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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Separability Criteria for Entangled Polystyrene Solutions Using Flow Birefringence
Step shear strain experiments were performed using several entangled polystyrene (PS) solutions to investigate factorability requirements of the non-linear relaxation modulus, G(t,?) [? ?12(t,?)/?]. A phase modulated flow birefringence apparatus was used to measure optical equivalents of shear stress (n12) and first normal stress difference (n11-n22) in a plane-Couette shear flow geometry. For all polymers studied, a separability time ?k was identified beyond which the optical equivalent of G(t,?) [B(t,?) ? n12/? ? G(t,?)×C] could be factorized into separate strain and time dependent functions. In every case, ?k exceeded longest Rouse relaxation time ?R and found to be of the order of terminal relaxation time ?d0. These findings could help explain previous experimental observations of delayed factorability and non-factorable relaxation moduli in well entangled polymer solutions and melts.
Simulating the Cohesive Properties of Ultem and Related Molecules
The cohesive properties of many engineering plastics are difficult to determine experimentally, as the polymers are frequently insoluble, have high Tg's, and are sometimes poorly characterized. Molecular modeling can provide useful information of higher quality than might be obtained by other methods for these difficult polymers. A series of simulations on Ultem® and related molecules have been performed to evaluate the cohesive energy density of the polymer and determine interfacial interactions with small molecules. These methods yield a value near 22.0(MPa)½ for the solubility parameter of the polymer, and it is shown that benzyl alcohol has the most favorable interactions.
Adhesion of Polyethylene to Polypropylene in Multi-Layer Films
A distinct difference was found between metallocene and Ziegler-Natta catalyzed linear low density ethylene copolymers (LLDPE) in the coextrusion with polypropylene (PP). A layer of amorphous material was hypothesized to form between PP/Ziegler-Natta LLDPE interface and not in the PP/metallocene LLDPE system. The presence of a weak amorphous interfacial layer was supported by the results of the T-peel test where the metallocene LLDPE system showed significantly higher level of adhesion between PP and LLDPE than the Ziegler-Natta LLDPE systems.
Graphic Film Inserts for Molding
There are many methods to decorate plastic films. As an overview, I will highlight most of the methods used to decorate plastics in post mold operations and in mold operations.
Film Finishing Part II: Use of Multi-Layer Films in Finishing Technologies
Part I of this two part series addresses the background of film finishing, its status and the strategic potential for the technology. Part II is concerned with the materials and processes used in multilayer film production. Film application methods are reviewed from an overview perspective.
Micro-Photometric Inline Particle Monitoring in Flowing Melt (TSE)
A unique particle sensing system will be presented based on a special micro-photometric principle. The final objective is to achieve inline / realtime informations about developing and final stage of particle dimensions in flowing polymer melts. The performance of the new sensor prototytype PMP 690 adapted to a twin screw extruder (TSE, ZSK40-type) will be demonstrated by extrusion mixing of different model glass bead types (particle diameters and volume concentrations) into polystyrene melt.
Modeling the Melting Process of Polymer Pellets Caused by Friction
The melting of polymer caused by friction before the solid plug is formed is an important phenomenon in the plastic injection process. To analyze the melting process caused by solid particles sliding against the bellow, an analytical method that can simulate behavior of each particle during the calculation should be used. Particle element numerical method is hence adopted in the analysis for this research to take into consideration the behavior of each particle. In the review of literatures in this area, no publication has reported success in the analysis of the transient close-contact melting process caused by friction. In this paper an analytical expression for the transient melting process is derived by assuming friction against flight and screw as friction against adiabatic walls.
Modelling of the Effect of Slip in Plug-Assisted Thermoforming
In plug-assisted thermoforming, the interaction between the sheet and the plug strongly affects the final part thickness distribution due to sheet cooling and slippage on the plug surface. The type of plug material and surface finish has to be carefully selected. The amount of slip on the plug surface depends on the rheology of the polymer sheet and on the friction coefficient. Both properties are temperature dependent. In this work a non-isothermal friction coefficient model is evaluated for its potential in predicting the amount of slip in plug-assisted thermoforming. The model has been implemented in a finite element analysis software for predicting the consecutive steps of the thermoforming process. The model has been applied to simulate industrial scale plug-assisted thermoforming and the predictions are compared to experimental measurements.
