SPE Library
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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Conference Proceedings
Numerical Simulation of Expandable Polystyrene Microsphere Expansion
In this work, a continuum mechanics model is developed to simulate the expansion process of expandable polystyrene (EPS) microspheres both in air and in partially cured epoxy resin. The model is formulated to take into account various kinetic and dynamic parameters involved in gas bubble nucleation and growth in EPS, including nucleation rate, bubble number per EPS microsphere, rate of bubble radius growth, and bubble pressure drop. For expansion in air, the model is able to quantitatively predict the actual experimental growth rate of EPS microspheres. For expansion in partially cured epoxy resin, the model prediction shows that the retardation effects on EPS expansion only becomes significant in the late stage of the expansion process.
Predicting Physical and Optical Properties of Co-Extruded Blown Films Using Design of Experiment Based Model
Co-extrusion enables the combination of attributes of different polymeric resins to create films having unique and tailor-made properties. Besides the resins used in the film structure, the properties of co-extruded films depend upon factors such as film gauge, layer ratios, amount of blend component used in the layers. We developed an easy to use model with MS Excel interface to predict physical and optical properties of three layer co-extruded films. The model uses Design of Experiments (DoE) approach, and the regression coefficients obtained from each of the responses are used to model the film properties. The model enables designing film structures to optimize film properties and material cost.
Compatibilizing and Toughening of an Immiscible Polyphenylene Blend via Reactive Mixing
A reactive blending of two immiscible thermoplastic polyarylene derivatives namely, poly (p-phenylene sulfide) [PPS] and poly (phenyl sulfone) [PPSU] was accomplished in presence of compatibilizing agents.
The blend of a semi-crystalline polymer, PPS, and an amorphous polymer, PPSU, can be turned into entirely amorphous material with finely dispersed discrete domains in the matrix phase. The cured composite obtained by further heat treatment of melt-mixed PPS/PPSU blend exhibits a single glass transition temperature (Tg). The cured polymer blend thus developed extends the application potential as downhole backup ring and sealing application over the application range of the component polymers (ò400F).
Creep Behavior of Polymer Blends and Long Term Prediction
Creep behavior of polymers and polymer composites as structure materials used in load bearing applications is of considerable interest to the design engineers. This paper presents short-term creep behaviors of three polymer blend systems: unreinforced compatibilized blend, glass fiber reinforced blend, and miscible blend. The long-term creep behaviors of these blends were predicted based on the time-temperature superposition principle. The applications of this principle to the polymer blends that contain more than one phases were discussed. The benefits of creep behavior to plastic parts designers, builders, and operators were revealed.
Layer Integrity in Polyethylene Based Multilayer Film/Foams and Their Properties
Previous research has shown that multilayer film/foam structures can be developed by co-extrusion technology. This paper discusses the strategy to achieve good layer integrity as well as high deformability in polyethylene based film/foam systems. In order to improve the layer stability during processing, a viscosity contrast between film and foam layer is maintained. Three different LDPE grades having different melt flow indices have been used. Film/Foam systems with up to 32 layers have been produced. High viscosity film layer and low viscosity foam layer in each film/foam system contributed to good layer integrity even with high foam content. Moreover, each film/foam system exhibits high failure strain in tensile mode. In addition, increasing layer number also improved the tensile modulus and strength of each film/foam system.
