bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Milling Behavior and Characteristics of Bi2Te3 Thermoelectric Materials
Authors: Babu M. , Kim H.-S. , Kim H.-Y. , Hong S.-J.
Published: December 2013

In this paper, starting from the gas atomization powders, n-type Bi2Te3 thermoelectric alloys prepared via high energy ball milling and subsequently consolidated by hot extrusion. The effect of ball milling on the microstructure of Bi2Te3 alloys was studied. With increasing the milling time, from 3 min to 90 min, the particles were coarsening due to the agglomerated because of the high surface energy of the fine particles adhesive each other during the high energy ball milling. The preferential orientations of grains indicate that the extrusion process has the significant method to forcing the basal plane to orient preferentially in the extrusion direction were clearly observed by the TEM micrograph. The maximum electrical conductivity 6675.567 Ω−1m−1 measured at 100 °C temperature owing to the increasing of carrier concentration due to the donor defect formation and contamination occurred during the high energy ball milling at longer milling time (90 min).
Characterization of Oxidation Resistance of Stainless Steels at High Temperature by Metallographic Examinations and In-Situ Electrical Resistance Measurements
Authors: Bruncko M. , Rudolf R. , Mehrabi K. , Kneissl A. C. , Anzel I.
Published: December 2013

Practically all metals and alloys survive high-temperature exposure by growing oxide scales and/or by precipitation of the oxide particles in the matrix. Formed products can grow in shape of external oxide layers on surfaces, or as discrete oxide particles precipitated in a metal matrix. The first case represents external oxidation, and the other case is called internal oxidation. These processes are very important, because they determine the properties and applicability of metallic materials. Generally, they are undesired, because they cause deterioration of the mechanical properties and decomposition of metallic material. On the other side, the controlled process of external oxidation could be used for formation of protective coatings and the internal oxidation for dispersion strengthening of materials.

In this paper we present monitoring of high-temperature oxidation of X12Cr13 stainless steel by in-situ electrical resistance measurements at different annealing temperatures in the air atmosphere. We determined the kinetics of oxide scale formation and its morphology with additional metallographic examination made by optical and scanning electron microscopy. The results of this research work show that in-situ monitoring and characterization of high-temperature oxidation present a strong tool that will contribute to a better fundamental understanding of the phenomena that occur during high-temperature oxidation of metallic materials.
Analysis of Stray Grain Formation in Single Crystal CMSX-4 Superalloy
Authors: Chmiela B. , Szeliga D. , Sozańska M. , Jarczyk G. , Cwajna J.
Published: December 2013

Modern single crystal (SX) turbine blades are fabricated by directional solidification using a grain selector. The grain selection process was investigated by numerical simulation and verified by the experiment. A coupled ProCAST and cellular automaton finite element (CAFE) model was used in this study. According to the latest literature data, we designed the grain selector. Simulation confirmed an optimal grain selection efficiency of the applied selector geometry. The obtained experimental results reveal the possibility of stray grain formation in SX castings with a designed selector, in contrast to the simulation results.
X-Ray Computed Tomography as Supporting Technology in The Failure Analysis of Press-In Connections for Electronic Assemblies
Authors: Rauer M. , Schreck T. , Kaloudis M.
Published: December 2013

Besides its original field of application–the characterization of microstructures–the metallography is often referred to when analyzing failures of electronic components and assemblies. In this context, the cause of the failure is analyzed by means of a metallographic section. At this point, the precondition and difficulty is the right choice of the section plane. If it is not optimally selected, there is a risk of overlooking the defect and therefore of not recognizing important correlations. The X-ray computed tomography is an efficient method which helps making the right choice and facilitates a targeted metallographic preparation. Conspicuous features inside the damaged component can be detected in advance by means of a three-dimensional volume model established by computed tomography. Based on this information, an appropriate cutting plane can be chosen in the volume model and a targeted metallographic section can be prepared. In the following, it is possible to view the conspicuous spot with high resolution and to analyze its microstructure in selected areas. In order to demonstrate the use of computed tomography as a supporting technology in the target preparation, the following article establishes a link between both testing technologies and their application to the press-fit technology which serves as joining technology when assembling electronic components.
Multiple Fractures of Used In-Service Disc Springs in a Stationary Gas Turbine Engine
Authors: Neidel A. , Cagliyan E.
Published: December 2013

