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SPE Library content related to rheology
Characterization of poly(deamino-tyr-tyr carbonate hexyl ester)
A class of poly(amino acids) often used in medical and pharmaceutical applications forms potentially useful extended associations above a critical concentration.
Microcellular processing of biobased, biodegradable polymer blends
Using microcellular injection molding to prepare renewable polymer composites could lead to components with lower cost, improved material properties, and an extended range of applications.
Comparison of Carbon Footprint of Standard Thermoplastic Urethane (TPU) and TPU from Renewable Resources
Merquinsa has developed Pearlthane® ECO, based upon polyols derived from various plant sources. The driving force to develop this bio TPU was our interest in creating a more sustainable product offering for companies and brands to choose from. These products, with very similar thermal, mechanical and rheological behaviour to standard TPU’s, have been widely accepted in the marketplace and are affording design engineers performance with sustainability. Although conceptually it is believed that producing TPU parts from bio based products is more environmentally friendly, Merquinsa will quantify and compare the greenhouse gas (GHG) emissions to validate this belief with hard science. The quantification of greenhouse gas (GHG) emissions associated with the production of a product is commonly referred to as the “carbon footprint”. PAS 2050 is a method prepared by the BSI British Standards for assessing the product life cycle GHG. For the purpose of this comparison, the lifecycle is defined as beginning with raw material manufacture, either from agricultural or petrochemical inputs, through to the delivery at our customer’s facility. This is commonly referred to as the cradle-to-gate approach. Any process at customers beyond this point will be similar for the Pearlthane® ECO and standard Pearlthane® TPU materials.
Characterizing the cure shrinkage of an epoxy resin in situ
A pair of modified rheology and gravimetry techniques successfully measure and describe the evolution of the volumetric effects of an epoxy system during processing.
Revisiting Boltzmann kinetics in applied rheology
The dynamic viscosity of resins undergoing soft gelation shows a marked sigmoidal shape, suggesting that similarly shaped functions might be considered for model predictions.
Structure and rheology correlation in polymer nanocomposites
Flow-reversal experiments and x-ray analysis show that the morphology of polymer nanocomposites evolves in time during and after processing.
Progress in Simulations for Short & Long Glass Fiber Thermoplastic Composites
The development and implementation of lightweight materials using fiber composites made by injection molding represents an engineering challenge due to the inability to control the fiber orientation in the required direction of mechanical demand. This paper presents progress in developing the capability of predicting fiber orientation in simple and complex flow geometries for highly concentrated short-glass-fiber suspensions and the extension of this approach to long-glass-fiber suspensions. Three important aspects included in the approach are the implementation of new theories to model fiber orientation the evaluation of model parameters from rheological experiments and the use of stable numerical methods based on discontinuous Galerkin finite-element method.
Counterpressure for microcellular injection molding
Applying different gas pressures at the melt stage improves parts production by controlling foaming and viscosity.
MICROSTRUCTURAL STUDY OF GRAPHITE FILLED POLYETHYLENE TEREPHTHALATE NANOCOMPOSITES
Nanographite (NG) produced from milling by high pressure homogenisation was compounded in a Twin Screw Extruder with Polyethylene Terephthalate (PET). The resultant PET-NG pellets, produced in a variety of compositions (0-2% w/w) were subjected to Rheology, DSC, Electrical Resistivity and Tensile Analysis. No nucleation of the PET was noted even at low concentrations - 0.1%w/w NG. Viscosity of the blends was increased with addition of NG thus allowing for greater continuity of the fibres spun at the faster haul off rate.
A NOVEL MINIATURE MIXING DEVICE FOR POLYMERIC BLENDS AND COMPOUNDS
Polymeric compounds and blends are typically developed via a mechanical mixing process during which time the ingredients are subjected to both shear and extensional deformations. The overall integrity of said compounds strongly depends upon the shear and extensional rheological properties of the polymeric matrix. In addition, the rheological properties also control the final quality and commercial attractiveness of the final products. Often times when working with new experimental fillers and polymers, material quantities may be available in extremely limited amounts thereby constraining material compounding protocols and the physical property characterizations associated therewith. A new miniature mixer has been developed to monitor and optimize the preparation protocol of various polymeric compounds and blend systems. The effect of mixing time and other basic processing parameters on the shear and extensional rheological properties of said compounds is examined in order to understand the effect of undermixed and/or overmixed conditions on the rheological properties and thus the quality of the final products. Results from said new miniature mixer are compared with the results from other conventional mixing techniques in order to assess the scalability of the new mixing protocol.
THERMAL AND RHEOLOGICAL STABILITIES OF PE AND PP DUE TO REPEATED PELLETIZNG
It is known that polymers properties could change due to repeated exposure to high temperatures and shear during processing and recycling. In this research the rheological and thermal properties of polyethylene (PE) and polypropylene (PP) were investigated. A twin screw extruder (Farrel FTX20) was used to expose PE and PP to repeated thermal history during pelletization. PE and PP were exposed to thermal histories up to 12 times during pelletization and re-pelletization processes. The rheological and thermal properties of the virgin polymer were compared to the re-pelletized ones. It was noticed that the melt viscosity of PE increased and that of PP decreased as the polymer was exposed to repeated pelletization. Additionally, the evaluated thermal properties of those of PE were not significantly changed, whereas, those of PP were affected.
