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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In this study, the effect of PC-oligomer on mechanical properties and internal structure of injection molded glass-fiber reinforced PC/ABS was investigated. The mechanical properties of PC/ABS with PC-oligomer were lower and the difference became larger with increasing GF content. However, the internal structure was different from the surface to the middle layer through thickness direction. It is thought that this difference in structure and the dispersion of GF affected the mechanical properties of the composites.
The Non-Linear Strain Energy Equivalence Theory, a semi-empirical model, is utilized to predict long-term creep from short-term compressive stress-strain experiments conducted at different strain rates. Stress-strain experiments in uniaxial compression are performed at strain rates of 3 and 0.03 %/minute to predict creep behavior and stress-strain data at several strain rates for an immiscible polymer blend of recycled fractional melt flow high-density polyethylene and recycled polystyrene. The creep behavior is predicted up to 50 years at stress levels of 400 and 800 psi.
Surface damage of polymers in the nanometer-range is examined and results correlated with material characteristics and surface roughness of epoxies. Under a constant loading and constant scratch rate testing condition, surface roughness plays little or no role in surface damage formed during the course of this study. Material characteristics influence the damage occurred in terms of variations in elastic recovery, damage pattern and damage mechanism. The variations in scratch head geometry, which, in turn, lead to the variations in magnitude of stress and stress field distribution, give rise to various scratch features on the polymer.
Scratch behavior in several types of plastics have been investigated in order to develop scratch test method for plastics. The effects of scratching conditions such as scratch speed and normal load on scratch behavior have been discussed. The scratch behavior was classified into three modes (i.e. ploughing, wedge formation and cutting) based on the vertical scratch tip displacement and the horizontal load during the scratch process and scratched surface observation. A concept of scratch behavior evaluation is described by using mapping technique and some of the typical results are introduced.
A novel family of processable rigid rod polymers with outstanding mechanical properties has been recently introduced (Parmax® Self Reinforced Polymers (SRPs)). These materials, among other applications, are of interest in the field of high strength and stiffness, MRI-transparent implants driving an interest in their surface properties. Molded articles were fabricated from rigid rod polymers and surfaces were treated by mechanical and chemical modification. Surface properties were evaluated via contact angle measurements and AFM. In general, these aromatic rigid rod materials demonstrate high hydrophobicity. Surface modification techniques provided increased hydrophilicity of the surfaces. Interaction with biological molecules is reported.
Tribological measurement values represent system- properties. Therefore they are not directly transferable from the model-system pin-disc to the bearing technology. However, these values can be adjusted through qualified correlation. Basic differences in geometrical, kinematical and thermal relations between the two systems influence the friction- and wear-mechanisms.A focal point is the tribological analysis of different systems as pin / disc (thermoplastic / Steel) and bearing / shaft (thermoplastic bearing / steel shaft). According to online-measurements and calculations, statements can be evaluated about the transferability of the results from the different systems and about the mathematical coherences of a possible correlation. The consideration of the heat development resulting out of friction in both systems, which has an important influence on the transferability of the tribological properties from the model-system to the part-system, is the main focus.
This study focused on evaluating the effects of artificial weathering (per a filtered automotive interior Xenon weathering method) on the scratch resistance of two thermoplastic polyolefins (TPO-A and TPO-B). The scratch resistance evaluated using 5-Finger and Scratch-O was significantly lower after short artificial weathering exposures for both TPOs. The coefficient of friction determined using a Slido method increased as the scratch resistance decreased. Microhardness increased and indentation depth decreased with artificial weathering.
The surface properties of thin film amphipathic proteins (hydrophobins) and Pluronic® (PEO-PPO-PEO) polymers are investigated to evaluate surface lubricity and adhesion on molded polymer surfaces. Hydrophobins are fungal proteins that self-assemble at hydrophilic-hydrophobic interfaces into amphipathic films and Pluronics are nonionic amphiphilic surfactants. Because of their unique properties, they are of interest as models for potential biomedical and pharmaceutical applications. We have studied the self-assembly behavior of hydrophobins and Pluronic® polymers on hydrophobic polymer surfaces and examined the surface hydrophobicity and the lubrication properties.
