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On-Line Morphology Control Features of Continuous Chaotic Advection Blenders
Blending has been typically regarded as a mixing process, so the variety of producible structures in melts and attainable physical properties of plastics have been constrained. In contrast, a variety of polymer blend morphologies have been deliberately constructed in situ with novel blenders based on chaotic advection. Operation of a continuous chaotic advection blender is described that allows on-line control of blend morphology development or of the arrangement of particulate additives in polymer melts. Notably, features allow efficient structure-property-composition optimization, the production of extrusions with periodic or graduated properties, and assembly of functional devices.
New Generation of TPUS; Short-Term Characterization and Applications
TPU or thermoplastic polyurethane belongs to the thermoplastic elastomers or TPE family. TPUs combine the processability of thermoplastics and the flexibility of elastomers. TPU could be tailored to cover a wide range of hardness (about 70D to 80A) by changing its chemistry, such as the chemical components or molecular weight, or the type and content of additives. Traditionally, adding plasticizer to TPU resin produces the softer grades down to shore hardness of 60A. A new trend in producing soft TPU grades is to manufacture them free of plasticizers. This is achieved by controlling the TPU chemistry.In this work, Elastollan® C75A15HPM (which is plasticizer free) is compared to Elastollan® C75A15W (which has plasticizer). Different methods are used to characterize the short-term properties of these materials. Tensile, thermo-mechanical, tear, melt-viscosity, and surface properties are discussed. The relation of these properties to processing and application is described.
Processing - Structure - Property Relationships in Bicomponent Blown Film Extrusion Using Online Raman Spectroscopy
Crystallinity was measured in real-time using online Raman spectroscopy during blown film coextrusion of polyethylene (LDPE) and polypropylene (PP). The effect of blow-up ratio (BUR) and take-up ratio (TUR) on the crystallinity development of individual components, PP and LDPE, is reported. The kinematics of the process was found to be controlled by polypropylene, the component which freezes first. Temperature measurements revealed the appearance of double plateaus in the profile, one at the onset of crystallization of PP and the other near crystallization of PE, for some processing conditions.
Lubrication Mechanism of Poly(Vinyl Chloride) Compounds: An Understanding of Lubricant Failure at Higher Processing Temperatures
Poly(vinyl chloride) (PVC) compounds require metal lubrication and polymer to polymer lubrication for good processing performance. Much of the mechanism for PVC’s lubrication has been elucidated over the years. One point has not been completely understood, that is the “lubricant failure” at higher processing temperatures where the compound becomes more brittle. This is contrary to what might be expected with better PVC fusion (gelation). This paper discusses the mechanism involved, which is lubricant inversion, where the lubricant goes from the continuous phase to becomes the discontinuous phase.
The Influence of Painting Systems on Low Temperature Deployment Behaviour of Airbag Covers
Paint systems have influences on the low temperature Airbag Deployment of airbags. This influence is related to several items like:Type of paint which is usedMaterial properties of the paintKind of adhesion promotingPolarity modification of the substrate. (Polarity increase)Use of an adhesion promoting primerSarlink 3939DB-01 unpainted withstands the airbag deployment requirements till –35 C. In order to find out how big the influence of the paintsystems can be, Sarlink 3939DB-01 has been tested with 2 paint systems from Mankiewicz: a “Solvent Based” and “Waterborne” system, as well as with 2 other waterborne systems from other paint manufacturers. These systems have been tested in combination with an adhesive promoting primer or with a flame-treated surface, without primer.Furthermore 2 new Sarlink ® development products have been tested in comparison with Sarlink® 3939DB-01 with the waterborne system of Mankiewicz in combination with their primer system, to investigate the possibility to improve low temperature properties without changing the paint system.The following results were obtained:Both (waterborne and solvent based) paint system have a negative influence on the low temperature behavior at testing temperatures below –55C, which is regarded as representative for high speed airbag deployment around –35C.Water-borne paints used in this study outperform the solvent-based paint!Flame treatment instead of the use of an adhesive promoting primer, improves the low temperature behavior substantially.The 2 new development products outperform the 3939DB-01 in low temperature behavior, with only slightly lower stiffness for 04EW033 at 80° C. At 20° C both 04EW033 and 034 have a higher stiffness.One of the development products 04EW033 in the painted state performs even better than the Sarlink 3939DB-01 in the unpainted state and can overcome the negative effects of the paint.The findings from our investigations have been confirmed by testing at our Tier1 customers rec
Effect of Compatibilizing Agents on Clay Dispersion of Polypropylene-Clay Nanocomposites.
