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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Thermal Properties and Reactions between Poly(3-Hydroxybutyrate)/Functionalized Ethylene Copolymer Blends
Some properties modifications of poly(3-hydroxybutyrate), P(3HB), by blending with ethylene-methacrylic acid copolymers either in the acid form (I-H) or partially neutralized with Zn (I-Zn) were investigated in an internal mixer. Thermal properties and the reactions between the polymers were evaluated by DSC, SEC and FTIR. A significant change in the crystallinity degree was noticed in blends containing I-Zn. The FTIR analysis of the chloroform soluble and insoluble fractions presented evidences of chemical reactions between the components during melt mixing. A significant amount of P(3HB) became insoluble in the P(3HB)/I-Zn blend, showing in this case that the reactions have occurred in significant degree.
Thermoforming of Thermoplastic Composite Sheet - Experiments and Modeling
Thermoforming represents an alternative to more common thermoplastic composite processes such as compression molding. An important step in the development of thermoformed parts is determining formability and final part thickness. Computer simulations are a low cost technique for estimating this information. This work presents a numerical model to simulate the thermoforming of a low density thermoplastic sheet reinforced with 55% glass fiber. The model stress-strain parameters were obtained as a function of temperature using a Bruckner biaxial stretcher. Pressure-thickness model parameters were obtained using a laboratory press. The results of the simulation are compared with data from a laboratory thermoformer and a small, simple mold.
Thermoforming: From Baby Rattles to Bed Springs and Beyond
Commercial thermoforming began in the late 1800s when cellulose nitrate was first skived into sheets, then steam heated and pressed against cool metal molds to produce baby rattles, hairbrush backs, and picture and mirror cases. Technological advances languished until WWII, when heavy-gauge acrylics were formed into fighter and bomber windscreens and canopies and thin-gauge cellulosics were formed into infantry relief maps. Since then, there have been many advances in plastics, machinery, and mold technology. Thin-gauge thermoforming continues to be driven by the packaging industries. Heavy-gauge forming benefits by rapid idea-to-consumer marketing needs and by the proliferation of designer" products. This paper will reflect on some of the ideas that spurred the industry growth in the past and some concepts that may lead to important advances in the future."
Thermoforming-Stamping of Continuous Fiber Thermoplastic: Laminate Deformation Mechanisms, Microstructure and Mechanical Properties
The complexity involved in the development and implementation of thermoforming-stamping processing techniques for continuous fiber reinforced thermoplastic composites (CFRTPs) demands the understanding of the deformation mechanisms of the composite during its forming as well as the development of the matrix microstructure as a function of the processing conditions. In this paper, after a brief presentation of some of the processes used to mold CFRTP parts, an overview of the composite deformation mechanisms inherent to the forming of 2D and 3D parts is discussed. The influence of the molding temperature, pressure and cooling rate on the development of the matrix microstructure and the mechanical behavior of CFRTPs is presented.
Thermographic Characterisation of Polymers for the Laser Transmission Welding
The joining of plastics micro parts is of high importance during the production of micro systems. Combinations of similar and different thermoplastics can be welded using the laser transmission welding process. For the selection of materials suitable for this process, the knowledge of optical properties is most essential. Laser light absorption, scattering and reflection influence the energy transport during the welding process and the quality of the joint to a high extent. The measurement of the heated area on the specimen surface by infrared thermography is a suitable test method to characterise optical properties of polymers for laser transmission welding.
Thermomechanical Characterization of a Novel Series of Shape Memory Polymers
Polymers with shape memory effect have garnered increased attention recently for use in real world applications. Compared with the shape memory alloys (SMAs), the shape memory polymers (SMPs) have the advantages that: (i) the transition temperature and the rubbery modulus can be tailored according to the application and (ii) the recoverable strain can exceed several hundred percent. One of the potential uses of these interesting materials is as a medical plastic; namely, SMPs offer potential use as smart" tubes and stents for both surgical implements and implantable devices. As tubes and stents SMPs can be initially fixed in a form needed and subsequently heated for strain recovery during surgery. In our lab we have designed and prepared a new type of shape memory polymer that features good shape recovery with tailored transition temperatures and recovery strength. We present thermo-mechanical characterization data for the new materials and briefly discuss their potential uses as medical plastics."
