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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Unique Crystallization Behavior of ?-Polypropylenes
The work deals with the effects of ?-nucleation and thermal conditions on crystallization and resulting supermolecular structure of isotactic polypropylene (iPP). Neat and ?-nucleated iPP were crystallized under various conditions. Strong interrelation between crystallization temperature (Tc) and ?-phase formation was found. Moreover, the content of ?-phase was specifically affected by the nucleator concentration - increasing Tc depressed the formation of ?-phase in samples containing higher amount of the nucleator while this effect was inverse when low-nucleated samples crystallized.
Processing of Antimicrobial Nanocomposites and Their Characterization
The volume of antimicrobial plastic materials in the healthcare and the food industry sector is growing rapidly. Different approaches to achieve antibacterial effects are followed. The technology discussed in this article is based on silver ion release.To obtain such antimicrobial nanocomposites, thermoplastic materials were processed with Agnanoparticles on TiO2 particles as carrier substance in a co-rotating twin screw extruder. Process parameters and the kind and amount of nanoparticles were changed to characterize their effect on the morphology, antibacterial and different mechanical properties using TEM, DSC, and tensile tests. In this work, the relation between these properties, the process parameters and the concentration of additives is presented. The processes of compounding and subsequently injection molding were optimized to get a plastic material with added value.
Clearweld™ Resins: Alternative Options for TTIR Clearwelds
Clearweld is a through-transmission laser welding process promoted for the ability to generate colorless welds. A colorless weld is generated by applying the absorbing material only at the weld interface. The coating may be applied by a liquid dispensing method such as spraying, microsolenoid dispensing, etc. The limitation of the coating process is the secondary step of applying the coating.Clearweld laser absorbing additives were compounded into various resins to be used as the bottom substrate in a weld configuration. The resins eliminate the need for the dispensing step. The laser absorbing additive has minimal affect on the coloration of the part, which allows for a broad selection of colors, both transparent or opaque. The resin is typically injection molded but may also be extruded into a film for insert molding. This paper presents results of compounding the Clearweld additive into various polymers, including but not limited to Acrylic, polycarbonate, and polypropylene.
Poly (Ethylene Terephthalate) -Organoclay- Impact Modifier Nanocomposites
This study was conducted to investigate the effects of component concentrations and addition order of the components, on the final properties of ternary nanocomposites composed of poly (ethylene terephthalate), organoclay, and an ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) terpolymer acting as an impact modifier for PET. Among the investigated addition orders, the best sequence of component addition (PI-C i.e. PET, Impact Modifier-Clay) was the one in which poly (ethylene terephthalate) was first compounded with E- MAGMA; later, this mixture was compounded with the organoclay in the subsequent run.
Study on the Mechanical Properties of Microcellular Injection Molded Parts
There are several benefits of using the supercritical fluid microcellular injection molding process. The weight of the parts, process conditions (material temperature, viscosity, and clamp force), shrink/warpage, dimensional instability, and cooling/cycle time are all reduced. This process is made by introducing the controlled gas during the injection stage cycle to create millions of micron-sized voids in otherwise solid thermoplastic polymer parts. The purpose of this study is to study the effects of process conditions on mechanical properties by microcellular injection molding. The weight variation was reduced by as much as 40%. This process reduced the melt temperature by about 20-30°C and also reduced the cycle time by about 5-15 s. The higher injection speed resulted in better cell structure. In addition, the supercritical fluid microcellular process did not reduce the tensile strength of the material, but the impact strength was increased by four times.
Modeling the Effects of Solid State Orientation on Blown High Molecular Weight High Density Polyethylene Films: A Composite Theory Approach
High molecular weight high-density polyethylenes (HMWHDPE) are unique, in that they can be uniformly oriented to high draw ratios to produce films with significantly enhanced physical properties. Such improvements are the result of the transformation of isotropic piles of lamellae into rigid, long, fibrous microstructures, which can be characterized by various analytical techniques. This work represents the first industrially usable approach to the prediction of mechanical properties in oriented polyolefin films and may have wider application to other fiber-like microstructure forming polymers. The model presented is tied both to the observed structural features, as well as to properties that are routinely measured in the industrial setting. These enhanced films create new opportunities for flexible packaging in high strength and stiffness applications.
Polydimethylsiloxane Polyurethane Modified Epoxy as Precursor for Manufacturing Carbon / Carbon Composites
The objectives of this study are to investigate the feasibility of utilizing the aromatic amine-terminated polydimethylsiloxane polyurethane modified novolac type epoxy to prepare carbon/carbon(C/C) composite. The compatibility of polymer blend and curing kinetic of modified epoxy were investigated. Thermal, physical and mechanical properties changes during the post-cure stage and carbonization processing are also examined.Results show that the polydimethylsiloxane polyurethane is compatible with epoxy resin when the content is below 5 phr (parts per one hundred parts of epoxy resin). The curing kinetic study show that epoxy matrix modified with polydimethylsiloxane polyurethane decrease the collision factor and increase total heat of reaction and the active energy of reaction. The polydimethylsiloxane polyurethane increases the mechanical properties after carbonization since polydimethylsiloxane polyurethane releasing the internal pressure and protecting the fiber surface during carbonization process. The Novolac Epoxy with polydimethylsiloxane polyurethane modified has better oxygen resistance and lower oxidation rate from the TGA oxidation testing results.
