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.
Bone tissue engineering is a rapidly developing field, and seeks to offer an alternative treatment for bone defects by restoring and maintaining the function of bone tissue. One of the most established approaches is using polymer scaffolds seeded with osteoblast and other growth factors to speed the body’s natural healing processes, decreasing rehabilitation time for patients. The biomimetic design of the scaffolds will need to replicate the structural and mechanical properties of the tissue and be stiff enough to withstand immediate weight bearing. The effectiveness of this approach is determined by examining the properties of the scaffold including porosity, interconnectivity, and mechanical properties. The goal of this study is to create viable polymer/ceramic scaffolds through melt processing of polycaprolactone (PCL) and poly(ethylene oxide) (PEO), combined with hydroxyapatite (HA) and salt (NaCl), followed by porogen leaching. The effects of polymer ratio, ceramic and salt content, and the pressure applied during the fabrication process have been examined in this study. These results will be used to create a factorial design of experiments (DOE) to determine the optimal scaffold fabrication parameters.
This work is concerned with the determination of changes in molar masses of virgin and recycled PET resulting from the action of a chain extender additive compounded in a laboratory internal mixer, based on the processing data provided by the mixer, without further analysis. Results obtained show that the additive increases the molecular weight of both, virgin and recycled PET. Actual values depend on the amount of additive used and processing conditions. The additive tested is more efficient increasing the molar mass of the virgin versus the recycled resin (more additive is needed to obtain the same relative increase).
The present work is concerned with the preparation and characterization of composites of poly(3- hydroxibutirate) (PHB) and vegetal fiber from the mesocarp of the babaçu palm tree fruit. Composites with 5, 10 and 20% micronized babaçu fibers of two different granulometries were prepared in an internal mixer, and characterized by melt flow rate (ASTM D1238) and optical microscopy. Results indicate that the PHB is thermally unstable at all admissible processing conditions, and that partial degradation of the matrix in the resulting composites must be taken into consideration. On the other hand, the analysis of low-magnification optical microscopy images showed that excellent dispersion was obtained for all loadings and particle sizes tested.
Biodegradable polymers are used to fabricate porous scaffolds for tissue engineering. Among different scaffold fabrication techniques, thermally induced phase separation (TIPS) is valuable because of producing highly porous scaffolds with interconnected structures. The effect of adding hydroxyapatite (HA) to poly (lactic-co-glycolic acid) (PLGA) scaffolds as well as other TIPS parameters was investigated in this study. The ultimate goal is to fabricate porous scaffolds that are mechanically functional, while they provide the desired porosity and pore interconnectivity for cell migration, cell growth, and transport of oxygen and nutrients.
In this research, injection molding was combined with a novel material combination, supercritical fluid processing, and particulate leaching techniques to produce highly porous and interconnected structures that have the potential to act as scaffolds for tissue engineering applications. The foamed structures, molded with Poly(?-caprolactone) (PCL) and Poly(ethylene oxide) (PEO) with salt as the particulate, were processed without the aid of organic solvents, which can be detrimental to tissue growth. The pore size in the scaffolds is controlled by salt particulates and interconnectivity is achieved by the cocontinuous blending morphology of biodegradable PCL matrix with water-soluble PEO. Nitrogen (N2) at the supercritical state is used to serve as a plasticizer, thereby imparting moldability of blends even with an ultra high salt particulate content, and allows the use of low processing temperatures. Interconnected pores of ~200 ?m in diameter and porosities of ~72% are reported and discussed.
The rectangular foamed polystyrene plates were molded using microcellular injection-compression molding (MICM) and standard microcellular injection molding (without compression, MIM). The cellular structures of both MICM and MIM samples were investigated. The results showed the compression can further change the cellular structure formed in the injection stage of MICM. Taking 4 mm-thick sample as an example, the thicknesses of the outer zone, where irregular striations-shaped cells dominated, decreased about 25% at different positions along the melt flow direction. In the inner zone dominated by ellipsoidal cells, the cell size distributions at different positions, especially near the sprue, became narrow. Finally, a cellular development mechanism in the compression stage of MICM was proposed. The narrow cell diameter distribution in the inner zone resulted from the collapse of some small cells and decrease of some large cells.
In this work, the extensional viscosity of polypropylene (PP) melt was determined by the rheotens test. Three different extrusion velocities were employed and the extensional viscosities were calculated following a “Newtonian local approach”. A new test mode, the “steady state rheotens test”, was tentatively used to obtain a reliable extensional viscosity. The results indicate that the extensional viscosity increased with the increase of extrusion velocity in the standard rheotens test. In the steady state rheotens test, the influence of extrusion velocity on the extensional viscosity was eliminated and a superposition of the extensional viscosity curves appeared at relatively low extrusion velocities.
