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

Quantification of Melting Progression during Twin Screw Extrusion Using the Pulse Perturbation Technique Part II: Physics of Melting

Mark D. Wetzel, Donald A. Denelsbeck, Susan L. Latimer, Chi-Kai Shih, May 2005

Further analysis of steady state and pulse perturbation monitoring of the melting process in a twin-screw extruder discussed in Part I has been carried out with respect to the physics of melting. This paper examines why the total specific energy changes with operating conditions. New parameters are defined, the differential specific energy, ?P/?Q and ?P/?N, that can be determined from either monitoring method. It is proposed that the differential specific energy may be used to characterize an extrusion system and applied to the prediction the total specific energy at any rate and screw speed. From pulse and RTD responses, a modified description of the progression of melting based on plug and fluid flow regimes is made using concepts advanced previously. Energy input related to back mixing or mass spreading during melting is discussed.

Structure-Property Correlations for PE Blown Films

Shokoh Fatahi, Abdellah Ajji, Pierre G. Lafleur, May 2005

In order to develop correlations between the properties and microstructural characteristics of polyethylene (PE) blown films, three polymers were evaluated in this study: LDPE, LLDPE and HDPE. Series of blown films were produced at different process conditions. Morphological characteristics of the films were analyzed using SEM and AFM. Herman’s orientation factors of the films were determined via both wide angle X-ray diffraction pole figures and FTIR. DSC, WAXD and SAXS were used to determine the degree of crystallinity, lamellar thickness and crystal dimensions. Finally, key mechanical properties including Elmendorf tear, dart impact, tensile properties in both MD and TD and optical properties such as haze and clarity have been measured. By using the statistical design of experiments and multivariate modeling, the properties of PE films are correlated to the microstructural parameters including; lamellar thickness, crystal size and Herman’s factors.

Study on the Properties of Gear Disk in Co-Rotating Twin Screw Extruder

Xiuqing Ma, Shixiong Ren, Qingfeng Liu, Yanling Yin, Xiaozheng Geng, May 2005

Gear disk is one of the most important mixing screw elements. It can meet the demand in distribution mixing of filler in polymer, and can be used in co-rotating twin-screw extruder with other screw elements in different configurations. In order to study which screw configurations can get the best mixing capability, flow fields of different configurations of gear disk and common screw elements were studied. Pressure profile and shear stress profile were calculated. The mixing ability of different flow fields was compared. The result can be concluded that alternate short mixing zones have better mixing ability than a whole long mixing zone. The simulation results of the flow field in different screw configurations of gear disk and common screw elements were verified by experiments.

Development of Thermoplastic Polyurethane Electrolytes and Their Ionic Conductivity

Soondeuk Jeung, Kyonsuku Min, May 2005

The ionic conductivity of linear segmented thermoplastic polyurethane (TPU) in-situ reacted with alkali metal salts is investigated. The kinetics of thermoplastic polyurethane (TPU) electrolytes complexed with varying molar concentrations of lithium perchlorite (LiClO4) salt has been studied at various temperature (100, 120, 140, and 160°C) by differential scanning calorimeter (DSC). The relationship between ion conductivity and cationic size in TPU electrolytes is discussed with different salts including LiClO4 and KI. Fourier transform infra-red (FTIR) spectroscopy was used to determine the interaction of LiClO4 and KI salts with TPU. The temperature dependency of TPU electrolytes is also studied by using the modified LCR meter.

Erosion and Continuity Development in High Viscosity Ratio EPDM/PP Blends

Prashant Bhadane, Basil Favis, Michel Huneault, Michel Champagne, Florin Tofan, May 2005

Blends of EPDM and PP provide an interesting model system to examine continuity development in very low interfacial tension systems. In this work an emphasis is placed on the study of high viscosity ratio blends. The SEM micrographs of the dispersed phase, after matrix dissolution, demonstrate a variety of unusual morphological features including: isolated nanometer-scale fibers, very large particles, and numerous particles interconnected by fibers. It is found that the high viscosity EPDM phase slowly erodes during melt blending by a number of different mechanisms: i) simple erosion, at low compositions, ii) via droplet alignment, elongation in the direction of first normal stress and the subsequent strangulation in the flow direction, and iii) collisioncoalescence- separation type erosion, at higher compositions of the dispersed phase. It is found that the unique morphologies generated enable the dispersed phase to percolate and become cocontinuous at unexpectedly-low compositions of the dispersed phase.

