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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SPECIALTIES OF THE PROCESSING OF PLA THROUGH EXTRUSION AND INJECTION MOLDING, AND RESULTING CHARACTERISTICS
Next to the established packaging market the interest for biopolymers in technical application increases more and more. Especially the technical industry is interested in substituting oil-based polymers with biopolymers. In view of that, the focus of the work described here was on optimization of injection molding of polylactide (PLA) in order to improve material performance for technical applications. Furthermore, the effects of poly-D-lactide (PDLA) as nucleating agent, fibers and modifiers on material properties (e.g. heat resistance, mechanical properties) are reported.
EXECUTION OF 3 LEVEL FULL FACTORIAL DESIGN TO EVALUATE THE PROCESS PARAMETRS: POLYMER COLOR
The foremost reason of incorporating pigments in polymers is to introduce color either for aesthetic reason or because of functional needs. For dispersion of these pigments, the optimization of extrusion process parameters is required. In present study, a regression model was generated to illuminate the effect of processing parameter on the color properties of polymers by employing a 3 level full factorial design for response surface. The three processing parameters were temperature; speed and feed rate during extrusion of polymer compounding. Design expert software was employed to carry out the experimental designs, statistical and numerical optimization. The analysis of variance (ANOVA) reveals that the color parameters L*, a* and b* are significantly influenced by the considered parameters. The optimization of L*, a* and b* indicates that they are closer to the required target values at 241.9°C, 737.6 rpm and 25.3 kg/hr.
STRUCTURE AND PROCESSING DESIGN OF JUTE SPUN YARN/PLA BRAIDED COMPOSITE BY PULTRUSION MOLDING
Currently, the light has shed on the green composite from the view point of environmental protection. Jute fibers are natural fiber superior on light weight, low cost and environmental friendly corresponding to the green composite materials. Meticulously, fibers of polylactic acid (PLA) thermoplastic biopolymer were micro braided around jute spun yarns and paralleled configuration with jute. The pultrusion experiments were done with jute/PLA yarns and combined with glass fiber yarns to fabricate the tubular composite. Impregnation quality was evaluated by microscope observation of the pultruded cross-sections. The flexural mechanical properties of the beams were measured. The jute/PLA tubular pultrude composite using the parallel configuration of yarn showed the highest bending strength 28.3 MPa and modulus 15.4 GPa with the filling ratio 130% and volume fraction 52%.
NEXT GENERATION UV STABILIZED, IMPACT MODIFIED POLYACETAL COPOLYMER (POM) FOR AUTOMOTIVE INTERIOR APPLICATIONS
As presented at ANTEC 2010, a new family of impact modified Polyacetal copolymers (POM) have been developed that demonstrate improved stiffness, impact strength, and increased weld line performance compared to conventional impact modified POM grades. The unique properties have been achieved through the modification of the polymer backbone. Another drawback of conventional impact modified POM grades is generally poor UV performance, particularly for automotive interior applications. This paper discusses development of a next generation impact modified POM grade which exhibits a good balance of practical part toughness and UV stability in a broad range of colors to meet these demanding automotive interior applications.
NANOSTRUCTURED POLYMER SURFACES TO OPTIMIZE CELL BEHAVIOR
Recently, there has been growing interest to fabricate polymeric nano-structured surfaces with the ability to manipulate and control specific cell functions like proliferation, migration and differentiation. The nano-surface imitates the extracellular matrix, whose topography interacts in vivo with the cells and regulates their activity and morphology. The possibility to optimize the tools for tissue engineering and regenerative cell cultivation will be highly interesting for both the biomedical and polymer processing research and industry. Basic requirement for cells to interact with a surface is sufficient adhesion. Hydrophilic surfaces are known to increase adhesion, so in the first place the polymer surfaces were Corona-treated to enhance hydrophilicity. So in the beginning the target was to examine the Corona impact on unstructured polymer regarding to hydrophilicity (contact angle, surface energy) and surface chemistry (XPS). The results are presented in this work. It can be said that due to the Corona treatment all contact angles decrease with or without UV sterilization, which is equivalent to an increase of hydrophilicity. Furthermore the compared commercial products can be outreached concerning hydrophilicity by choosing appropriate Corona outputs. Hydrophobic recovery did not reach an equilibrium state, but after 10 weeks surface activation is still comparable to commercial references. XPS demonstrated that as result of the oxidation reactions due to Corona treatment polar groups containing oxygen are implemented in the surface. In future the outcome of this work will be combined with the impact of treated unstructured surfaces on cell behavior giving base knowledge, before the influence of nano-structures on cells is determined.
