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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BARRIER PROPERTIES OF GRAPHENE-BASED POLYMER NANOCOMPOSITES
Exfoliated graphite sheets, or graphene, are currently being studied for their electrical, mechanical, and thermal properties. This material also has great potential for mass transfer barrier properties when dispersed in polymer to form polymer nanocomposites (PNCs), and these graphene-based PNCs (GPNCs) should yield better properties as compared to PNCs made using other nanofillers, including nano-layered silicates. In this work, commercially-available graphene was surface treated with silanes to impart hydrophobic character to the graphene surface allowing for better dispersion in a matrix of polyvinyl acetate (PVAc). This was verified using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moisture diffusion through PVAc samples containing up to 1.5 wt.% treated and untreated graphene with platelets of two different aspect ratios was studied at room temperature which showed that the initial moisture diffusivity decreased with increasing filler content. The diffusion coefficient was found to reduce by as much as two orders of magnitude from that of the neat polymer. These results are superior to those obtained by us in the past using organoclay as the filler, where the observed reduction was about 20%. Clearly, graphene platelets form an excellent barrier against water diffusion.
DETERRA® BIOBASED POLYMERS-NEXT GENERATION MATERIALS FOR DURABLE APPLICATIONS
In the past decade, the market for biobased polymers has grown dramatically. Much of this growth has been in the packaging market, where biobased polymer films (i.e., PLA and PHA) have displaced conventional LDPE and LLDPE. Packaging is a natural application for biobased polymers given the short life cycle and consumable nature of this product. Recently, consumers have begun to demand green alternatives in applications where durable plastics have historically been utilized. For example, PVC has been under intense scrutiny in recent years. PVC’s inherent chemical nature and the additives it is often formulated with have been identified by several organizations targeting chemicals that can harm the environment. In certain markets, like the building and construction market, there is a salient need for a biobased material that can be used as a PVC alternative. Leadership in Energy and Environmental Design (LEED) certification and other local codes and regulations are creating a new market for durable biobased polymers. One may consider durable biobased polymers a misnomer. However, the inherent nature of biopolymers like PLA, is such that they can function in one environment (e.g., interior building applications), but degrade in another environment (i.e., compost). This work describes several grades of polymeric compounds that been recently developed by Interfacial Solutions for durable applications. These products are currently marketed under out deTerra® Biobased Polymer trade name.
SUPRAMOLECULAR IONIC BLOCK COPOLYMERS
Supramolecular polymers employ non-covalent interactions to bind functional polymeric units together into effective macromolecular structures. Non-covalent interactions can lead to unique self-assembly behavior useful for processing and smart materials. This paper considers the use of ionic interactions to produce supramolecular polymers. The balance between association and dissociation of the ionic species can produce interesting properties of physically bonded multi- block copolymers. Controlled polymerization techniques were adapted to synthesize well-defined end- functionalized polymers with low molecular weights.
OPTIMIZATION AND SENSETIVITY ANALYSIS OF A FILM DIE
This study shows how response surface based goal driven optimization can be used to optimize the shape of a film die (coat hanger die). A parametric model for the die geometry is constructed containing three (input) geometrical parameters. Output parameters are defined as the pressure drop and the flow uniformity. A Design Of Experiments (DOE) approach is implemented to cover the feasible design space. A mathematical response surface is then constructed to represent the correlation between the output parameters and the input geometrical parameters. Using screening of the response surface, two optimum designs are obtained that will reduce the pressure drop and increase the flow uniformity. Furthermore, assuming possible variations in the material's shear thinning index and flow rate, to account for different material grades and throughput, the sensitivity of the pressure drop and the flow uniformity in the two suggested optimum designs are compared. It is desired to select the one design among these two suggested optimums that will have the smallest variations in flow uniformity when the power law index is changed.
