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
In Situ Study of Microstructure Change during Polymerization of Thermotropic Liquid Crystalline Polymer
Si-Xue Cheng, Tai-Shung Chung, Sanjoy Mullick, May 1999
Microstructure change during polycondensation reaction for thermotropic liquid crystal polymer (LCP) poly(p-oxybenzoate/2,6-oxynaphthoate) was in situ studied by novel thin film polymerization technique. The polymerization was conducted on the heating stage of a microscope. The reaction process was observed in situ through the polarizing optical microscope. Reaction system started from a homogenous phase and changed into a heterogeneous one. Following sequence of morphological changes during the entire reaction was observed: generation of anisotropic phase, coalescence of liquid crystal (LC) droplets, formation of schlieren texture, annihilation of disclinations and formation of banded texture. Kinetics of the LC texture formation was investigated. The number of defects decreased with increasing reaction time through coalescence and annihilation. Annihilation process was studied. Copolymer was characterized by FTIR.
Thermal Decomposition Behavior of High Performance Liquid Crystalline Polymers Studied by TGA and TG-IR
Xing Jin, Tai-Shung Chung, May 1999
The thermal decomposition behaviors of three liquid crystalline polymers were investigated. Namely, Polyester A is composed of p-hydroxybenzoic acid (HBA) and 2,6- hydroxynaphthoic acid (HNA) monomer units with a HBA/HNA molar ratio of 73/27; Poly(ester-amide) B is made of HNA, p-hydroxyl acetaniline (HAA), and terephthalic acid (TA) units with a HNA/HAA/TA molar ratio of 60/20/20; Polyester B is synthesized from HBA, biphenol (BP), and TA units with a HBA/BP/TA molar ratio of 2/1/1. The apparent activation energies (Ea) associated with the thermal degradation processes are determined by the Ozawa and Kissinger methods, using data from dynamic thermogravimetric analysis (TGA) experiments. The magnitudes of the Ea for these LCPs follow the order: Polyester B > Polyester A > Poly(ester-amide) B in both air and N2 environments. The stability of the samples at the beginning of the degradation processes follows the same order. Random chain scission and hydrogen abstraction are the main degradation mechanisms in N2 atmosphere. For all three LCPs, CO2 is the dominant degradation product during the entire testing periods in both N2 and air environments and the change of CO2 amount is consistent with the degradation rate. Relatively high percentages of O and N elements were found in the residues after TGA experiments in N2.
Surface Energy Investigation of Organic Light Emitting Polymers and its Substrates
Kui-Xiang Ma, Chee Hin Ho, Tai-Shung Chung, May 1999
The sessile-drop contact angle technique and the Lifshitz-van der Waals Acid-Base theory were utilized to investigate acid-base interactions and non-polar interactions of a polymer light emitting diodes (PLED) material, MEH-PPV. The same methodology was also applied to PLED substrate material, e.g., ITO films, without and with solvent cleaning treatments. Surface energy components of MEH-PPV and ITO films were calculated from the contact angle data with the 3-liquid approach. With above determined surface energy components, we further estimated the thermodynamic work of adhesion between the two solid films, MEH-PPV and ITO. Experimental data suggested that after solvent cleaning treatments, the Lifshitz-van der Waals parameter of surface energy (?LW) and hence the total surface energy of ITO films tended to increase. The methanol-treated ITO has the strongest adhesion with MEH-PPV in terms of acid-base work of adhesion, in other words, methanol is the most effective solvent in our studies for ITO films.
Thermal Degradation of Polyimide and Polyamide Liquid Crystalline Polymers
K.P. Pramoda, T.S. Chung, S.L. Liu, H. Oikawa, A. Yamaguchi, May 1999
The thermal stability of a polymer is its most important property for applications in various fields. This paper reports some studies of the thermal degradation behaviour of polyimide and polyamide liquid crystalline polymers (LCP) in air and inert environments. It focusses on the determination of degradation kinetics and the evolved gas analysis of these LCPs. Characterization was done using thermo-gravimetric analysis (TGA) coupled with Fourier Transform Infra-Red (FTIR) spectroscopy. Observations indicated one-step degradation process in inert environment, while two steps were noticed in the case of air. The activation energies for these degradation processes were computed using Kissinger and Ozawa methods. Decomposition results show that polyamide is much less thermally stable than polyimide. Evolved gases are found to be H2O, CO, CO2 and various hydrocarbon fragments.
