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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Conference Proceedings
Optimization of Pack and Hold times for Hot Runner and Valve Gated Systems in Injection Molding
Suhas Kulkarni, May 2014
For cold runner molds, the pack and hold times are optimized by conducting a gate freeze study (or gate seal study) where the part weight is recorded as a function of the pack and hold times. When the gate freezes the part weight remains constant with increasing pack and hold times. A second or so is added to the lowest value of time where the part weight stays constant and this number is taken as the total time for the setting of the pack and hold times. However, in hot runner systems or in valve gated systems the gate area always has molten plastic and therefore the above method does not produce acceptable results. A method for optimizing this value in hot runner systems or valve gated systems is proposed based on the Cosmetic and Dimensional Process Window concept that was introduced by the author in an earlier paper. This was followed up with experimental results.
Test Method Development for Outdoor Exposure and Accelerated Weathering of Vinyl Siding Specimens
Sean Fowler, Jeffrey Quill, May 2014
This paper provides an overview of extensive research conducted by the Vinyl Siding Institute (VSI) on the development of new test methods for exterior plastic building products. The purpose of the VSI study was to develop an accelerated testing protocol for use in certifying materials. This paper describes the development of an outdoor certification test program and subsequent efforts to create an accelerated weathering test method that could be used to predict the results of the outdoor protocol with a high degree of accuracy. Outdoor weathering tests were conducted in Florida, Arizona and Northern temperate locations to obtain baseline data for comparison. This part of the research led to the development and subsequent publication of ASTM D6864. Accelerated laboratory tests were performed in Fluorescent UV/Condensation test apparatus and Xenon Arc test chambers. The process involved the examination of multiple types of equipment, multiple cycles, and multiple conditions, and comparing the various results to the outdoor exposures. Testing suggested that for this particular material, one method was more suitable than the other. The proposed method was verified with repeat testing and rugged statistical analysis. Round robin testing was conducted to determine repeatability and reproducibility. Although the proposed accelerated method was not adopted into the VSI’s certification program, its results demonstrated high rank order correlation with outdoor test results, giving the user much greater confidence that materials passing the accelerated test will pass the outdoor test. The accelerated method, therefore, is useful during research and development because it provides a fast and reliable method for evaluating small formula changes. It is useful for selecting formulations to include in a 2 year certification test.
Formation of Morphology as a Function of Process Control by Foam Injection Molding of a Functionally Graded Component
Hans-Peter Heim, Mike Tromm, May 2014
A special mold technology enables the production of foam injection molded components with locally differing foaming ratios. Thus, components with functionally graded foam structures can be produced in one processing step. The method (pull and foam method) is based on the idea of creating components with thin-walled areas with a high surface quality and partially foamed, thick-walled areas (e.g. with the function of integrated structural elements) in a controlled foaming process. This paper describes the characteristics of the structure and density in the differentially foamed areas in correlation with the essential processing parameters.
Investigation of Melt Modulation Control and its Effect on Cold-Runner Injection Molding Packing Parameters and Final Product Quality
Majed Alsarheed, John P. Coulter, May 2014
This paper describes current efforts to investigate and expand melt modulation capabilities in controlling the packing parameters of cold-runner based injection molding processes. Packing parameters, including packing pressure and packing time, have significant impact on the internal molecular orientations, mechanical properties and optical performance of injection molded polymeric products. This investigation focuses on manipulating and controlling packing parameters using melt modulation in order to produce molded parts with different optical and physical properties in each injection molding cycle. Numerical simulations of common thermoplastic optical polymers, such as PMMA, PC, and PS are also demonstrated herein.
Improved Processability and Productivity of Thermoset Compounds Using Sp Scorch Protected Peroxides
Peter R. Dluzneski, Leonard H. Palys, May 2014
Peroxides are used to vulcanize a wide variety of elastomers and plastics including saturated polymers that are not curable by other means. The cure rate obtained varies depending on the stability of the peroxide. Some peroxides provide relatively fast cures but could suffer from premature crosslinking which is also known as scorch. This may result in higher scrap rates and clogged processing equipment. Other peroxides cure more slowly and are less prone to scorch but require longer cycle times. To address this predicament, Arkema has developed a series of scorch protected peroxides1 which are capable of providing protection against premature crosslinking while not affecting the overall cure time. This allows the use of faster curing peroxides to reduce cycle times without concern about scorch. It also allows for more rigorous mixing and processing conditions to increase output without sacrificing efficiency.