Multiple cracking was observed in disc springs made from an austenitic stainless steel and used in large stationary gas turbine engines. It was determined that they failed in service by bending overload. The metallurgical cause of the cracking was found to be grain boundary embrittlement by secondary chromium carbide precipitates. They formed upon heat treatment during manufacture of the components. It was recommended to either alter heat treatment parameters to avoid embrittlement, or to select a different spring steel that does not require heat treatment.
Embrittlement of Fuel Gas Piping Made of Wrought Nickel-Based Superalloy Due to Inadequate Heat Treatment
Authors: Neidel A. , Gädicke T.
Published: December 2013

Cold-drawn and cold-bent seamless Alloy 617 pipes were received by a gas turbine engine manufacturer for final assembly. They exhibited multiple cracking on the surface. The extrados of bending zones were most affected by this condition. It was determined that the metallurgical root cause of the problem was inadequate heat treatment by the supplier of the semi-finished product. The cracking upon cold bending the seamless pipes was caused by embrittlement of the pipes’ surface due to nitridation and a further drop in formability as a result of grin boundary embrittlement by secondary carbide precipitates.
The Preparation of Metallic Joinings to Optimise their Topography
Authors: Herbst S. , Jablonik L. , Gerstein G. , Nürnberger F. , Bach F.-W.
Published: December 2013

Modern light structures increasingly require different alloys or metals to be joined with one another in the form of composite materials [1]. As a result of their different melting temperatures or of the formation of brittle inter-metallic phases, many combinations of metals cannot be produced using thermal methods. One alternative, however, is the use of solid state welding such as explosive or magnetic impulse welding [2; 3]. The examination and analysis of the bonding interfaces is therefore of central importance in the evaluation of the quality of the bond produced. Scanning electron microscopy together with electron probe micro­analysis of the characteristic X-rays emitted using EDX and WDX techniques can reveal information regarding the distribution of the metals present within the bonding interface [4], the presence of inter-metallic phases [5] and of areas of inadequate bonding. For an accurate evaluation of the characteristic X-rays produced, however, the surface of the specimen must be guaranteed to be both flat and smooth in order to prevent the effects of shadowing and deflection of the primary beam which might otherwise cause erroneous results in the elements present and their distribution [6]. A specimen surface which is not perfectly flat also makes it difficult to focus the electron beam.

The simultaneous flat and smooth preparation of metallic composites which have very different strength and hardness properties is very difficult due to the different rates of removal of material during grinding and polishing [7; 8]. In view of this, the following methods of preparation used to produce flat and smooth specimen surfaces on two types of metallic joinings are presented.
Mapping the Local Structure of Nanowires
Authors: Persson J. M. , Wagner J. B.
Published: December 2013

The crystallographic and compositional structure of heterostructured semiconductor nanowires has been studied by means of transmission electron microscopy. The native geometry of the studied InP-GaAs nanowires (80–100 nm in diameter) is in general too thick for reliable high-resolution TEM imaging. Nano Beam Electron Diffraction (NBED) is shown to be a powerful technique to reveal strain near the interface of compositional change in heterostructured semiconductor nanowires. Furthermore, the relative orientation of the nanowires is studied by means of NBED revealing the nanowires to be very flexible. NBED proves to be a good alternative to convergent beam electron diffraction and electron backscatter diffraction in terms of crystal orientation determination and mapping.
Effect of Distributor Geometry on Crimp Contraction of PET Side-by-side Bicomponent Fibers
Authors: Oh T. H.
Published: December 2013

The effect of distributor geometry on crimp contraction in the melt spinning and drawing of polyethylene terephthalate (PET) side-by-side bicomponent fibers was studied. Three different distributors located on top of the spinneret were designed to change curvature ratio of a side-by-side cross-section of bicomponent fibers. Regular and modified PET were selected to make latent crimp yarns. Spinning and drawing conditions were changed to choose the effective variables heat set temperature and draw ratio. Crimp contraction increased with increasing draw ratio and decreasing heat set temperature. Die geometry had a significant effect on crimp contraction by changing the curvature ratio of the cross-section. Under the same spinning and drawing conditions, the crimp contraction with higher curvature ratio was larger.
Modeling and Practice of Ethanol-devolatilization of Silica-silane Rubber Compoundsin an Internal Mixer
Authors: Dierkes W. , Noordermeer J. W. M.
Published: December 2013

During mixing of a rubber compound containing silica and silane, the mixer is not only used for the dispersion of the filler and other ingredients, but also for a chemical reaction. These two functionalities of the mixer result in opposite processing requirements: A good dispersion is reached by high shearing forces, increasing the compound temperature. The silanization is not dependent on high shearing forces; it is positively influenced by high temperatures, but with an increasing risk of scorch. Another drawback is the equilibrium between the ethanol concentration in the vapor phase in the void space of the mixing chamber and in the rubber phase, which is limiting the reaction rate of the silanization. Devolatilization of the compound is a crucial factor for the efficiency of the silanization reaction.