Thermoplastic Bio-Fiber Composite: Ideation through Product Commericialization
In the last decade tremendous interest has risen in a class of materials that can be categorized as Thermoplastic Bio-Fiber composites. This paper discusses development methodology necessary to convert concepts into commercially viable materials. This development methodology includes: quality function deployment, assessment of available technologies, assessment of viable starting components, unit operations sequencing and assignment, statistical process control and commercialization. Particular attention will be paid to processing and material criteria necessary to achieve the required performance. Fibrex™ will be used as the vehicle to convey this methodology.
Thermoplastic Vulcanizates in Appliances - A Fantastic Elastic Solution
Thermoplastic Vulcanizates (TPVs) have been replacing thermoset rubber in the appliance industry for almost two decades. They continue to perform in this environment and are becoming the rubber" of choice in most new designs. Differences between TPVs and thermoset rubber will be examined as they relate to the appliance industry. Various areas such as design process and engineering criteria will be discussed to ascertain the effectiveness of each type of material. In addition we will present data to show the effectiveness of these materials in these demanding applications and environments. The paper also demonstrates proven performance in existing applications.Thermoplastic vulcanizates are the fastest growing part of the overall elastomer product group. Elastomers can be divided into two major groups thermoset rubber and thermoplastic elastomers. The majority of thermoplastic elastomers can be divided into four separate groups which are made up of chemistry differences. These groups are thermoplastic vulcanizates (TPVs) styrenic block copolymers (SBCs) thermoplastic polyolefins (TPOs) and thermoplastic polyurethanes (TPUs). TPVs are made by a process for vulcanizing the rubber phase in the alloy during mixing. The product exhibits synergistic performance capabilities.All TPVs consist of a hard and soft segment. The hard segment is generally a crystalline or amorphous polymer with a soft rubber phase incorporated in the structure. TPVs are considered elastomeric or dynamically vulcanized alloys which are partially or fully crosslinked in the rubber phase. SBCs are styrenic based and the rubber portion is not vulcanized or crosslinked. TPOs are mechanical blends of polyolefins and various types of synthetic or natural rubber which are not vulcanized or crosslinked. TPUs are a rubber material made in a chemical reactor in several forms. These products again do not contain a vulcanized or crosslinked rubber phase and are susceptible to polymer degradation in a high moisture environments.All of these polymers have their fit as an ideal candidate for many applications. We will primarily focus on the opportunities and benefits offered by thermoplastic vulcanizates in the appliance market."
Thick Composite Extrusion Process
Production of large thermoplastic composite products such as railroad cross ties, marine pilings and utility poles requires an extremely long cooling time. Undesirable internal shrinkage voids from the core of the extruded product create poor physical appearance and concern about the physical properties.Cross head extrusion allows the product to be cooled in layers, thereby reducing cooling time and internal imperfections. Elaborate internal core design increases the surface area for faster heat transfer, allowing for higher extrusion rates of the inline compounding extruders. Fusible polymers in the interfacing layers permit interlayer bonding. This bonding enhances shrinkage compression of the inner core. This internal compression will stiffen the resulting product.Additional cost savings can be achieved by using off-spec resins and low cost fillers at a high loading in the core. Twin-screw compounding extruders are well suited to accomplish this compounding step in line at low die pressures. The removal of volatiles by means of vacuum venting is essential to produce a solid profile.Cross head extrusion also allows the application of high performance weathering surfaces to enhance product performance. In the following paper, the thick composite extrusion process is demonstrated with the development of railroad ties as a replacement for conventional hardwood timbers.
Three Approaches in Utilizing High Power Diode Laser to Join Thermoplastics
As we enter the micro age, the new challenge in the plastics industry is to manufacture and assemble smaller and smaller parts. Standard joining methods, such as adhesives, fasteners, ultrasonic or vibration welding may no longer suffice.Conventional lasers, such as the CO2 and Nd:YAG, have developed into important tools for the metals industry but their use to the plastics industry is limited to the cutting and scribing of plastics. Diode lasers have a shorter wavelength and have now reached output powers that allow them to be used to produce a controlled melt, or welding, of thermoplastics. Weld lines as narrow 0.1 mm (0.004 in.) have been achieved using diode laser welding systems.This paper reviews the capabilities of the diode laser welding process, and expands on three methods of delivering the diode laser energy to the work piece.
