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What You Need to Know About Drying Specialty Nylons

PPA is being used more frequently by molders for demanding high-heat applications in automotive and other markets. While in the nylon family, it does not dry quite like nylon. Follow these tips. William Hamm technical development engineer, Solvay Specialty Polymers Edgar Benjamin technical development engineer, Solvay Specialty Polymers Basic chemistry dictates that the strength of molded parts partly derives from the entanglement of the long polymer chains that comprise the base resin. Hygroscopic engineering resins, such as PBT, PET, PC and nylons, all absorb ambient moisture that can effectively shorten their polymeric chains and adversely affect performance in both the mold and the end part. The aliphatic amine molecule of nylons, in particular, lacks the aromatic ring directly on the molecule’s nitrogen atom, which makes them particularly susceptible to picking up moisture. If excess moisture is not removed, the presence of heat and pressure during molding can cause hydrolysis, which degrades the polymer or causes chain scissions that produce excessive outgassing, splay marks, or discoloration and compromise the physical integrity of the finished part. ▲ Specialty resins such as Amodel PPA absorb less moisture than aliphatic nylons such as nylons 6 and 66, and do so at a slower rate. Yet PPA is still considered hygroscopic and requires proper drying prior to processing. A number of specialty resins, such as polyphthalamide (PPA), have significant amounts of aromatic character in their polymeric backbone, which causes them to absorb less moisture than aliphatic nylons like nylons 6 and 66, and do so at a slower rate. The diffusion coefficient for water in some grades of Solvay’s Amodel PPA, for instance, is approximately 20% that of nylon 66 at 73°F (23°C). Put another way, PPA generally will not absorb more than 1.5% of its weight in moisture, while nylon 6 can hold up to 7%. Yet PPA resins are still considered hygroscopic and require proper drying prior to processing. It is important to emphasize that there is more at stake here than simply getting unwanted moisture out. There is such a thing as drying a resin too much. Ultimately, the aim is to ensure maximum polymer performance, which is especially important if your design calls for a specialty polymer like PPA. This also applies to less hygroscopic specialty resins like polyamide-imide (PAI) and even non-hygroscopic polymers, like polyphenylene sulfide (PPS). Although PPS is hydrolytically stable, pellets may pick up some surface moisture during shipping or storage that may result in cosmetic defects, such as surface streaks or splay marks on injection molded parts or severe bubbling or streaking in extruded profiles. Further, surface moisture can vaporize into steam within the barrel of an injection molding machine, creating internal pressures that force nozzle drool. Lastly, it is important to remember that many mineral fillers are hygroscopic and can make reinforced compounds more susceptible to moisture-driven drool even if the base resin is stoutly non-hygroscopic. ▲ Proper drying of PPA is critical to maintain mechanical and aesthetic performance in demanding applications, such as this automotive exhaust-gas recirculation valve. ROLE OF DRYING EQUIPMENT & TECHNIQUE The first step toward optimal drying of hygroscopic resins is to prevent moisture absorption in the first place. Amodel PPA, for example, is shipped with less than 0.15% moisture in vacuum- sealed, aluminum-lined containers that prevent moisture ingress. Once opened, it is critical to reseal packaging containers as quickly and as tightly as possible. Many suppliers provide tools to help molders gauge how long they should dry a resin based on how long its container has been open. Equally important is that bags should be opened individually and immediately loaded into a hopper dryer. Opening several bags to allow air conveyors to transfer the resin to the hopper as needed allows the resin to pick up moisture. When loading resin from large containers, it is best to cut just enough of the foil liner to fit an air- conveyor wand into the package, and then reseal the foil around the top of the wand. Only dried air—as opposed to “shop air”—should convey resin. More exacting applications may require measurement of resin moisture content prior to molding. Karl Fischer titration, which uses a moisture-reactant chemical, offers an efficient, rapid, and highly precise method for determining water content in resins. Gravimetric moisture analyzers, while less