London Celebrates 100 Years of Plastics

It has been 100 years since Leo Baekeland invented Bakelite, and to celebrate this occasion, the Science Museum of London opened a special exhibition this week. Appropriately titled Plasticity – 100 years of making plastics, this exhibition has several interesting displays to showcase the evolution of plastics over the last century:

• Bakelite coffin from wood-flour filled phenol-formaldehyde resin, 1938
• Mold for a Tupperware(R) container, 1965
• Model airplanes with different shapes, some appear to resemble a bird
• Toyota iUnit concept car, 2005. It uses plant-based materials instead of oil-based plastics and metals. Tough kenaf plant fibres are held together by lignin, a natural polymer found in wood.
• GRP Futuro House, 1968
• PVC dress

I am sure there are many more exhibits, this is what I could gather from the web. I hope they are getting a good crowd!

Baekeland was Belgian by birth, but immigrated to USA after completing his doctorate. Most of his inventions happened here in America. So I wonder why this exhibition did not open in an American city.

Certainly, plastics have changed the way we live so much so that we now take it for granted. Here is a nice timeline of plastics that I found on the National Plastics Center & Museum’s website.

Carbon Nanotubes Gaining New Applications In Plastics

New applications of plastic composites based on multi-wall carbon nanotubes (MWNT) are finally emerging according to the cover story in the May 2007 issue of Plastics Engineering. There are three key drivers for this trend:

• New production capacity and lower cost of production (see my post of May 15, 2007)
• Expiration of important patents held by Hyperion Catalysis (for example US patent 4,663,230 issued May 1987)
• A growing number of business and technology partnerships

Two main areas of applications are sports equipment (lighter and stronger composite material) and automotive (static dissipation). Here are a few examples:

• Hockey sticks from the Finnish company Montreal Sports use Baytubes(R) in an epoxy compound. These sticks are reported to be 60 – 70% more impact resistant than carbon fiber composite sticks. According to a page on the company’s website, “Nanotechnology has made it possible to produce a more flexible shaft, which helps the handling of the puck and improves the feel for the game. The most important benefits are the improved manageability and durability“.

• Sailboat mast for the new Synergy 350 RL yacht based on the Nanosolve(R) epoxy-nanotube composite from Zyvex. According to Zyvex’s press release, it replaces a carbon-fiber reinforced fabric bonded together by epoxy.

• Zyvex’s Nanosolve(R) materials are being used in a variety of sporting goods such as bicycles, baseball bats, hockey sticks and golf clubs. According to the Plastics Engineering story, the 2006 US Open winner, Geoff Ogilvy, uses clubs containing Nanosolve(R). See a complete list of Nanosolve(R) applications here.

• Nano In branded nanocomposites from Nanoledge are used in skis called “Nano In Black” from another French company Axunn. These are reported to have better shock resistance and flexibility and are lighter than other brands. Several other applications are under development for Sports & Leisure, Automotive and Aviation sectors.

• Applications in the Automotive and Electronic industries (Reference: paper from Hyperion Catalysis)
  • Fibrils from Hyperion Catalysis are used in the auto industry to dissipate electricity in fuel lines and connectors. Nylon 12 is typically used as the plastic material for these components, to which MWNT is added in low loading levels. Nylon 12 has good resistance to gasoline. Lately, the fuel lines are made of multiple co-extruded layers to comply with hydrocarbon emissions levels according to the Clean Air act.
  • Thermoplastic fenders of high-heat plastic for in-line electrostatic painting in conjunction with steel panels. High conductivity in the plastic part is achieved from these carbon nanotubes.
  • Front Unloading Unified Pods (FOUPS) for transporting silicon wafers from one station to the other are made from engineering plastics such as polycarbonate (PC), polyetherimide (PEI) and polyetheretherketone (PEEK) loaded with carbon nanotubes.

