The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Evaluation of Molecular Orientation of Weldline Region in Polycarbonate by Laser Raman Spectroscopy
Molecular orientation in weldline region in injection molded polycarbonate was investigated by polarized laser-Raman spectroscopy. The relative intensity ratio of two specific peaks in a spectrum was determined as an index of molecular orientation in accordance with an earlier report. The intensity ratio of the peaks showed the highest value at the point ca. 30 ?m apart from the V-notch at the surface of the specimen. The orientation direction was found to be parallel to the weldline. The birefringence, ?n, of this point was estimated to be 2.64×10-3 from the results of another study to determine the relationship between Raman peak intensity and birefringence. This value corresponded to ca. 2.5 % of the intrinsic birefringence of polycarbonate, 0.106. Meanwhile, the birefringence of V-notch itself was calculated to be 0.59×10-3, lower than that of the surroundings. Although a similar tendency was found at the area ca. 100 ?m inside from the surface, the birefringence itself was slightly lower than that of the surface. These results suggest that molecular orientation increases near the weldline due to convergent flow, while the molecules at the interface of the weldline relax. Thus laser-Raman spectroscopy provides some important clues to understand the flow behavior around weldline.
Crystallinity Development during Spinning of Polypropylene Part II: Fiber Spinning Model Validation
The original Doufas-McHugh (1,2) two-phase microstructural/constitutive model for stress-induced crystallization (SIC) is validated for its predictive capability using on-line Raman crystallinity and spinline tension data of two Dow homopolymer polypropylene resins. The material parameters – inputs to the model – are shown to be obtained from lab scale material characterization data: oscillatory shear (DMS), rheotens and DSC. The same set of two SIC material parameters are shown to be able to predict the crystallinity profiles along the spinline and tension very well overall. The model captures quantitatively the effect of take-up speed, throughput and MFR on crystallization rate due to SIC
Rheometer Compliance Effects: Viscoelastic Measurements on Small Molecule Glass Formers and a PDMS Rubber
Effects of instrument compliance can induce large errors on shear measurements of elastic and viscoelastic properties of materials [1,2]. These effects are caused not only by the transducer but also the machine itself (load frame), and the rheometer fixtures. We present examples of rheometer compliance effects on the measurement of the material properties of small molecule glass formers and a commercially available polydimethysiloxane (PDMS) rubber. A TA Instruments ARES Rheometer was used with a strain gage transducer (Honeywell-Sensotec). Stress relaxation, aging experiments, and dynamic frequency sweep experiments were performed. We also propose a procedure to correct for compliance effects in stress relaxation experiments and dynamic frequency sweep experiments. Suggestions are made for both instrument and experimental design to avoid and/or reduce compliance effects.
Effect of Two Compatibilizers Having Comonomer in Polypropylene/Clay Nanocomposites
Nanocomposites prepared by PP(Polypropylene) based compatibilizers modified with GMA(Glycidyl methacrylate) and HEMA(Hydroxyethyl methacrylate) were used to investigate the clay dispersion and mechanical properties of them. XRD patterns showed the improvement of dispersion through clay intercalation according to the compatibilizers and comonomer. GMA modified polypropylene gave the better mechanical properties of the nanocomposite with respect to the balance of Flexural modulus (FM) and Notched izod impact strength(IS). Compatibilizers with comonomer commonly have higher grafting yield and lower melt flow rate than those of comonomer free. And they enhanced the clay dispersion and mechanical properties of nanocomposites. Optimum ratio of monomer to comonomer for nanocomposites having better mechanical properties is about 1 to 1 ratio.
Improving the Toughness of Poly(Lactic Acid)(PLA) through Co-Continuous, Immiscible, Biodegradable Blends with PHA
Poly(lactic acid) (PLA) and Polyhydroxy octanoate (PHO) were melt blended using a torque rheometer in the ratios of 80/20, 60/40, 50/50, 40/60, and 20/80. In this study, the rheological, thermal, and mechanical properties of the blends were investigated. Differential scanning calorimetry showed that the two components in these blends were found with two crystalline phases and two amorphous phases confirming the coexistence of two immiscible components. The addition of modified PHO in PLA increased the toughness of the PLA and increased the elongation to break more than 158%. Results obtained from rheological test indicated that the melt viscosities of PLA/modified PHO decreased as a function of modified PHO content.
Application of Composites in the Sulfur Acid Production
Chemical resistant epoxy vinyl ester resins serve the needs of a wide range of process in sulfur acid production at petrochemical enterprises with final FRP products, such as chimney liner, process pipes, ducts and scrubbers.Operation of the process equipment does not exclude occurrence of extreme situations at the moment of start-up and stop of manufacture: rises of temperature, influences of more concentrated environments, mechanical loading. The results of physical property testing after 3 years of service of the FRP products, such as chimney liner, pipes, ducts exposed to sulfur acid production, are considered.The damages of chemically resistant layer of FRP connected with extreme situations are discussed.The maximum temperature of application of chemically resistant layer, established during researches in a sulfur acid of different concentrations, is presented in this article.
