In a research project being carried out by the IKV and KTP, the influence of geometric and process parameters on the quality of the screw connection in the direct assembly of thermosetting plastics has been analyzed. The research results show that, in addition to the geometric design, the production parameters offer additional optimization potential for the reliability of the screw connection. The compactness and curing degree of the parts exert the largest influence.

Encapsulation protects the sensitive sensor technology from external influences. The direct screw connection enables secure mounting of the module.

16:9

Higher Process Quality through Adjustment of the Production Parameters

Spritzgießen

Kunststoffverarbeitung: Verfahren

Verbindungstechnik

Schraubtechnik

Verbindungstechnik Verfahren

Duroplast-Spritzgießen

Duroplaste

Kunststoff Werkstoffe

Achieving a More Secure Connection with the Correct Design

Thermosets are being increasingly used for packaging electronic devices, and offer good properties for this application. Direct overmolding of the components is particularly interesting here. However, achieving a successful product requires striking a balance between processability, thermal conductivity and reproducibility.

In direct packaging,  the electronic devices or components are directly overmolded with the molding compound 

Thermoset Injection Molding of Packages for Electronic Devices

Elektronik

Kunststoff

Bauwesen

Baustoffe

Duroplastische Werkstoffe

Direct Packaging of Components

Last year, nearly 12.9 million t of plastics were processed in Europe using injection molding.

Elastomer-Spritzgießen

Ceresana Report on the European Market for Plastic Injection Molding

The transfer of foam injection molding from thermoplastic to thermoset processing has not yet been implemented in industrial practice. IKV Aachen has investigated this transfer and has precisely analyzed the economic efficiency of the process and the potential for lightweight construction.

Foamed thermosets can be used to produce low-density thermally resistant components at low cost

The Qualification of Suitable Foam Injection Molding Processes Enables the Use of Thermosets in Lightweight Construction Applications

Schaumspritzgießen

Excellent Resistance at Reduced Weight

Time to take stock: in what condition and with what agenda is the industry presenting itself after two-and-a-half years of a difficult climate? We have conducted a survey: insights into the dominant themes of the age.

Preview of K 2022: Kunststoffe Questionnaire on the Situation in Injection Molding Machine Construction

Steuerungen (Hardware und Software)

Automatisierungstechnik

Doriat, Clemens, Dr.

Messe K-Kunststoffmesse

kunststoffe-international.com

Steuern, Regeln

Software

Digitale Transformation

Wirtschaft

Innovationen und neue Technologie

Nachhaltigkeit

Umweltmanagement

Mess-, Steuer- und Regelgeräte

Qualitätssicherung

Qualitätssicherung Kunststoff

Energieeffizienz

Spritzgießmaschinen

Kunststoffverarbeitung: Maschinen und Komponenten

Kunststoff-Recycling

Kunststoff-Aufbereitung

Kunststoff-Rezyklat

Kreislaufwirtschaft

Harsh Realities

Paint bucket or A-pillar finisher? In our thoughts and attribution of value, packaging items and high-tech components often represent opposites. Yet the two can complement one another – when you look at used packaging as a valuable raw material. At the fair, KraussMaffei will be showing the concept for a closed material cycle and is making plastics processing sustainable through this.

First a bucket or another plastic product, then raw material for further processing: the shredded post-industrial material

At the K, KraussMaffei Will Be Showing the Cycle from Product to Upcycling  to a New Product

Smart Factory

Folientechnik (IMD, IML, FIM, u.a.)

Laserbeschriftung

Oberflächentechnik

Laserbearbeitungen

Rückverfolgbarkeit, Traceability

Qualitätsmanagement

Handling, Handhabungstechnik

Zerkleinerungsmaschinen

Greifer für die Kunststofftechnik

Compoundieren

Today Packaging,  Tomorrow Raw Material

Robotics meets additive manufacturing: when Kuka robots produce furniture, they do not take work away from carpenters by any means. The chair and bench modules made of recycled hospital waste, named Twine – designed by HagenHinderdael in London – are a novelty in the world of furniture, engineering, and recycling.

Designers Lisa Hinderdael (left) and Sofia Hagen present a better side of plastic waste. The KR Quantec used to print the larger Twine elements is in the background.

