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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Recent Advancements in Transparent Lexan SLX Resins: Weatherability and Phsical Properties
A new family of transparent Lexan* SLX resins, based on resorcinol phthalate, has been developed that dramatically improve the cost/performance balance over existing resorcinol phthalate containing resins. Like polycarbonate, they have an excellent balance of clarity, toughness and good processability. Unlike PC, the ITR containing resins have dramatically improved weatherability as a result of a photogenerated UV absorber (UVA) on the surface of a part. The photo generated UVA has been found to suppress the photo induced degradation of the resin which would lead to the loss in optical properties (color, transmission and haze) and a loss in physical properties.
Thermoplastic Polyurethane/Polylactic Acid Tissue Scaffold fabricated by Twin Screw Extrusion and Microcellular Injection Molding
Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. They possess rigid and flexible mechanical properties. The TPU/PLA blend tissue scaffolds at different ratios were fabricated via twin screw extrusion and microcellular injection molding techniques (a. k. a. MuCell) for the first time. Multiple test methods were used in this study. Fourier transform infrared spectroscopy (FTIR) verified the presence of the two components in the blends. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between TPU and PLA. Scanning electron microscopy (SEM) images affirmed that the PLA was dispersed as spheres or islands inside the TPU matrix, and that the phase morphology further influenced the surface roughness of cells. The blends exhibited a wide range of mechanical properties that cover most human tissue requirements. It was found from DMA and viscosity tests that 25% PLA significantly reinforces the blends at low temperatures or deformation frequencies.
Plastic Composite Material of Bamboo and Bamboo Charcoal
The use of natural fiber reinforced composites has continuously increased during recent years due to their low density, low cost and environmental friendliness. The use of bamboo biomass plastic has been examined by various researchers because bamboo has a regenerative power, and is leading the bamboo reinforced composites as biomass resources. On the other hand, the bamboo charcoal has various functions, then the following effects can be expected: Good adsorption performance, removal effect for harmful gas and moisture adjustment capability. As current study, a preliminary investigation on the mechanical properties and morphologies of polypropylene (PP) reinforced by bamboo powder and bamboo charcoal were carried out. Additionally, the effect of sandwich structure of bamboo powder and bamboo charcoal on the composites has also been carried out.
Effects of Molecular Weight Changes on the Foaming Behavior of Thermoplastic Polyurethane (TPU) and its Acoustic Properties
This paper investigates the effects of molecular weight changes on the foaming behavior of thermoplastic polyurethane (TPU) and its acoustic properties. In order to vary the molecular weight of TPU, the additional melt extrusion processes are introduced and the foam samples are manufactured via injection foam molding technology. The effects of each additional extrusion process on the molecular weight changes are examined by analyzing heatcycle and rheological behaviors. In addition, the cellular morphologies and acoustic properties of injection foam molded samples are evaluated and their relationships with molecular weight changes are discussed. The foaming behaviors are varied significantly due to reduced molecular weights and different foam structures result in different acoustic performances. In general, the foamed samples from the processed TPU resin are able to achieve higher acoustic absorption coefficients.
Long-Wavelength Laser Welding of Clear Plastics Without Absorbers
The newest advancement in laser welding of plastics involves laser welding of non-pigmented plastic components with a wavelength above 1070 nm. Thermoplastics are partially absorbing in a range above 1500. When exposed to infrared energy within this wavelength range, the work pieces are heated through volumetric absorption and a weld can result. In this study, several commonly used thermoplastics, of varying thicknesses, were welded using a 1908 nm diode laser source. All thermoplastics included in the study were successfully welded. The capabilities of this approach were demonstrated with film and plaque samples.
