SPE Library

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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Enhanced Compost Rate With Simultaneous Toughening By Multifunctional Particle Additives In Poly(Lactic Acid)
Caroline R. Multari, Raymond A. Pearson, June 2022

A particle additive is reported that simultaneously improves ductility and biodegradation behavior of poly(lactic acid) (PLA). Our approach explores the use of encapsulation technology to create degradation-promoting additives while limiting any breakdown of the matrix during melt extrusion and service life. In addition to promoting biodegradation such encapsulated particles are designed to enhance toughness of the matrix. Such dual use particles have the potential to broaden the uses of PLA. In this work, particle properties are examined and the accompanying tensile behavior and compostability of the composite investigated. Particles were dispersed within the PLA matrix by extrusion to 3D printer filament. Elongation at break was improved over neat PLA with limited loss of yield strength. Degradation rate in compost is accelerated and decoupled from environmental conditions by embedding a degradant material into the PLA matrix itself, aided by encapsulation technology that isolates and protects the degradant. The additive has been found to improve mechanical properties while accelerating the biodegradation of parts produced by extrusion-based methods.

Characterization Of Vibration Welded Pine, Maple, And Bamboo
Curtis Covelli, Dr. David Grewell, Shichen Yuan, Klaus Schmidt-Rohr, June 2022

This study investigates the factors affecting the welding of pine, maple, and bamboo pulp-board. This research used a Branson Mini II vibration welder traditionally used for welding plastics. The effects of weld pressure, amplitude, and weld time were varied to determine their effects on lap-shear weld strength. Strength testing was performed with a universal testing machine. The morphology of the weld zone was also analyzed to gain insight into the welding mechanics. The highest strength of pine samples was 8.4 MPa, while maple was approximately 35% stronger and had a smaller standard error. It was observed that bamboo pulp board weld strength was primarily dependent on weld pressure. Also, pulp-board seemed to weld in a similar fashion to wood.

GLIM: Glas Fabric Insert Molding - Polymer Back-Injection Of Glass Fabrics To Increase Strength
Christian Rust, June 2022

Hybrid materials nowadays are achieving increasing market dominance in the technical segment due to their outstanding mechanical properties. One such hybrid material that is increasingly coming into focus, especially in mobility branch, are fiber-reinforced plastics. They offer the advantage of low weight and high strength. As a rule, generally glass or carbon fibers are embedded in the matrix material. Over the last few years, the demand for fiber-reinforced plastics has increased continuously. Considering the recent changes in the automotive industry, it is expected that this trend will not change in the near future, especially with regard to the weight reduction of means of vehicles.

Effect Of Talc And Carbodiimide On The Hydrolytic Resistance Of A Poly(L-Lactic Acid) Compound
Nishant Singh, Celina Alvarado, Carlos A. Diaz, Baxter Lansing, Christopher L. Lewis, June 2022

In this work we examine the influence of talc and a polymeric carbodiimide on the hydrolytic degradation resistance of a commercially available Poly(L-Lactic acid) PLLA. Here, polymer blends containing 0-4wt% talc, a crystal nucleating agent and 0-1 wt% of a polymeric carbodiimide (CDI), an anti-hydrolysis agent, were melt blended and compression molded into plaques. Samples were then submerged in a phosphate buffer solution (PBS) at 50°C for up to 60 days. Results indicate that the presence of talc as the sole ingredient in the formulation increases the crystallization rate and this translates to an increase in the degree of crystallinity of compression molded plaques and a modest improvement in hydrolytic degradation resistance as compared to unfilled PLLA. The presence of CDI retards PLLA crystallization. In spite of this, compounds containing CDI exhibited much greater hydrolytic degradation resistance than PLA with the effect being more pronounced with increasing CDI concentration. Under DSC conditions, the addition of 1wt% talc to CDI containing compounds improved the non-isothermal crystallization rate at 5°C/min but this effect diminished as cooling rate increased and this explains the low crystallinity of compression molded samples. However, compounds containing both talc and CDI showed an improved hydrolysis resistance as compared to compounds containing only CDI implying that talc's role in reducing the rate of hydrolysis is caused by the hydrophobic characteristic of the material. It is envisioned that this work will help pave the way for the usage of PLA in durable applications where long-term resistance to humidity is anticipated.