Axial Transport in Kneader Reactors
Whereas for bulk and liquids, gravity is the main transport mechanism for conveying material through vessels, different transport mechanisms are involved for conveying high viscosity fluids. Screws have been used for forced conveying of all those material behaviors and are well described in literature. This paper describes transport mechanism for viscous fluids in kneader reactors, which are not covered in that literature so far. In those reactors the fluid can flow backwards due to the open flight design and the net flow has to be computed as a cascade of communicating chambers. Empirical data is presented both on pilot and industrial scale equipment and a model is presented.
Oil Extension of Olefin Block Copolymers
The Dow Chemical Company introduced INFUSE™ Olefin Block Copolymers in June 2006. Olefin Block Copolymers are polyolefins with blocks of hard (highly rigid) and soft (highly elastomeric) segments. Because of this block structure, Olefin Block Copolymers break the traditional relationship of flexibility and heat resistance, while offering significantly improved compression set and elastic recovery. This paper will discuss how the performance balance of these new resins can be further enhanced by incorporation of oil, allowing Olefin Block Copolymers to enter markets and applications that are currently served by high performance soft thermoplastic elastomers.
Nanomechanical Properties of Ultrathin Polymers
We have developed a novel microbubble inflation method to measure the viscoelastic properties of ultrathin polymer films over a range of stresses and temperatures. The method is capable of measuring the biaxial creep compliance response of films as thin as 13 nm. We summarize some prior experiments that show a dramatic stiffening of both poly(vinyl acetate) (PVAc) and polystyrene (PS) in the rubbery regime at the reduced thickness but a material specific degree of reduction in the glass transition temperature. In addition, we show preliminary results of creep recovery experiments and thin film rupture images that suggest that the method can be used for a broader range of mechanical measurements than originally anticipated.
Evaluation of Nanoparticulate Fillers for Shape Memory Polyurethane Nanocomposites
The objective of this work was to evaluate nano and micro size fillers on shape memory (SM) properties of polyurethane nanocomposites. The matrix material was synthesized from diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD), and polycaprolactonediol (PCL). Organoclay, carbon nanofiber, carbon black, and silicon carbide were selected as fillers. Our results indicate that exfoliated organoclay augments SM performance significantly, while other fillers diminish it by interfering with the soft segment crystallinity and/or hard segment phase separation. Better SM properties with organoclay can be attributed to mechanical reinforcement without interfering with crystallinity and phase separation.
Analysis for Pressure Profile Behavior of Mixtures of PS with R22 Blowing Agent in a Single Screw Extruder
Both experiments and numerical studies were conducted to investigate the PS foam screw characteristics with R22 blowing agent in a single screw extruder. Five thermocouples and pressure transducers are equipped in this extruder. R22 is the blowing agent for this study, which is injected into the extruder at 18.4D with temperature around 200°C. Without the blowing agent, it is found that the pressure monotonously increases along the screw axis after the distance of 24D. However, the pressure profile changes after the blowing agent is injected. A hybrid FEM/FDM was applied to predict the Q-P characteristic curves for PS and PS foam extrusion.
Use of Dimensionless Numbers in Analyzing Injection Molding and Extrusion Processes
Dimensionless analysis is a powerful tool in analyzing the transient heat transfer and flow processes accompanying melt flow in an injection mold or cooling in blown film,to quote a couple of examples. However, because of the nature of non-Newtonian polymer melt flow the dimensionless numbers used to describe flow and heat transfer processes of Newtonian fluids have to be modified for polymer melts. This paper describes how an easily applicable equation for the cooling of melt in a spiral flow in injection molds has been derived on the basis of modified dimensionless numbers and verified by experiments. Analyzing the air gap dynamics in extrusion coating is another application of dimensional analysis.
Difference in Thermoforming Processability Observed for Three High Impact Polystyrenes
The difference in thermoforming processability of three STYRON* high-impact polystyrene (HIPS) resins was investigated. Experiments were performed on a moldbottle thermoformer as well as a step-case tool thermoformer. Disparities observed were analyzed in terms of differences in rheological properties of the resins. Conclusions were drawn as to which rheological characteristics the resins should possess in order to give the largest temperature processing window coupled with high quality thermoformed parts.
Mechanical Hole Burning Spectroscopy in the Vicinity of the ODT for an SIS Block Copolymer
We describe results for experiments in which a novel rheological technique is applied to a styrene-isoprene-styrene triblock copolymer in the vicinity of the order-disorder transition. Mechanical Hole Burning Spectroscopy (MSHB) was developed to probe dynamic heterogeneity in polymers. In this technique, a large amplitude oscillatory strain (LAOS) is imposed on a sample as a perturbation, and is followed by a small step strain. The relaxation response is then compared with that without the LAOS perturbation. It has been assumed that mechanical holes for heterogeneous systems. For homogeneous systems no hole would result. Here the heterogeneity of a tri-block copolymer was investigated in the vicinity of its order-disorder transition and it was found that the mechanical hole intensity gradually decreases as the phase boundary is approached from the ordered regime. At the one-phase or the disordered region, no apparent holes were observed.
