polymer science and Engineering

Standard fused filament fabrication (FFF)-based 3-D printers fabricate parts from thermopolymers, such as polylactic acid (PLA). A new range of metal based PLA composites are available providing a novel range of potential engineering materials for such 3-D printers. Currently, limited material data, specifically thermal property characterization is available on these composites. As a result, the application of these materials into functional engineered systems is not possible. This study aims to fill the knowledge gap by quantifying the thermal properties of copperFill, bronzeFill, magnetic iron PLA, and stainless steel PLA composites and provide insight into the technical considerations of FFF composite 3-D printing. Specifically, in this study the correlation of the composite microstructure and printing parameters are explored and the results of thermal conductivity analysis as a function of printed matrix properties are provided. Considering the relative deviation from the filament raw bulk analysis, the results show the printing operation significantly impacts the resultant component density. Experimentally collected thermal conductivity values, however, do not correlate to the theoretical models in the literature and more rigorous quantitative exercises are required to determine true percent porosity to accurately model the effect of air pore volume fraction on thermal conductivity. Despite this limitation, the thermal conductivity values provided can be used to engineer thermal conductivity into 3-D printed parts with these PLA-based composites. Finally, several high-value applications of such 3-D printed materials that look metallic, but have low thermal conductivity are reviewed.

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

The residence time distribution (RTD) functions were derived for screw extruders, based on the "parallel plate" and curved channel flow models. The results indicate a relatively narrow distribution, and they explain several characteristics of screw extruders. The strain distribution in the fluid across the channel was also derived. With the aid of these two functions an average strain of the fluid leaving the extruder was defined. The resulting weighted-average total strain (WATS) provides a quantitative criterion to the "goodness of mixing" in extruders.

The crystallization behavior of poly(pheny1ene sulfide) (PPS) has been examined by differential scanning calorimetry as a function of melt temperature, residence time in the melt, and the presence of a liquid crystal polymer. The results suggest that the thermal history of the sample plays an important role in determining the crystallization kinetics. Short residence times at low melt temperatures and high melt temperatures alone resulted in a low value for the Avrami exponent n. The former effect was ascribed to incomplete melting of the polymer while the latter effect was attributed to thermal degradation. Blending a liquid crystal polymer, Vectra A950, with PPS had only a minor effect on the crystallization behavior.

This paper presents the effect of nanoparticle concentration on the performance of hybrid polymer (P-DSBT)/Zinc Oxide (ZnO) thin layers. For studying the morphology, the structure and the optical behavior of the different synthesized nanocomposites, FTIR transmission spectra, scanning electron microscopy (SEM), Transmission electron microscopy, and X-ray diffractometry (XRD) were used to characterize ZnO nanostructures, atomic force micros-copy, UV-Vis absorption, photoluminescence spectroscopies and contact angle measurement were used to characterize (P-DSBT)/Zinc Oxide (ZnO) nanocomposites. It has been shown that the RMS (Root Mean Square) roughness of the hybrid layers increases as a function of the percentages of ZnO in the matrix. A clear participation of nanoparticles in the nanocomposites absorption has been demonstrated in UV-Vis spectra with maintaining the absorption features of the polymer. A photoluminescence study at room temperature was been also carried out under optical excitation set as λ = 375 nm. It was confirmed that when increasing the ZnO concentration in the polymer, a shift towards red was observed and the contact angle of the composite layers decreases progressively comparing with the pure polymer. Interestingly, this confirms that polymer and polymer-ZnO hybrid nanocomposites are well adherent to the contaminated free solid surface.

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long multimode polymer waveguide.

The rheological and thermokinetic aspects of the cure of epoxy based composite laminates are analyzed by means of a computer program developed using the heat transfer and heat generating characteristics of a polymerizable system. In particular, the temperature and degree of cure influence on the resin viscosity have been first considered, then the temperature profiles, calculated according to an appropriate kinetic and heat transfer modeling, have been used to predict the corresponding viscosity profiles. Molecular and thermocalorimetric parameters are used for the prediction of the theoretical chemorheological behavior. Commercial epoxy systems commonly used in the preparation of carbon fiber laminates have been characterized by Differential Scanning Calorimetry (DSC) and dynamic viscosity measurements and the results are compared with the theoretically predicted values.

