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Source: guukaa - Fotolia.com

Source: guukaa – Fotolia.com

With advances in technical properties and functionality and a growing number of manufacturers, materials and applications, the bioplastics market is emerging from the side-lines. Although we are currently in a period of unpredictability in oil prices and supply, it is recognised that in the long-term industries that have traditionally relied on fossil based feedstocks will need to embrace new technologies to sustainably meet the demands of a growing global population. It is acknowledged that bioplastics will play a pivotal role in the evolution of the plastics industry and ‘The New Plastics Economy’ [1].
Industry is demanding renewable plastics at a level that has not been seen before. Several multinational brands have put sustainability at the centre of their strategies, investing heavily in the research, development and implementation of sustainable materials. They are looking to polymer producers and compounders to deliver new solutions to drive this transformation of their products.
A globally connected and ecologically conscious consumer base is supporting this change. They are challenging industry to use smart technology and materials to deploy our resources in a sustainable way. Purchasing power favours products from sustainable resources. According to a 2013 survey released by the European Commission around 77% of European consumers are willing to pay more for environmentally-friendly products if they were confident that the products are truly environmentally-friendly [2].
Currently biodegradable and biobased plastics represent less than one percent of global plastics production. In 2014, global production capacity amounted to around 1.7 million tonnes. However, there is a growing number of bioplastic materials and feedstocks entering the market. In 2015 European Bioplastics in cooperation with the Institute for Bioplastics and Biocomposites and the nova-Institute [3] presented data that the global market for bioplastics will quadruple to 7.8 million tonnes by 2019. Biobased represents the largest driver with an increase from 60% of global bioplastics production in 2014 to over 80% in 2019.

What are Bioplastics?

The term bioplastics describes an evolving and increasingly sophisticated family of materials. Bioplastics can be biobased, biodegradable or both. A bioplastic that is biobased has some or all of its carbon produced from a renewable plant or animal source such as agricultural crops, trees and algae. ‘Renewable’ is defined as a resource that is readily replaced or inexhaustible.
There can sometimes be confusion between the terms biobased and biodegradable, biodegradability and biobased content are in fact, two distinct features of bioplastics. A common misconception is that “biobased” bioplastics are all “biodegradable”, they are not. A bioplastic that is biobased may not necessarily be biodegradable, and a biodegradable bioplastic may not be biobased. We can therefore categorise bioplastics in three groups, each with their own set of properties and characteristics:

  • Biobased or partially biobased: a bioplastic where a percentage of the content comes from renewable agricultural or biological materials
  • Biodegradable and biobased: a bioplastic that is designed to degrade under compost conditions. Containing renewable content
  • Biodegradable: a bioplastic that is designed to degrade under compost conditions. Based on fossil resources
    Fig. 1: Global production capacities of bioplastics. Source: Hexpol TPE

    Fig. 1: Global production capacities of bioplastics.
    Source: Hexpol TPE

 

Why use Biobased?

There are numerous potential benefits from utilising bioplastics:

  • Biobased plastics help to reduce the usage and dependency on limited fossil resources, which also are expected to become more expensive in the coming decades.
  • Plants absorb carbon dioxide from the atmosphere as they grow. By using these crops to create biobased plastic products, greenhouse gases (CO2) are removed from the atmosphere.
  • As many bioplastics can be mechanically recycled in existing recycling streams, they also have the potential to contribute to an improved LCA (Life Cycle Assessment). They can first be used for products (both as virgin- and recycled materials), then at the end of the product life they can be used for renewable energy generation.
  • Crops for industrial use can be grown in poor soil which is unsuited to food crops, thereby avoiding food crop displacement and improving biodiversity.

Green TPE Compounds

Dryflex Green is a family of biobased thermoplastic elastomer (TPE) compounds. A range of options has been developed containing raw materials from renewable resources that have been responsibly grown. Raw materials can be produced from various renewable sources, these include products and by-products from agricultural that are rich in carbohydrates, especially saccharides such as grain, sugar beet, sugar cane, etc. The biobased content could derive from different raw materials such as polymers, fillers, plasticizers or additives. The Dryflex Green family includes compounds with amounts of renewable content up to 90% (ASTM D 6866-12) and hardness from 30 Shore A to 50 Shore D.
Since Hexpol launched the Dryflex Green TPEs to the market it was seen just how diverse the requirements are for biobased products. While some of the customers have already adopted a ‘green’ strategy and are well on the road to developing sustainable products and practices, others are keen to ‘go green’ but are uncertain what this means and what the options are. The role of the producer is to guide the market to a greater understanding of the possibilities and limitations of biobased TPEs. Many of the advantages with biobased plastics are not inherent in the material alone, but are rather a commitment to the shift to a sustainable circular economy.
Manufacturers also recognise that using renewable resources brings with it a responsibility to ensure that they are managed in an ethical way, without any impact on other global needs. In this regard, Hexpol is working closely with the suppliers to ensure they
operate in a responsible manner with good environmental practices that comply with social and environmental demands. Dryflex Green thermoplastic elastomer (TPE) compounds are biobased. They contain raw materials from renewable resources that have been responsibly grown.Hexpol_