Sb2O3 Free FR PBT Product Development
Yuzhen Yang, Tianhua Ding, May 2014
Antimony trioxide (Sb2O3, ATO) is widely used as a flame retardant in combination with halogenated materials. The combination of the halides and the antimony is the key to the flame-retardant action for polymers, helping to form less flammable chars. The Objective of this work is to develop ATO free FR PBT products with equal robust FR properties. Many candidates were screened to replace ATO as the flame retardant synergist. Among them all, one FR combination package with no ATO was tried in a glass filled PBT system. Experimental results demonstrated that this ATO free FR PBT product shows good flame properties and passes UL 94 V0 rating @ 0.71 mm thickness. Meanwhile, the physical properties, mechanical properties, and processability were all well maintained. In addition, the ATO free FR PBT formulation is very robust against both extreme extrusion conditions and abusive molding conditions even when recycle materials are incorporated. The same ATO free FR package has the potential to work in other unfilled and filled PBT resins or blends too.
Tuning the Compatibility of Polyolefins with Polypropylene-Based Olefin Block Copolymers – Stiff, Tough, and Clear
Colin Li Pi Shan, Gary Marchand, Kim Walton, Edmund Carnahan, Ray Laakso, Eddy Garcia-Meitin, May 2014
Polyolefin materials requiring high clarity and low haze are still challenged to achieve the material property balance of stiffness and toughness required for durable storage containers and food containers especially at low temperatures. The selection of polypropylene polymers having a combination of high clarity and impact resistance is limited to random copolymers (RCP), impact copolymers (ICP) or those impact modified with elastomers that are either miscible with the polypropylene (PP) or have similar refractive indices. Impact efficiency of an elastomeric modifier is directly related to its crystallinity and dispersion of the individual elastomer domains into a PP matrix. Conventionally, dispersion of an elastomer into polypropylene is challenged by the melt-mixing process and compatibility with the polypropylene. The recently announced INTUNE™ polypropylene-based olefin block copolymer comprising iPP hard blocks and ethylene-propylene soft blocks can minimize the compatibility differences (between the polypropylene and an ethylene-based elastomer) by containing intra-chain segments that are compatible with polyethylene and polypropylene, respectively (1). This new polyolefin compatibilization approach is effective in combination with ethylene-based elastomers for improved dispersion and morphology stabilization, leading to modifier solutions that have high impact toughness and clarity in polypropylene.
Layer-Multiplying Co-Extrusion of High Viscoelasticity Ratio Polymers
Rongzhi Huang, Jessica Patz, Jorge Silva, Joao Maia, Benjamin A. Huntington, Roger T. Bonnecaze, Mark Cox, May 2014
Traditionally, viscosities of co-extruded polymers are required to match to obtain decent multilayer structures, which severely narrows the processing window. In this study, we introduce a way to improve the non-uniform multilayered structure in rheologically mismatched polymers during layer-multiplying co-extrusion. Both high viscosity ratio (PS/PMMA) and high elasticity ratio (TPUs) polymers were used in this paper. The solution to this problem was broken into Engineering and Material approaches. In the Engineering solution a 9-layer feedblock and a new design of multiplier die are combined to start layering with more (and more uniform) layers and lower the pressure drop. In the Material approach, external lubricants are applied to provide the system with maximum wall-slip effect, thus reducing second normal stress difference (N2) responsible for the development of elastic instabilities. Finally, finite element method simulation (FEM) via ANSYS POLYFLOW® is used as a comparison tool to validate the accuracy of predicting the formation and development of flow instabilities.
