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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A new approach to the control of melt modulation during injection molding processes has been investigated using numerical simulation. Based on a new development in melt flow control for cold runner base injection molding, numerical simulations were used to replicate the behavior of a melt flow with multiple control valves incorporated into a single runner system. It is demonstrated that a new control technique in which all valves can be controlled as a function of ram position allows the user to locally determine the amount of flow in each runner section more precisely.
Blends of linear low density polyethylene (LLDPE), low density polyethylene (LDPE), and high density polyethylene (HDPE) have been characterized in this research work. The main purpose was to generate clear two-peaks from the expanded polyethylene (EPE) foam beads made out of these blends . The blends of 20 wt% of the minor components into LLDPE and a ternary blend of the three components were prepared in a twinscrew extruder at two levels of rotational speed: 5 and 50 rpm. The DSC measurement was carried out at two cooling rates, 5 and 50?§C/min. The results showed that blending with HDPE has a more noticeable effect on the DSC curve of LLDPE than with LDPE. Also, the rotational speed and the cooling rate affect the shape of the DSC curves and the percentage area below the onset point. DSC Characterization of the batch foamed blends revealed the existence of multiple peaks which may be mainly due to the annealing effect during the gas saturation process.
There have been many studies on the cell nucleation behaviors in extrusion. In this paper, an effort is made to utilize the cell nucleation mechanism obtained from foam extrusion to describe that of the structural foam molding process. The mold pressure profile is recorded and used to determine the pressure drop (i.e., super-saturation) that is applied for cell nucleation during the structural foam molding process. The predicted data are compared to the actual obtained cell densities. The results indicate that a variety of cell nucleation technologies developed in extrusion foam can also be applicable to injection molding as long as cell deterioration is prevented.
This paper demonstrates a previously unnoted heat transfer mechanism for solids-conveying in an extruder which certain polymers exhibit. It was found in this study that polyethylenes readily demonstrate bed circulation in a geometry representative of a lid-driven cavity. This granular advective term for heat transfer in the heated chamber resulted in a more rapid rise in overall bed temperature compared to plug-like conditions. The mechanism for this circulation appeared to be a cohesiondominated phenomenon which requires adhesive forces at the rotating surface to exceed the internal cohesive strength of the solids bed. Conversely, other materials like polypropylene and polystyrene did not readily show this behavior except under more extreme conditions.
In this work, a unique approach for designing a nonlinear regression model-based predictive controller (NRPC) for controlling the injection speed of 150 tonne injection molding machine. The innovation of this strategy is that the controller structure allows nonlinear open-loop modeling to be conducted while closed-loop control is executed every sampling instant. Consequently, the system matrix is regenerated every sampling instant using a continuous function providing a more accurate prediction of the plant. The proposed algorithm is implemented on controlling the screw speed for injecting plastic into a mold and controlling the temperature of three steel cylinders inside a barrel in order to melt the plastic. The experimental closed-loop responses of the proposed algorithm were compared to a multi-model dynamic matrix controller (DMC) with improved results for various setpoint trajectories. Good disturbance rejection was attained resulting in improved tracking of multi-setpoint profiles in comparison to multi-model DMC.
This study is aimed at investigating the effect of blending modification with polyethylene (PE) on cell morphology of Polycarbonate (PC) foam. In this study, foamed PC was produced using a dynamic simulation foaming setup designed by ourselves, with supercritical CO2 as foaming agent. The cell morphology of the foamed samples was characterized using SEM. It was found while added appropriate content of PE in PC formulations, melt viscosity and strength of the mixture could decrease, which was beneficial in foaming of PC. But if excessive PE was added, the melt strength of PC/PE mixtures became too low to form cell structure.
Molded Interconnect Devices (MIDs) are plastic substrates with electrical infrastructure. The fabrication of MIDs is usually based on injection molding and different process chains may be identified from this starting point. The use of MIDs has been driven primarily by the automotive sector, but recently the medical sector seems more and more interested. In particular the possibility of miniaturization of 3D components with electrical infrastructure is attractive. The paper describes possible manufacturing routes and challenges of miniaturized MIDs based on two component micro injection molding and subsequent metallization. The technology will be demonstrated by an industrial component.