USING MELT FLOW INDEX TO CHARACTERIZE SOME RHEOLOGICAL USING MELT FLOW INDEX TO CHARACTERIZE SOME RHEOLOGICAL
This paper is a sequel to a previous publication that was presented at ANTEC '08. That paper addressed a variety of uses of the Melt Flow Index (MFI) equipment, which were achieved by changing the heating temperature, the dwell time, and load. Some of these conditions were used to judge the temperature and / or load sensitivity of polyethylene (PE) and polypropylene (PP).In the current paper we will show a new set of applications for the MFI equipment. Some of polyolefin's properties that are presented here and could be characterized by MFI equipment are; melt density, extrudate swell, and viscosity. These properties were measured and compared for high density PE (HDPE), linear low density PE (LLDPE), low density PE (LDPE), and PP.
FOAMING BEHAVIOR OF MELT BLENDED POLYLACTIDE-CHITIN COMPOSITES
This study details the fabrication and foaming of melt blended polylactide (PLA) and chitin composites. The chitin used for compounding was as-received and in nano-whisker form, which were produced by an acidhydrolysis technique and their morphology was examined with Transmission Electron Microscopy. The composites were characterized for their thermal and rheological behavior. Chitin was found to decrease the thermal stability but increase the crystallinity of PLA. Addition of chitin was also found to reduce the viscosity of the composites even though chitin is a stiffer phase. The reason for this observation is believed to be due to the hydrolysis of PLA during melt blending of chitin in suspension. Foam samples were produced by a two step batch foaming technique and the expansion behavior was correlated with the visco-elastic observations.
SURFACE ENHANCEMENT OF TPO POLYMERS WITH IMPROVED FLOW AND SCRATCH PROPERTIES
Detailed application data is presented for the newly developed additive formulations designed for their use in surface enhancement of TPO polymers with improved flow and scratch properties. Improvements in impact properties and talc dispersion have been achieved with newly developed additives. Excellent scratch resistance performance has been achieved in TPO when used at 1-3% loadings without negatively affecting key physical properties. Recent work conducted on flow and release property enhancers for polyolefins are discussed. It is shown that significant performance improvements in PP /TPO polymers can be obtained at low loadings of these process aids. In addition to mechanical properties, rheological data is presented. It is shown that tailor making the additive formulations can achieve optimal scratch performance required for automotive interior/exterior applications.
SHEAR AND EXTENSIONAL RHEOLOGY OF CARBON NANOFIBER/POLYSTYRENE MELT COMPOSITES
The rheological behavior and morphology of polystyrene / carbon nanofiber (PS/CNF) composites in their melt phase have been characterized through experimental measurements. Viscosity measurements of the PS/CNF composites in the linear viscoelastic regime show the ratio of the transient extensional viscosity to the transient shear viscosity to be greater than three, the Trouton ratio. This behavior is believed to be due to differences in the flow induced orientation of the CNFs in shear and extensional flow. The orientation development of the CNFs were analyzed by TEM and optical microscope and considered for the relationship to rheological behavior.
MULTILAYER RHEOLOGY EFFECTS IN COEXTRUDED STRUCTURE DESIGN
Multilayer coextrusion is a process in which two or more polymers are extruded and joined together in a feedblock or die to form a single structure with multiple layers. This paper will discuss techniques for measuring experimental rheology data for monolayer and multilayer structures. These data will then be used to show the effects of multilayer rheology in the design of coextruded structures.
ON-LINE OPTICAL MONITORING OF NANOCOMPOSITE COMPOUNDING
On-line monitoring of compounding of PA6 with nanoclay is examined to investigate the level of exfoliation and degradation under a variety of conditions in real-time. On-line rheological and optical reflectance measurements are compared with off-line analyses of compounded samples to investigate the relationship between these readings and exfoliation/intercalation and/or degradation of the nanocomposite. The effect of the processing (twinscrew/ single-screw temperature and screw speed) on the resulting melt quality and the ability to assess this quality in real-time is discussed.
ON-LINE OPTICAL MONITORING OF NANOCOMPOSITE COMPOUNDING
On-line monitoring of compounding of PA6 with nanoclay is examined to investigate the level of exfoliation and degradation under a variety of conditions in real-time. On-line rheological and optical reflectance measurements are compared with off-line analyses of compounded samples to investigate the relationship between these readings and exfoliation/intercalation and/or degradation of the nanocomposite. The effect of the processing (twinscrew/ single-screw, temperature and screw speed) on the resulting melt quality and the ability to assess this quality in real-time is discussed.
EXPERIMENTAL STUDY OF EXTRUSION AND SURFACE TREATMENT OF ORGANO CLAY WITH PET NANOCOMPOSITES
The use of organoclay in polymers is expected to increase on average annually by about 5 percent. This paper describes melt blending techniques using PET nanocomposites containing commercially available organoclays with different percentage of surfactant coatings. This paper will also evaluate the morphology and mechanical properties of the composites using a range of techniques like scanning electron microscope melt rheology andthermal analysis. Comparisons will be made between properties of amorphous and semi crystalline films in terms of surfactant used and material properties. It will be demonstrated that the quantity of surfactant used with the organoclays can significantly affect dispersion and properties of composites produced.
RHEOMETERS FOR HIGH-THROUGHPUT POLYMER CHARACTERIZATION
High-throughput rheological characterization has applications in many industries but dealing with molten polymers poses special challenges. For purposes of structure determination however rheology has potential advantages over GPC. There is currently no commercial rhometric device that can make rapid measurements on very small samples of molten polymers. However descriptions of several devices designed to accomplish this have been described in presentations and publications. The deformations involved include capillary torsional shear and squeeze flows. Each of these approaches has its advantages and disadvantages and it is not yet clear which if any of them will be able to meet the stringent requirements of high-throughput characterization.
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