In this work, polypropylene-clay nanocomposites were obtained and studied by using three different coupling agents, glicidil methacrylate (GMA), acrylic acid (AA) and maleic anhydride (MA). Three different clays, natural montmorillonite (Closite Na+) and chemically modified clays Closite 20A and 30B have also been used. Nanocomposites were prepared by melt blending in a twin-screw extruder using two methods of preparation, with only one pass and two pass trough the extruder. The relative influence of each factor was observed from structural analysis by SAXS, and mechanical properties. The results were analyzed in terms of the effect of each compatibilizing agent and incorporation method in the clay dispersion and mechanical properties of the nanocomposite.
Compatibilization of Poly(Vinyl Chloride) with Polyamide and with Polyolefin with Poly(Lauryllactam-Random-Caprolactam-Block- Caprolactone)
The compatibilization of various poly(vinyl chloride) (PVC) blends was investigated in this study. The blends systems were PVC-polyamide 12(PA12), PVC-polypropylene (PP), and PVC-ethylene propylene diene rubber (EPDM) with a new compatibilizing agent, random-block terpolymer poly(?-lauryllactam-random-?- caprolactam-block-?-caprolactone) or systems containing these copolymers. It was compared to previous studies using poly(?-lauryllacatam-block-?-caprolactone) copolymer. This block copolymer was specially synthesized by reactive extrusion. Observation by scanning electron microscopy (SEM) reveals that compatibilized blends have a finer morphology than that of the noncompatibilized blends. Addition of 10 weight percents of block copolymer proved to be sufficient to give a significant improvement of the mechanical properties of the immiscible PVC blends at room temperature and high temperatures which are above glass transition temperature of PVC.For polyolefins, a three component compatibilizing system including maleated polypropylene, polyamide 12, and block copolymer was used.
Three-Dimensional Mold Cooling Analysis for Injection Molding Process
Mold cooling process in injection molding is critical in order to reduce cycle time and improve the quality of molded part. In this paper, a fully three-dimensional mold cooling analysis is developed. Mold heat transfer is considered as cyclic-steady, three-dimensional conduction: heat transfer within the part is treated as a three-dimensional transient heat conduction; heat exchange between the cooling channel surfaces and coolant is treated as a cycle-averaged steady state three-dimensional heat conduction. Numerical implementation includes the application of a hybrid scheme consisting of a 3D BEM for mold region and a CVFEM for part. These two analyses are iteratively coupled in order to match the temperature and flux at the interface. The present analysis is then used to predict the temperature field for a 3D plastic part geometry.
Transient Solutions and Experimental Observations Casting Process Accompanied by Flow-Induced Crystallization
The dynamics and stability of film casting process including crystallization kinetics have been investigated using a 2-D model with finite element method (FEM). The transient solutions of extensional deformation processes such as film casting, film blowing and fiber spinning are essential for the comprehensive analysis of their dynamics, but they are found extremely difficult to obtain if flow-induced crystallization (FIC) occurs, while it is rather a simple exercise without it. Once the transient solutions of film casting process with flow-induced crystallization were obtained, the information on this transient behavior becomes extremely useful for the optimization and stabilization of the process. Experimental corroboration using isotactic polypropylene (iPP) has been achieved.
Temporal Profiles of Spinline Variables in Fiber Spinning Process Accompanied by Flow-Induced Crystallization
The transient behavior of fiber spinning process when flow-induced crystallization occurs on its spinline has not been reported yet in the literature, whereas the steady state behavior has been well understood and simulated by various researchers as well as the transient behavior without crystallization on the spinline. In this study, this particular issue has been investigated incorporating flow-induced crystallization into the mathematical model of the system and then devising proper numerical schemes to produce the temporal pictures of the system. It turns out that the difficulty for obtaining the transient solutions of fiber spinning accompanied by flow-induced crystallization lies in the extreme sensitivity of the spinline velocity toward the fluid stress level at the spinneret. With the successful transient solutions of fiber spinning with flow-induced crystallization, nonlinear stability analysis has been investigated to advance an understanding of the process.