Three-Dimensional Cae Analysis of Underfill Flow of Flip-Chips
This paper presents a true three-dimensional simulation of the underfill flow in the encapsulation of flip-chips. The SIMPLE-based finite volume method (FVM) is combined with the volume of fluid (VOF) method to solve the two-phase flow field and to track the advancement of the resin front during underfilling process. Since the underfill encapsulation is driven by the capillary force, the continuum surface force (CSF) model is employed in the present approach to calculate the surface tension at the resin front surface. In addition, the chemorheology of the encapsulant is also included to consider simultaneously the effects of temperature, shear-rate and degree-of-cure on the underfilling patterns. Several test examples with different dispensing locations or molding temperatures are analyzed to demonstrate the capabilities of the present approach.
Through-Transmission Infrared Welding (TTIR) - Filter Media
TTIR heating is more selective if filter media are used to remove unwanted light wavelengths from the spectrum of quartz-halogen lamps. Moving sheets of the non-absorbing polymer are excellent filters when interposed between the lamp and the workpieces. This paper describes an evaluation of different filter materials and filter thickness on heating selectivity and presents a method for quantifying filter performance for an acrylic to polycarbonate weld joint. Selectivity numbers (SNs) are defined here as the number of degrees of heating selectivity that are observed per second of heating. While the best filter material is another sheet of the non-absorbing polymer, some very good performance was seen for liquid filter media that are safe and easy to use. SNs greater than 4 are needed to achieve welds with minimal distortion and several liquid materials were found with SNs from 10 to 15°C/sec.
Tie Rod Strain Incorporated as Part of an Adaptive Process Monitoring Device
Introduction In today's industry, the number one priority is time. The faster a product reaches the market, the more profit a company can make. By utilizing a cavity pressure transducer in a mold, the quality of a finished part can be predicted. Based on this information, proper adjustments can be made to the process to correct quality issues and speed up rates of production. This works well, but an expensive transducer is required for each mold. With the aid of a newly redesigned device, it is believed that time and money can be saved in processing a product. Less scrap will also be generated by the implementation of such a monitoring device. This study is a continuation of previous research performed by Juraj Ulik, ANTEC 1999 and Scott M. Frantz, ANTEC 1993, which established that there is a relationship between tie rod bending and hold pressure. Previous research was hindered greatly by a transition noise" problem. The device has been redesigned to maximize the mechanical gain and minimize the amount of noise. Incorporating this tie rod device into an adaptive process monitoring system is the ultimate goal."
To Refine Mesh or Not to? An Innovative Mesh Generator for 3D Mold Filling Analysis
True three-dimensional (3D) mold-filling technique has been a research hotspot since 90s. Important and interesting 3D phenomena such as inertia, corner effect, splitting flow, as well as fiber orientation can only be captured by the true 3D approach. On the other hand, pre-processing of the geometry model before analysis is still a rate-determining step in a CAE analysis. Poor mesh distribution will lead to loss of resolution in the 3D solver; extensive meshing will lead to huge number of elements and long CPU time that is impractical for designers. In additional to these challenges, thin-wall structure of injection molded part will generate poor aspect-ratio 3D elements for most commercial mesh generators. Therefore, geometry modeling is even more crucial in 3D than the traditional 2.5D shell element approach. In this work, an innovative mesh generator is developed to relief the effort in 3D mesh generation. This approach combines the flexibility and robustness of non-structure tetra mesh and the good boundary-layer-resolution of prism mesh. Numerical experiments prove this new approach is promising for 3D mold filling analysis for thin-wall parts.
A Tough and Flexible Syndiotactic Polypropylene - Actylic System Made via in Situ Polymerization
Blends of syndiotactic polypropylene (sPP) with high molecular weight acrylic monomers were prepared by extrusion blending to obtain polymer/monomer (P/M) pellets. These pellets were then converted into sheet form using flat die extrusion. Sheets of P/M material were continuously thermally cured to high conversion. The effect of processing conditions on the behavior of the resulting uncured and cured sheets was investigated. The effect of the amount and composition of the monomer mix on the morphology and physical properties of the resulting cured sheets was studied. Processing conditions and compositions were identified which produced cured sheets showing reduced modulus and improved tensile properties, relative to sPP. The in situ polymerization produced a two-phase system with very small acrylic domains. Products with good clarity have been obtained.
