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 Fiber Orientation For Injection Molded Thermoplastics
The goal of this research is to further the understanding of the relationship between flow properties, orientation, and related mechanical properties of injection molded parts. The properties and behavior of the flow of a fiber reinforced polymer composite during molding is directly related to the stiffness and the strength of the completed part. Flow affects the orientation of the fibers within the polymer matrix and at locations within the mold cavity. Mechanical properties of fiber reinforced polymer parts, such as stiffness and strength, are controlled by the average length of the fibers and how the fibers are oriented. The ability to predict, and ultimately control, flow properties allows for the ability to efficiently design safe parts for industrial uses, such as vehicle parts in the automotive industry. A lab developed simulation packaged has been designed to predict the orientation and modulus of long glass fiber reinforced polypropylene composites. With the improved simulation package, the flexible fiber model was proven to be more accurate for predicting fiber orientation than the traditional rigid fiber model. The goal of this work is to test the universality of the existing model using long carbon fiber reinforced nylon 6,6 composites by injection molding parts and then performing experiments to check their tensile strength and the modulus. The methodology for collecting the data and the ability of the simulation to converge has been proven for the new material. The universality of the simulation package will be determined by comparing the accuracy of the results for the two materials.
Predicting Fiber Orientation in Short Fiber Reinforced Injection Molding Process Using DEM
A new and efficient method using Discrete Element Method (DEM) to perform fiber orientation analysis for short fiber reinforced injection molding process is presented in this paper. This method uses a particle-based approach with one-dimensional two-node tracker particles that are convected by the flow field. Using this particle approach instead of solving a full tensorial equation yields higher accuracy and excellent computational efficiency. The underlying flow field for this analysis is computed using a FEM based simulation of the filling and packing phases of the injection molding process. Two case studies are presented to validate the implemented solution. The results show that the implemented solution is accurate and matches well with experimental data. Strengths and limitations of the model and the ongoing work to further improve this analysis are discussed.
Preparation of Cellulose Nanocrystal-Polypropylene Masterbatches by Water-Assisted Thermokinetic Mix
In an effort to avoid freeze-drying or solvent blending techniques and better leverage the fact that preparation of cellulose nanocrystals (CNCs) result in aqueous dispersions, we investigated a water-assisted melt compounding approach to disperse cellulose nanocrystals in polypropylene. A simple, water-based cetyltrimethylammonium bromide (CTAB) treatment of CNCs was used to reduce their hydrophilicity and inhibit hydrogen bonding. The aqueous suspension of treated CNCs was then blended with polypropylene in a thermokinetic mixer with various levels of a maleated polypropylene (MAPP) as a dispersing agent. CNC dispersion was evaluated by optical microscopy, scanning electron microscopy, and rheology. CTAB treatment alone was insufficient to provide good dispersion but dispersion improved greatly with increasing MAPP content. At the highest levels of MAPP, agglomerates were still present but nearly all were well below 1 µm in size. However, despite a CNC content of 8%, little rheological evidence of a network structure was found that would suggest well-dispersed nanocomposites.
Processing of Functionally Graded Integral-Skin Cellular Polymeric Composites Utilizing Rrfm
This paper presents the processing methods for producing functionally graded rapid rotational foam molded foam composites with supercritical CO2. The cell density of the foamed core is deliberately varied across the length of the part by gradually increasing the talc content from 1 wt% to 3 wt% or by increasing the chemical blowing agent content from 0.5 wt% to 2 wt%. The foamed core of the composite is produced with foaming grade LDPE. The cellular morphology is characterized by its foam density, average cell size, and cell density across the length of the part. A scanning electron microscope (SEM) was used in the characterization process at 37X magnification along with a digital microscope at 30X magnification. The analytical characterization of the foam revealed, LDPE foamed core processing is more suitable when the chemical blowing agent (CBA) is combined with the physical blowing agent (PBA) rather than just utilizing talc with PBA. The cell density within the water-cooled LDPE foam was 1.4e6 cells/cm3 with an average cell size of 137 um. These results demonstrate the capabilities of a new experiment setup designed to combine PBA foam extrusion and RRFM technology.
