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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PRELIMINARY FAILURE EXAMINATION OF A TOOL USED IN TYRE WASTE RECYCLING - CASE STUDY
Tyres consist of synthetic rubber | metals and linen. Tyre waste decomposes after hundreds of years | and its presence is detrimental for the environment. Standing water | trapped into tires may be a permanent pollution source | while tyre waste next to a forest increases the possibility of fire. European legislation imposes the recycling of tyre waste | which includes the following three steps: shredding in strips | cutting strips in small pieces | and powder production from the pieces. At the last stage magnets remove the metallic pieces | while centrifugal screens remove the linen. Metals are sold to the steel industry as scrap | linen is used in limekiln as a combustion material and the rubber flakes are used in numerous applications (e.g. road surface construction, concrete additives | mouse pads | etc.).
CORRELATION BETWEEN DIFFERENT MICRO-STRUCTURAL PARAMETERS WITH PHYSICAL/MECHANICAL PROPERTIES OF POLYETHYLENE BLOWN FILMS
A wide range of PE materials | including LLDPE, HDPEs and LDPE were used for preparation of the blown films. By changing processing conditions | different structures for these blown films were produced and their structural parameters investigated. Establishing fundamental /structural model between structural parameters and tensile modulus of blown films was the objective of this work. A model for the tensile modulus was proposed and correlated to some structural parameters including crystallinity | orientation factors for crystalline c-axis and amorphous phase | lamellar thickness and crystal size. The measured modulus and calculated one were compared and a reasonable agreement was found between them.
FLEXURAL PROPERTIES AND FAILURE MECHANISM ASSESSMENT FOR ADDITIVE MANUFACTURED LOM BARS ON DIFFERENT BUILDING ORIENTATIONS
Plastic Laminated Object Manufacturing has not been assessed from the flexural properties point of view. The deflection range in parts manufactured by this technique is wider than in parts fabricated by other additive manufacturing methods like SLS or FDM. This fact has increased the interest on the final application of these parts rather than restricted to Rapid Prototyping applications. In this study it will be compared the impact of building orientation and geometric features of parts over the flexural properties. Through optical observation it will be studied the failure mechanism
SEQUENTIAL INJECTION MOLDING: DESIGN CONSIDERATIONS
New injection processes have been developed last decades, improving the designer freedom in order to launch attractive functionalities. All these procedures should be carefully analysed before to decide their use, because it is necessary to understand their natural restrictions, cost and operation requirements and rheological implications in the tools construction. This contribution presents a wide study made in the T.I.I.P., research group from the University of Zaragoza, which gives simulation results and experimental values about sequential injection moulding, and some practical considerations for designers and toolmakers, in order to get successfully results.
KINETCIS AND CHEMICAL REACTIONS OF ACETALDEHYDE STRIPPING PROCESS IN POLY(ETHYLENE TEREPHTHALATE) RESIN
The Kinetics of acetaldehyde (AA) stripping from PET pellets were determined at different temperatures, along with the determination of the residual concentrations of other less volatile compounds such as 2-methyl-1,3-dioxolane (2MD). The rate constants for the polymerization and AA diffusivity coefficients were determined at different temperatures of air stripping of PET. The air stripping of AA from PET is shown to involve chemical reactions and physical changes including polymerization, diffusion and generation of AA, 2MD, EG and water. This paper discusses the mechanisms of the chemical reactions and the formation of the by-products. The techniques used to elucidate the mechanism include gas chromatography (GC), intrinsic viscosity (IV), and density.
FEED ENHANCEMENT TECHNOLOGY FOR LOW BULK DENSITY MATERIAL INTO CO-ROTATING TWIN-SCREW COMPOUNDING EXTRUDERS
Effectively feeding low bulk density material into a co-rotating twin-screw extruder has always been a challenge. However with the introduction of even finer particle size fillers (sub-micron in some cases) as well as new generations of polymer reactor resins, the issue has become even more problematic. Additionally as bulk density decreases, the materials tend to fluidize more easily. Fluidization lowers the “effective” bulk density even further and exacerbates feeding issues. Typical unit operations within the compounding process where material is more susceptible to fluidization are: transfer from storage vessel to feeders, from feeder to twin-screw extruder and within the feed zone conveying section of the twin-screw extruder. While there are methods to minimize the potential for fluidization such as dense phase conveying from storage to feeder, minimization of the feeder height above the extruder feed opening, incorporating a vent into the feed hopper, extending the length of the conveying zone in the extruder feed section, the process eventually reaches a feed volume limitation, which more often than not is well below an economically viable production rate. This paper will review a new Feed Enhancement Technology (FET) that provides significant improvement for the introduction of fine particle / low bulk density materials into the extruder.