Recycled Hospital Waste as Raw Material for 3D-Printed Furniture

Industrieroboter

Montagetechnik

Filamente für additive Verfahren

Andere Werkstoffe

Werkstoffe für additive Verfahren

Additive Fertigung

Resting in Good Conscience

In the past, relying on vertical injection molding machines instead of traditional horizontal molding machines when it came to the production of 2-component molded parts was a common option for molding small and medium-sized parts but not for large size parts. But when the automotive supplier Eldisy was faced with parts in that segment horizontal injection molding machines proved to be an inaptly alternative as new vertical machine systems proved as more reliable and therefore more productive. In the Bavarian injection molding machine manufacturer LWB-Steinl, the company found a partner to enter this new territory.

A vertical gantry frame machine with two thermoplastic injection units injecting from above proves to be a “gamechanger” for the production of 2-component automotive components at Eldisy in the German Gardelegen.

Eldisy Switches to Vertical Machines for the Production of Large-Size 2-Components

Mehrkomponenten-Spritzgießen

KFZ-Zulieferer

Dienstleistungen

With a System Change  to New Competitiveness

The plastics processor TKW Molding, which specializes in safety-related automotive components, is responding to the increasing requirements of its tier 1 and OEM customers by extensively automating its injection molding production. This also encompasses downstream process steps, such as integrated component testing, traceable part deposition and packaging. The company has been working closely with Arburg in this field since 2020.

A robotic system removes the parts from TKW’s 8+8-cavity mold.

Fully Automated In-Mold Assembly Process at TKW Molding

Spritzgießwerkzeuge

Werkzeuge für die Kunststoffverarbeitung

Optische Mess- und Prüftechnik

Messtechnik

Montage-Spritzgießen

Safely Belted in

Arburg has been dealing with the issue of sustainability and resource efficiency for a very long time. The machine supplier is being integrated more and more by its customers into evaluations of climate-change activities along the supply chain.

Raw materials extraction through to delivery account for just 5 % of the CO2 emitted by an injection molding machine over its entire life cycle.  

Arburg Devises an Informative Product Carbon Footprint Calculation

Recycling

CO2 Footprint of Injection Molding Machines

Arburg has adopted a clear message for its trade fair appearance at the K 2022 in Düsseldorf: „There is only a Plan A“.

In the arburgGreenworld pavilion of the VDMA Circular Economy Forum, an Allrounder 370 A with recyclate package is manufacturing “Greenline” wall plugs from Fischer.

Spritzgießsimulation

Simulation

Industrie 4.0 für die Kunststoffverarbeitung

Industrie 4.0

Sustainability thanks to Digitalization

How the direct compounding opens up new potential to reduce CO2 footprint – also for smaller components thanks to a further development from KraussMaffei.

DCIM technology enables injection molding and compounding in a single heating process.

Efficiency Meets Sustainability: Systematically Reduce Costs and CO2 Emissions

Extruder

Extrusionsanlagen

Cost-Effective Direct Compounding for Medium-Sized Components

At K 2022, Engel, with its partners Alpla Group, Brink and IPB Printing, is presenting a quantum leap for the packaging industry. Thin-wall containers can for the first time be produced from PET directly by injection molding in only one process step.

Fig. 1. The thin-walled containers are injection molded from rPET.

kunststoffe.de

Schmelzefilter

Polyethylenterephthalat

Thermoplaste

Processing rPET by Thin-Wall  Injection Molding

GS Kunststofftechnik produces hollow bodies made of recycled polypropylene in an injection molding process for Unidome Deutschland GmbH, which replace up to 40 percent of concrete in building ceilings.

The displacers are particularly useful in multistory buildings with large ceilings, balconies and foundations with thicknesses between 18 and 50 cm. With displacers, builders can reduce concrete up to 40 %.

Less CO2 in Construction: Plastic Displacers Replace Concrete

Beton

Ecologically Sustainable Construction with Plastics

In the conception of functionally integrated and injection molding-appropriate designs, SimpaTec supports the company with up-to-date simulation expertise.

Flooded with water: the new generation of e-bike frames is manufactured by the WAIM process.