REINFORCING THERMOSETS USING CRYSTALLINE DESOXYANISOIN STRUCTURES
This paper presents the preliminary investigation of desoxyanisoin molecule as an in-situ self-reinforcement agent that can also improve thermoset flammability properties. Both isothermal curing and radial temperature gradient curing conditions for epoxy network crosslinking and desoxyanisoin phase separation were investigated. Desoxyanisoin did not increase the thermoset flammability. However, this crystallizable small molecule is promising in terms of creating long microchannels and distinct reinforcement domains. Straight fiber-like crystals on the mm scale were observed during the isothermal cure, whereas the thermal gradient cure resulted in complex and rich crystallization morphologies.
GEOMETRY OF TRIPLE SCREW EXTRUDERS TO PROMOTE MIXING
The development of screw extruders has experienced several milestones over the past century, giving rise to the wide and extensive application of screw extruder in polymer, food, and other industries. The newly developed triple screw extruder began to catch close attention owing to its versatility in its changeable screw axes adjustments, multiple intermeshing regions, multi-displacement of melt flow, lower ratio of length and diameter, and higher output and energy consumption ratios. In this article the geometry of three screws inside the triple screw extruder was studies, and the result shows great advantage of performance in mixing for the triple screw extruder while comparing with twin and single screw extruders.
EFFECTS OF ANNEALING TIME AND TEMPERATURE ON THE CRYSTALLINITY AND DYNAMIC MECHANICAL BEHAVIOR OF INJECTION MOLDED POLYLACTIC ACID (PLA)
The effects of annealing time and temperature on the crystallinity of poly(lactic acid) (PLA) were investigated. The degree of crystallinity observed after short annealing times resembled those observed at cooler temperatures, suggesting a time–temperature superposition relationship. Crystallinity isotherms in the logarithmic scale were shifted horizontally along the log-time axis and a master curve was constructed. Dynamic mechanical analysis showed that an increase in crystallinity increased the glass transition temperature and improved the storage modulus.
EFFECT OF THE MOLECULAR STRUCTURE OF PLASTICIZER ON THE MORPHOLOGY OF POLYMER BLENDS WITH THERMOPLASTIC STARCH
In this study, two different plasticizers from the polyol family have been used in the preparation of thermoplastic starch. The effect of these plasticizers on the interfacial modification of thermoplastic starch/polyethylene mixtures has been examined. When a higher molecular weight plasticizer is used, a different emulsification behaviour is observed for compatibilized systems. The number average droplet size decreases much more effectively with compatibilizer content than the volume average diameter. This behaviour is attributed to the chemical structure of the plasticizer. The mechanical properties of these systems are also presented.
MORPHOLOGY OF POLY(LACTIC ACID)/POLY(BUTYLENE ADIPATE-CO-TEREPHTHALATE) BLENDS AND ITS COMPOSITE WITH SPHERICAL SILICA PARTICLES
In this work the detailed morphology of poly(lactic acid)/ poly (butylene adipate-co-terephthalate) has been carried out for the first time. The morphology of PLA/PBAT blends with different compositions was studied and limits of the co-continuity region were determined using rheological measurements and image analysis. Particle size analysis and breaking thread experiments showed that PLA/PBAT is a very low interfacial tension polymer blend. Moreover, composites of PLA/PBAT/spherical silica particles were prepared and the localization of silica particles in this blend was studied.
CARBON NANOTUBES IN BLENDS OF THERMOPLASTIC STARCH/POLYCAPROLACTONE CARBON NANOTUBES IN BLENDS OF THERMOPLASTIC STARCH/POLYCAPROLACTONE
Polycaprolactone (PCL) has been blended with thermoplastic starch (TPS) and carbon nanotubes in different compositions. The localisation of solid particles is an influential factor in filled polymer blends. Hence, SEM and TEM images have been used to investigate the morphology and localisation of nanofilled-polymer blends. .The blending of a semicrystalline polymer with another polymer or nanofillers will also change the thermal properties of the polymers in different ways. This change has been studied by non-isothermal crystallization curve analyses. These results were interconnected in such a way that it was possible to confirm the localisation from thermal properties.
