What Do The Numbers Mean On Plastic Bottles?

Most plastic bottles carry a recycling symbol with a number from 1 to 7

which indicates the material the bottle is molded from

Introduction

A question frequently asked of us at Srlon, as manufacturers of bottles is “What do the numbers on plastic bottles tell us?”.

The Society of the Plastics Industry (SPI) introduced the Resin Identification Code (RIC) code system in 1988 that is intended for the identification of materials in recycling waste streams. In reality, while the symbols guide client-sorting where this practice is encouraged/facilitated, the reality is that the recycling industry does not use or sort by these codes but by more reliable and automated methods.

Almost all plastic products bear the general recycling symbol: a triangle formed by three twisted arrows. The number these arrows enclose narrows down the material to 6 broad families and a 7th catch-all for others that are rarely recycled.

In simple terms the symbol informs about the rough classification of polymers used in a bottle. The intent is to  ease sorting in the recycling process. In reality, few if any waste processors sort by use of these symbols.

Srlon is very active in the plastic bottle market, and we see some quite unclear answers to this question so we figured we would clarify it categorically.

Plastic recyclability is a complex issue, and its efficient exploitation is key to reducing[1]  the environmental impact of plastic waste. Knowledge of the strengths and weaknesses of the RIC can empower re-use and safe disposal, so it’s an important issue we will address in detail.

The Implications of Recycling

The numbers on plastic bottles, the RIC, indicate the type of plastic material used to make the bottle. These codes are usually found inside a triangle of arrows and range from 1 to 7. Here’s what each number represents:

1. PET or PETE (Polyethylene Terephthalate): Commonly used for beverage bottles, food containers, and packaging. It is easily recyclable and often turned into fabric for clothing or carpets.

2. HDPE (High-Density Polyethylene): Used for milk jugs, detergent bottles, and other household products. It is highly recyclable and used for making new containers, plastic lumber, and piping.

3. PVC (Polyvinyl Chloride): Found in pipes, shrink wrap, and some toys and bottles. It is less commonly recycled and can release harmful chemicals if not handled properly.

4. LDPE (Low-Density Polyethylene): Used for plastic bags, six-pack rings, some food wraps, and soft, squeezable bottles. It is not commonly recycled but can be repurposed for products like trash can liners and floor tiles.

5. PP (Polypropylene): Found in yogurt containers, straws, bittles and more often bottle caps. It is recyclable and often reused in products like signal lights, battery cables, and brooms.

6. PS (Polystyrene): Used for disposable coffee cups, plastic food boxes, some bottles and egg cartons. It is less commonly recycled and can be used for insulation and other industrial products.

7. Other: Includes plastics not covered by the first six categories, such as acrylic, nylon, polycarbonate and many others. This category can include co-molded and co-extruded bottles and is essentially viewed as non-recyclable.

In reality, only highly pure and good quality sources of 1, 2, 4, 5 and 6 are typically recycled – these are recycled as molding granules for re-use on a meaningful commercial scale with any environmental impact.

It’s also clear that the overwhelming majority of polymers are not uniquely listed in the widely used RIC system. This is in large part because their widespread presence in commercializable concentrations in typical waste streams is absent.

Taking nylon as an example, there are multiple types – nylon6, nylon66, nylon6/6-6, nylon6/9, nylon6/10, nylon6/12, nylon11, nylon12 and more. There is also a strong tendency for additives to be integrated into many polymers in group 7. Additives such as glass and Carbon fiber can be very hard to remove to make high grade recycled material.

Understanding these numbers helps consumers make informed choices about recycling and the potential health and environmental impacts of different types of plastics.

One highlight of success in recycling is in the highly regulated European automotive market, where a strong push towards complete lifecycle materials control is forcing manufacturers to sort and recycle materials to an increasing degree.

In this sector, the various material descriptors added to components are both clear and well understood/used by the recyclers.

Bottles in detail

The overwhelming majority of bottles are made through two manufacturing processes that result in hard to distinguish products;

• The more established and still very widely used process uses an injection molded part that forms a neck/thread for a bottle with a small closed tube attached to it.

This pre-form is then moved from the injection molding tooling to a blow mold, where the tool clamps the neck part and the small tube is heated and blow molded to form the bottle.

This is referred to as Injection Blow Molding, or IBM.

• The increasingly common and more up to date process uses a downwards extruded, open ended tube that has a tool close around it, pinch sealing its end.

This still soft preform or parison is then blow molded to fit the tool, making this closer to a single stage manufacturing method and therefore reducing tooling and processing costs.

This is referred to as Extrusion Blow Molding, or EBM

While both methods are highly effective at turning low cost polymer material into low cost and extremely high quality bottles, EBM is gaining traction as the preferred process for two reasons.

• The first and most obvious is the single stage nature of the process, reducing setup and operational costs markedly, for no loss of quality or precision in the end resultant bottle

• The second and possibly more potent reason for the growth of EBM is that the parison can, with relatively little cost, be extruded in multiple layers, resulting in a bottle that can have markedly improved properties and commercial advantages.