Co-rotating Fully Intermeshing Twin-screw Compounding Extruders Technology: Advancements for Improved Performance and Productivity
The co-rotating fully intermeshing twin-screw extruder is the primary production unit for compounding of polymer based materials. It also has had a long term presence in processing material in the chemical and food industry and more recently in pharmaceuticals. While this equipment celebrated its 50th anniversary several years ago and might be considered a “mature” technology, it has not experienced a decline in new developments as might be expected, but rather a significant number of advancements continue to evolve. This paper will highlight several significant developments of the past 10 to 15 years. These are the implementation of high torque (power) designs, the use of increased rpm in conjunction with high torque for improved operating flexibility and productivity, and finally a technology breakthrough for feeding difficult to handle low bulk density materials.
COMPUTATIONAL ANALYSIS AND DESIGN OF SINGLE SCREW EXTRUDERS HAVING SCREWS OF COMPLEX GEOMETRY WITH MIXING ELEMENTS
The methodology is based on some conventional models for flow in the hopper, solids bed and melting zone. In the melt pumping zone the Hele – Shaw approximation is applied, which describes spreading flow in two dimensions. The momentum and energy equations are solved layer – by – layer starting from the barrel wall. This methodology enables significant reduction of computer time required for simulation of extruders with complex screw geometry, over the fully 3D approach. Good agreement was obtained with some available experimental data and further evaluations of predictive capabilities are currently underway.
PROCESSING AND PROPERTIES OF BIOABSORBABLE PLLA-HA COMPOSITES
Orthopedic procedures often require repair materials that can carry large loads without excessive deformation or failure. To this end, we designed composites using two biocompatible/bioabsorbable polymers, poly(L-lactic acid) (PLLA) and polycaprolactone (PCL). The latter was filled with nano-needles of hydroxyapatite (HA), while the PLLA was used in long-fiber form. Theory advises that the HA nano-needles must be of high aspect ratio and be aligned in the matrix to gain sufficient stiffness. We have explored several processing techniques for accomplishing this task, and have successfully made composites in the 8- to 10-GPa range. Variations of this structure will also be described.
STAGES MOULDING A NEW TECHNOLOGY FOR THE PRODUCTION OF PLASTIC PARTS
This paper presents a novel technology to produce plastic parts called “Stages Moulding”. The patented technology allows producing plastic parts with complex shapes, from a wide variety of polymers, with excellent surface quality, reduced thermal and mechanical stresses and possibility to produce parts with reduced weights. This novel process uses cheaper moulds and equipments than those used in injection moulding. The specific characteristics previously mentioned make this technology very promising for the production of plastic parts for different markets. The paper explains the main characteristics of this technology presenting some real examples of parts produced.
DEVELOPMENT OF STARCH BIOBASED AND BIODEGRADABLE PLASTICS FOR THEIR USE IN TRAYS FOR FOOD-PACKAGING
This research work develops new methods to produce biodegradable starch-based trays for the purpose of replacing expanded polystyrene in the food packaging market. The starch based biopolymers present several drawbacks like poor mechanical properties and very high density. In order to overcome these drawbacks two research lines have been set up: blending thermoplastic starch with biobased reinforcements from agricultural wastes like barley straw and grape wastes, and testing the foamability of these materials with a Microwave-foaming method.
RELEVANCE OF THE FEMTOLASER NOTCH SHARPENING ON THE IMPACT FRACTURE OF POLYCARBONATE
The traditional sharpening through the razor blade method employed in the fracture characterization of polymers creates plastic deformation at the notch tip, which affects the fracture toughness values. Recently it has been applied a technique based on femtosecond pulsed laser ablation, which removes material with almost no heat dissipation, preventing melting and thermal deformation of the surrounding area and without plastic deformation at the crack tip. In this work, the fracture toughness of polycarbonate was studied using the Linear Elastic Fracture Mechanics testing procedure at impact velocity, evaluating the influence of crack sharpening by femtolaser or razor blade sliding.
EFFECT OF NANOCLAYS ON THE FOAMING BEHAVIOR OF RIGID POLYURETHANE MONITORED BY X-RAY RADIOSCOPY
X-ray radioscopy is a technique in which a series of radiographies are acquired during an evolving process. The present study aims to investigate the mechanisms occurring during the reactive foaming process of rigid polyurethane (PU) foams in its liquid state. The work addresses a comparative study of in-situ pore growth determination in PU foams with and without nanoadditives (nanoclays), based on the mentioned technique and thus providing a valid methodology to investigate the foaming process in all its stages. The results confirm that nanoparticles addition modify the final pore size most probably based on a higher nucleation rate at initial stages.
