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Conference Proceedings
The Effects of Process Conditions, Nominal Wall Thickness, and Flow Length on the Shrinkage Characteristics of Injection Molded Polypropylene
Patrick M. Gipson, Peter F. Grelle, Brent A. Salamon, May 1999
The use of polypropylene in injection molding large parts, for automotive and durable applications, has increased due to down engineering from high performance engineering thermoplastics such as acrylonitrile butadiene styrene (ABS) and polycarbonate/ABS (PC/ABS) blends. Due to polypropylene's high shrinkage characteristics, the molding conditions used to fabricate polypropylene parts are very critical since they can affect post-mold shrinkage ultimately affecting final part dimensions. This paper will address issues on how injection molding conditions, nominal wall thickness, and flow length will affect the shrinkage characteristics of polypropylene.
A New, Unique Thermoplastic Elastomer with Enhanced Properties
Johanna Lampinen, Optatech Corporation, May 1999
A new polyolefin-polyacrylate elastomer based thermoplastic elastomer has been introduced on the market. It is produced by a method called solid state grafting and it can be further modified by compounding. Rigid polypropylene or polyethylene copolymer constitutes a continuous phase in which soft crosslinked polyacrylate elastomer is dispersed. The elastomer is a fundamentally new concept offered to compounding companies and the present three base polymer grades provide new alternatives with their moderate price and unique properties. The chlorine-free elastomer offers excellent oil and gasoline resistances combined high flex resistance and good weather resistance. It has also good adhesion to paints, polyethylene, and polypropylene, and the surface smoothness is excellent.
The Effect of Thermoplastic Olefin (TPO) Morphology on Friction Induced Paint Damage
Rose A. Ryntz, Dennis Mihora, May 1999
Damage to painted automotive plastics induced by compressive shear continues to plague the material engineer involved in the design and selection of fascias, bumpers, body-side moldings, and the like. Studies conducted to determine the root cause of such failures have focused on the effects of paint and the role of friction in the compressive shear failure of painted thermoplastic olefins (TPOs), which are blends of poly(propylene) and elastomer. The study described herein probes the effects of TPO morphology on compressive shear damage resistance of painted TPO substrates. Morphological variations within the subsurface of the TPO substrate caused by compositional as well as injection molding variations will be described. The apparatus utilized to impart the damage, SLIDO, and the variables studied affecting the damage, e.g., acceleration, velocity, temperature, and loading, will be discussed.
Extrudate Prediction and Die Design of Profile Extrusion
Woei-Shyong Lee, Sherry Hsueh-Yu Ho, May 1999
The objective of this study is to investigate the die swell behavior of a polymer melt and to predict the final shape of the polymeric extrudate formed by profile extrusion. The finite element method was used to simulate a Newtonian fluid passing through a die with the geometry of a quarter ring profile. Based on the swell studies, a modified die was designed to produce a quarter ring profile extrudate. Polystyrene pellets were chosen to perform the profile extrusion experiments. The theoretical and experimental results confirm that suitable operating conditions and die geometry can improve the die swell phenomena. The die swell ratio becomes smaller as the melting temperature and melting residence time are increased. As the die length is increased, the die swell ratio is lowered. According to the prediction of die geometry, an extrudate with the desired profile can be made precisely.
Material Screening Process for Medical Film Applications
Jerry Davis, Joyce Silvestri, Sr., May 1999
The dynamic medical market in the '90's is experiencing rapidly changing, highly specialized therapies and treatments. These products require device components and container systems with narrow product definitions. To meet this demand, the leading edge companies continue Tto develop methods that will shorten their development cycle One cornerstone in cycle time reduction is having an established Product Development Process encompassing material screening. The process integrates identification of team membership, product definition, design reviews, and screening requirements. The effective process will optimize utilization of the human and financial resources of an organization.
