A New Class of Polymer that Defies the Laws of Physics

By Frank Rovella

If you find yourself going straight for the technology section every time you get online or open a paper, then you’re not alone. There are a lot of us just waiting for the next big thing, seeking to be awed by some new technological development. The Industrial Space is fertile ground for this enterprise; just take a look at emerging materials technology.  

Unlike automation that has a level of predictability akin to a train that always runs on time; we can see it downrange, hear the tracks rumble, and watch it flash by.  However, materials technology is more like a seismic event, we know it’s coming but no one is sure when or how big it’s going to be.

An example is a recent discovery by the French physicist Ludwik Leibler, who is this year’s winner of the European Inventor Award in the category research.  Leibler along with his team at the Laboratoire Matière Molle et Chimie at ESPCI ParisTech, have developed a whole new class of plastics called Vitrimers. 

"Classified as supramolecular substances, Vitrimers are a derivative of thermoset plastics and exhibit self-repairing characteristics."

What’s really intriguing about Vitrimers is how they do what they do. To understand this, we’ll have to look at the mechanics of their most basic elements.  At the molecular level, the atoms that comprise standard thermosets maintain their crystalline structure through permanent or rigid chemical bonds, the strength of these bonds ultimately determines the characteristics of the material. Flex, friction, and thermal cycles break down these bonds resulting in weakening that leads to cracks and fractures. Once these bonds are broken, they cannot be repaired  However, the molecular bonds that makeup Vitrimers are neither permanent nor rigid; their state is more akin to a dynamic equilibrium. This means that molecular bonds are forming and breaking simultaneously. Regardless of the molecular structure, the number of bonds remains the same. This reaction is thermally activated allowing VItrimers to go from solid to liquid and back with no change in crystalline structure; this is known as a glass transition. These characteristics, in essence, are what make Vitrimers a self-repairing plastic. Testing conducted at the University of Minnesota concluded that fractured samples that were healed recovered 102% of tensile strength, 133% of the original tensile modulus value, and 67% of ultimate elongation. Vitrimers glass-like qualities, allow it to be welded like glass, meaning that if two surfaces are brought to a molten state and welded, when they solidify the molecules are aligned like a solid section, with no seam. This is similar to friction stir welding, but far more complete.

The self-repairing qualities of Vitrimers are paving the way for a number of impressive innovations, and will surely lead to many more.  One of these is in the medical industry, where Vitrimers are being used in what is being called “Organ Glue.” This is a self-healing polymer hydrogel that acts as an anti-hemorrhaging, wound-healing aqueous solution. Vitrimers have the ability to form “nanobridging”, that is a molecular bridging of tissue; it can be used in situations where stitches are impractical.

For the more mundane, however, these same self-healing properties can make a significant impact on manufactured goods. Self-repairing plastics means that products made from it will have a far longer service life. Simply put less material is required because fewer parts are needed to accommodate for wear.

Then there are the effects on recycling, Vitrimers by nature are ideal for recycling because they can be liquefied and solidified over and over. Think about all the plastic that can’t be recycled, they end up in landfills, and some of these plastics can take hundreds of years to decompose fully. Vitrimers could make plastics as recyclable as aluminum.

The concept of materials that self-repair, or do things that seem physically impossible certainly has an awe factor, but Vitrimers are just one example. NASA is currently developing materials that can self-heal after a meteor strike and even self-repairing alloys. As we move forward keep your eyes open, because there is a lot more from this came from.

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A 3D Printing Industry Game Changer… This Time for Sure

By Frank Rovella

If you’ve been holding your breath waiting for 3D printing to change manufacturing as we know it then your face is probably blue, or you’ve already passed out.  For years a succession of technological breakthroughs has emerged but, each time falling short of the ultimate goal. I’ve even heard proponents say that someday we’ll all have 3D printers in the home so we can manufacture our own products on demand. Manufacture what, plastic

silverware, Legos?

The plain truth is that for 3D printing to make any kind of an impact, it will have to displace existing technology and do it economically.

For the most part, 3D printing has been relegated to the world of prototypes, short runs, and hobbyists. These days when I hear about the latest in 3D printing technology I get a little skeptical. However, this time around it includes some big names such as HP and Voxeljet, using phrases like “high-speed, low-cost manufacturing” and the Holy Grail “cheaper than injection molding”.

Today the new savior of manufacturing futurists is called “High-Speed Sintering” which has been in development for over a decade. One of the people behind high-speed sintering technology is mechanical engineering professor Neil Hopkinson, of the University of Sheffield in England. He believes that this really is the way forward for 3D printing. Hopkinson’s entry is based on the layering principals of laser sintering. As its name implies in laser sintering, a laser is used to melt material in thin layers. Though the results can be very precise, the technology is expensive and slow. In Hopkinson’s high-speed sintering approach, the laser is replaced by an infrared lamp and what is basically an ink-jet print head. In this process, the print head moves at high speed layering a polymer powder that is blended with light/radiation absorbing material. As each layer is laid down on the print bed, an infrared light fuses the powder. Hopkinson claims that given a large enough build area high-speed sintering can be 100 times faster than laser sintering, and deliver the same level of dimensional precision. This seems to be where injection molding may finally be impacted. High-speed sintering has no expensive tooling, design changes can be made on the fly, and there is little or no setup, essentially providing manufacturing on demand.