Welding Thermoplastic Foams
Foamed thermoplastics display economical potentials due to the material saving and reduced cycle time during the injection molding process. At present neither knowledge of the applicability of different welding methods exists, nor the process parameters to gain the optimum weld quality are known. In this paper an experimental study will be presented to analyze the effects of the process parameters on the attainable strength using the heated tool welding and vibration welding. Via three-dimensional experimental design all process-relevant parameters have been varied including the material density. It was found that the process parameters have a considerable influence on the weld results. Differences in terms of weld strength between the particularly small pores and large pores were found. Comparing to bulk material a major reduction of the cycle time has been observed. Connections between the melting characteristic and the process parameters were deduced.
CDs and Interactive Programs in Plastics Engineering Education
We have developed CDs1,2 and interactive programs that are being used in both polymer science and plastics engineering courses. These CDs contain various interactive programs and numerous animations. These materials can be used as self- learning tools with the aid of workbooks. Initial evaluation has been very positive with a high level of acceptance and use by students. The plastics industry is now the fourth largest manufacturing industry in the United States, accounting for $330 billion in annual shipments and directly employing more than 1.5 million people. A key to this industry remaining competitive with countries where workers are paid a fraction of U.S. wages is a skilled, educated, and flexible workforce. Over the course of the past five years, we have been working to address the need for technical personnel in this field through NSF funded projects whose goals have been the development of new and innovative educational materials and the dissemination and evaluation of this material.
Fibre Orientation Measurement and Prediction within Gates and Ribs of Injection Moulded Parts
Within this paper we discuss the effects of gating systems and ribs on the fibre orientation of injection moulded parts. Three-dimensional analyses were performed using the Moldflow MPI 5.0 commercial software with predicted fibre orientations compared to experimental measurements made at the University of Leeds. For many years thermoplastics have been extensively used in a wide variety of applications due to their relatively cheap cost and high processability, particularly by injection moulding. However, commodity polymers such as polypropylene and Nylon have relatively poor mechanical properties, which limits their use to non-structural applications. The use of short glass fibre reinforcement is a well-established means of significantly improving mechanical performance without compromising processability.
The Effect of Volume Fraction and Particle Size of Polystyrene onto Magneto-Rheological Properties of Inverse Ferrofluid
Inverse ferrofluids are prepared using microsized polystyrene particles dispersed in a ferrofluid. The magnetorheological properties were measured as a function of the particle size, and polydispersity. The measurements are performed in a plate-plate rheometer applying a vertically oriented magnetic field. The obtained flow curves show, that under shear a ”solid” to “liquid” transition take place, which is presumable due to the destruction of chains of the non-magnetic particles. This transition is characterized by an apparent yield stress and compared with theoretical predictions. In the oscillatory mode, the storage and loss moduli reveal, that also the viscoelastic behavior is affected by the particle size and the particle size distribution of the non-magnetic particles in inverse ferrofluids.
Enhanced TPO Thermoforming Using High Melt Strength Polyolefin Elastomers
Hard TPOs have grown rapidly in the automotive industry due to their favorable cost/performance characteristics and injection molding processability. Other plastics processes are now either currently used or under investigation. Processes such as blow molding and thermoforming offer the potential to manufacture large parts with much lower tooling costs than injection molding. However, it is well known that conventional polypropylene exhibits poor melt strength. This deficiency has limited its use in either large part extrusion blow molding or thermoforming.Recently, polypropylene producers have introduced high melt strength polypropylene into the market. These polypropylenes have much higher melt strength than conventional materials. They are being promoted for use in hard thermoplastic olefin (TPO) applications requiring high melt strength.However, other components, particularly the impact modifier, can now play an important role in the thermoforming characteristics of hard TPO compounds. In a series of experiments, significant changes in TPO rheology were observed, depending on the level and type of impact modifier used. The characteristics of ethylene/alpha olefin copolymer impact modifiers and their effect on hard TPO thermoforming performance will be discussed.
Morphological and Electrical Properties of the Adhesive for Lithium Ion Battery
This research intends to investigate the utilization of porous polymer for Li-ion second battery. The phase separation method was used to control the porous condition. Various solvents were used to generate phase separation when epoxy resin was cured. The void distribution of porous polymer was observed by scanning electron microscope (SEM). Furthermore, the porous adhesive was applied to the Li-ion battery. The effects of adhesive on the capacity and the cycle life of Li-ion battery were investigated.Results showed that the porous epoxy adhesive did not change the electrochemical reaction of electrode. The battery properties, such as the capacity, cycle life and the 1st irrev % are significantly affected by the porous adhesive. The ratio of discharge to charge was over 90% in the coin-cell test. The capacity of battery decreased slightly (about 6.91%(23mAh/g)) as the coating area of adhesive reached 20%(1cm2). The real battery cycle life is more than 85% after 250 times test, which meets with the standards of the commercial grade.