Fumed silica dispersions in mineral or silicone oil are used to fill fiber-optic cables to prevent macro-bending of the fibers and to provide environmental protection. Adequate control of the rheology is essential for the effectiveness of the filling compounds: the materials must be sufficiently viscous to minimize stresses on the fibers but have considerable elasticity so as not to drip with time or temperature. The effects of shear history, aging, temperature, and water contamination on the rheological properties of two commercially available systems are studied using steady and dynamic measurements. The results are interpreted in terms of the microstructure resulting from the aggregation of submicron silica particles and their interactions with different solvents.

Series of 4-(4-substituted benzylideneamino)-5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazole-3-thiols were synthesized and their structures were confirmed. The synthesized Schiff bases were used as photostabilizers for polystyrene against photodegradation. Polystyrene polymeric films containing synthesized Schiff bases (0.5% by weight) were irradiated (λ max = 365 nm and light intensity = 6.43 × 10 −9 ein·dm −3 ·s −1) at room temperature. The photostabilization effect of 1,2,4-triazole-3-thiols Schiff bases was determined using various methods. All the additives used enhanced the photostability of polystyrene films against irradiation compared with the result obtained in the absence of Schiff base. The Schiff bases can act as photostabilizers for polystyrene through the direct absorption of UV radiation and/or radical scavengers.

The presence of additives influences the state of segregation of filler particles in the polymer matrix which in turn controls the electrical and mechanical properties of poly(vinyl chloride)-copper composites. The liquid plasticizer seems to form a coating on the filler surface which introduces quasirandomness in the segregated network. In accordance with the mathematical model proposed earlier, the strength properties were found to be proportional to dm−½ where dm is the mean free path between the filler particles. Calculations of dm were based on two different models, one for segregated network (unplasticized and low plasticized composites) and the other for quasi-random distribution of filler particles (plasticized composites). Extruded samples in general show more randomness in the filler distribution than the compression molded samples.

Sink marks are shallow depressions normally observed above reinforcing ribs in molded Sheet Molding Compound (SMC) parts. In this paper, the effect of mold geometry, particularly the rib entrance shape, on the flow pattern of molding compound and the resulting sink marks in molded parts is presented. Flat plate specimens with a single reinforcingrib in the center were used in this work. Rib entrance shape was varied and its effect on both sink depth and fiber orientation measured. A reduction in sink depth from 0.0007 in. to less than 0.0001 in. was observed when comparing rounded and protruding rib entrances, respectively. The effect of inducing unequal flow rates from the two sides of the rib was also investigated and found to give a reduction in sink depth of about one-third. A computer simulation of the flow during molding was used to compare observed flow patterns with simple theoretical predictions. The SMC was modeled as a highly viscous Newtonian fluid and finite difference methods were used to solve the Navier-Stokes equations. Extension of this modeling procedure to more complex geometries will aid in the design of nearly sink free molds.

Annihilation kinetics of color center in polycarbonate (PC), irradiated with gamma ray at elevated temperatures, was investigated. The transmission loss in the PC was monitored in the ultraviolet and visible wavelength range. The transmittance decreased with increasing gamma-ray dose. The loss was attributed to the presence of annealable and permanent color centers. The absorbance in situ data were detected at the wavelength of 450 nm and found in good agreement with the theoretical model in which the annealable color center followed a first-order kinetic process. The rate constant satisfies the Arrhenius equation, with the activation energy of the color centers decreasing with increase of the gamma-ray dose. The results were compared with the early findings reported in the literature.

An optical fiber probe has been constructed in order to obtain real-time measurements of fluorescence radiation during twin screw mixing and extrusion of plasticized polybutadiene and calcium carbonate particulate. The probe consists of an optical fiber bundle which was inserted along the axis of a half-inch sensor bolt, and it was used to transmit optical excitation energy to the processed material and to detect the subsequent fluorescence. The source of fluorescence radiation was a fluorescent dye which was doped into the processed ingredients at very low concentrations. Although most of our measurements were taken with the probe positioned close to the exit die, the sensor bolt can be placed in any instrumentation port along the extruder line. Experiments were carried out to measure residence time distribution, quality-of-mix, and mix concentrations as a function of processing conditions. Product mix changes in response to variations in material feed rates and screw RPM were also observed. Values of residence time were obtained by measuring the transit times for the dye to travel from an upstream injection port to the measurement probe, a distance of 63 cm. Flow instabilities, such as mat formation of the solids, were observed by noting the abrupt changes and discontinuities in the fluorescence signal.