BIO COMPATIBLE FLUOROPOLYMERS AND ADVANCES IN INJECTION MOLDING THESE MATERIALS FOR MEDICAL DEVICES, DRUG DELIVERY SYSTEMS AND STORAGE COMPONENTS
Injection molded fluoropolymers provide the chemical resistance and material performance needed for the manufacturing, storage and delivery of next generation cancer and biologic drug technologies. Fluoropolymers barrier properties, thermal properties and low surface adhesion characteristics offer advantages for powder and viscous liquid manufacturing, storage and delivery components. In the past, fluoropolymer were not often considered for high volume parts with complex geometries due to injection molding process limitations. Developments in mold design and tooling steels combined with new manufacturing equipment and processing techniques now allow the use of these biocompatible materials for high volume drug storage and delivery components.
IMPROVING THERMAL EFFICIENCY OF SINGLE SCREW EXTRUSION
Thermal issues associated with polymer melt extrusion are complex. The process efficiency associated with melting and conveying polymers using a rotating screw inside a barrel is highly dependent upon the frictional, thermal and rheological properties of the polymer, the selected screw geometry, and designated extruder operating conditions including machine set temperatures and screw speed. Melting of the polymer is attained through a combination of thermal conduction and viscous shearing. This process is energy intensive but optimisation cannot be simply indicated by the energy used per kilogram of product. The quality of the extrudate is also of paramount importance. Melt quality can be defined in terms of the value and homogeneity of melt temperature. In this work, in- process monitoring techniques incorporating thermocouple grid sensors, infra-red thermometers and an energy meter have enabled real-time characterisation of thermal dynamics in single screw extrusion, for a 63.5mm diameter extruder. Operation of this extruder has also been simulated using commercial CAE software. Two commercial grades of polyethylene have been investigated using three extruder screw geometries at different extrusion operating conditions to gather evidence relating to process thermal efficiency. Extruder screw geometry, screw rotation speed, extruder set temperatures and material properties were each found to have a significant effect on the thermal homogeneity of the melt and on process energy consumed.
POLYETHYLENE BLENDS CONTAINING POLYMERIC MICROSPHERES FOR MILITARY PACKAGING APPLICATIONS
A low density/ linear low density polyethylene (LDPE/LLDPE) blend was compounded with expandable polymeric microspheres at 1, 3 and 5% loading levels. Multilayer blown films, comprising of a microsphere loaded core with neat blend skins; were processed and characterized for mechanical properties, tear strength, oxygen and water vapor barrier, density, optical microscopy, and thermal conductivity. Significant reductions in thermal conductivity and effusivity, as well as reductions in density were observed at increasing microsphere loading levels.
RENDERING WATERPROOF AND MULTIFUNCTIONAL FIBROUS SHEETS OF CELLULOSE: FROM PACKAGING AND ANTICOUNTERFEIT TO CONSTRUCTION APPLICATIONS
We present a scalable, inexpensive and green process to render cellulosic sheets waterproof with additional functional properties (magnetic, photoluminescent, antibacterial, etc.). The fibrous cellulose-based sheets are treated in their final, dry phase, with a huge potential economic impact in the manufacturing industry. Our method is based on the impregnation of cellulose sheets with acrylate monomers and micro or nano-scale functional fillers solutions, which polymerize as soon as they come in contact with the fibers. The formed polymeric nanocomposite creates a cladding around each individual fiber and not an overall coating onto the cellulose sheets. The treated cellulose fibers can be still recycled due to biodegradability of the used polymer.
MORPHOLOGICAL ZONES IN MICRO INJECTION MOLDING OF POLYOXYMETHYLENE
A Battenfeld System 50 micro injection molding machine was used to produce micro moldings of polyoxymethylene (POM), using a stepwise reduced thickness (0.8 mm, 0.45 mm, 0.2 mm) mold. Polarized light microscopy (PLM) was employed to investigate the morphology of the POM micro moldings. Morphology was examined in both the flow and transverse planes. A variety of morphological zones (oriented skin, shish kebab, cylindrulite, twisted lamellae, oblate, spherulite, etc.) are obtained, depending on the location. The morphology depends strongly on the thickness of the molding and thickness changes. The oriented skin layer tends to diminish away from the gate and near the vent end.