A Device for Simulataneous In Situ Structuring and Measurement of Rheological Properties of Polymer Blends and Composites
A prototype In Situ Structuring Rheometer (ISSR) was developed to study the shear behavior of polymer blends and composites in tandem with forming material components into a variety of fine-scale structural types. The ISSR utilizes a regime of fluid mechanics known as chaotic advection which enables progressive structure development, whereby specific blend morphologies are derived in sequence from in situ structural transitions. The ISSR resembles a conventional parallel plate rheometer and as such can be incorporated into commercial rheometer instruments. The ISSR provides new means to explore interactions between material components at the micro- and nano-scales, validate theoretical rheology models, and characterize melt properties to support manufacturing processes. The ISSR design and results of initial trials are presented.
Sourcing Bioplastics from Plant-Based Wastes: Examples of Progress
Biobased plastic materials have captured much attention recently, but the raw materials for their building-blocks are typically food crops – not an ideal or sustainable approach. However, obscure biochemical processes are being used to transform organic wastes into useful compounds for polymers and plastics. This paper reviews some recent developments in researchers’ efforts toward exploiting wastes as raw materials, especially plantbased food and industrial wastes. The paper will also discuss the practical issues and commercial limitations of “upcycling” these waste materials into biobased plastics.
Thermo-physical and Optical Parameter Estimation for Pyrolysis Modeling of Fiberglass Reinforced Polymer Composites
To explore the potential use of modeling for the development of fiberglass reinforced polymers (FRPs) with good fire characteristics, parameter estimation based on comprehensive pyrolysis modeling of an FRP composite is conducted. Kinetic modeling is performed using data from TGA and DSC experiments. Different kinetic models are proposed and their effect on pyrolysis modeling is evaluated using a screening process that involves simulation of 1D FRP pyrolysis. This procedure shows that changes in simulation results (mass loss rate) are minor when different kinetic models are applied. Following this work, a sub-set of these kinetic models are used in a parameter estimation process to examine their effect on the estimated parameters. The results show that different kinetic models affect the successful completion of the estimation process. When completed successfully the estimation process demonstrates the possibility of applying numerical optimization to estimate model parameters that can be reproduced from independent standard measurements.
Predicting the Long-Term Ductile Failure of PE-100 Grades Based on Short-Term Testing
In this work, a method to predict long-term ductile failure using short-term testing is presented and validated for a high density polyethylene (PE100) pipe grade. Constant strain rate experiments, performed at different temperatures, are used to characterize the plastic flow kinetics. Combined with the hypothesis that failure occurs when a critical amount of plastic strain is surpassed, this enables prediction of the time-to-failure. We demonstrate that this method enables accurate long-term predictions of pressurized pipe certification tests (time-scale 1 year), based on an experimental procedure that takes approximately two weeks.
Super High-Flow Polycarbonate Copolymers: Development and Overview of Physical and Mechanical Properties
A new super high-flow polycarbonate copolymer derived from bisphenol-A (BPA) and specific biosourced monomer derived from castor bean oil is reported. This copolymer belongs to the class of Lexan* HFD resins known for their improved melt flow and ductility balance compared to standard polycarbonate yet with similar high optical clarity and light transmission properties. These super high- flow HFD copolymers are designed to have all attributes of the Lexan*HFD resins such as lower temperature processing capability, longer injection molding flow lengths and improved low temperature ductility versus a standard polycarbonate material but with superior flow characteristics as the name suggests. The superior flow would enable molding of thinner parts with similar practical impact to standard PC
Recent Advancements in Opaque Lexan* SLX Resins: Weatherabillity and Physical Properties
A new family of Lexan* SLX resins, based on resorcinol phthalates, has been developed that expands the cost/performance envelope. These resins have an excellent balance of weatherability, processability and polycarbonate-like physical properties. The unique weatherability of these resins comes as a result of a photogenerated UV absorber (UVA) on the surface of the part. These resins have excellent gloss and colorability and physical properties in addition to good retention of these properties on exposure to UV radiation making them useful in a wide variety of outdoor applications.