precise than titration, may be more suitable for a manufacturing setting. These devices comprise a sensitive weigh scale embedded within a benchtop drying oven to measure how much weight the resin loses during drying. While relatively fast and inexpensive, gravimetric analysis is not moisture-specific. So, its measurement may be distorted by the evaporation of other volatile components in the resin. The range of options for drying resin is even more diverse, but they take one of three approaches: heat, chemical desiccation, or vacuum pressure. All are suitable for drying specialty resins. • Hot-air dryers are the most effective in removing surface moisture and therefore are suitable for non-hygroscopic polymers such as polyolefins, polystyrene, and PVC. • Desiccant dryers have long been the workhorse for drying resins that absorb moisture, and generally include some configuration of a moisture-removal filter or bed that recycles dry air through the system in a closed loop. Single-bed desiccant systems are adequate as long as the desiccant is replaced as necessary, but dual-bed systems allow regeneration of one bed while the other is drying. Another variation incorporates a rotor that exposes different sections of a rotating desiccant wheel to process air, regeneration or cooling. Rotating or wheel designs absorb moisture at a more constant rate than a conventional desiccant bed, which helps to minimize spikes in dewpoint or temperature. • Low-pressure or vacuum dryers heat pellets just enough to dislodge moisture from the resin’s molecular structure, and then draw it off under vacuum. These systems can dry resins in a fraction of the time it takes other dryers, thereby saving energy and minimizing the prospect of discoloration from heat. Regardless of the technique, the key metric for effective drying is dewpoint, which equates with ambient moisture. That is, the lower the dewpoint, the less moisture there is in the air inside the dryer. The ideal dewpoint for drying most resins, including PPA, is -40°F/°C. As long as the dryer’s dewpoint remains fixed, however, time and temperature can be used to calculate when the resin is adequately dry for processing. This may vary from polymer to polymer. For PPAs, the drying time and temperature depends on the moisture content of the resin, the size of the hopper dryer used, and the throughput of the molding process. To determine the proper drying temperature, divide the capacity of the hopper dryer (in lb or kg) by the rate of resin consumption (in lb/hr or kg/hr). This will determine how long the material should remain inside the dryer, which in turn determines the drying temperature. Figure 1 shows recommended drying time and temperature for Solvay’s Amodel PPA resins when their sealed shipping container is opened. For most uses, the specified dryness is 300 ppm (0.03%) for Amodel PPA resin. However, this specification may be tighter for some applications, such as extruded monofilament, which requires the resin to be extremely dry. As previously mentioned, it is possible to overdry PPA and other resins, thereby solid- stating the material or increasing its molecular weight. This typically leads to increased viscosity or lower flow, which may result in short shots, increased pressure required to fill, and inconsistent processing. It is best to find the equilibrium temperature where uniform moisture can be maintained without over drying. The low-end tolerance for Amodel PPA is 100 ppm (0.01%) moisture content. Once a resin has been adequately dried, it is important to maintain relatively constant moisture levels throughout the molding run to ensure process and part uniformity. Melt viscosity is influenced by the amount of moisture in resin. More moisture equates with a lower melt viscosity (see Fig. 2). Moisture levels upwards of 0.15% can cause cosmetic problems such as splay or silver streaking on the surface of a molded part. Higher levels can lead to hydrolysis, and result in a significant reduction in mechanical properties. This is clearly an issue for any molder. But it underscores the importance of proper drying techniques when specifying specialty resins like PPA, which are often selected for the most demanding applications. ABOUT THE AUTHORS: William Hamm and Edgar Benjamin are both technical development engineers in Solvay’s Specialty Polymers global business unit in Alpharetta, Ga. They bring nearly 50 years of combined experience in polymer technology. Contact: 770-772-8200; William.hamm@solvay.com and edgar.benjamin@solvay.com; solvay.com; http://www.ptonline.com/articles/what-you-need-to-know-about-drying-specialty-nylons