A NEW POLYPROPYLENE/CLAY NANOCOMPOSITE FOR REPLACEMENT OF ENGINEERING PLASTICS IN AUTOMOTIVE APPLICATION
Polypropylene matrix nanocomposites reinforced with organoclay are investigated and their ability to replace some polyamide automotive parts is evaluated. This is so interesting from industrial point of view because of cost saving and ease of processing and recycling. This work is focused on different nanocomposite systems, which are PP/nanoclay, and PP/PA/nanoclay. Also the effect of compatibilizer is presented here. Structures of these systems are studied by using WAXD, TEM and SEM. Mechanical properties of specimens are studied using uniaxial tensile test. As it will be demonstrated, nanoclay sheets tend to disperse in PA particles. On the other hand, introducing nanoclay into PP/PA blends is proven to have a significant effect on the shape and size of PA particles. In addition, incorporation of nanoclay and compatibilizer into PP matrix directly affected the elastic modulus and yield strength, respectively. Finally, it is observed that among different formulations, PP/PA/nanoclay with PP-g-MA shows the most similar mechanical properties in comparison to neat PA. Based on these results, an automotive part (hubcap which is usually made from PA) was manufactured and its performance investigated in service situations as a case study. Automotive manufacturers' standards were considered and all results were satisfactory.
A STUDY ON EFFECT OF SMALL PERTURBATIONS IN COLOUR FORMULATION ON OUTPUT COLOUR OF A PLASTIC GRADE COMPOUNDED WITH A SINGLE POLYCABONATE RESIN
Effect on output colour coordinates, of percent variation in pigments standard formulation is studied through statistical analysis of historical data of a compounded plastic grade manufactured at Sabic IP Cobourg Plant. Aim was to investigate sensitivity of output colour data to small adjustments made during production in pigments standard formulation to reach target colour of the plastic grade, which was a blend of polycarbonate resin, four fillers and four solid colour pigments including one organic – the black, and three inorganic - white, red and yellow. Analysis of the colour deviation caused by these adjustments reveals that output colour values are pretty much sensitive to perturbations made in white, black and yellow pigments amount compared with red. Results of optimization carried out to minimize colour deviation, are also presented for the plastic grade
INFLUENCE OF FIBER LENGTH ON THE FATIGUE BEHAVIOR OF GLASS FIBER REINFORCED POLYAMIDE
Injection molding of long fiber reinforced thermoplastics is a well-established method in automotive industry to mass-produce high quality structural parts without finishing. However, the process generally results in a reduction in fiber length and therefore the maximum fiber length in the parts is limited. Shorter fibers consequently result in reduced mechanical performance. Tensile properties, being static or fatigue, are mainly influenced by fiber length distribution or average fiber length respectively. When applying direct processes, which combine the compounding and the processing of the compound to a finished part, fiber length degradation is widely avoidable during processing. The aim of the present work is to study and compare the fatigue properties of standard injection molded fiber-reinforced polyamide and LFT-compounds processed by injection molding compounder technology. Effort is made to correlate the fiber length to the long-term behavior of dynamically loaded thermoplastic composites. Results of static tensile tests showed considerable improvements in Young’s modulus and tensile strength of composites with longer fibers. Furthermore, high temperature fatigue tests clearly showed that increasing the fiber length in the compound reduces the dynamic creep and improves the dynamic modulus. As a consequence, it is possible to tailor the composite performance by fiber length, and to draw correlations between the structure and the properties of fiber-reinforced compounds.
ELONGATIONAL RHEOLOGY AND MECHANICAL PROPERTIES OF BIODEGRADABLE PLA/PBSA BLENDS
Blends of poly(lactic acid) (PLA) and poly[(butylene succinate)-co-adipate] (PBSA) were prepared using a twin screw extruder. The morphology of the blends was examined using scanning electron microscopy (SEM). Elongational flow properties of the blends and pure components were studied. A strong strain hardening behavior was observed for PLA/PBSA blends, in which PBSA forms the continuous phase (PBSA wt% ? 50). The results of tensile test showed that even for blends containing only 10wt% PBSA, elongation at break increased significantly. By the addition of PBSA to PLA, a transition from brittle behavior (observed for pure PLA) to ductile behavior was observed.
