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.
Failure behavior of polypropylene block copolymer welded joints was investigated. Double V welded joints were performed using an automated hot gas welding machine, which is able to independently control welding parameters leading to reproducible welded joints. Uniaxial tensile tests and fracture mechanics experiments were carried out. From these results and complementary FEM analysis, the quality of welding rods and welding interfaces were assessed. By using different specimen configurations and optical microscopy the damage zones generated during mechanical solicitation of the joints were investigated. Welded joints coming up from three hot gas temperatures in the range of 230 to 260°C were analyzed.
REACH-RS (Research & Education Academy for Coaching/Mentoring High School – Rising Stars) introduces K-12 participants to the needs for enhanced inter-personal skills and technical proficiency in the areas of nanomaterials, multifunctional materials and processing through a series of in-lab assignments. In this project, a group of K-12 students in collaboration with PSU undergraduates injection molded blends of HDPE and carbon black, and tested the resultant ASTM-type, test bars for electrical conductivity, flammability resistance and mechanical properties. The generated stress-strain, electrical and flammability data were analyzed, and correlated to electromagnetic interference (EMI/RFI) applications.
In the present study morphology and properties of partly shrunk linear low density polyethylene (LLDPE) biaxially oriented films were studied. It is shown that the mechanical properties of the films as function of the thermal shrinkage behave differently in machine (MD) and transverse (TD) directions. A correlation between mechanical properties and orientation factors determined by Fourier Transform Infra-Red spectroscopy (FTIR) was found. On the basis of the thermal shrinkage behavior of the films as a function of temperature, the molecular orientation during double bubble process was explained in term of superposition of different orientation stages.
The electrically conductive acrylonitrile butadiene rubbers (NBR) containing a carbon black as a conductive additive were prepared to investigate electrical and mechanical properties in this study. We considered the effects of conductive carbon black loading and various temperatures on conductivity, acrylonitrile contents, crosslinking density of vulcanizates, and the existence of a plasticizer. The change in electrical conductivity with different amounts of carbon black of NBRs showed that there is a certain critical point which produces a significant decrease in electrical resistivity (increase in conductivity). The mechanical properties like tensile strength, elongation to break, and surface hardness of vulcanized NBRs were determined. We found that the percolation threshold region was 5 phr CB in the NBR/CB composites. It means that there are formed continuous electrical paths which are attributed conductive carbon black in the NBR/CB vulcanizates.
This paper investigates the effect of electron beam radiation on the through thickness molecular weight profile of a bioresorbable polymer. Stacks of thin layers of two bioresorbable polymers were irradiated and the molecular weight of each layer determined. Experiments were carried out to determine the reduction in mass of each layer over time. It was found that there was a clear decrease in molecular weight in the layers nearest the beam, resulting in faster degradation.
Recyclable high-melt-strength (HMS) PP has been introduced as an alternative choice to replace crosslinked material in a tandem foaming extrusion process. A filamentary die was selected to promote the optimum processing condition. The cell nucleation and volume expansion behaviors have been investigated as a function of the aspects of die temperature, CO2 content, and talc content. The results exhibited a significant relationship between the processing parameters and foaming behaviors. Low density (i.e., 12~14 fold), fine-celled (i.e., 107-109 cells/cm3) PP foams were successfully produced using a small amount of talc (i.e., 0.8 wt%) and 5 wt% CO2.
Polymer processing and converting operations, whether they relate to extrusion coating, blown film extrusion, producing sheets for thermoforming or manufacturing finished articles by injection molding, generally involve some amount of resin waste. A total conversion of the resin into an article of desired quality is an exception rather than a rule.As material costs constitute the bulk of the total costs associated with any product, the aim should be to keep the resin waste as low as possible. With the quality of the product depending largely on the machine and processing parameters, one of the easiest and most effective methods of reducing polymer waste is to optimize the design of the converting machinery at the design stage before they are built as well as optimization of processing conditions.With the illustration of several examples representative of blown film extrusion, flat film extrusion, extrusion coating, blow molding and pelletization process, this paper demonstrates how by applying this strategy resin waste could be reduced.
