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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Effect of E-Beam Sterilization on the Physical and Optical Properties of Medical Plastics
Electron beam (E-beam) exposure is becoming increasingly popular as a lower cost alternative for the sterilization of medical devices and rigid medical packaging. The objective of this study was to determine the effect of E-beam sterilization on several plastics typically used in medical devices and packaging including: copolyesters, polycarbonate, acrylic and cellulosic polymers. Exposures of 25 and 50 kGy (2.5 to 5.0 Mrad) were found to induce significant yellowing. However, color measurements performed at various intervals subsequent to the exposures indicated that the yellowing decreased over time, each plastic to a different degree. Effects of these E-beam exposures on physical properties of these plastics were also determined.
Process Optimization of Injection Molding by Integrating Numerical Simulation with Surrogate Modeling Approaches
An integrated optimization system that can adaptively and intelligently determine the optimal process conditions for injection molding has been developed. Nonlinear statistical regression techniques and design of computer experiments are used to establish adaptive surrogate models that can substitute time-consuming numerical simulation and quickly provide predictions with adequate accuracy for system-level optimization. While the Gaussian process (GP) surrogate model is being refined, a multi-objective genetic algorithm (GA) is employed for the global optimal solutions in a concurrent fashion. The performance and capability of various surrogate modeling approaches—i.e., Gaussian process (GP), artificial neural network (ANN), and support vector regression (SVR)—are also investigated and compared in terms of accuracy, robustness, and efficiency. The examples presented in this paper show that the adaptive optimization procedure helps engineers determine optimal process conditions more efficiently and effectively.
Mathematical Model and Numerical Analysis of Polymer Melt Flow and Heat Transfer in a Cooling Extruder
This paper presents a mathematical model and numerical analysis of momentum transport and heat transfer of polymer melt flow in a standard cooling extruder. The finite element method is used to solve the three-dimensional Navier–Stokes equations based on a moving barrel formulation; a semi-Lagrangian approach based on an operator-splitting technique is used to solve the heat transfer advection–diffusion equation. A periodic boundary condition is applied to model fully developed flow. The effects of polymer properties on melt flow behavior, and the additional effects of considering heat transfer, are presented.
Compressed Viscose Sponges as Actuators
Compressed viscose sponges can be applied in devices in which a force is exerted when the compressed sponge is wetted. These sponges are used as actuator in a device to rescue keys attached to the floating device when it drops in water.Experiments have been carried out to determine the magnitude of the exerted force as a function of the mass of compressed sponges, but also as a function of the gap between the sponge and the object on which the force is exerted.From the experiments it was learned that the gap is predominant. Compressed sponges exert a force which is more than 4 times higher than the case when a gap of more than 1.5 mm exists.
Characterization of Model Urethanes and Ureas Based on Hydrogenated Methylenediphenldiisocyanate via Solution and Solid State NMR Spectroscopy
Models for hard-block segmented polyurethanes were synthesized using a pre-polymer process. Urethane linkages were synthesized using hydrogenated methylenediphenyldiisocyanate (H12MDI) reacted with dimethylol propionic acid (DMPA) and hexanol. Urea linkages were synthesized using H12MDI and hexylamine. The resulting small molecules were then subjected to solution and solid state nuclear magnetic resonance (NMR) spectroscopy to determine the reaction coordinates, to investigate possible side reactions, and to document 13C peaks and reaction times.
Failure Analysis of Polypropylene Used in a Hot Water Environment – Effect of Different Stabilizer Systems
Polypropylene has been used for many years in hot water applications with varying degrees of success. Failures in one instance were traced to a stabilizer package that inadequately protected the polymer in a hot, chlorinated water environment. This same stabilizer system performed extremely well in oven aging tests. The current study involved examination and analysis of failed samples from the field, along with laboratory aging studies designed to replicate the field failures and compare the performance of the stabilizer system in different environments.
New Materials from Polylactide Bioplastics
Renewable resource based bioplastic are the next generation of materials, which will play a major role in building of a sustainable bioeconomy. Polylactide (PLA) is a renewable resource based bioplastic. The realm of PLA bioplastic is expanding through innovative research methodology, products and processes. There is pressing want to enhance the versatility of this bioplastic, so that it can compete with conventional polymers. Inclusion of nanostructures in polymeric matrices is looked upon as unique approach to create revolutionary material combinations. Harnessing the benefits of nanotechnology in generating new biobased material is considered as a benign approach. Biodegradable polymer-clay nanocomposites have already been explored extensively. The niche application of nanotechnology to bring breakthrough research in the field of biobased polymer is still elusive. Recently, polylactide (PLA) has been modified with a new technology based on nanoscopic hyperbranched polymers (HBP) at Michigan State University. The modified PLA has shown a unique balance of stiffness and toughness. Such modified PLA bioplastic will act as ideal matrix for nano-clay, talc as well as natural fiber reinforcements leading to the development of new materials from PLA bioplastics.