The metal injection molded hinge product is breakdown after sintering. The goal of this research is to find out and solve the problem. According to the moldflow simulation, the welding line is created nearby side holes which are thinnest regions of the part, because of the race tracking effect. First of all, a suitable polymer material is selected to simulate the flow pattern of metal powder polymer melt and is proved by injection molding short shot experiment. The result shows that the deviation between both of simulation and experiment is less than 3%. In addition, the gate design, such as location, number, and type, is optimalized. The optimal gate design is proposed to move the welding line to a thicker region and the quality of welding line is improved, therefore, the hinge never breakdown after sintering.
Since the introduction of the feed in tariff programs, the construction of large-scale photovoltaic (PV) power plants is rapidly increasing in Japan. As the lifetime of the PV system is demanded for minimum 20 years, some PV panels installed for long time have a reduced ability to generate electric power. The performance degradation of PV panels can be evaluated by only measuring electric-generating capacity at present. It was considered by degradation of a polymer material which is used for the PV backsheet as a possible cause of decreasing electric-generating capacity. In this study, the most commonly used PET film for the PV backsheet was evaluated. The rate of degradation of PET film was investigated by mechanical properties and partial discharge characteristics. It was found that the rate of degradation of PET film could be effectively evaluated by the partial discharge characteristics.
The synergistic non-covalent interactions originating from hydrogen bonding and n-n stacking between sorbitol and tri-silanol phenyl polyhedral oligomeric silsesquioxane (tri-POSS) yield a low viscosity liquid complex [1, 2]. In this research, the influence of carbon nanotubes and nanosilicon is investigated on the stability of the complex liquid and development of composites with isotactic polypropylene (iPP). The values of draw down ratio of spun fibers and viscosity of iPP blends were analyzed.
The objective of this study is to develop a polymer matrix based composite technology for its use in low cost mass transit (automotive) System, considering the matrix/fiber compatibility, stiffness, strength, hardness, damping and moisture absorbance characteristics of Natural fiber Composites. This objective is achieved through formulation of a low cost composite material which meets the required demands for mass transit system and identifying the most economic manufacturing/fabricating process to produce components to be used in mass transit systems as the next crucial step. For manufacturing continuous laminate, commonly used reinforcement materials such as glass fiber as well as new materials such as natural fibers including, grass, bamboo and jute will be investigated in this study. Both hand layup and RTM method using unsaturated polyester resin matrix were used to fabricate continuous fiber laminate. The mechanical properties are measured and compared with respect to the reference material glass fiber composites manufactured through compression molding process. The investigation shows that Natural fiber Composites have mechanical properties as high as glass fiber composites or even higher in some cases. The effect of water absorbance in the case of natural fibers on their mechanical properties was also determined. Such good mechanical properties in combination with light weight and lower cost, makes the use of these natural fiber composites very attractive for low cost mass transit (automotive) industry. The composite performance is analyzed in terms of constituent properties and product quality.
Graphite and graphene particles were employed as nucleating agents to fabricate polystyrene (PS) composite foams in both extrusion and batch foaming processes. The foams were expanded by supercritical carbon dioxide (CO2). The results show that the particle concentration, not particle type and size, is important for the morphology and thermal conductivity of PS foams produced by the extrusion foaming process. In the batch foaming process, particles pre-compounded with PS and particles pre-attached onto the PS pellet surface led to very different foam morphology. Their mechanical properties and thermal insulation performance are being investigated.
Applications, such as sheet and pipe, often require polymers that can resist abrasion during use. This is especially true if the application is to handle a slurry or grit. Although typical HDPE resins have good resistance to abrasion and can be broadly used with different chemicals, there are several applications that need a resin with improved abrasion resistance and good chemical resistance. For example, HDPE pipes designed to handle gritty water based slurries, such as mining slurries, may not be adequate to handle petroleum based slurries. This is especially true if the application is normally at an elevated temperature such as 60 degrees C. This paper discusses the evaluation of various HDPE resins and shows their differences in relationship to the environmental parameters encountered in slurry handling applications along with the processing parameters needed for manufacture. The different HDPE resins were tested at RT, 40 and 60 degrees C and at different immersion times in water and solvents. After the immersion conditioning, the resins were then abrasion tested. A modified HDPE resin shows acceptable abrasion resistance at both room temperature and elevated temperatures in both water and solvent based slurries. Evaluation of processability parameters were undertaken using melt index, spiral flow, and both lab and production extrusion equipment.
The usage of waste tire rubber crumb as a dispersed phase in a thermoplastic matrix has been a topic of study for a long time. In order to obtain ‘value added products’ from polypropylene (PP) and waste ground rubber tire (GRT) crumb composites, the use of compatibilizers was found to be essential. The properties achieved remained inferior and thus GRT based thermoplastic elastomers (TPE) have limited applications. Due to similar reasons not many studies have been carried out on blending devulcanized rubber (DR) and plastics. However, DR being relatively more similar to virgin rubber is expected to perform better than GRT and result in improved properties as compared to GRT. This work expands our previous effort on a statistical analysis of compatibility between DR and PP, and the effectiveness of a sulphur cure system in compatibilization. We further study the role of a peroxide based cure system in detail with respect to compatibilization efficiency.