  

• There is also a strong interest in the Aerospace market for nanocomposites of carbon nanotubes. Broadly speaking, carbon nanotubes are considered for use as reinforcements in ultra-lightweight parts. In my research, I came across a presentation from the advanced materials and processing group at NASA (see Enabling Technologies for Aerospace Missions – The Case for Nanotubes). The information in this package is rather futuristic; however it is quite clear that carbon nanotubes are considered to be among the front-runners in the list of available materials. They are expected to enable “radical design changes” by permitting a combination of properties not previously available and multi-functionality for increased efficiency. Among the challenges cited before this promise becomes a reality are inconsistent quality of supply, dispersion issues and limited characterization data for nanocomposites.

 

 

There is enough momentum in the industry, and enough pull in the market, for the technology of carbon nanotubes to eventually mature into a solid, reliable platform. It is only the beginning!

 

 

 

Picket Fence from Recycled Plastic and Wheat Straw

Using recycled Polyethylene (HDPE) from milk jugs and cellulose from wheat straw, a Wyoming company has developed a process to make picket fences that look like wood but have the durability and a maintenance-free benefit of plastic. The latest issue of Plastics Technology reports that Heartland Bioplastics LLC is now marketing its PrairiePicket(R) privacy fence using this process hoping to capture a share of the fast growing residential fence market.

Total US fencing market in 2007 is estimated at $3.3 billion growing at 5% each year, of which 59% is for residential use (2003 note from Dartmouth). Wood and metal are predominant and account for nearly 90% of the sales. Vinyl plastic and wood-plastic composites (WPC) are gaining in popularity although cost remains a major issue. Utilization of recycled plastic and wheat straw should result in lower cost, although I do not know the exact cost of the PrairiePicket fence.

An interesting fact is that one picket (6 ft long by 5 1/8″ wide by 3/8″ thick) takes 12 jugs and that Heartland uses upto 40,000 lbs of plastic a week (See Tom Lacock’s post on Wyospace). Based on this information, I estimate a production rate of about 23000 pickets/week.

Wheat straw is a good source of reinforcement for plastics that melt at low temperatures (less than 200 °C). Good thing is that it is makes up about half of the yield of a cereal crop such as barley, oats, rice, rye or wheat, which means it is available in abundant quantities. Sure, there is a lot of interest in converting the straw cellulose into ethanol as a biofuel, however that technology is in its infancy and only a small amount is produced on a pilot scale. So, there should be plenty of wheat straw available for these applications.

At a 30% loading by weight in polypropylene, wheat straw as a reinforcing filler delivers a modulus of 3.3 GPa, nearly 2.5 times more than virgin polypropylene, and 3-16% incresae in tensile strength and 13 – 48% increae in flexural strength (see paper from the 4th International Conference on Woodfiber-Plastic Composites). However, similar to other filled composites, there is a significant drop in impact strength.

Wheat Straw fibers have an interesting microstructure as shown in this picture. Dr. Vik Malhotra at Southern Illinois University, Carbondale, has been using wheat straw to develop biocomposites for wheat byproduct wallboards. In order to get good reinforcement, it is important to convert wheat straw into fibers of uniform length without causing excessive damage. Heartland, it appears, has developed its own proprietary “dry process” to prepare wheat straw for mixing with recycled HDPE. At 50 – 60% loading, the wheat straw-HDPE composite picket has a flex modulus of 3.3 GPa, similar to the Polypropylene-wheat straw composite described above.

A few more things to keep in mind – it is critical to dry the wheat straw prior to mixing with plastic in a hot extruder. Typically, wheat straw at ambient conditions have about 10 -15% moisture by weight, which must be reduced to less than 1% prior to extrusion. Otherwise, this moisture will steam up and create voids in the final product.

Since wheat straw is a natural material, it can lead to mildew growth. Reportedly, Heartland adds Zinc Borate to prevent mildew. Zinc Borate is also commonly used as a flame retardant in polymers.

Overall, a good use of recycled plastic and a natural biomaterial. Who knows, if you save up enough milk jugs, you might be able to get a free fence!

