| Summary: |
The Reaction Injection Moulding (RIM) is an industrial process for plastic parts production, mainly polyurethanes, where two or more reacting monomers are rapidly mixed in a small cylindrical chamber, the mixing chamber, characterized by extremely short liquid passage times, in the range of 10-100 ms. The resulting reacting mixture is then discharged into a mould, where most polymerization takes place. The monomers are introduced into the mixing chamber by two opposing jets, with injection velocities usually ranging from 10 to 100 m/s. Due to the high viscosity of the injected monomers, up to 1 Pa s, and in spite of the extreme dynamics expected for the jets' impingement when they are decelerated over the short space of one diameter of the mixing chamber, 5-10 mm, the flow field is still basically laminar.
Existing RIM machines do not include real time controlling procedures for assessment of mixing within the mixing chamber, which is a critical step of the RIM process. Recently new concepts for RIM control, registered as RIMcop®, were introduced at LSRE/FEUP and are presently being patented (Lopes et al., 2004, 2005).
This project aims to study the mixing mechanisms in the mixing head of a RIM machine and to identify the parameters and conditions that will enable the precise control of a RIM machine. Two main concepts of the RIMcop® technology - controlled induction of oscillations and flow rate pulsation - will be further developed and tested in the existing laboratory pilot RIM machine using experimental techniques such as LDA and PIV. Another RIMcop® novel concept, the introduction of a third jet injector, whose potential has been shown by CFD, will be experimentally validated with a new pilot mixing head chamber equipped with a centralized needle type injector using experimental techniques such as LIF.
A new industrial scale RIMcop® Prototype machine that will incorporate the above new mixing control
technologies and the third jet i  |
Summary
The Reaction Injection Moulding (RIM) is an industrial process for plastic parts production, mainly polyurethanes, where two or more reacting monomers are rapidly mixed in a small cylindrical chamber, the mixing chamber, characterized by extremely short liquid passage times, in the range of 10-100 ms. The resulting reacting mixture is then discharged into a mould, where most polymerization takes place. The monomers are introduced into the mixing chamber by two opposing jets, with injection velocities usually ranging from 10 to 100 m/s. Due to the high viscosity of the injected monomers, up to 1 Pa s, and in spite of the extreme dynamics expected for the jets' impingement when they are decelerated over the short space of one diameter of the mixing chamber, 5-10 mm, the flow field is still basically laminar.
Existing RIM machines do not include real time controlling procedures for assessment of mixing within the mixing chamber, which is a critical step of the RIM process. Recently new concepts for RIM control, registered as RIMcop®, were introduced at LSRE/FEUP and are presently being patented (Lopes et al., 2004, 2005).
This project aims to study the mixing mechanisms in the mixing head of a RIM machine and to identify the parameters and conditions that will enable the precise control of a RIM machine. Two main concepts of the RIMcop® technology - controlled induction of oscillations and flow rate pulsation - will be further developed and tested in the existing laboratory pilot RIM machine using experimental techniques such as LDA and PIV. Another RIMcop® novel concept, the introduction of a third jet injector, whose potential has been shown by CFD, will be experimentally validated with a new pilot mixing head chamber equipped with a centralized needle type injector using experimental techniques such as LIF.
A new industrial scale RIMcop® Prototype machine that will incorporate the above new mixing control
technologies and the third jet injector will be constructed at ESTG/IPLeiria in order to validate the operational feasibility of these techniques and to establish the relationship between the composition of the mixture (that depends on the mixing process) and the polymerisation and flow process inside the mould. The final validation of this technology will be achieved by producing polyurethane RIM parts, which will be characterized by using DSC and DMA techniques during mould filling and curing in addition to the end product analysis.
This project brings together two research groups that have done work on RIM from two different perspectives. The group at LSRE/FEUP has focused on the mixing head phenomena, studying the mixing mechanisms by experimental data acquisition on a pilot RIM machine and by CFD simulation. The group at ESTG/IPLeiria has a vast experience on construction and operation industrial scale RIM machines, focusing on the phenomena occurring in the mould, namely the curing process.
A FEUP spin-off company, Fluidinova, Engenharia de Fluidos, SA, has recently been constituted with the objective of developing and introducing to industry technologies developed at LSRE/FEUP, such as the RIMcop® technology. The role of Fluidinova is key to this project, namely in the search for potential industrial applications and new formulations for this technology. |