POLYURETHANE FOAM NANOCOMPOSITES: RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND FILLER-MATRIX CHEMICAL INTERACTION
Nanofillers are added to rigid PU foams to improve their mechanical properties, however this expected behaviour is not always found. A poor dispersion of the fillers is usually accepted as a possible explanation, but chemical interaction between matrix and fillers could also result in a reduction of the final foam properties. In this study, polyurethane rigid foams (with and without nanoclays) have been produced and characterized. Different dispersion techniques have been used. The experimental results suggested that chemical interaction between fillers and matrix plays a critical role in the mechanical behaviour of these type of systems.
IMPROVING THE THERMAL INSULATION OF POLYSTYRENE FOAMS BY THE ADDITION OF CARBON BLACK.
This paper presents an investigation on the improvement of the thermal conductivity of polystyrene foams by using different types of carbon blacks as additives. Carbon blacks with different morphologies were used as IRblockers. To test the changes in the conductivity foams with densities between 20 and 100 kg/m3 were produced using the solid state foaming technique. The cellular structure and thermal conductivity were analyzed in detail. In addition the thermal conductivity was analytically modeled to study the influence of the different carbon black types on the heat flow by radiation. The best morphology to reduce the thermal conductivity has been detected.
STUDY ON RAPID MANUFACTURING TRAINING NEEDS IN THE EUROPEAN CONTEXT
Rapid Manufacturing (RM), as one of the most important emerging technologies, has a high potential as part of European industry, with a clear role in manufacturing process and economy. In this context, seven EU entities have proposed an e-learning program on these technologies, to increase its knowledge and use, with the aim of improving competitiveness in companies. Results on surveys prepared in this project with the aim of establishing the actual situation in Europe in this field and filled in by companies and training centres are presented in this communication, providing an overview of RM general knowledge and use.
THIN TPO FILM OVERMOLDING FOR VEHICLES INTERIORS DECORATION
Many vehicle manufacturers are aiming diversifying their car interiors with more daring colours and textures with limiting the amount of investment. For large interior parts, like instrument or door panels, special resins or painting technology was considered current state of the art. A new technology, thin TPO film overmoulding, could replace this current state of the art technology. The main paper objective of this paper is to describe the advantages and the issues in using thin thermoplastic olefin (TPO) foil overmolding as an alternative. This paper presents the new generation of TPO “ready for graining” soft foils and the innovative tooling & process needed to laminate the foil during the PP direct injection shot
EXPANDED INJECTED PP SYSTEM TO MAKE 25% LIGHTER ESTHETICAL INSTRUMENT PANEL
By the year 2025, carbon emissions levels will require for the main vehicle in the world important weight reductions. Plastics components can now be expanded during injection keeping correct mechanical behavior to design vehicle interiors. The paper presents the instrument panel application and describes the importance of the Polypropylene (PP) material, the expansion technology and the related component, injection press and tooling designs. The paper aims to demonstrate how applications like visible instrument topper panels or side trimmings could be designed in purpose to respect esthetical and mechanical specifications
PRODUCTION OF POLYPROPYLENE (PP) FOAMS FROM A CONVENTIONAL PP GRADE. ANALYSIS OF CELLULAR STRUCTURE AND MECHANICAL PROPERTIES.
Foaming of polypropylene is not trivial due to its weak melt strength and its semicristalline character. The solutions proposed up to now are based in crosslinking the polymeric matrix or in the use of special polypropylene grades. A collection of samples with relative densities in the range of 0.3-0.6 have been produced using a conventional PP grade. The improved compression moulding foaming process which uses a chemical blowing agent was used to produce the analyzed foams. The effect of chemical composition on both cellular and mechanical properties has been analyzed.
ADHESION BETWEEN POLYPROPYLENE AND STEEL BY OVER MOULDING
In this work, a hybrid polypropylene (PP)/steel car part (Traverse leg) was created by over moulding. PP was modified with 10%wt. of PP-g-Ma coupling agent. Different surface treatments were applied to the steel determining its influence on adhesion. Best peel strength was reached when the steel was sanded. Etching and shot peened plates showed similar but lower levels of adhesion. In all cases, the application of torch heating was necessary to create a thin layer of iron oxide strongly bonded to the steel and by reaction to the PP-g-Ma. To create adhesion a minimum steel temperature of 120ºC was necessary.
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