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Conference Proceedings

Foaming Behavior And Property Of PMMA Nanofoam Fabricated By By Hot-Bath And Hot-Press Foaming
Po-Chih Tseng, Kiday Fiseha Gebremedhin, Nigus Maregu Demewoz, Shu-Kai Yeh, June 2022

Nanocellular foam has attracted significant attention because of its superior physical and mechanical properties than microcellular foams. In this study, nanocellular foams were produced using the hot-bath and hot-press foaming methods. By lowering the saturation temperature (Tsat) to -30 ºC, the CO2 solubility was increased to 45.6%, and the cell size was reduced to less than 40 nm. Samples prepared by hot-bath exhibited smaller cell size, thinner solid skin, and transitional layer.

Fem Modeling On Scratch Behavior Of Micro-Patterned Polymer Surfaces
Sumit Khatri, Shuang Xiao, Hung-Jue Sue, Xing Cheng, June 2022

Polymers are inherently scratch sensitive due to their soft nature. Utilizing patterned surfaces while retaining transparency is a viable strategy to achieve better scratch performance. In this paper, we model the scratch behavior of micro-patterned surfaces using FEM simulation by employing a powerful coupled Eulerian-Lagrangian approach. The effect of two different pattern types on scratch behavior is studied and validated with available experimental results. Results suggest the significance of patterned surface topology in improving scratch performance.

Cyclic Olefin Copolymer Foam: A Promising Thermal Insulation Material
Ruiyan Zhang, Eric S. Kim, Sandra Romero-Diez, Patrick C. Lee, June 2022

In the effort to alleviate climate change and energy consumption issues, thermally insulating polymeric foams can improve energy-management efficiency. we report a superior thermal insulation (~28.5 mW⋅m-1K-1) microcellular foam from ethylene-norbornene (NB) based cyclic olefin copolymers (COCs). Unlike the traditional carbon-filled approach, the incorporation of more NB segments (content from 33, 36, 51 and 58 mol %) in the COC structure greatly improved its ability to block thermal radiation without increasing its solid thermal conductivity. Using the supercritical CO2 and n-butane as physical blowing agents, we fabricated COC foams with tunable morphology. The void fraction of the foams ranged from 50 to 92%, and they demonstrated a high degree of closed cell content (>98%). In COC foams with given cellular structures (e.g. void fraction of 90%, cell size of 100–200 μm and cell density of ~107 cells/cc), their total thermal conductivity decreases from 49.6 to 37.9 mW⋅m-1K-1 with increasing NB content from 33 to 58%, which is attributed to high- NB COC’s strong ability to attenuate thermal radiation.

Diffusion-Bonded Mold Inserts Expand The Portfolio Of Injection Molding Tool Manufacture
Vanessa Frettloeh, Udo Hinzpeter, Jan Pfeiffer, Christian Kolbe, Udo Staps, Felix Gemse, Simon Jahn,, June 2022

Due to rising demands on the quality of the final plastic product, it becomes increasingly important to influence the thermal behavior of the injection molding tools. Due to this fact the geometry of heat control channels becomes very complex, leading to a change in the manufacturing strategy of large-scale tools: manufacturing of a layered structure followed by joining the complete component. Besides the influence of the surface roughness and precision of the mold making the possibility of joining non-planar surfaces is elucidated. To demonstrate and to evaluate the diffusion bonding process, a demonstrator injection-molding tool was constructed and realized by joining the nozzle side and the ejector site of the mold by diffusion bonding after the contour conformal cooling channels were integrated. The cycle time for the production of fan wheels with the finalized mold could be reduced by 10%. Moreover, the concentricity of the fan wheels could be improved.

Evaluation Of Shear Modulus Using Destructive Shear Test And Non-Destructive Ultrasonic Shear Waves
Yannick Bernhardt, Marc Kreutzbruck, Ruben Czichos, Jörg Dittmann, Peter Middendorf, June 2022

The material properties of fiber reinforced plastics are highly directional and the final fiber orientation can usually only be determined after the manufacturing process by time-consuming and cost-intensive sample preparation. The determination of the mechanical properties usually requires destructive testing. Compared to conventional methods, the method of ultrasonic birefringence presented here allows a non-destructive determination of the shear moduli G13 and G23. Furthermore, it allows the determination of the fiber orientation without the need of a complex specimen preparation. The difference in shear modulus measurement between the two methods is less than 1%.

Experiment And Simulation Of 1D Flow And In-Plane Permeability Validation Considering Fabrics Orientation Effects In Resin Transfer Molding
Yu-Ho Chen, Yi-Kai Kao, Chen-Chieh Wang, Hsun Yang, Yuan Yao, Chia-Hsiang Hsu, Rong-Yeu Chang, June 2022

The purpose of this research is to develop measurement devices and verify whether the permeability values obtained by different experimental devices and theoretical models are correct through Moldex3D RTM simulation tool. The experimental mold dimension and process parameters are established in Moldex3D for verification, such as one-dimensional flow and radial flow. From the results, it is known that the experimental and simulation results are highly consistent. Therefore, Moldex3D simulation software can be used as a verification tool to compare the permeability and flow front.

