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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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.
A Study on the Morphological Properties and Foaming Behavior of PS/Polyolefin Blends
In this study, the blends of polystyrene (PS) with three different polyolefins of polypropylene (PP), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) that consists of 20 wt% polyolefins with/without 4phr UPES interpolymer, were prepared using a twin screw extruder. Scanning electron microscopy (SEM) was used to describe the phase morphology of the blends. The rheological characteristics of neat polymers and their blends were analyzed to evaluate the viscosity ratio of blends and the interaction between dispersed and matrix phases. Finally, the foaming behavior of PS/polyolefin blends in the presence of supercritical Co2 were studied by using a batch foaming technique at 140°C and 145°C under 1500psi pressure. The results show that the higher interfacial area of LLDPE dispersed phase in the PS matrix plays a key role in controlling the cell size, cell density and expansion ratio and improve the foaming behavior of the PS.
Different Failure Regimes in Dynamic Loading of Glass Reinforced Materials
In this work, a method is provided to distinguish brittle failure from ductile failure. It is shown that dynamic loading results in a clear difference in the effect on time-to-failure for both failure mechanisms, i.e. accumulation of plastic strain and slow crack growth. The effect is explained by analyzing both mechanisms separately and the method is applied on multiple glass reinforced materials, since the failure mode of these materials seems rather brittle. As is shown, this might also offer an easy tool to estimate the lifetime under static load, although it still has to be validated.
New Methods for Quality Control of injection-molded Parts
Besides functionality, the appearance of products has become a major factor for the buying decision of customers. Especially high-gloss facing parts which are generally produced through injection molding enhance the look of products. However, quality control is still performed manually which is tiring and tedious work and provides subjective results. Machine vision methodologies provide objective, reproducible results and can be implemented into a process line. Especially methods based on deflectometry show promising results for high-gloss parts.
Effect of D-content on CO2 solubility in PLA
The pressure-volume-temperature (PVT) behavior of Poly Latcic Acid (PLA) with dissolution of CO2 was investigated using an in-house visualization device; experiments were carried out at 453 K and 473 K, and pressure was varied from 6.894 MPa to 20.684 MPa. The results indicate that as the temperature increases, the swelling decreases, whereas an increase in pressure results in an increase in swelling. The effect of molecular weight (Mw) on swelling volume was also investigated by experimenting on different grades of PLA with varying Mw. The result is that molecular weight does not have a pronounced effect on swelling volume. The effect of talc on swelling ratio was observed by the addition of 5% talc content in PLA 3001D. A comparison was made between theoretical and experimental swelling volume ratios; the theoretical data was obtained using SS-EOS and SL-EOS.
Application of Extended Finite Element Method to Determine the Plane-Strain Essential Work of Fracture of Polyethylene
The applicability of the extended finite element method (XFEM) coupled with known data-based cohesive law to simulate the polyethylene cracking process in fracture specimen testing is studied. The essential work of fracture (EWF) concept was employed in such XFEM simulations to characterize the plane-strain fracture toughness of two grades of polyethylene. Results show that the XFEM simulations with crack growth modeling successfully worked with the EWF concept to predict the fracture toughness within the plane-strain limit. The plane-strain toughness values obtained from the simulations agreed well with the experimental data provided in the literature by Janko, et al., and Ting, et al. [2, 3] for these two grades of polyethylene.
A Multiphysics Approach Applied to Bottle Dispensing
This case study is the first attempt to look at the bottle dispensing problem in a single multiphysics approach. The objective of the study is to report the flow rate variation during the dispensing process. The case study investigates the effects of blow molding conditions, the structural behavior of the bottle, and the presence of a liquid inside the bottle on the dispensing behavior. This requires a close look at the blow molding process to obtain the final material distribution of the bottle. Then a detailed examination of the structural behavior of the partially filled bottle, taking into account the variable material distribution, is considered. Finally, the effect of the liquid presence on the dispensed flow rate variation with time is considered while taking into account the liquid detailed flow properties. The proposed multiphysics approach consists of detailed blow molding simulation, FEA simulation for the bottle deformation during the dispensing, and detailed CFD analysis of the flow inside the bottle.
Chemical Aging of Elastomers Under Different Environmental Conditions
The use of elastomer components in technical fields is enormously increasing. Elastomers can be used in a wide spectrum of applications including automotive-, machin-ery- and plant engineering, as well as in marine and civil engineering areas. Due to their properties regarding form-ability, workability, flexibility and adhesion, also the research activities are increasingly rising. In particular, the exploration of the aging behavior of polymers is getting more and more attention. With respect to literature, only a few experimental studies are dealing with the aging behavior of elastomers. Experience has shown that the properties of rubber materials can change significantly over time. The field of chemical aging is of particular importance due to the changes of the molecular structure and the cross-linking of the material during the aging process. These changes may in fluence a variety of properties such as weight, tensile and flexural strength. For more accurate predictions regarding the life time of an elastomeric component, all environmental factors need to be thoroughly experimentally investigated. In the light of these statements, more research activities concerning the long-term behavior of elastomers are nec- essary. This is the point where the present contribution attaches. We investigate natural rubber under different environmen-tal conditions. Therefore, we use air, seawater, distilled water, freshwater and salt solutions of 6%, 12% and 24%. The elastomer specimensare exposed to the medium and then aged by using different isothermal temperatures of 23°C, 60°C and 80°C. At predetermined aging times the samples are taken out of the medium and are experimen-tally investigated. Therefore, mechanical, calorimetrical and optical experiments are performed. The evaluated data is pointing out that the material is changing its properties during the aging time. Both soften-ing and stiffening effects can be observed relating to the environmental condition.
Evaluation of 9-Layer Film Blowing Process by Using Variational Principles
In this work, coextrusion experiments utilizing an industrial 9-layer Brampton Engineering coextrusion film blowing line for LDPE/LDPE/tie/PA6/EVOH/PA6/tie/LDPE/LDPE film production has been performed under different processing conditions (different air cooling intensity and mass flow rate) in order to evaluate variational principles based modeling approach for the multi-layer film blowing process. It has been revealed that the variational principle based model can describe the bubble shape, temperature profile and predict internal bubble pressure reasonably well for all applied processing conditions even if the multi-layer film has been viewed as the static elastic membrane characterized only by one material parameter - bubble compliance J, which was not allowed to vary along the multi-layer bubble
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