SELECTIVE LOCALIZATION OF SPHERICAL SILICA PARTICLES IN HETEROPHASE POLY(LACTIC ACID)/ LOW DENSITY POLYETHYLENE BLENDS
In this article, different strategies to control the localization of spherical silica particles in Poly(lactic acid)/ Low density polyethylene blends were studied. These strategies include different sequences of addition of components and compatibilization. Results show that using these different strategies, the controlled localization of silica particles in either the matrix or in the dispersed phase can be achieved. Long processing times used in this study show that the observed localization is stable and does not change with further processing.
HIGHLY GAS PERMEABLE UV CURED, PERFLUORINATED ACRYLATE MODIFIED THIOL-ENE NETWORKS WITH TUNABLE TRANSPORT PROPERTIES
Optically clear perfluorinated acrylate modified thiol- ene network films were prepared via a two-step approach, first by modifying multifunctional thiols with perfluorinated acrylates of different length followed by UV curing in the presence of multifunctional enes. By increasing the length of the perfluorinated species, free volume of the networks was shown to noticeably increase. As a result, oxygen permeability showed more than a three order of magnitude improvement with the increase of the length of perflurinated moieties as compared to unmodified network. Water vapor permeability also increased but to a critical level.
USING FINITE ELEMENT ANALYSIS TO ADVANCE HEAT STAKE DESIGN
Staking is a widely used joining technique to bond similar and dissimilar materials. There are many different staking techniques, such as ultrasonic staking, hot air cold staking, heat staking, and infrared staking. Recently, impulse staking and laser staking were also reported. The concept of staking is by deforming a stud or a hollow boss to form a button (or mushroom) to mechanically hold two materials together. This work utilized finite element (FE) modeling to study the effect of stake geometry on retention force. For FEA modeling, 3-D solid models were constructed to simulate the stake under a tensile load. It was found that a minimum button height to pin diameter ratio of 0.625 was required to had necking occurred in the pin during tensile loading. In addition, smaller hole opening provided higher retention force for shorter stake; however, for a larger stake this effect is minimum. A minimum overlay at the opening is required to have necking occurred in the pin. Furthermore, difference between theoretical and practical design was also discussed.
IMPROVED APPROXIMATIONS IN THERMAL PROPERTIES FOR SINGLE SCREW EXTRUSION
Actual screw design software is capable to simulate the performance of a single screw extruder based on elaborated program codes. The aim of this work is to present improved approximations in relevant thermal properties for simulation and design of single extrusion screws in combination with analytical calculations appropriate for the industrial praxis. The developed approximation functions for thermal properties, such as, specific heat capacity, enthalpy, thermal conductivity and density, were obtained looking for small number of parameters. A comparison between the improved approximation functions, existing known functions and measured data for some common polymer families is shown.
MULTI-COMPONENT BIO-BASED BLENDS WITH POLYLACTIC ACID AND POLYHYDROXYBUTYRATE: MORPHOLOGY AND PHYSICAL PROPERTIES
Polylactic acid (PLA) and polyhydroxybutyrate (PHB) are two of the most important polymers derived from renewable resources. In this work, the morphology and physical properties of binary blends of PLA/PHB and multi-component blends of PLA/PHB with other commodity polymers such as polystyrene (PS) or biodegradable polymers such as polycaprolactone (PCL), poly (butylene succinate) (PBS), and poly(butylene adipate-co-terephthalate)(PBAT) were examined. Completely biodegradable blends of PLA/PHB/PBAT/PCL and PLA/PHB/PBAT/PBS demonstrated some unique morphologies including triple percolated systems.
