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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Investigation of Re-Crystallization of Injection Molded TPO Unpainted Plaques
Thermoplastic olefins (TPO) are widely used in the automotive industry as painted exterior plastic parts such as fascias and bumpers. The overall production process includes injection molding of parts, surface treatment, painting and finally baking at 120°C for 30 min. During the injection process, residual stresses are generated by chain orientation and thermal gradients. After the paint process, more stresses and deformations are added. This work focuses mainly on baking conditions and the micro-structural changes as a source of final surface defects. As a first step, we used DSC to simulate the baking process and study the effect of injection molding and baking conditions on unpainted samples. By controlling the scanning rates and the residence time within the DSC furnace, this alternative technique can reveal some interesting results. Samples were also annealed in an oven in the same conditions then analyzed by DSC. The results of both approaches are compared and discussed.
The Effect of Cooling Air Aerodynamics on Bubble Instability in Blown Film
A numerical analysis using a renormalization group (RNG), k-? model and Fluent software was performed to predict the static pressure distribution around the bubble as well as the flow field of cooling air in the film blowing process. Bubble instabilities were experimentally studied using an in-line scanning camera system developed in our laboratory. The combination of experimental measurements and numerical analysis indicated that different bubble shapes led by various cooling rate produced significant differences in dynamics of bubble instability. When the gradient of static pressure along the axis of the bubble is minimized, the stability of the bubble increases.
Volumetric Orientation and Selective Placement of Platelets in Clay Nanocomposites by Chaotic Advection
Following first work reported last year, this paper presents additional information regarding novel polyamide-6/nanoclay nanocomposites having platelets volumetrically oriented and localized within alternating platelet rich and virgin polyamide layers of nano-scale thicknesses. These novel nanocomposites were produced with a continuous chaotic blender (CCB). A variety of structural arrangements among platelets in extruded films are presented. Methods are applicable to other polymer types and additives having platelet shapes. A theoretical permeation model was implemented to assess influences on permeability of structure parameters such as platelet orientation and layer number. By localizing and orienting platelets within multilayers and neglectling crystallinity changes, model results indicate that such nanocomposites may have very low permeabilities. Permeability measurements and evaluations of crystallinity changes are subjects of future work.
Fracture of Polycarbonate in a Medical Device
The fractographic study of a polycarbonate component used in a prototyped medical device is reported of fracture mode, origin and mechanism, based on the examinations of the fracture surface and the interpretation of various fracture markings as observed using scanning electron microscopy (SEM). An explanative kinetics of fracture is given for describing the fracture process and various associated fracture events. The time and temperature effects on the fracture properties and fracture kinetics of polycarbonate are qualitatively considered to explain the causes of material brittleness. It has been noted that under complex long-term loading and varying time-temperature conditions, the fracture origins might be preexisting or newly created in a fracture event. Therefore, caution should be used in assigning the likely causes of material failure for design and manufacturing processes.
Modeling of the Effect of Intercalated Clays on the Tensile Properties of PMMA/Clay Nanocomposite Foams
A constitutive model for tensile behavior of PMMA/clay nanocomposite foams was developed in this paper. The model elucidates the effect of intercalated and agglomerated clays, where the elastic modulus of the nanocomposite foams is affected by the addition of clays to the polymer matrix. A viscoelastic model was adapted for the tensile behavior of the material. The detrimental effect by clay agglomeration was considered on the determination of the elastic modulus. For the verification of the constitutive model, PMMA/clay nanocomposite foams were manufactured by batch process method and their uniaxial tensile test results were compared with theoretical results. The proposed constitutive equation showed agreement with the tensile test results.
Photoelastic Measurement and Numerical Simulation of Residual Stresses
Injection Molded Polycarbonate Parts are extensively employed in optical, optoelectronic and electronic applications. But the molded residual stress can deteriorate the optical properties of the final product. Compared with PMMA, residual stress has more effects on PC injection-molded parts. In this research, the distributions of residual stress of the transparent molded polycarbonate parts have been inspected firstly under polarized light to understand effects of flow-induced and thermal-induced stresses and their interaction. Then based on optical experiment results of photoelasticity, the value of residual stresses was calculated. Flow-induced stress and thermal-induced residual stress of different molding conditions was investigated by numerical methods. A series of multicolored band or fringed pattern and simulation results showed the effect of non-uniform temperature distribution and fill pattern were the causes of residual stresses of thin PC parts.
Evaluation and Modeling of Scratch Resistance of Polymers
A new test methodology based on materials science and mechanics tools for evaluating scratch resistance of polymers has recently been developed and approved as a new ASTM standard. This new test method allows for simple, unambiguous quantitative evaluation and ranking of scratch resistance of polymeric materials. A low-cost scratch tester that can perform a constant load scratch test, an accelerated rate test, and a progressive load scratch test was built in our laboratory for the present study. Finite element methods (FEM) simulation has also been carried out to correlate between material parameters and the surface damage observed during scratch. An overview of the state of the art understanding of scratch behavior of polymers and coatings will be presented. Approaches for designing scratch resistant polymers and coatings will also be discussed.
