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Pharmaceutical Manufacturing and Packing Sourcer

A Natural Choice

Polymers can be broadly categorised as natural or synthetic in origin, with the latter familiar as elastomers, thermosetting plastics and thermoplastics. Plastics production is one of the largest sectors in the chemical industry and has been dominated by fossil fuel-based feedstock. The Earth has finite resources, hence depletion of this non-renewable feedstock, combined with disposal concerns of plastics to landfill due to a finite capacity for disposal of waste, have contributed to the development of an alternative approach, the so-called biopolymers or bioplastics.

In the US, the 2002 Farm Bill defined bio-based products as commercial or industrial products (other than food or feed) that are composed in whole, or in significant part, of biological products, renewable agricultural materials (including plant, animal and marine materials) or forestry materials. This was subsequently extended to include bio-based intermediate ingredients or feedstocks.

The low environmental impact of biopolymers can be observed at the beginning and end of the product life cycle. In an ideal case, a biopolymer should be made from biomass and at the end-of-life be biodegradable, returning to the soil to commence the process again. However, in reality, biopolymers can be categorised as polymers based on renewable resources, or as biodegradable polymers. Products from the first class do not necessarily have to be biodegradable, just as those from the second do not necessarily have to be based on renewable resources (1).

Apart from being a renewable resource, other environmental benefits resulting from the selection of biopolymers can include: a reduction in CO2 emissions; an improvement in waste management; and, potentially, biocompatibility. Biotechnological approaches are being increasingly recognised as a key to developing lower cost biopolymers, ensuring they have an adequate life span for applications, and better biodegradables where environmental degradation can involve enzymatic pathways and microorganisms, such as bacteria and fungi, or chemical pathways, such as hydrolysis. Key biopolymers include the following (2):

Natural Biopolymers

Carbohydrates (cellulose, starch, chitin); tannins (polyphenolic plant products); cashew nut shell liquid; rosins (from tree sap); lignin (from wood); protein; polyesters synthesised through the fermentation of microbes which serve as the carbon sources and energy reserves such as polyhydroxyalkanoates (PHA). Due to the different monolithic structures of PHA, it can be further developed into numerous polyester varieties, including the short-chain monomer PHA, the long-chain monomer PHA, and even some copolymers composed of monomers of different kinds. So far, several kinds of PHA have been manufactured through mass production, including polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

Synthetic Biopolymer/Biodegradable Polymers

Polylactic acid (PLA); polycaprolactone (PCL); polybutylene succinate (PBS); polyvinyl alcohol (PVA).

Bio-Based Conventional Polymers

PE/PP polymerised by the monomer derived from bio-ethanol derived from biomass produced by fermentation of plant materials; polyurethane synthesised by plant oil-based natural monomers; polyester made from bio-derived raw materials.

Materials suppliers have been developing new and enhanced grades with improved processability and enduse properties, which could help these materials to advance into a wider range of applications. Biopolymers can be modified with plasticiser(s) and other additives as appropriate to overcome processing and performance limitations, producing commercial materials which can be processed using existing equipment by conventional extrusion and moulding techniques, as shown in Table 1.

Obviously all polymer resins require some care in processing, however for biopolymers, particular attention may need to be paid to the source of the material, for example with starch materials from a different plant variety, growing places which tend to have different composition (amylose and amylopectin) and crystallinity; these will affect the conditions used for the processing.

Table 1 illustrates that the majority of PLA consumption is in packaging applications. Moisture sensitivity of biopolymers can be tackled by various surface treatment approaches to enhance the moisture resistance and water vapour barrier properties – factors which are vital to this sector.

Biodegradability and Compostability

There is a general understanding that discarded conventional plastic packaging, such as films and carrier bags, will endure in the environment for many years. This is clearly an issue for those items collected as refuse in terms of increasing requirements for landfill sites, potential damage to wildlife, and the unsightly nature of these items left as litter. To counter these issues, there is a movement to manufacture packaging products which will have significantly reduced lifetimes once discarded as waste. Therefore, consideration is given to biodegradability and compostability.