In this article a model for devolatilization of a rubber compound in an internal mixer is developed, including a chemical reaction replenishing the volatile component during the devolatilization process. The model is based on the penetration theory, with the main contribution to the devolatilization being convective mass transfer. The main influencing factors, theoretically deducted and practically verified, are temperature, mixer volume, fill factor, rotor speed, reaction time and partial pressure of the volatile component in the void volume of the mixer.
Paste Extrusion of Polytetrafluoroethylene: Temperature, Blending and Processing Aid Effects
Authors: Ochoa I. , Hatzikiriakos S. G. , Mitsoulis E.
Published: December 2013

Blends of different PTFE fine powder resins have been prepared and extruded in an attempt of improving the PTFE paste extrusion process and/or the extrudates. The extrusion pressure and the mechanical properties of the extrudates were found to fall between those exhibited by the pure components. While this is an expectable behavior, it offers opportunities for controlling the degree of fibrillation needed in the final products by mixing highly fibrillated with low fibrillated PTFE resins. Boron nitride and organically modified montmorillonite clays (solid lubricants) are also tested as additives to the lubricants used in the PTFE paste extrusion in order to identify enhanced processing aids. It was found that the addition of boron nitride and clays increase the extrusion pressure but at the same time improve the mechanical properties of the final extrudates in most cases. This again offers possibilities for controlling the final mechanical properties by controlling the degree of fibrillation, i. e., by adding a small amount of solid lubricants to adjust pressure, fibrillation, and thus the final mechanical properties. Finally, it is shown that fibrillation depends on temperature. Moreover, the mechanical properties of extrudates increase as the temperature goes through its two transition temperatures of 19 °C and 30 °C that render PTFE particles more deformable and prone to fibrillation.
A Process Classification Number for the Solidification of Crystallizing Materials
Authors: Janeschitz-Kriegl H. , Eder G. , Ratajski E.
Published: December 2013

A critical number, which one may call a process classification number, has been introduced more than twenty years ago [1, 2, 3]. It has been called the Janeschitz-Kriegl number Jk [4]. It gives the ratio of two times governing the solidification process of a crystallizing material: one for the thermal equilibration and the other for the crystallization process itself. With one class of materials (mainly metals) the thermal equilibration time is usually the longest time, dependent of course on the sample thickness. With another class (glass forming minerals) always the crystallization time is the longest time. So, one obtains (as extreme cases) purely heat diffusion controlled and purely crystallization kinetics controlled processes. Only polymers (and probably also other crystallizing soft condensed matters) show an intermediate behavior, as can be characterized by the announced number.

So far, however, this number could not be made operational because of a lack of crystallization kinetics data. This shortcoming could now be cleared away. It turns out that between the values of Jk for HDPE and for i-PS a gap exists of more than six decades. In their behavior all other known industrial polymers lie between these limiting cases. In this way the transition from heat diffusion controlled to crystallization kinetics controlled processes is clearly marked. For the now relevant interaction between cooling and crystallization a new mathematics was required [2]. It enables also the description of the development of structures, which are of particular interest for the quality of the product.
Welding of Plastics: Fundamentals and New Developments
Authors: Grewell D. , Benatar A.
Published: December 2013

This paper provides a general introduction to welding fundamentals (section 2) followed by sections on a few selected welding processes that have had significant developments or improvements over the last few years. The processes that are discussed are friction welding (section 3), hot plate welding (section 4), ultrasonic welding (section 5), laser/IR welding (section 6), RF welding (section 7) and hot gas/extrusion welding (section 8).
Preparation and Characterization of HMW PA 6 via Anionic Polymerization of ∊-Caprolactam by Using a Mixture of Di- and Tri-functional Chain Initiators
Authors: Barmi M. M. S. , Assempour H. , Nazockdast H.
Published: December 2013