Pushing the Limits to the Next Level: A New Mold Steel for Demanding Plastics and Biocomposites Designed for the Best Polishability
The increasing use of advanced engineeringplastic compoundsand biocomposites causes problems in the mold thatcan bederivedfrom a combination of wear and corrosion. The degradation of the tool steel resultsin increased maintenance, downtime and in worst case premature breakage of the mold.Manufacturing of optical devices, such as lenses, demands an extremely goodsurface finishof the mold. In addition, it should be reached as fast as possible to reduce lead times.Uddeholm Tyrax® ESR isa newpremium martensitic tool steel from Uddeholm,developed to cope with these problems by combining corrosion resistance with high hardness,very goodwear resistanceand excellent polishabilitywithout compromising on ductility.The recommended hardness of Uddeholm Tyrax® ESR is in the range of 55-58 HRC.
Quantitative Determination of Interfacial Strength of Multilayer Films Using an Instrumented Machine
The ASTM D3359 and ISO 2409 standards are currently utilized to rank the adhesive strength between the coating layer and substrate by quantifying the damaged area across the crosshatched region after a tape pulling. However, these standards neither specify the forces needed to cut the film and rub the tape nor spell out the speed and angle of the tape required during peeling. These uncertainties lead to inconsistent results. Another issue is that the current standards only apply to rigid substrates. Consequently, the above methods cannot be applied to soft multi-layer films for adhesive strength determination. In this study, a new test methodology has been developed for quantitative determination of adhesion in soft thin multi-layer polymeric films. The depth of the surface cutting was controlled using an instrumented machine. The processes of attaching, rubbing, and peeling the tape were also automated by the instrumented machine to allow for repeatable and reliable test results. Lastly, instead of using visual assessment to rank adhesive strength of the multi-layer films as instructed in the standards, our proposed new method will quantify interfacial adhesion between the top-layer and in-layer of the multilayer films based on the principle of energy conservation. Fundamental structure-property relationships on multilayer films can now be established.
Reaction Induced Phase Separation of High-TG Thermoplastic from Glassy Thermoset During Cure
Highly crosslinked, typically brittle epoxide/amine thermosets are commonly toughened with high Tg thermoplastics to afford phase separated morphologies that provide increased toughness without sacrificing high temperature performance. The typically low molecular weight thermoplastics are solubilized into the uncured thermoset system, and as the epoxide:amine reaction proceeds, the rapid molecular weight increase of the thermoset phase leads to a loss of solubility of the thermoplastic and initiates phase separation. The morphology development of reaction induced phase separation (RIPS) occurs between the initiation of phase separation and gelation. The development of these phase separated morphologies is altered by the cure prescription, the time between initiation and gelation, and breadth and depth of the rheological well during cure, all of which alter the growth and coarsening of phase separated domains. In this work, networks are prepared adjusting the loading level of thermoplastics to form a wide variety of network types, including droplet dispersed, network-like pattern co-continuous, and co-continuous networks. The morphology of networks is characterized using optical microscopy, scanning electron microscopy, and the phase separation and cure of the networks is monitored with rheokinetics studies. Cure rates of 1 and 5 °C/min are examined. Thermomechanical analysis confirms network type, and the effects of cure schedule, viscosity, loading level on RIPS morphology development is correlated to control phase separation during cure and target desired morphologies.
