Two-component Injection Moulding Research Articles

Cyclic Compression Testing of Three Elastomer Types-A Thermoplastic Vulcanizate Elastomer, a Liquid Silicone Rubber and Two Ethylene-Propylene-Diene Rubbers.

Thermoplastic elastomer vulcanizate (TPV) and liquid silicone rubber (LSR) are replacement candidates for ethylene-propylene-diene rubbers (EPDM), as they offer the possibility for two-component injection moulding. In this study, these material types were compared side by side in cyclic compression tests. The materials were also characterized to provide details on the formulations. Compared to the rubbers, the TPV had higher compression set (after a given cycle) and hysteresis loss, and a stronger Mullins effect. This is due to the thermoplastic matrix in the TPV. The LSR had lower compression set (after a given cycle) than the EPDM, but stronger Mullins effect and higher relative hysteresis loss. These differences between the LSR and the EPDM are likely due to differences in polymer network structure and type of filler. Methods for quantifying the Mullins effect are proposed, and correlations between a Mullins index and parameters such as compression set are discussed. The EPDMs showed a distinct trend in compression set, relative hysteresis loss and relaxed stress fraction vs. strain amplitude; these entities were almost independent of strain amplitude in the range 15–35%, while they increased in this range for the TPV and the LSR. The difference between the compression set values of the LSR and the EPDM decreased with increasing strain amplitude and increasing strain recovery time.

Technologies for the integration of miniaturised silicon sensor systems in fibre-reinforced composites

Functional integration processes gain more and more importance in lightweight engineering. In this paper we discuss how to improve fibre-reinforced composites with structurally integrated condition monitoring systems, suitable for predicting failure behaviour. Especially commercially available and tested silicon sensors, but also new developments are well-suited for this intention. We present a smart semi-finished textile with integrated silicon sensors for in-situ conditions and process monitoring in fibre-reinforced composites. It consists of a textile substrate tape with integrated electrically conductive fibres and various silicon sensors, applied by micro-injection moulding. A so-called “interposer” is used as an electrical adapter between the microstructures of the sensor system and the mesostructures of the textile. The key technology used for the encapsulation and electrical contacting of the sensor nodes is a two-stage two-component micro injection moulding process, allowing for a cost efficient and application specific mass production. As proof of concept we chose the injection moulding process to investigate the influence of the fabrication process on all electronic components with a silicon stress measurement chip. We performed in-situ measurements of temperature and in-plane mechanical stress for different glass fibre contents of the PA6 melt and tool temperatures and compared the results with a finite element simulation.

Multiphysics modelling and experimental investigations of the filling and curing phases of bi-injection moulding of thermoplastic polymer/liquid silicone rubbers

Liquid silicone rubber (LSR) is a family of high-technology elastomer materials. The member of this family has been identified as being very promising for development in the coming decades due to their unique properties and ease of generation in large series by the injection moulding process. In particular, the over-moulding of LSR on other materials, such as thermoplastic polymers, metals and ceramics, is possible today, which leads to the possibility of obtaining multi-material, functional multi-colour and newly featured components. The work presented in this paper focuses on the transformation of liquid silicone rubber to better understand the phenomena involved to improve production processes and to optimize the processing conditions for bi-material components in well-defined geometry and functional properties. The rheological, rheo-kinetic and thermal behaviours of silicone elastomers were investigated and characterized under real conditions of manufacture with different combined methods. A thermo-rheo-kinetic model was then developed and implemented using the moulding simulation software Cadmould® 3D to simulate two-component injection moulding of silicone rubber into a thermoplastic polymer. For the validation of the models chosen and the parameters identified, bi-material injection moulding tests of a two-component standard peel test specimen (polyamide thermoplastic polymer/liquid silicone rubber) were performed and compared to numerical results.