A Comparison of Process Configurations for Compounding Woodfiber-Plastic Composites
The market for woodfiber-plastic composites is growing at an astounding rate. Subsequently, numerous machinery manufacturers and individual processors have been scrambling to develop unique methods for continuously mixing, devolatilizing, and extruding these materials, in an attempt to increase manufacturing efficiency and to optimize finished products properties.A wide variety of devices, including parallel twin screw extruders (co- and counter-rotating), conical twin screw extruders, continuous mixers, batch mixers, and even single screw extruders are being used for compounding woodfiber-plastic composites. This paper will identify those devices, and the various process configurations currently being utilized in the manufacture of woodfiber-plastic composites. In commodity thermoplastic operations, these mixing devices have traditionally produced intermediate pellets, which are then processed in a separate operation on single screw extruders to make an extruded part. With woodfiberplastic composites, however, the trend (although not the rule) is to bypass the pelletizing step and to combine compounding/devolatilizing with direct sheet or profile extrusion.
Evaluation of Classical Nucleation Theory Using Visualization Data
Numerical modeling of the microcellular polymeric foaming process often employs the classical nucleation theory. Although many previous theoretical studies of cell nucleation and cell growth have attempted to verify the theoretical models through experimental observations, most studies have been limited to the comparison of simulation results with the final cellular structures after the foams were stabilized. In this work, visualization data obtained by Guo et al  for the in situ foaming processes was utilized to evaluate the theoretical model for the polymeric foaming process based on the classical nucleation theory. Unintentional heterogeneous nucleation and nucleus-size dependent surface tension were discussed to narrow the gap between theoretical and experimental results. Simulation results indicated that contact angle and surface tension had significant effects on the final foam structures.
Heated Die Energy Saving Enhancement through Thermoset Polyester Mold Insulation
The energy consumption of a heated die can be significantly decreased by using mold insulation. Two different types of insulation applications will be evaluated to determine the significance of the energy savings by insulating the shear bars and platens as opposed to just the platens in a compression molding process. The applications being compared are, mold platen insulation versus mold platen and shear bar insulation. The most productive application will also be established in order to maximize energy cost savings. The insulating media was chosen due to its low thermal conductivity and high compression strength.
Study on RTD of S Element in Co-Rotating Intermeshing Twin-Screw Extrusion
S element is a new screw element. It takes the shape of the character ‘S’ in the cross section and is always consisted of positive and negative components. In this paper, a simulation method of residence time distribution in intermeshing co-rotating twin-screw extrusion was put forward. According to the velocity profiles simulated and the marker particle tracking method, the functions of the resident time distribution (RTD) are fit. The functions of RTD demonstrate that lognitudinal mixing ability of S is better than that of common screw elements. The theoretical RTD is agreement with the experiment results.
Shear Imbalance Effects on Gas Distribution in Gas-Assist Injection Molding
This paper presents a study about the way in which shear, developed in the perimeter of the runner, affects the distribution of gas in gas-assisted injection molding. The high shear regions created in the perimeter of the runner continues into the mold cavities. These high shear regions within the cavity create variations in the melt’s viscosity within that cavity and will control the distribution of the gas within the formed parts. This study evaluates the sensitivity of this phenomena in a variety of different plastic materials. The study further evaluates means to control the gas distribution through use of melt rotation technology.
Resistance Welding of Conductive Thermoplastic Composites
Resistance welding is a common metal joining process wherein electrical current is dissipated as heat as it passes through a high resistance boundary between mating parts. This process can also be used with thermoplastic composites rendered electrically conductive by the addition of carbon reinforcement. In this study, two conductive thermoplastic composite plates were resistance welded without external electric heating elements to form a complex box-like structure. The influence of welding conditions on mechanical and physical properties of the assembly was studied. Weld strength and meltdown were strongly dependent on the welding current, and pressure. A minimum energy, equal to the product of current, pressure-induced contact resistance and welding time, was required for meltdown. It was also observed that, regardless of the current, a critical pressure must be applied to achieve acceptable mechanical properties.
Modification of Physical and Chemical Properties of Polyethylene Resins through Electron Beam or Gamma Irradiation
Polyethylene resins have been modified with electron beam or gamma radiation to adjust some of their physical and chemical characteristics before their conversion into formed parts, with positive impact on the properties of end products produced from these resins. This paper provides results from characterization studies which give evidence of structural changes, including long-chain branching and oxidation, from the modification of certain polyethylene resins, as well as data on important property enhancements in extruded, injection molded and blown film end products produced from these resins. The property enhancements allow the material to be more competitive with other resins and offer good prospects for overall cost savings.
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