Poly(N-vinyl-2-pyrrolidone) (PVP) is widely used in medicine due to its high biocompatibility. In this study, itaconic acid (IA) was co-polymerized with N-vinyl-2-pyrrolidone (NVP) monomer to prepare the pH sensitive hydrogels. These copolymer hydrogels were prepared using ultra-violet (UV) induced methods at ambient temperature. Monomer and cross-linking agent (N,N -methylene-bisacrylamide (MBAAm)) concentration effects on preparation of this copolymer hydrogel were investigated using swelling, FT-IR, and SEM. The prepared copolymer hydrogel is highly pH sensitive. The percentage swell of the copolymer hydrogels was found to increase from 150 to 3011% as the pH value of the swelling solution varied from 4 to 10. These pH sensitive copolymer hydrogels present a promising approach for drug delivery applications.

A new experimental technique for studying the dynamics of bubble growth in thermoplastics using scanning electron microscopy is developed. The influence of temperature, saturation pressure, molecular weight, and the nature of physical blowing agent are investigated. The experimental results show that the above process variables control the growth of foams during processing. The existing Newtonian model for the growth of a single bubble in an infinite amount of polymer has been modified to account for the non-Newtonian effects by modeling the polymer as a power law fluid. The experimental data has been compared with the appropriate viscoelastic cell model which considers the growth of closely spaced spherical bubbles during the foaming process. The simulation results indicate that the predictions of the cell model are in qualitative agreement with the trends of the experimental data and the quantitative agreement is reasonable. The cell model also gives an equilibrium radius which agrees with the experimental data. Other viscous models do not predict the equilibrium radius of the bubble and underpredict the experimental data.

Microphase-separated poly(styrene-b-ethylene-co-butyleneb-styrene) copolymers of different molecular weights with polystyrene (PS) volume fraction / 5 0.30 are investigated. Linear dynamic viscoelastic data reveal the blocking effect of the ordered PS microdomains, which produces a predominantly elastic response at low frequencies, associated with a mechanical relaxation. These results are correlated with tack and extrusion flow measurements, which involve polymer/metal adhesion processes. Nonlinearity implied in some experiments alters the ordered morphology of low molecular weight samples producing a viscous dominant behavior. Dissipation is reflected in viscous-like adhesion and lack of viscoplastic response in extrusion flow experiments. For the highest molecular sample, only a rubbery or entangled state (G 0 > G 00 and G 0 > 10 5 Pa) is observed in the linear viscoleastic regime. This is associated with the lack of adhesion seen in both, probe tack experiments and capillary flow measurements. This lack of adhesion gives rise to a plug-flow as the polymer slips in the capillary wall.

Heat transfer simulation within heating furnaces is of great significance for prediction and control of the performance of furnaces. In this paper, a set of models is proposed to solve heat transfer problems in a loaded furnace. Furthermore, a 2-dimensional algorithm based on a finite difference method is presented. The heat transfer models are integrated with a furnace model to simulate the heating process of workpieces. Temperature variation of the workpiece with time is predicted by the system. An experiment is carried out for validation of the system. Themain objective of this work is to evaluate the behavior of a heated enclosure, when variable radiant panels are introduced. Experimental investigation shows that their efficiency depends on their position.

Linear viscoelastic, steady shear behaviors, and morphologies of starch formate/poly(e-caprolactone) (PCL) blends, compatibilized by oligomers and obtained by reactive extrusion, have been investigated as a function of formic acid (FA)/starch ratio, nature, and molecular weight of the oligomer. The rheological properties of these blends have been compared with those of a commercial starch-based thermoplastic, namely Mater-Bi 1 ZF03UA. In presence of FA, starch is destructured to starch formate and oligomers are used as plasticizers. The linear viscoelastic response of blends is quite similar to that of nanocomposite materials: the low frequency behavior is attributed to a percolated network of destructured starch particles, and the high frequency behavior is that of the polymer matrix. The viscosity curve presents a profile characterized by two plateau regions, at low and high shear rates. The plateau region at low shear rates corresponds to the viscous response of the blend while that observed at high shear rates can be attributed to the PCL matrix. The compatibilization is enhanced in the presence of starch formate and increases with increasing the oligomer molecular weight. The use of PCL oligomer was shown to improve this compatibilization effect.