Two-component injection moulding of thermoset rubber in combination with thermoplastics by thermally separated mould cavities and rapid heat cycling

Two-component injection moulding is a manufacturing process used to combine polymers with different properties within a single product. The process is often used to combine thermoplastics of different colours or to combine thermoplastic elastomers with thermoplastics to create hard and soft areas. In this study, a two-component injection moulding process is proposed for combining thermoplastics with thermoset rubbers. This poses technological challenges since rubbers require a heated mould (160–200 ∘C) for the rubber to vulcanise whereas thermoplastics need a relatively cold mould (20–100 ∘C) for the polymer to solidify. The mould used for this study is equipped with thermally separated mould cavities and allows to reverse the injection sequence of the two materials. It was found that the optimal sequence is to inject the thermoplastic first, followed by rubber, and that the mould temperature at the interface during the vulcanisation of the rubber is a critical process parameter. Too low mould temperatures at the interface result in long vulcanisation times and poor adhesion, whereas higher temperatures at the interface both decrease the vulcanisation time and increase the adhesion strength. However, when the temperature is too high, the adhesion strength decreases again due to gas bubbles at the interface released during the vulcanisation process.

Two-Component Injection Molding of Molded Interconnect Devices

Molded Interconnect Device (MID) can be defined as that an injection-molded plastic part combining with electrical and mechanical functions in a single device. This study is to examine the application of micro injection molding technology to the two-component molding process for the MID fabrication. The process involves the first shot of a plastic component with channel patterns on the surface. A second shot by micro injection molding technology is applied to fill the channel with the plateable plastics. The effects of the micro injection molding process parameters on filled line width of the two-component MID will be investigated. It is concluded that, for a MID component, the molding conditions must be designed carefully to keep the thickness variation below the allowable value. It is also found from the experiments that the thickness interference may in the range from 92 m to 196 m to have adequate molding at the second shot.

Investigation of Material Combinations Processed via Two-Component Metal Injection Moulding (2C-MIM)

Joining materials with different properties into a single component is an attractive solution that allows producing parts with unique properties. In this respect, Two-Component Metal Injection Moulding (2C-MIM) presents numerous advantages, since the moulding and joining stage are performed in a single process step. In this work, the challenges, which occur when different materials are combined, are elucidated. Furthermore, the contact between metals with unequal chemical compositions leads to atomic interdiffusion that forms an interface layer. The interface quality is crucial to the production of intact parts after processing. Different material combinations are co-sintered and the interfaces are characterized by means of optical microscopy and EDX/SEM line scans. Further, thermodynamic and kinetic simulations are used to examine the interdiffusion in detail. The results show promising possibilities to combine different materials and helpful methods to examine the interface.

Monte-Carlo Simulation of Compatibilization by Network-Building and Catalytic Interface Reactions in Two-Component Injection Molding

Adhesion of immiscible polymers during two-component injection molding can be improved by transreactions of properly functionalized molecules in situ by exploitation of the thermal energy of the melts. These reactions must pro- vide a sufficient conversion of reactive monomers in the short cooling time down to the glass temperature. Furthermore, as much as possible interconnecting chemical links on the molecular level have to be created between the components within the small spatial region of the interdiffusion interface width. To investigate these processes, we performed Monte- Carlo (MC) simulations based on the three-dimensional coarse-grained Bond Fluctuation Model (BFM) including a ther- mal interaction potential in r 6 with energy = 0.1 kBT . We compared a simple Split type reaction, which is capable of network-forming, with a catalytic interface reactive process both exhibiting different values of activation energy. The main process of the catalytic reaction system is identical to the simple Split reaction as described in a previous paper, but now a reactive monomer creating process is prefixed. For the reacting systems different physical properties like consump- tion, radius of gyration, concentration profiles or the distribution of the degree of polymerization were calculated as a function of time. Additionally, several functions for the description of the adhesive strength on the molecular level were adopted and calculated depending on reaction type, activation energy and degree of consumption, respectively. From the results, those chemical reaction types were deduced, which should be most suitable for compatibilization intentions in two-component injection molding.

