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.
Mechanical properties and damage pattern of a multiaxial textile reinforced epoxy composite was evaluated by tension and bending test. A non crimp fabric (NCF) of [0°,+45°,90°,-45°] stacking sequence was used as reinforcement. Through the identification of the initiation sites and the coalescence of cracks was possible to correlate the damage with the textile geometry and its effect on the mechanical properties. Fractography was used as a tool to identify governing mechanisms and link these to the material internal structure and the textile geometry. Acoustic emission technique was employed to identify the mechanisms of fracture by correlating the signals of mechanical waves produced my damage with fracture stages. Additionally the effect of textile architecture on the composite mechanical properties and damage pattern was correlated with its damage initiation and propagation. Through a combination of experimental work and theoretical studies the mechanisms controlling the mechanical behavior are explained.
This paper presents the redesign of an existing polymer extrusion line involving a 75 mm screw design with a barrier zone and a mixing unit for the manufacturing of PA12 pipes for high internal pressure applications. The existing line was used for the manufacturing of HDPE pipes for gas supply. The new PA12 screw was designed to be used with an axial grooved feed zone. The bulk density was measured as a function of the container depth or bulk height (i.e. screw channel depth) and approximated to a function. A comparison between the improved approximation function and measured data for some common polymer families is shown. The bulk density is an important property of powders, granules and other solids. As a function, it is relevant for the appropriate design of screws to be used with grooved feed section.
A study was coordinated between Washington Penn Plastic (WPP) and a major automaker to investigate multiaxial impact test results under a variety of testing parameters for two polyolefin alloy products — TPO-6087 P Black and PPC5UF0-Natural. It was determined that the use of a lubricated striker consistently lowered energy to maximum load results versus equivalent setups where no lubrication was used on the striker. The optimum test setup with respect to achieving ductile failures for TPO-6087 P Black required an ASTM striker/clamp setup, 2.2 m/s drop velocity, no striker lubrication and an ASTM disc specimen. The optimum test setup with respect to achieving ductile failures for PPC5UF0-Natural required an ASTM striker/clamp setup, 4.4 m/s drop velocity, striker lubrication and an ASTM disc specimen. The effect of sub-ambient temperature conditioning on these two materials —in particular the effect of time from freezer to impact when a remote chest freezer is used for sub-ambient conditioning of specimens —was also studied. It was determined that test results are significantly affected beyond a ten second time interval out of the freezer.
The influence of process parameters, particularly with regard to the cooling rate, on the specific interfacial morphology and strength of paired polymers will be discussed. The focus is on the “cold” interface that occurs during a multi-shots injection molding process. A “cold” interface is consequently defined as the overmolding of a second melt to a chilled, hardened preform. In the experiments three different semicrystalline polymers polyoxymethylene, high density polyethylene and polypropylene were used. Regarding the strength two different types of interfaces were determined and for the visual inspection of interfacial morphology polarized light microscopy was used. The second important interface during injection molding process is the so called “hot” interface or well known as weld line which represents two melt streams meeting. The comparison between hot and cold interfaces presented here will focus on substance-to-substance bonds between plastics. An overview will show the propensity to fail for several thermoplastics, in case there are interfaces in the injection molded part. The strengths of hot and cold interfaces will be compared for certain thermoplastics. In conclusion, new aspects about a correlation between interfacial morphology, bonding strength and injection molding parameters are addressed.
To attain an optimal and efficient bipolar plate, the used material, a ternary compound consisting of polypropylene, graphite and carbon black, as well as the molding process have to be fathomed. Therefore, steps for conditioning the highly filled compound before injection molding are compiled and the behavior of the matrix material polypropylene during thermal-mechanical stresses was analyzed. On the one hand this paper shows the influence of pellet forms (different L/D ratios), moisture absorption and barrel temperature on the resulting electrical resistance of the bipolar plates. On the other hand the consequences of process temperatures above the recommended temperature range of polypropylene are investigated via the dedication of different amounts of a polypropylene-based heat stabilizer masterbatch and residence times.
As polyethylene (PE) pipe is being employed across an ever-widening range of applications, its resistance to rapid crack propagation (RCP) is a primary consideration for designers and end users. Test methods for determining a pipe’s resistance to RCP are the ISO 13478 Full Scale (FS) test and the ISO 13477 Small Scale Steady State (S4) test. Because of availability, low cost, ease of installation, and low maintenance, medium density polyethylene (MDPE) has been a customary material of choice for gas distribution lines for several decades. Presented here are the results of an experimental study to characterize the RCP resistance of chromium catalyst based unimodal MDPE pipe of common sizes using both the FS and S4 tests. While the S4 test results suggest lower RCP performance, the FS test results for all pipes tested indicated very adequate RCP resistance for use in gas distribution lines. This difference is attributed to the fact that the current S4-to-FS correlation factor of 3.6 is not representative of many current generation PE pipes, and a factor of 4.5 is more appropriate. The correlation factor of 4.5 determined from the current study matches very well with previously published data from our laboratory.