Evolution of Surface Free Energy during Thin Film Polymerization of Main-Chain Liquid Crystalline Polymers
Tai-Shung Chung, Kui-Xiang Ma, May 1999
By applying thin film polymerization technique and the Lifshitz-van der Waal-Acid-Base theory, we have determined, for the first time, time evolution of contact angle and surface free energy during the polymerization (or molecular weight increase) of liquid crystalline poly(p-oxybenzoate/2,6- oxynaphthoate). Surface free energy components of these main-chain liquid crystalline copolyesters were calculated from contact angle measurements using a Ramé-Hart goniometer and 3 liquids (water, glycerol and diiodomethane). Experimental data suggest that the Lewis-base parameter (?-) of poly(p-oxybenzoate/2,6- oxynaphthoate) decreases rapidly with progress of polymerization, while the Lewis acid parameter (?+) and the Lifshitz-van der Waals parameter (?LW) do not vary significantly.
Examination of Starve-Fed Single Screw Extrusion in Conventional and Barrier Feed Screws
M.R. Thompson, G. Donoian, J.P. Christiano, May 1999
An investigation of starved-fed single screw extrusion was initiated to study its improved mixing capabilities for the compounding of filler. Experiments were carried out in a 63.5 mm single screw extruder, examining the effect of degree of starvation on a conventional and barrier feed screw. Interest was focused on the mixing/melting mechanism of starved-fed solids-conveying as it affects the size and number of filler agglomerates observed in the extrudate. Both screws showed improved mixing quality with increased starvation. Trends in pressure, torque and power efficiency reflected the improvement in mixing.
Developments in High Strength I-PP: Technology Properties, Applications and Markets
Manfred Rätzsch, Ulf Panzer, Achim Hesse, Hartmut Bucka, May 1999
In this paper the manufacture of a new family of high melt strength polypropylenes (HMS-PP), its benefits and application in the field of foam extrusion are discussed. A brief introduction into general pathways of influencing melt strength shows that it is the combination of both, a high strength and high drawability of the polymer melt (due to the introduction of some long-chain branches into the polymer structure) which is the main characteristic of these special materials. The rheological behavior is due to a special post polymerization (Daploy) process which introduces long-chain branches into the propylene polymer by comonomer bridging. The presentation of general properties resulting from the modified polymer architecture is followed by the discussion of benefits HMS-PP gives to polymer processing and to final material properties. In particular it is possible to manufacture non-crosslinked and thermoformable PP foams with a density range down to 0,1 g/cm3 and below by foam extrusion processes similar to the known from polyethylene and polystyrene. Main applications are lightweight packaging trays, beakers and containers as well as technical foams for automotive applications such as headliners, door liners, acoustic panels. In summary it is shown that the new family of high melt strength PP is a challenge and chance for PP to improve in existing and to enter into new polymer processing technologies, applications and markets.
A Knowledge-Based System with Fuzzy Logic for the Tuning of Injection Moulding Machines
Nikos G. Pantelelis, Andreas E. Kanarachos, Miltiadis M. Procos, May 1999
The proposed system aims at a) helping injection moulders to tune the process parameters of an injection moulding machine, b) storing knowledge and experience that can be used later and c) creating an integrated tool with information on materials, process parameters so it etc. The system is based on general guidelines coupled together with expert rules from the users and a fuzzy logic system which is responsible for the intelligent communication with the users. Results show the way the system operates in an industrial environment.