Failure Analysis of Nitrile Radiant Heating Tubing
Radiant heating systems comprised of tubing installed beneath floors is widely used in the United States and Europe. Some radiant heating tubes are composites of multiple rubber compounds and textile reinforcement. In this paper, we present a detailed forensic examination of failed nitrile rubber radiant heating hose, based on techniques including field investigation, ion chromatography, high performance liquid chromatography, fractography, and gas permeability testing. Enduse testing of the nitrile tubing performed in the laboratory is described and correlated to field performance.
Evaluation of Weldline in Polycarbonate by Laser Raman Spectroscopy
Molecular orientation in weldline region in injection molded polycarbonate was investigated by laser-Raman spectroscopy. The observation was focused, in particular, on the area surrounding a V-notch on the surface of weldline. In the case of opposite flow weldline occurring in moldings produced with a two-gated dog bone cavity, the molecules just on the V-notch were slightly oriented along the notch, whereas those of the area within 1 mm from the V-notch were highly oriented parallel to the notch. Similar characteristics were found in an adjacent flow weldline occurring just behind an obstructive pin in a plaque mold. However, the degree of orientation varied along the weldline or flow direction. The degree of orientation was low near the obstacle and increased along the flow direction, resulting in high orientation in spite of complete disappearance of the V-notch at the area ca. 10 mm apart from the obstacle. In addition, further orientation was found in the position slightly apart from the disappeared V-notch. This suggested that the interface of the adjacent flow weldline behaved as a mold wall to generate shear flow during filling process.
Preparation and Characterization of HDPE Nanocomposite Micro Porous Film
A micro porous film with HDPE/MMT nanocomposite has been developed. The HDPE/MMT nanocomposites were prepared by melt blending with twin screw extruder with two step process. The master batches were manufactured by melt compounding with maleic anhydride grafted HDPE (HDPE-g-MAH) and MMT. The HPDE/MMT master batches were subsequently mixed with HDPE. Non-porous nanocomposite blown films were obtained by a single screw extruder attached film blowing and take-off unit. The micro porous film prepared by uniaxial stretching of non porous films. X-ray and TEM images showed the partially exfoliated nanocomposites which have the 5:1 – 20:1 ratios of HPDE-g-MAH and MMT. The thermal and mechanical properties of nanocomposites were enhanced by increasing the contents of MMT and in the presence of compatibilizer. The influences of annealing and stretching conditions were evaluated on micro porous film.
Computing Viscoelastic Flow of Polymer Melt in Injection Molding
Flow induced stresses, caused by viscoelastic flow of the polymer during the filling and post-filling stage, determines the anisotropy of mechanical, thermal and optical properties and influences the long term dimensional stability. A numerical method for solving viscoelastic fluid flow problem is presented in this study. The governing equations are in terms of generalized Hele-Shaw flow for incompressible, non-Newtonian, non-isothermal fluid and Maxwell model. The conventional Galerkin method is employed to discrete the constitutive equations expressed by pressure gradient, while the implicit scheme combined with up-wind method is used to discrete the energy equation. The typical example proves the viscoelastic constitutive relation is significantly better than the viscous.
Flow Charactristics of Rubber-Toughened Glass-Fiber Reinforced Nylon 66
This research deals with studying the effect of incorporating thermoplastic rubbers on the flow properties of virgin and Post-Industrial glass-fiber-reinforced nylon 66. Rubbers used in this study were Styrene-Ethylene- Butylene-Styrene and Ethylene-Propylene grafted with maleic anhydride. Flow properties of the composites were examined by the melt flow index and rotational viscometry. The melt flow index (MFI) data showed a drastic reduction in MFI when both rubbers were added to recycled and virgin glass-fiber-reinforced nylon 66. The highest reduction in MFI, which implies an increase in viscosity and molecular weight of the composites, was observed at higher rubber content. The measurements of the dynamic viscosity vs. shear rate showed an increase in viscosity with increasing rubber content at both glass fiber contents. The zero shear viscosity of the composites was found to generally deviate positively from the log additive rule.
Structural Development in Solution Casting Optical Polycarbonate Film
Optical polycarbonate (PC) film has been prepared by the solution casting film process using 1,3- dioxolane. The crystallization behavior of PC during the solidification process with removing 1,3-dioxolane was investigated to avoid the development of crystalline structure in optical PC film. The evaporation rate of PC/1,3-dioxolane solution affected the level of crystallinity in obtained PC film. It was found that the slow evaporation caused the forming of crystalline structure since it allows PC chain to have an enough time to crystallize. It was noticed from this study that PC undergoes solvent-induced crystallization by the solvent evaporation as well as by the absorption of organic solvent.
