反应注射成型及其制品性能和应用

介绍反应注射成型特点与原理,以及反应注射成型制品的性能与应用。     

Moldability diagrams for the reaction injection molding of a polyurethane crosslinking system

A trial and error approach reflects the state of the art in reaction injection molding. Material and process parameters determine the “moldability” of a specific system in a particular application. The concept of “molding areas” on the critical parameters plane can be extended form thermoplastic injection molding (TIM) to reaction injection molding (RIM). In this work moldability diagrams for the filling and curing stages of a RIM process are obtained based on a simplified engineering approach. The key process parameters chosen for the filling stage are initial material temperature and filling time. In the curing stage, the critical parameters are considered to be mold wall temperature and demold time. Experimental results obtained on a laboratory-scale RIM machine on a Crosslinking polyurethane system are used to check the validity of the predicted molding areas. The agreement obtained is satisfactory considering the broad range of processing parameters used.     

High strength continuous glass strand—polyurethane composites by the reaction injection molding process

Considerable work has been published on the subject of filling reaction injection molded (RIM) polyurethane elastomers with discontinuous particulate fillers such as milled glass fibers, flake glass and wollastonite, RIM polyurethane elastomers are filled for three reasons: (1) to increase stiffness, (2) to decrease the linear coefficient of thermal expansion, and (3) to improve thermal dimensional stability. Discontinuous particulate fillers either do not appreciably change strength properties, e.g., tensile strength or they cause dramatic reduction in strength properties, e.g., impact resistance. To overcome these deficiencies, new fillers are necessary. Once such material is continuous glass strand mat. In order to make continuous glass strand-polyurethane composites by the RIM process, a particular balance of ingredients to produce the RIM polyurethane must be used. We will discuss the properties of these composites and suggest possible applications and future directions in which this research might proceed.     

反应注射成型尼龙6的研究进展

介绍了反应注射成型尼龙6（nylon 6-RIM）、增强反应注射成型尼龙6（nylon 6-RRIM）、毡片模塑反应注射成型尼龙6（nylon 6-MMRIM）以及反应注射成型尼龙6嵌段共聚物（NBC-RIM）材料的性能特点以及研究进展。并讨论了nylon 6-RIM材料在各个领域的应用优势和前景。     

Reaction injection molding (RIM) elastomers having superior high temperature performance

Reaction injection molding (RIM) elastomers are being seriously considered by major automotive companies as a substitute for metal in exterior body panels. One major consideration in this application is dimensional stability at a 325°F paint bake cycle. Reported here are formulations which via novel processing result in finished parts with excellent dimensional stability at 325°F. In addition, other properties such as impact resistance and flex modulus ratio improve parallel with high temperature performance. Mechanical properties as a function of processing and molding parameters are presented. Other studies are presented and a tentative explanation of the superior performance of these RIM elastomers is made.     

Three-dimensional modeling of reaction injection molding. I

In this research a model to simulate both the filling the curing stages of a reaction injection molding (RIM) process in complex three-dimensional molds is developed. This model can be used to predict not only the temperature and conversion changes with time but also the front position during filling. Using given physical and chemical properties of the RIM system, moldability can be determined in advance. The numerical techniques used in this research include adaptation of the SIMPLE algorithm developed by Patankar for a moving-front, two-phase system with non-negligible inertial effects, and exothermic chemical reaction. The model predictions of temperature and conversion compare favorably with available data on simple two-dimensional molds. The ability of the model to predict the dynamics of filling in more complicated molds was verified by comparison to mold filling experiments with water and a polyurethane foam.     

RIM聚氨酯加工设备及其在汽车内饰件生产中的应用

介绍了反应注射成型(R IM)聚氨酯(PU)加工设备中原料储存系统、原料预混系统、R IM高压发泡机、模塑发泡生产线等几个主要组成部分及其工作原理,并从经济效益、环保、节能、自动化程度等方面介绍了此类设备的最新研发技术及其在汽车内饰件生产中的应用。     

反应注射成型聚双环戊二烯研究进展

聚双环戊二烯是采用反应注射成型工艺合成的一种性能优良的新型工程材料,是通过开环易位机理形成的聚合物。综述聚双环戊二烯聚合机理,反应注射成型技术概况。主要对在运用此技术合成不同类型聚双环戊二烯中采用的不同催化剂体系的作用进行了阐述。     