The use of terms such as biodegradable and compostable without reference to acknowledged standards can be misleading; some standards are shown below:

Aerobic Biodegradation in Soil

The degree and rate of aerobic biodegradation are determined by measuring the evolved carbon dioxide as a function of time that the plastics are exposed to soil under laboratory conditions (ASTM D 5988 (3); ISO 17556 (4)).

Aerobic Biodegradation by Composting

The degree and rate of aerobic biodegradation are determined by measuring the percentage of conversion of carbon in the sample to carbon dioxide under controlled composting conditions (ASTM D 5338 (5); BS EN 14995 (6)).

Anaerobic Biodegradation under Simulated Landfill Conditions

The degree and rate of anaerobic biodegradation are determined by measuring the biogas production (CH4 and CO2) and the percentage of conversion of carbon in the sample under simulated landfill conditions (ASTM D5511 (7), ASTM D5526 (8), ISO 15985 (9)).

Fully biodegradable synthetic polymers, such as PLA and PCL, have been commercially available since 1990, with degradability improved by blending starch and used in, for example, packaging film applications. Unfortunately, without modification, the mechanical strength or thermal resistance properties of these blends have been limited. Modification can be by the addition of natural fibre reinforcements, such as sugar cane bagasse and jute, or by creating polymer alloys with a renewable resource content; PLA/polycarbonate or PLA/polyethylene grades are available, for example. Such alloys aim to balance renewable content with other required properties.

Commercially, biopolymers can be relatively expensive and are available only in relatively small quantities. This has led to some application limitations to date. However, there are signs that this is changing, with increasing environmental awareness and more stringent legislation regarding recyclability and restrictions on waste disposal.

The ‘green’ credentials of products can be certified to provide credibility and to show that it meets a set of ‘green’ criteria for a recyclate content, bio-based content or both. Globally, there are several schemes which aim to increase purchase and use of bio-based products: for example, USDA BioPreferred in the US and Viçotte in Europe.

Pharmaceuticals Packaging

Biopolymer development has serviced many industry sectors including packaging applications for bottles, jars, bags, films and trays. While offering the environmental advantages, usage has been restrictive with some materials in terms of properties, such as relatively high cost, availability and low softening temperature.

Pharmaceuticals packaging is not the largest segment of consumer packaging, but it is dynamic, innovative and growing within developed markets due in part to the aging population’s need for medication. Consumer needs and purchasing power fuel packaging innovation, which leads to development of new materials and creative packaging design, in consideration of, for example, quality, safety and sustainability. The latter is becoming a principal driving force within the packaging industry (see Table 2); thus, use of renewable materials, recycling of packaging materials and design to reduce the amount of packaging required all improve the packaging’s environmental credentials by reducing the environmental load.

From a consumer’s perspective, price and quality of a product are priorities. However, once satisfied, their concern for the environment becomes a focus, and packaging can become a key differentiator, with surveys showing that consumers are responding to packaging from renewable sources and energy use (10).

As the principal pack material for pharmaceuticals is plastic, replacing glass in many applications, use of packaging based on biopolymers can be one route to attaining such environmental credentials. The EU Packaging Directive 94/62/EC defines packaging as: “all products made of any materials of any nature to be used for the containment, protection, handling, delivery and presentation of goods, from raw materials to processed goods, from the producer to the user or the consumer” (11). It gives descriptions of three packaging categories as part of the definition: primary packaging (or sales packaging); secondary packaging (or grouped packaging); and tertiary packaging (or transport packaging). There is therefore opportunity to apply biopolymer material developments to such packaging.

PLA- and PHA-based barrier materials are being developed for paper and board packaging in various sectors, including pharmaceuticals, driven in part by the UK's Packaging Waste Regulations to develop more environmentally friendly and recyclable materials. Traditional polymer laminates are not sustainable or renewable, but they are recyclable. They do not rapidly biodegrade but do offer barrier performance. Hence, there are opportunities for biopolymer barriers used on paper and board to replace existing polymer emulsions (10). It could be considered a ‘green’ material made from natural and renewable materials, just like the paper itself.

