Under normal conditions, ABS sheet is known for its good impact resistance, bending without breaking, but in some special circumstances, embrittlement can still occur. ABS sheet can be caused by prolonged direct sunlight, absorbing excessive ultraviolet rays and causing embrittlement, low-temperature embrittlement occurs when the temperature is lower than 20 degrees Celsius, and embrittlement occurs depending on the formulation of the sheet's production process.
What circumstances will ABS sheet become brittle?
Environmental factors
Low temperature environment: When ABS sheet is in a low temperature environment, its molecular chain movement ability will be weakened. The restricted movement of the molecular chain segments makes the material less flexible and the impact toughness deteriorates, thus exhibiting embrittlement. For example, if ABS sheet is used in cold outdoor environments, or if it is placed in low-temperature refrigerated or frozen environments, embrittlement is likely to occur.
Chemical erosion: If ABS sheet is exposed to certain organic solvents, acids and alkalis and other chemical substances for a long time, it may lead to its molecular chain dissolution, degradation and other changes. For example, when the ABS sheet and ketone, ester organic solvents in contact, these solvents may penetrate between the molecular chain, destroying the molecular chain of the regularity and the interaction force, so that the performance of the sheet is reduced, embrittlement.
Ultraviolet radiation: prolonged exposure to ultraviolet radiation, ABS sheet in the molecular chain will occur photo-oxidation reaction, molecular chain fracture, molecular weight reduction, so that the mechanical properties of the material deterioration, gradually become brittle. Such as long-term outdoor use and no protective measures of ABS sheet products, easy to be brittle due to ultraviolet radiation.
Processing factors
Improper processing temperature: In the ABS sheet moulding process, if the processing temperature is too high, the material will be overheated, resulting in molecular chain degradation, molecular weight distribution becomes broader, the material's performance decreases, and becomes fragile. On the contrary, if the processing temperature is too low, the material plasticisation is poor, the bonding force between the molecular chain is insufficient, will also reduce the toughness of the plate, the tendency to embrittlement.
Processing stress concentration: in the process, such as extrusion, injection moulding and other processes, if there is an unreasonable mould design, too high injection pressure or too fast extrusion speed, etc., may make the ABS sheet internal stress concentration. These concentrated stresses in the subsequent use of the process, easy to trigger the generation and expansion of cracks, and ultimately lead to plate embrittlement.
Material factors
Poor quality of raw materials: If the ABS resin raw material itself is not high purity, containing impurities, moisture, etc., or the acrylonitrile, butadiene, styrene, three monomers of the ratio is not reasonable, will affect the performance of the material, so that the ABS sheet is more prone to embrittlement.
Aging: With the increase of the use of time, ABS sheet will occur natural aging. In this process, the molecular chain will gradually occur fracture, crosslinking and other changes in the performance of the material gradually deteriorate, manifested as embrittlement, discolouration and so on.
Can embrittled abs sheets be recovered?
Slight embrittlement
If the embrittlement is slight due to short-term exposure to an adverse environment (e.g., short-term low temperatures, mild chemical contamination), you can try to place the ABS sheet in a suitable environment for a period of time to allow it to 'naturally recover'. For example, the low temperature embrittlement of the plate, in the temperature recovery, the molecular chain activity may be restored, the toughness will have a certain degree of improvement.
For embrittlement caused by mild surface oxidation, etc., the surface of the plate can be sanded, polished, etc., to remove the oxidised layer, which may improve the surface properties of the plate and alleviate the embrittlement phenomenon to a certain extent.
Severe embrittlement
For serious embrittlement caused by long-term aging, severe chemical attack, serious damage to the internal structure caused by processing, etc., it is generally difficult to recover by simple methods. Usually need to use some special technical means, such as the addition of toughening agents and other additives for mixing and modification, but it is also difficult to make the plate completely restored to the state before embrittlement. Moreover, this method is more difficult to operate, and it is more difficult to implement for already moulded sheets, even if they are reextruded as recycled plastics, the effect on performance is irreversible.
Embrittlement of ABS sheet even after treatment to improve, it is difficult to reach its original performance level, so in the use and storage of ABS sheet, should try to avoid making it in the environment may lead to embrittlement, in order to extend its service life and maintain stable performance.