Two-component micro injection moulding for hearing aid applications

Two-component (2k) injection moulding is an important process technique at the present state of technology, and it is growing rapidly in the field of precision micro moulding. Besides combining different material properties in the same product, two-component moulding can eliminate many assembly steps in the manufacturing process chain. One of the biggest technical challenges associated with 2k moulding is the unavailability of suitable material combinations which can meet the diverse requirement from both product and process point of views. When it comes to the point of micro application, the precise dimensional requirement and tolerance make the 2k moulding a technically challenging process. This paper presents an industrial case study of 2k micro moulding covering all the important issues like product design, material selection, moulding and functionality testing of the micro moulded 2k parts. An intensive search for suitable 2k materials is made and few combinations of plastic materials are presented in the paper which can be used for highly demanding application areas like hearing aids. By using these material combinations, a demonstrator 2k micro part has been fabricated. The moulding machine was a state-of-the-art 2k micro machine from DESMA. The fabricated micro part was a socket house integrated with a sealing ring for the receiver-in-canal hearing instrument. The test performed on the demonstrator showed the potential of the 2k moulding technology to be able to solve some of the existing problems associated with hearing instruments.

The development of two-component micro powder injection moulding and sinter joining

Two-component micro powder injection moulding experienced significant progress in the recent past. Starting as a manufacturing method for integrating two different plastics, the extension of two-component injection moulding (2C-IM) from pure plastics to more resistant materials like ceramics or metals (2C-PIM) provided sophisticated and challenging applications. With the transfer of 2C-PIM to micro systems, two-component micro powder injection moulding (2C-MicroPIM) was established. Up to a certain extend sinter joining is an alternative to 2C-PIM. It allows for component assemblies to be moulded as separate low-complexity parts which are then joined into complex assemblies. This procedure considerably reduces the time and cost required to manufacture the injection moulding tools. This article gives an overview of the development of 2C-MicroPIM—from two component plastic devices to the production of complex two-component micro assemblies made of two ceramic or metallic materials and the state-of-the-art of science and technology of sinter joining.

Compatibilization in Two-Component Injection Molding by Means of Split Reactions with Varying Reactive Sites – a Monte-Carlo Simulation

Adhesion of immiscible polymers during two-component injection molding may be improved by transreactions of properly functionalized molecules in situ using the thermal energy of the melts. These reactions must provide a suffi- cient conversion of reactive monomers during the short cooling time down to the glass temperature and within the small spatial region of the interface width to create as much as possible interconnecting chemical links between the components on the molecular level. To investigate these processes, we performed Monte-Carlo (MC) simulations based on the three dimensional coarse-grained Bond Fluctuation Model (BFM) in a two-phase system. We studied split type reactions exhib- iting reactive monomers at different sites (End, Middle, Random) of the polymers governed by activation energies of EA = 0, 1, 3, 5 and 7 T k B. For the reacting systems several physical properties like consumption, radius of gyration, concentra- tion profiles or the distribution of the degree of polymerization were calculated as a function of time. Additionally, differ- ent functions for the description of adhesion on the molecular level were adopted and calculated depending on reaction type, activation energy and degree of consumption. From the results those chemical reaction types were deduced, which should be most suitable for the compatibilization in two-component injection molding.

Two-component microinjection moulding for MID fabrication

Moulded interconnect devices (MIDs) are plastic substrates with electrical infrastructure. The fabrication of MIDs is usually based on injection moulding, and different process chains may be identified from this starting point. The use of MIDs has been driven primarily by the automotive sector, but recently, the medical sector seems more and more interested. In particular, the possibility of miniaturisation of three-dimensional components with electrical infrastructure is attractive. The present paper describes possible manufacturing routes and challenges of miniaturised MIDs based on two-component injection moulding and subsequent metallisation. This technology promises cost effective and convergent manufacturing approaches for both macro- and microapplications. This paper presents the results of industrial MID production based on two-component injection moulding and discusses the important issues for MID production that can modulate the qualities of final MID. The results and discussion presented here can be a valuable user guide for mass production of moulded interconnect devices.