Properties of Rapidly Formable Composite Bipolar Plates from Graphite Filled Wet-Lay Composite Materials
The wet-lay sheets consisting of thermoplastic (Poly(phenylene sulfide) (PPS)) fibers, graphite particles and carbon fibers are generated and used to compression molding bipolar plates with gas follow channels. The bipolar plates have high electrical conductivity (in-plane), high corrosion resistance, excellent mechanical properties and thermal stability. The plates have in-plane conductivity of 270 S/cm, tensile strength of 57.5 MPa, flexural strength of 95.8 MPa and impact strength (unnotched) of 84.2 J/m. All these values exceed the industry's requirements or targets for composite bipolar plates. The through-plane conductivity (around 20 S/cm) and half-cell resistance of the bipolar plate indicate that the through-plane conductivity of the material needs some improvement.
Optimization of Laser Transmission Welding of Polymers Using Thermography
Due to the complexity of the interaction of material and machine parameters in laser transmission welding, there is still a lack of knowledge about the influence of process parameters and possible process optimization. One crucial factor is the heating behavior, especially of the absorbing partner, which can be determined by the material composition, but also by choosing appropriate processing parameters.Using an IR camera, analysis of the thermal response to laser beam, with respect to its temporal and spatial development, can be used to classify the plastics regarding laser beam weld-ability as well as to derive suitable parameters for the welding process. Results of investigations of different plastics and their modifications will be presented.
Flow Field Analysis during Quasi-Simultaneous Welding of Thermoplastics
In laser transmission welding of thermoplastics, there are process limitations due to a limited knowledge about the impact of all process parameters. This is partially due to limited access to the process zone for process monitoring. This paper will present the results from the application of a new on-line analysis method, with the aim to extend existing limits in laser transmission welding of thermoplastics, here with a focus on quasi-simultaneous welding. The method is based on the on-line visualization of the melt pool dynamics during the welding process. A correlation of the thermo-fluid dynamical processes in the melt zone with the process parameters and the resulting weld seam properties is realized. Technological information about the analysis method and results, taking into account key material properties and processing parameters, will be presented.
Mechanical Characterization of a Liquid Crystalline Polymer Nanocomposite
Vapor grown carbon nanofibers (VGCF), 60-150 nm in diameter, were mixed with Vectra A950 liquid crystalline polymer (LCP) and the mixture was extruded as 0.5-2 mm diameter filaments for use in creating composites with hierarchical structuring. VGCF is added to increase the strength, stiffness and conductivity of the LCP. Interesting mechanical and conductive behavior is expected owing to interactions between similarly scaled LCP fibrils and VGCF. LCP-VGCF filaments were characterized via tensile testing and fractography. The tensile modulus, failure strength and strain-to-failure were found to be sensitive to filament diameter, VGCF content and extrusion process. There was a noticeable increase in mechanical performance with decreasing filament diameter irrespective of VGCF content. Fracture surfaces showed hierarchical features from nanometer to micrometer scale and processing defects in the form of voids. In the following, the mechanical properties will be correlated to the microstructure and processing parameters.
Processability and Film Performance of Single Site SLLDPE/LDPE Blends
Traditionally for Linear Low Density PolyEthylene (LLDPE) blown film, blend strategies have been set up based on blends of Ziegler Natta catalyzed Linear Low Density PolyEthylene (ZN/LLDPE) and High Pressure Low Density Polyethylene (LDPE). For blends of dual reactor single site catalyzed Linear Low Density PolyEthylene (sLLDPE) and LDPE, however, these strategies do not necessarily apply.In this paper two sets of experiments are presented that compare sLLDPE/LDPE blends with ZN LLDPE/LDPE blends. It is shown that for sLLDPE/LDPE excellent bubble stability and superior optics can be achieved while maintaining a balanced set of film physicals.
