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

INDUSTRIAL & TECHNICAL PART BLOW MOLDING RESIN AND COLOR CHANGE FOR SHORT RUNS

Robert Slawska | Brian Dowler | Luis Lacambra, November 2011

Many producers of large technical parts are struggling with increasing demands for short-run parts, caused by a trend toward differentiation (more SKU’s), Just In Time (JIT) delivery and multiple colors for consumer appeal. With many large technical machines requiring as much as 8-12 hours of running to switch colors or materials, this is a huge cost and profit drain on processors. This technical paper illustrates the necessary key elements in large part blow molding to tackle these supply chain requirements. It discusses current limitations, and advances in machinery design to enable fast resin and color changes in large industrial machines.

EXTRUDED MULTILAYER STRUCTURES FOR RIGID PLASTIC CONTAINERS

Authors Brian Dowler | Luis Lacambra, November 2011

This technical paper illustrates the current state and applications for multilayer containers that package food and consumer products. The paper describes different structures utilized in making containers for varying applications, including demanding barrier requirements. We also discuss how to meet requirements for food processing systems, including hot fill, pasteurization, and retort. Several case studies of multilayer containers currently in the market are shown. The paper includes pictures and diagrams and is designed to serve as an ongoing guide for anyone tasked to determine appropriate container manufacturing processes, container designs, and material configurations to meet various barrier and post-filling requirements.

A PHENOMENOLOGICAL CONSTITUTIVE MODEL FOR STRAIN SOFTENING PREDICTION IN SEMI-CRYSTALLINE POLYMERS

Mariajosé Pineda Manzano | Joel Bohórquez | Agustín Torres, November 2011

Strain softening in semi-crystalline polymers, is one of their most important viscoelastic characteristics and these materials are very sensitive to temperature and strain rate. A new phenomenological model with strain, strain rate and temperature dependence on stress was developed based on the Gsell & Jonas model with a new expression used to predict the strain softening henomena, completing the whole mechanical behavior of polymers from initial strain, strain softening and part of the strain hardening. Model verification was performed on four materials and it was developed to further study the complex deformation patterns in thermoplastic materials subjected to impact loads

TRANSIENT MOLD COOLING SIMULATION FOR THE INJECTION MOLDING PROCESS

Clinton Kietzmann | Lu Chen | Harold Lin Feng | Franco Costa | Ronan Le Goff, November 2011

In recent years, injection molding technologies have been developed which use variable mold heating and cooling to increase part quality without significantly increasing cycle time. These processes are not suited for simulation with a conventional steady-state (cycle-average) mold thermal analysis. This paper presents the development of a new 3D finite element based transient mold cooling simulation capability which includes coupling the mold thermal solution with the mold filling and packing simulation. The predicted transient mold temperatures are validated against measured mold temperatures for two instrumented injection molding trials.

NANOMINERALS & NANOOXIDES

Yatish. B. Vasudeo, November 2011

Nanoclays have to intercalate and exfoliate. The extent of intercalation and exfoliation is not understood by the processing industry. Researchers have to develop and nanoclay manufacturers have to supply a product which can intercalate and exfoliate to achieve the desired performance of the final product. The nanoclay powder which is supplied has a BET surface area of 5m2/gm or less. To disperse such a powder from 5 to 750m2/gm is difficult. To salvage such a situation, there has been a relook at minerals which are platey such as talc and mica. The finest talc supplied in the world has a BET surface area of 15m2/gm. It is possible to further grind this talc (also mica) along the basal cleavage to 100m2/gm to 200m2/gm. Such talc, if added to polymers can improve properties.

LIFE CYCLE ASSESSMENT OF METALLOCENE POLYETHYLENE IN HEAVY DUTY SACKS

Abdelhadi Sahnoune, November 2011

The substitution of plastic for more traditional materials stems from its reliability and affordability. However, with the heightened awareness on sustainability, plastic from fossil sources are sometimes perceived to adversely impact the environment. In an effort to address this issue, a detailed life cycle assessment of heavy duty sacks made from metallocene polyethylene (mPE) has been completed. The sacks are used in packaging powdered products for the construction industry. The results show that these sacks have several positive attributes and in many instances, may be a preferred alternative from a sustainability perspective. In fact, in manufacturing, transportation and handling mPE sacks are shown to consume significantly less energy and emit less greenhouse gas than paper-based alternatives. Additional environmental benefits will be discussed.

Part and Mold Design Guidelines for the High Volume Compression Molding of Carbon Fiber Reinforced Epoxy

Donald M. Lasell, November 2011

The objective of this paper is to discuss unique part and mold design requirements for high volume, cost competitive compression molding of carbon fiber reinforced epoxy (CF/E) uni-directional prepregs (UD). The typical part and mold design for compression molding of chopped fiberglass reinforced polyester sheet molding compound (SMC) will be used for comparison. Information that can be used as a design and processing guide for composites engineers involved with the development of high stiffness and strength CF/E for application in the transportation industry will be shared.

