Yes, but density of PE can be very misleading. Let me explain.
HDPE is the "ideal" PE that we think about when we think of
polymerizing ethylene. The chains are repeating CH2 units and are
perfectly linear. LDPE is similar, but due to polymerization defects,
it has a number of branches. These branches prevent the chains from
crystallizing to a very high degree. Since crystals are more tightly
packed than non-crystals, they are more dense. Consequently, LDPE has
a lower density than HDPE. LLDPE is a copolymer of ethylene and
octene or some similar alpha-olefin. Like LDPE, the octene prevents
the PE from crystallizing, but since the branches are short (only 6 C
atoms long), the material still has better properties than LDPE.
So yes you can blend HDPE with LLDPE or such, but reducing the density
as an objective is not the right idea. What is it that you are really
trying to achieve?
Aspen Research, -
"Turning Questions into Answers"
Opinions expressed herein are my own and may not represent those of my