Effect of Interphase Modulation and Orientation on Dielectric Properties of PET/P(VDF-HFP) Multilayer Films
High energy density dielectric film capacitors require polymer films having advanced dielectric and breakdown properties. Using nanolayer coextrusion technique, multilayer film capacitors were produced with poly(ethylene terephtahlate) (PET) and poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)]. Dielectric properties of the polymer multilayer films were improved by adding poly(methyl methacrylate) (PMMA) as tie layers and biaxial orientation. Layer uniformity of PET/PMMA/P(VDF-HFP) films was confirmed using AFM and a diffused interphase was found with PMMA as a tie layer. From biaxial orientation, the c-axes in P(VDF-HFP) crystals oriented parallel to the layers. With interphase modulation and biaxial orientation, PET/P(VDF-HFP) films exhibited a 33% enhancement in breakdown strength and 150% improvement on energy density
Injection Overmolding Performance of Thermoplastic Polyester Elastomers (TPC-ET)
This paper describes overmolding processability and performance of wide range of polyester elastomers with varying hardness over commercially important hard substrates. Such combinations are judiciously selected to achieve required performance for excellent grips, aesthetics or improve impact strength. While the soft components vary from 60 Shore A to 55 Shore D; hard components are selected based upon the relative polarity and cover a broad variety of engineering thermoplastics used for structural applications. New low hardness (60 Shore A to 80 Shore A) thermoplastic copolyester elastomers (TPE-E) are also tailored to achieve good adhesion on difficult to bond substrates such as polyacetals. These elastomers deliver excellent mechanical properties, such as low-temperature flexibility, cold temperature impact strength, tensile elongation greater than 700%, and work well at a broad range of temperature and humidity conditions. These recyclable elastomers can be processed via injection molding, blow molding and extrusion.
Understanding Blown Polyethylene Film Dart Strength Variability
The impact resistance of film is a critical property for many applications. The Falling Dart (or Dart Drop Impact, DDI) test is an industry standard for gauging the strength of films subjected to a relatively high speed impact event. The test is based on a ?staircase? methodology and requires a minimum of 20 drops to obtain a single strength value. An alternative test, the Spencer Dart Impact test, uses a pendulum mounted impactor and measures the energy required to break a stationary film. This has an advantage over the Falling Dart test in that each impact will give a strength allowing for better statistics. We examine here the variability of the dart strength within a blown film and how ?robust? the dart test is in determining the true strength of the film using experimental and modeling data.
Triple Shape Memory Materials Fabricated by Forced Assembly Multilayer Film Coextrusion Technology
Forced assembly multilayer coextrusion through a series of layer multiplying elements has enabled the production of films containing tens to thousands of alternating continuous layers with individual layer thicknesses down to the nanoscale. A multilayered triple shape memory material, polyurethane (PU)/ethylene vinyl acetate (EVA)/polyvinyl acetate (PVAc), with 257 alternate micro- or nano-scale continuous layers, was investigated. The triple shape memory behavior of PU/EVA/PVAc multilayered film was studied by thermomechanical cyclic test, and its triple shape memory mechanism was also discussed.
The Impact of Engineering Plastics on the Advancement of Solar Energy in the United States
The United States photovoltaic (PV) demand has experienced exponential growth in the residential, commercial and utility segments during the past several years and this growth is expected to continue. The growth of this market is due to the drastic reduction in the cost ($/watt) of solar energy systems initiated through the Department of Energy (DOE) Sunshot program which aims to reduce the cost by over 70% by the year 2020.1 In order to achieve this aggressive goal, alternative materials such as engineering plastics are being considered more than ever before. This paper discusses the impact of engineering plastics on reducing the overall cost while increasing the performance of solar installations in the United States. This paper focuses primarily on the commercial flat rooftop segment of solar due to this segment?s traditionally strong growth and high potential for metal to plastic product conversion.
Using Molecular Stress Function Theory to Evaluate Strain Hardening of Polyethylene
Strain Hardening of polyethylene in uniaxial extensional flow is evaluated with a focus on its strain rate dependency. The stress growth function data of LDPE and HDPE by a rheometer with dual drum fixture was evaluated with the Molecular Stress Function (MSF) Theory. The model provides evidence that the MSF fit on the data at the lowest available strain rate may be used to obtain reasonable semi-quantitative characterization of the long-chain branching content of LDPE. The rate dependent strain hardening behavior of the LDPE and HDPE samples, on the other hand, is well characterized with the maximum Trouton ratio (Tr) predicted by MSF. All three resins studied show a decreasing Tr with increasing strain rate. The rate dependence is strong when Weissenberg number Wi ó1.