Holistic Product Development of a Carbon Fiber-Reinforced Bicycle Frame

Kohlenstofffasern / -matten

Verstärkungsstoffe

Verbundwerkstoffe / Werkstoffverbunde

Analysetools, FEM

Drop by Drop

Direct Recycling of Cured Thermosets as Fillers in the Injection Molding Process

Thermoset molding compounds crosslink irreversibly during processing. Both the material from the sprue runner system, the process start-up and scrap components are typically sent for thermal recycling as waste. The granulation and direct recycling of this material in the injection molding process increases resource efficiency due to material recycling, but has an influence on the mechanical properties of the components. In the present study, the necessary parameters are investigated.

Direct recycling of cured thermosets as fillers in the injection molding process increases resource efficiency due to material recycling.

Thermoset molding compounds have inherent disadvantages compared to thermoplastics, due to their irreversible chemical crosslinking during molding. Nevertheless, they have very good thermomechanical properties, excellent media resistance and high dimensional stability, which make them attractive for numerous applications. In addition, their price is extremely lucrative. In the “Lite2Duro” research project, the Fraunhofer Institute for Chemical Technology (ICT), together with a consortium from industry and research, is investigating strategies to increase resource efficiency in the processing of thermoset molding compounds by directly recycling finely comminuted cured components.

The basic strategy of using cured molding compounds as fillers is well known from the literature. For example, the use of phenolic resin as a filler in polypropylene (PP) has been investigated [1, 2]. Other research groups have used cured bulk molding compound (BMC) as a filler in PP [3, 4]. Both studies refer to unreinforced PP as a reference, and consequently report significant improvements in the mechanical properties.

Where thermosets are used as matrix material, the granulated fillers are mixed with the virgin material in an upstream compounding process [5 to 8]. A common factor in all the studies is that only the basic mechanical properties of the recyclate-filled plastics are investigated. This current study also examines

<ul><li>the processing properties in the injection molding process,</li><li>the influence of the recyclate filler on the geometric properties of a precision component and</li><li>the influence on the ecological footprint (LCA) of the component produced.</li></ul>

Two phenolic resin molding compounds from the manufacturer Vyncolit were used for the experimental tests:

<ul><li>Vyncolit X7530, a PF-GF55, and</li><li> Vyncolit X7320, a PF-(MD+GF)80.</li></ul>

The basic mechanical characterization was carried out on a pilot plant scale at Fraunhofer ICT using tensile test specimens. Subsequently, the dimensional stability and mechanical behavior under a realistic complex load were investigated for an oil pump adjustment ring (Fig. 1) under series production conditions, at Baumgarten automotive technics GmbH, Burbach, Germany.

Preparation and Injection Molding  of the Recyclate

To obtain the recycled material, components and sprues from the two molding compounds were crushed using a single-blade crusher and a cutting mill. Two size classes of the recyclate were investigated:

Immediately before injection molding, the recyclate was mixed in batches with the virgin phenolic resin in weight fractions between 4 and 20 %, homogenized by tumbling and fed into the material hopper of the injection molding machine.

The tensile test specimens were produced using a 6-cavity mold on a 30 mm screw diameter injection molding machine (type: Allrounder 320 C, manufacturer: Arburg). The oil pump adjustment ring was produced using KM 80/390 and KM 150/750 injection molding machines (manufacturer: KraussMaffei) in 1-cavity and 4-cavity molds (mold design and construction: Baumgarten automotive technics). In each case the transition to holding pressure was adjusted according to the injection path.

Impact Assessment Based on Global Warming Potential

The life cycle assessment (LCA) was carried out in accordance with ISO 14040 standards [9, 10] using the software GaBi [11] and the Gabi Professional database. The study determines the potential resource and greenhouse gas savings along the full life cycle of the oil pump adjustment ring, from manufacturing, to use, to disposal.

In order to demonstrate the effective contribution to recycling and circularity in terms of resource savings, a so-called “life cycle gap” analysis (LCGA) is also carried out in the evaluation phase [12]. The product system as well as the life cycle inventory of the LCA are available online [13]. The functional unit here is an adjustment ring for a controlled pendulum adjustment ring oil pump in a passenger car with an expected service life of ten years or 200,000 km. The impact assessment is based on the indicator of global warming potential (GWP) over a period of 100 years, measured in kilograms of carbon dioxide equivalents (kg CO2-eq.), according to the “Environmental Footprint 2.0” method.