Dimensional Stability of Pre-Shaped Nylon-6 Tubes

Jean Zheng, James Colunga, Yi Zhang, May 2005

During the fuel tank assembly process, preshaped Nylon-6 vapor lines were subjected to 148.9°C. At this elevated temperature the bent tubes tended to return to their original straight shapes, which created undesirable contact with the tank shell. A series of experiments were performed in lab to quantify the effect of several design and processing variables – bend radius, angle, and orientation; forming temperature; and storage temperature – on the tube dimensional stability. Experimental results indicated that the bend radius, forming temperature, and storage temperature affected the tube dimensional stability significantly while the other factors did not. Curved beam theory was employed to calculate the equivalent bending moments associated with the radius change measured in the experiments. Those bending moments were then applied to FEA models to predict the dimensional change of vapor lines at assembly positions. The CAE predictions correlated well with the assembly test results and successfully resolved the contact issue.

Rapid Thermal Response Mold Design

Weidan Liu, Tom Kimerling, Byung Kim, May 2005

Rapid thermal response (RTR) technology has been successfully applied to the injection molding and hot embossing processes. This technology was found to be durable and reliable for manufacturing disposable plastic parts with micro/nano scale features. This paper focuses on the mold design challenges. Thermally induced surface deflection and stress of the mold were simulated and used for optimal mold design with respect to thermal fatigue failure. A mold was constructed and tested to verify simulation results by experimental study. In a thermal fatigue test, the optimal designed mold showed no signs of fatigue after 10,000 thermal cycles.

Development of a Technology for Large Scale Production of Continuous Fiber Reinforced Thermoplastic Composites

W. Krause, O. Geiger, F. Henning, P. Eyerer, May 2005

New highly economical process technologies for long-fiber reinforced thermoplastics such as the LFT-D process are the current trend of the market in the automotive industry in Europe. The next step on the way to enhanced LFTs is the use of engineering thermoplastics (e.g., PA66, SAN and PBT) as well as co-molding with local reinforce ments and tailored fiber placement [1, 2, 3, 4]. The process described in this paper shows how continuous fiber reinforcements such as fabrics, profiles, and preforms are co-molded with an LFT material in one step (Tailored LFT). Process parameters for a sufficient bonding of the thermoplastic preform with LFT-material as well as an example of an automotive application are given in the paper. A pilot-scale production plant has been built to demonstrate the ability of serial production.

Research of Screw Configurations on Dispersing Nano-Particles in Polymer

Xiuqing Ma, Qingfeng Liu, Haiyong Li, May 2005

Melt compounding is one of the methods in dispersing nano-particles in polymer. In this paper, 12 different screw configurations in co-rotating intermeshing twin-screw extruder for preparing nano-particles/polymer composite (by Melt compound processing) were studied. The physical property test and TEM of extrudates were carried out. The results show that VCR which characterized as having highly tensile effects, are much more preferred in the melting zone of the intermeshing twin-screw rather than in the melt conveying zone, as well as the forward kneading block which have remarkable shearing performance. While the reversed kneading block and NIMPE elements being set in melt conveying zone of the twin-screw will have much more advantage over those in the melting zone.

The Effect of Sorbitol Based Nucleating Agents on Tear Strength in Polyethylene Film

Arnold Lustiger, May 2005

Ziegler-Natta (Z-N) based polyethylenes have been generally known to display higher tear strengths in blown film applications, especially in the machine direction, than their metallocene-based counterparts. Z-N films display an oriented lamellar morphology, while the metallocene film morphology is more spherulitic and hence less oriented. The objective of this work, in part, was to try to duplicate the Z-N film morphology in metallocene films by adding nucleating agents that orient during film blowing. It was shown that addition of sorbitol based nucleating agent to metallocene based films gives rise to increased lamellar orientation and hence improved tear strength since the nucleant forms an oriented gel in the melt.