In the present work, an attempt was made to synthesis polyamide 6 through anionic polymerization of e-Caprolactam by using a mixture of Diphenylmethan 4, 4-di and tri-isocyanate as a chain initiator and sodium caprolactamate as a catalyst. Polymerization was carried out in a laboratory internal mixer (Brabender). The rotor speed, reaction temperature and reaction time were among the processing variables studied. The prepared samples were characterized by Thermogravimetry Analysis (TGA), Differential Scanning Calorimeter (DSC) and FT-IR spectroscopy. The flow behavior and melt viscoelastic properties of the samples were studied by using a Rheometric Mechanical Spectrometer (RMS). The polymerization reaction was found to be very fast and was completed within 6 minutes. This was detected by following the mixing torque which reached to a steady state after passing through a maximum. The pronounced decrease in the torque was found to be determine by the thermomechanical degradation as a predominating mechanism. The polyamide 6 prepared in this work showed greater melt elasticity, much higher molecular weight and slightly narrower molecular weight distribution in comparison with the commercial grades of polyamide 6. The crystallinity of the samples was also higher than that of the commercial polyamide 6. These results were explained in terms of contribution of fraction of the molecules possessing single long chain branch formed as a result of three functional nature of the chain initiator. Increasing the rotor speed was found to have strong influence on lowering molecular weight as well as narrowing the molecular weight distribution through increasing the extent of thermomechanical degradation. Increasing the initial set temperature in the studied range had no appreciable effect on polymerization rate and degree of conversion. It was demonstrated that the results of melt viscoelastic measurements performed on the samples collected at different polymerization times can provide valuable information to follow the polymerization reaction.
Method for the Optimisation of Screw Elements for Tightly Intermeshing, Co-rotating Twin Screw Extruders
Authors: Potente H. , Thümen A.
Published: December 2013

Demanding mixing tasks are usually solved through the use of tightly intermeshing, co-rotating twin screw extruders. Since both the barrel and the screw are of a modular design, the extruder can be optimised for a given task. In the framework of this investigation, the screw-element geometry for tightly intermeshing co-rotating twin screw extruders is optimised in order to achieve specific aims. The threaded elements have been optimised for different materials and operating conditions.

The investigation set out to achieve a screw-element geometry that would generate the maximum pressure gradient while, at the same time, ensuring that the temperature increase and the power consumption were kept to a minimum. The pressure profile, the temperature progression and the power consumption have been calculated on the basis of one-dimensional models of the type used in the SIGMA process simulation software. The geometrical data of the individual elements was varied with the aid of non-linear algorithms, and the quality of an individual geometry was assessed on the basis of quality functions. Subsequent to the theoretical optimisation, experimental analyses were performed for purposes of verifying the optimisation method used.
Structure Development in Melt Spinning and Cold Drawing of Poly(ethylene-co-octene) Copolymer
Authors: Shan H. , White J. L.
Published: December 2013

An experimental study of melt spinning and cold drawing of polyethylene and its Dow Chemical INSITEØ catalyst octene copolymers was carried out. The structure and morphology of both melt spun and cold drawing fibers were investigated using wide angle x-ray diffraction (WAXD), small angle x-ray scattering (SAXS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and birefringence. Up to 5.9 mol.% octene, the fibers exhibit only the Bunn orthorhombic crystal structure. Fibers with 9.7 mol.% and 13.3 mol.% octene, whose DSC crystallinity is 0.23 and below, have an additional reflection at about 0.45nm. The Hermans-Stein orientation factors for the melt spun fibers were determined and correlated with spinline stress. Cold drawn polyethylene fibers exhibited additional reflection at 0.45, 0.38 and 0.35nm which may be associated with the Tanaka-Seto et al. monoclinic unit cell. The copolymers contained a decreased monoclinic level which disappears at about 5.9 mol.%. However, a broad reflection at 0.45nm, reappears at 9.7 mol.% octene. This reflection is also present at the 13.3 mol.% level. It is surmised that a pseudohexagonal or mesomorphic structure is developing. The Hermans-Stein orientation factors were determined for the drawn fibers as a function of cold draw ratio. Drawing results in high crystalline orientation and fibrillation for polyethylene fibers. For copolymers, with higher octene content, the fibrillation decreases.
Experimental Investigation of the Cooling Flow in the Film Blowing Process
Authors: Peters F. , Ruppel C.
Published: December 2013