Real-time PRESS MEAS during Plasticization and Injection Process and Its Effect on Part WT Variation
The development focus of the injection molding industry has gradually shifted from single-machine to factory-wide intelligence. Accordingly, a crucial research topic has emerged regarding the use of information collected by real-time sensors in injection molding machines to facilitate the integration of science-based software and machines and enhance product quality and machine productivity. In addition to equipment and manufacturing stability, product plasticization quality and characteristics are crucial factors affecting the establishment of a cyber-physical system for smart injection molding. The pressure-specific volume-temperature relationship is an essential attribute of polymers. The specific volume of a polymer varies with molding temperature or pressure. This causes difficulties in predicting the changes of polymer melts during injection molding, and therefore impedes control over product quality and precision. To address the aforementioned problem, this study adopted computer-aided engineering to perform analysis and experiments on the plasticization characteristics and behavior of plastic materials used in injection molding. A measurement system was established and installed on an injection unit to perform real-time measurement and record changes in the pressure of plastic melts during plasticization. The weight of the molded products was also recorded. Several process parameters were explored, including screw speed, back pressure, and melt temperature. The results indicated that (1) screw speed and back pressure exert considerable effects on barrel pressure and part weight; (2) overly fast screw rotation can cause the pressure in the compression section to exceed that in the metering section; and (3) back pressure exerts the greatest effect on barrel pressure and part weight.
Recycling PET into Plastic Lumber at Forward Operating Bases
Recycling of plastic waste at Forward Operating Bases (FOBs) is becoming a topic of considerable interest to the Department of Defense. The ability to recycle plastic waste into plastic lumber that would be of use at the FOBs accomplishes two goals: (i) Reducing the environmental concerns caused by open pit burning of waste plastics (which is now prohibited at many sites) and, (ii) Providing the warfighter with useful materials for infrastructure improvements lessening the need for building supplies that in many cases must be delivered by convoy. This paper describes the investigation of using recycled PET (rPET) to make plastic lumber using flow intrusion molding and the resulting performance characteristics
Reduced Order Kinetic Model for Corrosion of High-Density Polyethylene in Bleach Solutions
A reduced order kinetics model is proposed for the corrosion of polyethylene in bleach solution. Hypochlorous acid (ClOH) is considered as the oxidizing agent which is formed from the hydrolysis of bleach. The model simulates the diffusion of ClOH into the non-polar polymer matrix followed by its dissociation into radicals. The reaction between the radicals and the polymer is phenomenologically modeled using an ordinary differential equation. The model is suitable for coupling with mechanical models for life-time analyses of polymers members under mechanical loading and exposure to corrosion. The model captures the effect of the chain oxidation process which causes the accelerated aging of the polymer.
Reduction of Demoulding Force Through Innovative Surface Modification
Plastic parts are becoming more and more complex. Thus, the demolding of such parts is becoming more and more challenging. Meanwhile it is difficult to reproduce the conditions, appearing during the demolding of a part from a molding tool. To overcome this gap a simple and robust test setup has been developed to measure the necessary torque to demold a plastic test specimen from a defined surface of a test blank. During the test, two variables are measured and evaluated, the adhesion torque, which describes the loss of adhesion between the plastic test specimen and the metal surface of the test blank, and the sliding integral, which describes the torque needed to overcome the sliding friction between friction partner. As a result of the tests the influence of the used plastic, the influence of the process and the influence of the functionalizing of the metal surface via structuring and coating on the demolding behavior is shown.
Reinforced Thermoplastic Containing Recycled Cardboard Fibers for Recreational Vehicles Applications
Lightweight reinforced thermoplastic (LWRT) composites are ideal for the recreational vehicle (RV) industry where traditional building materials are unable to provide the performance required. The LWRT composite is more durable and can be assembled for RV exterior and interior sidewall, ceilings, and roofs of both towables and motorhomes. Due to lighter weight, LWRT-based RVs may provide opportunity for towing with smaller vehicles, can be more fuel efficient, or can carry more cargo than traditional, wood-based RVs. This paper presents the initial investigations into the properties of LWRT composite panel produced from recycled (or old) corrugated cardboard (OCC) fiber, glass fiber and thermoplastic materials using a wet-laid process. New composite systems have been obtained varying the loading levels of OCC fibers (0, 10, and 20 %) and density of the resultant composite panels. The flexural test results showed panels made from OCC fibers were 30 to 50 % stronger and stiffer in machine direction (MD) and 30 to 40 % stronger and stiffer in cross-machine direction (CD) than the control composite material without OCC fibers. The sound absorption properties of the composite panels containing OCC fibers depend on the loadings of OCC fibers and the density of the panel, and 20 % OCC fiber-based composite showed best sound absorption results. The addition of OCC fiber resulted in a smoother surface and better aqueous glue compatibility than the control composite material. In addition, the flame retardancy results showed the addition of OCC fibers decreased the flame spreadability (FSI = 30) according to ASTM E84 standard. The results suggested that sustainable fibers could be used to produce strong and stiff composite panels with significantly lighter weight.