Phosphate Esters as Stress Crack Agents – Case Studies in Failure Analysis
With a recent push toward non-brominated flame retardants, phosphorus-based alternatives, such as phosphate esters, are used more frequently for various applications. Their use as plasticizers is also well known. However, their function as environmental stress crack agents of various thermoplastics is less well recognized. Two case studies, one - in which a triaryl phosphate was a component of the formulation, the other – in which it was migrating from an adjacent component illustrate some of the problems with their use. Fractographic analysis and various analytical techniques were used to determine a root cause of each of the two failures.
Multilayer Films of Ethylene Co-Vinyl Alcohol Nanocomposite and Polypropylene for Food Packaging Applications
Retort is a high temperature sterilization process that is used to prolong the shelf life of military rations. Ethylene co-vinyl alcohol (EVOH) /montmorillonite layered silicate (MLS) nanocomposites were co-extruded with retort grade polypropylene (PP) into a multilayer cast film to determine if the addition of MLS to EVOH improved barrier, mechanical, thermal and retort properties. The PP/EVOH-MLS/PP structure showed an improvement in some properties such as water vapor transmission rate, Young's modulus, and seal strength before retort in comparison to the PP/EVOH/PP structure; however, the improvement in properties was lost after the retort process.
Structure and Properties of ?-Polypropylene Cast Films
The effect of ?-nucleation on structure and properties of cast films manufactured from isotactic polypropylenes has been studied. Two commercial-available polypropylenes – homopolymer and random copolymer – were modified by 0.03 wt.% of specific ?-nucleating agent NJ Star NU 100. Cast films were extruded from both starting and nucleated polypropylenes using a slit die and water-cooled chill roll. Supermolecular structure of the films was evaluated using wide-angle X-ray scattering. Tensile testing was used for the preliminary measurement of mechanical properties. A significant effect of the nucleation and solidification temperature on structure and properties of the films was found.
Advancements in Super Low Gloss ABS
The character and impression of an automobile interior is greatly influenced by the gloss and appearance of the interior components. This can have far reaching implications on the choice of polymer for molded-in-color parts. Acrylonitrile-Butadiene-Styrene (ABS) and talc filled Polypropylene (PP) resins are both widely used in such applications and each have their advantages and disadvantages, especially in respect to low gloss aesthetics and scratch resistance. Dow Automotive has recently developed a next generation of super low gloss ABS resins for interior applications, called MAGNUM* SLG ABS.Tool and part design for low gloss aesthetics using ABS resins and talc filled PP resins requires specific attention with respect to filling pattern and process conditions. Talc filled and impact modified PP resins are widely used for interior applications including instrument panels, door parts and pillars due to the versatility in part design and superior aesthetics. The impact-stiffness balance of mass-solution produced high impact ABS is very similar to talc filled impact modified PP, but ABS exhibits superior scratch resistance. Often, the Automotive Original Equipment Manufacturer (OEM) will set sixty degree gloss targets, for example between 1.8 and 2.5 for talc filled PP on specific grain types and/or textures. Achieving these gloss targets, whilst maintaining good scratch and mar behavior is heavily dependent on the texture applied on the mold surface. In an attempt to balance this demand between gloss and scratch and mar performance, additional mold surface treatments are becoming increasingly widespread in the industry. While in the first instance following seemingly opposing routes to achieve the same goal, we shall highlight the synergy achieved between super low gloss resins and secondary mold etching technologies.With this new development the aesthetical shortcomings of ABS resins have been resolved giving the part designer another material option for uncovere
Monitoring Curing Reactions of Thermosets under High Pressure by Use of Raman Spectroscopy
Reactions of many thermosetting materials may be monitored by the use of Raman Spectroscopy. It allows accurate online reaction monitoring for precise curing analysis. Curing is monitored through direct molecular changes thus reducing inaccuracies present when relating macroscopic variables to molecular level reactions. From the spectral changes in peak height or peak area, the curing behaviors were monitored. A high pressure reaction vessel has been designed with a fully automated temperature control, for monitoring the curing of unsaturated polyester and other thermosetting materials under high pressure or vacuum. Processing conditions such as heating rate and pressure will be related to the reaction conversion and material properties. The curing results for unsaturated polyester and epoxy reactions at constant pressures up to 2000psi will be presented.
Failure Mechanism of Panel Leak Formation in Solution Containers
Large-volume flexible solution containers are gaining in popularity in the medical products arena in recent years. The composition of these products often involve materials other than PVC. These products present peculiar engineering challenges, particularly in relation to the formation of panel leaks during packaging, storage, and distribution, due in large part to the volume of solution in the container. An extensive investigation of these panel leaks led to the elucidation of a multi-step failure mechanism. Understanding the failure mechanism directed efforts to enhance the robustness of the final product.
