What is Thermo Shrinkable Plastic and its purpose
You need some form of closure or stopper when bottling wine, spirits or liquors. A tamper evidence seal is placed on top for inviolability and decoration purposes. This can be in the form of a simple paper strip also referred to as bandrol, a wax seal, a tin or polylaminate capsule. One of the more popular options are heat shrink wraps.
These shrink seals/wraps can be made of various materials such as PVC, PET or PLA. We will review each option in detail below. Once heat is applied to the wraps, they will shrink and form a tight seal that holds the stopper in place when traveling and protects it from dirt and dust.
There are multiple terminologies for this type of application:
- Tamper Evidence
- Heat shrinking bottle capsules
I came into contact with a Belgian startup called “Bostocap“who specialises in stopper and capsule packaging for the drinks industry and seems to be pushing the boundaries when it comes to thermo plastic seals. They helped me obtain the information that I needed to compare PLA bottle caps with PVC and PET options.
Chris Lancksweert (co-founder and head of sales) – “We can help our clients accelerate the transition from fossil to bio-based plastics in this industry. We aim to become the leader in PLA heat shrink capsules.”
PLA – Polylactic Acid
PLA is still in its infancy compared to other plastics. It’s a bio-based plastic made from fermented plant starch. PLA is primarily produced in the US (corn) or in Thailand (sugar cane). It’s rapidly gaining popularity and may become a replacement for certain fossil-based plastics applications.
Advantages PLA Shrink Capsules
- Plant-based – PLA is usually made from 100 % plant based feedstock.
- Carbon footprint – PLA has a lower carbon footprint due to its renewable carbon-absorbing plant origin. The plant absorbs CO2 while growing.
- Sustainability Claim – PLA is perceived as a sustainable plastic because it is made from biobased and renewable feedstock.
- Popularity – There’s a growing interest in PLA as it replies to an ecological drive.
- Similarity – PLA looks, feels and can be handled just like a fossil-based plastic.
- Performance – PLA has a low melting temperature. It has the highest shrink at the lowest temperature and a more gradual shrink curve compared to PET and PVC. Lower melting temperature means less energy and less CO2 production during processing.
- Industrial Compostability – PLA is industrially compostable according to the norm EN 13432. PLA can break down into water and carbon dioxide in a period of 12 weeks in an industrial composting facility.
- Home Compostability – PLA shrink films could be made home compostable by 2022 according to suppliers. Some suppliers claim that certified “Home Compostable” PLA would degrade over a period of approximately 6 to 12 months in a home compost bin or heap.
- Incineration – PLA is said to be one of the plastics that produces the less toxicity (toxic fumes) when incinerated.
- Production process – the production of PLA releases less toxic fumes and uses less energy than other traditional fossil based plastics.
Disadvantages of PLA Shrink Capsules
- Biodegradation – The biodegradation of PLA is a slow process. PLA will not biodegrade in the open environment but needs to be processed by an industrial or commercial composting facility. Should PLA end up in a tightly-packed landfill it could actually take 100 to 1000 years to decompose.
- Composting – Many PLA films are certified to be industrially or commercially compostable. At this point in time, PLA is not yet accepted by most industrial composters.
- Labelling – There’s no specific industry ‘Resin Identification Code’ for PLA. PLA falls under number 7 which is branded “other plastics”. There are European logos called “Seedling” and “OK compost” that tell consumers that the film is theoretically industrially compostable.
- Recycling – PLA is not yet collected and recycled at this point in time. PLA cannot be added to traditional plastic recycling waste streams as it will be considered as a contaminant. One of the reasons may be that PLA has a very low melting point.
- Plastic vs Food – PLA is mostly made from food crops such as corn and sugarcane. Many people believe that food crops should not be used to produce biofuels (fuels vs food) or bioplastics (plastic vs food) as it may reduce food supply and increase the price of food crops.
- Availability – PLA is not yet available in large quantities and may still be considered as “experimental” in this type of application, but it’s technically feasible.
- Convenience – PLA is the less convenient option for this type of application. Industrial operators in this industry prefer to work with PVC and PET. It has probably an historical reason and may be influenced by one’s resistance to change.
- Price – PLA heat shrinking bottle caps are twice as expensive as PVC and 50 % more expensive than PET options.
- Recycled Content – It’s impossible to obtain rPLA at this point in time.
- Colours – PLA is only available in transparent glossy.
PVC – Polyvinyl Chloride
It’s the one of the most widely produced synthetic plastic. PVC is made from fossil based feedstock and has been in the line of fire of many environmental NGOs in the past.
Advantages of PVC Shrink Capsules
- Preferred option – PVC seem to be the industry’s preferred option for this type of application.
- Price competitive – PVC is the cheapest option; cheaper than PLA, PET, Aluminium sandwich foil, pure Tin.
- Easy to print and glue – PVC compatible glues are more performant that PET and PLA compatible glues.
- Thermoformability – PVC has a very good thermoformability. PVC is easier to shrink around the bottleneck than PLA and PET, you need more sophisticated hardware to shrink the PLA and PET capsules (more complex temperature management).
- Colours – PVC is available in several basic colours, PVC can be printed in any color of the Pantone book more easily than PET and PLA who need more solvent based printing inks.
- Opaque – Condensation on the bottlenecks may appear during bottle filling. Opacity of the shrink film is useful to hide this condensation. It’s easier and cheaper to make PVC opaque than PET and PLA.