Experimental investigation of the factors influencing the polymer–polymer bond strength during two-component injection moulding

Two-component injection moulding is a commercially important manufacturing process and a key technology for combining different material properties in a single plastic product. It is also one of most industrially adaptive process chain for manufacturing so-called moulded interconnect devices (MIDs). Many fascinating applications of two-component or multi-component polymer parts are restricted due to the weak interfacial adhesion of the polymers. A thorough understanding of the factors that influence the bond strength of polymers is necessary for multi-component polymer processing. This paper investigates the effects of the process conditions and geometrical factors on the bond strength of two-component polymer parts and identifies the factors which can effectively control the adhesion between two polymers. The effects of environmental conditions on the bond strength are also investigated. Investigation shows that melt and mould temperatures are vital process parameters that influence the bond strength. Besides this, surface roughness of the first-shot part and environmental factors like moisture have profound influence on the bonding of the two materials. The selections of materials and environmental conditions were done based on the suitability of MID production, but the results could be useful for two-component polymer processing for a wide range of industrial applications. The results and discussion presented in this paper are only valid for the two-component plastic parts moulded by over moulding in cavity-transfer process.

An economical way to produce high-end interiors

Thermoplastic polyurethanes (TPU) open up interesting possibilities for car designers working on vehicle interiors. One particularly promising application is their combination with proven PC blends using the two-component injection moulding process. For this to function successfully, however, good bonding of the materials is essential. With a range of technically compatible material combinations from an array of possible materials, Bayer MaterialScience is now making available stable, high-impact injection-moulded parts featuring the sought-after soft-touch surface in an economical production process.

Electroforming of Metallic Microparts on Sacrificial Molds made by Two-component Injection Molding

One of the process developments required in Micro System Technology (MST) is oriented to the mass production of metallic microsystem components with high aspect ratios and high surface qualities by galvanic replication. The limiting factor is the generation of suitable templates for electroforming. A production of metallic microsystems or components in large numbers requires on one side the transcription of the special technique of the electroforming step in the LIGA process and on the other side replication and fast multiplication into a mass production process. The envisaged possibility will be given by thermoplastic injection molding of sacrificial molds and the following electroforming on these polymer molds.

MULTI-COMPONENT INJECTION MOULDING OF LIQUID SILICONE RUBBER/THERMOPLASTIC-COMBINATIONS

The two-component injection moulding method allows the production of parts consisting of two components which are arranged next to or above each other (overmoulding). Besides well known combinations between thermoplastics and thermoplastic elastomers (TPE) which are used in various applications, the combination of Liquid-Silicone-Rubbers (LSR) and thermoplastics becomes more important because of their better mechanical and thermomechanical properties as well as the chemical resistance in comparison with TPE. These combinations of LSR and Polyamid can be a new alternative for combinations made of rubber and metal, which often require a costly preparatory treatment. Concerning the adhesive strength of these combinations, which depends on the properties of the materials, the process parameters in the moulding process and the mould technique, there is only insufficient knowledge. To solve this, the IKV developed techniques to meet the requirements. Results of the investigations in this context will be presented.

Testing of Two-Component Injection Moulded Polypropylene Specimens. 1. Principles of Two-Component Injection Moulding

Testing of Two-Component Injection Moulded Polypropylene Specimens. 1. Principles of Two-Component Injection Moulding

Multimode polymeric waveguide devices fabricated by two-component injection moulding

Multimode polymeric waveguide devices with PMMA substrates, large core (0.25–2 mm2) styrene/acrylonitril copolymer waveguides and PMMA superstrates have been fabricated by injection moulding. Waveguide losses of 0.15–0.3 dB/cm have been measured in the 600–1100 nm wavelength range. The stability of the devices has been tested by temperature cycling between –40°C and +75°C.