The thermo-mechanical history of thermosetting compounds in injection molding cavities influences the ultimate properties of molded articles and affects both moldability and the productivity of the process. Mathematical modeling is an attractive approach for obtaining information regarding the thermomechanical history of the compound in the cavity. In order to obtain useful mathematical models of the thermoset injection molding process, it is necessary to have information regarding. the kinetics and heats of reaction during cure; the rheological, thermal, and PVT properties of the thermosetting compound; and the variation ot these properties with operating variables and the degree of cure. The paper outlines a model of the thermoset injection molding process in simple rectangular or semi-circular cavities. Methods are described for the experimental determination of the various physical and chemical properties of thermosets, which are required for modeling purposes. The results obtained in conjunction with the characterization of an epoxy system are illustrated. Finally, the paper demonstrates the results of mathematical modeling of the injection molding process for a commercial epoxy molding compound in a semi-circular cavity, and shows that reasonable agreement is obtained between model predictions and experimental data.

Avaliadora Dedico este trabalho a Deus que me guia, minha esposa Marcia que me edifica e meus filhos Gabriel e Gustavo, que me fortalecem a prosseguir. AGRADECIMENTOS Agradeço a Deus pelo fôlego de vida, por seu amor e graça que nos direciona a cada dia. Por sua sabedoria que é compartilhada a nós, homens. Sem isso, nada do que há existiria. Agradeço a Marcia, minha esposa, por me dar o suporte nesse período de estudos e às vezes que estive ausente por esse motivo. Aos meus pais, Genésio e Aparecida, por me conceber, meus irmãos Danielle e Rafael, por serem meus companheiros desde sempre. Aos meus amigos da Indústria ARTEB que me apoiaram e auxiliaram neste projeto que foi muito importante para minha experiência profissional. Ao meu professor e orientador desta monografia Prof. Dr. Ronaldo Câmara Cozza, aos que compõem a banca examinadora e a todo o corpo docente da FATEC-MAUÁ, que não pouparam esforços em transmitir da melhor maneira, seus conhecimentos pedagógicos, técnicos e experiência de anos de dedicação.

Twin screw extruders can Le classified according to their geometrical configuration. The main distinction is made between intermeshing and nonintermeshing extruders. Another distinguishing characteristic is the sense of rotation. The most important characteristics of the various twin screw extruders are examined, with particular emphasis on the effect of screw geometry on the conveying characteristics. A brief review is given of the state of the art in theoretical analysis of twin screw extruders. Experiments with two lab scale, intermeshing twin screw extruders are described, one co-and one counterrotating. Results are presented on power consumption, residence time distribution, and mixing characteristics of the two extruders. The counterrotating extruder exhibits a narrower residence time distribution and better dispersive mixing capability. The corotating extruder showed a better distributive mixing capability. These results can be explained in terms of the conveying and mixing mechanisms in both extruders. The overall extruder performance seems to be dominated by the effect of the intermeshing region. Any realistic, theoretical analysis oftwin screw extruders should be centered around the flow behavior and mixing characteristics of the intermeshing region. The corotating extruder appears to be best suited for melt blending operations, while the counterrotating extruder seems to be preferred in operations where solid fillers have to be dispersed in a polymer matrix.

A series of random poly(ethylene-co-1,4-butylene terephthalate)s (PEBTs), as well as poly(ethylene terephthalate) (PET) and poly(1,4-butylene terephthalate) (PBT), were synthesized by the bulk polycondensation. Their composition, molecular weight, and thermal properties were determined. All the copolymers are crystallizable, regardless of the compositions, which may originate from both even-atomic-numbered ethylene terephthalate and butylenes terephthalate units that undergo inherently crystallization. Non-isothermal crystallization exotherms were measured over the cooling rate of 2.5-20.0 K/min by calorimetry and then analyzed reasonably by the modified Avrami method rather than the Ozawa method. The results suggest that the primary crystallizations in the copolymers and the homopolymers follow a heterogeneous nucleation and spherulitic growth mechanism. However, when the cooling rate increases and the content of comonomer unit (ethylene glycol or 1,4-butylene glycol) increases, the crystallization behavior still becomes deviated slightly from the prediction of the modified Avrami analysis, which is due to the involvement of secondary crystallization and the formation of relatively low crystallinity. Overall, the crystallization rate is accelerated by increasing cooling rate but still depended on the composition. In addition, the activation energy in the non-isothermal crystallization was estimated.