Toughness Response of Amorphous (Co)Polyesters Using the Essential Work of Fracture Approach
The essential work of fracture (EWF) is an easy to perform approach to determine the plane stress fracture toughness of ductile polymeric sheets and films. Amorphous polyesters and copolyesters are the most suitable model materials for EWF studies as they undergo full ligament yielding prior to the subsequent necking+tearing process. This behavior allowed us to partition between the yielding- and necking-related EWF parameters. The EWF method was applied to study the fracture behavior of amorphous (co)polyesters as a function of external (testing-related) and internal (material-related) parameters. It was claimed that the yielding-related specific essential work of fracture term represents the inherent toughness of the materials accordingly. This material parameter is controlled by characteristics of the entanglement network which is in close analogy with the toughness response of chemically crosslinked rubbers.
A Tubular Melt Extrusion of Poly(Vinylidene Fluoride): Structure/Process/Property Behavior as a Function of Molecular Weight (Mw)
Five poly(vinylidene fluoride) (PVDF) resins, R1-R5, of narrow molecular weight distribution (ca. 2.0) but of different weight average molecular weights Mw’s (85 – 250 Kg/mol) were melt extruded in tubular film form with a blow up ratio (BUR) of unity. The objective was to produce a stacked lamella structure that could serve as a precursor for a later process step that converts this film into a microporous membrane. Four of the resins were in pure form R1-R4 whereas the fifth, R5, contained a small amount of plasticizer to facilitate processing due to its high molecular weight. Comparisons were made of how Mw influences film morphology under a given set of process conditions. WAXS systematically showed an increase in crystal orientation as Mw increased for fixed conditions. A Carreau-Yasuda fit of the melt rheological data provided a characteristic relaxation time and this variable was correlated to the respective morphologies produced. It was shown that nearly spherulitic-like textures could be induced with the lowest Mw material whereas highly concentrated fibril nucleated morphologies were promoted with the highest Mw under identical process conditions. It was demonstrated that by blending the resins, R2 & R4, the desired stacked lamellar structure could be fine tuned with regard to morphological features.
Twin Screw Extrusion Guidelines for Compounding Nanocomposites
Nancomposite polymer compounds are poised to have a significant impact on the reinforced polymer market. A relatively small loading of properly dispersed treated clay can yield substantial improvement in a polymer's thermal, mechanical and barrier properties, as well as flame resistance, and abrasion resistance. Until recently, most nanocomposite development has focused on determining proper treatment for the clay to make it more compatible with the base polymer and thus improve the ease with which it can be dispersed. However, increasingly more effort has been extended to development of a direct compounding production methodology that will effectively disperse and exfoliate the clay. Of course, clay preparation is still extremely important, but proper design and operation of the compounding system is critical. This presentation will review the design flexibility associated with co-rotating twin-screw extruders and discuss key unit operations necessary to obtain well dispersed clay.
Twin Screw Extrusion of Polyurethane Nanocomposites
Triton Systems, Inc., has fabricated polymer layered silicate nanocomposites excellent dispersion of layered nanosilicates within a wide range of thermoplastics through inorganic surface chemical modification and polymer processing. These materials, including those with polyamides, polyolefins, polyesters, and polyurethanes result in dramatic improvements in mechanical, flammability, and gas barrier properties, while maintaining processibility for extrusion, injection molding, and blown film applications. This study aims to investigate the effects processing parameters have on thermoplastic polyurethane-nanocomposites. The optimization of the processing temperature, shear, and nanosilicate loading level results in materials with superior mechanical strength, toughness, solvent resistance, and hydrolytic stability.
Twin-Sheet Thermoforming of Dissimilar Materials
The effects of material properties in the simultaneous twin-sheet thermoforming of dissimilar materials were evaluated using a selection of 1 mm thick sheets and a test mold. Forming of dissimilar sheets required major modifications to parameters recommended for similar sheets. For this system, increasing the sheet temperature provided the greatest improvement in seal strength. Mold temperature had little effect of seal strength whereas air temperature and pressure had no processing window. The seal strength was sensitive to the solubility parameter mismatch and difference between sheet temperature and critical transition temperature. When the former was large and latter was small, seal strength was inadequate. Of the materials used in this study, polycarbonate and ABS exhibited the highest seal strengths.
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