UNITIKA Nylon 6
(4) Chemical Resistance
Nylon resins exhibit excellent chemical resistance. The chemical resistances are summarized below with respect to each group of chemicals.
Nylon resins are not degraded chemically by pure water, and all the effects, if any, are physical. These effects are the results of water working as a plasticizer. However, the resins may be degraded by hydrolysis when they are stored at high temperature for an extended period of time. Water containing oxygen may oxidize nylon resins at high temperature.
Nylon resins are stable in most inorganic chemicals including liquid ammonia, sulfurous acid, and others, but may be eroded with oxidants such as hydrogen peroxide and chlorine-based decolorants.
(a) Acids and alkalis
Nylon resins are eroded in concentrated inorganic acids at room temperature, but fairly resistant to dilute acids. The resins are significantly resistant to alkaline solutions, and are stable to up to 20% alkaline solutions at room temperature. The resins are almost stable in weak alkaline solutions containing, for example, calcium carbonate or sodium carbonate even at high temperature.
Liquid or gaseous halogens oxidize nylon resins, resulting in discoloration and change in physical properties of the resins.
Nylon resins exhibit significantly great resistance to organic solvents, oils, and fuels.
(a) Organic solvents
Esters, halogenated hydrocarbons, mercaptans, glycols, and aldehydes (except formaldehyde) exert completely or almost no effects on nylon resins. Both phenols and cresols dissolve nylon resins, but the dilute solutions of these compounds have only limited effects. Benzylalcohol, nitrobenzene, nitroalcohol and others dissolve nylon resins at high temperature. However, the effect is negligible at room temperature.
Nylon resins are extremely resistant to oils and fuels. Although nylon resins absorb some of them depending on the kind of the resins, there are no observable degradation and permanent chemical change. Hereinafter, the chemical resistance of nylon resins is summarized. In the Table, the following symbols are used:
- A. Completely non-erosive to nylon resins, completely or almost non-absorbable and has smaller effect on mechanical properties.
- B. Completely or almost non-erosive to nylon resins, but slightly swells nylon resins, leading to change in mechanical properties.
- C. Slightly erosive to nylon resins at room temperature. The use period should be restricted, as it may be absorbed in significant amount.
- D. Dissolves or decomposes nylon resins at room temperature in a short period of time.
Although the classification above is not strict and thus there is some ambiguity between the categories, use the Table as a general indicator in determining the suitability of nylon resins for use in specific applications. Final decision is preferably made after evaluating test pieces.