Best of plastics: Bioplastics
Monday, October 24, 2016
Note: This is the fourth of a five-part "best of" series covering trends, material/process advances and applications in electrical and electronics, barrier packaging, medical, bioplastics and 3-D printing.
By way of an introduction definition, the term bioplastics is not limited to biodegradable or compostable plastics made from natural materials such as corn or starch. With its low cost and low toxicity, carbon dioxide is an attractive carbon feedstock for the synthesis of polymers.
Bioplastics is also applied to petroleum-based plastics that are degradable; natural-based plastics that are not necessarily biodegradable; and plastics that contain both petroleum-based and plant-based materials that may biodegrade or not.
Bioplastics are distinguished in two categories: bio-based and/or biodegradable.
- Bio-based plastics: The major focus of this material is the "origin of its carbon building blocks," and not by where it goes at the end of product life.
- Biodegradable plastics: The focus here is on a materials "end of life disposal" independent of its carbon source.
Plastics Institute of America
Bio-based raw material source (left), and bioplastics can be bio-based, biodegradable or both (right).
Bio-based content refers to the weight fraction of the total organic carbon in the material that is bio-based. Originally developed for bio-based content determination of products for the U.S. Department of Agriculture (USDA) BioPreferred Program, American Society for Testing and Materials (ASTM) D6866 is a standardized analytical method for determining bio-based content of materials using radiocarbon dating and is widely used in the bioplastics industry.
- ASTM D6866 bio-based content computation only considers total organic carbon content, not product weight.
- The standard does not measure product biodegradability.
Biodegradable products refer to any organic substances capable of being broken down by microorganisms independent of carbon source. Recently, the European Bioplastics Association estimated that of 1.16 million metric tons (mt) global bioplastics capacity in 2011, 58 percent were bio-based/nonbiodegradable. The group predicts bio-based/nonbiodegradable plastics will grow to 87 percent of the estimated 5.8 million mt global bioplastics capacity that will exist by 2016.
Petrochemical-based materials make up the majority of plastics — approximately 280 million tons of plastics produced worldwide. Global bioplastics production capacity will see almost a fivefold increase from 2012 to 2016. Growing from around 1.2 million tons in 2012, the production capacity for bioplastics will increase to a predicted 5.8 million tons by 2016.
By far the strongest growth will be in the bio-based nonbiodegradable plastics group. The composition of bioplastics production capacity is expected to change significantly from 58 percent bio-based/nonbiodegradable in 2012 to 87 percent by 2016.
Drop-in bioplastics — chemically identical to petroleum-derived plastics — are rapidly gaining acceptance at much greater speed compared to other bio-based plastics. Use of these drop-in materials involve much less risk versus unknown novel materials and are compatible with existing recycling streams.
Institute for Bioplastics and Biocomposites (IfBB)
Expanding bioplastics production capacity.
Leading the field is partially-bio-based PET (polyethylene terephthalate), which accounts for approximately 40 percent of the global bioplastics production capacity. This bioplastic is expected to see a 10-fold increase to 80 percent of total bioplastics production capacity in 2016 to 4.5 million tons.
Following PET is bio-based PE (polyethylene), another drop-in material strongly driving bioplastics growth with 250,000 tons, or more than 4 percent of the bio-based production capacity predicted for 2016.
Other drop-ins that have been or are being commercialized include bio-based nylon, polypropylene, polystyrene, polycarbonate, PVC (polyvinyl chloride) and many other traditional plastics. While Europe is the world's largest market for bioplastics, production capacity is growing most rapidly in Asia and South America.
Let's look at some recent noteworthy bioplastic material, process and application developments.
First, bioplastic feedstock advances have produced new plastic bio-based building blocks. A good example here is isosorbide renewable diol. Isosorbide is a biobased chemical made from starch that is a sustainable, nontoxic diol for polymers and can be used in a wide range of applications, including bisphenol A (BPA) — free polycarbonate and bio-based copolyesters.
Although isosorbide, as a derivative of sorbitol, is not a new product, it is one that for a long time was considered too complicated to purify for chemical industrial use. Roquette Frères, a global leader in the starch manufacturing industry, conducted major research and development efforts to develop technology for using isosorbide in the polymer industry.
