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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TIPS FOR OPTIMIZING TWIN-SCREW EXTRUDER PERFORMANCE
A collection of 17 techniques is presented for increasing the performance of twin-screw extruders. Processors may be aware of some of these tips, but many are not well known. All are based on solid scientific principles, and have been proven in dozens of extruder installations. Also, all techniques presented are easy to apply, so the benefits can be realized quickly.
ACCELERATED TESTING AND LIFETIME PREDICTION FOR PLASTIC PIPES
Short-term tests are used in many branches of Science and Engineering to predict future outcomes of long-term processes. It is important to ascertain criteria of similarity between the short-term test and real life events. The criteria for predicting lifetime must reproduce the mechanisms of field failures and have a technically sound procedure for extrapolation of a relatively short test data. A quantitative modeling approach as an alternative to “empirical” extrapolation is proposed in this paper.
STUDIES OF DEGRADATION EFFECTS DURING ROTATIONAL MOLDING
This paper describes a program to assess degradation effects on polyethylene, the most common polymer used in rotomoulding. Polyethylene was compounded with a variety of antioxidant (AO) combinations, pulverized to a powder and then rotationally moulded. The impact strength of samples cut from the rotomoulded parts was correlated with assessments of material condition made using Carbonyl Index (CI) and Yellowness Index (YI). Significant differences were observed between different AO formulations.
TROUBLESHOOTING PLASTICS INDUSTRY POWDER STORAGE & HANDLING PROBLEMS USING FLOW PROPERTIES
This paper describes four basic flow properties of powders and bulk solids and how these properties may be used in diagnosing flow problems in existing handling processes. Included are cohesive strength, frictional properties, permeability, and segregation tendencies. Examples of common flow problems in typical handling systems are provided as well as how a specific flow property may be the controlling factor. Using these properties, a system may be evaluated, and corrective actions developed to eliminate the flow-related problems.
VARIABLE STRENGTH STRESS BEAD ANALYSIS IN A TWIN SCREW EXTRUDER
An experiment has been created that relates stress distribution history with residence time distribution. To quantify the results, stress beads that break up at a specific stress were used to measure the percent of material that sees those critical stress values throughout the extruder. Two different strength stress beads were used along with two different mixing section geometries. This paper describes results for a range of different throughputs and speeds in the extruder.
SUREFLO®: A NEW AND HIGHLY EFFECTIVE PROCESS ADDITIVE FOR THERMOPLASTICS
In this paper, we explore the effects of a new process additive, SureFlo®, on the rheological and crystallization behavior of semi-crystalline polyolefins. It was found that SureFlo® can dramatically lower melt viscosities and delay crystallization, resulting in improved processability of the polymer. As we show in a finite-element simulation of a typical injection molding process, the use of 7 wt- % SureFlo® results in significant decrease in fill time and increases productivity by ~20%.
ADDITIVE MIGRATION IN POLYMER FILMS
Additives are commonly blended into polymer films. Oftentimes the additives and the film resins are incompatible, which leads to blooming of the additives to the film surfaces. This research focuses on quantifying the amount of additive exuded to the surfaces over time. Examples include slip agents, anti-fogging agents, and drugs in polyolefin and biopolymer films.
INFLUENCE OF PROCESS PARAMETERS OF AN UNDERWATER PELLETIZING SYSTEM ON THE MOISTURE OF WPC (WOOD-PLASTIC-COMPOSITE) PELLETS
An underwater pelletizing system was used for the production of WPC pellets. In order to avoid the costs of drying prior to injection molding, the pellets must have a low moisture content before bagging. Selected screening results of the effects of different parameters on the moisture of WPC pellets are shown in the paper. By adjusting the appropriate process parameters, producers can save energy and costs by doing without or limiting the following drying steps.
EVALUATION OF FRACTURE CHARACTERISTICS OF POLYETHYLENE BLOWN FILMS USING THE ESSENTIAL WORK OF FRACTURE (EWF) WITH VARIABLE FILM ORIENTATIONS
In this paper, essential work of fracture (EWF) tests for five polyethylene blown films are conducted. The fracture toughness of those samples was evaluated based on test results. The effect of the film orientation on the fracture toughness of materials was evaluated. The work calculated from load-displacement curves obtained from double edge-notched tension (DENT) specimens was analyzed as the ligament increases
EXAMINATION OF THE PERFORMANCE OF A HIGH SPEED SINGLE SCREW EXTRUDER FOR SEVERAL DIFFERENT EXTRUSION APPLICATIONS
This study investigates the extrusion characteristics of a High Speed Single Screw Extruder, (HSSSE), to determine suitability for use in several different extrusion applications including Sheet, Fiber and Extrusion Coating. The study demonstrated that a properly designed HSSSE can greatly improve the processing capability of a small diameter single screw extruder for a wide range of applications.