Effect of Compatibilizer Molecular Weight on the Rheology of Polypropylene Nanocomposites
Melt compounding with a twin-screw extruder was used to prepare exfoliated polypropylene (PP) nanocomposites of organophilic montmorillonite clay compatibilized with maletaed polypropylene (PPgMA). Several grades of PPgMAs of different melt flow indices (MI) and molecular weights were analyzed for the effectiveness of melt exfoliation of organoclay. The extent of clay exfoliation in the nanocomposites was confirmed by X-ray diffraction spectroscopy. It was found that the nanoscale dimensions of the dispersed clay platelets led to significantly increased oscillatory shear flow properties. At a clay loading of 5 wt%, which is much smaller than that of conventional macrocomposites, the hybrid materials exhibited unbound increase of shear viscosity at low frequencies; and nonterminal low-frequency plateau in the linear storage modulus. The relative dynamic properties revealed a systematic trend with the state of exfoliation and dispersion in the nanocomposites.
Understanding Why Adhesion in Extrusion Coating Decreases with Diminishing Coating Thickness, Part I: Penetration of Porous Substrates
It is well known that in extrusion coating the adhesion of PE to paperboard and other porous substrates decreases with decreasing thickness. Several hypotheses are proposed for the origin of this decrease, including a reduction in time for oxidation, faster cooling in the air gap and more rapid quenching in the nip. A model of the penetration of the molten polymer into the substrate shows that the greatest effect is cooling in the nip; thinner coatings have less time to flow into the interstices of the substrate once contact with the chill roll is made. The model results agree well with experimental adhesion data from the literature.
Application of the Similarity Theory for Special Injection Molding Processes
Quality characteristics on injection molded parts are influenced by a large number of influencing factors and complex correlations. This applies to both standard injection molding processes and special processes, such as gas assisted injection molding (GAIM) and overmolding. In many cases, a closed analytical description of these correlations is not possible.One means of countering this problem is to employ the similarity theory. This creates simple correlations between the target parameter, different molded part geometries and the influencing factors.After discussing the fundamentals of the similarity theory, the characteristic numbers that describe the process are established for the special injection molding processes of GAIM" and "Overmolding". In a second step experimental investigations are presented for the mentioned processes in order to establish correlations between influencing parameters.For gas-assisted injection molding equations are derived on the basis of experiments with laboratory molds which make it possible to predict the gas bubble cross-section for different geometries. In the case of overmolding model laws are derived which can be used to transpose process settings or process conditions from model geometries to other geometries."
Cell Morphology, Surface Roughness, Impact and Odor of Microcellular Injection Molded Wood-PP Composites
This paper represents the investigations on the cell morphology, surface roughness, impact properties and odor concentration of microcellular wood fiber reinforced PP composites in injection molding process with different chemical foaming agents. The chemical foaming agent and wood fiber content strongly affect the microcellular structures of wood-PP composites. Microcells morphology (cell size, shape and distribution) were investigated using optical light and scanning electron micrographs. Charpy impact strength, impact resistance and damping index of the composites influenced by different chemical foaming agent type and content. Due to microfoaming, odor concentration and surface roughness significantly improved.
Flame Retardant Polypropylene Containing Functionalized Nano Clays
With the development of nano clay technology, new opportunities have emerged for imparting enhanced fire retardancy, mechanical and barrier properties to plastics.Polypropylene resins enjoy a large increase in consumption due to its cost/properties combination. However, one of its main shortcomings originates from its flammability. To remedy the flammability of polypropylene relatively large amounts of flame redardant additives have to be used. This in turn decreases the mechanical properties of the resultant compound.Consequently, the objective of the present investigation is aimed at exploring the effect of functionalized nano clays on the flammability retardation and mechanical properties of polypropylene. Commercial as well as novel functionalized nano clays were included in the study.Experimental results have shown that the burning mechanism of nano clay containing polypropylene compounds was completely changed due to formation of a char layer. Furthermore, 2.5% of bromine functionalized nano clays, reduced the required amount of conventional bromine containing fire retardants by 50% to meet UL 94 V-0 levels. The resulting fire retardant polypropylene compounds possessed higher modulus and strength while preserving the impact resistance compared with neat polypropylene.
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