Ms.Kang 2017-05-15

Hexion introduces new bakelite phenolic resin for coatings

Thermoset resin specialist Hexion Inc has developed a new Bakelite phenolic resin for the production of coatings with a formaldehyde (ULEF) content of less than 0.1%. Bakelite PF 7835 LB Resin offers adhesion and substrate protection when used as a crosslinking agent for polyester and acrylic based container coatings. Crosslinkers bind polymer chains together, and can produce tough and resilient coatings that can resist mechanical deformation, aggressive chemicals and sterilization processes. These coatings are used as protective liners in food cans, aerosol cans, tubes, and other metal containers. ‘Our new Bakelite ULEF phenolic resin will enable customers to formulate higher performance coatings, since they will be able to include a higher phenolic content without exceeding the preferred 0.1% limit of free formaldehyde for these applications,’ said JP Aucoin, vice president and general manager, Global Phenolic Specialty Resins. ‘The extremely low level of free formaldehyde in this resin system is significantly less than that of any other phenolic resin available in the market and provides manufacturers with a variety of formulation advantages, such as anticorrosion properties and a long shelf life.’ The new Bakelite resin features free phenol levels below 0.5%, resulting in lower overall free VOCs. Hexion also offers Bakelite ULEF resins specifically designed for use in anticorrosive and powder coatings. This story is reprinted from material from Hexion, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. http://www.materialstoday.com/composite-parts/products/hexion-introduces-new-bakelite-/

Ms. Kang 2017-05-15

Invista introduces thermoplastic resin that acts like a thermoset

By: Clare Goldsberry Invista’s Chemical Intermediates Division (Houston, TX) recently introduced a new thermoplastic material that acts more like a thermoset resin. business partnership Image courtesy Stuart Miles/freedigitalphotos.net. The new nylon-1,6 resin (formaldehyde-hexanedinitrile copolymer) has spectral features and thermal behavior aspects similar to features historically known in resins such as UF, melamine, Bakelite and others, according to Senior Research Advisor William J. Tenn. A high density of amide residues in the polymer makes it significantly more hydrophilic than other nylons; it can be used in combination with other thermoset and thermoplastic materials to modify properties such as water and hydrocarbon absorbance. Nylon 1,6 can provide a more rapid cure response than other polyamides in epoxy applications. It is being evaluated as a fortifier for use in UF-, PF- and melamine-based formulations, and as a composite material in combination with other thermosets and thermoplastic materials. Invista is currently offering partnership opportunities to accelerate development and aid in bringing the product to market. The company is interested in discussing opportunities for partnering that could take many forms including co-development, licensing and consulting. If you're interested in exploring some opportunities, send an e-mail to William Tenn , Intermediates R&D. https://www.plasticstoday.com/materials/invista-introduces-thermoplastic-resin-acts-thermoset/59773997956630

Ms. Kang 2017-05-15

Metallocene polypropylene resin eliminates weld lines in interior plastic parts

By: Stephen Moore in Automotive and Mobility ▲ Welnex/GF delivers weldless injection-molded parts. Weld line elimination and excellent surface appearance are key properties achievable with a new grade of glass fiber-reinforced thermoplastic polyolefin (TPO) based on metallocene catalyst and process technology developed by Japan Polypropylene (JPP, Tokyo). The primary target application of Welnex/GF is automotive interior components. Welnex/GF delivers weldless injection-molded parts. As opposed to conventional talc-filled polypropylene (PP) grades employed in interior applications, weld lines are almost invisible with the new grade, which crystallizes relatively slowly like a random copolymer grade, resulting in better integration of the two flow fronts. According to a JPP spokesperson, while the cycle time might consequently be roughly 10% slower, advantages such as no need for coating and a softer feel despite the 10–30% glass fiber reinforcement content have already convinced some end user to adopt the material. Further advantages of Welnex/GF include excellent mold pattern duplication, i.e., higher gloss for mirror surfaces and lower gloss for grained surfaces. And remarkably, according to JPP, glass fibers are invisible in grained surfaces. The grade is also said to exhibit outstanding color vividness (good pigment dispersion), anti-stress whitening, and less shrinkage and warp, meaning larger parts can be molded. A Welnex/GF 20% glass fiber-reinforced grade exhibits an MFR of 30, flexural modulus of 2730 MPa, Charpy impact strength at 23°C of 30 kJ/m 2, and shrinkage in the flow direction of 1.2x10 -3. JPP has also reported developmental progress in its Waymax metallocene-catalyzed high melt strength PP material. Using double-sided vacuum forming machinery commonly used to process polystyrene foam sheet, 4.2-mm thick extruded foamed sheet (10-fold expansion ratio) is now possible. JPP is also touting Waymax as a film modifier for air-cooled blown film processed using its Wintec metallocene random copolymer PP resin. Addition of 10% of Waymax grade MX3 to the core Wintec layer achieves better bubble stability, and hence higher productivity, with no sacrifice in haze, which is maintained at a level of 2.6%. https://www.plasticstoday.com/automotive-and-mobility/metallocene-polypropylene-resin-eliminates-weld-lines-interior-plastic-parts/159853120856622