In this research the variation of mechanical and rheological properties of the composite as a function of different processing parameters and ethylene propylene diene monomer (EPDM) rubber content was studied. The optimum amount of dicumyl peroxide (DCP) to achieve the highest percentage of grafting of maleic anhydride to EPDM was obtained by Fourier transform infrared (FTIR) spectroscopy. In general, immiscibility between nylon 66 and EPDM, and their high interfacial tension makes their blending difficult. Maleic anhydride was grafted to EPDM to reduce interfacial tension between two phases. Also the blends were prepared at highest possible speed of mixing (screw speed in extrusion) and lowest temperature to reach a well mixed sample which can be seen in scanning electron microscopy (SEM) images and impact strength results. Dynamic mechanical thermal analysis (DMTA) tests were conducted to evaluate the miscibility of the components and to measure the glass transition temperature of...

Nowadays modern commercial simulation software provides acceptably faithful representation of reality, assuming the correctness of boundary conditions and reliability of data of processed composite material. In the case of non-standard plastics which include polyimide, we do not always have access to the target material and we do not have proper equipment to produce such products. Due to very interesting properties of the polyimide and its low popularity in use as an injection moulding material, the analysis of injection moulding of tooth plastic gear made from carbon fiber-polyimide composite was made. In this work the chosen material data, necessary for the numerical analysis, were presented. The impact analysis of main factors controlling the volumetric shrinkage during injection moulding processing was conducted. It was found that the greatest impact on the quality criterion is the melt temperature. To optimize control factors, the Taguchi orthogonal plans were used. In addition, the issue of polyimide properties, the possibility of its injection moulding and applications was discussed.

We investigate the viscosity dependence on
concentration and molecular weight of semiflexible polyelectrolyte
sodium carboxymethylcellulose (NaCMC) in aqueous salt-free and
NaCl solutions. Combining new measurements and extensive
literature data, we establish relevant power laws and crossovers
over a wide range of degree of polymerization (N) as well as
polymer (c) and salt (cs) concentrations. In salt-free solution, the
overlap concentration shows the expected c* ∝ N−2 dependence,
and the entanglement crossover scales as ce ∝ N−0.6±0.3, in strong
disagreement with scaling theory for which ce ∝ c* is expected, but
matching the behavior found for flexible polyelectrolytes. A second crossover, to a steep concentration dependence for specific viscosity (ηsp ∝ c3.5±0.2), commonly assigned to the concentrated regime, is shown to follow c** ∝ N−0.6±0.2 (with c**/ce ≃ 6) which thus suggests instead a dynamic crossover, possibly related to entanglement. The scaling of c* and ce in 0.01 and 0.1 M NaCl shows neutral polymer in good solvent behavior, characteristic of highly screened polyelectrolyte solutions. This unified scaling picture enables the estimation of viscosity of ubiquitous NaCMC solutions as a function of N, c, and cs and establishes the behavior expected for a range of semiflexible polyelectrolyte solutions.

In this article we study thixotropic and time-dependent rheological behavior of commercial acrylic emulsion paint using a framework of soft glassy rheology. We observe that acrylic emulsion paint, which shows thixotropic rheological behavior, demonstrates various characteristic features of a soft glassy materials such as weak but certain increase in elastic modulus as a function of aging time, maximum in viscous modulus as a function of strain at the onset of yielding, and slow increase in elastic modulus as a function of frequency. Stress relaxation measurements, subsequent to step strain, carried out at different aging times demonstrate slowing down of the relaxation dynamics. This behavior is similar to that observed in polymeric glasses and other soft glassy materials undergoing aging dynamics. Relaxation modulus when plotted against appropriately rescaled time yields a superposition irrespective of the aging time. The rescaled time also known as effective time, which adjusts the material clock by accounting for increasing relaxation time, enables estimation of the rate of change of relaxation time with the aging time. We conclude by relating thixotropy in an emulsion paint sample to an interplay between physical aging and shear melting in the same.