Bioplastic Converts to Biodiesel After Use

The New York Times reported on this interesting technology on April 9, 2007:

Scientists worldwide are struggling to make motor fuel from waste, but Richard Gross has taken an unusual approach: making a “fuel-latent plastic,” designed for conversion. It can be used like ordinary plastic, for packaging or other purposes, but when it is waste, can easily be turned into a substitute diesel fuel.

Following the original story, several prominent blogs also reported on this interesting technology (See posts on Green Options, Wired Blog Network, Green Brooklyn, FutureSheet). However, it was only recently that I came across this news on the Plastics and Resins blog on CR4’s Chemical and Material Science section, which I must admit, was a fascinating find!

What I find most interesting is that the packaging material made out of this bioplastic can be converted into fuel after it has been already used and rejected. In this way, it provides value multiple times during its life cycle. Not to mention that the original biopolymer is synthesized using a bioprocess from natural raw materials using enzymes or chemical catalysts.

Prof. Richard Gross, who holds the prestigious Herman F. Mark Chair at the Brooklyn Polytechnic University, has been active in this field for many years. As I read his bio on his website, I was delighted to learn that he had worked with Prof. Robert Lenz at UMass, Amherst (I obtained my PhD from UMass in 1998!). Prof. Lenz, of course, is very well known for his pioneering work with bacterial synthesis of PHA’s. In 2003, Prof. Gross received the Presidential Green Chemistry Award for his work on lipase-catalyzed polyester synthesis (see cover story in Chemical & Engineering News, June 30, 2003) via condensation or ring-opening polymerization reactions.

Over the years, Prof. Gross have developed an expertise in enzyme catalyzed reactions such as step condensation and ring opening polymerizations for preparation of aliphatic polyesters. Used extensively in his research is a class of lipase B enzyme called Candida Antarctica (CALB) which is physically immobilized on a macroporous polymer material. Commercially, this enzyme is available as Novozym 435 from a Denmark-based biotech company Novozymes.

Starting materials for such synthesis are hydroxyl fatty acids, which can be derived from plant or animal sources (oils/fats). According to the research summary on Prof. Gross’s website, polyesters prepared by lipase-catalysis from long chain hydroxylfattyacids are strong-tough plastics that offer properties that are intermediate between poly(ε-caprolactone) and polyethylene. Although, not quite in the class of engineering plastics, these materials can still be expected to have moderately good physical properties for packaging applications. If unsaturated fatty acids are used, it is possible to introduce crosslinking in the resulting polyester, which can further improve the physical properties of these materials.

In packaging applications, these materials can be converted into a film or rigid containers depending on their physical properties. Typically, the packaging material is discarded right after the first use. Therefore, a lot of waste is generated from packaging materials. I was surprised to learn from the New York Times story that a soldier generates on average more than 7 lbs of packaging waste per day. That’s quite a lot!

This is where I am impressed by the value of Prof. Gross’s idea. If the packaging material is made from his biopolyester, the trash can be collected and converted into biodiesel using Cutinases, a class of enzymes that catalyze the hydrolysis of the ester bonds in cutin, a waxy lipid-polyester found in the plant cuticle. In this way, the long-chain biopolyester gradually breaks down into smaller alkyl-ester fragments, which at a certain point, separate out of the water mixture as biodiesel! Now it can be used to run diesel generators, for example, to make electricity.

What an excellent idea!

Carbon Nanotubes Still Not A Cheap Material

Stuart Cantrill’s post “A nanotube fix” on nature.com got me interested in looking up suppliers and prices of single-walled (SWNT) and multi-walled nanotubes (MWNT). He noticed an interesting comparison between cost of SWNT and another more interesting chemical on Wikipedia’s entry on carbon nanotubes:

Single-walled nanotubes are still very expensive to produce, around $1500 per gram as of 2000 (compared to marijuana, which generally costs between $10 and $30 per gram, depending on who you know and how sweet the nug is) ……

Although, the Wikipedia entry has been fixed, I was very amused by this comparison!

