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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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
Analysis of Thermal Conductivity of Thermoplastic Hybrid Yarn Textiles Using the Hot Disc-Method Under Process Requirements
Within the research activities in the Collaborative Research Centre 639 (SFB 639) the processing of fiber reinforced thermoplastics is examined and novel thermoplastic hybrid yarn textiles are considered. Since hybrid yarns are non-rigid, the application of these materials causes different challenges concerning their handling during the whole process chain. Thereby, the thermal conductivity plays a significant role for the consolidation process of textile-thermoplastic composites. Dependent on process parameters as applied pressures and temperatures of the analyzed material different thermal conductivities are expected. This paper presents research on the influence of process parameters on the thermal conductivity of analyzed fiber reinforced materials using the hot disc-method.
Molecular Structure and Thermal Properties of Recycled and Virgin Nylong and Their glass Fiber Reinforced Composites
The effects of molecular weight and molecular structure on non-isothermal crystallization behavior of recycled and virgin nylon and their composites with glass fiber (GF) were studied. Two different recycled nylon resins,namely post-industrial waste (PIW) and post-consumer waste (PCW) were used. The former was obtained from a fiber manufacturer and the latter was recycled from used carpets. Intrinsic viscosity (IV) measurements and 13carbon nuclear magnetic resonance (13C-NMR) were used to characterize the molecular weight and the structure of the resins. Non-isothermal crystallization of the resins was studied using differential scanning calorimetry (DSC). The molecular weights of recycled materials (without glass fiber) were found to be higher than that of virgin PA6, but their crystallization rates (implied by the reciprocal of t1/2) were faster. It is due to their higher cis conformer content and consequently advanced segmental mobility. Recycled materials contain TiO2 which can act as heterogeneous nucleating agent.
Preparation and Biodegradability Study of Polymer Blends of Poly(Lactic Acid) and Poly(R)-3Hydroxybutylate-co-(R)- 3-Hydroxyvalerate)
Polymer blends of poly(lactic acid) (PLA) and poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) for biodegrdadable textile application purpose were prepared to improve the flexibility of PLA. using twing screw extruder at 180-190°C. The ratios of PLA:PHBV were varied with 100:0, 90:10, 80:20, 70:30, 60:40, 50:50 and 0:100 by weight. Polyethylene glycol (PEG) having molecular weight of 6000 and 4000 were added to the polymer blends as compatibilizer at 2, 4, 6, 8 and 10 phr. It was found that addition of PEG having molecular weight 4000 g/mol showed better mixing and flexibility. PEG molecular weight 4000 g/mole resulted in higher tensile strength and Young’s Modulus than PEG 6000 g/mole). The biodegradability of PLA/PHBV was analyzed. The crystallization parts in the polymer blends retarded the biodegradation.
3D Simulation of Mucell Microcellular Foam Process in Large Automotive Application
We present a practical study on the large automotive product using a 3D MuCell process CAE tool. Comparisons between conventional injection molding process and MuCell microcellular foam process were done for injection sprue pressure, clamping force, and weight reduction; also, the product warpage were analyzed for two different processes from simulation results. Microcellular cell size distribution and cell density distribution of an automotive instrument panel model were calculated from MuCell process simulation with 30 wt % glass fiber polypropylene and nitrogen super critical fluid, which can provide good reference of determining mechanical properties.
Listening to Your Mold Using Advanced Mold Monitoring Technology
Increasingly mold builders are being asked by their customers if they warranty their work. Traditionally most avoid the question, some answer to it, but very few actually embrace the question. Those that do embrace the topic recognize it as an opportunity to partner with their customer on a common interest: Eliminating unscheduled mold stoppages and downtime. If the mold builder can assist in this, it will differentiate them from others. New tools have been developed in order to enable a mold builder to assist with decreasing mold downtime. A monitor mounted on the mold can be initialized by the mold builder and data can be stored to the monitor device. Among the information to be stored can be the number of cycles that the initial PM should be performed, along with the subsequent intervals for PM's. Also, stored to the device can be maintenance instructions and mold disassembly/assembly drawings. Then, when the molder receives the tool and runs it, the monitor device can be connected to a PC when the mold enters the molder's tool room for service. Once connected, the device sends to the mold builder data on how many cycles have been run and what PM activities have been performed. The mold builder can review this information, and offer any suggestions to the molder in order to avoid any breakdown. In this scenario, the mold builder warrantees the materials and accuracy of the tool, and can monitor that PM's are taking place in order for the performance expectations of the mold to be met.
Effect of Clay Incorporation on the Broadband Dielectric Properties of MWCNT/Polyvinylidene Fluoride Nanocomposites
This study reports on the effect of clay addition on the broadband dielectric properties of multi-walled carbon nanotube/Polyvinylidene Fluoride (MWCNT/PVDF) composites, i.e., 101 – 106 Hz. The three-phase PVDF/MWCNT/Clay composites with different loadings of MWCNT and clay were prepared employing melt mixing method. Characterization techniques, such as X-Ray diffraction and transmission electron microscopy were employed to examine the crystalline structure and morphology of composites, respectively. The dielectric spectroscopy showed that introducing clay into the MWCNT/PVDF composites at the critical MWCNT concentration improved dielectric properties tremendously. For instance, incorporating 1.0 wt% clay into the PVDF/MWCNT composite at the critical MWCNT loading, i.e., 0.5 wt% MWCNT, increased dielectric permittivity significantly (670% at 100 Hz). Furthermore, it was observed that the addition of clay reduced the dissipation factor considerably (68% at 100 Hz).
