Design elements that influence the recycling of PET container packaging products

        A large proportion of PET recycling comes from the recycling of PET bottles. The production efficiency and product quality of the recycling process are constantly affected by the non-recyclable design elements of the front-end PET bottles, mainly from the material selection and design form of the bottle resin, color, barrier layer/coating/additives, cap/pump head, label/ink/adhesive and accessories.

        ◆Bottle resin and color

         PET bottles are the main materials for recycling and regeneration. Homologous bottle-grade PET polyester chips and bio-based PET with a melting point between 225℃-255℃ are well compatible with the recycling system. Colorless and transparent blue PET bottles are the most popular colors in the recycling industry. The recycled plastic products produced are also the most colorless and transparent, with the widest application range, and can be used for high-value applications and same-level recycling. The darker the color, the narrower the corresponding downstream application direction, the more it tends to be downgraded, and the lower the commercial value and willingness to recycle.

        ◆Barrier layer/coating/additives

        PET products need to add a certain proportion of barrier layers, coatings or additives to achieve certain functionality, and these added ingredients are often difficult to distinguish and identify from the appearance of the product, which brings trouble to subsequent recycling. When designing packaging, it is necessary to consider the possible impact of these non-PET materials on subsequent PET recycling and regeneration, and reduce or avoid their use. These common additives include plasma carbon coating, nylon, PVDC barrier, nucleating agent, fogging agent, fluorescent brightener, carbon black and degradable materials.

        ◆Capping/Pump Head

        Bottle caps and pump heads should be designed with materials with a density less than 1, such as the commonly used PE and PP materials, which are conducive to separation from PET during the sorting process. Materials with a density greater than 1 require auxiliary near-infrared sorting equipment or other sorting methods to remove impurities during the regeneration process, which has a negative impact on PET production and quality and reduces production efficiency. In addition, the use of polyvinyl chloride (PVC) materials should be avoided in bottle caps/seals/pump heads. PVC will cause the recycled PET material to turn yellow and become brittle, accompanied by chlorine volatilization, and is a non-recyclable design. The national standard requires that the PVC content of PET crushed flakes for high-quality fiber should not exceed 50mg/kg.

        ◆Labels/Inks/Adhesives

        Label films are generally attached to PET bottles by adhesives, or fixed to packaging by physical shrink sleeves. The design mainly considers how to separate them from PET in a simple and economical way during the recycling process without polluting the PET recycling flow. Labels/inks/adhesives usually appear in combination with different technical solutions:

        Ink and label (excluding adhesive), when the PET bottle body is irregular in design, cannot be labeled, or requires a large area of label blocking, companies often use a full set of bottle labels (heat shrink labels) with a density greater than 1 to wrap the whole bottle, or do not use labels and directly print on the PET bottle body with ink.

        Non-washable adhesive labels (wrap labels) are commonly made of flexible PP or PET films. They are cheap and have poor conformability to the bottle body, but the label size and the adhesive used at the head and tail links are minimal, making them easy to remove and conducive to recycling.

        Non-washable adhesive labels (self-adhesive labels) have a wide range of materials, and common surface materials include plastic, paper, and materials containing metal elements, but the cost will be relatively high. From the perspective of the recycling process, self-adhesive labels mainly consider the impact of adhesives and should be easy to remove.

        Washable adhesive labels can achieve clean label separation through adhesive technology innovation, perfectly solving the label removal problem and impurity residue of traditional self-adhesive labels, thereby achieving higher recycling yield and better recycling quality.

        According to the survey data of the Plastic Recycling Branch of the China Synthetic Resin Association: Common materials for plastic labels on the market include PO, PVC, PETG and OPS. PVC has a large market share due to its good transparency, high shrinkage rate, and easy tearing. However, due to its poor environmental protection, it will reduce the impact resistance of recycled PET and has been banned in Europe, the United States, Japan and other countries. Heat shrink labels and wraparound labels account for about 45% each, and self-adhesive labels account for about 10%; wraparound labels are easier to peel off from PET bottles than the other two types of labels, and the less coverage of the heat shrinkable label on the bottle, the better;

        Compared to 100% full bottle coverage, 50% coverage is easier to remove. Regardless of the label form or material, labels that are easy to peel off have no impact and are recyclable. For labels that are difficult to peel off and cannot be separated by density method, recyclable design analysis needs to be conducted based on the characteristics of the label product.