SPECIAL: PU Elastomers (cast, spray, TPUs)

Transcription

1 September 2017 English EUROPEAN POLYURETHANE JOURNAL SPECIAL: PU Elastomers (cast, spray, TPUs) in German in Russian KP VERLAG ISSN FACHMAGAZIN FÜR DIE POLYURETHANINDUSTRIE

2 Technical Articles New markets for PU pultrusion Wolfgang Hinz, KraussMaffei Technologies GmbH, Munich, Germany Benedikt Kilian, Covestro Deutschland AG, Leverkusen, Germany Pultrusion is on the verge of a performance boost: Together with Covestro and other partners, KraussMaffei has managed to increase the pultrusion speeds to up to three meters per minute with the new ipul machines. Covestro offers polyurethane (PU) materials for the new machine technology which permit industrial-scale production. Together with their customers, both companies want to open up applications and markets which were previously closed off to pultrusion. Pultrusion is one of the few industrial technologies for the continuous production of high-filled, continuous fiber-reinforced composite profiles. According to estimates published by the market research company Lucintel, the global market for pultrudates is currently growing at annual rates of approx. 5.1 %. In 2016 it had a volume of 1.54 billion US dollars. The main customers were the consumer goods, construction, and chemical industries (Fig. 1). Linear and curved profiles Fig. 2: The new ipul machines combine the direct injection of the matrix material with the radius pultrusion process. The results are higher production speeds. (Source: KraussMaffei) KraussMaffei brought in its know-how as a market leader in dosing technology for fiber composites and its expertise in extrusion to the development of ipul (Fig. 2). For the first time pultrusion operators can acquire turnkey complete solutions, in which the machine, process, and tool technology comes from a single source and important process parameters such as the discharge capacity or haul-off speed can be controlled centrally. Up to now processors had to put together their machines from individual components from different providers, which led to tuning problems between the individual components and disadvantages in terms of production efficiency and comfort. Fig. 1: Examples of pultruded profiles with PU matrix (Source: Covestro) The process is based on continuous fiber rovings which are generally made from glass, carbon, basalt, or aramid. They are continuously removed from fiber shelves and soaked and impregnated in an injection box with the liquid matrix of a thermoset resin system. The fiber composite is hardened in a mold when heat is added. Grippers behind the mold pull the hardened profile continuously, which is why the process is also called pulling profiles. After cooling a floating saw cuts the profiles into defined lengths. The result is straight profiles with a generally constant cross-section, which are characterized by very high strength and stiffness in the fiber direction with low weight. The i in ipul stands for injected, innovative, integrated, and industrialized. In the new ipul machines the fibers are no longer soaked in an open trough, but by a dosing machine in a closed injection box. The direct continuous injection of the matrix material has several advantages over the previous common soaking in a trough and pulling process. The machines are more compact and protect the operators of the pultruder against unpleasant smells and potentially hazardous emissions. Above all, however, the pultrusion speeds can be increased significantly by a special temperature control during curing and by design measures from previously 0.5 to 1.5 meters per minute. This leap in efficiency makes possible applications which were previously closed off to pultrusion due to costs. Machines with which two- and three-dimensional curved profiles can be manufactured by radius pultrusion are also offered. KraussMaffei is working closely with Thomas GmbH + Co. Technik + Innovation KG (Thomas Technik), Bremervörde, the inventor of radius pultrusion. 32 FAPU EPJ September 2017