Anyway, here is what I found through various sources on the web:

• Cheap Tubes Inc (Vermont, USA): SWNT of high purity at $250/g. Appears that the price might be $75/g for a 1 KG order (check out the price list on the website). MWNT’s are much cheaper, around $0.18/g for an order of 1 ton of the industrial grade. Production capacity is 10 – 12 MT/year of MWNT and 1 Kg/month of SWNT.
• Nanothinx SA (Patras, Greece): High purity SWNT at 180 Euro/g and MWNT 10 -20 Euro/g (see price list). Still a low capacity player, although promises to be above 1 MT/year by end of 2007 through a new high-yield process.

Bayer Material Science (Germany): MWNT commercialized under the Baytube(R) brand. According to a February 2007 press release, current pilot plan capacity is 30 MT, however a large-scale plant with 3000 MT capacity is planned.

• Arkema (France): MWNT commercialized under the Graphistrength(TM) brand. Current pilot plant capacity reported to be around 10 MT. Recently announced a joint development deal with Zyvex to utilize their Kentera(TM) dispersion technology to develop various value-added MWNT systems for different applications. Also the sole supplier in Europe of Zyvex’s Nanosolve(R) product line.

Several other selected smaller players are emerging across the world:

• Ahwahnee Technology (USA): SWNT and MWNT
• BuckyUSA (USA): Fullerenes, SWNT ($250-750/g), MWNT ($100-150/g)
• Carbolex (USA): Lower purity SWNT ($50-100/g)
• Carbon Nanotechnologies Inc(USA): Buckytubes, Research grade SWNT ($375-2000/g)
• Carbon NT&F 21 (Austria): 5-10MT of SWNT and MWNT
• Iljin Nanotech (Korea): SWNT, MWNT
• Nanolab (USA): SWNT ($175-2000/g), MWNT ($2.5-700/g). Current capacity of 2MT going up to 20 MT by 2008-2009
• NTP (China): SWNT, MWNT

This is not meant to be the complete list. Nanotube-suppliers.com has many more listings. Similar to all new technologies, the industry is quite fragmented with a large number of suppliers. In time, this will surely lead to consolidation among these suppliers. Already, Cheap Tubes Inc. claims to have the following mission:

We are embracing the commodity status of Carbon Nanotubes. Many of our competitors are unwilling to accept that ultimately CNTs are a commodity. We believe that when a product is a commodity then if features and quality are equal, then price is largest governing factor. We are striving to be the highest volume, lowest cost CNT supplier.

 

Bioplastics Production Capacity Building Up

This week in Cincinnati, at the 2007 ANTEC conference organized by the Society of Plastics Engineers (SPE), I attended a keynote presentation by Professor Stephen McCarthy on polymers derived from renewable resources. According to his information, large-scale commercial production of several bioplastics is finally becoming a reality. Here are the key players in this industry:

• NatureWorks LLC (Cargill) – 140,000 MT of polylactic acid (PLA) capacity at the Blair, Nebraska plant. Product branded as Naturework(R) PLA. Also available in fiber form under Ingeo(TM) brand.
• Telles (Metabolix/ADM) – 50,000 MT of polyhydroxy alkanoate (PHA) capacity at Clinton, Iowa plant to be commissioned in 2008. Product branded as Mirel(TM).
• Novamont – 20,000 MT of starch polymer at Terni, Italy. Product branded as Mater-Bi(R). Also acquired Eastar Bio copolyester technology from Eastman in 2004. Estimated capacity for these copolyesters is 15,000 MT at Hartlepool, UK.
• The Stanelco Group – 15,000 MT of PLA
• BASF -15,000 MT of Ecoflex(R), a biodegradable copolyester at Schwarzheide and Ludwigshafen sites in Germany

Energy Saving Building Panel Containing Phase Change Material

May 7, 2007 issue of the Chemical & Engineering News reports the following:

“DuPont has launched a new building panel called Energain that it says can reduce room temperature peaks by as much as 12 °F…..”

“……A building using Energain panels can cut air-conditioning costs by 35% and heating costs by 15%, DuPont says.”

Energain is a trademark of DuPont.