For most model-based control algorithms, the control performance is heavily relied on the model accuracy. This paper presents two new Two Dimensional Recursive Least Squares (2DRLS) estimation approaches for batch process system identification, a time wise 2DRLS (t-2DRLS) and a batch wise 2DRLS (b-2DRLS). Both approaches use parameters information from previous batches. The difference between them is that the t-2DRLS uses intermediate computation information from last sampling period, while the b-2DRLS uses the information from last batch but the same sampling period. The proof of convergence of b-2DRLS is given in this paper. Furthermore, both approaches have been applied to injection molding, a typical batch process, to test the performance of the design. An adaptive control scheme has been adopted and the experimental results of injection packing pressure control verified the advantages of the proposed approaches over the traditional RLS.
Polymerization of lactide to polylactic acid (PLA) can be performed using conventional reactor technology such as stirred tank reactors, but the conversion and/or final molecular weight may have to be controlled to a lower level. At higher conversion and/or molecular weight, the reaction mass will become very viscous, which limits the ability of conventional reactor technology to provide adequate mixing, minimize mass transfer effects on reaction kinetics, remove exothermic heat of reaction and ensure proper heat transfer in order to eliminate hotspots/thermal degradation. Kneader reactor technology has been used over 60 years in many high viscosity applications such as reactions and polymerization, devolatilization, and drying. This technology can handle the higher conversion and molecular weight polymerizations of lactide and other copolymers of lactide, while also providing the heat transfer required for proper temperature control. Using model kinetics and rheology data, a study was performed that shows the capability of kneader reactor technology for lactide polymerizations as well as other copolymers. Kneader reactor technology can also be used to remove the unconverted monomers from the polymer and expected results from the continuous operation of a polymerizer and finisher will be shown.
The use of bio-based polymers continues to gain commercial acceptability. With this growth, the need to impart opacity, whiteness, UV protection and printability to commercial articles is becoming more critical. Titanium dioxide (TiO2) is typically the pigment of choice to meet these criteria. While TiO2 is traditionally delivered as a highly loaded masterbatch, it is well known that many bio-based polymers are sensitive to masterbatch processing conditions. Understanding whether bio-based polymers are tolerant of the processing conditions used in high solids loading without significant performance degradation is the subject of this paper. Using polylactide (PLA) as a model system, the compounding performance of highly loaded TiO2-PLA masterbatches is discussed.
A novel floating/swivel platen approach is proposed in this paper for primary package top-load evaluations. Different from the conventional fixed platen top-load practice, this approach, which frees the translational (floating) and rotational (swivel) degrees of the platens and designates them separately to the bottom and top platens, allows tests or simulations to predict the lateral instability of primary packages. The lateral instability of primary packages becomes increasingly crucial to the tray-based unit load stability with growing cost-saving efforts and design innovations from brand owners, design agencies and packaging suppliers. This study, through both lab testing and virtual computer simulation, has demonstrated that the proposed floating/swivel platen approach accurately captures the package top-load reduction induced by the package lateral instability, while the conventional fixed platen top- load practice dangerously over-predicts the package top-load by a factor of as high as 3.6, due to the suppression of the lateral instability by the fixed platens. Such an over-prediction could lead to unexpected damage to the primary packages and/or unit load collapse during storage and transportation. The proposed floating/swivel platen top-load approach is recommended for light- weighting and design innovation in the early package development stage.
Multi-walled carbon nanotubes (MWCNTs) were introduced into poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile copolymer (SAN) blends by melt mixing in an asymmetric mixer. A composition of 70 wt% of PMMA and 30 wt% of SAN was mixed to make a co-continuous morphology. Transmission electron microscopy images of ultra-microtomed samples (70 nm in thickness) showed selective localization of MWCNTs inside the percolated SAN polymer. The occurrence of the double percolation phenomenon resulted in lower electrical percolation thresholds of PMMA/SAN/MWCNT blends prepared at high temperatures. Dielectric spectroscopy indicated a higher electrical permittivity of samples that were molded at 260°C. Due to the higher affinity of MWCNTs to SAN, there was a migration of MWCNTs into the SAN phase during the melt processing.
Cyclic olefin copolymers (COCs) is a novel engineering plastic with excellent thermal and mechanical properties which make them viable alternative to polyolefins. In this study, the solubility of supercritical carbon dioxide (CO2) in COC (Topas 6017) was measured at temperature from 453.15 to 493.15 K and pressure up to 17 MPa by a modified pressure decay system which can be operated in high temperature environment. The volumetric expansion of polymer caused by the dissolved CO2 were calculated by using the Sanchez-Lacombe equation of state (SL EoS) and these volume data were used to correct the apparent solubility data. The results demonstrated that solubility of CO2 in COC increased with the elevated pressure and decreased with the elevated temperature. SL EoS can correlated the solubility within 6% average relative deviation by introducing a temperature dependent interaction parameter. Moreover the COC foams were prepared by using pressure quench process and some preliminary results were obtained.