Experimental Study of a New Dispersive Mixer
Chris Rauwendaal, Antoine Rios, Tim Osswald, Paul Gramann, Bruce Davis, Maria del P. Noriega, Omar A. Estrada, May 1999
New dispersive mixing technology for extruders and mixing devices (1, 2) is based on creating strong elongational flow to achieve efficient dispersive mixing. These mixers are designed so that all fluid elements pass through the high stress regions several times. One version of the new mixer, CRD-4, was tested on a modular 45 mm extruder using a dryblend of polyethylene and polystyrene. The CRD-4 mixer was tested against a Leroy/Maddock mixer and a Maillefer mixer. The mixing capability was studied by microscopic analysis of the domain sizes of cross sections of extruded strands. The mixer performance was also analyzed with respect to pressure profiles, characteristic curves, and melt temperature distribution. It was found that the CRD-4 mixer achieves a fine level of dispersion under most circumstances. The Leroy/Maddock mixer has limited dispersive mixing capability at low screw speed; however, its dispersive mixing capability is better at high screw speed. The CRD-4 mixer is designed with forward pumping capability. As a result, the output-pressure characteristic of a screw with a 6D CRD-4 mixer is essentially identical to the same screw with the mixer replaced by a conveying section.
The Adjustable Grooved Feed Extruder
Chris Rauwendaal, Robert Sikora, May 1999
Grooved feed extruders have been around since about the 1960s. These extruders offer considerable advantages over conventional extruders, such as higher throughput, better stability, and the ability to process very high molecular weight polymers. There are some important disadvantages as well, for instance, higher motor load, wear is more likely, high pressures in the grooved region, and the screw design has to be adapted. The disadvantages of the grooved feed extruder disappear when the grooved feed extruder is made with a mechanism that allows adjustment of the groove depth. This paper will report on the development of grooved feed extruders that incorporate an adjustment mechanism that allows the depth of the grooves to be changed, during actual operation, from zero to full depth. Operational data from actual extrusion experiments are presented.
Use of Stereolithography for Extrusion Dies
A. Munot, J.L. Mead, S.A. Orroth, R.G. Stacer, May 1999
Stereolithography has been used for many years to develop prototype parts. This is a good method for evaluating preliminary designs, but restricts the fabrication material to that used in the stereolithography equipment. It is more desirable to produce molds using stereolithography and prepare parts in the material of choice. This method has been successfully used for injection molding, but has not been evaluated for use in extrusion. This work examined the use of die inserts made by stereolithography for profile extrusion. An existing die was modified to allow epoxy inserts to be placed in the die so that the dimensions of the profile could be modified quickly without preparing a new metal die, but rather changing to a new epoxy die insert. This technique allows new profiles to be rapidly evaluated. In this work the lifetime of the epoxy inserts was determined for varying profile cross-sections. The effect of temperature and pressure on the lifetime of the epoxy die inserts was also measured.
Trade-Offs in Blown Film Processing-Structure-Property Behavior of LLDPE Type Resins from Chromium, Metallocene and Ziegler-Natta Catalysts
Ashish M. Sukhadia, May 1999
Linear low density polyethylene (LLDPE) resins are a very important class of resins for the blown and cast film industry. In this paper, the processing-structure-property behavior and trade-offs observed with three LLDPE resins made from chromium, metallocene and Ziegler-Natta catalysts were examined and critically compared. First, their basic molecular and rheological properties were examined. The blown film performance of these resins was examined with respect to the effects of film thickness and molecular orientation on film properties. The processability of these resins was compared through an examination of the typical extrusion and film blowing parameters. The extensional viscosity behavior of these resins using Cogswell's converging flow analysis was compared. Finally, an attempt was made to highlight the advantages and disadvantages of each resin type as they apply to blown film applications. The overall objective, and hope, of this work was to demonstrate that LLDPE resins from the various catalysts are dramatically different in nature, thereby resulting in different trade-offs with respect to their processing - structure - property behavior in film blowing.
Time-Temperature-Stress Correspondence
Witold Brostow, Nandika Anne D'Souza, Robert D. Maksimov, May 1999
We present methods of calculation of mechanical properties (stress relaxation. creep. dynamic mechanical. tension. etc) of polymers based on the time t temperature T correspondence. The equations are applicable in wide temperature ranges and require relatively small amounts of experimental data. The conventional wisdom says that the correspondence principle is applicable to one-phase materials only: we prove otherwise since successful applications of our formulae include also notoriously multi-phase polymer liquid crystals (PLCs). Our equation for the temperature shift factor is used in conjunction with the Hartmann equation of state (valid for polymer solids as well as for melts). Since the origin of the time temperature correspondence lies in free volume, we explore also methods of free volume variation other than temperature manipulation. In particular. we report progress achieved in using the time t stress ? correspondence principle.