PVC plastisols were formulated with silicone surfactant, mechanically shipped to form froths, and oven-fused to form open-cell foams. These were much softer than conventional chemically-blown foams which contain mixtures of open and closed cells. Increasing plasticizer content and decreasing foam density also had the expected softening effects on foam properties.

The thermoplastic polymer blends of commercial interest generally need a phase compatibilization to reduce the interfacial tension, to stabilize the morphology, and to increment the interfacial adhesion. This work deals with the compatibilization of PP/PS blends by addition of a tailor-made copolymer, which is prepared from the pure homopolymers by a Friedel-Crafts reaction. This addition compatibilization process comes out as an economic alternative applicable to the recycling of mixed plastics from urban and industrial wastes. The influence of compatibilizer concentration and blending time on the emulsifying effect, morphology, and mechanical properties of the resulting blends are analyzed. The compatibilization process effectiveness is assessed through the improvement in phase adhesion, emulsification and ductility of the compatibilized with respect to the physical blends. An increase of three times in ductility is achieved using very low compatibilizer concentrations (0.5-0.7 wt%). No appreciable detriment in yield strength or modulus is observed in these compatibilized blends. POLYM. ENG. SCI., 46:329 -336, 2006.

The dynamic mechanical properties in terms of the storage modulus E′, loss modulus E″, and the loss tangent δ has been studied for highly filled magnetic polymer composites. The effect of surface treatment on the relaxation spectra has been clearly elucidated and quantitative values indicating the extent of polymer–filler interactions have been given. Various models have been tested for describing the viscoelastic behavior of such highly filled systems. The Wiechert model using a single-arm with a Cole–Cole parameter has been shown to effectively fit the Argand diagram in the case of the present highly filled systems

Polymer-clay nanocomposites are materials with many interesting structures, properties, and potential applications. Microstructural evaluation of a nanocomposite is not an easy task, as clay may form hierarchical structures which may look different when observed at various magnifications under a microscope, and also as the concepts of ''intercalation'' and ''exfoliation'' are not self-sufficient to describe its morphology. In this work polymer-clay nanocomposites of polystyrene and two styrene-containing block copolymers (styrene-butadiene-styrene and styrene-ethylene/butylene-styrene) were prepared using three different techniques. Clay dispersion was evaluated by a recently developed microscopy image analysis procedure, combining the analysis of optical and transmission electron micrographs, and the characterization was complemented by X-ray diffraction and rheological measurements. The results showed better clay dispersion for both block copolymers nanocomposites, mainly due to their molecular architectures. Moreover, the techniques which showed the best results involved mixing the materials in a solvent medium. POLYM. ENG. SCI.,

Despite seven decades of intense research, the generally accepted insertion mechanism (IM) has generated many open questions. It is shown in this paper why IM is incorrect and nonsense. We reexamined the fundamental presumption of this polymerization, evaluated the roles of each basic component and proposed an alternative mechanism by electric charge percolation (CPM).

Injection molding is one of the most widespread processes for plastic manufacturing. Software packages are often used in several steps of the production cycle, from mold design to the determination of processing conditions. In this work a method is reported to improve the predictions of the description of pressure profiles made by injection molding simulation software. The method is applied to two polymeric materials (a PolyStyrene and a PolyCarbonate) injection molded into linegated rectangular cavities adopting different molding conditions and cavity thickness. The method, that is independent of the software adopted, in this paper is illustrated adopting the commercial code Moldflow®. It is shown that the predictions of the description of pressure curves inside the cavity can be significantly improved by introducing the effect of pressure on viscosity and the effect of cavity deformation during molding. The former effect is taken into account by finding an appropriate value for the parameter which takes into account the effect of pressure in the equation which describes material rheology. The latter effect can be introduced by defining and implementing an apparent material compressibility.