Compatibilization of Polypropylene/Polyethylene Terephthalate Blends and Composites
Kimberly M. McLoughlin, Sharon Jones Elliott, Edwin B. Townsend IV, May 1999
Traditionally, polypropylene (PP) mechanical properties have been enhanced by compounding PP with inorganic fillers. Recently, fillers have been added to PP-based polymer blends to create composites with even greater ranges of properties. In a previous study, we examined glass-filled PP compatabilized using maleic anhydride-grafted polypropylene (PP-g-MA). We reported adding a small percentage of polyethylene terephthalate (PET) to those materials enhances mechanical properties. Here, we confirm that adding a small amount (15% or less) of PET to glass-filled PP containing PP-g-MA yields significant increases in tensile strength and flexural modulus. We also demonstrate that the property enhancements achieved by adding PET to glass-filled PP can be used to reduce the amount of glass in the system without significantly reducing mechanical properties
Extrusion of PE/PS Blends with Supercritical CO2 in a Twin-Screw Extruder and a Twin/Single Tandem System
Minhee Lee, Costas Tzoganakis, Chul B. Park, May 1999
The effects of dissolved supercritical carbon dioxide on the viscosity and morphological properties were investigated for polyethylene, polystyrene and their blends in a twin-screw extruder and a twin/single screw tandem system. The viscosities of the polymer/CO2 and the blend/CO2 solutions were measured using a wedge die mounted on the twin-screw extruder. The effect of CO2 on the morphology of PE/PS blends was investigated using a twin/single screw tandem system. This system allowed for preferential dissolution of the CO2 into the matrix and/or dispersed polymer phase. By introducing devolatilization to the tandem system, the morphological behaviors of PE/PS blends were investigated on unfoamed filaments.
The Effect of Process Parameters on the Modulus and Structure of PET/LCP Blends
Zhigang Li, Kwabena A. Narh, May 1999
In this study, the correlation between structure development during injection molding, and the modulus of injection molded PET/LCP blends were studied. Process parameters such as injection speed and melt temperature were varied to determine the effect of these parameters on the modulus and structure of the blends. The skin/core structure in the cross section of injection molded samples was observed with optical microscope set up. Injection molding experiments show that the thickness of skin layer increases with decreasing injection speed and decreasing melt temperature. The trends in morphological developments in the injection molded specimens can be correlated with the measured tensile moduli.
Polypropylene Blanks and the "If You Can't Beat Them Join Them" Approach to Copolymerizing Functional Olefins with Metallocene Catalysts
Bruce M. Novak, Mitsuru Nakano, Hiromitsu Tanaka, May 1999
Although the incorporation of polar monomers into coordination polymerization systems has been an active area of research for over forty years, no satisfactory solution to this problem has emerged. The reasons for this are many and include poisoning of the metal centers, disparity in reactivity and electron distribution between comonomers, and the formation of lower energy intermediates incapable of inserting olefins (e.g., enolates in the case of (meth)acrylate comonomers). Two of our approaches to overcoming these global limitations will be discussed. The first involves completely circumventing the problem by (co)polymerization of allene to form unsaturated precursor polymers (polypropylene blanks") that can be later reduced and elaborated with functional groups."
Polypropylene Blanks" and the "If You Can't Beat Them Join Them" Approach to Copolymerizing Functional Olefins with Metallocene Catalysts
Bruce M. Novak, Mitsuru Nakano, Hiromitsu Tanaka, May 1999
Although the incorporation of polar monomers into coordination polymerization systems has been an active area of research for over forty years, no satisfactory solution to this problem has emerged. The reasons for this are many and include poisoning of the metal centers, disparity in reactivity and electron distribution between comonomers, and the formation of lower energy intermediates incapable of inserting olefins (e.g., enolates in the case of (meth)acrylate comonomers). Two of our approaches to overcoming these global limitations will be discussed. The first involves completely circumventing the problem by (co)polymerization of allene to form unsaturated precursor polymers (polypropylene blanks") that can be later reduced and elaborated with functional groups."