The film blowing process relies on external air cooling of the extruded polymer hose. The air is supplied by a ring nozzle surrounding the die. We investigate the flow as it emanates from a commercial nozzle by a laser light sheet method which reveals the instantaneous rather than the mean flow structure. Flow separation in the nozzle is diagnosed as well as a high degree of disturbances affecting the thermal boundary layer. To improve the flow a modified nozzle is investigated in the same way, which shows how separation is avoided and how the regular structure of a wall jet is attained. The limits of this approach are highlighted. The optical measurements are amended by pressure measurements inside and outside the nozzle. They show what the flow disturbances mean in terms of normal forces on the film.
Mechanical Properties of Rubber-toughened Post-industrial Glass-fiber-reinforced PA66
Authors: Alsewailem F. D. , Gupta R. K.
Published: December 2013

When compounding engineering thermoplastics with glass fibers for reinforcement purposes, a tremendous amount of polymer-containing waste is generated. However, the polymer of interest is usually commingled with the polymer used to purge the extruder. Reclaiming valuable polymer from this waste is hindered by the incompatibility with the purging material since this leads to a blend system that has poor mechanical properties and low economic value. For this reason, this potentially valuable post-industrial polymer-waste is normally land filled. The current research is directed at the characterization and reuse of a post-industrial PA66 filled with glass fibers; this was separated from LDPE purge material and its impact resistance was modified through rubber toughening. Styrene-Ethylene-Butylene-Styrene and Ethylene-Propylene elastomers grafted with maleic anhydride (SEBS-g-MA and EP-g-MA respectively) were used as the toughening agents in this study due to their compatibility with PA. Izod impact strength, tensile strength and modulus, flexural strength, and elongation at break were used to characterize mechanical properties of the rubber-toughened recycled glass-filled PA66. The morphology of the fracture surfaces of the composites was examined by Scanning Electron Microscopy (SEM). It was found that both impact strength and elongation at break increase with increasing rubber content while flexural strength and tensile strength suffer upon incorporating rubber; however, by adding moderate amounts of rubber to the recycled glass-fiber-reinforced PA66 a balance between stiffness and toughness of the material could be obtained. For example, the addition of 10 wt.% of SEBS-g-MA to the recycled PA66 with 23.62 wt.% glass fiber loading resulted in a 27% and 151% increase in tensile strength and impact strength respectively of the blends when compared with neat PA66. This suggests that compounding both glass fibers and elastomers with PA66 is a useful strategy to recycle PA66, especially for reuse in under-the-hood automotive applications.
Effect of Compatibilizer Distribution on Thermal and Rheological Properties of Gelatinized Starch/Biodegradable Polyesters Blends
Authors: Xie F. , Yu L. , Liu H. , Dean K.
Published: December 2013

Thermal and rheological properties of various blends of gelatinized starch and biodegradable polyester, polycaprolactone (PCL) or poly(butylene succinate adipate) (PBSA), were studied by DSC, TGA and rheometry. Methylenediphenyl diisocyanate (MDI) was used as a compatibilizer and was distributed in different phases through controlled processing. The addition of MDI showed a stronger effect on thermal and rheological properties when it was mainly distributed in the polyester phase prior to blending. Starch was shown to increase the shear viscosity of both types of polyesters. The two blends, starch/PCL and starch/PBSA, showed a similar pattern of a power law dependence of viscosity on shear rate. MDI was shown to enhance the effect of starch on the melting and decomposition temperatures, especially when distributed in the polyester phase.
Study of the Compatibilizer Effect on Blends Prepared from Waste Poly(ethylene-terephthalate) and High Density Polyethylene
Authors: Kratofil L. , Hrnjak-Murgić Z. , Jelencć J. , Andricć B. , Kovacć T. , Merzel V.
Published: December 2013

In this work mechanical recycling of waste poly(ethylene-terephthalate) (PET) in the presence of high density polyethylene (HDPE) was studied. The fraction of HDPE in PET/HDPE blends was 3, 5, 6 and 10 wt.%. Isocyanate HI compatibilizer was first synthesized and then added to the blends at a fraction of 5 wt.%. Ethylene-propylene-diene masterbatch (EPDM-M) was prepared by mixing and added in fraction of 15, 30 and 50 wt.%. All PET/HDPE blends studied were characterized by scanning electron microscopy SEM, differential scanning calorimetry DSC and melt flow rate (MFR). Blends prepared with isocyanate HI compatibilizer were also studied by FTIR spectroscopy. Appearance of new vibrations in the FTIR spectra confirms that during the blending reactions between isocyanate HI compatibilizer and blend components appear. Results show that used compatibilizers significantly improved compatibility of polymers in studied blends. From the results it is obvious that immiscibility of PET and HDPE can be overcome.
Melting Temperature Characteristics for Polyethylenes from Crystal Size Distribution
Authors: Feng L. , Kamal M. R.
Published: December 2013