Ranking of Correction Methods - How Effective Are They?
A. Goettfert, E.O. Reher, I.M. Balagula, May 1999
Capillary rheometry is the most popular rheological measurement technique for polymer melt characterization. One of the reasons it is used so frequently is the system's simplicity compared with a rotational rheometer. However, the analysis and interpretation of the raw experimental data (pressure drop as a function of piston velocity) can be time consuming, before the viscosity function can be determined in absolute terms. The Bagley-Correction to determine the entrance pressure losses and the Rabinowitsch-Weissenberg-Correction to determine the true shear rate at the wall (caused by the difference between Non-Newtonian flow and Newtonian flow), are the two classic methods for the determination of the true viscosity function. The failure of adhesion of the polymer melt at the capillary wall, encountered as slippage, asks also for correction. Viscous heating due to dissipation can be significant for high molecular weight polymers processed at high shear rates and asks also for a correction of the viscosity function. The correction methods mentioned will be analyzed with respect to their influence on the viscosity function. It is a goal of this work to provide a quantitative ranking of the methods in question for selected polymers.
Pressure Shear Pulverization (PSP) Process for Thermoplastic and Thermoset Waste
Tapan Patel, Fyodor Shutov, May 1999
A novel process of pulverization known as Pressure Shear Pulverization (PSP) process has been developed for thermoplastics (PE, PP, PS, PVC, PA, PET and/or their mixtures), thermosets (polyurethanes and phenolics), composites, and various blends (thermoplastics and paper). PSP is a proprietary, non-extrusion process and is realized inside a specially designed pulverization head. It is very different from cryogenic grinding, various versions of solid state shear extrusion (SSSE), and other size reduction processes. PSP has several advantages, namely, high output, low specific energy consumption, and low cost of pulverization head. PSP process is capable of producing coarse to very fine particles by manipulating the processing parameters. This paper deals with the development of pulverization of pre-consumer cross-linked LDPE foam waste and LDPE/Paper mixture by PSP process. As a model system, the processibility and properties of virgin LDPE have been studied. Physical properties of LDPE foam waste and polymeric powder have been determined and compared to understand the behavior of polymer under the combined action of thermally and mechanically induced stresses. Lab-scale and pilot-scale PSP machines have been designed and constructed.
Integrated Use of Educational Software for Product/Process Design
J.-M. Charrier, B. Sanschagrin, May 1999
As the use of plastics products in numerous areas continues to rise rapidly, a growing number of personnel in companies, as well as students from academic institutions, have a need for efficient and user-friendly educational tools to acquire the basic knowledge necessary to either undertake a conversion to plastics, or start a career in plastics. Plastics products have to be designed and then manufactured. Probably more than with any other material, the geometric design, material selection and manufacturing must be integrated to get good and economical products. This is related to the wide variety of types and grades of plastics, associated with a very wide variety of applications using a wide variety of distinct processing techniques. We have used our long educational experience in academic environments, as well as our extensive involvement with professional/industrial seminars, to develop a series of interactive CBT programs" (Computer-Based Training programs) which address different needs and complement each other. In this presentation we will emphasize the simultaneous use of the various software to quickly acquire knowledge related to several specific plastic products. Since the softwares were designed to be used in either instruction mode (instructor in classroom situation) or in self-study mode (individuals on their own) we will address these two distinct cases. A brief description of major features of four of our Windows-based softwares is first presented in the following."
