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

Thermoplastic Composites Containing Deformable Reinforcing Composites

Donald G. Baird, Wei Huang, Jianhua Huang, Robert T. Young, May 1999

The forming and shaping of thermoplastic composite prepregs is severely hindered by the lack of deformability of the reinforcing component (e.g. glass or carbon fiber) and the separation of the matrix from the reinforcing component. In this paper we study the behavior of thermoplastics reinforced with two types of reinforcing components which are deformable in subsequent shaping operations. In particular we investigate the formability of thermoplastics (e.g. polypropylene, polyetherimide, and polyphenylene sulfide) reinforced with thermotropic liquid crystalline polymer (TLCP) micro-fibrils of higher melting point than the matrix and with melt processable glass. Studies include thermoforming, stretching, and compression molding of blanks containing micro-fibrils of both reinforcing materials.

A Method to Quantify the Average Biaxial Orientation of the Crystalline Phase in Polyethylene Blown Films

Rajendra K. Krishnaswamy, May 1999

Following an approach suggested by Kissin (Journal of Polymer Science: Polymer Physics Edition, v30, 1165, 1992), a general form of the Beer-Lambert law was employed to quantify the White-Spruiell biaxial orientation factors for various polyethylene (PE) blown films using IR absorption data at 719 cm-1 and 730 cm-1. It was pointed out that certain assumptions employed by Kissin are invalid for most polyethylene blown films. However, when alternate assumptions based on sound experimental evidence were employed, the resulting orientation estimates were in good qualitative agreement with X-ray diffraction patterns for various low and high density polyethylene blown films.

The Relative Influences of Process and Resin Time-Scales on the MD Tear Strength of Polyethylene Blown Films

Rajendra K. Krishnaswamy, Ashish M. Sukhadia, May 1999

This paper is concerned with the effects of polymer relaxation time (as estimated via melt rheology) and process extension rate (as quantified via an average MD extension rate at the frost line) on the MD tear strength of various polyethylene blown films. An increase in melt relaxation time at constant process conditions or an increase in process extension rate for a given resin (constant melt relaxation time) were both observed to result in lower blown film MD tear strength. These observations were interpreted in terms of molecular orientation and deformation mechanisms in polyethylene, with preliminary data suggesting that interlamellar shear plays an important role in determining the MD tear performance of LDLPE and LLDPE blown films.

Effects of Viscosity Ratio and Compatibilizers on the Morphology Andmechanical Properties of Polycarbonate/Acrylonitrile-Butadien-Styrene Blends

Kumin Yang, Shi-Ho Lee, Jong-Man Oh, May 1999

A comprehensive experimental study was carried out to investigate the effects of 1) viscosity ratio, 2) temperature, and 3) compatibilizers on the morphology of bisphenol-A-polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS). Blends were prepared by utilizing a co-rotating twin screw extruder and in-situ morphology was obtained via the screw pullout technique. Plot of the PC/ABS viscosity ratio, ?PC/?ABS, versus the shear rate showed a gradual rise in the curve up to a critical shear rate and thereafter displayed asymptotic character. Contrary to premise, ?PC/?ABS decreased with increasing temperature. This was elucidated by the melt viscosity of PC being thermally more sensitive than ABS over the temperature range investigated. As expected, plot of the average domain size versus the viscosity ratio gave a concave up curve with a minimum when the viscosity ratio was close to unity. Polymethylmethacrylate (PMMA) exhibited the greatest ABS domain size reduction, and annealed samples showed that it suppressed coalescence.

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.

Measuring Depolymerization Kinetics of a Methacrylate Using a Novel Optical Technique

F. Rodriguez, T.S. Bean, May 1999

A new and inexpensive analytical tool, thermovolumetric analysis (TVA) is similar to thermogravimeti-ic analysis (TGA) except that it is volume rather than mass which is being monitored. This is a new application of laser interferometry which is especially applicable to thin films of polymers which depolymerize at elevated temperatures. Coatings 300 to 1500 nm thick of poly(n-butyl methacrylate) on silicon are removed in an orderly manner when heated at temperatures up to 300°C. The technique can also be employed with the temperature increasing at a constant rate.

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

Future Overlays for Composite Bridges

Arif J. Chawalwala, Reynaldo M. Ong, May 1999

The smooth surface of a composite bridge deck pose a significant problem for bonding of an overlay surface. Previous research conducted using cementitious overlays have shown significant delaminations of the overlay when subjected to flexural loading. Epoxy overlays possess superior bonding and other mechanical characteristics, and have been successfully used on concrete-filled steel grid and steel orthotropic decks. Besides, they reduce the overall dead load on the structure due to its thin application. This work presents a brief overview of the properties and future potential of epoxy overlays for composite bridge decks.

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

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"