A Case for Round Energy Director: Utilizing Advanced Control Capabilities of Servo-Driven Ultrasonic Welders in Evaluating Round Energy Director Performance
Ultrasonic welding of thermoplastics is widely used in many industries to fuse two parts together in a very short time with no additional consumables. The development of the Dukane?s iQ series Servo-Driven Ultrasonic Welder with patented Melt-Match? technology introduces unprecedented levels of control, which allow to overcome less than optimal weld joint designs, material compositions and processes, that have long been challenging to pneumatically driven welding presses. This study further investigates the capabilities of the servo-driven welder and focuses on experiments evaluating the feasibility of using round energy director (ED) designs for the ultrasonic welding process.
Sterilization Effects on Hard-Soft Combined Polymers for Medical Application
Polymeric hard-soft combinations manufactured by multi-component-injection molding are a suitable way to combine strength properties of a hard thermoplastic component with an elastomer for damping, sealing or haptic functionalities. The use of multi-component injection molding has been transferred to medical applications, mostly applied for sterile products. Consequently, it has to be ascertained that necessary sterilization processes do not affect the adhesion between hard and soft component during the life cycle of the plastic part. So far, there is a lack of sufficient studies on sterilization effects within hard-soft combinations.
For this reason, the adhesion strength of different polymeric hard-soft combinations after sterilization treatment was analyzed in this study. The tested material combinations are different thermoplastic elastomers (TPE) on thermoplastic substrates. Moreover, silicone rubber was combined with thermoplastic substrates after atmospheric pressure plasma treatment. Hot steam sterilization (20 min., 121øC) and gamma irradiation (50 kGy) were applied on the specimens with varied intensities. To quantify the influence of sterilization treatments, adhesion strength was analyzed by 90ø-peel testing. SEM images of the peeled off surfaces were compared for qualitative analysis of the bond strength. Hot steam sterilization was particularly critical to polar materials as e.g. polycarbonate (PC), resulting in reduced peel force, as well as to heat sensitive material combinations. Gamma irradiation can be applied to nearly all tested polymers, for some thermoplastic ? silicone rubber combinations the peel force can even be enhanced due to post-curing reactions. Beneath the influence of sterilization on adhesion, other effects as yellowing of e.g. PC and TPU or changes in mechanical characteristics have to be respected.
Rheological Characterization of Highly Filled Composite Systems for Injection Molding Applications
The focus of this study is to characterize the rheological properties of boron nitride (BN) composites. A series of boron nitride composites with varying filler loading level were prepared using two different forms of BN fillers blended with polystyrene (PS). The rheological properties of these composites were characterized using a parallel plate rheometer and a capillary rheology. The structure and thermal conductivity of these composites were also characterized. These data were used to identify structure-property relationships for PS/BN composites.
Heat Transfer Simulation for a Continuous Annealing Process of Plastic Sheets
The continuous annealing process in conjunction with an extrusion casting line is of vital importance to reduce the shrinkage level of plastic sheets while maintaining economic competitive advantage. Therefore, it is crucial to accurately predict the temperature profile of plastic sheets during the annealing process to facilitate process design and operational control. In this paper, a heat-transfer model was developed to predict and optimize the continuous annealing process. Through mathematical modeling of the infrared heating process using a finite-difference analysis (FDA) program coded with FORTRAN language, we successfully mapped the temperature profile of plastic sheets. The numerical simulation results were validated and consistent with experimental data.
