What Film Quality Can Be Achieved with the Use of Recycled LDPE?

Never before has the quality of a recycled LDPE granule been so important for the production of a film, as the expectations of the market, which is moving from virgin to recycled raw materials, are very high.

It is not always easy to convey to the customer, who wants to produce with recycled LDPE , the need to know the genesis of recycling so as not to make a mistake in purchasing the product based, perhaps, only on the economic convenience of the recycled raw material compared to the virgin one that comes to him. offer.

Let's say, in principle, that even in the field of recycled LDPE there are product families through which some items can be produced and, consequently, others cannot be produced if you always want to obtain a good technical and aesthetic result on the finished article to be placed on the market.

The macro families can be distinguished into three areas:

• Post-consumer recycled LDPE

• Industrial post-consumer recycled LDPE

• Post-industrial recycled LDPE

The post-consumer LDPE granule is produced through the recycling process of waste from separate waste collection, which is separated, ground, washed, densified and extruded into granules.

The first thing to consider about the products of this family is the degree of contamination to which the processed film is subjected during its life . In fact, separate waste collection involves mixing pollutants, such as food remains, oils, fats, into household waste bags. , polylaminates of food packaging and many other products which, during the collection phases, form solidarity with the film to be recycled, creating a quality problem downstream of the process.

Furthermore, during mechanical separation , it may happen that parts of other plastics remain within the flow of LDPE to be recycled, creating another stream of contamination in the granule production process.

Mechanical recycling systems include washing the selected material but, often, this is not sufficient to reduce the presence of plastics other than LDPE and the dissolution and detachment of non-plastic parts present on the product to be washed.

These contaminations can create various problems in the production of the film:

• Pungent odors in the finished product

• Brittleness when cut due to the presence of polypropylene

• Lumps not melted during the extrusion phase with consequent pitting of the film

• Irregularity of the film surface due to the degradation of impurities in the extrusion phase

• Inconsistency of the film due to the excessive presence of gas inside the granule caused by the degradation of the extruded material

• Difficulty in creating a regular bubble following the possible degradation of the polymer during the blowing phase due to the presence of the problems listed above.

The use normally made of post-consumer LDPE granules from separate waste collection is reserved for rubbish bags with a thickness of no less than 100-120 microns , of dark colours, in which the possible smell, the speckling of the film and the possible fragility when cutting is tolerated by customers at a competitive price.

Another application is temporary covering sheets , normally black, with thicknesses from 140 to 300 microns in which the impurities present in the granules are diluted in the generous thicknesses of the film.

The industrial post-consumer granule is a product very close to the post-industrial category that we see later, as the material input does not come from separate waste collection but exclusively from the collection of industrial packaging , supermarkets and the commercial sector, whose packaging films are not contaminated in any way by harmful substances for recycling.

Once collected, these films are divided by color, ground, washed, densified and extruded into granules suitable for the production of films.

What are the advantages of this flow:

• Material not contaminated by organic waste or industrial liquids

• Selected by color

• Selected by type of plastic

• Normally subject to first recycling

• Does not contain polylaminates from food packaging

The production of films with this type of material allows the creation of very thin thicknesses, starting from 20 microns, using 100% recycled granules.

The film remains elastic, the welds do not open as the negative influence of the presence of PP as in post-consumption does not occur, it does not present unpleasant odors, transparent films can be created, even if starting from a non-transparent granule, or colored film by adding the master.

There is also a version suitable for the production of black film, mainly dedicated to garbage bags with thicknesses from 20 to 100 microns or to roofing sheets for construction where a good degree of tear resistance is required.

The neutral post-industrial granule normally comes from neutral film processing waste which is collected and divided by color, ground and extruded again into granules for production.

Another type of post-industrial LDPE is characterized by the use of waste from the polymer processing of the petrochemical industries , which are compacted into blocks or bars, to then be ground or pulverized and reused as a raw material during the extrusion phase of the granules.

This type of recycled LDPE is very similar to a virgin polymer , both in terms of mechanical characteristics and transparency in the production of the film. It has no odors, no color alterations, it can be mixed with virgin raw material if required and it retains excellent mechanical and quality characteristics of the surface.

Related articles:

• LDPE RECYCLED FROM POST CONSUMER: 60 TYPES OF ODORS OBSTACLE SALES
• LDPE FROM POST CONSUMER. HOW TO REDUCE IMPERFECTIONS. EBOOK

Category: news - technical - plastic - recycling - LDPE - plastic films - post-consumption

See more information on LDPE recycling