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 METHOD FOR CONTROLLING THE BARREL TEMPERATURE IN AN INJECTION MOLDING MACHINE
A new method of obtaining open loop responses of a three barrel injection moulding machine is investigated. The method involves limiting the amount of heat transfer between adjacent zones by using a controller to create an artificial adiabatic wall. Since most barrel zones are run at or near to the same temperature, the system identified by the adiabatic wall method better represents industrial operating conditions. A predictive controller was designed to handle the dynamics of the adiabatic system and compared to a conventionally-tuned controller
THE EFFECT OF COMPATIBILIZER ON MICROFIBRILAR-PHASE FORMATION IN PE/PP BLENDS
The paper focuses on the role of ethylene-propylenediene rubber compatibilizer in the formation of polypropylene microfibrils in polyethylene matrix during extrusion through semihyperbolic die. Several blends varying in phase composition was processed. The structure and properties were examined by scanning electron microscopy DSC and tensile testing. Significant changes in morphology and properties were observed.
ENVIRONMENTALLY SUSTAINABLE THERMOPLASTIC FOAMS: POLYLACTIDE FOAMS VERSUS POLYSTYRENE FOAMS
Polystyrene (PS) foams have a number of desirable properties and thereby have been used for many applications. However, one of the most notable drawbacks of PS foams is its non-biodegradability. In recent years, polylactide (PLA) has been viewed as an environmentally sustainable substitute of PS. In this context, this paper aims to provide head-to-head comparisons between PLA and PS foaming processes, in terms of the cell formation mechanisms and foamability of the resultant foams.
EFFECTS OF E-BEAM IRRADIATION ON MELT BEHAVIOR OF POLY(LACTIC) ACID
In this paper the effects of ionizing radiation on poly(lactic acid) PLA will be investigated. The PLA used in this experiment is a NatureWorks LLC extrusion and thermoforming polylactide resin product code 2002D. Its rheological properties will be investigated. This team worked in conjunction with Mr. Song Cheng and Scott Goetz of Sterigenics and Professor John Bartolomucci of the Pennsylvania College of Technology. The material was irradiated using electron beam radiation. The material was then tested to obtain rheological properties at various dosage levels.
ASYMMETRIC AND SYMMETRIC COMPOSITE FOAMS
In this work, symmetric and asymmetric structural polyethylene foams were produced via compression molding using a chemical blowing agent and wood fibres as reinforcement. By modifying the temperature field in a compression molding process, it is possible to adjust the density across the partƒ??s thickness. Here, the results are discussed in terms of density profile and mechanical properties.
CAVITY PRESSURE CONTROL DURING INJECTION IN AN INJECTION MOLDING MACHINE
Many investigations have emphasized the importance of cavity pressure in determining final part quality in an injection molding machine. During the injection cycle the main factor affecting cavity pressure is the screw hydraulic pressure valve Y3. Cavity pressure has some nonlinear characteristics thus an advanced control strategy is developed. Experiments quantified the relationship between the nozzle pressure and the Y3 valve in order to design a predictive controller. The controller was implemented with good closed loop results.
SIMULATION OF THE FOUNTAIN FLOW EFFECT BY MEANS OF THE RADIAL FUNCTIONS METHOD (RFM)
The fountain flow effect affects the orientation of the macromolecules and the mechanical and optical properties of injection molded parts. The fountain flow effect is modeled using the Radial Functions Method (RFM). In this paper, the flow in a planar slit and a steady state is considered. Good agreement between the obtained results (velocity field, pressure field and front shape) and the existing data in the literature was attained.
INVESTIGATING THE EFFECT OF INJECTION PRESSURE SCREW POSITION BARREL TEMPERATURE AND OTHER VARIABLES ON CAVITY PRESSURE
An investigation into the effect of injection pressure screw position barrel temperatures and other variables on cavity pressure data is presented. This approach consists of monitoring key process data features and using a Projections to Latent Structures (PLS) multivariate modeling technique to correlate injection molding process variables to cavity pressure data.
INFLUENCE OF CROSSLINKING ON RHEOLOGICAL PROPERTIES OF ELASTOMER AND ITS FOAM EXTRUSION
In this paper, the effect of crosslinking on the flow properties in foam extrusion and injection molding was studied using. The change in flow resistance of Ethylene-Vinyl Acetate (EVA) from partial crosslinking of the resin was characterized, with and without the influence of the dissolved blowing agent. The shear and extensional viscosities of the resin were approximated through the analysis of the pressure drop across a Hele-Shaw die channel. The influence of blowing agent on the viscosity of the EVA resin was also investigated.
DEVELOPMENT OF CROSSLINKED WOOD FIBER/ELASTOMER FOAMS
In this paper, the development of crosslinked wood fiber/Elastomer foams was investigated using a batch foaming system. Potential cost reduction and improvement of certain mechanical performance are the motivations of this study. The cell morphology of the foamed products was optimized by varying processing. The influence of different parameters on the cell structure was analyzed. The mechanical properties (tensile modulus and durometer hardness) were also measured to pursue the effect of wood fiber.