Optimization Model Based on a Heuristical Method for Barrier Films Design

Iván Darío López, Omar Estrada, María del Pilar Noriega, Kellys Osorio, May 2005

This paper presents an optimization model based on a heuristical method to support the design of plastic barrier packaging for food and beverage. The goal is to minimize the cost of a multilayer film structures satisfying the end product requirements. The technical conditions for every layer and its polymer material (support, tie and barrier materials) are considered.The algorithm of this optimization model was evaluated by means of numerical experiments considering accuracy and precision for obtaining the target results. The oxygen and water vapor barriers for several multilayer films up to seven layers were measured and compared with the results of the model.

Polypropylene - Polyethylene Multilayer Films

X. Zhang, A. Ajji, May 2005

In this study, we investigated the properties and some structural parameters of multilayer and blends films of polypropylene (PP) and polyethylene (PE) obtained from the extrusion blowing process. Three PP’s (a homopolymer, copolymer and a high melt strength PP compound) and one LLDPE were used. In general, tensile strength and modulus were larger in MD than TD and tear resistance higher in TD than MD, with some differences between the different sets of polymers. The modulus and strength were lower for the films made from the blend. Haze depended strongly on the PP used and whether it was pure, multilayer or blend, with the lowest haze obtained for the multilayer films made of copolymer PP and the highest with the multilayer films with homopolymer PP. Other properties such as oxygen permeability will also be discussed. The oriented crystalline structure of the PP’s was such that b-axis oriented in ND-TD plane and c-axis oriented in MD. PE crystalline morphologies at the interface were different for the different PP’s multilayer films and blends. PP had similar crystalline orientation for blends and co-extruded films but not PE.

Optimise Organoclay Exfoliation in Polymer Nanocomposites by Customising the Extrusion Temperature Gradient

C.Y. Lew, I.M. Major, W.R. Murphy, G.M. McNally, May 2005

This is a communication article describing a novel and simple approach to optimise the exfoliation and dispersion of organoclay layered-silicate in the extrusion processing of polymer nanocomposites. A range of HDPE nanocomposites were processed by configuring the extrusion temperature gradient in a single-screw compounder. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of organoclay exfoliation, which is directly associated with the various property improvement in nanocomposites, was influenced by the extrusion temperature gradient. These nanocomposites exhibited significant difference in their rheological flow characteristic and mechanical properties, owing to the difference in the resultant organoclay structures. Regardless of the level of organoclay exfoliation, all the nanocomposites exhibited better processability and improved mechanical properties compared to the virgin HDPE. The elongation at break of all the nanocomposites was considerably greater than the virgin HDPE despite recording an increase in crystallinity.

Comparative Study between Metallocene Polyolefin Blends Modified by Beta-Irradiation and a Silane Crosslinking Process

N. Villarreal, I. Gobernado-Mitre, J.C. Merino, J.M. Pastor, May 2005

Three binary groups of metallocene blends of ethylene- 1-Octene copolymer (80 and 50 weight %) with two metallocene ethylene-1-Octene copolymers of different crystalline density and a metallocene EPDM were made in a co-rotating twin-screw extruder. The first group corresponds to blends without chemical modification. In the second group the dispersed phase was grafted with vinyl-triethoxy silane by means of a reactive extrusion process (SIOPLAS). The blends of the third group were crosslinked with Beta-Radiation at 200 KGy as final dose. The gel content of the crosslinked blends showed higher values for those blends crosslinked by Beta- Irradiation than SIOPLAS process. DSC using a heat treatment known as Successive Self- Nucleation/Annealing (SSA) and DMA techniques were used to analyze the effect of the comonomer content on the crystalline morphology of the crosslinked materials. Important changes in crystalline morphology of the blends due to the crosslinking process were observed.

Structure and Oxygen Barrier of Polyhydroxylated Dendritic Polyols

Sergei Nazarenko, Jason Pratt, Brian G. Olson, Jun Lin, Shaosheng Dong, May 2005

Dendritic polymers exhibit properties that often differ dramatically from those of the more traditional polymer types. Only minimal research has been done in the past to understand gas transport behavior of these unique polymers.In the present work, oxygen barrier properties of a series of inexpensive dendritic aliphatic polyesters (Boltorn™) containing multiple functional hydroxyl groups have been studied as a function of relative humidity (RH) and temperature. The structure of these HB polyols was also modified by cross-linking with linear aliphatic, 1,6- hexamethylene diisocyanate (HDI), to improve the mechanical properties and to reduce the water sensitivity.