Turnkey Solution For 3D Metal Printed Conformally Cooled Injection Mold Inserts
Zakary Smith, June 2022

Background: In Spring of 2020, Instaversal was contracted to test our newly developed conformal cooling technology, CoolTool™, against existing production benchmarks for a plastic injection molded Pipe Bracket Adapter. The Product Innovator was going through a period of elevated demand where the current cycle time of the existing injection mold tool prohibited them from meeting their demand. When cooling cycles were sped up this led to higher scrap rates due to sink marks. This left the Product Innovator with two options: delay delivery of the product to their top customer with the risk of losing the sale and potentially losing the customer or to invest in additional injection mold tools to double production capacity. To meet the customer’s demand, 100,000 parts needed to be produced in a 60-day time period. This request created conflict with the contract manufacturer. They were being asked to absorb the cost of additional molds to meet the timing or run full 24-hour (Monday-Friday) shifts over the 60-day period which would create losses in revenue by eliminating other clients’ scheduled jobs.

Zirconium Dioxide As A Thermo-Insulating Coating For Molds In Plastic Injection Molding
Anatoliy Batmanov, Vanessa Frettloeh, Ruben Schlutter, Frank Mumme, Paul Ditjo, Ivan K. Kibet, Juergen Wieser, June 2022

Effect of the thermal barrier coating (TBC), deposited on the mold for plastic injection molding was investigated. The mold cavities were coated by yttrium stabilized (YSZ) and phosphorous doped (PDZ) zirconium dioxide as multilayer film using chemical vapor deposition (CVD) method. It was found that films deposited at higher temperatures have better thermo-insulating properties than films deposited at lower temperatures. Growth rate and film porosity increase as deposition temperature increases. It was observed that the TBC slightly affects the flow length of the plastic melt but improves the filling ability of poorly vented molded part areas.

Relative Humidity Effects on Accelerated Aging of Medical-Grade Polymers: Should ASTM F1980 be Revised to Recommend Constant RH Instead of Constant Moisture Content?
Aniruddha Palsule, Rachel Jacobs, Martin Gibler, Robert J. Klein, June 2022

ASTM F1980 provides a methodology for accelerated aging of sterile barrier systems for medical devices, and is also widely used as the definitive guide for accelerated aging of medical devices and pharmaceutical packaging. ASTM F1980-16, as well as previous versions going back to 2007, emphasize that when increasing temperature to accelerate aging, it is preferable to decrease relative humidity so as to maintain an approximately constant moisture content. However, there is a revision under consideration by the ASTM F02.50 committee that would dramatically change this guidance to indicate a preference (although allowing for other options) to keep relative humidity approximately constant. This change is based on somewhat limited test data and literature review published recently by Thor et al. In this paper, we perform a study looking at eight resins (PP, COC, ABS, PC/PET, Copolyester, PBT, PA66gf, PUR) that have been aged at 60C and three different RH levels to evaluate the impact on aging. Our findings to date indicate that: (i) yes, it is likely that RH should be held constant when increasing temperature in order to keep moisture constant in the resins at a similar level; and (ii) for the medical-grade resins evaluated here, RH level does not significantly impact the physical aging mechanism. We also recommend that further accelerated aging studies are performed to more thoroughly evaluate the impact of moisture content on Q10 factors, corrosion rates, and other endpoints before this dramatic change is made to the ASTM F1980 standard.

Effects Of Sample Shape And Adhesive Type On Rheology Of Unidirectional Carbon Fiber Prepregs
Arit Das, Kathleen J. Chan, Michael J. Bortner, David A. Dillard, Davide S.A. De Focatiis, June 2022

The viscoelastic properties of carbon fiber reinforced thermoset composites are of utmost importance during processing such materials using composite forming. The quality of the manufactured parts is largely dependent on intelligent process parameter selection based on the viscoelastic and flow properties of the polymer resin. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G’), loss modulus (G’’), and loss tangent (tanδ) are used to determine the critical transition events (such as gelation) during curing. An understanding of the changes in viscoelastic properties as a function of processing temperature and degree of cure provides insight to establish a suitable processing range for compression forming of prepreg systems. However, tracking viscoelastic properties as a function of cure during the forming process is a challenging task. In this current work, we have investigated the effect of sample size and adhesive type on the rheological properties of a commercially available carbon fiber prepreg material. Specifically, determining the linear viscoelastic region (LVE) as a function of sample configuration and different adhesive chemistries were explored. The results suggest that the square-shaped sample geometries coupled with cyanoacrylate based adhesive are optimum for conducting rheological characterization on the carbon fiber prepreg system.