Hybrid Joining Technology - A New Method for Joining High Load Thermoplastic-Metal Mixed Components
The extended utilization not only of mixed joints but also of higher-strength steel and aluminum materials in the automotive and in other fields of the sheet processing industry is setting more stringent requirements on joining technology. These are leading to the increased utilization of low-heat joining methods. In many cases, conventional (thermal) welding and brazing processes exert a negative effect on the base material properties (e.g. reduction in strength) and on the joint attributes (such as increases in hardness and hardening cracking). Moreover, the corrosion resistance may be affected by the burning-off of protective coats. In recent years, combinations of plastics, composite materials and mixed-material structures consisting of metal and plastic are being utilized for either lighter or better- value fabrication. These multimaterial structures can no longer be joined with simple classic joining methods such as welding. A process that has been used since many years is the use of metal inserts in injection molds to join thermoplastic-metal composite structures. In spite of that, there is an increasing need for joining methods which are suitable for assembly and series production for the reliable joining of large-area thermoplastic components with metallic components. One approach to solving these joining technology problems on thermoplastic-metal mixed joints is offered by the combination of mechanical joining and hot-melt adhesive bonding which is presented below. These initial results illustrate the potential. In this article, the method is still carried out in two stages. The simultaneous execution in one process step is under development.
Wedge Ring Coupler: A New Approach for Easy Jointing of Large Bore PE Pipes
We have developed a totally new concept of electrofusion jointing method for large bore PE pipes, d1000 mm and above. The new method completely revolts existing practice with respect to easy installation, fast progress and minimal energy consumption. Compared with standard EF fittings in large dimensions the new technique allows a dramatically reduction in processing time, eases installation and does not require additional devices on site. Basic design criterion of the fittings is maximum reliability in processing of the joint under rough site conditions as well as durable operation of the pipe system. The presentation introduces the new concept, shows the advantages of the new method and highlights processing with respect to practical and economical aspects.
Degradation Mechanism of GFRP in Hot Water and Ultrasonic Wave Inspection
This study was proceeded to understand the degradation mechanism of glass fiber reinforced plastic (GFRP) immersed in hot water. The degraded process of GFRP was investigated through the surface and cross section observation, the weight change, and the bending test with acoustic emission (AE) measurement. As a result, the internal defect of GFRP grew up in the following order, debonding, crack, and delamination, with increasing the immersion time. Firstly, the debonding was appeared as split around the single fiber. Secondly, the crack was generated as connecting to each debonding in fiber bundle. Finally, the delamination was appeared by connecting their defects, and opening layers in GFRP, and then, the bending strength was decreased. In addition, the ultrasonic wave inspection was conducted to detect the internal defect of GFRP nondestructively. The ultrasonic wave echo parameter V value was used to estimate the damage of GFRP. As a result, the V value was decreased with increasing the immersion time by extension of the internal defect of GFRP.
Preparation and Characterization of Noncovalently Functionalized Graphene and its Poly(Vinyl Alcohol) (PVA) Nanocomposites
Noncovalently functionalized graphene can be dispersed and stabilized in water by weak ?–? or van der Waals interactions. In this work, PVA/graphene nanocomposites were prepared by the above method to prevent the agglomeration of graphene sheets during the reduction of graphene oxide. The mechanical properties, including the Young’s modulus and tensile strength of the PVA/rGO (reduced graphene oxide) nanocomposites, were improved by adding graphene sheets. A 55% maximum increase in the modulus was obtained by the addition of only 0.1 wt.% rGO, and an increase of 48% in tensile strength was achieved by adding 0.3 wt.% rGO.
Injection foam molding of highly expanded polycarbonate with open-cell structure using mold opening
A novel strategy was developed to produce rigid highly expanded polycarbonate foams with a porous structure. In order to achieve high expansion ratios in the injection foam molding process, both mold opening and gas counter-pressure (GCP) techniques were adapted for the processing. The microstructure and porosity of the injection molded samples were characterized at several locations. The results show that injection foam molding technology equipped with the mold opening technique and GCP together with tuned processing parameters was able to successfully produce polycarbonate foams with expansion ratios as high as 8 and open-cell contents as high as 85%. The results also revealed that the mold opening length, melt temperature and injection flow rate were the most influential parameters in creating the cellular structure with a high open-cell content.