Cationic Transition Metal and Main Group Metal Alkyl Complexes in Olefin Polymerization
Richard F. Jordan, May 1999
Metallocene catalysts, i.e. olefin polymerization catalysts derived from Cp2ZrX2 and other metallocenes, polymerize olefins with high activity (typically >106g/(mol Zr*h*atm)) and, with proper tuning of the Cp ligand structure, highl selectivity. Metallocene catalysts display single-site behavior and produce polymers with narrow molecular weight and composition distributions. The active species in these catalysts are Cp2Zr(R)+ cations, which are generated from Cp2ZrX2 precursors by alkylation and R-/X- abstraction. The important activators include methylalumoxane (MAO), strong Lewis acids such as B(C6F5)3, and trityl, bulky ammonium and ferrocenium salts of B(C6F5)4-. It is critical that the activator create or contain a non-reactive, weakly-coordinating anion to stabilize the electrophilic Cp2Zr(R)+ cation. Chain growth occurs by repetitive olefin insertion into the Zr-C bond of the cationic active species. Studies of model chelated-olefin complexes Cp2Zr{OCMe2CH2CH2CH=CH2}+ indicate that the d0 metal center coordinates the pendant olefin in an unsymmetrical fashion primarily through C1, which results in polarization of the olefin double bond and buildup of positive charge at C2. These results and related control studies suggest that Cp 2 Zr(R) + species coordinate and polarize olefin in a similar fashion, thus promoting insertion into the Zr-C bond. These advances have prompted the development of new classes of LnMX2 and LnM(R)+ catalysts (Ln = ancillary ligand(s)) which incorporate the key features of metallocene systems, but which contain new metal/ligand combinations and as a result display different polymerization characteristics. Here we describe extension of these studies to the main group metals. Neutral aluminum alkyls oligomerize ethylene to C8-C20 a-olefins at high ethylene pressures and temperatures above 120°C. However this process is quite slow; for example AlEt3 oligomerizes ethylene with an activity of < 10 g/(mol Al*h*atm) at 140°C and 36 atm. Mono
Novel Naturally" Compatible Polyolefin Alloys by Single-Site Ziegler Catalysts"
James C.W. Chien, May 1999
The properties of different polymers may be brought together by different ways. Random copolymer is one method. More strikingly new and improved properties are achieved by graft or block copolymerization, with respective examples of ABS and impact modified polypropylene. Specific process is required to prepare each such copolymer system. This is illustrated by the synthesis of thermoplastic elastomeric polypropylene, comprising of alternating blocks of isotactic polypropylene (I-PP) and atactic polypropylene (a-PP)2,3. It is prepared with a specially designed asymmetric (C1) metallocene catalyst, rac-ethylidene(1-?5-tetramethylcyclopentadienyl)(1-?5-indenyl) titanium dichloride, which functions by switching between two catalytic states to promote alternatively stereoselective and nonselective polymerization of propylene4-6. A general method to obtain new products and to expand the market is by the physical mixing together (blending) of existing products into polymeric alloys or blends. No new polymer need be synthesized. Since two polymers are usually immiscible for well-known thermodynamic reason, alloy is best formed between polymers with comparable cohesive energy densities. The process can be promoted by compatibilizing agent. Such system is thermodynamically unstable. However, mixing at phase boundary may persist sufficiently long for it to have useful applications. The most effective compatibilizing agent is usually a block copolymer of the polymers to be blended. However, the synthesis of any block copolymer is not a simple matter (vide supra). Polyolefins form a large family of materials possessing every known property. However, it is very difficult to prepare blends of polyolefins. We disclose here a method to prepare novel “naturally” compatible polyolefin alloys by binary single-site Ziegler catalysts.