Metal injection moulding is gaining more and more importance over the time and needs more research to be done to understand the sensitivity of process to different process parameters. The current paper makes an attempt to better understand the effects of holding pressure and process temperatures on the moulded metallic parts. Stainless steel 316L is used in the investigation to produce the specimen by metal injection moulding (MIM) and multiple analyses were carried out on samples produced with different combinations of holding pressure, mould temperature and melt temperature. Finally, the parts were characterized to investigate mechanical properties like density, ultimate tensile strength, shrinkage etc. The results are discussed in the paper. The main conclusion from this study is unlike plastic moulding, the tensile properties of MIM parts doesn’t vary based on the flow direction of the melt, and tensile properties are sensitive to holding pressure and process temperatures. In order to achieve higher tensile strength, higher holding pressure is required. It was also observed that the samples shrunk more in thickness than in the width and length.
Due to the growing worldwide interest in tasks such as environment preservation and recycling, a model of float-valve system for domestic water tanks has been proposed. It considers in its design, the use of an urban waste product such as PET bottles, as the floating device of the mentioned mechanism, having as main idea to contribute with environment care. If the new design is compared with known commercial models, it could be considered as innovative due the reutilization of plastics wastes. At the same time, the system functionality is preserved, and the final parts are easy to fabricate at low cost. Also, the estimation of the Life Cycle Assessment (LCA) for the system shows that the proposed design could be catalogued as environmental friendly.
The main objective of this work was to compare the advantages and disadvantages of using an isolated runner mould comparing with hot and cold runner moulds. It was used CAD and CAE software for the representation of the mould. The isolated and hot runner’s moulds showed advantages regarding volumetric and lineal shrinkages and sink marks of the injected part and there is not loss of material after each cycle by solidification of the sprue and runners when it is compared with the cold runners. The isolated runner mould is less expensive than a hot runner mould.
In Mold Coating (IMC) has been applied to Sheet Molding Compound (SMC) as an environmentally friendly alternative to make the surface conductive; for subsequent electrostatic painting operations. Due to its successful application to exterior body panels made from compression molded SMC, the application of In Mold Coating for injection molded thermoplastic parts is being developed. In order to make the coating conductive, the filler used in IMC is carbon black (CB). However, the injection pressure needed to coat the part is significantly affected by the amount of CB in the coating material. Predicting injection pressures for IMC of thermoplastic parts is more critical than for IMC of SMC. To predict the coating pressures we need to measure the effect of CB on the IMC viscosity. In the present work, we studied the effect of CB on electrical conductivity and viscosity. The pressures needed for coating a typical IMC part with the required conductivity level are estimated.
A novel in-situ anionic polymerization method for preparation of nylon-6/clay nanocomposites in N- methylpyrollidone is explored. Anionic solution polymerization of caprolactam was performed in the presence of montmorillonite clay. The product was obtained as granules. The morphology of the nanocomposites was studied by using X-ray Diffraction (XRD) technique and Scanning Electron Microscopy (SEM). Differential scanning calorimeter (DSC), was used to study the composites transition temperatures and melting behavior. The presence of clay broadens the melting and crystallization peaks and shifts the glass transition temperature and melting point to higher temperature.
Cooling plays an important role in injection molding process. A well designed cooling system can effectively shorten cycle time and improve product quality as well. Nowadays, three dimensional cooling analysis has been applied in injection molding simulation. With this function, a complex cooling system design can be validated with its efficiency prior to actual manufacturing. However, the current simulation tool is not perfect yet since it does not consider turbulent flow and pipe surface roughness effect. In the current study, a latest simulation tool was applied which can predict the turbulent flow effect on cooling. Two cooling systems (conventional and conformal) were designed and simulated. The results were compared to each other which are helpful at the design stage in an injection molding cooling system.
We presented numerical simulations concerning two important defects encountered in the sandwich molding process: the core breakthrough in a thin-walled part and the flow imbalance in a multi-cavity mold. The part thickness largely determines how far the skin melt front advance before breakthrough happens. This limits the size of the part and the maximum core ratio. The skin and core advancement in the multi-cavity system is complex due to the temperature imbalance and pressure resistance variation encountered in the runner. An understanding of the melt flow mechanism through simulation is helpful for the part designer to fully utilize the benefits of the sandwich molding process.
Special applications in plastic engineering require new different polymers. Therefore new polymers and additives are constantly being developed. A lot of these special polymers are not available in databases and cannot be used in simulation software. But it is becoming more and more important to know as much as possible about polymers in order to avoid problems in product development and the manufacturing process. So the polymers have to be tested. This paper shows a possibility of measuring points of flow curves and transforming them into a mathematic model to do molding simulation with the specific material afterwards.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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