These multilayer bottles can be formed from as many as eleven layers of polymers and adhesives, or as few as three

The selection of bottle materials is driven by technical and commercial considerations, so selection can include;

• Inner and outer layers of polypropylene, high density polyethylene (HDPE), nylon, PVC PET and even polycarbonate

• Innermost and outermost layers can be of different materials.

• Often the inner, food contact layer is ‘virgin’ material and the outer layer is recycled material, to reduce environmental impact and cost.

• A very common mid layer is ethylene vinyl alcohol/PE copolymer as a thin film that enhances gas exclusion/inclusion and potential flavor contamination.

It is on this basis that co-extruded multi material bottles are considered essentially non recyclable to high grade material, in most waste processing chains.

The separation of these layered and varied materials, and the effective identification of them, is essentially impractical by current, mechanical methods. In general, such materials carry a version of the non-recyclable marking;

Many variation of the recycling symbol are used

Technical Details of Recycling

Plastic recycling is currently minimal. Less than 10% is recycled, where the rest ends up in landfill, incineration or in the environment.

With the increasing production/use of plastics, effective recycling methods are essential to mitigate pollution, conserve resources, and stem the harmful  tide of microplastics.

Recycling typically looks like this;

1. Collection and Sorting: Plastic waste is collected from various sources such as households, industries, and public places. The collected plastic is then sorted by type and color. Sorting can be done manually or with automated systems – usually now by optical sorters that use infrared technology to identify different plastic types.

2. Cleaning and Shredding: After sorting, the plastics are cleaned to remove contaminants like food residue, labels, and adhesives. The cleaned plastic is then shredded into smaller pieces or flakes to make handling and further processing easier.

3. Melting and Pelletizing: The shredded plastic is melted and formed into pellets. These pellets, known as nurdles, serve as raw material for manufacturing new plastic products.

4. New Products: The plastic pellets are used to produce new items, ranging from packaging materials and containers to automotive parts and textiles.

There are numerous challenges that make plastic recycling difficult, drive up the recycled material price and the businesses that do it less successful.

• Contamination: Contaminants in plastic waste, such as food residue, mixed plastic types, and uncontrolled additives such as talc, glass fiber etc degrade the reliability of the resulting grades of material.

• Separation Difficulties: Efficiently separating divergent and incompatible types of plastics, especially multi-layered or composite materials, remains a significant challenge excluding these from the recycled waste stream.

• Market Demand: The demand for recycled plastic is relatively small and highly price sensitive, reducing the economic viability of operations. Virgin plastic is often cheaper than lower grade recycled material, due to low oil prices and subsidies.

• Quality Degradation: Recycled plastics often have inferior properties compared to virgin plastics because of poor selectivity in the sorting, random additive variations and contaminants, limiting their application scope.

Plastic recycling is showing signs, at least at the research level, of progressing to a more complete and effective processing;

• Chemical Recycling: This breaks down plastics into their basic chemical components and can handle contaminated and mixed plastics, converting them into high-quality raw materials. This essentially reduces the polymers either to monomers or to a material more akin to crude oil.

• Advanced Sorting Technologies: AI-driven robotic sorters and improved optical sorting will enhance the efficiency and accuracy of separating different plastic types, if the economics justify the CAPEX.

• Biodegradable Plastics: Biodegradable and compostable plastics aims to reduce reliance on traditional plastics and improve environmental sustainability. While many materials are available, their properties are less suitable in many applications, which is limiting their adoption growth rate.

• Regulatory and Lifecycle Costs: In some areas, such as California and Western Europe, government controls are imposing a lifecycle control approach and applying polluter costs that will  in time benefit the recycling sector by shifting the balance of the economics away from virgin material.

Conclusion

The recycling of plastic bottles is a complex market sector that suffers from major difficulties;

• Virgin material is in plentiful supply and at commodity level prices that give recycling companies relatively low profitability. Without subsidy, it is more expensive to recycle at good quality than it is to buy new.

• The deceptive presentation of recycling collection that leads to unsorted landfill or incineration is sometimes exposed in the West, leading to reasonable cynicism.

• Rapidly developing research is leading to new methods for separation/sorting of material waste, to improve the selectivity and quality of recycled materials. But this is a slow process.

• A brake on the capacity of recycling to address the widespread waste problem  has been low demand for the moderate quality and non food grade results from processing.

The recycling sector has begun to be affected by the adoption of co-molded and co-extruded manufacture of bottle and sheet materials, allowing a thin, virgin, food grade layer to be encapsulated in a recycled layer that has no food contact. This is increasing demand for high grade recycled product.

This also increases contamination in the waste stream, as separation is essentially commercially impossible.

If you want to know more about this complex area, please contact us at Srlon so we can help. We have huge experience and we value sharing this without customers, potential customers and interested parties.