Adiabatic reactive viscometry for polyurethane reaction injection molding

Adiabatic reactive rheometry involves the simultaneous measurement of viscosity and temperature changes during adiabatic polymerization. Using the adiabatic reactor method to relate temperature to fractional conversion results in a useful rheokinetic tool ideally suited for fastreacting reaction injection molding (RIM) systems for which the mold-filling step is nearly adiabatic. In this work, a small laboratory RIM machine is used to mix the reactants and deliver them to a constant stress rheometer retrofitted with a wide-gap Couette geometry and two thermocouples. Measurements on two polyurethane systems are reported. A simple cross-linking system is used to verify the adiabatic rheokinetic method through comparison to a known gel conversion. Subsequent measurements on a phase-separating RIM system show that increases in catalyst level, hard segment content, and initial reactant temperature result in a decreased gel time and an increased gel conversion. The viscosity rise profiles aid our understanding of the onset and development of phase separation. They are also essential for mold-filling models and establishing moldability criteria for these RIM systems.     

Kinetics and conversion monitoring in a RIM themoplastic polyurethane system

Kinetic data are reported for the fast polymerization of a thermoplastic polyurethane under conditions similar to that of commercial reaction injection molding (RIM). The components were a 2000 molecular weight polyester polyol, butanediol and 4,4′-diphenylmethane diisocyanate. Three catalysts–dibutyltin dilaurate, phenyl mercuric propionate, and triethylenediamine–as well as uncatalyzed formulations were studied. Kinetic parameters were obtained by numerically fitting adiabatic temperature rise data with both second-order and hyperbolic models. The hyperbolic model gave consistently better fits and is supported by mechanistic studies in the literature. Activation energies compare well to literature values. The uncatalyzed rate was found to be significant. The kinetic parameters obtained by this method are useful measures of catalyst performance in the RIM systems. Moreover, the models provide a conveient way to predict the extent of reaction during the production of parts by the RIM process. The shape of the reaction pathway (extent of reaction time) may be important in the development of physical properties of polymers produced by the RIM process. Physical properties for these samples compare favorably to those for a conventionally produced (batch) polyurethane of the same formulation.     

Reaction injection molding of polyureas. II: Rheo-kinetic changes and model simulation

An experimental and theoretical study of reaction injection molding (RIM) of polyurea was conducted in this work. A lab-scale RIM machine was used to carry out the polyurea bulk polymerizations. A “free-table” viscometer was designed to measure the fast rheological changes and liquid-solid transition. A mathematical model was proposed to simulate the fast reaction and rheological changes in the polyurea RIM process. The parameters of this model were determined based on the solution polymerization data from FTIR and Haake rheometer measurements. Combined with an appropriate heat transfer equation, this model predicts fairly well the adiabatic temperature and viscosity rises of bulk polyurea reactions in RIM.     

Chemical recycling of reinforced polyurethane from the automotive industry

R-RIM PU (reinforced-reaction injection molding polyurethanes) from the automotive industry (production scrap and parts at the end of their life cycle) can be recycled for the production of new RIM PU by a chemical process. Among the various possible chemical processes (hydrolysis, alcoholysis, aminolysis, and pyrolysis), we have examined glycolysis, a particular form of alcoholysis, for the purpose of obtaining a mixture of oligomers sufficiently similar to a polyol to be used in the production of new R-RIM PU. Glycolysis with dipropylene glycol (DPG) of R-RIM PU forms a monophasic product that could be used in the preparation of new, highly crosslinked polymers, similar to those used in the preparation of rigid thermal insulation foams. The same product, because of its high hydroxyl number, cannot be directly re-used in the production of new RIM PU. Partial substitution of free DPG in the glycolysis product with a triol having high molecular weight forms a homogeneous mixture suitable for production of new RIM PU. This final product has been used in the original R-RIM application introducing an appropriate optimization of formulation. In comparison with RIM PU obtained from only virgin materials, the loss in properties of molded parts based on even high amounts of regenerated polyol was only marginal.     

环氧树脂的RIM成型技术现状及发展

本文着重综述以环氧树脂为中心的RIM(反应注射成型)以及RRIM(增强反应注射成型)的现状及研究动向.     

Reaction kinetics of a polyurea reaction injection molding system

Polyureas have the potential for Improving reaction Injection molding (RIM) productivity through shorter demo Id times and elimination of external mold release agents and post-cure. Kinetics of urea formation are necessary for process modeling of polyurea RIM systems. Adiabatic temperature rise measurements were used to monitor the extent of reaction of an aliphatic diamine and an aromatic diamine reacting competitively with a single diisocyanate. The aliphatic diamine reacted much faster; essentially complete polymerization occurred in the RIM mixhead. A similar three-component system was studied in dimethylacetamide and diethylene glycol dimethyl ether, and the sequential nature of the two competing reactions was confirmed. The RIM polymerization of the aromatic diamine, 3,5 diethyltoluene (2,4 and 2,6) diamine and;4,4′-diphenylmethane diisocyanate was studied using an unreactive poly ether as the solvent. The exotherms could be fit with a third order model. Adiabatic temperature rises for all RIM experiments were in good agreement with the values predicted by heats of reaction measured in solution.     