The objective of this research work was to gain a better understanding of the mechanical properties of epoxy resin composites reinforced with carbon fiber. For this purpose, the effects of fiber orientations, resin types, and number of laminates on mechanical properties of laminated composites have been investigated. In the sample preparation, composites were manufactured by hand lay-up process, using a fiber-to-resin ratio of 40:60 (w:w). To investigate the effect of fiber orientation, angles of 0 , 35 , 45 , and 90 were selected. Results show that the mechanical properties, in terms of tensile, flexural and impact strengths, were mainly dependent on the fiber orientations followed by the number of laminates. At a similar fiber orientation, the composites made with EM500 epoxy resin showed the highest mechanical properties (such as tensile and flexural and impact strengths) compared to other evaluated composites. However, the differences were not highly significant. The results indicated that the mechanical properties of composites made with fiveply were generally slightly greater than three-ply composites. It may be due to the bondline defects, which adversely influence the mechanical properties. Scanning micrographs of the composites showed that the epoxy matrix material was fully adhered to the fibers, indicating a strong interface. It can be concluded that the order of increment parameters in the mechanical properties of the composites is fiber orientation > number of laminates > resin type. In addition, the tensile and flexural properties were superior in case of AE35 fiber orientations.

The objective of this work is to validate predictive models for the simulation of the mechanical response of polypropylene undergoing impact situations. The transferability of material parameters deduced from a particular loading scenario (uniaxial loading) to a different loading situation (multiaxial loading) was studied. The material was modelled with a modified viscoplastic phenomenological model based on the G'Sell-Jonas equation. To perform the numerical simulations, a user-material subroutine (VUMAT) was implemented in the ABAQUS/explicit finite element code. Constitutive parameters for the model were determined from isostrain rate uniaxial tensile impact test data using an inverse calibration technique. In addition, falling-weight low-energy impact tests were performed on disc-shaped specimens at velocities in the range 0.7 to 3.13 m s −1 . The model predictions were evaluated by comparison of the experimental and finite element response of the falling-weight impact tests. The G'Sell-Jonas model showed much better predictability than classical elastoplasticity models. It also showed excellent agreement with experimental curves, provided stress-whitening damage observed experimentally was accounted for in the model using an element failure criterion.

The impact behavior of a low-density polyethylene was studied with an instrumented Charpy tester. A change from elastic or ductile response to brittle fracture was observed over a small temperature interval, usually within 1°C. This characteristic impact transition temperature (ITT) was highly sensitive to shallow, sharp notches. Whereas an unnotched test bar had a very low impact transition temperature of -94"C, a razor cut with a depth of only 5 percent ofthe total thickness raised it to -4°C. The impact transition temperature was effectively reduced by increasing the cooling rate during specimen preparation and by the addition of nonpolar liquids. On the other hand, impact properties were adversely affected by aging, annealing, and adding other thermoplastics.

Resin rich zone along component edges is a common phenomenon during composites liquid infusion with the resin transfer moulding process. The challenge in the present work is to be able to predict the realistic racetrack flow behaviour along a 90° edge in order to manufacture high-quality composites materials for aerospace or other applications. To that end, there is a lack of an advanced simulation tool capable to predict the manufacture of multi-layer textile composites. The issue of 2D, 3D racetrack prediction on this paper was investigated along a 90° edge for a composite textile. A novel numerical approach for a three-dimensional Finite Element Control/Volume modelling was developed in order to predict race-tracking permeability for any composite structure. The model was experimentally verified for a 2/2 twill carbon fibre geometry. All experiments and simulations used 1 bar pressure and 300 mPa.s viscosity.

In this work the blends of long chain branched polypropylene (BPP) and chain extended/branched PET (MPET) were prepared and the melt and crystallization characteristics, rheological properties in shear and elongational mode for BPP, MPET and their blends in correlation with their morphology were studied with various amounts of PP grafted maleic anhydride as compatibilizer. BPP is prepared by using dicumyl peroxide and trifunctional monomer trimethylolpropane trimethacrylate (TMPTMA) and MPET were prepared by using tetrafunctional modifier pyromellitic dianhydride (PMDA) and pentaerythritol (PENTA). The rheological study showed the increase in melt shear and elongational strengths of MPET after the chain extension process and increase in shear thinning and strain hardening behavior of modified samples. The zero shear viscosity and shear thinning index of PET increased from 210 Pa s and n 0 ¼ 0.15 to 315 Pa s and n 0 ¼ 0.22 after modification and for PP they decreased from 4940 Pa s and n 0 ¼ 0.54 to 1170 Pa s and n 0 ¼ 0.45. These results prove that increase in molecular weight and widening of molecular weight distribution are the major consequences of PET modification and chain scission;