EVOH up to 5%, with a minimum of 32 mol% ethylene
Ethyl Vinyl Alcohol (EVOH) is a common layer material used to increase the barrier properties of HDPE. It is not separable in the recycling process and therefore will become part of the recycled HDPE. APR guidance is that a package containing up to a 5% layer by weight of EVOH with a minimum of 32 mol% ethylene can be compatible with the residential postconsumer HDPE recycling stream. Package with a thicker EVOH layer or lower mol% ethylene may be tested according to APR Critical Guidance tests for compatibility in the HDPE recycling stream.
A number of innovative packages using EVOH barrier material have received APR Critical Guidance Recognition.
Workhorse additives historically used without issue
Most HDPE in a package contains some form of additives. The "workhorse" additives commonly used have not been shown to cause significant issues with the recycling process or further uses of the recycled HDPE. Commonly acceptable workhorse additives include:
- Thermal stabilizers - These additives typically enhance the further processing of the polymer and are therefore preferred for recycling.
- UV stabilizers – These additives typically enhance the further processing of the polymer and are therefore preferred for recycling
- Nucleating agents
- Antistatic agents
- Fillers – note that many fillers are dense, so particular attention should be paid to the overall blend density
- Impact modifiers
- Chemical blowing agents
Additive usage should be minimized to maintain the best performance of recycled HDPE for future uses.
REQUIRES TEST RESULTS
Non-HDPE barrier materials other than EVOH
Testing must show that layers and coatings will either separate and be removed from the HDPE in the recycling process or have no adverse effects on the recycled HDPE in future uses. When used, their content should be minimized to the greatest extent possible. Some layers and coatings have been found compatible with HDPE or are easily separated in conventional recycling systems. Companies that are considering such barrier materials and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.
A number of innovative packages using non-EVOH barrier materials have received APR Critical Guidance Recognition.
Additive concentration causing the overall blend to sink in water
Many of the additives and fillers used with HDPE are very dense and when blended with the polymer increase the overall density of the blend. When their weight percentage reaches the point that the blend density is greater than 1.00, the blend sinks in water rather than floats. Density is an important property and float-sink tanks are critical separation tools used by reclaimers. Therefore, a sinking material will be considered waste by a polyethylene reclaimer and any HDPE in the blend will be lost.
Degradable additives (photo, oxo, or bio)
Recycled HDPE is intended to be reused into new products. The new products are engineered to meet particular quality and durability standards given properties of typical recycled HDPE. Additives designed to degrade the polymer by definition diminish the life of the material in the primary use. If not removed in the recycling process, these additives also shorten the useful life of the product made from the recycled HDPE, possibly compromising quality and durability.
Degradable additives should not be used without testing to demonstrate that their inclusion will not materially impair the full-service life and properties of any product made from the recycled HDPE that includes the additive. Testing must show that these additives will either separate and be removed from the HDPE in the recycling process or have no adverse effects on the recycled HDPE in future uses. When used, their content should be minimized to the greatest extent possible.