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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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.
Superhydrophobic Coatings for Encapsulation of Flexible Hybrid Electronics
Recent advances in encapsulation process of Flexible Hybrid Electronics (FHE) provide routes to enormous application in advanced healthcare, smart layer based integrated sensor network, and digital microcontroller circuits. Stretchable/flexible encapsulation for advanced FHE devices requires new material sets and processes to ensure physical protection of any microchips in the FHE devices. Innovation in this research is creating a superhydrophobic coating that is spray coated and slot die coated on the FHE as an encapsulation process. The superhydrophobic coating is based on a cellulose acetate resin with hydrophobic silica nanoparticles and plasticizers incorporated. Here, two critical aspects are under examination; the content of plasticizer which is determined by glass transition temperature, migration and durability, and the hydrophobic silica nanoparticles which is determined by surface energy and durability. Both aspects are optimized and evaluated. Optimization of Spraying technique and its requirements is also under examination.
Surface Modifications of Cellulose Nanocrystals by Grafting Polylactic Acid via Polymerization—From Technique
Cellulose nanocrystals (CNCs) have drawn significant attention in recent years owing to their specific strength, renewability, widespread availability and relatively low cost. As a result, they have gained scientific and commercial interest and are currently produced at a pilot scale in many jurisdictions for several polymer composite applications. However, their poor dispersion in typically non-polar polymer resins limits the translation of their exceptional nanoscale properties to the macroscale. In this paper,we presenteda method for the surface modification of CNC by grafting polylactic acid(PLA) onto CNCs. The dispersibility of the native and surface modified CNCs(SMCNC)in rubber latex is compared and reported here. SMCNC showed a very good dispersibility in both water and chloroprene rubber(CR)which make it a good candidate for latex composite applications.
The Advanced Study of Hybrid Molding by CAE Simulation
Hybrid Molding is an emerging molding technology that is used in composite products. It has integrated molding characteristics, which can integrate multi-step process, save cost, reduce cycle time and make the product multifunctional. However, it is very hard to know what happened between composite sheet and melt during the process. In this study, we try to use CAE software to simulate the hybrid molding process. From the analysis results, it is possible to know the temperature change of composite sheet at any time and any place during the hybrid molding process, thereby helping to optimize the process and avoid possible problems.
The Challenge of Simulation For Ear-Flow Phenomenon In Injection-Mold Filling
Plastics applications are found in almost all areas of everyday living due to their versatility with an economically attractive choice in the manufacturing industry. Injection molding is the most common manufacturing process for producing plastic parts. However, there is a long-running problem requiring an urgent solution for the industry: to date, prior state-of-the-art predictive engineering tools have always provided unsatisfactory results regarding “so-called Ear-flow”, in which the advance of the flow front in the centre of the cavity is obviously slower than at the edges. Thus, the primary objective of this work is to simulate a reliable Ear-flow for neat polycarbonate (PC) material in injection molded disk via a new Moldex3D Flow solver coupled with the viscoelastic constitutive equation [U.S. Patent Pending in USPTO with Application No. 62/886,539 (2019)].
The Complexity of Service Life Prediction For Polyolefins In Chlorinated Disinfectants
Despite much effort, it is still very difficult to predict the service life of polyolefins when used in contact with the chlorinated disinfectants; chlorine, chlorine dioxide and chloramines. The actual degradation mechanism, both for the degradation of the additives and the subsequent, or in some cases parallel, degradation of the polymer, is still under debate. Also, it is not really that well known if chemical or physical properties are the most decisive in improved resistance to disinfectants. How much effect will the morphology, number and lengths of side chains, creep resistance, density, crystallinity, type and amount of stabilizer, number of tertiary hydrogens, double bonds, processing quality, solubility and diffusion rate of stabilizers, disinfectant and oxygen etc play? Since it is very difficult to change just one parameter at the time, this is quite difficult to investigate. For hot water pipes the aim is to have at least 50 years’ service life. Today the ASTM F2023 is used to test if a material will achieve this service life or not. Even if this testing is quite time consuming, with exposure times at the lowest temperature up to two years, or even longer, its validity to really predict the service life is quite questionable. The ASTM F2023 method is a pipe and materials test not a systems test and discards failures at fittings, while in fact this is often where the failure in service appears. In recent years a number of papers and presentations have been made presenting alternative accelerated testing methods and possible degradation mechanisms but very little can be found in the literature on investigations of pipes taken out of service and the correlation between the accelerated ageing with actual failures. This paper aims at describing the complexity in accelerated ageing and service life predictions of polyolefins in chlorinated disinfectants.
The Effect of Argon Plasma Irradiation On 3D Scaffolds For Bone Tissue Engineering
Tissue engineering using 3D scaffolds is an alternative to bone repair techniques that are currently used, such as autografts or allografts for bone non-union. Plasma irradiation is used as a sterilization method and can alter the surface topography of the scaffolds. We have prepared 3D scaffolds composed of poly(lactic-co-glycolic)acid (PLGA) and nanohydroxyapatite (nHA) using thermally– induced phase separation (TIPS) and 3D-plotting (3DP) techniques. We have also performed experiments to study murine stem cell adhesion to scaffolds that have been plasma irradiated. The scaffolds that were plasma irradiated with argon gas had ~140% more cell adhesion compared to untreated scaffolds.
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