The influence of the recyclate on the injection molding process is determined by investigating the maximum injection pressure as a function of the recyclate content, using the example of tensile test specimens produced from X7530 (Fig. 2). For both size classes, a clear increase in injection pressure was seen with increasing recyclate content. With the exception of the highest recyclate content of 20 wt. %, the recyclate particle size does not appear to have a significant impact on the injection pressure.

The tensile strength of the manufactured test specimens is determined according to DIN EN ISO 527–2 [14] (Fig. 3). A decrease in tensile strength of about 15 MPa is observed for recyclate contents between 4 and 12 wt. %. At higher contents of recyclate, the decrease in strength is more pronounced. Where the recyclate with a particle size of 250 µm &lt; d &lt; 1000 µm is used, a sharp decrease in strength (25 MPa) occurs even at 4 wt. %. There is no discernible influence on the measurement scatter of strength for any size class or percentage of recyclate.

The fracture surfaces of X7530 virgin material and specimens with recyclate contents of 20 wt. % in both size classes (Fig. 4) were analyzed microscopically. Individual recyclate particles are hard to identify even at higher magnification. The skin and core layer-structure typical for phenolic resin molding compounds [15] is less pronounced at d > 250 µm, and the fracture surface is generally more jagged and irregular.

Comparable results were obtained for the molding compound X7320. Due to the significantly lower strength when using larger recycled particles (250 µm &lt; d &lt; 1000 µm), the injection molding tests for the oil pump adjustment ring were only carried out with the smaller size class (d &lt; 250 µm). In injection molding, the required injection pressure also rose with increasing contents of recycled material. With unchanged injection molding parameters, mold filling with a recyclate content of 4 wt. % and above was only carried out during the injection phase of the process, and not during the holding pressure phase. This could be compensated by adjusting the holding pressure to the higher transition mass pressure.

Challenges in the Injection  Molding Process

However, one factor emerged as problematic: the increasing tendency of the nozzle to clog due to material deposits building up on the inside. This phenomenon occurred at increasingly shorter intervals of 10 to 15 cycles for the high recyclate contents > 12 wt. % and could not be significantly mitigated despite numerous adjustments to the process parameters (including back pressure, screw speed, plasticizing temperature, mold temperature and injection profile).

The breaking load of the oil pump adjustment ring, determined in accordance with the requirements of series components, shows decreasing mechanical properties with increasing recyclate content, as was the case in the tensile strength tests. There is also a tendency towards higher measurement scattering. With an average breaking load of F = 1.6 kN, the material batch with a recycled content of 4 wt. % is still slightly above the breaking load of F = 1.5 kN, defined as the acceptable/ unacceptable limit.

In contrast to the mechanical characterization, the size of the tolerance zone is not discernibly influenced by the recycled material content (Fig. 5). For all recyclate contents, a tolerance zone of s &lt; 0.03 mm is achieved, which is well within the specification of s &lt; 0.12 mm. There is a tendency for the diameter to decrease with increasing recyclate content. This is attributed to the higher cavity pressure that was required for complete mold filling in batches with a high recycled content [16].

The results of the LCA study according to the GWP 100 global warming potential show that the newly developed recycling process can effectively reduce greenhouse gas emissions by around 11 g CO2-eq. per adjustment ring (Table 1), which corresponds to around 1 % of total emissions.

From a circular economy perspective, the LCGA results (Fig. 6) show that the gap can be narrowed from the original 80 % to 77 %. The recycling of cured thermoset molding compounds from sprue distributors and from start-up and scrap components thus saves resources, and makes a positive contribution to closed-loop recycling and circularity. At the same time, it is clear from the results that there is still significant potential for improvement.

The investigations show that it is possible to recycle cured thermoset molding compounds as finely ground fillers in the injection molding process. The feasible recycled content results from a trade-off between resource savings on the one hand and the loss of mechanical properties on the other. For the inorganically filled, glass fiber-reinforced phenolic resin molding compounds investigated in this study, the limit is a recycled content of approx. 8 wt .%.

This proportion of recyclate results in a moderate loss of mechanical properties (-15 MPa tensile strength), an unchanged dimensional stability of the components and an increase in the maximum injection pressure of 100 bar. The GWP 100 global warming potential can be reduced by about 1 % and the gap in the cycle by about 3 %. In future studies, the aim will be to comminute the sprues directly at the injection molding machine, in order to achieve a closed cycle of the sprue material.