Effect Of Plasma Treatment On Degradation Of Biodegradable Mulch Film
Swapnil Bhattacharya, Harshal J. Kansara, Celina E. Alvarado, Carlos A. Diaz, Jeffrey Lodge, Christopher L. Lewis, June 2022

Mulch films modify soil conditions thus improving crop output, hence are widely used across the world. Traditional PE (polyethylene) films do not degrade and must be disposed of afterwards. Biodegradable mulch films (BMFs) provide a much better alternative and are meant to be tilled with the soil after harvest. But most BMFs degrade slowly and accumulate in soil, harming the soil productivity. In this investigation we evaluate the effect of gliding arc plasma treatment on the behavior of a commercially available biodegradable mulch film based on polybutylene adipate co-terephthalate (PBAT) and polylactic acid (PLA). Following plasma treatment an initial increase in the hydrophilicity of the films is observed and this is attributed to an increase in oxygen containing species on the surface. Moreover, hydrophobic recovery is slow as indicated by contact angle measurements taken over a 30-day time. Thermal analysis results indicate no significant difference indicating that treatment is confined primarily to the surface. A treated film showed enhanced disintegration as compared to an untreated film following 65 days of composting in an aerated static pile compost. These results indicate that plasma treatment may aid the biodegradation of plastic mulch films and therefore eliminate their accumulation in soil.

Investigation Of Orotic Acid Effects On The Crystallinity Development Of Poly-Lactic Acid
Faisal J. Alzahrani, Peng Gao, Alaauldeen Duhduh, John P. Coulter, June 2022

This research investigated the effect of the addition of Orotic Acid (OA) on the crystallization kinetics of Polylactic Acid (PLA) in quiescent and non-quiescent conditions. A differential scanning calorimetry (DSC) study was used to investigate and understand the effect of the addition of orotic acid on 2500 HP PLA under quiescent conditions. DSC technique was utilized to capture the crystallinity, melting point, and other thermal parameters of PLA-OA blends. Conventional injection molding (CIM) was used to investigate the influence of adding OA into PLA under non-quiescent conditions. Two concentrations of orotic acid, 0.3 wt% and 0.7wt% were mixed with neat PLA and then investigated. It was observed that the 0.3 wt.% orotic acid provided significant improvement in crystallization kinetics by increasing the crystallinity and reducing the incubation time. Both blends under quiescent conditions showed almost the same crystallinity in which the maximum crystallinity that was observed was around 63% in the blend of the PLA/0.7OA at 85°C. For 2500HP PLA, Orotic acid (OA) showed to be an effective nucleating agent. A small amount (0.3 wt%) was sufficient to achieve 61% of crystallinity in injection molding at 80°C mold temperature.

Automated Optimization Of A Block-Head-Mixer With An Innovative Algorithm
Felix Vorjohann, Lucas Schulz, Mirco Janßen, Reinhard Schiffers, June 2022

CFD-Simulations are a common tool to design and optimize mixing elements. The manual evaluation and experience-based derivation of an optimized geometry is still an iterative process which is time consuming. In this paper an automated algorithm is developed and tested for a mainly distributive Block-Head-Mixer. To automatically evaluate the flow field of each geometry variant, quality criteria are introduced which enable the assessment of the mixing capability. The investigation showed that the quality criteria are suitable to evaluate the flow field and an optimized candidate compared to a starting geometry could be found automatically.

Curing Behavior Simulator For Robotic 3D Printing Of Uvcurable Thermoset Polymers
Luke Weger, Luis Velazquez, Corina Barbalata, Debaroty Roy, Genevieve Palardy, June 2022

Robotic 3D printing systems utilizing photopolymers can enable free-standing structures, large-scale printing, extensive mobility, and increased part complexity. However, to better estimate robotic printing parameters and eliminate expensive trial-and-error approaches, a simulation framework for curing behavior is needed. In this work, an autocatalytic curing model, considering printing speed, UV light intensity, spotlight diameter, and filament thickness, was used to create a MATLAB simulation to study the effect of different printing parameters. The printed filament was discretized into a set number of elements over its length and thickness. UV light exposure time above each element was derived based on spot diameter and printing speed. This simulation framework, combined with experimental data (real-time ATR-FTIR), can better inform decisions regarding printing parameters selection. Overall, it was estimated that a speed ≤ 3 mm/s with a filament thickness ≤ 2 mm would produce acceptable ranges of degrees of cure at different UV light intensities and spot diameters. Finally, control of printing parameters (robotic arm movement and UV light intensity) to obtain a specific degree of cure (DoC) ensuring structural rigidity is demonstrated for a two-degree-of-freedom manipulator, showing both the desired endeffector position and the desired DoC are achieved in four seconds.