In assembly processes, occasionally a plastic component mysteriously" breaks at a rate of two percent or less. Successful diagnosis of this type of low rate breakage depends on not only skillful laboratory work but also careful observation of failed samples. In addition it is useful to observe and understand the relevant assembly process because the interaction between the plastic component in question and surrounding components may be the key factor in its breakage. Solution to this type of low rate breakage typically starts with identification of the crack initiation site. Examples of the diagnosis and verification of low rate plastic component breakage are given in this paper."
Crack initiation in pipe grade polyethylene is studied using a circular notch specimen (CNS) under constant load. The specimen geometry and loading conditions are selected in a way that the crack becomes unstable and leads to almost instant fracture after initiation. Therefore the time of crack initiation practically coincides with easily recorded time to failure. The crack initiation takes place within a process zone (PZ) coplanar with the notch and extending from the front of the notch. Two sub-zones are distinguished within PZ. The first, located in the frontal part of PZ comprises of a planar set of micro cavities within a thin strip of material coplanar with the notch. The second, constituting the rest of PZ, consists of micro fibers and membranes resulting from cold drawing of the material between the cavities. With time creep & degradation of micro fibers and membranes leads to crack initiation. Results of experimental observation and an approach to modeling of crack initiation in CNS are reported.
Polyesters are widely used in automotive and electrical industry parts due to their excellent electrical, mechanical and molding properties. However, as the industry is driving/evolving towards miniaturization of parts it is a challenge to develop polyester compositions with high flow properties in order to fill the thin wall molds/parts. Furthermore, flow improvement is more challenging in filled polyester compositions as these have substantially higher viscosity than corresponding neat polyesters. Polyester modification in compounding, molding, and extrusion stage is an easy, economically viable and flexible route than corresponding modification in reactor stage. In the present study, we discuss the development of new high flow polyester compositions using extrusion process and flow additives. The correlation between standard viscosity measurements and molding properties in thin wall molds is also discussed.
This study investigates the effect of localized final molecular orientation and anisotropy on mechanical part properties with melt manipulation during polymer processing. The localized final molecular orientation and morphology are indicative of the resultant product response and typically resulted in improved mechanical properties with an increase in tensile strength for the material investigated, polystyrene. In general, specimens with high levels of retardation distributed more uniformly along the gage length exhibited higher tensile strengths. he specimens tested in tension tended to fail in the gage section end opposite the gate with the lowest molecular orientation. To elicit the ultimate tensile strength of the higher oriented sections, miniature specimens were machined from molded specimens of varying molecular weight uniformly along the gage length and tested. This paper discusses the results of the investigation along with future directions of study.
In this work, we started the preparation of multiwalled carbon nanotubes (MWNTs) by the CVD method. Following surface modifications, MWNTs were grafted with poly(L-lactide) to obtain poly(L-lactide)-grafted MWNTs (or MWNTs-g-PLLA). Prior to investigation on whether the MWNTs-g-PLLA could be an effective reinforcement for the semicrystalline, biocompatible and biodegradable PLLA, we investigated the effects of MWNTs on the crystallization of PLLA in the nanocomposites (PLLA/MWNTs-g-PLLA) using differential scanning calorimetry (DSC). The MWNTs was found to significantly enhance the crystallization of PLLA.
Research work using the Distinct Element Method (DEM) has identified the potential of a discrete approach for more accurately modeling the motion of plastics solids within a single-screw extruder. Experiments of HDPE particles contacting a steel anvil showed a velocity dependency in their impact behavior, which becomes an important consideration when selecting an appropriate force-displacement model for DEM simulations. In addition, Experimental trials have been conducted to examine the bulk motion of solids within an actual single-screw extruder at different screw speeds and barrel temperatures. The implications of velocity-dependency in the contact-displacement models were subsequently examined in 3-D, non-isothermal DEM simulations of the solids-inflow and solids-conveying zones of a single-screw extruder.