Semi-crystalline polymers exhibit broad and multiple peaks in their melting traces. Thus, the melting temperature characteristics of polymers should consider both melting peak positions and melting temperature polydispersity. In this work, the effective melting temperature and temperature polydispersity are defined and calculated from DSC traces, using the crystal size number distribution and the melting temperature equation. Three methods are proposed for calculating melting temperature characteristics. These methods are based on: (i) average crystal size, (ii) the crystal stem number distribution function, and (iii) the monomer structural unit distribution function. They were employed to analyze the isothermal and non-isothermal experimental results for polyethylene polymers, especially linear low-density polyethylene copolymers. The first method, based on the value of average crystal size, gives the most reasonable results, taking into consideration agreement with experimental observations and structural data.
A Numerical Investigation on the Cure Cycle of Composite Brake Blocks
Authors: Shojaei A.
Published: December 2013

Composite friction materials used in the braking system of vehicles are composed of different ingredients (typically up to 20 materials). The overall physical properties of these products are determined by the type and percentage of the individual ingredients in the final composition and consequently, may differ from one product to another. This paper studies the cure characteristics of railroad composite brake blocks during compression molding. Numerical simulations using the control volume/finite element method (CV/FEM) are utilized to predict temperature fields and cure conversion during the process. As railroad brake blocks are normally thick-sectioned parts, a three-dimensional modeling routine is developed. The model combines heat conduction and mass balance equations employing an appropriate cure kinetics equation. The required material data for the numerical simulation is obtained experimentally for a brake block available commercially. The effect of processing parameters and material properties on cure is studied by performing numerical simulations for different molding conditions and materials with different thermophysical properties. The effect of the heat of reaction on the thermal events of cure is also investigated using the numerical simulation in absence and in presence of that parameter, and assuming different values. For a rubber-based friction material, temperature distribution and molding time are not influenced by the heat of reaction released during cure. Moreover, the results indicate that the thermophysical properties of the brake blocks are much more effective than molding conditions in reducing the cycle time. Since the thermophysical properties are governed by the ingredients of the friction material, these properties can be improved in the formulation designing stage by including the appropriate ingredients. The results obtained by numerical simulation can be helpful to the designer of the compound, in order to achieve a brake block with both good braking performance and suitable processing properties.
Influence of a ‘Rotating Tip’ on the Properties of Tubing Made Using a Cross-Head Tubing Die
Authors: Gupta A. , Hsu T.-C. , Harrison I. R.
Published: December 2013

A novel ‘Rotating Tip’ die has been designed and built that offers the tubing processor the ability to produce a wide variety of tubing ID's and OD's from a single fixed geometry die. Furthermore the device permits, amongst its many other advantages, the production of variable ID tapered tubing, increased hoop stress tubing and ease in production of microbore tubing.
Drawing of β-Crystal Nucleator-Added PP
Authors: Fujiyama M.
Published: December 2013

Extruded sheets were prepared from homo-isotactic poly-propylenes (PP) with 0 to 10 ppm of quinacridonequinone which is a β-crystal nucleator for PP and the characteristics of drawing behavior and properties of drawn sheets were studied. The sheet without the nucleator consisted of usual α-crystals (hereinafter called α-PP), whereas the sheets with the nucleator contained much β-crystals (hereinafter called β-PP), whose content slightly increased with increasing nucleator content. While the tensile yield stress of the β-PP is lower than that of the α-PP, the drawing stress of the former is higher than that of the latter at the higher strain region after yielding. Even after drawn, the β-crystals remain in the α-crystals with low crystallinity at low drawing temperatures. However, the β-crystals and amorphous phase gradually decrease with increasing drawing temperature, and the α-crystals dominate above 80°C. The resultant tensile modulus and strength of the drawn sheets show maxima at drawing temperatures of 40 to 80°C on a balance between the effects of crystallinity and molecular orientation. The tensile modulus and strength of drawn sheet prepared from the β-PP are higher than those prepared from the α-PP by about 10% at those temperatures. The tensile elongation of drawn sheet prepared from the β-PP is slightly higher than that prepared from the α-PP at low drawing temperatures due to the remained β-crystals.
Crosslinking Modification of UHMWPE Fibers by Ultra-violet Irradiation
Authors: Yu J. R. , Chen Z. L. , Zhu J. , Liu Z. F , Wang Q. R.
Published: December 2013

