Question

which causes plastics non decomposable

Answer 1

Oxo-biodegradable. They are based on conventional plastics, like polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET), to which additives, that shouldcause the plastic to degrade by a process initiated by oxygen and accelerated by light and/or heat, are added

Answer 2

Because petroleum-based plastics like PET don't decompose the same way organic material does. ... This kind of decomposition requires sunlight, not bacteria. When UV rays strike plastic, they break the bonds holding the long molecular chain together