High Throughput Compounding: Application Specific Thermoplastic Compounds Developed

Markus Gross | Gerhard Maier, November 2011

Polymaterials has developed a new high-throughput compounding (HTC) technology which generates thermoplastic formulations and DIN-ISO compliant test specimen accepted by engineers and the plastic industry. This technology accelerates the development of new compounds and is also much more cost-effective since only a fraction of material and time is needed compared to the conventional process. HTC not only increases the output significantly but also generates more insights enabling one to push innovation and to cut time to market for new products. The presentation introduces the technology and illustrates its capabilities by demonstrating several case studies.

THERMAL CONDUCTIVITY OF HYBRID FILLED HDPE NANOCOMPOSITES

Michael Thomas Muller | Beate Krause | Bernd Kretzschmar | Ivonne Jahn | Petra Potschke, November 2011

In this study composite materials based on highdensity polyethylene (HDPE) with fillers containing nanostructures were prepared using melt mixing. Vapour Grown Carbon Fibers (VGCF), multiwalled carbon nanotubes (MWCNT) of the types Baytubes® C150P and NanocylTM NC7000, anthracite powder, microsilica, organoclay and expanded graphite (EG) as well as mixtures of these fillers were used. The amount and mixing ratios of the hybrid filled systems have been varied to determine the effect on the achievable level of thermal conductivity as measured on pressed plates. The filler dispersion and phase adhesion were studied using scanning electron microscopy. When limiting the maximum filler content to 10 wt%, the highest enhancement in thermal conductivity by 166% was found for VGCF followed by a 1:1 filler combination of VGCF with EG (148%).

A REVIEW OF LONG FIBER THERMOPLASTICS (LFT) COMPOSITES DESIGN

Raj N. Mathur | Stephen T. Bowen, November 2011

Long fiber thermoplastic (LFT) composite design studies often emphasize fiber content but are sketchy on fiber-orientation, fiber-matrix interface and mold design. In this paper we detail a comprehensive approach to designing with LFT materials. Specific examples are given. Carbon-fiber compounds were successfully substituted for die-cast magnesium parts by redesigning the metal part for injection molding. Tailored fiber architectures were achieved through strategic gate locations, as advised by Finite Element Analysis (FEA) and Mold Flow Analysis (MFA). Mechanical properties were enhanced through modified molding processes.

Influence of the Mould Cooling on the Quality and Reproducibility of Injection Moulded Parts

Walter Michaeli | Christian Hopmann | Silke Allert, November 2011

The use of pulsed cold water instead of tempered coolant is suggested to be a versatile and cost-efficient technique for the cooling of injection moulds. However, the advantages and limitations of such discontinuous cooling strategies are still a controversial issue. In this paper the behaviour of a discontinuous temperature control system is analysed with a particular focus on the reproducibility of the process and the realisable dimensional stability of the parts and compared to that of a continuous cooling. For the investigations both a conventional and a conformal cooling channel geometry are considered. It turns out that at high mould temperatures the warpage of the parts can be reduced by use of discontinuous cooling, but at the same time the reproducibility of the process is affected adversely. The regulation of the discontinuous cooling proved to be challenging especially in combination with conformal cooling.

CONSIDERATION OF WELD LINE STRENGTH WITHIN THE SIMULATION OF SHORT FIBER REINFORCED THERMOPLASTICS

E.h. W. Michaeli, Ch. Hopmann, Klaus Kusters, November 2011

Weld lines are formed during injection molding, when two flow fronts meet. They are often not avoidable in complex technical parts. Their presence reduces mechanical strength, especially in high performance short fiber reinforced materials. Evaluating the load of highly stressed parts requires accurate knowledge of the interrelationship between the type of weld line, its morphological structure and the resulting mechanical properties. This paper aims at the development of a simulation method which enables the mechanical properties of weld lines to be considered precisely in part design.

DESING OF INJECTION MOLDS FOR FLOATING VALVE SYSTEM USING PET BOTTLES AS FLOATING DEVICE

Mariangel Berroterán | María Virginia Candal | Nelson Colls | Magda Castillo | Luis Marín, November 2011

The plastic parts for a float-valve system were designed. In the design was considered the use of PET bottles as floating device instead of the regular spheres, in order to promote the reuse of this plastic container and to decrease plastics residues. Additionally, the part thickness was reduced to use less plastic on the parts, and to decrease cycle times. All molds are two-plate and two cavities. The refrigerating system proposed uses U-shape channel, and the expulsion system is composed by ejector pins. Threaded connector´s mold is more complex due to require two-step opening.

