MIT Makes Strides in Future of PHA-Based Biopolymers

By: Lilli Manolis Sherman 17. November 2016

Researchers identify key enzyme that can be tweaked to make it more industrially useful.


Biopolymers like PLA and PHA are here to stay and expected to continue to evolve. The latter, polyhydroxyalkanoates or PHAs, are linear polyesters produced in nature by bacterial fermentation of sugar or lipids. Produced by the bacteria to store carbon and energy, PHA can be combined with a large number of different monomers to produce biodegradable plastics with varying properties.


PHAs generally have had more of an uphill battle in terms of commercial advancement, with companies such as Metabolix, Woburn, Mass., recently exiting the business with its sale to Korea’s food and bioengineering conglomerate CJ CheigJedang. In the last couple of years, Metabolix had shifted its focus to promoting it amorphous PHA (a-PHA) for use as a performance additive for PVC and PLA.


In contrast, MHG, Bainbridge, Ga., became the world’s largest producer of PHA biopolymer with the startup of its first commercial-scale fermenter last year. Initial capacity for Nodax PHA is 30 million/lb/yr, though at full production, the plant is capable of twice that volume. The company’s PHA-based resins, which include hybrids such as PHA/PLA, have been targeted for use in such articles as: bottles for beverage, personal care and household products; food packaging and service items such as cups, lids, containers and utensils; bags for shopping, trash collection and composting; agricultural mulch and fishing lures; healthcare bandages, tubes and syringes.


Now MIT chemists have determined the structure and mechanism of the PHA synthase enzyme, present in nearly all bacteria which use it to produce large polymers that store carbon when food is scarce. The bacterium Cupriavidus necator can store up to 85% of its dry weight as these polymers.


And the key is that the PHA synthase enzyme produces different types of polymers depending on the starting material, usually one or more of the numerous variants of a molecule called hydroxyalkyl-coenzyme A, where the term alkyl refers to a variable chemical group that helps determine the polymers’ properties. Some of these materials form rigid plastics, while others create softer and more flexible plastics or ones that have elastic properties, which are more similar to rubber—all very similar to petroleum-based thermoplastics but with biodegrability.


The MIT team notes that PHA synthase is of great interest to chemists and chemical engineers because it can string together up to 30,000 monomers, in a precisely controlled way. “What nature can do in this case and many others is make huge polymers, bigger than what humans can make…and, they have uniform molecular weight, which makes the properties of these polymers distinct,” says JoAnne Stubbe, the Novartis emeritus professor of chemistry and a professor emeritus of biology, who along with MIT professor of chemistry Catherine Drennan, are the senior authors of the study, published in last month’s Journal of Biological Chemistry.  


It appears that these two, along with other chemists, have aimed to identify the PHA enzyme’s structure for over 20 years, but it had, until now, proven elusive because of the difficulty in crystallizing the protein. Crystallization is a key step to performing X-ray crystallography, which reveals the atomic and molecular structure of the protein.


Crystals at hand, the MIT researchers collected and analyzed the resulting crystallographic data to come up with the structure. The analysis revealed that PHA synthase is made up of two identical subunits, which form what is known as a dimer. Each of them has an active site in which the polymerization occurs—this debunked an earlier proposal that the active site is located at the dimer interface.


Also key in this analysis is that the enzyme has two openings—one, where the starting materials enter, and another that allows the growing polymer chain to exit. Says Stubbe, “The coenzyme A part of the substrate has to come back out because you have to put in another monomer…there are a lot of gymnastics that are going on, which I think makes it fascinating.”


The next step, according to Drennan, is to try to solve structures of the enzyme while it is bound to substrates and products, which ought to result in more information critical to understanding how it works. “This is the beginning of a new era of studying these systems where we now have this framework, and with every experiment we do, we’re going to be learning more.”


While the structural information that resulted from this work will have little impact on the cost of producing PHA polymers, the researchers see potential for the production of new and improved materials with unique properties. 


Tampoprint Shined at K 2016

By: Lilli Manolis Sherman 11. November 2016

With its 60 years of experience in machine engineering, Tampoprint belongs among the innovators of the pad-printing industry, according to founder and chairman Wilfried Philipp.


The company went to K 2016 to introduce four new concepts for the pad-printing process, which is projected to increase in demand 4-5%/yr in the coming years.