ENCAPSULATED GRAPHENE WITH POLYSTYRENE BY ULTRASONICALLY INITIATED IN-SITU EMULSION POLYMERIZATION
Graphene was successfully encapsulated with polystyrene via ultrasonically initiated in-situ emulsion polymerization in this paper. The XPS, FTIR, TEM and SEM results confirmed the PS encapsulation of grapheme nanocomposite (PS-G) was achieved through ultrasonically initiating technology without any initiators. The graphenes exhibit good compatibility and dispersion in the PS matrix. The thermal stability of nanocomposites is improved with the incorporation of graphene.
POLYMER EXTRUSION CONTROL SYSTEM DESIGN
In this paper, the overall extruder control system is constructed by two control loops, a multi-input-multi- output (MIMO) control of the barrel temperatures and a single-input-single-output (SISO) control of the melt pressure at die output. Advanced control algorithms are adopted to control these key variables. Experimental results demonstrate the fast response, near-zero overshoot and precise tracking performance of the proposed control strategies. And ultimately the effectiveness of the whole controller is well reflected by product quality.
STUDY OF PRODUCING MICROCELLULAR INJECTION MOLDED PARTS WITH IMPROVED SURFACE QUALITY
This paper describes a novel approach to achieve swirl-free foamed plastic parts using the microcellular injection molding process. With a better understanding of the cell nucleating behavior, which is governed by the degree of supersaturation, one can delay the onset of cell nucleation during mold filling, thereby allowing a solid skin layer to form on the part surface prior to foaming. The theoretical background of this approach as well as the experimental results are presented.
THE INFLUENCE OF FLOW ENHANCED CRYSTALLIZATION ON SHRINKAGE PREDICTION
Comparison is made between a flow-induced crystallization model and measurements made on injection molded samples of a PBT material. The magnitude of shrinkage in the flow direction and the direction perpendicular to flow are found to be in good agreement, as is the degree of shrinkage anisotropy. The flow-induced components of the model are demonstrated to be crucial for the correct prediction of the shrinkage anisotropy.
RECYCLE TECHNOLOGY OF USED PLASTIC MATERIALS
This paper describes the recycle technology of used plastic materials such as waste HDPE films and containers, waste caps for PET bottles, and used PET bottles with caps and films. The fusion joining strength of extruded sheets of waste HDPE films and containers using a compatibilizer was firstly studied. A compounding technology of used PET bottles with caps and films using a compatibilizer was secondly studied.
A NOVEL FOAM INJECTION MOLDING PROCESS USING GAS-LADEN PELLETS
This paper proposes a new foam injection molding process that enables the ease of processing of the chemical blowing agent method with the foaming characteristics of a physical blowing agent, but in a cost-effective fashion. By using gas-laden (CO2 or N2) pellets in injection molding, a simple yet cost- effective dosing method can be achieved. This paper presents this new process and the properties of the injection molded foamed parts.
A CONTRIBUTION FOR QUALITATIVELY MODELING OF FRICTION AND WEAR BEHAVIOR OF THERMOPLASTICS
Tribological parameters are results of a complex system; therefore their behavior can not easily be predicted. This paper suggests a model for characterizing tribological behavior by the distinct contribution of basic friction, and wear modes. These modes and the transition from one to another are influenced by material, geometric, and other system properties. The presented model is based on broadly accepted, mostly two-dimensional, correlations and supported with own pin-on disc friction and wear experiments.
A SIMULATION OF INJECTION STRETCH-BLOW MOLDING PROCESS BY USING A VISCO-PLASTIC MODEL
A finite element simulation of ISBM (Injection Stretch-Blow Molding) Process was conducted based on visco-plastic material model assumption for PET. ISBM process for obtaining a circular PET bottle was designed in terms of stretch displacement and blow pressure. And parametric study was conducted to examine the effect of visco-plastic properties on the final properties of PET bottle. Based on the finite element simulation results, the predictability and limitations of visco-plastic material model was discussed.
THE INFLUENCE OF TEST FREQUENCY AND ECCENTRIC CRACK GROWTH ON CYCLIC CRB TESTS
The cyclic CRB test was standardized recently as an alternative method to characterize the SCG resistance of polyethylene pipe grades. Open questions like the influence of frequency or eccentric SCG are focused on. To study the impact of hysteretic heating, tests with thermal observation of the crack tip were conducted with different frequencies. Moreover, COD measurements were used to study the eccentricity of SCG. Both investigations confirm high reliability and reproducibility of cyclic CRB tests.
SWELLING OF PLA MELT DUE TO CO2 DISSOLUTION
The superior mechanical properties of microcellular foams such as, heat resistance, lightweight and high performance to weigh ratio, are important factors to be considered with respect to the automotive industry and foaming industries. Therefore, an understanding of the thermophysical and rheological properties of polymer/gas mixtures is critically important. This paper focuses on the pure PLA 3001D volume swelling measurement and its comparison with varying talc content. Effect of D content on swelling ratio is also discussed.
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