Effect of Dynamic Melt Manipulation and Flow Induced Orientation on Biaxial Stress in an Injection Molded Coupon
This study investigates the effect of locally induced molecular orientation imparted by dynamic melt manipulation based injection molding has on the biaxial stress in an injection molded coupon. Melt manipulation refers to a process where the polymer melt is manipulated during molding beyond normally encountered in conventional injection molding. The technique studied in this paper is Vibration Assisted Injection Molding, where a conventional injection molding machine is augmented by oscillating the injection screw (in the axial direction) during the injection and packing phases. The localized final molecular orientation and morphology that results dictates the resultant product response. Typically improved mechanical properties are observed. For this study the ultimate tensile strength of injection molded polystyrene was investigated. A previous study showed a dramatic tensile strength increase in the regions of higher melt manipulation induced molecular orientation along the direction of flow. To elicit the effect on the strength in the transverse direction, smaller test specimens were machined uniformly perpendicular to the flow length and tested. Comparisons were made with specimens tested axial to the flow.
Surface Properties of Hydrosilylated Polyolefins Annealed in Supercritical Carbon Dioxide
Two hydrosilylated polyolefin compounds, a polydimethylsiloxane (PDMS) end-capped PP and a lightly crosslinked PE sample, are annealed in supercritical carbon dioxide (scCO2). The contact angle, instead of Si concentration, of both samples is found to increase with annealing temperature. Increasing the scCO2 pressure leads to higher Si concentration on the surfaces of both samples, but opposite trends in contact angle: an increase in contact angle on the hydrosilylated PP and a decrease on hydrosilylated PE. The hydrosilylated PP surface shows SiO2 particles after annealed in CO2 at 120 °C.
Distribution of Minor Phase Components and its Influence on the Film-Substrate Interface in Film Insert Moldings
In most cases, the injection molding conditions significantly affect the morphology and subsequently the bulk mechanical properties of the product. This effect is more pronounced when polymer blends or composites are used where the extent of dispersion and orientation of the disperse phases or reinforcements would affect the final property of the molding. In film insert moldings, it is important to ensure that the film is firmly attached to the substrate. Hence, the distribution of the disperse phases (Acrylonitrile-butadiene-styrene in polycarbonate) at the interface is investigated to establish correlations between phase anisotropy, film-substrate adhesion and bulk mechanical properties.
Enhancing the Performance of Polymeric Dyes in Polypropylene
Clarified polypropylene (PP) continues to find increasing uses as polymer and additive improvements allow for its incorporation into applications where resins such as polystyrene or acrylics have traditionally been used . Second and third generation clarifiers have improved the clarity, processing properties, and the organoleptic properties (residual odor and taste), opening the way for more extensive food contact applications [2,3]. With the expanded use of clarified polypropylene comes the need appropriate colorants which will give high clarity, low haze, deep coloration, and no migration. Polymeric colorants have shown to possess these properties, further expanding the market potential for clarified polypropylene. This paper will explore the use of various modified wax compounds and their effects on the residual haze of clarified PP molded with GemToneTM Polymeric Colorants.
Development of an Extended Predictive Controller for Injection Speed
An approach for controlling the injection speed is developed using a new form of predictive control termed extended predictive control (EPC). EPC is a practical scheme that can be implemented on a wide range of industrial processes. The major contribution of EPC is that only one tuning parameter is used in a simple and effective way to tune the process closed-loop response. The main features of EPC are practically illustrated on controlling the injection speed of a 150 tonne machine and three temperature zones on a steel cylinder that used to melt the plastic material inside the barrel. The control performance of EPC is compared with other predictive controllers with improved results.
An In-Process Ultrasonic Approach to Investigating the Relaxation of Orientation and Disorientation of Polymer Melts
The orientation and relaxation behaviors of a low density polyethylene melt after undergoing a shear flow in a restricted channel were investigated by using ultrasound. A capillary rheometer was used to force the polymer melt through a slit die equipped with pressure, temperature, and ultrasound sensors, and the variation of ultrasound velocity traversing the melt was measured. Experimental results revealed that due to different mechanisms involved, the relaxations of orientation and disorientation processes show different dependences on temperature and shear rate.
Hierarchical Structure Developed in PC/ABS Closed Spiral Flow Injection Molding
The internal structures of the injection molded parts are complex and greatly affect on the mechanical properties. The closed-spiral flow injection molded technique was used to observe the microstructure development. Through thickness direction, different morphological structures were observed. The changes in morphology can be abrupt, especially at the regions closest to the external surface of the specimen, while a more gradual transition was observed with increasing depth of the specimen. The width of each layer and the characteristics (i.e. shapes and sizes) of the cavities are believed to have a direct impact on the final mechanical properties of the moldings. Hence, it is essential to understand the morphology of the moldings in order to effectively predict the final properties at different molding conditions.
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