Model Laws and Scale-Up Rules for the Design of Extrusion Slit Dies
The design of extrusion slit dies is frequently based on knowledge and experience of the designers and toolmakers. One very simple, rapid and low-cost means of designing a slit die is the use of model laws and scaleup rules based on the similarity theory. This paper deals with an approach to develop scale-up rules which make it possible to scale-up or scale-down an existing die by means of simple equations, developed from the similarity theory. The cases observed are those of a constant gap height with a variable gap width and a variable gap width with a constant gap height. Allowance is also made for a change in material properties in order to achieve the greatest possible variability in the slit die design. Scaleup rules are compiled for die geometries and material properties described and derived by means of model laws and similarity theory. The scale-up rules are examined in practical experiments and in simulation calculations.
Numerical and Experimental Study of Dispersive Mixing Of Agglomerates
The degree of filler dispersion has a major influence on the physical properties of rubber compounds. Typical fillers, e.g. carbon black and silica, are difficult to disperse, particularly if they are fine and low structured. As a result, the quantity of undispersed fillers generally amounts for 1% to 10% of the compound. The elimination, or at least the reduction, of agglomerates will result in rubber parts (e.g. tires, seals, belts) with improved properties and higher reliability. Clearly, a better understanding of the physics of batch mixers would help improve their mixing performance. Due to the complexity of the real process, experiments on a representative device were held from which a model has been deduced. It appears to be a generalization of the law of Kao and Mason, but for high viscous matrices. The next step was to get a model available for statistically large number of pellets as can be found in any sample taken out of the mixer. A statistical approach is used where we define a model describing the evolution of mass density function of agglomerate sizes. Eventually, we implement this model within available numerical simulation tools to estimate dispersion in real mixers.
Experimental Investigations on the Plasticating Process in a Short Single Screw Extruder for Biopolymers
Compared to conventional single screw extruders, the ultra-short extruder has a completely different design. Therefore, the melting mechanism is also completely different. Experimental investigations in case of processing biopolymers like starch have shown first insight in the relations between process parameters, the place of melting and the energy conversion related to the melting process. Because the ultra-short extruder has no heating system, the plasticating process is only based on the conversion from drive power to friction. The variation of screw speed, feed rate and die resistance showed that mostly the screw is partly filled. This has an influence on the energy conversion and on melt temperature. Based on this knowledge, physical relationships between the parameters have been formulated in order to allow a further mathematical modelling.
Successful Defense Against Infringement
This personal narrative about involvement in a multimillion dollar patent infringement suit excites me even to this day. It actually involved work that I did in the1950s. The lawsuit took place in the 80s and involved over a year and half of preparation prior to trial in New Orleans. The infringement claim was based on an issued patent that involved a variation of a basic patent of mine which had been declared prior validity during a very active research era in which I introduced organotin/sulfur stabilization for polyvinyl chloride. At deposition time, the opposing attorney insisted that this case would not be settled out of court. At trial, the opposing attorney made a fool of himself and the case was decided in our favor. Because of continuing litigation elsewhere, the trial record was sealed and I was not allowed to testify in any similar case.
Rapid Cooling Crystallization in Thin Films of Linear Polyethylene
A rapid cooling technique has enabled us to study crystallization at very large supercoolings in the past, and is now well established for routine experiments on thin films. The results obtained for a series of polyethylenes, polypropylene, nylons and PET using the technique have enhanced current knowledge of the crystallization behavior of such materials at very high cooling rates. All the previous studies were carried out using thin films, 40 ?m or higher in thickness, and with embedded thermocouples. In the current study we will report the effects resulting from using films lower in thickness (~10?m) on the growth rate and morphology of linear polyethylene
Novel Metallocene Catalyst Phillips Loop-Slurry Based Polyethylene Resins for Extrusion Coating Applications
Significant advances in our abilities to synthesize novel polyethylene resins for extrusion coating applications are discussed. The new resins were largely equivalent to a conventional HP-LDPE resin in impact, tear, adhesion, sealing, extruder motor loads and pressures at comparable melt index values. Some resins closely approached the neck-in and drawdown of the HP-LDPE resin. These results are discussed in terms of the molecular and rheological properties of these novel resins compared to conventional HP-LDPE resins.
Observations and Insights into Some Unusual Rheological Behavior of Metallocene Catalyst Polyethylene Resins
The dynamic shear rheological behavior of polyethylene resins made using a single metallocene catalyst was measured and analyzed. We observed some unusual rheological behavior that, at first glance, was more reminiscent of the well-known behavior of highly filled systems. Specifically, the viscosity exhibited yield stresslike character with a sharp upturn in the low-frequency viscosity. The standard molecular weight distribution profile for these resins was generally unremarkable. The causes of this viscosity behavior were explored by further characterization of the molecular architecture and attributed to the presence of long chain branching selectively present in the highest molecular weight fractions of the polymers.
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