- Labelling – PVC has its own resin Identification Code; the number is 3.
Disadvantages of PVC Shrink Capsules
- Fossil-based – PVC is made from fossil based feedstock.
- Biodegradation – PVC is not biodegradable.
- Composting – PVC is not industrially or home compostable.
- Toxicity – PVC has a bad reputation and is often considered as one of the most harmful polymers. It is often described as toxic. The reason is because PVC contains a lot of Chlorine and historically we used mercury to source it.
- Recycling – PVC packaging is not recycled. PVC heat shrinkable caps are not accepted in plastic waste bags at this point in time. PVC bottle caps will be incinerated or landfilled.
- Incineration – PVC will generate toxic fumes such as Hydrochloric Acid if incinerated.
- Recycled Content – It’s impossible to obtain rPVC for this type of application. It’s only possible to obtain rPVC (40-50%) for applications in the construction sector (windows, pipes, flooring).
PET – Polyethylene Terephthalate
PET is the world champion when it comes to recycling. It’s Resin Identification code is number 1. The use of PET in packaging applications are mostly for bottles.
Advantages of PET Shrink Capsules
- Recycling – PET bottles have a very good recyclability. They are the most recycled plastic application. PET bottles can close the loop completely: they can be recycled from bottle-to-bottle.
- Biobased – There is a “bio-based” version of PET referred to as Bio-PET; it’s a bio-similar to it’s fossil based twin.
- Superiority – Some consider PET as a superior material. It’s strong and tough.
- Sustainability – PET has a better reputation than PVC when it comes to sustainability.
- Recycled Content – It’s possible to obtain a rPET film (30 % recycled content). It’s almost a phone call away. Recycled PET is much more expensive than virgin PET.
- Labelling – PET has its own resin Identification Code; the number is 1.
Disadvantages of PET Shrink Capsules
- Biodegradation – PET is not biodegradable.
- Composting – PET is not industrially or home compostable.
- Workability – PET is not the easiest material to work with. It has a high melting point and it’s very hard to cut.
- Expensive – PET is 50 % more expensive than PVC.
- Fossil-based – PET is made from fossil feedstock. There’s a bio-based version called “bio-PET” but it’s almost unavailable.
- Recycling – Only PET bottles are recycled. PET shrink films are not recycled and are considered as a contaminant by the recyclers.
- Colours – PET is only available in transparent glossy.
End of Life
PVC Shrink Capsules
PVC shrink capsules for bottles are incinerated.
Most PVC is used in the construction industry while a much smaller part is use in food packaging applications. The most popular PVC food packaging applications are cling films. PVC used in construction can be recycled, but that’s it. PVC food packaging and cling films are not recycled and will be incinerated.
The incineration or energy recovery of PVC has a toxicity problem. PVC contains high levels of chloride and hydrochloric acid (HCL) will be released when PVC is burned. Incinerators need to be equipped with special and expensive equipment to filter these toxic fumes.
PET Shrink Capsules
PET shrink capsules for bottles are incinerated.
PET is the most recycled plastics but only when it comes to bottlesand when we are in Northern and Western Europe (Scandinavian countries, the Netherlands, Germany, Belgium and Switzerland). These countries have a high collection rate through deposit return systems or pre-sorting kerbside collections.
PET films are not a commodity, they’re too expensive compared to PE films and do not have the same technical advantages. PET films are not the norm and are not available enough in large quantities to make the recycling of PET films an economically viable operation. PET films are not recycled; and will be considered as a contaminant by PET bottles recycling operations.
Soft drink producers will require more and more rPET to achieve their recycled content commitment; therefore it is suggested to avoid using rPET for shrink bottle capsules applications.
PLA Shrink Capsules
PLA shrink capsules for bottles are incinerated.
PLA is theoretically recyclable but is currently not recycled at commercial scale. There’s not enough PLA waste to make its recycling economically and operationally viable.
The incineration of PLA shrink capsules generates less toxicity than the incineration of PET and PVC shrink capsules and PLA burns at lower temperatures than PET and PVC. The release of CO2 caused by the incineration of PLA is “atmospherically speaking” neutral. The plants absorbed the CO2 while growing.
PLA shrink capsules are not accepted by industrial composters yet but suppliers are working on home compostable PLA shrink capsules that should become available in the coming year(s).
One of the most frequently used metric to measure the sustainability of a material is “carbon footprint”.
Other metrics include recycling rate and recycled content.
Carbon footprint, recycling rate and recycled content may not always point in the same direction when it comes to sustainability. For instance, glass packaging has a very high recycling rate and will most certainly be recycled into new glass (recycled content) after use but the carbon footprint of glass is very high.
PLA is promoted and perceived as having a much better carbon footprint than fossil based plastics, the reason being that the feedstock of PLA is plant based. Plant absorb CO2 while growing.
There are no logos on plastic heat shrinking bottle caps so it’s impossible for an average consumer to distinguish between PLA, PVC and PET.
In all cases, the heat shrink capsules will be incinerated and this is where PLA becomes the winner. Incineration of PLA will be less toxic, will require less energy and will be “CO2 neutral” atmospherically speaking. Home compostable PLA shrink films may even bring another end-of-life option to the table.
PLA shrink films are the most sustainable option for heat shrink bottle capsules applications and may even become one of the top applications for PLA in the future.