Said to be the first of its kind is the patent-pending Continuous Circular rotation pad-printing system. This new machine enables the continuous decoration of cylindrical parts, making the printing process significantly more efficient and productive. According to Tampoprint, it is well suited for a range of applications from cosmetic packaging to writing utensils to technical mass-produced articles. Better quality and high precision are claimed and multicolored printing is possible. The unit’s output is up to 15,000 parts/hr.



Another new machine concept launched and demonstrated by the company was Module One, a semi-automated modular design developed for small and medium batch sizes. The central element of Module One is formed on a base frame, which can be assembled flexibly. Module One has eight stations and can be outfitted with up to three machine satellites. Pad printing units are selected from the company’s Series Hermetic and Sealed Ink Cup E. The remaining positions can be independently outfitted; for instance, with intermediate drying, infrared drying and part recognition.



With a maximum three-color print image and a maximum diameter of 125 mm, this system is suitable for a range of applications including toys, electronic housings, and household appliances. Construction and installation are reduced through standardization of all assemblies and ancillary options, according to the company. Significantly shortened setup times are claimed.


The company also showed the new variLEX 8130T pre-press laser system for graphics. It was developed by Tampoprint’s technology partner SPGPrints of Austria, a leading supplier of digital imaging technologies. This system is developed for direct engraving/ imaging black pad-printing plates—essentially replacing the conventional photopolymer plates. In combination with the black pad-printing plates, this system reportedly allows an optimal workflow which eliminates the use of any film-making (the photopolymer plate process), exposing, washing or drying.



The variLEX 8130T is also said to reduce tolerances and possible errors, which increasing quality. This system is capable of engraving high-quality line-counts, making it suitable for all pad-printing applications. SPGPrints says, it developed its laser system to image the needed relief-depth in one shot, resulting in smooth slopes, which in turn ensures an optimal ink release. Engraving time for three plates (100 x 220 mm) is 10 minutes with an engraving depth of 25-45 µm, both depending on imaging parameters and design, with up to 5080 dpi resolution claimed.


Finally, designed to work hand-in-hand with the cliché laser veriLEX 8130T, Tampoprint showcased the new “Do-It-Yourself” Intaglio laser cliché, said to deliver unrivaled pad printing results. The user creates the Intaglio laser cliché, fast and operator free, with the veriLEX 8130T. The user fastens the cliché on the magnetic drum, loads the print image on the PC and engraves. Here’s how it works: point by point the smallest cells are engraved in the Intaglio laser cliché. Each of them very precise, with different depths and widths. The pad printing ink can be precisely printed in different shades. Up to 30,000 prints in a contour sharpness can be achieved.

Novel On-Line Rheometer; In-Line Molding Specimen Device

By: Lilli Manolis Sherman 10. November 2016

Two major suppliers of extrusion and/or in-line process testing/monitoring equipment showcased novel systems at K 2016.


• Brabender has its new SpeciMold injection molding specimen device designed for in-line continuous extrusion processing. It takes a stream of material and injects it into the mold to make nearly all of the physical testing bars, including, tensile, impact, HDT/Vicat, flexural, and spiral flow. It is also well suited to molding color masterbatch samples to make sure the colorant disperses well and for ensuring the color match is correct for the intended customer.



A key advantage is that this device provides first-pass information in thermal history and process efficiency. Moreover, in addition to Brabender extruders, it can be used with other extruder brands smaller than 30 mm. It features its own control panel, which monitors temperature and pressure.


• Dynisco has expanded its online rheometry portfolio with the launch of a novel, simplified and lower price-point rheology device—the new ViscoIndicator online rheometer. It is specifically designed for the thermoplastics compounding and processing industry. It provides continuous measurements of the melt flow rate, apparent viscosity, or intrinsic viscosity directly on an extruder.



The unit sells for about $32,000 vs. larger units which range from $71,000-$108,000. The main differentiation between this compact unit and its larger counterparts is that it only provides an indication of whether the process is going off specification. It includes a control box that's mounted on the outside of the extruder and a sensor, which is about the size of a shoebox.


The ViscoIndicator’s single plug-in-power connection and ability to screw into an existing 1/2-20 process connection reportedly allows users to be up and running in no time without modifications to an extrusion line. This, in combination with its simple-to-use Windows 10 IOT HMI is said to minimize the learning curve.

New Film Resins’ Performance Demonstrated by Several Equipment Makers at K 2016

By: Lilli Manolis Sherman 3. November 2016


Take a look at a video discussion between ExxonMobil Chemical and W&H on processing the new Exceed XP resins.