While biopolymers are used in general packaging applications, catering products, agriculture medical applications and so on, the market drivers for the further exploitation of biopolymers include:

  • Cost reduction (influenced by increasing oil costs)
  • Competition with food resources
  • Productivity improvement (development of catalytic processes/monomer production)
  • Physical properties enhancement
  • Lack of products and quality standards
  • Difficulty in separation of biodegradable plastics from mixed plastic waste

Future Outlook

Some areas of future general packaging developments are presented in Figure 2, in which biopolymers have featured and are anticipated to grow. Compared to 2010 data from European Bioplastics, the global production of bio-based commodity plastics is estimated to almost treble by 2015 to one million tons, and biodegradable plastics almost double to 700,000 tons.

Packaging growth in the pharmaceutical sector is anticipated in a number of areas in which biopolymers can play a role. There are also trends toward more complex packaging and higher standards of production, which in turn brings added value to the packaging: for example, smart packaging, safety, compliance, convenience and regulatory constraints on manufacturing (10).

With packaging, it is important that the product and the packaging are considered together in any development. Pharmaceutical packaging can be considered to deliver multiple functions, which include physical protection, product conservation from production to use, security, convenience, barrier protection, containment or agglomeration, dose application and information transmission.

Use of bio-based polymers appears to be considered a priority to reach future sustainability objectives, together with weight savings and recycling. However, it remains a market with a number of uncertainties, primarily with a financial cost. While there are clearly opportunities for biopolymers in the pharmaceutical sector, selection of packaging materials must satisfy all the necessary performance requirements, environmental issues being only one area of consideration.

Conclusion

There are many challenges to full-scale commercialisation of biopolymers, including competition with inexpensive commodity polymers, poorer performance in functional packaging and the requirement for an infrastructure and capital investment for disposal. New barrier materials are being developed that use natural products such as whey protein, wheat gluten and starch that offer excellent gas and other barrier properties. These products can be coated or laminated onto paper, PLA or other materials to improve the biodegradability of a package. There is an interest in multilayer bio-based materials where coated or laminated paper represents a potential market for biodegradable plastics. Biopolymer barriers could come into effective use for paper and board, replacing the polymer emulsions traditionally used. If a package can be considered to be environmentally friendly because it can either be recycled or biodegrade then it would be seen as a green material made from natural and renewable materials, just like the paper itself.

References

1. Tiwari A et al, Biotechnology in Biopolymers Developments, Applications & Challenging Areas, Smithers Rapra, 2012

2. Johnson RM, Mwaikambo LY and Tucker N, Biopolymers, Smithers Rapra Review Reports, Vol 14, No 3, Report 159, 2003

3. ASTM D 5988 – Standard test method for determining aerobic biodegradation of plastic materials in soil

4. ISO 17556 – Plastics – Determination of the ultimate aerobic biodegradability of plastic materials in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved

5. ASTM D 5338 – Standard test method for determining aerobic biodegradation of plastic materials under controlled composting conditions, incorporating thermophilic temperatures

6. BS EN 14995 – Plastics, evaluation of compostability, test scheme and specifications

7. ASTM D 5511 – Standard test method for determining anaerobic biodegradation of plastic materials under high-solids anaerobicdigestion conditions

8. ASTM D 5526 – Standard test method for determining anaerobic biodegradation of plastic materials under accelerated landfill conditions

9. ISO 15985 – Plastics – Determination of the ultimate anaerobic biodegradation and disintegration under high-solids anaerobicdigestion conditions – Method by analysis of released biogas

10. Helander F, Packaging Technology to 2020 (e-book), Smithers Pira, 2010

11. European Parliament and Council Directive 94/62/EC of 20th December 1994 on packaging and packaging waste


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Michael Lock is a Principal Consultant at Smithers Rapra, where he has been supporting a variety of customers in material selection, failure diagnosis, technical review and product testing. Michael also provides general polymer support, helping the company to remain at the forefront of polymer testing and consultancy. This capability is rooted in extensive previous experience, both in polymer R&D and as a technical manager for a packaging supplier in the plastics manufacturing sector.
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