3 Resin with higher reactivity can be used A further benefit of the new machine technology is its flexibility and precision. With the injection box and dosing technology with a newly developed mixing head, it is not only possible to process very different resins. In fact, systems with higher reactivity such as PU can also be pultruded without any problems. The formulations can be adjusted precisely to the component requirements. The injection of the matrix material is effected under low pressure, which saves costs. The internal pressures in the injection box are between 5 and 100 bar. Injection points are product-specific and can be individually adjusted. Additives such as flame retardants, release agents, color pigments, or filler materials can be added directly. The use of woven and non-woven fiber fabrics is also possible. The defined profile is pulled via a synchronized puller with spindle drive or in the case of profiles with simple geometry by caterpillar or belt haul-off. After the injection box the profile passes through an extrusion tool with three or more individually adjustable heating zones. ipul is also suitable for the pultrusion of thermoplastic materials. The machine technology is currently being modified so that in the future Polyamide 6, for example, can also be pultruded. Thermoplastic matrices are required if the component should be weldable. Network of expertise in pultrusion PU resins have already been used in pultrusion for quite some time now. With their performance profile they are an alternative to resin systems which are established in pultrusion. They are also ideal in many applications for the substitution of other materials such as thermoplastics and wood or metals such as steel or aluminum. Despite the benefits they offer, their application potential has not yet been fully exploited. These opportunities can only be used on an industrial scale if, in addition to customized materials, there is also high-performance machine and process technology tailored to PU resins with which competitive component solutions can be realized. This was the reason why Covestro and KraussMaffei decided to cooperate roughly two years ago. The leading international manufacturer of injection molding, reaction and automation technology works closely with providers of resin systems in a network of expertise in pultrusion. Its aim is to improve the efficiency of the process through joint material and process developments and thus come up with new applications. The Competence Day Pultrusion ( Fig. 3: Wind power as a future market: Pultruded Spar Caps for reinforcing rotor blades (Source: Covestro) com/rpm-en/pultrusion.html) organized at the end of June this year at KraussMaffei in Munich provided an up-to-date intermediate status of the previous results. (Fig. 7 and 8) The new ipul machine was unveiled to the public for the first time at the event. In addition, a good-quality square hollow profile was manufactured using a PU system from Covestro at a production speed of two meters per minute. Besides the ipul, tailormade material solutions for the construction, wind power, automotive, and aerospace industries were also presented (Fig. 3 - Wind turbines). Furthermore, the possibilities of radius pultrusion were explored. Comparison of PU resins Compared to established materials for pultrusion, such as epoxy, unsaturated polyester, or vinyl ester resins, PU resins have significant advantages. Their low viscosity, the good wetting characteristics of the fibers, as well as the high reactivity, permit higher processing speeds compared to epoxy resins, which in turn lowers production costs. It also results in components with improved surface quality. The mechanical property patterns of PU pultruded materials, such as the strength and stiffness, are comparable to those of epoxy resins. They are significantly higher compared to polyester resin systems. PU components are more stress-resistant than their polyester resin counterparts. Alternatively, at a given load the wall thickness can be reduced and components can be more easily designed and by doing this the material consumption as well as the component costs are lowered. Another benefit of the higher mechanical performance of PU resin is that it can make a fiber reinforcement transverse to the profile direction superfluous for example by using fabrics or mats. This leads to a simpler process and lower production costs. In general, the processing properties of PU systems such as the reaction time and viscosity vary greatly. They can be precisely adapted to the respective manufacturing process and the component requirements. The viscosity can be controlled so that intricate or complex component geometries can be accurately shown without any errors. Two PU resin product series Covestro offers the PU systems Baydur PUL and Desmocomp for pultrusion. They are available worldwide in a uniform high quality. The differences between the two product groups are their property patterns and their application. In close cooperation with its customers, Covestro takes care of the applicationspecific fine tuning of these pultrusion materials. Baydur PUL are liquid, two-component PU systems. The derived pultrudates have excellent stiffness, elongation at fracture, shear strength, and impact strength. Other strengths include the high flame resistance, the excellent thermal insulation, the corrosion resistance, the low creep tendency, and the low linear expansion. These property patterns were the deciding factors in manufacturing profiles for doors and windows from Baydur PUL (Fig. 4 ). Aluminum profiles are substituted at comparable production costs. The PU profiles are mechanically more stable also than PVC profiles, have higher sound insulating properties, are more airtight, and above all have higher heat insulation. Window profiles are an attractive area of application of PU pultrusion resins, which according to estimates by KraussMaffei will grow rapidly at annual rates of around ten percent. So far the production speeds for window profiles with traditional pultrusion machines were roughly 0.4 meters per FAPU EPJ September

