1). Polyethylene chemical formula is:
-(CH2CH2)n-
Roughly:
HDPE is a linear polymer
LDPE is a branched and/or cross linked polymer
LLDPE is a low branched and rather linear polymer
2). Cured epoxy resins of Bisphenol A with polyamines H2N-(R)-NH2 , have the chemical formula:
-(-)N[-CH2CH(OH)CH2O-Φ-C(CH3)2-Φ-OCH2CH(OH)CH2NH-(R)-N(-)-]n-
Epoxies are highly cross linked materials.
Bisphenol F has an additional -CH3 substitution on the aromatic ring, compared to Bisphenol A.
There are also aliphatic epoxy resins, as well as curing agents that are based on aromatic polyamines, but both are expensive and thus, rarely used.