Single-Site Catalyzed Polyolefin for Fresh-Cut Produce Packaging - A Comparison between Monoextruded Blends and Coextruded Film
V. Patel, S. Mehta, S.A. Orroth, S.P. McCarthy, May 1999
Single-site and Metallocene catalyzed polymers, such as polyolefin plastomers (POPs) are unique due to their narrow molecular weight distribution (MWD) and comonomer distribution (CD). These factors can dramatically enhance the properties such as toughness, clarity, sealability and oxygen transmission rate. While linear low-density polyethylene (LLDPE) exhibits excellent physical properties and drawdown capability, the combination of both resins via blending or coextrusion provides a mix of film properties very difficult to achieve with individual components. This study examines the performance of monoextruded blown film made from blends of POP1 (0.9038 gm/cc density) and POP2 (0.8996 gm/cc density) with LLDPE (0.922 gm/cc), versus coextruded film made of POP1 40 % (1.0 mil) / LLDPE 60 % (1.5 mil). In addition, a bimodal resin (0.9175 gm/cc) was also compared with the above materials for the fresh-cut produce packaging application. Both monoextruded and coextruded films can be used for modified atmosphere packaging (MAP) of fresh-cut produce. Coextruded film is the best option for low respiration products because of its excellent sealing performance over other monoextruded films. The end use requirements at the reduced cost are better satisfied by bimodal resin film compared to monoextruded films made of POP1 and POP2 with higher LLDPE contents. Monoextruded blends of POPs with lower LLDPE content (< 40 %w) exhibit most of the property requirements of moderate to high respiration rate fresh-cut produce.
Experimental Studies of Inhomogeneous Post-Yield Deformation in LLDPE Films
Amiel B. Sabbagh, Alan J. Lesser, May 1999
Heterogeneous deformation in the form of dilatational bands is observed under certain biaxial stress states which closely resembles uniaxial necking in LLDPE blown films. The formation and orientation of dilatational bands is a function of film morphology and stress state. The dilatational bands form, with their length aligned with the machine direction (MD) of the film, under equibiaxial stress states and nonequibiaxial stress states when the higher principle stress is coincident with the transverse direction (TD). However, homogeneous deformation is observed if the higher principle stress is coincident with the MD. Similarly, uniaxial specimens show necking when the stress is applied in the TD and affine deformation when the stress is applied in the MD. Neck boundary propagation under uniaxial loading is only due to consumption of undrawn material, while dilatational band boundary propagation under an equibiaxial loading also includes simultaneous continued deformation of the drawn material.
Application of Iodine-Doped Poly(p-Phenylene) Langmuir-Blodgett Films as Homogeneous Alignment Layers
Scott C.-J. Tseng, J. Adin Mann, Jr., Jerome B. Lando, May 1999
Poly(p-phenylene) (PPP) ultra thin films oriented by the Langmuir-Blodgett technique were applied as homogeneous alignment layers and provide some orientation. Poly(2,5-dicarboxyl-1,4-phenelene) (PDCP) and o,o',o'-trihexadecanoyl-triethanolamine (NIII) were used to form the precursor salt, which was transformed into PPP LB films via pyrolysis. A pretilt angle of 0.2° was measured via crystal rotation method on antiparallel liquid crystal cells with PPP LB films as the homogeneous alignment layers. Thermodynamic properties of these Langmuir films at the air-water interface such as their isotherms and creep test were studied. These LB films were characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, electron diffractometry and wide angle X-ray diffractometry. Room-temperature electrical conductivity measurements were performed on the high-temperature iodine-doped PPP LB films via a four-probe method.
Novel Stress/Strain Sensors Based on the Mechanochromic Properties of Liquid Crystalline Polydiacetylenes
Suppalak Angkaew, Pak Meng Cham, Jerome B. Lando, Brian P. Thornton, Roberto Ballarini, Robert L. Mullen, May 1999
Polydiacetylenes obtained from a series of liquid crystalline diacetylene monomers and macromonomers (polymers containing diacetylene groups) exhibit mechanochromic behavior in which their original color changes upon exposure to mechanical force (tensile or shearing). These polymers have been used to develop novel, intrinsic stress/strain sensors based on their mechanochromism. Our study of morphology, crystallographic structure, and optical properties showed that the mechanochromism corresponds to structural phase transitions from crystalline to liquid crystalline phase. This paper will also discuss the relationship between chemical structure, optical properties and mechanical properties of these PDAs.
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