Injection Molidng Of Microporous Ultra-High Molecular Weight Polyethylene
Huaguang Yang, Lih-Sheng Turng, June 2022

Microporous ultra-high molecular weight polyethylene (UHMWPE) parts were produced by microcellular injection molding (MIM) technology, which enabled higher production efficiency and lower part cost compared to the traditional powder sintering method. The microstructure could be tuned by adjusting the shot size to produce either sandwiched solid-skin – porous-core – solid-skin parts or open porous parts. The pore morphology, average pore size, pore size distribution, and pore density were characterized, and the water contact angle (WCA) and degree of oil-water separation were determined. The part weight reduction of open-porous UHMWPE and sandwiched UHMWPE parts were 16.5 wt% and 11.8 wt%, respectively. The WCA results showed that the porous surface transformed molded UHMWPE samples from being hydrophilic (34.5°) to hydrophobic (124.6°). Furthermore, the open-porous structure exhibited good oil water separation capacity. Tensile tests were carried out to study the effect of morphology on the mechanical performances of the molded UHMWPE parts. The characterization shows that a possible application for the sandwiched UHMWPE parts could be as a bone replacement material because of its high mechanical performance, and an application for the open-porous UHMWPE is as a functional filter material due to the fine pore size and high pore density.

From Petroleum To Biobased Crude: A Thermoplastic Polyurethane From Lignin-Oil Without Isocyanates
James Sternberg, Srikanth Pilla, David G. Brandner, Reagan J. Dreiling, Arik Ringsby, Jacob S. Kruger, Gregg T. Beckham, June 2022

The movement to transfer from petroleum-based products and materials to renewables does not necessarily have to bypass the use of oil. A new type of “black-gold” is readily abundant from the earth’s most abundant source of aromatic carbon: lignin. While fractionation of petroleum yields fuels and chemicals for a diverse set of industries, lignin fractionation using targeted catalysts has demonstrated the ability to generate monomers and oligomers rich in functional groups for polymer synthesis. This study explores the use of lignin-oil, generated from reductive catalytic fractionation of popular wood, to a hydroxyl-rich mixture of aromatics that is used to synthesize a thermoplastic non-isocyanate polyurethane. The lignin-oil is first converted to a cyclocarbonated derivative using a benign synthetic sequence and further polymerized with a diamine to yield the non-isocyanate TPU. While more work is underway to optimize the reaction conditions and meet typical mechanical properties of commercial materials, initial analysis shows thermoplastic behavior and flexible properties consistent with traditional thermoplastic polyurethanes.

Development Of An Inline-Measurement System Of The Surface Temperature Of Square Hollow Profiles
Jonas Köllermeier, Volker Schöppner, June 2022

In polymer extrusion, the die temperature is normally set to the recommended temperature in order to reach a homogeneous melt. Nevertheless, the measurement of the melt and surface temperature of the product leaving the die is not state of the art due to the difficulty of an inline - measurement. As a consequence, the product temperature leaving the die is assumed as the set die temperature. Therefore, this article aims to engineer an inline-measurement system of the surface temperature of square hollow profiles immediately after leaving the die. First, two objective quality criteria to define the thermal melt homogeneity, named weighted melt temperature and radial temperature, are introduced. After that, experimental investigations are carried out for two different types of polyolefin polymers with the variation of several process parameters such as the screw speed and the die temperature. In order not to distort the product, the developed construction is based on a contactless measurement system using infrared pyrometers to measure the average surface temperature on each side of the profile. After all, rules of behavior are derived from the process and correlations between the investigated process parameters and the melt quality as well as the surface temperature are identified.

Deformation Mechanisms Of Toughened Poly(Lactic Acid) Using Novel Additives
Jordan Greenland, Caroline Multari, Raymond A. Pearson, June 2022

Poly(lactic acid) (PLA) is certified biodegradable under specific composting conditions, but its inherent brittleness limits usefulness in commercial applications. In this study, novel additives were supplied by TRuCapSol for twin-screw melt compounding and injection molding with general purpose PLA resin. These additives were received in powder form and investigated for their ability to improve the tensile toughness. We compared our blends to several commercially available toughened PLA blends. The inherent micro-deformations of PLA were amplified by the novel additive and resulted in improved ductility. Therefore, the potential for the development of blends that enhances the toughness and increase the rate of biodegradation of PLA has been demonstrated.