Nanocomposites Based on Ionic Liquid Modified Clays
Cationic nanoclays were treated with various novel modifiers based on ionic liquids of different structure and/or molecular weight. Initial experiments with short chain dialkyl imidazolium and monoalkyl pyridinium based modifiers were followed by treatments with phosphonium based ionic liquids having longer chain cations. The modified clays, characterized by spectroscopy, thermal analysis, microscopy and X-ray diffraction, were melt compounded with polypropylene. The effects of the ionic liquid structure and chain length on extent of clay dispersion, intercalation and thermal stability were investigated.
Prediction of Polyethylene Melt Index and Molecular Weight Distribution Using a Capillary Rheometer
Polyethylene, PE, is characterized by molecular weight (MW), molecular weight distribution (MWD) and density. Melt index (MI2) is measured in the QC lab and is used as an indication of resin MW. Melt flow ratio (MFR or MI20/MI2) is a calculated QC lab number, which is used as an indication of MWD. Density is a measure of crystallinity. In polyethylene production, having fast reliable feedback on MW and MWD is critical for producing high quality resins. This article describes a novel/unique idea how a capillary rheometer can be used to predict MI2 and MI20.
Solid-State Shear Pulverization as a Real-World Process for Polymer Blends and Nanocomposites
Solid-state shear pulverization (SSSP) is an innovative processing technique that has proven to effectively disperse nanoscale structural entities to achieve compatibilized polymer blends and exfoliated polymer nanocomposites. The SSSP apparatus, which is a modified twin-screw extruder, can continuously process polymer blends and nanocomposites without the use of heat, solvent, or chemical modifiers. For an insight into this unconventional process, the effects of different processing parameters are evaluated using several polystyrene-based blends as base systems. The manner by which the materials deform, mix, and disperse depend strongly on the type of polymers as well as the configuration of the mixing and pulverization zones in the SSSP apparatus. Such key processing variables as residence time and throughput are also considered and compared with typical values in conventional melt extrusion.
A New Approach to Seatback Design – Blow Molded Seatbacks
The automotive industry is facing increasing pressure to reduce weight and cost in vehicle design and development. Blow molded seatbacks for rear seating offers an opportunity to reduce weight and cost and meet US and European government regulations, including FMVSS 207, 210 and 225 in the US and ECE 17 (luggage retention) in Europe.This new generation of rear seating design has been achieved through the combination of innovative design, blow molding processing and an unfilled thermoplastic that performs over a wide range of temperatures. The plastic seatback eliminates the need for steel reinforcements to pass the loading requirements.This technology was first introduced by Dow Automotive in 2000 for rear seatbacks. Several prototype designs were tested and optimized for different latch configurations to meet the federal requirements. This led to the successful introduction on the 2006 Audi TT in Europe. This resulted in a mass savings of 1.2Kg. High stiffness is achieved through closed sections within the double shell blow molded structure. Blow molding also offers reduced development time and tooling costs when compared to more traditional steel designs.
Compactibilization Efficiency of Maleic Anhydride Grafted High-Density Polyehtylene with and without Zinc Neutralization for High-Density Polyethylene/Polyamide 6 Blends
A high-density polyethylene with grafted maleic anhydride units has been investigated as a compatibilizer for high density polyethylene with polyamide 6. The material acts as an effective compatibilizer, causing a marked reduction in dispersed phase size as well as an increase in tensile strength and toughness. Compatibilizer also affects the glass transition temperature, crystallization kinetics and amount of crystalline material for certain blend compositions. The addition of zinc cations, which are effective in increasing ethylene-acid copolymer compatibilizer performance in low-density polyethylene/polyamide blends, has little, if any, effect on compatibilizer performance in these high-density polyethylene/polyamide blends.
The Nanoporous Morphology of Photopolymerized Crosslinked Polyacrylamide Hydrogels for DNA Electrophoresis
Photopolymerized crosslinked polyacrylamide hydrogels are emerging as an attractive electrophoresis sieving matrix formulation owing to their ideal range of pore size, rapid polymerization times and the potential to locally tailor the gel structure through spatial variation of illumination intensity. This capability is especially important in microfluidic systems, where photopolymerization allows a gel matrix to be precisely positioned within a complex microchannel network. The achievable level of separation performance is directly related to the nanoscale gel pore structure, which is in turn strongly influenced by polymerization kinetics. Unfortunately, detailed studies of the interplay between polymerization kinetics, mechanical properties, and structural morphology are lacking in photopolymerized hydrogel systems. In this paper, we address this issue by performing a series of in-situ dynamic small-amplitude oscillatory shear measurements during photopolymerization of crosslinked polyacrylamide electrophoresis gels to investigate the relationship between rheology and parameters associated with the gelation process including UV intensity, monomer and crosslinker composition, and reaction temperature. In general, we find that the storage modulus G' increases with increasing initial monomer concentration, crosslinker concentration, and polymerization temperature. We also find an optimal UV intensity level at which the resulting hydrogels exhibit a maximum value of G'. A simple model based on classical rubber elasticity theory is used to obtain estimates of the average gel pore size that are in agreement with corresponding data obtained from analysis of DNA electrophoretic mobility in hydrogels polymerized under the same conditions.
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