Ms. Kang 2017-05-15

Thermoset resins set to feature heavily in next-generation drive trains

By: Stephen Moore in Automotive and Mobility, Compounding, Injection MoldingThermoset resins continue to play an important role in metal replacement and lightweighting in motor vehicles. And Japanese firm Sumitomo Bakelite continues to push the application envelope through the development of new phenolic resin matrix-based materials targeting the auto sector. ▲ Motorcycle engine housing molded from phenolic resin compounds saves weight and reduces engine noise. One such development turns to the ancient Japanese art of wet papermaking in a wet-laid nonwoven forming technology that interfaces and aramid or carbon fiber “entangled fiber network” with a phenolic resin molding compound. Sumitomo Bakelite envisages application in gears, where the technology has shown to be capable of reducing noise by 10 dB at a torque of 10 Nm and 1000 rpm (the counter material was an S45C steel gear). Further, gear compounds are typically 50–60% lighter than aluminum die-cast alloy gears. Sumitomo Bakelite has also developed a conductive grade for electromagnetic shielding applications. In other developments, the company has developed a long fiber-reinforced phenolic resin moldable compound that boasts shorter molding cycles compared with CFRP prepregs. Further, Sharpy impact strength is 10-times that if short fiber-reinforced phenolic resin compounds (30 kJ/m 2 versus 3 kJ/m 2) on account of the long fibers (4–6 mm versus 0.1–0.2 mm length). The compound is 34% lighter than aluminum and 77% lighter than medium carbon steel (S45C). ▲ Brake pads can be molded with integral back plates in an insert injection-molding process. Sumitomo Bakelite is also challenging the extremes of dimensional stability for thermoset molding compounds with grades Sumikon PM-5240 and 5245. Tests indicate that the standard deviation in internal diameter of parts molded from these grades is of the order of less than 0.005% while concentricity is in the range of 10–20 microns. Besides the driver train, Sumitomo Chemical believes thermoset resins have a role to play in bringing vehicles to a stop. Case in point: the company is developing an insert injection-molding process for back-injecting brake pads with a phenolic resin back plate. Sumitomo Bakelite has also joined forces with the Fraunhofer Institute for Chemical Technology ICT to joint develop composite materials for innovative functional and structural engine parts. Over the coming years, the two partners will work together to make drive trains lighter, better and more compact, and of course to integrate Sumitomo Bakelite materials into a variety of new applications. One such example is an engine housing for the BMW F650 water-cooled single cylinder (650-cc) motorcycle engine. Current die-cast from aluminum, switching to a phenolic compound would reduce the engine’s overall weight (including the mass of the cylinder) by 14–28%, while thermal efficiency would also be improved and engine noise would be reduced by 5 dB. Engine performance is equivalent to an aluminum engine housing. According to the project leader at Fraunhofer, Lars Fredrik Berg, the technology has further potential: “Besides cylinder housings and engine blocks, fiber composites such as Sumitomo Bakelite’s high-performance composite materials can be used in many other components in the drive train, to reduce weight and improve overall performance.” The materials are also opening up new possibilities in component design: “We are just starting to explore a range of new benefits and options which would not be possible with aluminum,” Berg explains. “Sumitomo Bakelite materials offer significant potential for application in and outside the drive train,” adds Pieter Vanderstraeten, CEO of Vyncolit, the European production company for the composite molding compounds of Sumitomo Bakelite in Belgium. The cooperation with Fraunhofer will accelerate the automotive industry’s adoption of these materials for innovative functional and structural engine parts. Sumitomo Bakelite Co., Ltd. is launching the sbDRIVE initiative to the automotive industry for the full development of lightweight solutions at acceptable cost in the automotive powertrain. It includes concept work, design iterations, composite material development and production techniques, prototyping, and validation testing up to industrialization for large-series production. In all of these fields, an intensive cooperation with Fraunhofer has been agreed. https://www.plasticstoday.com/automotive-and-mobility/thermoset-resins-set-feature-heavily-next-generation-drive-trains/212168276556610