 

Create Materials with high levels of renewable content

One of the key challenges was to develop low hardness TPE compounds with high levels of renewable content, since most biobased raw materials in the market are quite hard on their own. A major challenge has been to develop compounds with high renewable content, low hardness while at the same time maintaining mechanical properties at acceptable levels. As can be seen in Figure 2 the Green series divert from the other soft thermoplastic materials on the market today by including also soft materials with high level of renewable content and thereby covering a greater segment and opening up more design possibilities.
As the requirements can vary greatly for each application, there is a need for highly customised formulations. Rather than a standard grade range, the TPE-producer has therefore qualified a number of raw materials which will allow us to work with a modular system to build a compound that is tailored to customer specifications. The modular system will include options such as:

  • Percentage and type of renewable content
  • Hardness
    Adhesion to polymers, such as PE, PP, ABS, SAN, PET
  • and PLA for 2K multi-component applications
  • Colour
  • Filled or unfilled compounds
  • Mechanical behaviour such as flexibility and tensile properties
  • Price level
  • Surface finish and haptics
  • UV and heat stability

Formel KGK 6

 

The Green TPE compounds display mechanical and physical properties close to and comparable to TPE compounds from fossil based raw materials. What we have also noticed is that some of the biobased materials differ from the typical TPE’s in their haptic behaviour and you can get a material with even higher friction than for standard TPE, especially when wet. In general the compounds show very good bonding behaviour to PE and PP but there are also special grades with good bonding to ABS, PET, PLA compounds etc. Like conventional TPE compounds, Dryflex Green TPEs can easily be coloured to give vibrant and appealing visual impact. For applications wanting a look even closer to nature, organic fillers from plants, crops or trees can be used. These help to give an additional ‘organic’ appearance of products to the end-customer.

Fig. 2: Percentage of Bio-content vs Hardness. Source:Hexpol TPE

Fig. 2: Percentage of Bio-content vs Hardness.
Source:Hexpol TPE

Applications for biobased TPEs

Previously one of the main targets for bioplastics was mass produced single-use disposable items such as food packaging and carrier bags which were seen as the largest environmental offenders. Increasingly there is a push to also look at how bioplastics can be used in more durable items that are used longer-term. Dryflex Green TPE compounds have the potential to support this transition as they can be used in many applications that currently use conventional TPE compounds, such as:

  • Soft-touch grips and handles
  • Sealing and closures for packaging
  • Sports equipment
  • Toys and infant care
  • Soft-touch areas for packaging
  • Tools and hardware

In a highly competitive marketplace, Dryflex Green TPE compounds offer plastic product manufacturers and designers a differentiator, we see that many companies are adding a ‘green’ line to their existing product portfolio.

Fig. 3: The modular System for a customised TPE. Source: Hexpol TPE

Fig. 3: The modular System for a customised TPE.
Source: Hexpol TPE

Biobased Content – Certificates in Detail

Vincotte

  • The specified organic portion must be minimum 30 %
  • The proportion of biobased carbon to total carbon must be minimum 20 %
  • Products can be certified to four different levels depending on the biobased content:
    1 star – 20 to 40 % biobased
    2 stars – 40 to 60 % biobased
    3 stars – 60 to 80 % biobased
    4 starts – more than 80 % biobased [2]

DIN Certo

  • The specified organic proportion must be minimum 50 %
  • The proportion of biobased carbon to total carbon must be minimum 20 %
  • Products that pass the two criteria above can then be certified to three different levels depending on the biobased carbon proportion:
    20 to 50 % biobased carbon
    50 to 85 % biobased carbon
    Over 85 % biobased carbon [3]

How do you calculate renewable content in plastics?

The bioplastics industry needs to make is easy for consumers to identify biobased products and give a clear indication of just how renewable the materials used in the products they buy actually are. The amount of renewable or biobased content of a bioplastic can be reported in several ways, it is for example possible to indicate the ‘biobased carbon content’ or the ‘biobased mass content’. In some ways the renewable content by weight or biobased mass content can seem like the most relevant way to show the biobased content, since this will show the real weight of biomass inserted into the material, however, this can be highly inaccurate since the weight of biomass added to the material consists also of other substances than carbon. Presenting the biobased carbon content however gives a very clear image of the biobased content and can also easily be measured and verified in the finished material. International standards for quantifying the biobased content have been established for the bioplastics industry, the most widely used and accepted by the market is ASTM D 6866-12. On European level there is not yet a standard similar to ASTM D 6866 but a technical specification CEN/TS 16137:2011 “Plastics – Determination of biobased carbon content”.