According to the DuPont press release of April 1, 2007, Energain panles contain a paraffin wax based Phase Change Material (PCM), encapsulated within a copolymer and sandwiched between two aluminum sheets. “The system works by employing the capability of the PCM to absorb and release heat. Simplified, the compound has a melt point of 22°C. During the melting phase it absorbs heat from the room and stores it. When the interior temperature drops, it re-solidifies and releases warmth back into the room. Working in this way, the system can not only minimise uncomfortable temperature peaks by up to 7°C, it can save up to 35% of air conditioning costs (and 15% of heating costs – particularly at night time and mid-season)”.

Having worked extensively with PCMs (see my US patents 6,869,441 and 7,056,335 related to thermal therapy products), I know that a key problem in this technology is proper containment of the PCM and maximizing its weight per unit area. Proper selection of the right PCM is also important to regulate heat flow at the target temperature.

The key to DuPont’s success appears to be a copolymer of ethylene which can hold upto 60% by weight of the PCM without resulting into the “staining effect”, that is it does not leak out when it melts at the target temperature. Based on my research, the PCM is n-heptadecane, a low molecular weight paraffinic hydrocarbon of 17 Carbon atoms, which has a melting point of 22°C.  

According to the Energain datasheet, each panel is about 1.2 m X 1.2 m X 5 mm in size and weighs about 6.5 Kg. Accounting for the weight of the aluminum panels and tape, the “active” material (copolymer and PCM) weighs about 5.7 Kg per panel. At 60% loading of the PCM in the active material, each panel can absorb/release a total of about 240 kJ of energy (latent heat is >70 kJ/Kg) through the melting transition, or about 228 BTU. In other words, the active material in each panel can  provide a “buffer” for this amount of heat to regulate the temeprature at the target of 22 °C (or 71 °F).

To put it in perspective, it is recommended to have a window AC of 6000 BTU/h capacity for a 200 square feet room. Assuming the room has a 8 ft high ceiling, about 33 panels can be installed on three walls and the ceiling to provide the buffering effect against temperature spikes. Assuming an average of 4h of peak sun load during each day, these 33 panels can buffer an average of 1880 BTU/h; which is about 30% of the installed AC capacity.

The above calculation is only a very rough estimate, which does not really account for the dynamic changes in the sun load during the day. However, I just wanted to run some numbers to understand if the estimate of 35% savings on AC costs was realistic.

I think this is an excellent example of using the PCM technology for energy savings in large buildings. There likely is a trade-off between fixed and operating costs which may not work for individual homes. Notice that in the above example, 33 panels will add an extra 215 Kg of load on the supporting structure. In a large building with many rooms, this could be quite significant.

According to the Energain literature from DuPont, a simulation software called CoDyBa is available for architects and engineers to model the exact requirements and benefits of using these panels.

In my research, I found the following materials quite useful:

• Technical papers from DuPont (1, 2)
• Nov 23, 2006 press release
• Article by Raymond Reisdorf (DuPont Engineer) in BSEE

I would like to know more about the ethylene copolymer and the cost of this system. If you have any information that you can share, please leave a comment.

Cool Tools: Google Patent Search

Google has done it again! This time, they have expanded their excellent search capabilities to the US patent database. Although, currently they don’t include patent applications and international patents in their database, you can still search across 7 million issued US patents. Search results are ranked according to the relevance to the keywords used in the search. Advanced search options can be used to setup a complex query.

What I find particularly useful is a summary page for each patent providing all relevant details in a nice 2-column format. With a single click, you can see the patent summary with the picture of the first page, claims, drawings, citations and references. You can even search the full text of the patent for specific keywords. With citations and references easily available, it becomes very convenient to scan the related patents.

Check it out here.