By means of ultra-violet (UV) irradiation with photoinitiator and multifunctional crosslinking agent, the crosslinking modification of ultrahigh molecular weight polyethylene (UHMWPE) fibers prepared by gel spinning was performed. Thermal and mechanical properties of fiber samples were examined using differential scanning calorimeter, thermo-mechanical analysis apparatus and tensile tester, the gel content of fibers was measured by a standard device, the fiber surface was examined by scanning electron microscope. The results indicate that the optimal irradiation time is 1 to 2 hours. The modified fiber can then preserve its original mechanical properties, or may have better behavior, meanwhile, such fibers have improved heat- and creep-resistant behaviors.
Characterization of the Behavior and Blending Performance of a Continuous Mixer
Authors: Galle F. N. , White J. L.
Published: December 2013

An experimental study is presented of the residence time distribution, the melting/fusion process, power consumption, melt temperature and blending in a Kobe Steel Nex-T continuous mixer. Attention is given both to phenomena occurring in the mixing chamber and the associated bottom extruder. The variables considered include throughput rate, rotor speed, exit orifice position and mixing chamber temperature.
Stability of a Blown Film Extrusion Process
Authors: Yoon K.-S. , Park C.-W.
Published: December 2013

The stability of a blown film extrusion process has been investigated using a simple isothermal Newtonian model. Although the Newtonian model may be an oversimplification for polymer melts, it serves as a reasonable first approximation for linear polymers (e.g., linear low density polyethylene) in extensional flow situations. The results obtained by the method of linear stability analysis indicate that the blown film process becomes unstable if the blow-up ratio (BUR) or the film thickness reduction is larger than a certain critical value. In addition, existence of an optimum freeze-line-height is predicted at which the region of stable operation is largest in terms of the BUR and the film thickness reduction. These predicted trends are in qualitative agreement with experimental observations for linear polymers such as LLDPE.
Bulk Polymerization of ∊-Caprolactone in Twin Screw Extruder
Authors: Gimenez J. , Boudris M. , Cassagnau P. , Michel A.
Published: December 2013

The ∊-caprolactone bulk polymerisation, initiated by tetra-propoxy titanium, was investigated in a co-rotating twin screw extruder. On the basis of pressure measurements, the process dynamic modelling was achieved. The pressure drop at the exit die of the extruder was correlated to the rheological behaviour of the melt polycaprolactone owing to equations which characterise the flow inside the die. The residence time distribution modelling was determined with an in-line Ultra-Violet fluorescence method. Thus, the combination of both modellings leads to the process dynamic modelling. This work constitutes the basis for an approach of the process regulation by the way of an internal model control. Simulation has given good results. However, the large response time to the control, relative to the process dynamic, constitutes effectiveness limiting factor for experimental control of the process.
Analysis of Flow and Heat Transfer in Liquid Composite Molding
Authors: Yu B. , Chiu H.-T. , Ding Z. , Lee L. J.
Published: December 2013

An analysis of flow and heat transfer in Liquid Composite Molding (LCM) is presented. Analytical solutions for the velocity profiles including the boundary effects and temperature distributions are derived for constant viscosity fluids. The heat transfer during mold filling is also analyzed numerically. It is found that the boundary effect has a significant influence on heat transfer when the Reynolds number, Res, is greater than 1. When the Reynolds number is less than 1, the boundary effect on heat transfer can be negligible and Darcy's law is applicable. The results also show that the inertia effect can be neglected during mold filling in LCM. Experiments on heat transfer with a non-reactive fluid lead to measurements of the dispersion effect and test of the boundary effect on heat transfer. Several non-isothermal mold filling and curing experiments on two rather different reactive systems lead to an assessment of the factors a model must include to capture the curing behavior.
Solidification Criterion on Shrinkage Predictions for Semi-crystalline Injection Moulded Samples
Authors: Pontes A. J. , Pantani R. , Titomanlio G. , Pouzada A. S.
Published: December 2013