INCORPORATION OF SILICONES INTIO WOOD USING SUPERCRITICAL CO2
Wood samples have been impregnated with silicones and subsequently crosslinked in-situ by utilizing supercritical CO2 as a solvent and transport medium.These wood-silicone composites have been exposed to controlled thermo-oxidative conditions under load to determine their time to failure. The time to failure of wood samples has been found to be related to temperature through an Arrhenius type relationship. The addition of silicone to wood significantly increases time to failure suggesting that the silicone is acting as a reinforcing scaffold during the thermal degradation of wood.
NEW ENVIRONMENTALLY PROGRESSIVE POLYESTER FR RESINS
New family of ENH flame retardant PBT (polybutylene terephthalate) thermoplastic polyester resins developed is aimed at helping electrical/electronics (E/E) manufacturers and suppliers comply with regulations restricting use and disposal of hazardous substances. The non-chlorinated non-brominated resin based on PBT delivers good ductility and strength than other nonhalogen flame-retardant PBT materials as well as electrical properties of standard flame-retardant PBT materials. Some of the resin properties will be discussed in this publication.
THE EFFECT OF EXTENSIONAL STRESS ON FOAMING BEHAVIORS OF POLYSYTRENE BLOWN WITH CARBON DIOXIDE
Stresses can induce cell nucleation and affect the final cell morphology in plastic foaming processes. In our previous work, a novel batch foaming visualization system was developed in order to capture the in situ foaming process of a plastic specimen under extensional stress. Using the visualization system, this paper elucidates the effects of extensional stress on the foaming behaviors of polystyrene blown by carbon dioxide as processing conditions are varied.
FATIGUE TO CREEP PREDICTION IN BIMODAL POLYETHYLENE
This paper describes the numerical analysis of cell growth during the filling and post-filling stages in injection foam molding. The pressure change with regard to a Lagrangian framework, as well as temperature distribution, was calculated using the Finite Element Method. The foaming initiation line was predicted by utilizing the solubility of the blowing agent in polymer. Individual bubble growth during the filling and post-filling stages was simulated using the Cell Model. Furthermore, cell trajectory during the filling stage was tracked.
NUMERICAL ANALYSIS OF CELL GROWTH DURING FILLING AND POST-FILLING STAGES IN INJECTION FOAM MOLDING
This paper describes the numerical analysis of cell growth during the filling and post-filling stages in injection foam molding. The pressure change with regard to a Lagrangian framework as well as temperature distribution was calculated using the Finite Element Method. The foaming initiation line was predicted by utilizing the solubility of the blowing agent in polymer. Individual bubble growth during the filling and post-filling stages was simulated using the Cell Model. Furthermore cell trajectory during the filling stage was tracked.
INFRARED THERMOGRAPHY APPLIED TO THE TENSILE TESTING OF PLASTICS
In this study, polypropylene tensile bars were tested at rates of 50, 100, 200, and 400 mm/min while monitoring their heat output using an infrared video camera. Stress-strain-temperature curves and plots correlating mechanical work with heat output were then generated. The results demonstrate that changes in deformation behavior may be quantified via this approach, providing a new means of relating loading conditions, microstructure and ultimate properties.
THE MICROSTRUCTURE AND QUALITY OF LASER-WELDED JOINTS
The microstructural characteristics of laser-welded joints of PC PA-6 and PA-6 reinforced with 30% glass fibers were examined using optical and polarized light microscopy and scanning electron microscopy. The influence of laser power on the tensile strength of the laser-welded joints was examined and discussed in terms of various microstructural aspects. The melt fronts at the contact interface of PA-6 joints were monitored as a function of laser power. Glass fiber re-orientation in the reinforced PA-6 was also examined.
POLYETHYLENE – LAYER DOUBLE HYDROXIDE NANOCOMPOSITES: FLAMMABILITY AND THERMO PHYSICAL PROPERTIES
Layer Double Hydroxides (LDH) as flame retardants are a growing interest. The quest for non-halogen flame retardants has led to the need to find non-toxic flame retardants for commercial use in polymers. This article reports the thermal and flammability properties of linear low density polyethylene (LLDPE) incorporated with LDH. The objective of this project is to evaluate the flame retardance of polyethylene. Thermophysical measurements and tensile results are also conducted.
NANOSCALE IR SPECTROSCOPY OF POLYMER SYSTEMS USING AN ATOMIC FORCE MICROSCOPE
We describe a lab based AFM based IR measurement capability that can obtain local spectra and IR maps over the spectral range of 1000-4000cm-1 with spatial resolution as high as 100nm. We demonstrate this new capability on a polymer multilayer.
A STUDY OF FOAMING MECHANISMS IN ROTATIONAL MOLDING
The presented research focuses on the fundamentals of the foaming process in rotational molding and control of final cellular structure. The experimental results of foaming experiments, performed under isothermal and non-isothermal conditions, indicate that the foaming process could be divided into three distinct phases: bubble nucleation, bubble growth and bubble coalescence. It was found that bubble growth and coalescence mechanisms are dynamically competing during the entire foaming process and the degree of uniformity and structure of the final foam are primarily determined by the nucleation stage.
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