I had the opportunity along with my colleague Heather Caliendo to meet with ExxonMobil Chemicals’ experts on the company’s new Exceed XP family of high-performance LLDPE resins, produced with a proprietary catalyst. Four grades of this family were first launched at Chinaplas in April and two more were unveiled at K. 


We found it impressive that eight major equipment manufacturers were demonstrating these materials and their processing technologies. Among them was Windmoller & Holscher (W&H), which was running an Exceed XP food packaging film grade using quick change-over technology with ExxonMobil’s Enable 4020 performance polymer collation shrink film. Take a look at Heather’s video with ExxonMobil Chemicals’ Larry Gros, global polymers product & applications development manager and W&H’s Martin Backmann, division manager R&D extrusion equipment discussing the new polymers.


Following this video, Gros and his team gave me the opportunity to meet with Alex Dam, executive v.p. of Thanh Phu, a leading Vietnamese manufacturer of laminated flexible packaging. This very savvy processor has aimed to address the market’s demand for a more recyclable alternative for laminated packaging.


In collaboration with ExxonMobil experts, Thanh Phu first produced a package that can be recycled in the same collection stream as PE by using Exceed XP and Enable mLLDPE polymers and their proprietary film conversion technology. “This is a true synergy between material science and conversion technology innovation. We have changed the cradle-to-grave cycle into a more responsible cradle-to-cradle concept…out aim is to have a full PE alternative to conventional laminated solutions without compromising performance, while maintaining an attractive cost-efficiency ratio.”


Dam told me that his plant is outfitted with the latest processing technology including W&H’s Varex II 3-layer with inline MDP blown film line and their Heliostar S gravure presses for flexible packaging. He characterized MDO-Exceed XP formulated laminates as having very similar optics as OPP or PET/PE laminates, and noted that when an Exceed XP film is stretched, improved clarity and stiffness result.


He also touted Exceed’s XP excellent processing, noting that they have run a 25-micron MDO film with a +-1 micron deviation, which has two times the strength of a 50-micron film and at half the thickness. He confirms that about 60% of their film formulations are made of mLLDPE but for some products, they will go to 80% or 100%. The gravure printer can be used to back print as the resultant film is very stiff and strong.


Thanh Phu has produced commercial packages for both feminine hygiene and adult incontinence products and baby diapers for both Japan’s Unicharm Corp. and Kimberly-Clark, New Milford, CT. The company is considering the exploration of an all-PE package for frozen uncooke seafood to replace the current nylon/PE laminate package. 



Kurz, Engel and Lanxess Team for Decorated, Overmolded Continuous Fiber Sheet

By: Lilli Manolis Sherman 28. October 2016

A process to decorate a hybrid composite/thermoplastic part with a decorative film in one mold was among several new decorating technologies exhibited at K 2016 by The Kurz Group.


Kurz Transfer Products LP in collaboration with LANXESS Corporation Bond Laminates and Engel Machinery, Inc. have developed a process that enables a plastic composite component to also be decorated in the same processing step.



The Tepex continuous-fiber-reinforced thermoplastic semi-finished composite from Bond Laminates is formed and overmolded with plastic in a vertical press and then decorated in the same shot with a film running reel to reel through the tool cavity. Kurz also developed a new IMD coating system to suit the process: its lacquer package bonds permanently to the materials of the composite component.


• IPD-Skin process (Individualized Post Decoration) is a new process developed by Kurz in collaboration with Niebling, which makes the new IPD-Skin machine. The process involves permanently bonding a thin decorative layer to a pre-finished part. This is heated and then moved to a vacuum forming/air pressure segment where the part is fully decorated. It can be used to decorate highly three-dimensional parts and undercuts and tactile surfaced with pronounced structures can also be implemented.



• Kurz also showed new design options for automotive lighting. Included are full-surface backlighting of carbon, wood, metal or colored designs. When illumination is activated, the structures of the base designs are maintained or presented in a modified form, and completely different colors and material effects are also created.



Partially backlit designs are also possible. During daylight, you see a single- or multi-colored solid surface; when backlit, both opaque and translucent elements become visible, with various levels of transparency possible.


• Kurz also demonstrated its ability to implement dead front effects and integrate touch and gesture functions. Using Kurz's own sensor technology based on the technology of its subsidiary PolyTC, plastic parts can be equipped with a sensor function that if desired can be non-visible when inactive. In daylight, you see a solid, opaque decorative surface; on touching, approaching, or gesturing, a light source is activated and a control panel becomes visible.



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