The main objective of this work is to study the variables affecting the force produced by a plug on a polymer sheet during the thermoforming process, under different testing conditions. The considered variables are: the sheet temperature, the plug speed penetration, and the plug material. The plug material selection, speed and the temperature of testing under biaxial deformation play an important role in the registration of the force and, at the same time, it shall has a strong effect on the experimental data used to set the parameters of the material to determine a constitutive equation.
Biomax Strong is an impact modifier (IM) that is used to improve the physical properties of PLA produced in sheet extrusion applications. Its addition in the range of 1 to 4% into PLA has also been shown to improve the processing characteristics of PLA. Previous studies have shown a reduction in extruder drive power, lower melt temperature and lower extruder head pressure along with improved energy efficiency. This work investigates the processing characteristics of PLA, with and without the additive, in order to gain insight into the mechanisms leading to improved processing. A highly instrumented extruder was used to study how the impact modifier affects solids conveying, melting, melt conveying and power consumption.
In common thermoforming, filling and sealing applications the processes of sealing and cutting are performed in two separate steps. In order to combine sealing and cutting in one station a new device has been developed employing ultrasonic technology so that both functions can be executed simultaneously. The ultrasonic sealing and cutting station reduces sealing times, cutting forces, wear and tear as well as floorspace, facilitating fast format changes. Contaminated rims can be sealed without compromising the sealing integrity and thus preventing any exposure to the atmosphere so that neither food items are permitted to spoil nor medical items loose their sterility. This device provides data for logged sealing quality and is linked with the control system of the entire packaging line.
Polystyrene nanocomposites were prepared using the following compatibilizers: a block copolymer of styrene maleic anhydride (SMA) and various functionalized polystyrenes terminated (on one or both ends) with various polar functional groups (e.g. OH, COOH, acrylate). Solvent mixing was used to promote intimate contact between the organoclay and compatibilizer. A phosphonium surfactant was used to modify the montmorillonite, in order to obtain a thermally stable organoclay. Generally, the best mechanical and barrier properties were obtained with the SMA copolymer.
The rheological behavior and morphology of polystyrene / carbon nanofiber (PS/CNF) composites in their melt phase have been characterized through experimental measurements. Viscosity measurements of the PS/CNF composites in the linear viscoelastic regime show the ratio of the transient extensional viscosity to the transient shear viscosity to be greater than three, the Trouton ratio. This behavior is believed to be due to differences in the flow induced orientation of the CNFs in shear and extensional flow. The orientation development of the CNFs were analyzed by TEM and optical microscope and considered for the relationship to rheological behavior.
The major objective of this work was the study of the injection molding process conditions (holding/packing pressure, injection temperature, injection speed) and the geometry of the mold over the mechanical properties, morphology, orientation and core-skin structure of polypropylene (PP) plaques. Tensile test type IV specimens were cut in MD and TD directions of injected plaques (100 x 100 x 1 mm) with a 1 mmthick fan gate. Two different behaviors were clearly observed: there were groups with strain at break lower than 25% while others exhibit strains at break higher than 700%.
Unique low molecular weight polyphenylene ether telechelic copolymers were designed specifically foruse in a variety of thermosetting resins. These macromonomers have high solubility in common solvents and monomers and tailored functionality, which can react with cyanate esters. The incorporation of these copolymers in cyanate ester resins results in single-phase thermoset material with enhanced performance. Noticeably, toughness increases and moisture absorption decreases with increasing PPE content. Dielectric properties are very low. These cyanate ester/PPE materials show a performance profile well suited for electronics and composites.
Extruded polypropylene (PP) sheet is widely used in the production of thin gauge containers for the food and beverage industry using the thermoforming process. In industry there is not a clear understanding of the relationship between the effect of varying extrusion and thermoforming parameters and the resultant changes in end product properties. This paper investigates the effect of parameters such as chill roll temperature and haul off speed during extrusion, and plug speed and sheet temperature during thermoforming on end product properties such as wall thickness distribution, weight and compressive strength. Test results show several parameters have a large effect on end product properties, with greatest variations between different material grades.
