Recycling Of Plastic Bottles Labelled With Radiation Cured Films And/Or Adhesives

INTRODUCTION

Growing concern about the environment and rapidly dwindling waste disposal
space make reduction of waste a necessity. Therefore, the recycling of plastic
containers is being persued with increasing intensity and, in that context,
the labels used on plastic containers must be taken into consideration as
well. Paper and vinyl film labels generally must be removed prior to recycling.
Other polymeric films may or may not interfere. Similarly, the adhesives used
to affix the labels may or may not present a problem. Accordingly, the effect
of each label material on the recyclability of each bottle material needs to
be investigated.

The present study is concerned with bottles made out of polyethylene—
terephthalate (PET), high density polyethylene (HDPE) and low density,
polyethylene (LDPE).

The labels used for this'study consisted df either LOPE film or a
radiation cured polyester film as described in 'The adhesive was a
pressure sensitive adhesive (PSA) based on radiation cured polyesters as
described in (2-4).

For PET bottles, two alternative recycling techniques.were used, i.e.:
1. Direct recycling, involving grinding, homogenizing in a twin—screw
extruder and injection molding, and
2. Chemical recycling by glycolysis. This involves grinding and
reacting with excess glycol at 200°C in the presence of an
esterification catalyst. The glycolysate was subsequently
submitted to'polycondensation.

HDPE and LDPE bottles were subjected to direct recycling only.
Standardized test specimen were prepared by injection molding and

subjected to a tensile test.