Wireless Power Transmission: A 19th Century Dream Comes Alive In The 21st Century

Recent announcement about development of a plastic wireless power transmission sheet got me interested in this subject (See Plastic Sheet For Wireless Transmission). As it turns out, people have been interested in wireless power transmission since the early 1800’s, when following Faraday’s discovery of electromagnetic induction, Nicholas Joseph Callan developed an induction coil device, which demonstrated that electrical energy could be transmitted and received without wires (See Wikipedia article on Wireless Energy Transfer). Early successes in transmitting power wirelessly over short distances led to transmission of energy over long distances using electromagnetic radiation such as radio waves and microwaves. In the late 1800’s, “Wizard of the West” and “Master of Lightning” NikolaTesla mesmerized people by his remarkable inventions using high frequency alternating current.

At this stage, I could not resist taking a break and lazily scanning the pictures and stories in my copy of the book by Margaret Cheney and Robert Uth (Metrobooks, 2001), “TESLA: Master of Lightning”. What a delightful experience! I also remembered a movie I saw a while back – The Prestige, showing an interesting twist on Tesla’s “magnifying transmitter”, which could magically make a living man disappear in the midst of massive flashes of lightning. Science, Magic and Fantasy – sometimes, the boundaries merge!

Anyway, I digress…

The main purpose of this post is to briefly describe how the 4-layer plastic sheet developed by the University of Tokyo researchers works. I am not an electrical engineer, therefore I don’t claim to understand its circuitry in great detail. However, in simple terms, there are two major parts of this device (See original paper for details):

1. Contact-less position sensing sheet (2 layers)
2. Power transmission sheet (2 layers)

In the contact-less position sheet, the first layer contains an organic FET (Field Effect Transistor) active matrix and the second layer contains a position-sensing coil array of copper wires looped around in a circular pattern. A 91% change in output voltage of the FET is seen when the distance between the receiver coil (part of the electronic device such as a Light Emitting Diode, LED) and the position sensing coil is reduced to 1 mm. In this way, the exact location of the receiver coil is detected.

In the power transmission sheet, the first layer contains a MEMS switching matrix and second layer contains an array of copper wires looped around in a circular pattern for power transmission. When a voltage is applied to the MEMS switch, its resistance drops allowing passage of alternating current to the transmission coils. Power is now transmitted with high efficiency to the nearby receiving coil through electromagnetic coupling. And there you go – you can now light up your Christmas tree!!

I welcome your comments if you can provide more details on how this system works. Get as technical as you want!

As promised in my previous post, I will now dig deeper into the Thin film organic FET’s. Hang in there….

A Closer Look At The Plastic Wireless Power Transmission Sheet

I am quite fascinated by the recent blog posts on a multi-layer wireless power transmission sheet developed by researchers at the University of Tokyo. By now, several blogs have reported on this story. It seems that the original story was posted on Apr 29, 2007 by Tom Geller on the Nature Newsblog (See Plastic sheet delivers wireless power); however in my research, I came across another post from December 2006 in MIT’s Technology Review (See Plastic Sheet of Power). So it appears that this has been going on for sometime. I also liked Roland Piquepaille’ post on his Technology Trends blog (See A wireless power transmission plastic sheet), mainly because it was complete and provided several key references to the works of these researchers.

I liked the pictures of the prototype device, especially the one powering an LED in water with the goldfish. Just for the sake of making my post “memorable”, I want to include it here with full credit to the University of Tokyo researchers (Takao Someya and co-workers) via Nature Material.

Naturally, I am quite interested in learning more about the structure of this 4-layer plastic film device and the technologies used to create the various components in each layer. Over the next few weeks, I plan to conduct more research to develop a better appreciation of this technology. In particular, I am interested in the following areas:

1. Thin film FET design and setup
2. Dielectric layer materials
3. Organic Semi-conductor layer
4. Printed circuits on plastic films
5. MEMS on thin film
6. Device integration

Apart from the opportunity to learn something “cool”, the main reason for my curiosity is the target manufacturing cost of US $100 per square meter. I think that this target cost must come down before this technology can become mainstream so that it can deliver on its promise.

I hope to keep you, the reader, engaged in this journey over the next few weeks. I appreciate your comments along the way. If you like what I write, and would like to offer suggestions on where I should focus more, please feel free to post a comment.