High Stereoregular or Elastomeric Polyolefins Promoted by Rac- or Chiral Octahedral Complexes
Moris S. Eisen, May 1999
This presentation will report the synthesis and activity, as precatalysts for the stereoregular polymerization of propylene, of four racemic mixtures of bis(benzamidinate) group-4complexes, cis-[p-R'C6H4C(NR)2]2MX2 (R' = CH3, R = SiMe3, M =Ti, X = Cl (1); R' = CH3, R = SiMe3, M = Zr, X = Cl (2); R' = H, R = i-pr, M = Zr, X = Cl (3); R' = CH3, R =SiMe3, M = Zr, X = CH3 (4)). The hydrocarbyl complex 4 was prepared by the alkylation of the corresponding complex 2 with MeLi•LiBr and characterized by standard techniques including X-ray diffraction. Reaction of complex 4 with B(C6F5) or MAO (MAO = methylalumoxane) results in the formation of a cationic" intermediate complex which rapidly reacts with the incoming monomer. These complexes catalyze the stereoregular polymerization of propylene in CH2Cl2 producing polypropylene with very large isotacticities (mmmm % = ~95-98) high melting points (140-154¡C) and similar molecular weights as compared with cyclopentadienylcomplexes. The isotacticities of the polymers can be modulated by pressure and in some cases by the size of the metal center. In addition the presentation will report the synthesis and catalytic activity of new chiral C1 and C3 precatalysts. The chiral lithium (-) trimethylsilylmyrtanyl amide reacts with benzonitrile yielding the chiral benzamidinate lithium ligand ([N-trimethylsilyl][N'-myrtanyl] benzamidinate Li•TMEDA (TMEDA =tetramethylethylenediamine) [N(R*)-C-N]Li. Equimolar addition of [N(R*)-C-N]Li to TiCl4 in THF yields [N(R*)-C-N]TiCl3•THF (5). An X-ray study of 5 shows that it has an octahedral structure with the oxygen atom and one chlorine atom at the apicalpositions. [N(R*)-C-N]3ZrCl•toluene (6) can be prepared in a manner related to that employed to synthesize 5. An X-ray study of 2 shows that it has a capped octahedral geometry with the three trimethylsilyl groups in a cis position with respect to the chlorineatom and the other three myrtanyl groups arranged on the opposite side ofthe chlorin"
High Stereoregular or Elastomeric Polyolefins Promoted by Rac- or Chiral Octahedral Complexes
Moris S. Eisen, May 1999
This presentation will report the synthesis and activity, as precatalysts for the stereoregular polymerization of propylene, of four racemic mixtures of bis(benzamidinate) group-4complexes, cis-[p-R'C6H4C(NR)2]2MX2 (R' = CH3, R = SiMe3, M =Ti, X = Cl (1); R' = CH3, R = SiMe3, M = Zr, X = Cl (2); R' = H, R = i-pr, M = Zr, X = Cl (3); R' = CH3, R =SiMe3, M = Zr, X = CH3 (4)). The hydrocarbyl complex 4 was prepared by the alkylation of the corresponding complex 2 with MeLi•LiBr and characterized by standard techniques including X-ray diffraction. Reaction of complex 4 with B(C6F5) or MAO (MAO = methylalumoxane) results in the formation of a cationic" intermediate complex which rapidly reacts with the incoming monomer. These complexes catalyze the stereoregular polymerization of propylene in CH2Cl2 and in some cases by the size of the metal center. In addition the presentation will report the synthesis and catalytic activity of new chiral C1 and C3 precatalysts. The chiral lithium (-) trimethylsilylmyrtanyl amide reacts with benzonitrile yielding the chiral benzamidinate lithium ligand ([N-trimethylsilyl][N'-myrtanyl] benzamidinate Li•TMEDA (TMEDA =tetramethylethylenediamine) [N(R*)-C-N]Li. Equimolar addition of [N(R*)-C-N]Li to TiCl4 in THF yields [N(R*)-C-N]TiCl3•THF (5). An X-ray study of 5 shows that it has an octahedral structure with the oxygen atom and one chlorine atom at the apicalpositions. [N(R*)-C-N]3ZrCl•toluene (6) can be prepared in a manner related to that employed to synthesize 5. An X-ray stu producing polypropylene with very large isotacticities (mmmm % = ~95-98)high melting points (140-154¡C) and similar molecular weights as compared with cyclopentadienylcomplexes. The isotacticities of the polymers can be modulated by pressure dy of 2 shows that it has a capped octahedral geometry with the three trimethylsilyl groups in a cis position with respect to the chlorineatom and the other three myrtanyl groups arranged on the opposite side ofthe chlorin"
Concentration and Temperature Effects on the Flow of Polymeric Suspensions
Faezeh Soltani, Ulku Yilmazer, May 1999
The flow behavior of concentrated suspensions consisting of a Newtonian matrix (Hydroxyl-terminated-polybutadiene) and aluminum powder was analyzed using a parallel disk rheometer. The effects of the solid content and temperature on the viscosity and the slip at the wall behavior were investigated. Suspensions exhibited slip at the wall at concentrations close to their maximum packing fraction. The slip velocity increased linearly with the shear stress, and at constant shear stress the slip velocity increased with increasing temperature. Suspensions with more than 40% filler content by volume showed shear thinning at all of the applied temperatures.