Reliability Evaluation of Conductive Tracks Integrated Into Additively Manufactured Components
The use of 3D printing technologies enhanced with component placement and electrical interconnect deposition can provide structural electronic systems with higher fabrication freedom. Thermosetting resins that are used as adhesives in electronic packaging processes have the potential to fulfill new requirements coming from this application. Their use as building and conductive materials in additive manufacturing can lead to advantages, especially when selecting the same chemical basis. In this work, an extrusion-based additive manufacturing process was used to process the adhesives. A basic concept is introduced how the integration of electrical components and conductive tracks can be realized with this process-material combination and experimental work on two-dimensional tracks is presented. The developed process and the material selection for 2D-tracks was evaluated electrically as well as mechanically and was supported by highly accelerated life tests to ensure reliable performance. Different aspects of the integration were covered with three experiments that provide an understanding of properties of conductive adhesives printed as a tracks as well as their contacting behavior on SMD components. First design rules are derived from these experiments that can serve as a first step for developing processes for three-dimensional tracks and the procedure of contacting a component within the printing process.
Screw Design for Ultra-High-Speed, Quad-Screw Extrusion
The effect of screw programming on the performance of an ultra-high-speed, 15 mm quad-screw extruder was investigated by processing low-density polyethylene with four screw programs, no active barrel cooling (to evaluate viscous dissipation), and screw speeds of 500-2000 rpm. Observations indicated that kneading blocks were needed for timely melting of polymer pellets. Large increases in barrel temperature occurred with mixing, rather than melting, kneading blocks. Kneading block design had limited effects on power consumption but significantly affected residence time, melt temperature, and drive torque. All designs produced significant reductions in the viscosity of the extrudate, which previously has improved mixing.
Ship Less Air –Flexible Chip Bag Filling Simulation for Sustainability
The snack flexible packages on the market today, such as potato chips, pita chips, taco chips, tortilla chips, etc., are typically sold by weight, that is, the packages need to fulfill the label claims by weight. However, the size of the packages is determined by the overall volume of the products. The determination of the overall volume of a given product weight is not trivial. The volume is a function of chip broken rate, chip size distribution profile, bag width, bag film gage and material, production line speed (bag/minute), VFFS machine type, etc. Traditionally, the size of the bag is determined by trial & error process through iterative lab testing and production trials. This approach typically results in unnecessary large bags due to the concerns of sealing contamination induced leakage issues in the case of the bag being too small. This leads to significant sustainability issues in shipping and distribution since the shipping trucks are often cubed out by volume (not by weight) for chip/snack packages. The energy is wasted by shipping more air (thus, less chip/snack packages) during distribution. In this work, authors propose a novel approach of bag size determination by using a virtual simulation of the VFFS chip filling process, where the potential influential attributes, such as chip broken rate, chip size distribution profile, bag width, bag film gage and material, production line speed (bag/minute), and VFFS machine type, can be modeled and their impact on the bag size can be quantified. A progressive 3-case simulation is performed and presented in this paper. The results are directionally correct based on the authors’ observation and past experience. Currently, authors are looking for industry partners (brand owners, co-packers and machine manufacturers) to collect production data and validate the analysis model. The intent of this paper is to bring the awareness of applicability of the simulation technology regarding to the bag size determination and chip/snack filling process, and ultimately help the industry in adopting the technology to make the chip bag filling process more sustainable, i.e., to ship less air.