Pressure-Controlled Injection Molding Of Recycled Polyolefins
Joshua Krantz, Peng Gao, Zarek Nieduzak, Elizabeth Kazmer, Olvia Ferki, Margaret Sobkowicz-Kline, Davide Masato, June 2022

The importance of utilizing recycled materials to manufacture plastic products has been a topic of great interest due to the environmental repercussions. Processing issues arise from the usage of these resins due to the variation in their molecular weight and rheology. In this work, pressure-controlled injection molding is evaluated and compared against conventional velocity-controlled injection molding. The effects of injection velocity, mold temperature, and pressure on part shrinkage and mechanical properties of injection molded parts fabricated with post-consumer film-grade polyethylene were evaluated. The experimental results show that the different processing techniques significantly affect the mechanical properties and part shrinkage for both materials. Additionally, different levels of injection pressure and velocity significantly affect the shrinkage of the plastic parts. Moreover, it was seen that parts fabricated using pressure-controlled injection molding had preferable overall quality.

Potential Of Five-Axis Kinematic Systems For Additive Manufacturing Using Fused Deposition Modelling (FDM)
Joshua Voll, Jonathan Baier, Rene Brunotte, Stefan Roth, June 2022

Fused Deposition Modelling (FDM) technology is a widely used additive manufacturing processes. In this process, a plastic filament is fed to a nozzle, melted there and deposited in the X, Y direction based on an imported geometry. Afterwards the print bed moves one layer in the Z direction and starts depositing the plastic again in the X, Y-direction. These steps are repeated until the component is completely built up. In a recently developed system by one of the authors, the degrees of freedom in movement of the print head are extended to five axes: X, Y, Z-movement in translational direction plus an additional degree of rotation of the print bed and the possibility to tilt the print head with respect to the printed surface. Thereby, the surface quality and the geometric accuracy for rotationally symmetrical parts are intended to be improved. This paper investigates the potential of the additional motion axes with respect to part quality. To determine the accuracy, surface quality and the ability to print overhangs, tests have been carried out and compared to conventional manufactured FDM parts (X, Y, Z-kinematics). In a further step, the printing of the parts after model preparation in polar coordinates is compared to printing in Cartesian coordinates. To investigate the influence of the print head adjustment on part quality, namely surface roughness, test runs were performed with print head adjusted at different angles to the surface. Suitable demonstrators were developed for this purpose and evaluated in comparison with manufactured FDM parts using commercially available printers limited to X, Y, Z-movement only. The tests show that the recently developed 5-axis printer has a lot of potential. It’s comparable in performance to a commercially available FDM printer from the mid-price segment. The possibility of tilting the print head is the biggest advantage of the system. This has significantly improved part quality when printing overhangs and angled surfaces. The comparison between polar and Cartesian coordinates showed an improvement in surface quality for cylindrical parts printed by polar coordinates.

Investigating The Optical And Mechanical Properties Of Stimuli Responsive Electrosterically Stabilized Nanocellulose Crystals In Thermoplastic Polyurethane
Justin Anderson, Tyler Sequine, Mica Pitcher, Amir Sheikhi, Michael J. Bortner, June 2022

A new type of nano-cellulose crystal (CNC) has been gaining interest for its unique morphology combined with its as-produced carboxylate functionality: electrosterically stabilized nano-crystalline cellulose (ENCC). When ENCCs are added to thermoplastic polyurethane (TPU) composites and submerged in water they display a unique increase in opacity. Using UV-VIS and DMA, the optical and mechanical properties of these composites can be studied at differing ENCC concentrations.

Fabrication Of Expandable Filaments Towards In-Situ Foam 3D Printing Of Microcellular Poly(Lactic Acid)
Karun Kalia, Benjamin Francoeur, Alireza Amirkhizi, Amir Ameli, June 2022

The purpose of this study was to investigate the feasibility of in-situ foaming in fused filament fabrication (FFF) process. Development of unexpanded filaments loaded with thermally expandable microspheres, TEM is reported as a feedstock for in-situ foam printing. Four different material compositions, i.e., two grades of polylactic acid, PLA, and two plasticizers (polyethylene glycol, PEG, and triethyl citrate, TEC) were examined. PLA, TEM and plasticizer were dry blended and fed into the extruder. The filaments were then extruded at the lowest possible barrel temperatures, collected by a filament winder, and used for FFF printing process. The results showed that PLA Ingeo 4043D (MFR=6 g/10min) provides a more favorable temperature window for the suppression of TEM expansion during extrusion process, compared to PLA Ingeo 3052D (MFR=14 g/10min). TEC plasticizer was also found to effectively lower the process temperatures without adversely interacting with the TEM particles. Consequently, unexpanded filaments of PLA4043D/TEM5%/TEC2% was successfully fabricated with a density value of 1.16 g/cm3, which is only ~4.5% lower than the theoretical density value. The in-situ foaming in FFF process was then successfully demonstrated. The printed foams revealed a uniform cellular structure, reproducible dimensions, as well as less print marks on the surface, compared to the solid counterparts.

