Depending on the contamination level, both a food-grade and a non-food-grade recycled LDPE are available. Due to the diverse sources of LDPE waste, the availability of the food-grade recycled LDPE is considerably lower than that of the non-food-grade. The corresponding application products for food-grade applications are flexible bottles, lids, or milk cartons. The non-food-grade products are new plastic bags, hoses and cables, floor tiles, vehicle parts, toys, detergent containers, shipping bags, rubbish bin liners, and compost bins, as well as foils and films. Films made of recycled LDPE find a broad application in the agricultural industry.
There are various approaches to optimize the properties of LDPE recyclates for a specific application, like mixing the recycled and a virgin LDPE or use of additives including stabilizers, color masterbatches, fillers, etc. Particularly, the use of cellulose-based fillers like wood fibers is beneficial in the case of the LDPE due to its low melting temperature (105 – 115 °C). A further advantage of this approach is the ecological point of view, since the resulting composite is made of a recycled LDPE and a filler based on renewable resources.
LDPE (or also PE-LD) is a thermoplastic polymer from the polyolefin family, which consists of repeating ethylene units. Compared with high-density polyethylene, LDPE has a more branched molecular structure and weaker intermolecular forces. This results in various advantageous properties of LDPE, like high impact and moisture resistance. The typical density range for virgin and recycled LDPE is 0,92 – 0,93 g/cm3. Furthermore, it is soft, possesses high elasticity, and is available in a highly translucent form. At the same time, LDPE has lower strength and stiffness than HDPE.
These properties led to the main application field of virgin LDPE in plastic bags. In general, the amount of recycled LDPE is lower than that of the HDPE. This situation is associated with technical challenges during the recycling of light and soft plastic films. Depending on the input source, recycled LDPE is available in various qualities and colors. Post-consumer LDPE recyclates represent mostly mixtures of LDPE and HDPE and are offered in grey or black colors. The post-industrial LDPE is available in individually adjusted colors. Finally, the use of additives enables application-specific optimization of the recyclate properties.
LDPE is one of the most commonly used plastics worldwide. The main post-consumer LDPE feedstock for food- or non-food-grade applications is retrieved from packaging materials such as films, carrier bags, or squeeze bottles.
A large part of the post-industrial LDPE feedstock materials is based on various films, products from electronics, and chemical tank linings. Typically, LDPE recyclates are available as LDPE granules suitable for extrusion molding. Further forms of LDPE recyclates are regrinds from a wide variety of applications such as containers, pallets, water and gas pipes, or cable sheathing as well as agglomerates obtained from heavy-duty sacks.