Compatibilisation Protocol for the Processing of Polypropylene Organoclay Nanocomposites

C.Y. Lew, W.R. Murphy, G.M. McNally, J.E. Godinho, D.C. McConnell, May 2005

The effects of compatibilisers on the structures and properties of polypropylene organoclay nanocomposites, produced through maleation or acrylation with a range of chain functionalized oligomers were investigated using wide-angle (WAXD) and small-angle X-ray diffraction (SAXD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and mechanical analysis. Results showed that optimal nanocomposite properties, exfoliation and dispersion of the clay particles in the PP matrix required wetting of the clay substrates by a low molecular weight and high functionality compatibiliser, loaded at moderate concentration.

Novel Immiscible Blends for Membrane Applications

K.L. Lin, K.K. Sirkar, M. Xanthos, May 2005

Following our earlier work on PP/PS immiscible blends, the morphologies of blends and microporous membranes of hydrophobic poly(4-methyl-1- pentene)(TPX)/ hydrophilic polyethylene vinyl alcohol copolymer(EVOH) immiscible blend systems prepared in continuous extruders are investigated. The EVOH can form a well-distributed minor phase with domains having dimensions around 1~5?m by adding compatibilizing copolymer Lotarder®AX8950. The immiscible blend systems are extruded through a sheet die and then stretched to make flat, solvent-resistant microporous membranes suitable for ultrafiltration applications.

An Investigtion of Metallocene and Ziegler-Natta Catalysed LLDPE/Clay Nanocomposites

C.Y. Lew, W.R. Murphy, G.M. McNally, D.C. McConnel, I. Moore, J.E. Godinho, May 2005

The influence of controlled-chain branching in a metallocene-catalysed LLDPE (mPE) and random chain branching in a conventional LLDPE (zPE) on the exfoliation behaviour of an organoclay was investigated. Both X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed the clay exfoliation level to be significantly higher in the metallocene LLDPE. Rheological analysis suggested that higher shear stress during the processing of metallocene polyethylene, attributed to the narrower molecular weight distribution was responsible for this phenomenon.

Impact of Titanium Dioxide Surface Characteristics on Extrusion Processing

Rajath Mudalamane, Philipp M. Niedenzu, William T. Sedar Jr., May 2005

Interfacial interactions between the titanium dioxide pigment surface and the polymeric matrix have a significant impact on the energy requirements for incorporation and the rheology of the resulting compound. This study investigated the effect of screw geometry and operating conditions on dispersion performance and torque loading during twin-screw compounding of three different grades of titanium dioxide pigments with different surface treatments into highly loaded polyethylene masterbatches. It was found that the screw design and operating conditions where the pigments performed best were quite different for the three grades. It was found that low intensity mixing sections and cooler barrel temperature settings seemed to favor the pigment with a compatibilizing hydrophobic surface treatment and high intensity mixing sections and hotter barrel temperature settings favored the pigments that did not have such a surface treatment. It was also found that by optimizing screw designs, much higher throughputs and better dispersion could be achieved.

Twin Screw Extrusion of the Reactive Blends of Thermoplastic Polyurethanes and Poly(Vinyl Chloride)

Shane Parnell, Johanna Baena, Kyunsuku Min, May 2005

The reactive blending of Poly (Vinyl Chloride) (PVC) and Thermoplastic Polyurethanes (TPU) was performed by using a counter-rotating, intermeshing twin-screw extruder. The blending technique consists of two sequential stages of mixing and reaction respectively. In the first stage, the PVC is pre-blended with monomers of the TPU (soft segment and chain extender). In the second stage, the polymerization of the TPU in-situ with the PVC takes place upon the addition of the third monomer of the TPU (diisocyanate). In this study, the novel in-situ reactive extrusion technique and the procedure for producing PVC/TPU blends are discussed.