Production Of Flexible Thermally Conductive Thermoplastic Pipes By Orientation Of Filler Particles
Kevin Buchalik, Reinhard Schiffers, André Kayser, Marco Grundler, June 2022

Pipes for heat exchanger systems are usually made of metals to achieve a high level of energy transfer. Polymers, in comparison, save weight and costs and are suitable for use in corrosive and chemically aggressive environments. However, for many applications the comparatively low thermal conductivity of polymers is a disadvantage. To overcome this, polymers are usually mixed with high amounts of fillers, which transport the heat through the pipe wall. But the use of high filler ratios influences the mechanical properties of the pipe significantly. The aim of this paper is to develop a concept for a pipe extrusion die which aligns the filler particles in radial direction, so that the anisotropic material properties of the compound can be utilized and thus the amount of filler can be reduced. Consequently, the flexible material properties can be maintained as far as possible. Several die concepts are presented and their influence on the thermal and mechanical properties of the pipe are compared.

In-Depth Rheological Study Of Acrylic Processing Aids For Rigid Pvc Applications
Manoj Nerkar, Sam LaRosa, Mark Swain, Rich Ketz, June 2022

Acrylic processing aids are used widely in rigid Polyvinyl Chloride (PVC) applications. Key functions of processing aids in terms of processing and performance are discussed in the paper. Effect of molecular weight of acrylic processing aids on their functions are studied. Additionally, effect of processing conditions, such as temperature and shear on fusion characteristics of PVC formulations, are investigated. Shear rate in the processing was varied by means of rotor speed in torque rheometer. Processing aids of wide molecular weight range are evaluated in the study. It was observed that relatively lower molecular weight processing aids have different response to change in shear and temperature than higher molecular weight processing aids. Depending upon fusion conditions PVC formulations can yield either single or double fusion peak. Generally, it was considered that ultra-high molecular weight processing aids yield double fusion peak, however, it was demonstrated in the studies that it is not true. Fusion conditions, temperature, and shear are the main driving forces of fusion dynamics, resulting in either single of double fusion peak. Melt viscosity and shear thinning properties are also examined. Relatively lower molecular weight processing aids showed higher shear thinning behavior.

Scale Up Optimization Of Optical Nanolayer Films: Improved Thickness & Compositional Control
Michael Cantwell, Chris Oseredczuk, Mike Hus, Joseph Dooley, Michael Ponting, June 2022

A nanolayer coextruded optical film process was scaled up and optimized to show improvements in the thickness and compositional control at production level throughput rates. Adjustment of processing temperatures, implementation of online continuous gauging and automatic die lip adjusting equipment, and upgrades to the cast film pinning system led to improvements of film thickness control. A unique profile control scheme utilizing only the middle layer’s thickness instead of the total film thickness has been successfully utilized to control the critical layer’s thickness. Automation and optimization of the extruder’s feeding system provided compositional control capable of meeting tight quality specifications. With these improvements, production scale throughput rates of high-quality optical cast film capable for unique gradient refractive index (GRIN) optical applications were demonstrated.

Evaluation Of Component Specifications Of Largeformat Plastic Products Through The Use Of Machine Learning Methods
Michael Werner, M.Eng., Prof. Dr.-Ing. Thomas Seul, Prof. Dr.-Ing. Michael Gehde, Prof. Dr.-Ing. Andreas Wenzel, Norbert Greifzu, M.Sc., Markus Lehr, June 2022

This conference paper presents the investigations, results and findings from the research project "Tool-integrated assistance system for production control of highly complex and demanding component specifications" (acronym in German WASABI). The project investigates the possible use of sensor technology in combination with machine learning methods for the prediction of quality-determining component features on large-format plastic products. Furthermore, the information obtained will be used to propose target-oriented recommendations for action based on the predicted feature characteristics. An outer skin component (bumper) from the automotive sector was defined as the reference product for the investigations into the prediction possibilities of demanding component specifications. The injection molding tool required for production was designed as part of the project work and equipped with a variety of different sensor types (including pressure, melt contact, displacement measurement). The recording of the measurement signals is realized by a self-developed hardware system concept. The aim of the research is to predict various quality-determining characteristics from the fields of geometry (including total length) and surface (including sink marks). In the course of the project, extensive tests were carried out to generate a meaningful database. Through analysis and evaluation, it was possible to define the positions and number of sensors that provide a high level of information. Ultimately, three different approaches of machine learning methods could be learned for the prediction of component qualities and the prediction of corrective actions. These structures could be verified in laboratory environment by appropriate test data sets.

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