The company spent five years investigating the use of isosorbide as a renewable diol for various polymers and biopolymers. The company collaborated with Mitsubishi Chemical on its development and commercialization of Durabio, a durable biobased isosorbide polycarbonate that combines the benefits of polycarbonate (PC) and polymethylmethacrylate, or acrylic (PMMA).
Durabio chemical structure (left) and comparison properties (right).
The plastic has excellent optical properties, combined with high-impact strength and bio-based content. Mitsubishi has upgraded its existing polycarbonate facilities at its Kurosaki Plant in Japan and produces Durabio there for global customers with an annual production of 20,000 tonnes.
Next, Novomer has developed technology to produce polypropylene carbonate (PPC) and polyethylene carbonate (PEC) using CO2 as a primary raw material. Based on the co-polymerization of CO2 and propylene oxide (PO) or other epoxides, the polymers can be produced as both thermoplastic polymers and polyols for packaging and coating products.
The company has also developed chain-transfer technology to produce low-molecular-weight CO2-based polyols for thermoset applications that are commercially viable in coatings, adhesives, foams and composite resins. The process uses a proprietary catalyst system that is approximately 300 times more active than previous systems. The catalyst system does not use precious metals and requires simple organic chemistry, which keeps its synthesis costs low.
Proprietary CO2 and CO sustainable plastic feedstock routes.
In the world's first large-scale manufacturing run of PPC polyol, over seven tons of finished product was produced. Scale-up production was accomplished with Albemarle at their Orangeburg, South Carolina, facility using existing Albemarle equipment modified for PPC polyol production. The 1,000-molecular-weight PPC diol was used to accelerate product qualification and adoption in a wide range of conventional polyurethane applications.
Continuing, 100 percent bio-based polyethylene terephthalate (PET) developments are set to accelerate. Around 50 million tonnes per year of PET are produced for conversion into films/bottles for packaging, fibers for nonwovens/textiles and resins for automotive applications. PET is typically made from 15-30 percent monoethylene glycol (MEG) and 70-85 percent terephthalic acid (PTA).
Coca-Cola, Ford Motor Co., Heinz, Nike and Procter & Gamble have formed the Plant PET Technology Collaborative (PTC), a strategic working group focused on accelerating development/use of 100 percent plant-based PET materials and fiber in their products. All five member companies use PET, a durable, lightweight plastic in a variety of products and materials including plastic bottles, apparel, footwear and automotive fabric/carpet.
PlantBottle manufacturing process.
The PTC collaborative is building upon the success of Coke's PlantBottle packaging technology. At this time only the MEG segment is derived from renewable materials. In this case, that means Brazilian sugar cane/molasses ethanol, which is sent to India for conversion into ethylene and then Indonesia for polymerization into PET.
Bio-based MEG, available from several sources, accounts for approximately 30 percent of Coke's bio-based PET. The bio-PET material has the same properties/functions as traditional PET, and can be recycled just like traditional PET.
Coke introduced Plantbottle to reduce its dependence on nonrenewable petroleum while also lowering potential carbon dioxide emissions that result from their PET plastic bottles. The PTC collaborative was formed to leverage R&D efforts of the founding companies to achieve commercial solutions for PET plastic made entirely from bio-based material.
Finally, in durable automotive products, a lightweight crankshaft cover molded from EcoPaXX bio-based polyamide (nylon) has been adopted for diesel engines by the Volkswagen Group. Produced by DSM Engineering Plastics, EcoPaXX is a polyamide 410 based on 70 percent renewable resources derived from tropical castor beans, which don't compete with the food chain.
The material is also certified 100 percent carbon neutral from cradle-to-manufacturing plant gate. In other words, the CO2 generated during its production process is offset by the amount of CO2 absorbed in the growth phase of the raw material — in this case, castor beans.
DSM Engineering Plastics
EcoPaXX's low CO2 generation.
The cover weight is significantly reduced as EcoPaXX is 45 percent less dense than the aluminum typically used.
With terrific mechanical properties at elevated temperatures and excellent toughness, EcoPaXX is an ideal material for the required high performance under extreme use. The tight dimensional specification of the VW version, as well as the high loads it has to withstand, made the challenge of producing it in thermoplastic particularly severe.
DSM Engineering Plastics
EcoPaXX bio-based Volkswagen crankshaft cover.
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