Opinion Natural PHA
Opinion Natural PHA materials The most versatile materials platform in the world? By: Jan Ravenstijn Board member of GO!PHA Advisory board member of AMIBM Meerssen, The Netherlands Guo-Qiang (George) Chen Advisory board member of GO!PHA Tsinghua University Beijing, China We think that natural PHA materials show a much larger application versatility than any other existing material platforms can mimic. The reason for this thought is that natural PHA materials are already used in nature for many purposes and for much longer than the existence of mankind. PHA stands for Polyhydroxyalkanoate of which there can be an infinite number of different moieties. So it’s nonsense to claim properties for PHA, because different PHAmolecules have different properties. Even the well-known polylactic acid (PLA) and polycaprolactone (PCL) belong to the PHA group of materials. However, a number of PHA-materials are naturally occurring materials, like PHB and a number of its copolymers like PHBV, PHBHx, P3HB4HB, PHBO, and PHBD. These materials are not plastics, but are natural materials made and found in nature, like cellulose or starch [1]. These natural macromolecular materials are not made by polymerization, but by enzymatically controlled biochemical conversion of naturally occurring nutrients (sugars, vegetable oils, starches, etc.) and they all have a role to play in nature. These natural PHAs are part of the metabolism in all living organisms (plants, animals, and humans) since the beginning of life on earth. They function as nutritious and energy storage materials, so they are supposed to be used for that purpose. One can call that biodegradation, but one could also call that feed for living organisms in every environment. In addition, they can fully meet a comprehensive combination of end-of-life options, unlike most other material platforms [2]. Today, these bio-benign materials are made at industrial scale, just by mimicking nature. Many manufacturing capacity expansions are planned and built, especially in Asia/Pacific and North America. The materials appear to be excellent candidates for a very large variety of applications in thermoplastics, thermosets, elastomers, lubricants, glues, adhesives, but also in several non-traditional polymer applications like animal feed, cell regeneration in humans and animals, denitrification, and cosmetics for instance. Without further ado, we present a limited number of applications that have been successfully developed and already use these PHA materials: 1.Traditional thermoplastic applications During the past ten years manufacturing companies have invested billions of dollars to develop and build significant capacity to make natural PHA-materials at industrial scale. Simultaneously, applications were developed using these materials, focussing primarily on applications where biodegradability in many environments was seen to be an advantage and added value. Indeed, the natural PHA-materials are feed for living organisms in every environment, so they biodegrade (= carbon conversion to CO 2 ) in every environment, albeit the rate of biodegradation depends on part geometry and external conditions like temperature, humidity, and others [3]. The result of the BioSinn project [4], on request of the German Federal Ministry of Food and Agriculture, describes 25 product-market combinations where biodegradation is a viable end-of-life option. Biodegradability is an advantage when it is difficult or even impossible to separate plastics from organic materials that are destined for home or industrial composting and when it is challenging or (Photo: MAIP) (Photo: Nuez Lounge Bio ® ) 34 bioplastics MAGAZINE [06/21] Vol. 16
prohibitively expensive to avoid fragments ending up in the open environment or to remove them after use. Natural PHA-based end products that are currently in the market are for instance coffee capsules, waste bags, mulch films, clips, non-wovens, film for food packaging, microplastics in cosmetics, and natural PHA coated paper for coffee cups. The last application has also been accepted as recyclable by the paper industry. There are many more application opportunities according to the BioSinn report. Currently, the main challenge is the total global manufacturing capacity of these natural PHA-materials, but many new plant constructions are underway. (Photo: Prodir) That biodegradability is not the only Unique Selling Point (USP) to talk about has been made clear by a compounding company that significantly elevated the science level and knowledge base for natural PHA-materials [5]. They develop new PHA-compounds that are 100 % bio-based, have high temperature resistance, are easy to process, and are tailormade for a large variety of durable applications. This compounding company has developed more than 500 different natural PHA-based formulations from stiff to extremely flexible, thermal resistance up to 130 °C, weather and UV resistance, fast nucleation from the melt, and improved barrier properties, demonstrating that natural PHA-materials can be turned into a new series of biotechnopolymers that can be processed at as fast as or even faster than the currently used polymers in the industry for all conversion technologies currently in use. Today we see compounders using a combination of different natural PHA-materials to make them the only polymers in compounds for film or 3D printing for instance, while they were often used as additives in combination with PBAT or PLA a few years ago. The availability of high molecular weight amorphous and/or very low crystallinity PHA grades (like P3HB4HB with 50 % 4HB or PHBHx with 30 % Hx) offer the opportunity (Photo: Ohmie by Krill Design) to blend low and high E-modulus grades to control properties. Several examples of these so-called bio-technopolymers have been demonstrated and are used in applications for spectacle cases (replacing ABS or PP Talc), pens (replacing ABS), design chairs (replacing GFR-PP), lamps, electrical light switches (replacing PC/ABS), etc. The design chair has an injection moulded core of a 12 kg shot weight made in a 2,500 tonnes injection moulding machine. The chair comes in several colours. Also, some natural PHA-materials with low E-modulus have been developed for use in hot melt adhesives, pressure sensitive adhesives, and laminating adhesives & sealants. So far, the use is still limited due to the low manufacturing Opinion generic picture (Photo: Reef Interest) bioplastics MAGAZINE [06/21] Vol. 16 35