Mechanical Recycling Of Single-Use Polyethylene Into Materials With Variable Properties
Arun Ghosh, Ashik C. Kannan, June 2022

The post-consumer single-use polyethylene-based plastic bags supplied by the supermarket grocery stores, are converted into new materials with improved mechanical properties using a thermo-mechanical recycling process. The low-density polyethylene (LDPE) sourced from waste plastic bags, is injected into a high shear internal mixer and compounded with the additives such as acrylonitrilebutadiene copolymer or nitrile rubber (up to 10 wt%) and also treated with an organic peroxide curing agent. The resultant materials exhibit high ductility and elasticity, with a maximum tensile strength of 20.3 MPa, stiffness of 1262 MPa, elongation of approximately 500%, and impact strength of 62 kJ/m2 depending on materials compositions. These mechanical properties are profoundly higher than those of neat recycled LDPE. It is observed that the post-consumer plastics contain a significantly high amount of calcium mineral of approximately 30 wt% (13 vol %)[1], which plays a key role in improving mechanical properties during high shear blending with additives such as nitrile rubber. The melt-rheological characteristics such as complex viscosity and storage modulus of the materials are analyzed to evaluate the thermal recyclability and thermoplastic nature of the materials.

Thermal & Rheological Characterization Of Two High Density Polyethylene Grades
Phat T. Vu, Azizeh-Mitra Yousefi, June 2022

Presently, polymers such as high density polyethylene(HDPE) are utilized for an extensive array of applications because of their low weight, economical production, and exceptional physical and chemical properties. Thermal analysis and rheological measurements are the ideal techniques for characterizing the material properties of polymers. This paper employs thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and capillary rheometry to collate the contrasting nature of two HDPE resins. These resins will be referred to as HDPE A and HDPE C and are similar to two resins (Sample A and Sample C) included in a previous publication [1] that focused on blow molding parison sag and swell. TGA was used to investigate the thermal stability of these polymeric materials, as they were ultimately decomposed inside a furnace. DSC was conducted to examine the thermal transition behaviors of the polymers. Capillary rheometry was run to construct shear viscosity and extrudate swell versus shear rate data through single and twin bore configurations under varying temperatures. These measurements were conducted under testing conditions that are representative of industrial processes, such as extrusion blow molding. HDPE C was found to exhibit greater extrudate swell than HDPE A, as measured by capillary rheology measurements, and these data correspond to the earlier published results that Sample C exhibited greater parison diameter, thickness, and weight swell than Sample A as measured with a lab scale extruder.

Effect Of Plasticizer Content In EPDM On Ex-Situ Wear Test After High Pressure Hydrogen Exposure
Byeonglyul Choi, Byoung-Ho Choi, Un Bong Baek, June 2022

In high pressure hydrogen environment, elastomeric seals undergo degradation of mechanical properties and wear problems. Especially, wear of elastomeric seals causes failure of sealing system. Therefore, developing the material with good mechanical properties and wear resistance is important. In this study, five ethylenepropylene-diene-monomer (EPDM) with different content of plasticizer were prepared to investigate the effect of plasticizer on their tribological properties after the specimens were exposed to high pressure hydrogen.

Stress Corrosion Crack Growth Of High Density Polyethylene With Cracked Round Bar Specimen In Chlorine Medium
Jung-Wook Wee, Alexander Chudnovsky, Byoung-Ho Choi, June 2022

In this study, the stress corrosion crack (SCC) growth model for the cracked round bar (CRB) specimen was developed. The axisymmetric crack layer (CL) theory for simulating the slow crack growth (SCG) behavior of CRB specimen was modified to consider the chemical degradation due to diffused aggressive environment. The diffusion of oxidative fluid into the process zone (PZ) in radial direction is considered. Also, the chemical degradation kinetics of PZ materials due to the oxidation were modeled. The proposed model was shown that the discontinuous SCG behavior and the deteriorative effect from the chemicals were successfully simulated.

Diffusion-Softening Of Cellulose Nanocrystal And Thermoplastic Polyurethane Composites
Cailean Q. Pritchard, Jacob J. Fallon, Jeffrey Shelton, Michael J. Bortner, Cody Weyhrich, Katherine Heifferon, Boer Liu, Timothy E. Long, E. Johan Foster, June 2022

Smart materials that can adapt their mechanical response in the presence of an external stimuli are popular for their applications in 4D printing. Such printing methods exploit a smart material’s capability to interact with these stimuli to impart controlled material deformation tailored to specific applications. A modified percolation model was formulated to predict the dynamic transition exhibited in polymer composites containing cellulose nano-crystals (CNCs) which undergo mechanical softening in the presence of water. Coupling the effects water diffusion to the degree of CNC connectivity provided a method to capture the dynamic softening of CNC-based, water responsive smart materials as a function of filler loading. This modeling approach can be implemented to develop humidity sensing actuators and water-sensitive shape memory devices.

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.

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