MULTICOMPONENT BIODEGRADABLE BLENDS WITH POLY(BUTYLENE SUCCINATE): PARTIAL AND COMPLETE WETTING PHENOMENA
PBS (Poly(butylene succinate)) is a promising emerging bioplastic with good strength and modulus, however, its elongation at break (EB) is quite low and blends with higher EB materials are a potential route to develop more balanced properties. Blends of PBS with biodegradable polymers including polycaprolactone (PCL), poly(butylene adipate-co-terephthalate) (PBAT), and poly(lactic acid) (PLA) were studied. These blends result in fully-biodegradable blends with completely different thermodynamically stable wetting behaviors and hence, significantly different potential morphological states.
FEM MODELING OF SURFACE FRICTION EFFECT ON SCRATCH-INDUCED DEFORMATION IN POLYMERS
Three-dimensional finite element method (FEM) parametric study was performed to investigate the effect of surface friction on scratch-induced deformation. By varying the post-yield behavior of the polymer substrate, the effect of surface friction on scratch depth and its correlation with the strain hardening slope is sought. The simulation results indicate that the onset of groove formation during the scratch process is strongly influenced by surface friction. Also, increase in strain hardening slope reduces the relative frictional effect on scratch depth.
IN-LINE MEASUREMENT APPARATUS FOR RESIDENCE TIME DISTRIBUTION IN TWIN-SCREW EXTRUDER AND ITS APPLICATION IN POLYMER PROCESSING
The simulation of thermally and flow induced crystallization behavior of semi-crystalline polymers is of great engineering significance in polymer processing like injection, blow molding and extrusion. However, its key technology for practical application remains to be difficult. In the study, the mathematical model of three- dimensional thermally and flow induced crystallization of polymer melts obeying Phan-Thien and Tanner (PTT) constitutive model is established. A penalty finite element/finite difference method is introduced to solve the nonlinear governing equations. The computation stability is improved by using the discrete elastic-viscous split stress (DEVSS) algorithm incorporating the streamline upwind scheme. A modified Schneider’s approach is employed to discriminate the relative roles of the thermal and the flow state on the crystallization phenomenon. Two driving causes for the crystallization of polypropylene in extrusion process including the thermal and the flow state are investigated. Both the crystalline distribution and crystalline size of polypropylene are obtained based on the proposed mathematical model and numerical scheme.
RHEOLOGICAL CHARACTERIZATION OF INJECTION MOULDING GRADE THERMOTROPIC LIQUID CRYSTAL POLYMERS (LCPS)
Liquid Crystal Polymers (LCPs) are advanced high temperature processing polymers with unique physical properties. It contains rigid rod like molecules, which exhibit structural orientation during the flow process at one or two dimensional level. Rheological behaviour of unfilled LCPs and filled (glass fibre) LCPs were characterized with ARES and Capillary rheometer at low and high shear rates. The complex viscosities (h*) as well as shear viscosities (h) showed a typical shear- thinning behaviour. LCPs exhibit anomalous rheological behaviour with shear and temperature. Viscosity reduced at low shear rate region because of the tumbling nature of rod like molecules. The abnormal temperature dependence of the viscosities can be explained by the transition of anisotropic rod-like molecules to isotropic molecules with increase in temperature. In steady shear flow, it was observed that rotational transformation occur from direction of flow to surface direction, which leads to first negative normal stress difference (N1) with shear rate. Stress relaxation conducted after cessation of shear flow to prove the molecular dynamics. Multiple overshoot observed due to tumbling, which was varying with temperature and shear rate.
EFFECT OF PLASTICIZER ON THE PHYSICAL PROPERTIES OF TRI-ACETYL CELLULOSE FILM
Tri acetyl cellulose (TAC) is not a good material for the chain stretching due to its main chain rigidity. Plasticizers were introduced to increase the chain flexibility and the effect of plasticizer on physical properties of TAC film was studied. The lowering of glass transition temperature, melting temperature and crystallinity were found and this was understood that plasticizer provided the main chain mobility by reducing interaction between TAC molecules. These made possible to stretch the TAC chain under low stretching temperature and resulted in the development of birefringence in TAC film which indicated the characteristic of retardation film
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