Ms. Kang 2017-05-12

Using plastic to buy plastics

by Frank Esposito Teknor Apex customers now can use their plastic to buy plastics. The materials firm’s newly opened online Color Store allows any plastics processor to use a credit card to buy stock color concentrates in minimum order quantities of 2 pounds.Officials with Teknor in Pawtucket, R.I., said in a news release that the new program will simplify purchasing, particularly for processors with small product runs. The system “makes online shopping as easy for color concentrates as it is for consumer items,” they said. The Color Store enables a processor to purchase bags of 12 standard colors for polyolefins and some nylons using a credit card or PayPal. While colors are shipped in two-pound bags, customers may purchase up to 20 pounds per color at a time. There is no limit to the number of standard colors that can be purchased. All orders are shipped via UPS with freight prepaid and Safety Data Sheet (SDS) included. Overnight delivery is available.“Color suppliers typically have a standard minimum order of 50 pounds,” Teknor Color sales director Jeff Neupauer said. “Why buy 50 pounds of concentrate when 2 pounds will do? The Color Store eliminates need to carry unnecessary inventory.” The 12 concentrates are produced with FDA-compliant ingredients. Colors include Salsa Red, Citrus Orange, Sunflower Yellow, Candy Pink, Jungle Green, Forest Green, Celestial Blue, Denim Blue, Earth Brown, Wolf Gray, Raven Black and Winter White. “Ordering concentrates from the Color Store is easy,” Neupauer added. “Starting with ‘Add to Cart,’ site visitors follow the simple four-step procedure familiar to any online shopper.” Teknor is one of North America’s 30 largest compounders and concentrate makers. The firm also manufactures extruded hose products. Teknor employs more than 2,000 worldwide and has annual sales of more than $600 million. http://www.plasticsnews.com/article/20170407/BLOG07/170409929/using-plastic-to-buy-plastics

Ms. Kang 2017-05-12

6 tips for resin selection

by Scott Rishell As a custom plastics molder and contract manufacturer serving the medical, industrial, transportation, energy/environment, computer/business, and consumer markets, Mack Molding’s customers are varied, and so are their needs. To meet these diverse requirements, Mack has vertically integrated services including designing, prototyping, supply chain management, machining, sheet metal fabrication, molding, painting, assembly, testing, and fulfillment. With this diversity of services, it is interesting to note some of the most significant variation in customer requirements comes from the resin selection process. Material properties, processability, and cost all play key roles determining a resin’s suitability for an application. With thousands of grades to choose from, and new ones being developed to fill market niches, customers often turn to a contract manufacturer to help navigate the resin selection process. Here are some considerations when choosing a resin. Mechanical requirements – Parts that have specific strength requirements need to be considered when choosing a resin as different classes have various mechanical properties, including tensile strength, elastic modulus, and heat deflection. Thermoplastic resins offer a variety of strength properties that can often be modified with fillers such as glass or carbon fiber. Chemical compatibility – Many customers are concerned about how chemicals, including cleaning solvents and process reagents, interact with their resin choice. In these cases, we consult published testing data from resin manufacturers that show a material’s performance with each chemical. At times the data may not exist and testing with specific chemicals will be requested. Environmental compatibility – Parts that will be exposed to extreme hot or cold conditions need to be made with resins rated accordingly, making the long-term service temperature and heat deflection temperature critical performance metrics. Other conditions to consider include exposure to UV light and high humidity. Commodity vs. performance – When possible, customer applications are paired with commodity resin grades due to the inherent cost and availability advantages of higher volume raw material production. Some projects call for specific properties – strength, heat resistance – which is where performance resins excel. Though its higher cost makes it most appropriate for low-volume, niche applications. Amorphous vs. semi-crystalline – Amorphous resins can offer wider processing windows and improved dimensional control due to their random molecular structure. They can be transparent and are compatible with many adhesives. Semi-crystalline materials offer improved mechanical and thermal properties but can be more difficult to process. Material shrinkage – The amount a resin shrinks during the molding process can have a huge impact on the ease of building a tool or developing a successful molding process. Try to select resins that have lower shrink rates whenever possible. Once these factors are accounted for the list of suitable resins is typically cut down to a manageable number for consideration. The Mack team uses its knowledge of materials, coupled with supply chain management, to help make the final determination of a grade. Mack Moldingwww.mack.com About the author: Scott Rishell is the technical lead on several programs at Mack, developing part designs for production processes. Prior to his current role, Rishell was a program manager in Mack’s medical business, where he gained unique customer experience insights. He has a bachelor of science in mechanical engineering from the Rochester Institute of Technology. Rishell can be reached at scott.rishell@mack.com. http://www.todaysmedicaldevelopments.com/article/6-tips-for-resin-selection/