Thermal Ageing of Polyamide 12 Used for Polymer Laser Sintering – Influence on Part Quality Characteristics
Stefan Josupeit, Stefan Rüsenberg, Nicola Rupp, Monika Gessler, Hans-Joachim Schmid, May 2014
Polymer laser sintering is one of the most important additive manufacturing technologies for the tool-less production of three-dimensional prototypes and end-use parts. In this process, parts are manufactured layerwise out of a polymer powder by laser exposure. After the building process, these parts are located within a loose bulk powder cake. Due to long process times and high process temperatures, this powder ages thermally, which reduces the recyclability of the material. As a result, mixtures of used and virgin powder (“refreshed” powder) with a mixture ratio of approximately 50% are commonly used in the industry. The goal of this work is to determine the exact influence of different powder ages on resulting part quality characteristics, especially the mechanical behavior and the surface quality. Therefore, refreshed powder with different qualities adjusted by the melt volume rate (MVR) was processed along a defined process quality chain. To analyze the part qualities, mechanical tensile and profilometer tests were performed. The focus is on an application-oriented test set-up to ensure the usability of the results in the industry. The material used is polyamide 12 (PA 2200) processed on an EOSINT P395 laser sintering system from EOS GmbH, Krailling, Germany.
Wear Behavior of Polyaryletherketones (PAEK) under Multidirectional Sliding and Fretting Conditions
Kevin A. Laux, Hung-Jue Sue, Tim Bremner, May 2014
Fretting is said to occur when mutually loaded contacts move relative to one another with nominally small displacements. The resulting stick slip between asperities causes cracks to nucleate at the surface and may eventually lead to catastrophic part failure. Furthermore, prediction of how a material might respond to such a scenario is challenging due the overall complexity of the process. The polyaryletherketone (PAEK) family of thermoplastics has been increasingly used in such fretting environments, but few studies exist regarding their fretting behavior. In this study, a custom built multi-axis tribometer has been shown to replicate fretting of PAEK in a pin on flat configuration. The experimentation and analysis has provided new insights into this phenomenon.
Experimental and Numerical Analysis of Material Properties of Unidirectional Composites Manufactured by Tailored Fiber Placement
Amelie Leipprand, Axel Spickenheuer, Lars Bittrich, Gert Heinrich, May 2014
Working with fiber-reinforced plastics, not only the materials influence the resulting component properties but also the fabrication techniques. The Tailored Fiber Placement (TFP) technology is a textile manufacturing technique, where the reinforcing fiber thread (roving) is placed along almost arbitrary programmable curves in a 2-D plane and fixated by the stitching yarn on a textile base material. Hence the highly anisotropic material characteristics of reinforcing fibers can be fully exploited for lightweight construction if a dominating load case is known. This can lead to a dramatically increasing stiffness or strength per mass compared to conventional quasi-isotropic design. However, the TFP technology also leads to a small waviness of the reinforcing fibers in-plane and out-of-plane, decreasing the resulting mechanical properties of the component slightly. For high performance lightweight construction it is important to know about these effects qualitatively and predict the reduction of material properties compared to ideally placed fibers quantitatively. The goal of this work is to gain a first overview of the geometry of the waviness and to estimate the amount of its effects on the properties of a part produced by TFP. We start by measuring and characterizing the effects of different parameters, which can be set at the TFP machine, on the geometry of the fiber waviness. The data is analyzed statistically and by means of Fourier analysis. The findings were put into finite element (FE) analysis models of a single cell to predict the reduction of the resulting tensile stiffness. Experimental tensile stiffness measurements verify the simulated results.
Advancements in Lasermarkable Engineering Resins
Bruce Mulholland, May 2014
Laser marking on plastics is growing in use. Bar codes and product lot data can currently be marked with lasers some commodity resins. However, of specific interest is the use of lasers to mark functional or decorative information on engineering resins. Because of their inert surface characteristics, these resins can be difficult to mark via printing using ink. This paper focuses on the development of specialty grades of engineering resins that yield excellent sharp, clear images when laser marked. Grades have been developed for laser marking white characters on black, dark characters on white and other effects.