In this study, polyurethane nanocomposites of organically modified clay were synthesized by bulk-polymerization methods and their properties characterized. The polymerization methods took into account the possibility of formation of clay tethered polymer chains via reactions between isocyanate groups in the chains of prepolymer and chain extended polymers with the hydroxyl groups on organic modifier of clay. The thermal and mechanical properties of the resultant materials were evaluated as function of the method of nanocomposites preparation. As high as 110% increase in modulus and 170% increase in tensile strength were observed with only 5wt% organically treated clay particles. The method based on chain-extended polymers performed better than the method based on prepolymer.
Under the assumption that glassy polymers are incompressible, the mechanical response of a cylinder of viscoelastic material below the glass transition temperature to a torsional deformation consists of a torque response and a normal force response along the axis of the cylinder. In performing stress relaxation experiments on poly(n-alkyl methacrylate)s, the normal force required to keep the constant deformation is compressive and large. Here we examine the microscopic origins of the nonlinear response functions. We consider the influence of the secondary, sub-vitreous ? relaxation on the normal force response. This is done by performing experiments on poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) which both exhibit a ? peak in the loss modulus as a function of temperature located at the same temperature of 10 °C and having about the same intensity. A surprising result is that although the torque response for the PMMA is 50% higher than for the PEMA, the normal force response for the PMMA is 20% lower than the normal force response of the PEMA at the experimental temperatures of 45 °C and 30 °C.
The occurrence of a plastic deformation zone ahead of the crack tip in fracture of thin films and sheets of polycarbonate has been reported by several authors. This presentation will report the use of a high-speed thermographic imaging technique for studying the temperature rise at the crack tip as well as the shape and temperature distribution of the plastic zone in polycarbonate sheets. The technique was used to monitor craze and crack growth in compact tension tests. New trends in the growth of the plastic zone and the crack propagation mechanism were observed.
An in-depth experimental and theoretical study of many important factors governing the hysteresis loss of rubber vulcanizates having variation of loading of carbon black, silica, clay, resin, and curatives is carried out over a wide range of strain, strain rate/frequency and temperature. Experimental results reveal that the hysteresis loss depends on the heat generation of rubber vulcanizates, specific heat, thermal conductivity, Young's modulus, filler loading, structure and surface area of the filler, temperature difference between application temperature and glass transition temperature, frequency, temperature difference between wall and environment, stress, and stroke amplitude. To confirm the above statement, the hysteresis loss data are analyzed by dimensionless parameters developed by using both of Buckingham pi-method and Rayleigh method. Based on the analysis, an equation is developed in which hysteresis loss of rubber vulcanizates is expressed in terms of the operating conditions and material properties of elastomers.
Samples of poly(methyl methacrylate) - PMMA for short - were subjected to uniaxial tensile tests at 80 °C under conditions at which large plastic strains are obtained. The intrinsic stress-strain behavior of the material and the strain induced volume changes were simultaneously determined by means of a novel video-controlled system. It was observed that PMMA experiences a complex volume variation involving compaction and dilatation stages. These effects are correlated with orientation and crazing mechanisms.
All-acrylic block copolymers comprising rigid and rubbery blocks tethered together are prepared by a recently developed Controlled Radical Polymerization process, mediated by the SG1 nitroxide.The self-assembly of block copolymers at a molecular scale produces transparent nanostructures that are thermodynamically robust and can be processed repeatedly while maintaining favorable properties. Besides ductility due to confinement, nanostructuration of all-acrylic block copolymers can trigger new types of deformation mechanisms under dynamic loading and improve the toughness properties.
The ethylene-vinyl alcohol (EVOH) copolymers are a family of excellent high barrier resins with wide implementation in a number of oxygen sensitive food packaging applications. These materials are also widely used in retortable food packaging designs, where the multilayer structure, e.g. PP/EVOH/PP, is temporarily exposed to water vapour to render the packaged food sterile. This thermal treatment is known to lead to a deterioration in the oxygen barrier performance of the EVOH internal layer present in the structure. The previous understanding of this phenomenon suggested a plasticization process by which ingress of water through the external hydrophobic layers, e.g. polypropylene (PP), reached the high barrier EVOH layer. On the other hand, the results presented here clearly indicate that, in addition to water ingress and subsequent material plasticization, a crystallinity disruption is also taking place during retorting. Nevertheless, this crystallinity disruption can be effectively overcome, and, therefore, the packaged food safety be ensured, by, for instance, adequate drying/annealing of the packaging structure after the retorting treatment. Unprecedented time-resolved WAXS analysis of a PP/EVOH32/PP multilayer permitted us to determine that EVOH32 does actually resist the retorting process when protected between PP layers.
