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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Stretch Blow Molding of PET Bottle: Simulation of Blowing Process and Prediction of Bottle Propeties
This paper presents a technique for describing more accurately mechanical behaviors of a PET stretch blow molded bottle by using distributions of modulus and thickness over the bottle surface. The values of modulus and thickness at each point of surface of the bottle were predicted from deformation histories of the material during the blowing process, which were obtained in numerical simulation of the blowing process. It also needed experimental measurements and estimation of mechanical properties of a stretched material up to stretch conditions in the blowing process in order to find out dependency of the properties on stretch conditions.
Evaluating the Use of Aluminum Inserts on SL Puzzle Molds for Injection Molding of Complex Parts: A Case Study
Stereolithography is a rapid prototyping technique that is also capable to producing rapid molds with high accuracy in a short time. The mold's life expectancy is strongly dependent on the part geometry. This factor could induce weak regions in the mold that are more susceptible to collapse, like sharp corners and thin features. An alternative that could be used is to conceive the mold as a puzzle where slides are manually placed inside a main slot and drawn during the ejection. This work describes a comparison between two puzzle molds that had been made with and without aluminum inserts.
Determining, Understanding & Controlling the Morphology of Injection Moulded Parts Produced in Stereolithography Moulds
The direct use of moulds produced by stereolithography (SL) provides a rapid tooling technique, which allows low volume production by plastic injection moulding. The process’ greatest advantage is that it provides parts that are the same as those that would be produced by the conventional hard tooling in a fraction of the time and cost. However, work by the author demonstrates that the parts possess different characteristics to those produced by conventional tooling methods. These revelations defy the greatest advantages of the SL injection moulding tooling process - the moulded parts do not replicate parts that would be produced by conventional hard tooling. This work investigates the mechanisms in SL tooling that induce these different part properties and describes different approaches to modifying the process which allow the moulded parts to demonstrate characteristics closer to those produced by conventional means. The work also indicates control methods that may be unique to SL tooling.
Mold Conceptual Design Based on Fuzzy Logic
Mold conceptual design is the most important phase of mold design. The decisions made during this phase are of high level and have a direct influence on performance of the mold and development costs. The main task for mold conceptual design is the in-principle determination of each mold element type (design scheme). Because of its non-algorithmic nature, technologies and methodologies such as knowledge-based system (KBS), case-based reasoning (CBR) has been used to do the work. In this paper, a novel approach was proposed to map mold element design requirements onto the corresponding design scheme by using fuzzy logic. The proposed methodology follows three steps: (1) Design requirements for mold element is extracted and generalized. (2) Possible design schemes are presented. (3) The fuzzy mapping relationship between mold element design requirements and design scheme is established based on fuzzy composition and fuzzy relation transition matrices that are assigned by domain experts. A gate type selection example was presented to illustrate the feasibility of the proposed methodology.
Keeping It Straight: The Five Sided Box
Every molder that has tried to maintain squareness in the corners of a plastic part has come to appreciate the unique cooling problems inherent to the five sided box. It has long been understood that corners where two sidewalls meet the top or bottom of a product provide substantially increased heat load to the core of the mold. This increased heat load yields differential cooling, thus corners tend to develop stress, causing the sidewall to warp in. This investigation studied the effect of various core materials to and their effect on the warpage of the sidewalls of a five-sided box. The relative cycle time required to achieve maximum squareness for a given core material was also investigated.
Ultrasonic Microforging for Production of Microscale Parts with Nanoscale Features
An ultrasonic horn is used to investigate a manufacturing technique to produce microscale polymeric parts using continuous wave ultrasound. This technique of microforging has a potential to produce microscale parts in production quantities. It should be capable of replicating nanoscale features on the microscale part. Potential advantages of microforging include speed of production and easy handling of the parts compared to microinjection molding techniques.
Radiation Processing of Polymers: The Current Status and Prospects for the Future
Radiation processing has been used for almost 50 years to improve both bulk and surface properties of polymer resins and formed components. This session will examine several specific applications of commercial radiation processing in depth. This presentation will provide background for this session.
Novel Resins through the Pre-Irradiation Modification of Polyethylenes
The presentation describes the development of a new family of novel polymers made through the ionizing radiation modification of polyethylenes prior to the conversion thereof into end products.
Polymer Treatment Techniques with Energetic Electrons
Fluidized bed handling of polymer powders and granules has been evaluated using electron energies in the 0.25-1.0 Mev. range. Performance data are presented for two pilot systems used in the development of this process typically operating in the product velocity range of 300-2000 meters per minute.The application of electron beam processors to the disinfection and sterilization of polymer containers provides an efficient route to the high speeds offered by modern filling equipment. Some results for the post treatment extraction studies in high density polyethylene and polyester bottles are presented.""
Approach for a Mechanical Design of Plastics Injection Molds by Means of FEA
At the design phase the injection mold maker should endeavor to ensure a maximum reliability of the mold to avoid additional costs for subsequent modifications. It is astonishing that today the mechanical design of injection moulds is predominantly done in a conventional and crude way. Finite element analysis has the potential to improve that practice. Hence an approach has been developed to couple iteratively the structural analysis of the injection mold with the filling simulation of the plastics part. That approach for an automatically coupled simulation has resulted in the first prototype version and has shown good results. This paper seeks to present the theoretical and experimental data for review.