Ms. Kang 2017-05-12

Lightweight PP and plastic-metal hybrid solutions on show at Germany’s VDI congress

By: Stephen MooreWith the automotive industry’s continued focus on reducing emissions and increasing fuel efficiency, materials-maker SABIC is presenting a range of solutions at this year’s VDI Plastics in Automotive Engineering Congress in Mannheim, Germany. The solutions cross a range of application segments – from a vehicle’s exterior and glazing to components like instrument panel carriers and structural reinforcements for the body-in-white (BIW). Combined, these solutions can potentially reduce the overall weight of a vehicle by 13 to 15 kg. “Our featured solutions at this year’s VDI Congress bring forward some novel approaches or highlight progress in other technologies,” said Scott Fallon, global leader of SABIC’s automotive business. “I especially like that we’re showcasing answers for the industry that can ease multiple pain points. They not only help OEMs shed weight. They add value in other ways, too.” ▲ Injection-molded foamed instrument panel carrier uses LGFPP in combination with a block copolymer PP grade to achieve lightness and stiffness. A good example of this is plastic-metal hybrid (PMH) structural reinforcements for the vehicle’s BIW. A PMH floor rocker reinforcement, for instance, can help reduce weight by up to 45 percent vs. an all-steel alternative. In this component, NORYL GTX resin (mPPE/PA) from SABIC combines with steel to form a very efficient energy-absorption crash box structure. This saves 1 kg in weight and maintains the required level of crashworthiness. The component is an industry-first use of plastic in a BIW reinforcement without the use of structural adhesives or foams. Use of the NORYL GTX resin allows the part to go through the automaker’s e-coat process with the rest of the BIW. Additional opportunities across the BIW means that a manufacturer could save up to 8 kg of weight with these hybrid solutions vs. all-metal reinforcements. SABIC is also featuring an injection-molded, foamed instrument panel carrier. The part uses the company’s STAMAX long glass fiber polypropylene (LGFPP) resin (60YK270E grade) with a block copolymer SABIC PP resin (612MK10EE grade) in a structural foaming process. In this approach, the manufacturer injects the material into the mold with a foaming agent. Immediately afterwards, the mold is opened a few millimeters, controlling the final density of the part. During the process, the foaming agent produces CO 2 bubbles that create a foamed core. The final produced part is both light and stiff. SABIC’s solution is emission-optimized and meets the VDA278 industry standard. Other potential benefits from this foamed STAMAX resin solution include the need for less material during processing, shorter cycle times, and a better balance of impact and stiffness. Another PP-based solution from SABIC on display is a lightweight, thin-wall front bumper on a recently launched 2017 model. This part uses SABIC PP compound (8650 grade) to optimize the thickness to 2.5 mm, which can save more than 10 percent in weight. Low shrinkage, excellent impact-stiffness balance and potentially reduced cycle times are among the advantages of this approach. SABIC’s material is an open compound, which allows for greater dimensional flexibility for molders. SABIC continues to highlight progress in plastic glazing applications. This time, the featured part is an in-production rear quarter window, the largest in the world in LEXAN polycarbonate (PC) resin (GLX143 grade). A two-shot injection compression molding process combining PC resin with CYCOLOY PC/ABS alloy (XCM830 grade) results in a final part that is up to 40 percent lighter vs. conventional glass. This glazing solution allows for design features not possible in glass, as well. Notably, this window is the first from a new production facility in China devoted to the manufacture of mass-produced LEXAN PC glazing parts. Finally, SABIC is highlighting ongoing development work in the use of unidirectional laminates. The idea is to combine the material supplier’s UDMAX tape with STAMAX LGFPP resin to achieve further weight reduction, while improving mechanical performance. UDMAX tapes are fiber-reinforced thermoplastics, which offer high strength and stiffness, good processability and fatigue resistance. https://www.plasticstoday.com/automotive-and-mobility/lightweight-pp-and-plastic-metal-hybrid-solutions-on-show-germany-s-vdi-congress/160457500956549

Ms. Kang 2017-04-07