Poly(Lactic Acid) with Improved Melt Strength and Gardner Impact Strength
Leonard H. Palys, May 2014
Poly(lactic acid) or PLA is a commercial biopolymer made from lactic acid derived from sugar fermentation. “Greenbased” [1] PLA is desired as a biodegradable film, sheet and food packaging alternative to oil-based polymers. PLA has a Tm melting point range of 150-162°C [2]. Unfortunately, PLA has poor melt strength and impact strength. High melt strength and impact strength are important properties when manufacturing sheet, film, fibers and molded goods. In this paper we explored several ideas to improve the performance of PLA while maintaining its “green” characteristics. We found that an acrylic based core-shell polymer used at a low concentration significantly increased the Gardner impact strength of 15mil extruded sheet. Also, a high molecular weight acrylic copolymer used at low levels doubled the PLA melt strength. Lastly, reacting PLA with organic peroxides increased the shear modulus, molecular weight and melt strength based on rheometer, multi-angle light scattering and Rheotens analysis.
Characterization of Carbon Fiber Laminates: Determining Ply Orientation and Ply Type via Ultrasonic A-Scan and C-Scan Techniques
Sarah Stair, David A. Jack, John Fitch, May 2014
As companies search for strong, lightweight materials to incorporate into their product line, several are turning to fiber reinforced composites. While this material is lighter than traditional metals, its properties are dependent upon the manufacturing process and the orientation of the fibers within the part. For example, in a carbon fiber reinforced laminate the orientation of each ply directly affects the properties of the total stack and ultimately the final processed part. Employing a destructive testing method to determine material properties will render the part unsuitable for its intended application. Thus, a nondestructive testing method must be applied to determine the part’s material properties. The current study applies ultrasonic A-scan and C-scan techniques to characterize the final as-manufactured part. The as-manufactured part is not always the same as the as-designed part. Thus, a non-destructive testing technique that can validate manufacturing at the individual ply level is of critical importance. In this method, the C-scan measurements are analyzed using a custom Matlab program, and the results are displayed to the user in the form of a video. The video begins with an image of the top surface of the laminate, and each subsequent frame steps further into the thickness of the laminate. The uniqueness of this system lies in its ability to capture the carbon fiber tows within a given ply thus allowing the ply type and orientation to be determined for each lamina in the bulk laminate. While the initial results of this study are promising, surface features, which are a common artifact of the manufacturing process, have affected the analysis of the C-scan data. This study focuses on the effects of these surface features and discusses potential solutions.
Extensional Flow Blending of Immiscible Polymers with Nanoparticle Stabilization
Matthew S. Thompson, Sushant Agarwal, Xueyan Song, Rakesh K. Gupta, May 2014
In this work, blends of high-viscosity polyethylene dispersed in polystyrene (viscosity ratio > 4) were employed to study the effects of extensional flow mixing on morphology. Coarse blends, prepared in an internal mixer, were subjected to extensional flow by forcing them through converging flow dies, which resulted in decrease in the volume-average diameter of the drops. To inhibit coalescence, nanosilica was incorporated into the blend. This was found to decrease both the initial coarse blend dispersed phase size and the drop size after extensional flow. However, addition of nanosilica had only a small effect on blends subjected to extensional flow.
Ratio Function of Dynamic Moduli and its Application in Consistency Check
Jianhua Huang, May 2014
A new type of functions – a ratio of linear combination of dynamic moduli at different frequencies – and their bounding properties were studied. It was shown that these functions have an important feature, that is, if f represents a given ratio function for a Maxwell model whereas F represents the same function for a generalized Maxwell model, then f and F have exactly the same bounds. So the bounding properties of F can be known by analyzing simple function f only. The study showed that all four ratio functions proposed are bounded for a linear system, which means the dynamic moduli at different frequencies are not independent. Given any dynamic data, one can check the data by calculating the value of ratio function and comparing it with the bounds. If the value breaks the bounds and the violation cannot be attributed to normal experimental errors, then the data must be inconsistent. If the violation exists in the shifted data but not the original ones, then the shifted data might contain artificial errors. The method worked well as it was used to check the real G’, G” data reported in the literature.