Lead- and chrome-based pigments have been used in synthetic turf due to their performance properties and low cost in use. Environmental and regulatory concerns about these heavy metal-based pigments are leading the synthetic turf industry to voluntarily adopt guidelines that will effectively eliminate their use by 2010. Currently, no drop in" replacements exist for lead-based pigments. The variety of polymers used in synthetic turf further complicates finding solutions. Reformulation strategies using organic and inorganic colorants along with light stabilization systems are presented for several polymers."
Radical Innovation (RI) has been defined by the researchers who published the first study on RI in 1994 as 'a product, process, or service with either unprecedented performance features or familiar features that offer potential for significant improvements in performance or cost.' If these conditions hold, dramatic changes in products, processes or services may change existing markets and/or industries and be responsible for creating new ones. This can occur through several routes including technological discoveries, greatly improved services and processes, and novel business models. Traditional product development efforts result in incremental and platform innovations, however, it takes being comfortable with high uncertainty, seeing and thinking differently particularly about technology and business models, and an element of passion to create Radical or Breakthrough Innovations. This type of innovation is surrounded by high uncertainty and requires different maps, such as learning plans, discovery driven thinking, nontraditional success metrics, and portfolio management rather than project management and traditional gating processes and tools. RI territory will be explored through two case studies involving products and businesses with a focus on plastics and polymers.
In hundreds of projects across many different companies; we have worked with teams who have invented a new technology or product and then wanted to take a 'cookie cutter' approach to capturing value from the invention. Because each invention, by its definition as an invention, is unique and differentiating, we need to at least consider different options. Pre and post invention and pre and post commercialization. Two examples of alternative ways to capture value from invention are exemplified but there are dozens of additional ways to be innovative beyond the cases highlighted. The lesson is that neither client would have followed any other path than to invent its new product and then sell it to traditional customers with the approach they have already taken. The 'tried and true' process.
Abstract #1: Design, Fabrication and Applications of Polymer Microfluidic Biochips Microtechnology is initiated from the electronics industry. In recent years, it has been extended to micro-electro-mechanic system (MEMS) for producing miniature devices based on silicon and semi-conductor materials. However, the use of these hard materials alone is inappropriate for many biomedical devices. Soft polymeric materials possess many attractive properties such as high toughness and recyclability. Some possess excellent biocompatibility, are biodegradable, and can provide various biofunctionalities. I will first give a brief overview of major activities in our center on micro/nanomanufacturing of polymeric materials and microfluidics. An enzyme immunoassay chip will be discussed as an example for a low-cost and mass-producible lab-on-a-chip platform for molecular and biological analyses. The platform is a microfluidic CD for Enzyme-Linked Immunosorbent Assays (ELISA) that reduces cost, accelerates results, and improves reliability of analyses for food borne contaminants, cancer diagnoses and environmental contamination. The presentation will cover (1) optimization and integration of the critical microfluidic and biochip packaging methods developed for CD-ELISA applications, (2) development of manufacturing and detection protocols for the CD-ELISA chips, and (3) evaluation of the performance of CD-ELISA's by validating testing for food borne pathogens and cancer cytokines.?ÿ ?ÿ Abstract #2: Bio-applications of Microfluidics: A flexible microfluidic device to characterize bacterial biofilms We characterize the viscoelasticity of bacterial biofilms by means of a flexible microfluidic device. The biofilms are comprised of Staphylococcus epidermidis and Klebsiella pneumoniae.?ÿ The presence of implanted foreign bodies such as central venous catheters is a key risk factor for infection by bacteria of this kind.?ÿ Because of the sensitivity of biofilm properties to environme
The development of disposable microfluidic devices for rapid point-of-care applications has become central to progress in medical diagnostics and a variety of other fields. Microfluidics is the technology of engineering flow at the micrometer scale, making it possible to perform multiple operations on a single chip. The use of these systems is attractive because they promote reduced sample consumption and analysis time without being restricted to standard laboratory settings. To this end, lab-on-a-chip (LOC) systems have mostly been shown to function in conceptual ways, yet their commercialization and widespread use has been hindered by a number of challenges, which include materials and low-cost fabrication technologies as primary concerns.
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