4 Fig. 4: The PU frame components play an important role in making the windows and doors airtight, as well as very heat-insulating, thus saving heat energy. (Source: Internorm International GmbH) minute. With the ipul technology the speeds could be significantly increased. Fig. 5: Pultruded profiles with Desmocomp (Source: Covestro) Fig. 6: The side parts of the prototype of a weatherproof transport container for pick-ups and flatbed vehicles can be manufactured not only lighter, but also more cost-effectively with Desmocomp than with sheet steel. (Source: Sortimo) UV resistant and weatherproof Desmocomp is a PU system which is based on aliphatic PU raw materials. Derived pultrudates are characterized by excellent inherent UV resistance and weathering strength and are therefore also suitable for external use (Fig 5). Furthermore, the composites can be colored, are flame-retardant and resistant against chemicals. They have anti-graffiti property patterns and excellent mechanical property patterns (Fig. 6). For example, the transversal bending strength and interlaminar shear strength are higher than for pultrudates based on epoxy, unsaturated polyester, and vinyl ester resins. The single-component PU system is easy to process with a long pot life and cures quickly. Desmocomp received the JEC Innovation Award in the Raw Materials category at the international composites exhibition JEC World in Paris in Know-how! Customer service from A to Z KraussMaffei and Covestro boast many years of experience in composite technology. Both companies are very familiar with the structures, trends, and key players in the industry. This experience and expertise will also benefit the operators of pultruder machines in the future. In addition, development partners benefit from the know-how that Covestro, as one of the world s leading providers of PU coating raw materials, has in the painting of plastic parts. The polymer manufacturer has vast experience in fiber coating and offers, for example, film formers for glass and carbon fiber layers with the watery PU dispersions Baybond. Both companies support their customers from the pultrusion industry all over the world with a comprehensive technical and commercial service. Covestro develops customized materials for its customers. KraussMaffei offers partners system technology optimized to their specific needs. Both companies are providers of integrated complete solutions. The services for customers range from the concept phase, component analysis, and material selection, to the design, mold and machine dimensioning, through to the series start and production. Fig. 7: Constant transfer of know-how: Over 200 visitors obtained information at the KraussMaffei Competence Day Pultrusion about the new ipul machine. (Source: KraussMaffei) 34 FAPU EPJ September 2017

5 The services offered by Covestro include, for example: Support with the conversion of a pultrusion system to PU systems Support with the design of the injection box and mold dimensioning Simulation of the pultrusion process, e.g. regarding the heat transport and cross-linking Simulation of typical loads which the pultrusion component must endure Provision of material properties which were determined in the certified test lab of Covestro Troubleshooting upon start-up of production KraussMaffei supports its customers, for example: With studies to assess the feasibility of a component and with the simulation of the fiber infiltration With the process-oriented design, development, and production of components With material experiments and prototyping in the in-house pultrusion lab With the optimization of the interfaces between the individual system components With support in the automation of assembly and storage of the profiles Outlook Development projects for pultrusion Covestro and KraussMaffei use their broad knowledge of fiber-reinforced composites on thermoplastic and thermoset basis in order to extend the range of applications and services of pultrusion through process- and material-related innovations. The fundamental goal is to further industrialize the technologies. Both companies therefore cooperate not only with well-known industry partners, but also with research institutes and universities. Covestro is working, for example, on the strengthening of the PU system with other continuous fibers made from carbon. In the future the process should also be qualified for the use of metal, natural, or aramid fibers. Other research topics include the coloring of PU pultrudates, as well as the further development of aliphatic, lightfast PU resin systems. Another focus is on PU systems which produce components with even better mechanical property patterns, and on new catalysts and PU systems which make possible higher production speeds and a simpler process. The focus areas of the development work of KraussMaffei include the further automation of the process, the optimization of process and quality monitoring, and higher pultrusion speeds with a stable process. In addition, the machine manufacturer concentrates on the pultrusion of profiles with very prominent geometric complexity (e.g. with several hollow chambers and varying wall thickness) and on increased productivity through multi-cavities. Authors: Wolfgang Hinz is a product and sales manager in the Composites/Surfaces Business Unit in the Reaction Process Machinery Segment of KraussMaffei Technologies GmbH, Munich. The qualified economist (FH) has been at KraussMaffei since 2002, and has been working in the Composites/Surfaces BU since Benedikt Kilian studied industrial engineering specializing in mechanical engineering at RWTH Aachen and since 2015 has been employed at Covestro Deutschland AG as a project manager in the business area Processing and Application Technology in the Polyurethanes Business Unit. Fig. 8: Struck a chord with the market with the new ipul machine: Daniel Lachhammer, Nicolas Beyl, Josef Renkl, and Wolfgang Hinz from Krauss- Maffei (f.l.t.r.) (Source: KraussMaffei) FAPU EPJ September