Effect of Fountain Flow on Fiber Orientation and Distribution in Fiber Filled Polymers during Mold Filling
Abrahan Bechara, Sebastian Kollert, Jakob Onken, Daniel Ramírez, Tim A. Osswald, May 2014
The mold filling process of fiber reinforced parts manufactured by injection or compression molding plays a significant role on the quality of the finished product. For instance, during the injection molding process, the fountain flow dominates the mold filling stage, having a strong effect on fiber orientation at different locations within the molded part. In this work, the effect of fountain flow on fiber orientation is studied via simulation as well as experimentation. The fiber motion is simulated using a mechanistic approach where fibers are modeled as interconnected elements subjected to hydrodynamic and contact forces (fiber-fiber interactions). The simulation results show a good match with experiments performed in a device that allows visualization of the fountain flow region during injection molding.
Mechanistic Model to Determine Fiber Orientation Simulation Material Parameters
Erwin Baur, Sebastian Goris, Daniel Ramírez, Philip Schmidtke, Tim A. Osswald, May 2014
A joint Natural Fiber Composite (NFC) research project [1] aims for an integrated mechanical/crash simulation of natural fiber reinforced plastics. This paper presents results from one of the NFC tasks, namely, an alternative way to find fiber orientation material parameters for commercial simulation software by using a mechanistic fiber motion model. During processing of fiber reinforced plastic parts, anisotropy is introduced due to fiber alignment caused by the deformation of the flowing polymer melt. Different models are available to model the development of fiber orientation during processing. These orientation models include material dependent parameters, which are obtained using cumbersome reengineering techniques. These techniques involve measuring the fiber orientation within the finished parts, and fitting the material dependent parameters until the model’s fiber orientation distributions match the actual fiber orientation. For glass fibers, the models and the parameters have been well investigated. However, data for modeling the orientation distribution development during processing natural fiber filled resins, is basically non-existent. Furthermore, actual measurements of fiber orientation distributions within natural fiber filled composites are challenging to obtain. In this work, an alternative method has been developed to find the fiber-fiber interaction coefficient Ci from the Folgar-Tucker model, by coupling the model with a mechanistic fiber model. In this technique, Ci is iteratively optimized until the fiber orientation distribution computed using the Folgar-Tucker model fits the fiber orientation fields predicted by the mechanistic model. With this virtual method, the costly measurement of actual fiber orientation fields within a finished part, and the subsequent re-engineering approach can be avoided. Furthermore, the mechanistic model can be used to determine any material dependent parameters needed for other fiber orientation predictive model
Flow-Induced Fractionation of Bimodal Metallocene Polyethylene in Capillary Extrusion
Yongwoo Inn, Ashish M. Sukhadia, Paul J. DesLauriers, May 2014
We studied the melt fracture and wall slip behaviors during the capillary extrusion of metallocene-catalyzed bimodal polyethylene resins. The bimodal resin comprising a higher content of low molecular weight component showed more wall slip and unusual melt fracture behavior. GPC measurement done on the surface section of the extruded pipe of the bimodal resin showed the wall had enriched low MW component relative to the bulk. The distinct separation of the two modes and the high content of small chains of the bimodal resin promote the flow-induced fractionation leading to the small chains being more concentrated near the die walls, which in turn result in significant wall slip and unusual melt fracture behaviors observed.
Effect of Drying and Processing on the Performance of Eastman Tritan™ Copolyesters
Kaan Gunes, Roger Martin, May 2014
Proper processing of polymeric materials is often the key to achieving desirable properties, and good aesthetics in molded parts and extruded film or sheet. Proper drying of resin is particularly important for condensation polymers, which are often prone to molecular weight loss through hydrolysis. Tritan™ Copolyesters are transparent engineering thermoplastics used in medical, durable, and packaging applications. This paper discusses drying and processing conditions for Tritan Copolyesters, and its effects on mechanical properties, chemical resistance, and molded/extruded color.

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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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