Opinion Picture [M]:
Opinion Picture [M]: bioplastics MAGAZINE Is All ‘Non-Bio‘ Plastic Bad? Bioplastics are just plastics with special features By Igor Čatić retired Professor of the Faculty of Mechanical Engineering and Naval Architecture of the University of Zagreb, Croatia Plastic is based on natural resources Many journals and magazines, even newspapers, are full of words starting with ‘bio’, such as bio-fuel, bio-plastics, bio-cosmetics and so on. This leads to the question: Is all ‘bio‘ a universal solution for all of the problems surrounding climate change, famine in the world, and ‘using food as a weapon’? Or why are we are all horrified when we hear the words ‘plastics made from fossils raw materials’, ‘crude oil, natural gas or coal’. And must we all be delighted with bioplastics made from (cultivated, man-made) biomass, as suggested by one Italian manufacturer in a huge advertising campaign showing a horrified looking lady asking “Still using plastic?” The engineers must choose the optimum material Why do I demand that my students attend lectures? Spoken words can’t be fully replaced by written text and I have an example for this: In the first lecture on ‘Materials’, which I visited as a freshman back in 1954, I learned one thing for life: “The engineers must choose the optimum material for a given purpose (not necessarily the best or most expensive)”. Today, based on my experience I would like to add: “The optimum choice means taking into account technical, economic and social goals, even spiritual ones”. But this choice should not be influenced by marketing, particularly by some kind of eco-marketing with questionable goals. In my opinion agricultural (cultivated by man) products are not natural ones. I distinguish between ‘nature’ and ‘culture’. Examples are mushrooms pick-up in forests (‘nature’) or cultivated in caves on wadding (‘culture’). Polymers and non-polymers First we need to define some terms. ‘General Technology’ is a common name for natural technology and man-made (artificial) technology. Only the products of natural technology are natural products. All those made by man or with the help of man are cultivated (artificial) products. 44 bioplastics MAGAZINE [04/11] Vol. 6
Opinion Having this in mind, I would like to suggest and discuss a new systematisation of materials. We all learned in school for centuries that there are two main groups of materials, i.e. metals and non-metals. Recently, some colleagues and I proposed a new systematisation: polymers and non-polymers [1]. This idea for this new differentiation of materials comes from the basic definition of polymers. The name polymers is an umbrella term for natural and synthetic substances and materials with the basic component being the system of macromolecules, i.e. macromolecular compounds with repeating units (‘polymer‘ from the Greek: poly = many, meros = particle) [2-4]. Based on this definition it is possible to differentiate four basic groups of macromolecular compounds (level L2, see Figure 1). Polymers and nonpolymers can be organic or inorganic. In the following, we will only look at Column C of Fig 1 ‘Natural Organic Polymers’ and read the table from bottom to top. First I would like to mention that the natural organic polymers are the results of natural technology: basic polymers (L2) such as proteins; biopolymeric organisms (microorganisms, L3), phytopolymers (e.g. wood, L4) and animal polymers (e.g. natural pig, L4). On L5 we find non-living organic products such as crude oil or natural gas, and living organic natural products. Then we come to artificial (man-made) technology. Simplified, on level L6, plastics and rubbers (e.g. PE, PVC, PS, UP, PUR = fossil plastics) can be the results of organic synthetic polymers from non-living (fossil) sources or chemically modified biopolymers (bioplastics) from living natural or cultivated sources (e.g. PLA, PHA or even bio-PE). Bioplastics are also man-made organic polymers Bioplastics are a form of plastics derived from renewable biomass sources, such as vegetable oil, starch or microbiota, rather than fossil fuel based plastics which are derived from petroleum. Some, but not all, bioplastics are designed to degrade (see glossary on page 52) If we have a closer look at this definition above, we see that bioplastics are also man-made materials. So what is the difference from fossil based plastics? It is the input into the process. In bioplastics the input is man-made (cultivated) renewable biomass, and not really ‘natural’ products. Some wrong terms According to the descriptions in column C of Fig 1, the term wood-polymer composite is wrong*, because wood as a plant consists of organic polymers (cellulose and lignin). So this composite should be called, for instance, wood-polypropylene composite. Because we also have today hybrid materials such as protein with organic or even inorganic polymers and we should write the names of both components (L7). We use in our processes ever more and more microorganisms. These microorganisms also consist of organic polymers (L3). bioplastics MAGAZINE [04/11] Vol. 6 45
