue
Dynamic loading: Repeated bending or impact will trigger microscopic cracks, especially in the butadiene phase expansion, accelerated aging.

Performance: Stress whitening, brittle fracture.

6. Environmental Stress Cracking (ESC)
Stress + medium synergy: Even weakly corrosive mediums (e.g. detergents, alcohols) may initiate cracks under stress.

Performance: sudden brittle cracking without warning.

7. Microbial degradation (rare cases)
Certain microorganisms (e.g. molds) may attack additives (e.g. plasticizers) in ABS, leading to surface degradation.

Aging Characterization Methods
Appearance changes: yellowing index (ΔYI), surface roughness.

Mechanical properties: Impact strength, tensile strength reduction rate.

Molecular weight analysis: GPC to measure molecular weight distribution.

FTIR: Detection of oxidation products such as carbonyl (C=O).

Ps: The above news come from website.