3D Clogging Modeling of Polyurethane Nanofiber Based Filters by Ultrafine Aerosol Particles
Realistic SEM image based 3D filter model, transition/free molecular flow regime, Brownian diffusion, aerodynamic slip, particle-fiber and particle-particle interactions together with a novel Euclidian distance map based methodology to calculate the pressure drop has been utilized for a polyurethane nanofiber based filter prepared via electrospinning process in order to more deeply understand the filter clogging, filtration cake formation and its role on the final filter efficiency. By using proposed theoretical approach for the 3D filter clogging modeling, it has been found that the decrease in the fiber-particle friction coefficient leads to higher pressure drop, lower filtration efficiency, lower quality factor and lower quality factor sensitivity to the increased collected particle mass due to more deeper particle penetration in the filter and creation of smaller pores mechanism [12-22] have already been performed for micro-fibrous filters. Nowadays, nanofiber nonwoven based filters becomes of high interest due to their ability to reach high filtration efficiency for ultrafine particles with a low pressure drop due to aerodynamic slip around the nanofibers. Unfortunately, till now, the detailed theoretical analysis of the nanofiber based filters clogging has not been performed yet and thus, the full understanding of the filtration cake formation on the nanofiber based filters and its role on the final filter efficiency is not fully understood yet. In order to provide a better understanding of the nanofiber based filters loading process with respect to pressure drop and filtration efficiency evolution, a realistic SEM image based 3D structure model of the filter, transition/free molecular flow regime, Brownian diffusion, particle-fiber interactions, aerodynamic slip and sieve has been utilized in this work.
Visualization of Polypropylene Crystallization in Foam Extrusion Process
In this study, the crystallization of polypropylene (PP) in the foam extrusion process in the presence and absence of CO2 was investigated by in-situ visualization. The results showed that the plasticization effect of CO2 suppressed the crystallization temperature of PP by -15°C during the extrusion process. Moreover, the CO2 molecules reduced the effects of flow-induced crystallization. Visualization results confirmed that crystallization occurs within the die which affects the foaming behaviors of PP. However, inducing the crystallinity more than a critical value decreases the foam expansion ratio due to the increased stiffness of the matrix.
Simulation and Injection Molding of High Precision Plastic BI - Aspheric Lenses for Ophthalmoscopy
The manufacturing of ophthalmic lenses were traditionally by glasses. With the development of polymeric materials and the processing technology, plastic materials have gradually taken place of glass materials in the production of optical lenses. The moulding conditions have critical effects on the optical quality of the moulded lenses. However, the process has not been readily accepted in precision optical fabrication industry because several difficult issues such as geometry deviation, inhomogeneous index distribution and birefringence have hindered the implementation of injection moulding process in high precision optical applications. The scope of this research includes both numerical modeling by Moldflow Plastics Insight 6.1 and experimental approach in order to study the effects of the process parameters on optical performance such as birefringence and index distribution.
PLA Extrusion Foaming Behavior: Effects of Varying Isothermal Melt Crystallization Kinetics
This study investigated the effects of various isothermal-crystallization-kinetics on the extrusion foaming behavior of PLA-nanosilica and PLA-talc samples while using supercritical CO2 as the blowing agent. The results showed that various isothermal-crystallization-kinetics along the second extruder and die affected the PLA’s foaming results differently. At the Tcritical isothermal temperature, the fast growing crystals suddenly dropped the die pressure and caused a nonuniform foam structure whereas at T< Tcritical, a larger number of nucleated crystals contributed to cell nucleation and the uniform foam morphology.
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