Modeling Container Shelf Life & Top Load Performance

Scott W. Steele | Sumit Mukherjee | Mark Rule, November 2011

The use of performance modeling is becoming more and more critical to the packaging industry. This trend is driven both by lightweighting efforts and the need to shorten package development times. The primary driver for reducing the amount of material used in packaging is cost reduction, with environmental positioning an ancillary benefit. However, it is critical to not compromise the shelf life or creep performance of the package, particularly in regions of the world with temperature extremes. This paper will explain key elements necessary for precise modeling of package shelf-life performance. The mathematical models considered are M-RULE® Container Performance Model and Virtual Prototyping™ Software. Some examples of how computer modeling has been applied to optimize package performance will be discussed.

A self-optimising injection moulding process extendable by an incremental cooling system

E.h. W. Michaeli | Ch. Hopmann | A. Rebmann, November 2011

The conventional control of the injection moulding process is based on machine variables, which cannot sufficiently characterise the course of the process. Hence, a system that controls the injection moulding process based on process variables has been developed at the Institute of Plastics Processing at RWTH Aachen University during the last years. The concept of the self-optimising injection moulding process is based on this research. This paper describes the concept of the self-optimising injection moulding process during the holding pressure phase and the idea of an extension by an incremental cooling system using small-sized cooling areas.

ON MULTISCALE SIMULATION OF THERMOPLASTIC PARTS – CALCULATING MOLECULAR ORIENTATION

Christian Hopmann | E.h. Walter Michaeli | Thomas Baranowski | Barbara Heesel, November 2011

The general aim of the Cluster of Excellence “Integrative Production Technology for High-Wage Countries” is to overcome the actual contradictions between value- and planning-orientation as well as between scale and scope in production technology. One important aspect of this approach is the development of virtual production systems to increase simulation accuracy and thereby to reduce development times and costs as well as to optimise the utilisation of material. In this paper new developments in the field of the calculation of molecular orientation are described and a validation with different experimental measurements is presented.

OPTICAL ANALYSIS OF EXTRUDATE SWELLING OF POLYMER MELTS

T. Ottnad, S. Gepp, F. Irlinger, T. C. Luth, November 2011

Miniaturization and individualization are some of the current and in future ongoing trends in producing business in general and they also are influencing the plastics processing industry. To meet the upcoming challenges a lot of research is being done in the field of micro-extrusion. This work investigates a method to identify the phenomenon of extrudate swelling of micro extruded polypropylene using an optical analyzing method. Experimental data varying the pressure is presented and an optical analysis is explained. The results show the suitability of the method but reveal that some more experiments have to be done in order to formulate clear statements.

FAILURE ANALYSIS : MIGRATION OF PIGMENTS & SLIP ADDITIVE CASE STUDIES FROM THE INDIAN SUB-CONTINENT

Francis Rodrigues, November 2011

The role of slip additives as a crucial contributing agent in product failures due to it’s migration to the surface of plastic films is explored in the context of 5 case studies highlighting different aspects of the complex interrelationships that exist between the base resins, the slip additive present in the base resins, slip agent added by the film processor in the form of masterbatches, the color pigments , processing condition / storage conditions and the products which are subsequently packed inside the flexible pouch or flexible laminates.

Three Dimensional Finite Volume Method Simulation of the Melting Zone in a Single- Screw Extruder

E. h. Walter Michaeli | Christian Hopmann | Sebastian Grammel, November 2011

This paper presents a 3D numerical model to analyze the melting process in a single-screw extruder. The fundamental equations of fluid dynamics are solved using the Finite Volume Method. The software Fluent distributed by ANSYS, Inc. was used for the numerical calculations. The computing domain is a helical-shaped screw channel. The solid bed is modeled as a fluid with a very high viscosity by adjusting the formulation of the Carreau model for temperatures below the melting temperature. The model predicts the melting length, pressure build-up and the velocity and temperature distribution within the channel.

In-Vitro Modeling of Blood Vessels

A. B. Coffey | P.R. Walsh | C. Stanley | N.E. Murphy, November 2011

There has been much research in the biomodeling of human blood vessels. Models of human blood vessels can be used for aids in future research of new medical devices that can be preliminarily tested in an in vitro setting and that could potentially lead to breakthroughs in the medical device industry. There is also the possibility to use such models for the training of surgeons, especially for complex operations, analysis of arterial diseases, and to provide the basis for hemodynamic studies. Within the last two decades accurate models have been fabricated using corrosion casts obtained from cadavers and the lost wax process. Recently, there has been a trend towards replicating the properties of blood vessels more accurately. The use of hydrogels has the potential to achieve this, as it is possible to represent properties such as viscoelasticity, anisotropy, and lubriciousness, all of which have been shown to be present in human blood vessels. The goal of this study is to apply casting methods to a core, which represents similar tortuosity and dimensions to a section of blood vessel, and achieve a low cost model that will represent the dimensional accuracy as well as representing physical properties of blood vessels as accurately as possible. In order to achieve this, poly(vinyl alcohol) (PVOH)/poly (acrylic acid) (PAA) hydrogels were chosen as a material that has the potential to match the properties of blood vessels. The PVOH/PAA hydrogels were prepared using a freeze/thaw processing technique.