VERIFYING AND IMPROVING THE PLASTIC DEFORMATION OF AUTOMOTIVE INTERIOR PARTS AT EARLY DESIGN STAGE
In the plastic injection molded product development and fabrication, warpage is one of the crucial problems to dominate product quality. In general, the integration of product design, mold design, material selection, and various operation conditions has been regarded as the major factor to warpage. However, the real major effects on the warpage are still not fully under control. In this study, two methods are adopted to systematically investigate warpage quality. One is based on manually flow domain modification under CAE simulation direction and the other is benefited from DOE suggestion of process condition revision. Following the flow behavior guideline, the warpage of original design was improved over 50%, due to suitable pressure compensation to the shrinkage. Meanwhile, according to DOE result, it shows mold temperature is one of the most sensitive parameter. After using the suggested parameters from DOE, the poor warpage problem was also be improved up to 50%.
PROCESSING WINDOW FOR SWIRL-FREE MICROCELLULAR INJECTION MOLDED POLYETHYLENE (LDPE) AND POLYPROPYLENE (PP) PARTS USING SUPERCRITICAL NITROGEN (N2) AS A BLOWING AGENT
The surface swirl-marks on foamed plastic parts is an important issue with microcellular injection molding. Based on nucleation theories and experimental results, processing temperature windows for microcellular injection molded LDPE/N2 and PP/N2 parts were established. Comparisons of the predicted processing windows with the experimental results showed good agreement. Thus, based on these processing windows, the appropriate combination of gas dosage and processing temperature, which leads to swirl- free parts for microcellular injection molding, can be determined.
THE INFLUENCES OF PROCESSING TEMPERATURES AND NUCLEATING AGENT IN FOAMING OF A THIN-WALLED INJECTION MOLDED PART
The injection foam molding of a thin-walled polypropylene part of 1 mm thickness at low, moderate, and high melt temperatures using carbon dioxide, with and without talc, was conducted and the effect of process temperatures and nucleating agent on the cell morphology was thoroughly investigated. The results indicated that by using a modified gate geometry and proper control of the process parameters, a uniform microcellular fine-celled part could be successfully produced. Furthermore, the analysis of foams results produced at different temperatures, with and without talc, showed that in microcellular fine-cell foaming of thin-walled injection molded parts, temperature effect is more dominant.
ISOTHERMAL CRYSTALLIZATION-INDUCED FOAMING OF POLYPROPYLENE UNDER HIGH PRESSURE CARBON DIOXIDE
Crystals can strongly influence plastic foaming behavior, final foam structure and properties. Using an improved visualization system, foaming process of polypropylene was captured and compared with differential scanning calorimetry analysis. It was observed that crystals nucleated and grew into spherulite. At low temperatures, cell nucleation occurred at crystals’ boundaries due to CO2 exclusion from crystal growth fronts and increase in tensile stresses in surrounding amorphous regions. At higher temperatures, these two mechanisms became less apparent.
A STUDY ON RECYCLING OF POLYHYDROXYBUTYRATE (PHB) COPOLYMER AND ITS EFFECT ON MATERIAL PROPERTIES.
This study focuses on the ability of PHB copolymer to be processed a number of times and use of different virgin to regrind ratios. This work studied the effect of regrind levels and heat history on material properties of PHB Copolymer. The material was recycled for 10 regrind generations and also was studies for 7 regrind ratios with virgin material. 79% reduction in viscosity and 10% reduction in ultimate tensile strength were observed for 10 regrind generation. Also a drop of 5% was observed in the viscosity and ultimate tensile strength with a 50:50 virgin to regrind ratio.
INVESTIGATION OF SUPERCRITICAL FLUID-LADEN PELLET INJECTION MOLDING FOAMING TECHNOLOGY(SIFT)
A novel method of producing injection molded parts with a foamed structure has been developed. Compared with conventional microcellular foaming technologies, it lowers equipment costs without scarifying the production rate, making it a good candidate for mass producing foamed injection molded parts. In this study, further research on this method was conducted including: (1) comparison of different physical blowing agents, (2) shelf life of carbon dioxide laden pellets, and (3) optimization of the process conditions
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