HDPE composites

High density polyethylene (HDPE) is produced from the polymerization of the ethene monomer.   Cellulose is the major component of wood and other plant material.  Wood plastic composites (WPC) are a  mixture of the two.  This Wikipedia link discusses pros and cons of WPC.  In many communities, finding any to keep HDPE out of land fills garners some interest.  The challenge is mixing water loving, hdrophilic cellulose with hydrophobic polyethylene.  Most of us realize that olive oil does not mix with water.  Some of the details are currently being left of out this ongoing protocol.  Details of time and temperature will be supplied if this turns into a citizen scientist project.

HDPE_newspaper0
Cellulose found in wood and paper has hydroxyl groups (-OH) that bond to water (H2O). Polyethylene more closely resembles compounds like olive oil, which do not mix well with water.

In this particular example a half gallon milk bottle with residual milk was melded with some local grocery fliers.  These are colorful, ink saturated newspaper that are said to have little value for recycling.  HDPE  is also rumored to have poor value because of the effort it takes to remove the residual foods such as milk.

HDPE_newspaper1
A homemade composite of newspaper and recycled HDPE half gallon milk bottle. A bottle cap and were also added to the mix.

This particular composite measured 7.5 x 17 cm.  The thickness was about 5 mm.   The strength was tested by placed an ~1 kg brick on top.

HDPE_newspaper2
A 1 kg brick sitting on a homemade HDPE/newspaper composite.

This material showed no sign of bending.   While some may find some artistic value in the colored print that shows through, others may find it ugly.   Colored newspaper is not the only material with poor recycle value that we are trying to keep out of landfills.

Cotton Clothe HDPE composite?

This particular material was from a cotton pillow case with a thread count of maybe 20 threads per cm.  In this case three 16×6 cm strips were layered between the HDPE in a 1 gallon plastic milk bottle with residual whole milk.  More difficulty was encountered in keeping the composite flat in the 11 x 21 cm baking pan.  The resulting composite was about 16 x 6 x 1 cm.  It had the dimensions of the clothe rather than the baking pan.

HDPE composite made with plastic milk bottle with residual milk and a cotton woven fabric.
First cotton clothe / HDPE composite.

While this composite was slightly bent, it held 2 liters ( 1 kg) of water in a soda bottle.

HDPE_clothe2

The cotton/HDPE composite was very solid with not evidence of air bubbles.  There was some fabric sticking out of the sides that will have to be addressed in the next iteration.

A remark was made that these HDPE composites are ugly and never suitable for fence slats.  Some leaf debris that looked vaguely like pine needs was chosen for a test.  Three layers of this debris was heated between four pieces of HDPE from a one gallon HDPE milk bottle.  This bottle did not have much residual milk.  The dark black arrows point to needles poking out of the sides..

HDPE_needles_1

Unlike other trials, there was an air pocket in side 2 but not side 1 (thin gray arrow).

HDPE_needles_2

Even with the air pocket, this 8 x 17 x 1 cm piece could support the weight of a 2 liter soda bottle filled with water.