Fracture Behavior and Mechanical Property of Jute-Glass Hybrid Composite
Jute fiber has gained extensive use in recent years due to its advantage in environmental protection, low cost and low density. However, the limitation of its low mechanical property affects its application. Because of this reason, jute-glass hybrid fiber configuration was considered as an improvement. In this study, 2 kinds of jute-glass hybrid fiber configuration were employed to investigate the mechanical property and fracture behavior in different configuration. At the same time, different plies and different angle of the composite were analyzed. It was found the composite fabricated by B type fabric expressed better properties both on tensile and bending test. Scanning electron microscope observation was also found excellent matching between jute fiber and glass fiber in B type composite.
Low Percolation Threshold and Improved Electromagnetic Interference Shielding Effectiveness of Polypropylene/Carbon Fiber Composites Through Foaming
Injection molding of solid and foamed polypropylene/carbon fiber (PP-CF) composites with different carbon fiber contents (0-20 wt. %) was conducted. ~ 25% void fraction in the foamed composites was achieved using supercritical N2 as the environmentally benign physical blowing agent. The effects of foaming on the percolation threshold, through-plane electrical conductivity, permittivity and electromagnetic interference shielding effectiveness (EMI SE) were investigated. Compared to the solid composites, in addition to the reduced weight of the polymer matrix (25%), introduction of foaming lowered the electrical percolation threshold from 17 wt. % to 11 wt. %. The relationship between the structure and electrical properties was explained in terms of the changes in the fiber orientation and skin layer thickness. At 15 wt. % CF content, the foamed composites yielded an EMI SE of about 25 dB, significantly higher than that of the solid composite (13 dB) with the same CF content. In both solid and foamed composites, the dominant EM attenuation mechanism was found to be wave absorption not reflection. The results reveal the application of injection foam molding technology to manufacture lightweight conductive products with lower fiber content and enhanced EMI SE.
Thermal ageing performance of novel Ultrol® Nuclear 60 year Cables.
Wire and Cable manufacturers generally qualify products for class 1E application by envelope type testing to user specifications and environmental conditions recommended by IEEE standards 323- 1974 and 383-1974. Early cable qualification required only radiation in 1960s. 1960s and early 1970s added thermal aging to ICEA requirement. However the ageing requirement was very minimal (1 week @ 121°C). The long term ageing requirement was not as nearly stringent as present until IEEE 383- 1974 was added to standards. To determine the ability of samples to withstand normal operation, IEEE 383- 1974 introduced ageing samples to “End of Life” condition. Samples were heat aged to a timetemperature condition in excess of 40 years of service life. Federal law and regulation recently allowed electric companies to renew their nuclear plants’ operating licenses for 20 years beyond their original, 40-year license term, which in turn triggered IEEE standard 383-2003 to govern minimum requirements to meet 60 years. General Cable Corporation, GCC simply in this paper, recently completed qualification programs. The major milestones in the development included (a) product life improvement of our established products, Ultol® products, from 40 yrs to 60 yrs. (b) introduction of Ultrol® medium voltage power cable with 60 year life. Cable constructions tested were 600V instrumentation cables, 600V power cables, 600V control cables, 2000V power cables and 15kV Power cables. This paper presents Arrhenius thermal aging data collected for materials used in the qualification programs using IEEE 101-1987 as basis confirms that a 90°C conductor temperature has a life in excess of 60 years.
Fracture Toughness Of A Medical Grade Ultra High Molecular Weight Polyethylene Using A Single Specimen Method
Ultra-high-molecular-weight polyethylene (UHMWPE) has been extensively used in total knee arthroplasty because of its superior physical and mechanical properties. Fracture toughness and fatigue crack growth of UHMWPE has been widely accepted as critical to the structural performance of orthopedic implant bearings. Literature search revealed that the most commonly used techniques to determine the fracture toughness of UHMWPE material are the multi-specimen and single specimen normalization method. In this paper, a novel single specimen method was used to determine the resistance to fracture of GUR 1050 material during a stable crack extension. The crack length extension was obtained using digital microscopy and photogrammetric methods. The test results obtained were compared to the other multi-specimen method data published in the literature.
Feedback Control and Disturbance Rejection in Polymer Extrusion
Feedback control is important for commercial manufacturers of polymer compounds, especially in the extrusion process. The inability to respond to disturbances in the extrusion process results in production of off-specification product and down-time. Due to the complexity of the system, it is difficult to accurately model an extrusion process. The technique of active disturbance rejection control (ADRC) requires a small amount of knowledge of a system, and is effective over the traditional proportional integral derivative (PID) controller. ADRC is currently in use in programmable logic control code on multiple production lines of polymer hose extruders for barrel zones temperature control.
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