This study will show the effects of mold closing speed and position on the pinch-off strength of an extrusion blow molded bottle. It is important to have an optimal mold closing speed and position so the pinch-off strength is most advantageous to the part integrity. Today, the industry uses past knowledge to process the pinch-off strength. The study will add more scientific knowledge to the industry and improve overall pinch-off strengths. This is needed because simply relying on past experience may not help in new and more difficult situations. Data acquired from the study will give the necessary results to optimize the mold closing speed, position, and pinch-off strength on an extrusion blow molded bottle.It was found that the slower mold closing speed and larger mold closing position created the greatest pinch-off strength and thickness.
Specifying and installing the proper equipment for a process is key to minimizing the long-term cost of producing products. But often the objective to purchasing equipment is to minimize the initial capital cost. Minimizing this initial purchase cost, however, may require the purchaser to add costly modifications to the line after installation, creating higher operating costs, length troubleshooting, and a delay to market entry. Principals and strategies are presented here that show how to avoid this mistake, and case studies are provided as learning tools.
The current work demonstrates a novel automatic approach for the die balancing process. The algorithm involves flow simulation through computational fluid dynamics (CFD) and shape change via automatic shape deformation (ASD) to minimize the flow non-uniformity at the die exit. Taking a spiral mandrel die as an example, the combined use of ASD with CFD is highlighted. Using this approach, one baseline simulation was manually set up and two more simulations were automatically created study the effects of helical angle. In the example studied, it was found that changing the helical angle from 315° to 405° had a minor effect on the flow uniformity.
Back-propagation artificial neural network (ANN) models were constructed to predict the microstructure and mechanical properties of the microcellular injection molded polyamide nanocomposites. Key parameters that affect the evolution of the microstructure, i.e. supercritical content, melt temperature, shot size, melt plastication pressures and injection speed are selected as the artificial neural network inputs, and the outputs are the microstructure defined as the cell size, Weight reduction, and mechanical properties . The results revealed that ANN model offer a favorable method in the optimum design of the nanocomposites and process improvement. This work enhances the systematic understanding of parameters in the optimum design of the nanocomposites and process improvement.
In the context of lightweight construction and miniaturization, especially in the automotive industry, direct encapsulation of electrical components in injection molded parts gains further in importance. In particular with regard to the processing of temperature sensitive semiconductor devices specific knowledge on the thermal load is required for product-life estimation. In consequence of its mounting points and mass-to-melt-ratio, standard temperature probes are suitable only to a limited extent for this kind of measurement.As this paper shows, semiconductor diodes are well capable of measuring the time-dependent temperature inside an injection molding tool because of their electrothermal properties. During the investigation probes with an edge length less than 200 ?m have been mounted in the cavity of the tool. Due to the low heat capacity of the probe the temperature of the melt is unaffected by its presence and the thermal signal is registered with almost no delay. Using the method presented, the thermal load of directly encapsulated electrical devices can be measured. In particular the thermal degradation of semiconductors can be estimated.
A novel analytical computational model was developed to predict Top Load and Side Load performance of light weighted water bottle containers. This approach involves, simulating reheat stretch blow molding of PET containers using Virtual Prototyping™ software to predict the material thickness distribution of the blow molded container and associated mechanical properties derived from estimating the degree of stretch and orientation of different sections of the container. These parameters serve as inputs for Finite Element Analysis involving highly non-linear deformation of the containers under various types of loading. A predictive curve was established to determine the degree of light weighting that can be achieved for a 500mL water bottle by plotting the Top Load Strength as a function of container Sidewall Thickness. The Top Load performance for an empty 14g container was predicted to be about 47 N (10.5 lbs) compared to 86 N (19 lbs) for a 17g bottle and 61 N (14 lbs) for 15g bottle. This analysis has been proven to be effective and accurate for performance analysis without expensive prototyping of the container design and allows a wider number of sample designs and light-weighting options to be explored in a limited amount of time.
This paper investigates the effect of three screw geometries on the extrusion characteristics of 0%, 25%, 36% and 50% wood-filled HDPE blends in a single screw extruder. From the three screw geometries, the effects of feed depths, the compression ratios, and the metering depths were compared. The characteristics included output, pressures and melting profiles. It was found that, due to its partially filled phenomenon, the solid conveying section dominates the extrusion behaviour of the wood-filled resins. A modified solid conveying model based on viscosity was presented, and the solid conveying angles calculated.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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