Rapid Tooling for Injection Moulding Using Fused Deposition Modelling
S.H. Masood, W.Q. Song, J.H. Hodgkin, C. Friedl, May 1999
This paper presents the results of the research work on the development of a new metal-polymer composite material for the Fused Deposition Modelling (FDM) rapid prototyping system and the use of this material in fabricating injection moulding dies and inserts directly on the FDM system. The feed stock filaments of these composites have been successfully produced and used in the FDM system to produce test parts and inserts for the injection moulding dies. The inserts have been used in the injection moulding machine to successfully produce plastic parts in low density polyethylene and other thermoplastics. The work is a unique development in reducing the cost and time for making injection moulding dies.
Activation Energies of Polymer Degradation
Samuel Ding, Michael T.K. Ling, Atul Khare, Lecon Woo, May 1999
The degradation kinetics of a series of polymers was studied. The Arrhenius activation energy was used as the parameter to follow the rate dependence with temperature. For most systems, it was evident that the activation energies increase monotonically with temperature. This finding explains the frequent observation that kinetic parameters obtained at high temperatures often lead to grossly optimistic estimates of shelf-life at ambient. The activation energies of polypropylene from the surface embrittlement processes were also found to have a striking similarity to the thermal processes, with nearly identical activation energies at the same temperature. This observation could lead to broader applications and further understandings on the polymer degradation
High Temperature Flexible Polyolefins: A User's Perspective
Atul Khare, Samuel Y. Ding, Michael T.K. Ling, L. Woo, May 1999
In the last few years, we have witnessed a fundamental material revolution not seen in the last half century of polymer history. The so called single site catalyst, many of which metallocene compounds, are creating novel compositions and properties unheard of only a few years ago. In the medical plastics and packaging markets, the achievement of cost performance similar to that of the flexible PVC has always been an technology challenge. With the metallocene catalyst, unprecedented co-monomer incorporation can be achieved with high homogeneity, ultra low-density poly-ethylenes becomes widely available. However, with the steady reduction in crystallinity and modulus, the melting point also decreased monotonically. Thus, materials with both the flexibility and high temperature capabilities are still very rare. More recently, several developments on propylene based elastomers have been discussed. Combining the high melting point of isotactic polypropylene with a suitable elastomeric block structure appears to be very promising in achieving these properties. In this paper we will present our actual experiences in utilizing these new materials in medical application.
Shelf Life Failure Prediction Considerations for Irradiated Polypropylene Medical Devices
Michael T.K. Ling, Samuel Y. Ding, Atul Khare, L. Woo, May 1999
In a standard method for assessing polypropylene syringe durability, the maximum bend angle before failure was used as a measure of the device ductility. Since the ductility of polypropylene is heavily dependent on deformation rate, choosing a realistic testing rate is critical to predict its shelf life accurately. In addition, irradiated polypropylenes undergo degradation when free radicals deposited by the radiation react with atmospheric oxygen to form a brittle surface layer. This brittle layer can create sharp notches and magnify the local strain rates causing the entire device to fail. Therefore, it is important to incorporate the effect of strain rate and degraded surface in the shelf life prediction of the polypropylene devices. For thin film applications, we found that oxidative induction time (OIT) test combined with oven testing can be used to predict its shelf life quite satisfactorily.
Radiation Resistance of Multilayer Films by Instrumented Impact Testing
Robert Wojnarowski, Michael T.K. Ling, Atul Khare, L. Woo, May 1999
Olefinic multi-layer films are becoming increasingly cost-effective in the medical industry for a wide variety of applications. And terminal sterilization by gamma or electron beam is also becoming wide spread due to its economy and simplicity. However, during the irradiation process, much of the antioxidant in the polymer can be depleted, and in the case of high glass transition (Tg) polymers like polypropylene, could lead to brittleness during the shelf life storage of the product. We have utilized an instrumented impact test where film samples' high strain rate ductility and toughness can be quantified at deep subambient temperatures. The test system was constructed using the Lab-View( instrument interface system with an personal computer as the controller. Temperature control, velocity sensing and high speed strain gage data acquisition were all handled automatically. After the impact event, data presentation, energy integration and file archiving were built into the system. Using this system, we quantified the post irradiation embrittlement behavior of a multilayer film and developed an effective impact modifier system which insured ductility retention long after irradiation at high doses.


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