Effect of Rheology on the Morphology of Coextruded Microcapillary Films
This paper reports, for the first time, the successful implementation of microcapillary coextrusion technology with an emphasis on the fundamental understanding of the effect of rheological properties of polymers in both film matrix and microcapillaries on the morphology of coextruded microcapillary films. Four different polymer pairs were judiciously selected for coextruded microcapillary films, indicating that the microcapillary shape may be circular, oval, or even rectangular depending on the viscoelastic properties of the respective polymer pair as well as the processing conditions. The area percentage of microcapillaries in the film cross-section was dependent on the screw speed (i.e., extrusion rate) of the extruder. The average film thickness decreased with increasing line speeds, while the aspect ratio of microcapillary dimension held the reverse trend.
Numerical Simulation and Experimentation of Water-Assisted Co-Injection Molding of a Non-Circular Tube
Water-assisted co-injection molding (WACIM) is a complex, innovative injection molding process. A three-dimensional model for WACIM was setup and a turbulence model was adopted to deal with the turbulent flow of the water. A free interface of the skin?inner melt and the inner melt?water were tracked by the volume of fluid (VOF) method. Numerical simulations for the filling stage of WACIM parts with four types of cross-sections were carried out using the computational fluid dynamics (CFD) method. Experiments were conducted to verify the simulation results. The results of the experiments were in agreement with those of the simulations. The shape of the cavity cross-section had an obvious effect on the penetration section of the inner melt, while the shape of the water penetration ended up being round. The penetration area of the water increased in the flow direction, and the residual thicknesses of the inner melt downstream was thinner than the melt upstream.
Precise Injection Molding of Thermoplastics Elastomers -Evaluation of Surface Replication and Metal Adhesion-
New thermoplastic elastomer (TPE)s with different polymer content and additive were injection-molded onto line-and-space micro pattern and sand-blasted aluminum plates. The thermal shrinkage and micro surface replication of molded elastomers were revealed after injection molding. These properties of elastomers were dependent on the composition of polymer and additive. Moreover, the sand-blasted aluminum substrate was joined with the molten elastomer as the elastomers were developed to precise seal parts for electronic devices. The joining strength of the aluminum/elastomer interface was sufficiently strong as the elastomers themselves were fractured while the interface was held when the joined part was stretched.
A Walk around the Color Sphere: Effect of Titanium Dioxide Particle Size Distribution on Color of Plastics
?Black? and ?White? pigments are often referred to as colorants because they can influence the color properties of finished products in the plastics industry. One of the most common ?white? pigments used in the plastic industry is rutile titanium dioxide. This review provides an example of how various types of titanium dioxide materials can impact the overall color of plastics. Three different titanium dioxide (TiO2) grades were compounded into a soft PVC containing with a fixed amount of carbon black and the resulting CIE L*a*b* tri-stimulus values were measured. The primary difference amongst the titanium dioxide samples was their median particle diameter. Each titanium dioxide material resulted in a unique color space, As the amount of each pigment was increased in the soft PVC formulation, it was interesting to observe that the tri-stimulus values march towards the ideal white co-ordinates of L*= 100, a* = 0, and b* = 0, but follow different paths. In other words, the tri-stimulus values walk along the color sphere in different paths, but all tending towards the same point. At a given concentration of titanium dioxide, the smaller particle diameter pigment approached the ideal white the most amongst the three pigments. The highest Whiteness Index (WI) was achieved by the titanium dioxide with the smallest particle size diameter.
Fiber Orientation Measurements Using a Novel Image Processing Algorithm for Micro-Computed Tomography Scans
Based on previous work at the Polymer Engineering Center, Madison, a novel image processing algorithm has been developed that accurately analyzes fiber orientation distribution in discontinuous fiber-reinforced composites. The developed algorithm is an accurate and time-efficient method to measure the fiber orientation distribution of micro-computed tomography (?CT) scans. In this work, the image processing algorithm is described and verified experimentally. Additionally, the algorithm is compared to a commercially available benchmark software package. In this test case, ?CT scans of samples extracted from compression molded parts were used to evaluate the performance of the algorithm by comparing it to the benchmark. In all cases, the algorithm shows highly accurate fiber orientation measurements and the results show that it can compete with the benchmark software.
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