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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Prediction of Theweld-Line-Induced Strength Reduction for Nylon6 and its Nanocomposites
The position and strength of the weld-line have important influences on injection molding plastic products qualities. This paper discussed the weld-line in Nylon6 and its nanocomposites by formulae. Utilizing linear regression, referencing existing self diffusion mathematics model, semi-experimental formulation was found to calculate the degree of bonding. The influence of thickness and processing parameters, such as melt temperature, mold temperature, holding pressure and injection velocity, were considered. Compared with experimental results of PA6 and nano-composite PA6 specimens with thickness 1.0mm, 2.5mm under different processing conditions, the maximum of error by formulas is 2.56% of PA6 and 1.78% of nano-composite PA6, respectively.
Effects of Processing Parameters on Optical Properties of Injection Molded Polystyrene Parts
In this paper, PS products qualities are discussed by experiments to find the relations between processing parameters and residual stresses, optical properties. Residual stresses are measured by polarimeter. The variance of processing parameters is considered when residual stresses distribution and polarimetric interference are measured. Also the optical property of transparency and haze are measured by transmittance meter. From the experiments results, we find that processing parameters have great effects on residual stresses and haze but little effects on transparency.
Influence of Geometrical Factors on Cavity Pressure during the Injection Molding Process
The influence of the thickness of plastic parts on the behavior of the cavity pressure during the injection molding was studied. The instrumentation of molds for a modification of a normalized test specimen for impact was proposed, placing pressure transducers in the more critical zones of the parts. The evaluation of the molds was made using solid modelator software in three dimensions and a simulator software of the injection process with different resins. The simulation results demonstrated that the thickness of a part affect the behavior of the cavity pressure during filling and post-filling phases, the cooling and the dimensional stability of the part.
The Influence of Processing Variables and Two-Way Interactions on the Weldline Strength of Injection Molded Parts
Strength is an important performance of the injection molded parts. Obtaining sufficient mechanical strength is quite needed for some parts. Weldline developing in the part significantly reduces the strength of the parts. Strength of the parts is affected by many factors. In this report, An L27 Orthogonal Array designed based on the Taguchi method was conducted to investigate the effect of process parameters and two-way interactions on the strength of injection molded parts with weldline and without weldline. The main effects of the factors and two-way interactions were estimated, and the relative significances of each processing parameter and interaction on the strength were analyzed.
Mold Cooling Analysis for Injection Molding Process Using Fast Multipole Method
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 3D 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 based on FMM for mold region and a CVFEM for part. The FMM algorithm dramatically reduces the complexity of matrix-vector multiplication involving a certain type of dense matrix, which can arise out of many physical systems. The present analysis is then used to predict the temperature field for a 3D plastic part geometry.
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.
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