At this point, the technology has proven viable but there are still some hurdles to overcome. The biggest is that because the polymer must be mixed with a radiation absorbing material, it will only work with a limited number of polymers. Although this may be in the early stages, there is a lot of R&D money backing up this technology.

Hewlett-Packard has been working on a similar technology called “Multi Jet Fusion.” In HP’s product, the radiation absorbing powder is called a detailing agent. HP’s Multi Jet Fusion system is already available but is still being advertised for short-run and prototype work. Hopkinson’s high-speed sintering technology is now owned by the German 3D printer manufacturer Voxeljet. Voxeljet certainly has the know-how and resources to make this work, and German engineering can’t hurt either.

So to put it all into perspective, we have an obvious market need and two competing manufactures developing very similar technology. Both have a lot of capital, in HP’s case revenues of over $112 billion a year. Voxeljet, on the other hand, is quite modest in size, but totally focused on the industrialization of 3D printing and proving it with a pretty impressive product line. They are heavy into innovation and manufacture one of the largest commercially available 3D printers. Their VX4000 has a workpiece envelope of 157” x 79” x 40”. HP is certainly the 800-ton gorilla, but I’d put my money on Voxeljet to get this to market first. Their concentration on developing large scale volume manufacturing based 3D print systems is right in line with what this technology is meant for.

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Water, Water, Everywhere, But Not a Drop to Drink

This may not be the Rime of the Ancient Mariner, but it has everything to do with seawater

By Frank Rovella
I read an interesting fact in an MIT publication the other day; they stated that by 2025, 1.8 billion people will have trouble getting clean drinking water; that’s over 20% of the world population. This is a number that until recently has not gotten much attention, however, the recent drought on the west coast has helped to drive it home. Cities like San Diego have been hit the hardest, currently 80% of San Diego’s water supply is imported. This has prompted state and county officials to move forward with a massive $1billion desalination plant. When completed it will be the largest in the western hemisphere.

Desalination is becoming the only option for many metropolitan areas with growing populations and increasingly arid climates. This is highlighted by the fact that since 2000 over 16,000 desalination plants have come online in over 120 countries. Seawater desalination is certainly proving to be a viable option, but it’s expensive. Water produced by desalination is measured in acre-foot units, one acre-foot being almost 360,000 gallons or the estimated amount used per year by two five-member American households. One of the reasons it is so costly is that seawater desalination is based on the Reverse Osmosis (RO) process. It takes a lot of energy to push that much water through this type of system. San Diego, for example, will be paying approximately $2,000 per acre-foot, which 80% more expensive than their current supply. As you can imagine, with that much public money at stake, there is a lot of pressure to reduce costs. Though RO technology has come a long way in recent years due to advances in materials and process control, it still has a long way to go.  To understand why it’s expensive, and why it is a prime candidate for enhancements from process improvements and materials technology, we have to first look at what an RO filter is and does.

The RO process used for desalination typically uses a spiral wound type of RO filter. This configuration is composed of two sheets of membrane that are glued back to back to form an envelope or a leaf. Membrane leaves contain two membrane sheets sandwiching a porous sheet that is the permeate collector. The leaf is glued on three sides; the fourth side is attached to a perforated permeate tube.  In this method, the water can only exit through the permeate tube. While the system is in operation, pressurized water flows over the surface of the membrane on both sides of the membrane leaf. Water permeating through the membrane flows on the permeate carrier to the open side of the leaf, it then exits through the permeate tube.

In large scale RO applications such as desalination, multiple leaves are connected to the permeate tube. It is set up so that the permeate from all of the leaves goes through the same tube. In the multiple membrane configurations, a mesh spacer is placed between the leaves. They are then wound around the permeate tube, hence the name “spiral wound”.

Advances in the understanding of RO flow have brought about design changes that have added higher levels of efficiency. Modern RO filters contain more leaves that are shorter; the decrease in the water path this creates has proven to be far more efficient. This means that fewer membranes and less overall equipment is needed to create even more water. However, this is just one area where improvements have been made. There has been a great deal of advancements in membrane materials, as well as efficiency to feed pumps and general operating systems.

We have to remember that desalination power consumption is very high because of the amount of force required to pump massive amounts of water through an RO filter. The power used for seawater desalination accounts for 20 to 30% of the cost but its far less expensive now than it was. In 1979 1,000 gallons of desalinated water required 114 kWh. Today that same 1,000 gallons needs only 14 kWh.

But solving the world’s water problem will take more than high-tech large-scale filtration of seawater. Its also going to take boots on the ground in areas that can’t afford the colossal outlay for a desalination plant. The 2030 Water Resources Group has been applying some very innovative solutions across the globe to solve water shortage problems, and most of it is through pure efficiency. For example, in a project in Cape Town South Africa, they identified widespread leakage problem that caused the loss of approximately 600,000 gallons per hour. There are also a number of other examples, mostly based around water management for areas such as power generation, groundwater conservation, distribution management, agriculture, and wastewater treatment. There are also a number of other technologies in development that could change the freshwater playing field. Research is currently underway that includes distillation, ion exchange, and biochemical desalination. Whatever the final solution is, if the problem is not solved or at least addressed adequately, fresh water will become a key issue in the years to come.

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