ASTM D 6866

ASTM D 6866-12 [1] is a standard method for quantifying the renewable content in a material (solid, liquid or gaseous) based on the technique for radiocarbon dating where the ratio of biobased carbon to total organic carbon is evaluated. Radiocarbon dating was originally a method for determining the age of an object containing organic material by using the properties of decay of radiocarbon (14C), however, in this standard method it is being used to evaluate the amount of biobased organic matter in an unknown sample by dividing the 14C activity in the sample by that of a modern reference standard.
The idea behind radio carbon dating is quite straightforward but it has taken a lot of work to determine the 14C content in the atmosphere over the years and then convert this into a calibration curve that can be used to determine the age of an object from its proportion of 14C to 12C. 14C is an unstable isotope of carbon, half-life of 5730 years, created by cosmic irradiation on 14N in the upper region of the atmosphere. Biomass includes, other than the standard 12C, a very small amount of 14C and as long as the animal or plant (biomass) is alive and growing it will remain constant since the levels will be constantly renewed due to photosynthesis (plants) or by feeding on plants (animals). As soon as the plant or animal dies the level of 14C to 12C will start to decrease due to the decay of 14C and since the time it takes for biomass to be converted to fossil fuel is much longer than the time it takes for 14C to decay to 14N there is almost no remaining amount of 14C in fossil fuels.
The ratio of 14C to 12C in a material can then be used to determine the total percentage modern carbon (pMC total), which in turn is used to calculate the renewable content. The measured pMC total can be slightly higher than 100% in biomass due to the increase of 14C in the atmosphere during the nuclear testing program in the 1950s and therefore the pMC total must be corrected by dividing it by 1.05 to yield the true biomass content following ASTM D 6866-12.
Since the method is based on determining the content of modern organic material it can only be used for determining the renewable content in the organic part of the material (pMC organic), this means that it will not take into consideration the possible inorganic parts, e.g. possible fillers, of the material (pMC carbonate). In conclusion, this means that for a material containing inorganic fillers, such as calcium carbonate, this inorganic part has to be excluded from the analysis and it will also not affect the renewable content of the material as measured according to ASTM D 6866-12. Hence, a material with 70 % biobased content will have a biobased content of 70 % according to ASTM D 6866-12 also when filled with 20 % calcium carbonate. In order to get correct results when analysing a material according to ASTM D 6866-12 the filler content (or other inorganics) in a material must be known and accounted for.
The test procedures in ASTM D 6866-12-12 has an analytical error margin of +/- 3 % but due to differences in the age of the biomasses used in the industrial processes the final accuracy of the biobased content will be lower. According to the standard the accuracy of measured biobased content is assumed to be within +/- 5 % given that the products are no more than 10 years old. Since the ASTM D 6866-12 test method is only developed to measure the biobased content of a partly or fully biobased product and doesn’t value the actual level of biobased content, different branch certificates have been developed in order to raise awareness among end customers. Some of the most common certifiers in Europe are the Belgian certifier Vinçotte and the German certifier DIN Certo.

Fig. 4: Carbon 14Cycle

Fig. 4: Carbon 14Cycle

Conclusion

Bioplastics are stimulating the evolution of the plastics industry. They are helping to answer the question of how we will meet growing demand while deploying our resources in a sustainable way. As demand for bioplastics continues to rise, over the coming years we expect to see a lot of activity as feedstocks, processes and technical capabilities continue to be developed.
The Green TPE compounds are delivering mechanical and physical properties close to and comparable to TPE compounds from fossil based raw materials as well as the added quality of being derived from renewable resources. Their combination of low hardnesses with high levels of renewable content are opening up new opportunities for sustainability in the consumer, packaging, medical and construction market.

 

References
[1] ASTM International. D 6866-12 „Standard Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis“. May 2012
[2] AIB-VINCOTTE International s.a./n.v.
OK biobased: Certification Scheme.
April 2013. Edition B.
[3] DIN CERTCO. Certification scheme „Biobased
Products“. s.l. TÜV Rheinland, November 2015.
[4] World Economic Forum and Ellen MacArthur Foundation. The New Plastic Economy – Rethinking the Future of Plastics. 2016.
[5] European Comission. Attitudes of European
towards building the single market for green products. Flash Eurobarometer 367. 2013.
[6] European Bioplastics. Institute for Bioplastics and Biocomposites and the nova-Institute. [Online] 2015. [Cited: 3rd May 2016.] www.european-bioplastics.org.

Über die Autoren

Jill Bradford

Marketing & PR Manager
Hexpol TPE, Eupen, Belgien

 

 

 

Sofie Sandhagen

Development Engineer
Hexpol TPE, Eupen, Belgien