Polyurethane Coatings Based on Soybean Oil Prepolymers and Crosslinkers
Four series of coatings were prepared by using a soybean oil based isocyanate prepolymer and two types of the soybean oil based polyols as the crosslinkers. Water (humidity from the air ) was also used as a co-crosslinker. The isocyanate prepolymer and the polyols were prepared according to the original, proprietary methods. Varying the hydroxyl number of the polyol and polyol/ water ratio in the crosslinker varied the structure and properties of the coatings. The coatings were tested for hardness, elasticity (bending test), scratch resistance and adhesion. DSC, TGA, TMA, tensile strength and swelling were used to assess the glass transition and crosslinking density of the films.
Generation of Thermotropic Liquid Crystalline Polymer/Thermoplastic Polymer Strands for Producing Wholly Thermoplastic Composite Materials
Thermotropic liquid crystalline polymer (TLCP) reinforced thermoplastic polymer (TP) strands were spun and used in injection molding to form wholly thermoplastic composite materials. While keeping the strand size suitable for injection molding, effort was made to increase the orientation and aspect ratio of the TLCP fibril that would remain in the final product as reinforcement. The pelletized strand can be injection molded without disturbing the TLCP reinforcing fibrils. The samples have similar mechanical properties, lower density and smoother surfaces compared with glass fiber reinforced samples.
Rheology beyond One Million Reciprocal Seconds
In the wire and cable industry the speed of the insulated copper wire through the die is very fast. In 1963 a 24 gage wire was coated with plastic with a clearance in the die of only 5 mils (1 mm = 40 mils, i.e., 5 mils = 0.125 mm) at a speed that exceeded 2500 feet/min (almost 1 kilometer/minute). The shear rate calculates to be in excess of one million reciprocal seconds (actually this is 4 x 106 sec-1). Drastic changes were discovered in the molecular structure of the plastic. Shearing the polymer chain causes changes in the molecular structure that can be advantageous or severely detrimental. These running conditions and the effect on the PVC is the concern of this paper.
Re-Inventing the Wheel: Breaking New Ground with Rotary Shuttle Technology
Long-stroke shuttle machines have developed a well-defined role in the extrusion blow molding of calibrated neck bottles. However, these machines have limitations due to factors such as the long axial length of the stroke and the need for large multiples of tooling, knives, dies, punches and In-Mold Labeling (IML) tooling sets per the number of mold sets. Many of these limitations have been overcome through the incorporation of an indexing rotary motion. The end result is a technologically advanced, small footprint machine that can produce IML bottles with very little cycle time penalty. Further, the multi-layer containers are de-flashed before exiting the machine with positive bottle transfer between stations with a true single-point product discharge. All of this is accomplished using fewer die pins, bushing sets, cut-off knives, trim dies, punches, and IML deployment heads than typically required. This paper discusses the technical hurdles that were overcome to re-invent" the shuttle machine and open up new possibilities in extrusion blow molding."
Do You Want Some Salsa with Those Chips?
In the world of coloring plastics, there has been an apparent decline in the understanding and application of color technology. This is particularly noticeable the farther down and away from the source of the colored product you go. Retirements, downsizing, consolidations and other factors have contributed this knowledge base loss. This paper looks at this issue and what we can do to build it back up.
How Social and Cultural Influences Affect Automotive Design, Styling and Decoration
A discussion of how social and cultural influences in fashion, architecture, interior and product design affect automotive design, styling and decoration, and how these influences are brought to reality.
A Robust Ultrasonic Mold Condition Monitor for Injection Molding
An ultrasonic transducer was installed on an injection mold such that the sound pulse would strike the front surface of the mold cavity and reflect back to the transducer. Changes in the intensity of reflected echoes are shown to be sensitive to the presence of polymer in the mold. By monitoring this changing reflected echo a signal is produced that is sensitive to conditions in the mold during processing. The primary advantage of the transducer is that it can be mounted on the external surface of many molds, allowing an installation that requires no machining of the mold.
