Polyurethanes |
Polyurethanes | Elastomers Unique Soft Bioplastics Article contributed by Marco Meneghetti, Laboratory & Bioplastics Product Manager Paola Scopel, Technical Development, Polyurethanes API Applicazioni Plastiche Industriali S.p.A., Mussolente, Italy Fig. 3: Examples of hard/soft composite articles In addition to TPE’s, TPU’s and masterbatches API S.p.A. now produces APINAT, the first and unique soft and biodegradable thermoplastic, which is now also available made from renewable raw materials The Apinat family of soft biodegradable thermoplastic compounds has been available since June 2008. These products are recyclable and biodegradable under aerobic conditions in accordance with EN 13432, EN 14995 and ASTM D6400. With the aim of offering a wider range of bioplastic materials that can help the reduction of CO 2 emissions, API has just created a new formula based on renewable raw materials (from agricultural origin). The content of these renewable resources can vary between 15 and 40% of the total components. The product is the result of a more comprehensive R&D project at the API laboratory which leads to the creation of a complete range of polymers derived from renewable raw materials, from non-food sources. Bioplastics such as Apinat can help commercial companies, associations, local municipalities and governments engaged in greenhouse gas reduction to achieve the targets set by the Kyoto Protocol by reducing the whole environmental impact of the products. Bioplastics and Biodegradability It is of the utmost importance to point out once again that bio-based plastics are not always biodegradable and biodegradable plastics are not always biobased. Biodegradability is directly linked to the chemical structure rather than the origin of the raw materials. As a result, there are some special synthetic polymers which are certified as biodegradable: fossil raw materials can be used to produce biodegradable polymers and plastic products (oilbased bioplastics). This distinguishes them from conventional standard plastics which are neither biodegradable nor compostable. (e.g. PE, PP, PS, PET, PA, ABS, EVA or PVC). Further to the question of biodegradation/compostability there are other degradation mechanisms (oxo-degradation, UV-degradation) acting on specially modified plastics with additives (oxo-polymers). Plastics with this kind of degradation mechanism are not biodegradable because it is not scientifically proven that they are completely assimilated by mircroorganisms as an energy source and that they do not leave toxic residues. They do not meet the standards set for biodegradability/compostability (EN 13432/EN Fig.: 1 - Biodegradation 120 100 biodegradation (%) 80 60 40 20 Apinat Cellulose 0 0 10 20 30 40 50 60 70 80 90 Days 44 bioplastics MAGAZINE [05/10] Vol. 5
Polyurethanes | Elastomers Fig. 2: Before degradation Degradation in soil Compost at the end 14995). At present there are no standards or certifications for oxo- or UV-degradable plastics or plastic products. According to EN 13432/EN 14995 standards, in order to be defined as biodegradable the material must degrade by at least 90% within 6 months (180 days). Figure 1 shows the biodegradability of Apinat (Apinat shown in blue, Cellulose - used here as a reference - shown in green). 2. Grades and Properties Figure 2 shows the effect of the biodegradation of an Apinat plate under controlled composting conditions. Apinat behaves in the same way as many other thermoplastic elastomers and does not degrade in air or water. The evaluation of ultimate aerobic biodegradability of Apinat in an aqueous medium by measuring the evolution of carbon dioxide (according to a modified Sturm test, ISO 9439- 1999) gives a value of less than 10% (i.e. non biodegradable). The test is performed at 20-25°C in an aqueous medium containing microbes and mineral salts. Apinat is different from most other biodegradable materials so far available on the market because it is exceptionally soft and is classified as an elastomer (Shore A scale). The hardness is in the range between 55-90 ShA (ASTM D2240) and flexural modulus 45-110 MPa (ASTM D790). It possesses physical and mechanical properties which are very similar to the best traditional thermoplastics and it can be easily processed using all standard equipment for plastics (injection moulding, extrusion, co-extrusion and hard/soft overmoulding). Specific Apinat hard grades have been developed for coinjection/overmoulding applications. These products have a hardness between 35 and 85 ShD (ASTM D2240) and flexural modulus in the range 100-3000 MPa (ASTM D790). The final hard/soft product is completely biodegradable according to EN 13432:2000 and EN 14995:2006 norms (see Figures 3 and 4). Apinat products are generally supplied in neutral colour pellets, however API SpA has also developed Apicolor B, tailormade colour masterbatches for the Apinat range. This is a special series of biodegradable and non-toxic masterbatches which does not contain heavy metals and other dangerous substances, in full compliance with EN 13432 norm. These masterbatches are also compatible with other commercially available bioplastics. 3. A new ‘Green TPU’ API launches a new development in the TPU market, BIO- APILON 52 from renewable raw materials. This new family (not biodegradable) is a bioplastic with a renewable content of between 30 and 60% and can compete with traditional oilbased TPU in terms of quality and processability, opening the green future of plastics. The product range now includes the BIO-APILON 52 DB series, which is a polyester TPU obtained from vegetable oil based polyols. Its hardness is in the range between 40 and 50 ShD (ASTM D2240) and the tensile strength is about 30-50 MPa (ASTM D638). The BIO-APILON 52 TB series, a polyether TPU, is obtained from vegetable oil based polyols. The hardness of this type is in the range between 90 ShA and 50 ShD (ASTM D2240) and tensile strength was measured at 40-50 MPa (ASTM D638). API has been a member of European Bioplastics since 2009. www.apiplastic.com Fig. 4: Examples of hard/soft composite articles bioplastics MAGAZINE [05/10] Vol. 5 45