Gelation of Hydroxy Propyl Cellulose with Sodium Dodecyl Sulfate: Temperature, Frequency and HPC Concentration Effects
The gelation of hydroxypropyl cellulose (HPC) solutions with an anionic surfactant was investigated. First the influence of HPC concentration (1-8%) on viscosity of water was examined. This indicated a change from Newtonian to Non-Newtonian and the development of a biphasic system. A 2 and 8% solution mixed with an anionic surfactant, sodium dodecylsulfate (SDS), was then investigated. At concentrations below the critical micelle concentration of the SDS, a peak in viscosity-concentration was observed. The concentration corresponding to the peak was found to be frequency dependent. The introduction of the SDS into HPC eliminated the biphasic structure of HPC.
Microstructure Evolution during Flow Startup of a Thermotropic Liquid Crystalline Copolyester
The microstructure evolution and corresponding transient rheological behavior of a thermotropic liquid crystalline polymer (TLCP), Vectran V400P, is reported. The structure was characterized by using a Linkam CSS- 450 shearing/hot-stage mounting on a polarized microscope. Rheological characterization in the transient mode revealed that the transient shear stress exhibited two overshoots. We believe that the domain and defect rearrangement leads to the first shear stress overshoot. The relative magnitude of the second shear stress overshoot increases with increasing shear rate and with decreasing temperature.
Small-Scale Studies of Flowing Polymer Melts within Recirculation Flowcells
Two small scale (30g and 200g full charge) recirculation flow cells have been designed, manufactured and commissioned for the study of newly synthesised novel polymers. Full field stress and velocity measurements for a number of polymer melts through two abrupt contraction dies have been made utilising stress birefringence and particle tracking velocimetry techniques. These results have been compared with those through geometrically identical contractions mounted in flow cells on 38mm and 60mm extruders in order to quantify the effects of scale up. Complimentary small angle neutron scattering (SANS) and X-ray scattering (SAXS) studies on molecular configuration and shear induced crystallisation show the usefulness of these flow cells and brief results from these experiments will be presented.
Effect of Low Temperature Shift Factor Modeling on Predicted Part Quality
The effect of low temperature modeling of the time-temperature shift factor on the prediction of residual stress and warpage of injection-compression molded compact discs is studied for an optical grade polycarbonate. Predicted residual stress and warpage with WLF and Arrhenius shift factors truncated at different temperatures indicate that the truncation temperature has a significant effect on the predicted part qualities. A double domain approach is employed to fit the shift factor with WLF function above Tg and an asymptotic function below Tg, and the simulation results are compared with the experimental observations. The comparison shows that the double domain shift factor yields good model fit and part quality prediction of injection-compression molded compact discs.
Mechanical Hole Burning Spectroscopy: A Comparison of Two Scenarios
A mechanical hole-burning (MSHB) scheme was constructed to compare the analogous observations to those from dielectric non-resonant spectral hole burning (NSHB) for glass-forming liquids near their glass transitions. We used the framework of the BKZ and Bernstein-Shokooh nonlinear viscoelastic constitutive equations to examine the modified responses in a way that does not invoke an explicit heterogeneous or homogeneous nature for the relaxation response. From the BKZ model only partial hole-burning features are observed in the modified shear modulus. The Bernstein- Shokooh model used to calculate the modified compliance shows no evidence at all of a hole-burning event. These results suggest that in addition to showing potential as a probe of dynamic heterogeneity, MSHB may also a prove to be a sensitive test for the validity of nonlinear constitutive laws.
Electron-Beam Cross-Linking and Melting of UHMWPE for Hip and Knee Replacements
Wear and damage of polyethylene are the leading causes of in vivo failure of total hip and total knee arthroplasty. Increasing the resistance of polyethylene to wear and damage has been possible by radiation crosslinking and subsequent melting. Crosslinking improves the wear resistance of this polymer, while post-irradiation melting improves the long term oxidative stability, which is the primary precursor to polyethylene damage in vivo.
Continuous Process for Recycling of Polyurethane Foam
A continuous process for decrosslinking high resiliency polyurethane foam in an extruder with ultrasonic devices was developed. Rheological, structural and NMR relaxation and diffusion characterizations of decrosslinked foam were performed. The decrosslinked foam was blended with the virgin polyurethane rubber (PUR) and cured and the blend properties were investigated.
Study of the Processability of Post-Consumer and Post-Industrial Recycled High-Impact Polystyrene
In this work, the process of recycling high-impact polystyrene, both post-consumer and post-industrial, was studied. Blends of recycled/virgin materials were made and their MFI, mechanical properties and processability (thermoforming) were evaluated. Few differences in the behavior of the materials were found and their use as thermoformed packaging was ascertained.
The Effect of Process Aids on the Rheological Properties of Rigid PVC Melt
This work presents an overview on the role of process aids on the rheological properties of rigid PVC. A new rheological approach is introduced to allow a better assessment of the role of these additives. This system comprises a combination of a Couette-type cell and a capillary rheometer. The former allows a good control of the thermo-mechanical history of the compound prior to injection into the capillary barrel where a viscosity measurement is performed. The results showed that rigid PVC undergoes a fusion and gelation processes during the early stages of processing. In this step, the particles are agglomerated under the influence of heat and mostly shear. There seems to be an optimal morphological state where the best mechanical properties are obtained. Additional work showed that the addition of high molecular weight impact modifiers which also act as “binders” in the matrix promote the fusion and gelation of PVC. The results are supported by impact testing and microscopy.
Practical Application of a Portable Rheometer
A portable rheometer has been developed for characterizing plastic melts for different measurement purposes. The rheometer is intended particularly for use with rigid PVC processing, but can be used for other materials too. Measurements showing the accuracy of the instrument and its reproducibility are discussed. Comparisons are made between measurements on a conventional laboratory capillary rheometer and ones on the rheometer developed, using polypropylene. The practical application of the rheometer is also shown. This is used in combination with a twin-screw extrusion line to evaluate the rheological data of different pressure pipe and profile PVC formulations in order to develop new die geometries.
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