Simulation of a Saxton-Mixer in High-Performance Extruders Using the Immersed Boundary Method
The Immersed Boundary Surface Method(IBS)is a novel and very promising implementation of the Immersed Boundary Method (IBM) for modeling complex, moving processes. In order to validate IBS for the first time in plastics processing, this paper deals with the numerical simulation of a Saxton-mixer in foam-extend (release of OpenFOAM)as a complex application geometry.The Saxton-mixer  is well suited for validation because it canstillbe solved using traditional simulationmethods, but is alreadycomplex enough to test andvalidate IBS within a real-worldprocessing environment. For this purpose, body-fitted andIBS simulations are performedin the same wayand their results compared. In addition, the mixing zone is also investigated experimentally in order to evaluate the model qualityof the simulations.The results of both simulation methods are consistent and differ only slightly. Thus, the implementation of IBS is valid. Furthermore, a comparison of the simulation model with experimentsreveals asignificant influence of the rheological flow model. The results of thenon-Newtonian IBS modelare already approaching the experiments well and are therefore promising results for further applicationsof IBSin plastics processing.
Simulation of Structure Development During Isothermal Crystallization of Semi-Crystalline Polymers
Structures evolve at different scales when semi-crystalline polymers crystallize from the melt. During crystallization from a viscous melt or solution with moderate undercooling, the polymer forms lamellae by chain folding at the nanometer scale. These lamellae grow predominantly in radial direction and branch irregularly by non-crystallographic branching. By this, spherulites are formed at the micrometer scale. In this contribution, a simulation model for isothermal crystallization of semi-crystalline polymers is presented. For the simulation the polymer chains are divided into four different categories according to their mobility. In order to use a cellular automaton, different rules for diffusion and conversion are defined for the four categories. These rules cover the physical processes the chains experience during crystallization. With this simulation model, the crystallization of the polymer to a spherulite is simulated and compared to experimental results.
Studies of Material Properties of Htpb- Based Composite Under Aging Conditions
Hydroxyl-terminated polybutadiene (HTPB)-based rubber composite is usually used for solid propellant binder. In order to investigate the long-term material properties in the storage environment, it is recommended to set up the conditions refer to MIL-STD-810G. After aged for 100, 200, 300 hours with different temperature and humidity conditions, the key properties, i.e. tensile test, Fourier transform infrared spectroscopy (FTIR), and surface morphologies were examined. Also, by using these experimental data, diffusion model using finite element method suggested. This study will be useful for the life evaluation of HTPB-based composites considering diffusion.
Study On The Properties Of Microcellular Injection Molded Polyolefin/Polycaprolactone Composites
This study investigated the effects of polycaprolactone(PCL) loading on the morphology, tensile strength, and thermal properties of foamed injection molded PP and PPgMA composites. PCL is one of the biodegradable materials and can be used in heavy metal removal study. Results showed that PCL could increase tensile strength on PP but only small amount of it could enhance the tensile strength on PPgMA. PCL could affect the crystallization temperature and glass transition temperature both on PP and PPgMA. Storage modulus was enhanced by addition of PCL into PP and PPgMA.
Submicron Texturing of Injection Molds Using Femtosecond Laser
In injection molding, part thickness reduction is the main leverage to decrease process cost and material consumption. However, low thickness cavities require high pressure to be replicated. Controlling the surface properties of the mold/polymer interface can be a solution for drag reduction. Conventional micro- and nano-texturing technologies requires clean room environment, high-cost equipment, and are based on time-consuming multi-step processes. In this work, we presented a novel approach to sub-micron texturing of steel injection molds using femtosecond laser. A high-frequency and high-energy laser source is used to create regular and homogeneous ripples. The effect of these structures on the injection molding process are here discussed, showing how texturing can be used to reduce the injection pressure and promote wall slip.
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