This paper reports on a novel route to develop EVOH-kaolinite nanocomposites by a melt intercalation process and on some relevant nanocomposite properties as a function of composition. The kaolinite clay used is a very cheap raw material of the tile industry and as such needed to be refined and chemically modified prior to the melt intercalation step. The modification was carried out with dimethyl-sulfoxide, methanol and octadecylamine in order to increase the basal plane distance of the original clay by a factor of more than three. Wide-angle X-ray diffraction (WAXD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) were used for characterization of the morphologies obtained. From the early results, partial exfoliation and intercalation of the clay platelets was the dominant morphology attained. The dispersion of clay nanolayers in the EVOH matrix seeks to improve the barrier properties of EVOH. An increase in thermal resistance, glass transition temperature, crystallinity and barrier properties to oxygen were also observed for mass clay loadings below 8%.
In this study, different polyethylene films (LDPE, LLDPE and HDPE) were produced under using different processes (film blowing and biaxial orientation) and processing conditions. The orientation of the films was characterized in terms of their biaxial crystalline, amorphous and global orientation factors using birefringence, Fourier Transform Infrared Spectroscopy (FTIR) with a tilted incidence technique and X-ray pole figures. It is well established that FTIR can measure crystalline axes orientation for polyethylenes, as well as the orientation of the amorphous phase. On the other hand, X-ray pole figures determines the orientation of the crystalline axes, and in combination with birefringence can yield the amorphous phase orientation. The results from those techniques are compared and discussed in terms of the accuracy of the techniques and the contributions of different specific entities in FTIR measurements.
We analyze constant rate cooling and heating crystallization kinetics of PET samples by DSC. The samples have various degree of disentanglement, obtained by the new TekFlow processing technology. According to EKNET interactive Dual Phase model, the amorphous state is made up of two coupled and interactive amorphous phases. These two phases have distinct viscoelastic and thermodynamic characteristics (Tg, free volume, G' and G etc.) which are determined by the potential energy of the conformers and by the state of entanglement of the macromolecular coils.Semi-crystalline polymers such as Polyethylene Terephtalate (PET) are amorphous in the molten state and should have Dual Phase behavior. The phase duality should manifest itself during crystallization from the melt during cooling or during cold crystallization while heating quenched samples.The purpose of this communication is to quantitatively describe the kinetics of crystallization of PET samples with a dual phase kinetics formulation and determine the respective influence of molecular weight and degree of entanglement on the kinetics parameters rate of crystallization and percentage of crystallinity."
The interfacial tension of binary blends of an amorphous copolyester, poly(ethylene-co-cyclohexane 1,4-dimethanol terephthalate) (PETG) and an itaconic acid grafted polypropylene (PP-g-IA) have been investigated in order to elucidate the effect of ionic incorporation on interfacial tension. PP-g-IA was formed through reactive extrusion using dicumyl peroxide as the initiator with neutralization agents of zinc and magnesium oxide. Interfacial tension was determined using the breaking thread method (BTM). Reductions in interfacial tension have been seen with the grafting of itaconic acid onto PP, with neutralized PP-g-IA showing further reductions in the interfacial tension between the blend components.
Dynamically vulcanized PP/EPDM blends were treated by high intensity ultrasonic waves during extrusion. These blends were compared with unvulcanized PP/EPDM blends that were treated by ultrasound during extrusion and then dynamically vulcanized. Die pressure and power consumption were measured. The effect of different gap sizes, ratio of components, and number of ultrasonic horns were investigated. The rheological properties, morphology and mechanical properties of the blends with and without ultrasonic treatment were compared. The results obtained indicated that ultrasonic treatment induced the thermo-mechanical degradation causing enhanced molecular transport and chemical reactions at the interfaces, thus leading to in-situ compatibilization, which is evident by the morphological and mechanical property studies. Processing conditions were established for enhanced in-situ compatibilization of the dynamically vulcanized PP/EPDM blends.
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