[1] Bernardeau, F., Perrin, D., Caro-Bretelle, A.-S., Benezet, J.-C. u. Lenny, P.: Development of a Recycling Solution for Waste Thermoset Material. Waste Source Study, Comminution Scheme and Filler Characterization. Journal of Material Cycles and Waste Management 57 (2018) 2, pp. 1–17

[2] Bernardeau, F., Perrin, D., Caro-Bretelle, A.-S., Benezet, J.-C. u. Lenny, P.: Valorization of waste thermoset material as a filler in thermoplastic: Mechanical properties of phenolic molding compound waste-filled PP composites. Journal of Applied Polymer Science 135 (2018) 12, pp. 1–12

[3] Bream, C. E. u. Hornsby, P. R.: Comminuted thermoset recyclate as a reinforcing filler for thermoplastics. Part I Characterisation of recyclate feedstocks. Journal of Materials Science 36 (2001) 12, pp. 2965–2975

[4] Bream, C. E. u. Hornsby, P. R.: Comminuted thermoset recyclate as a reinforcing filler for thermoplastics. Part II Structure—property effects in polypropylene compositions. Journal of Materials Science 36 (2001) 12, pp. 2977–2990

[5] Iji, M.: Recycling of epoxy resin compounds for moulding electronic components. Journal of Materials Science 33 (1998) 1, pp. 45–53

[6] Dzeskiewicz, L. A. u. Ralston, J. D.: Evaluation of regrind in thermoset applications. Proceedings of the 52nd Annual Technical Conference of the Society of Plastics Engineers, ANTEC 1994. San Francisco 1994, pp. 931–934

[7] Whalen, J. P. u. Poston, D. D.: Recycling of mineral filled thermoset epoxy. Proceedings of the 52nd Annual Technical Conference of the Society of Plastics Engineers, ANTEC 1994. San Francisco 1994, pp. 924–928

[8] Olson, B. A. u. Keyser, H. D.: Recycling cured phenolic material. Journal of Thermoplastic Composite Materials 7 (1994) 1, pp. 30–41

[9] DIN EN ISO 14044–02. Umweltmanagement – Ökobilanz. Anforderungen und Anleitungen. Beuth, Berlin 2021

[10] DIN EN ISO 14040–02. Umweltmanagement – Ökobilanz. Grundsätze und Rahmenbedingungen. Beuth, Berlin 2021

[11] thinkstep AG: GaBi. Life Cycle Engineering Suite

[12] Dieterle, M., Schäfer, P. u. Viere, T.: Life Cycle Gaps: Interpreting LCA Results with a Circular Economy Mindset. Procedia CIRP 69 (2018), pp. 764–768

[13] Kunststoffe 12/2022: HTML-Version dieses Beitrags im Online-Archiv. <a href="https://www.kunststoffe.de/onlinearchiv" target="_blank">https://www.kunststoffe.de/onlinearchiv</a>

[14] DIN EN ISO 527–2. Kunststoffe – Bestimmung der Zugeigenschaften. Prüfbedingungen für Form- und Extrusionsmassen. Beuth, Berlin 2012

[15] Englich, S.: Strukturbildung bei der Verarbeitung von glasfasergefüllten Phenolformaldehydharzformmassen, Dissertation. Technische Universität Chemnitz 2015

[16] Höer, M.: Einfluss der Material- und Verarbeitungseigenschaften von Phenolharzformmassen auf die Qualität spritzgegossener Bauteile, Dissertation. Technische Universität Chemnitz 2014

Fraunhofer Institut für Chemische Technologie ICT  

https://www.ict.fraunhofer.de

Baumgarten automotive technics GmbH  

https://www.bat-duro.com

Ausgabenartikel

Table 1. Results of the LCA study according to the GWP 100 global warming potential. 

Fig. 7. Product system for LCA of a setting ring of a controlled pendulum-slider oil pump.

Recycling of sprue loss through shredding, blending with virgin material and direct recycling.

Fig. 1. Oil pump adjustment ring made of Vyncolit X7320.

Fig. 2. Maximum injection pressure as a function of the recycled content for Vyncolit X7530. 

Fig. 3. Tensile strength as a function of recycled content for Vyncolit X7530.