Applications of a reaction-injection-molding process model in the analysis of premature gelling,demold time,and maximum temperature rise

In this paper, we discuss a way to present results or practical interest for the reaction injection molding (RIM) process, such as guidelines to avoid premature gelling and to control demold time and maximum temperature rise. The results are presented as a set of graphs correlated using the relevant dimensionless groups of the process. Examples of applications of these graphs are given and discussed. The numerical calculations are done using the RIM process model developled by Castro and Macosko, which has been shown to agree with experimental results.     

Processing of polyurethane/polyester interpenetrating polymer networks by reaction injection molding (RIM). Part I: Design of a high pressure RIM system

This is the first of a three-part paper investigating the feasibility of processing polyurethane/polyester Interpenetrating Polymer Networks (IPN) by Reaction Injection Molding (RIM). The fundamental mixing process is discussed. Various approaches reported to analyze mixing are also critically reviewed. Good part quality in RIM mixing activated systems suggests the need for the creation of a rapid and intense turbulent state within the small impingement chamber. In order to generate the conditions of reactive components intermingling down to submicron dimensions, a high pressure RIM unit was built and tested. The device can inject reactants at high stream Reynolds numbers (around 10,000) and impingement pressures (up to 100,000 psi, 6,895 bar.).     

Conversion studies in a novel reaction injection molding process for syndiotactic polystyrene

Syndiotactic polystyrene (sPS) has successfully been produced using a novel reaction injection molding (RIM) process and a metallocene catalyst. Previous studies have shown that many of the requirements for a RIM process are achievable. However, problems due to incomplete conversion of monomer have hindered the commercial development of this process. In attempts to overcome this conversion limitation and gain insight into its nature, the effects of the extent of mixing, reaction time, and mold wall temperature were investigated on the monomer conversion and polymer properties. The properties of interest included the sPS fraction, molecular weight, melting point, and stereoregularity of the polymer produced. It was found that this RIM process was not mixing limited. Longer reaction times resulted in an increase in conversion, with no significant change in the polymer properties. Mold wall temperature had the greatest effect on both the conversion and polymer properties. Lower mold wall temperatures resulted in an increase in the conversion. At both of the temperature extremes studied, the polymer properties deteriorated. Infrared spectroscopic analyses of the as-polymerized samples indicated that sPS helical conformations were present. This suggested that the styrene monomer may be entrapped within the helical crystalline structures of sPS, preventing complete monomer conversion during this sPS RIM process. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2679–2693, 1998     

反应注塑成型聚双环戊二烯的合成与应用

从聚合机理入手,对反应注塑成型聚双环戊二烯(PDCPD)的合成方法、性能及用途进行了综述。     

Rheokinematics for product development—Formulation screening in rotational rheometers

Product formulations for industrial processes are typically developed at laboratory scale. However, the mixing conditions are not easily mimicked in the laboratory. A rotational device is proposed in this study as a fast laboratory-scale formulation development, which enables mimicking the mixing conditions in the industrial process. The geometrical configurations of the rotational device are from rheometry devices (plate-plate and cone-plate). The main advantages of this method are the small amounts of raw materials and shorter testing times. This methodology is applied to an industrial case study, the reaction injection molding (RIM) process. The mixing length scales evolution in the rotational rheometer were matched to those in RIM machines. The main novelty of this study is the introduction of a protocol that bridges the processing conditions at laboratory using small amounts of raw materials to high throughput continuous flow reactors.     

Reactive processing of acrylic–polyurea interpenetrating networks: reaction kinetic studies

Interpenetrating networks (IPNs), comprising a crosslinked acrylic polymer as one component and either a polyurea, a segmented copolyurea or a copoly(urea–isocyanurate) as the other component, have been formed by reaction injection moulding (RIM). The effects on the processability and the formation of the IPNs of (i) the crosslinker concentration in the acrylic component, (ii) the functionality of the amine‐functionalized polyether used for the polyurea, and (iii) the weight fractions of acrylic components are evaluated. Reaction kinetics during RIM processing of the IPNs are studied using adiabatic temperature rise (ATR) measurements. The macroscopic structures of RIM materials, determined via optical microscopy, are used to assess the mixing characteristics operative during reactive processing of the various IPNs. The results are interpreted in terms of differences in the rates of polymerization and in the solubilities of the acrylic‐ and polyurea‐forming components. © 2001 Society of Chemical Industry