When a plastic part fails, a tough question is often asked, “Why are a limited number of parts failing?”. This is particularly true with seemingly random failures at significant, but low, failure rates. Two aspects are generally linked to such low failure rates, multiple factor concurrency and the statistical nature of plastic failures. Failure often only takes place when two or more factors take effect concurrently. Absent one of these factors, failure will not occur. Plastic resins and the associated forming processes produce parts with a statistical distribution of performance properties, such as strength and ductility. Likewise, environmental conditions, including stress and temperature, to which the resin is exposed through its life cycle is also a statistical distribution. Failure occurs when a portion of the distribution of stress on the parts exceeds a portion of the distribution of strength of the parts. This paper will review how the combination of multiple factor concurrency and the inherent statistical nature of plastic materials can result in seemingly random failures.
Modern injection mold manufacturing technologies allow internal cooling channels to be made to any shape that follow the precise geometry of the part in the mold. This aids in creating a uniform temperature distribution in the part by targeting hot spots on the part surface with arbitrary shaped cooling channels in the mold. Ultimately these result in better quality parts, shortened cycle times, reduced waste and cost reductions. Simulation of these processes requires a fully transient, three- dimensional (3-D), time dependent computational fluid dynamics (CFD) solution in these conformal cooling channels. This paper presents the further development of a (3-D) finite element based transient mold cooling simulation capability to include a solution for solving the 3-D flow in cooling channels. This new capability forms part of a future release of Autodesk Moldflow Simulation.
Graphene oxide (GO) and benzenesulfonic acid functionalized graphene (GP-SO3H) nanopapers were successfully prepared from graphite. The GP-SO3H nanopaper with 13.7% functional groups after thermal annealing showed superior mechanical strength and excellent electrical conductivity owing to the well dispersed monolayer graphene nanoplatelets. The GO nanopaper, on the other hand, revealed outstanding gas (H2 and CO2) barrier properties. Both nanopapers could be easily coated onto the thermoplastic surface via thermal lamination or in-mold decoration (IMD) in injection molding. The GO nanopaper based polyester thermal lamination films showed very low water and gas permeation, while the GP-SO3H nanopaper coated thermoplastic polyolefin (TPO) plates made by injection molding provided good electromagnetic interference (EMI) shielding properties. When used together with thermoplastics as a laminate, these GO/GP nanopapers have great potential for various industrial applications.
During contour laser transmission welding (LTW), energy is absorbed by the laser-absorbing (ie black) material and immediately begins to redistribute itself by conduction inside the thermoplastic material. If the time over which this energy is deposited is quite long (corresponding to either a low scan speed or very long laser beam length), significant heat flow by conduction can occur before all of the laser energy has been deposited at a given point. For this reason, one cannot perform contour LTW with a classroom laser-pointer – the low power would require a low scan speed to deposit the requisite energy and, during that long time, most of the energy would be lost to the surroundings by conduction and melting would not occur. Conversely, if the time over which this energy is deposited is quite short (corresponding to either a high scan speed or very short laser beam length), very little conduction occurs during the heating period. This allows some simplification to the modeling process such as that proposed by Chen . The question addressed by this paper is, for a given set of material and laser parameters, at what laser scan speed can the effect of thermal conduction during heating be largely ignored. The paper shows that the critical speed is related to the material’s thermal diffusivity, absorption coefficient and the scattered laser beam length.
Rice husk is a major biomass that is abundant, renewable and thus is promising material for the development of biodegradable polymers. The physical structure of rice husks between two different varieties of long grain rice has been evaluated in this study. The results show that the wall of the rice husk consists of 3 different layers with full and hollow fibers with different orientations. The fibers consist predominantly of cellulose and hemicellulose. Rice husk also contains about 10% moisture and about 20- 25% silica. The different varieties of rice husk have a similar structure, but different thicknesses of various layer and different diameters for the fibers. Silica is concentrated mostly in the outer layer and is the main reason why rice husks need to be modified before they can be used to develop biodegradable polymers or employed as reinforcing agents in other polymers.
The University of Wisconsin Platteville, gave a research grant to test and experiment with organic lignin from American Science and Technology (AST) in plastic. The goal is to incorporate a true bond of lignin with plastic, in particular polypropylene, to create a desired set of properties for the customer. A series of tests will be used to examine the compound for these properties, and fine tune the processing parameters. Lignin is known to be found in the second cell wall of most plant life, some algae, as well as trees. It is one of the most common organic polymers found on earth. There is approximately 1.1 million metric tons of lignin used today in various applications. It will be laser cut for tensile testing, notched izod, spectroscopy, weather testing, heat deformation testing, and others. The test data will be analyzed and submitted to the company. This will be a new product that will be used to cut down the cost of production, become the new ecofriendly alternative, and change the way the plastic foot print is viewed in the world today.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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