Aliphatic amines contain only H and alkyl substituents. Epoxy resins diluents are typically formed by glycidylation of aliphatic alcohols or polyols. Aliphatic, cycloaliphatic and aromatic amines are all employed as epoxy hardeners. Representative laboratory routes to aromatic acyl halides are comparable to those for aliphatic acyl halides. An aliphatic diol is also called a glycol. Mechanisms differ for aliphatic and aromatic aldehydes and for aromatic and aliphatic phosphonium ylides. An alternative to aromatic substitution is electrophilic aliphatic substitution. Nitrile rubber is generally resistant to aliphatic hydrocarbons. It consists of high molecular weight saturated aliphatic hydrocarbons. The isocyanate can be aromatic or aliphatic in nature. JP-4 was a mixture of aliphatic and aromatic hydrocarbons. Polyglycolic acid is a thermoplastic polymer and an aliphatic polyester. Steam cracking is the process for producing ethylene and other alkenes from aliphatic hydrocarbons. Compared to aliphatic polyesters, Nylon 6 has poor biodegradability. These acids may be aromatic or aliphatic (nonaromatic).