Effects of Chain Extension/Branching on the Viscoelastic Behavior of Styrene-Maleic Anhydride/Polyol Blends
Styrene Maleic Anhydride (SMAH) / Polytetramethylene Ether Glycol (PTMEG) blends were produced in a batch mixer in the presence or absence of hydrated zinc acetate catalyst. The oscillatory shear properties in the melt state and the Fourier Transform Infrared Spectra (FTIR) of the blends were studied. The SMAH/PTMEG/zinc acetate blend had higher storage modulus, G', loss modulus, G and complex viscosity ?* than the blend without the catalyst. The distribution of relaxation times was calculated by using the oscillatory shear data and a generalized Maxwell Model. In comparison to pure SMAH for all the blends higher relaxation strengths at longer relaxation times were obtained due to chain extension and branching. The FTIR spectra of the SMAH/PTMEG blend indicated ester formation confirming the existence of chain extension / branching reactions in batch mixing."
The Selection of Mould Design Variables in Direct Stereolithography Injection Mould Tooling
Models produced by rapid prototyping (RP) allow the validation of a parts design with respect to its geometry. Beyond this, the rapid prototyping technique Stereolithography (SL); when used to manufacture moulding cavities, has shown itself to be capable of rapidly and economically producing low volumes of plastic injection moulded parts prior to commitment to hard tooling. These parts are more complete prototypes, they imitate parts that would be produced by a hard tooling manner with respect to their material, geometry and production process. A major drawback of the SL injection moulding process is that the tools are susceptible to producing only a small number of parts before failure. SL tools may break under the force exerted by part ejection when the friction between a moulding and a core is greater than the tensile strength of the core resulting in tensile failure. Very few justified recommendations exist concerning the choice of mould design variables that can lower the part ejection force experienced and reduce the risk of SL tool failure. This research investigates the ejection forces resulting from injection moulding polypropylene (PP), acrylonitrile-butadiene-styrene (ABS) and polyamide 66 (PA66) parts from SL tools which are identical in all respects except for their build layer thickness (a process variable when generating the SL tooling cavities) and incorporated draft angles (a tooling design variable). This work attempts to identify appropriate evidence for recommendations with respect to these variables and SL injection moulding. The results show that linear adjustment of draft angle results in a fairly minor linear change of part ejection force according to the moulding material. A linear adjustment of the build layer thickness results in a greater change in part ejection force as a more non-linear relationship. In both cases greater ejection forces were experienced by PA66, then ABS and then PP parts, respectively. The results also show that the s
Modeling of Fluted Mixing Elements
3D simulation helps to have a better understanding of material behavior in complicated flow geometries such as extrusion dies or mixing elements where a 2D simplification fails. In our study, we will simulate the material behavior in a fluted mixing element. The fluted mixing element is one of many used mixing elements. Its specific geometry influences a good or bad mixing performance as well as local heat generation because of the shear dissipation. The study is focused on parametrical study of the influence of mixing element dimensions on the material behavior (generated pressure drop, mixing quality etc.). It is also focused on the determination where and under which conditions the heat generation is occurring, what is the related temperature rise and how this high heating can be prevented.
Blends of Various Proteins with Poly(Hydroxy Ester Ether)
Blends of poly (hydroxy ester ether) (PHEE), a recently developed bisphenol A ether-based synthetic biodegradable thermoplastic polymer, with a soybean protein isolate and two hydrolyzed wheat glutens were studied. Blends of the proteins with PHEE were produced from 20-70% by weight of protein content. The Young's moduli of the protein/PHEE blends falls in the range of 0.8 - 1.5 GPa with the tensile strengths ranging from 10-30 MPa. Fracture strengths of the blends ranged from 9-2 MPa-m1/2 depending on the amount of protein added. Morphological analysis indicated acceptable adhesion between the protein and PHEE phases in the blends. In general, as the protein content was increased the materials lost ductility and failed in a brittle manner; however, the mechanical properties of several compositions were comparable to current commercial thermoplastics such as polystyrene.
Developing a System to Activate a Post-Molding Blowing Agent in the Application Field
This experiment creates a process which allows injection molded parts to be foamed during assembly applications, resulting in optimal airtight sealing properties at the plastic interface.
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