The phenomenon of shrinkage in injection moulding is particularly evident in semi-crystalline polymers. During cooling, these materials experience a transition from a completely amorphous to a partially crystalline status, which results in a severe change of all material characteristics, including volumetric parameters. In this study an iPP was injection moulded in a rectangular impression (120 mm × 30 mm × 2 mm) with a 1.5 mm thick line gate. The influence of holding pressure and time, and geometry constraints on linear shrinkage was explored. In-mould shrinkage was measured by means of a recent method based on strain gauges. Experimental results are compared with predictions for shrinkage obtained by C-Mold and a code developed at the University of Salerno, which takes into account crystallisation kinetics. The solidification criterion resulted to be extremely relevant for shrinkage predictions.
Flow Analysis of Injection-Press Molding Process
Authors: Tsutsubuchi M. , Kitayama T. , Togawa Y. , Nishio T. , Kutschera H.
Published: December 2013

We developed a method to determine the characteristics of a press machine required for the injection-press molding process. In this paper, a model based on a serial spring connecting two different springs was used. One was spring represented apparent machine rigidity and the other the resistance to compression of the resin. Using this model, we calculated the flow between parallel plates and flow behavior in a “tray” mold.
Properties of Injection Molded In Situ Composites Based on PPS and a Melt Processable Glass
Authors: Young R. T. , Baird D. G.
Published: December 2013

This work was concerned with evaluating the properties of injection molded composites consisting of polyphenylene sulfide (PPS) reinforced with various loadings of a melt processable phosphate glass. During injection molding, both the PPS and melt processable glass were deformable, facilitating the processing of higher glass loadings than are possible in conventional solid glass fiber reinforced materials. The stiffness of the composite blends was found to increase with glass concentration with a composite containing 60 wt% (44 vol%) phosphate glass showing moduli over 4 times greater than that of the neat PPS. Composites possessing stiffness comparable to a conventional E-glass reinforced material (40 wt% fiber) could be produced utilizing higher phosphate glass loadings on the order of 60 wt%. While the addition of the phosphate glass led to significant enhancements in the stiffness of the composites, the strength of the blends of ten fell to values below that of the neat resin. Although the use of phosphate glass typically resulted in strengths 2–3 times lower than those found for the E-glass filled material, these composites offered several advantages including lower anisotropy in mechanical properties, lower viscosities, and smoother surfaces.
Injection Blow Molding Technology for Polyethylene Terephthalate
Authors: Bubeck R.A. , Barger M.A.
Published: December 2013

A review of patents and the literature addressing the in ection blow molding (IBM) technology specific to PET bottles and containers is presented. Fabrication and polymer modification issues were cited. It was found that there is no model that includes all factors which enables a complete a priori prediction of in ection blow molded PET container performance, but there are several which cover certain aspects of the preform blowing step. Hot fill capability for PET is currently managed by both the control of crystallinity and container design considerations (i.e., wall profile, ribs, etc.). Depending on the desired result, both processing routes to enhance the level of crystallinity (generically referred to in the industry as heat set technology), and molecular modification to disrupt crystallinity have been patented, some quite recently. A number of patents address technologies that can be used to modify melt elasticity for blow molding. The modification of PET with PEN presents some new challenges due to transesterification during processing and fabrication. Biaxial stretch ratios of 18 are usually required for the blow molding of PET/PEN blends, and maximum filling temperature noticeably decreases only one day after fabrication.
Polymer Processing Technology in the 21st Century from the Viewpoint of the Japanese Plastics Industry
Authors: Sakai T.
Published: December 2013

Recent progress in polymerization easily allows the control of precise structure of a base polymer and accelerates lower-cost production using larger-scale-plants. In addition to this, today's more important issue in our industry is the development of the key-technology corresponding to a sustainable society. Under these circumstances, the polymer industry in Japan has been focussing on down-stream products from upper-stream using advanced processing technology. To meet today's trends, the polymer industry should establish more sophisticated technology in both higher functionality and hybridization to survive in the 21st century. In particular, various hybridized polymer-processing systems such as the combination of reactive extrusion and injection molding should be applied to create cost-effectiveness and less environmental burdens as well as higher performance.
Prediction of Screw Length Required for Polymer Melting and Melting Characteristics
Authors: Liu T. , Wong A.C.-Y. , Zhu F.
Published: December 2013

The previous study on the dynamic processing characteristics of co-rotating twin-screw extruder based on a visible technique (which employed a “transparent” extruder) performed by the authors Wong et al. [1 and 2] had enabled a quantitative treatment to be carried out in the present paper on the melting behaviour of polymer during an extrusion process. The qualitative analysis performed previously [1] had led to the development of a melting model which was capable of revealing some of the fundamental melting behaviour. The model also enabled the determination of the length of screw required for completing melting (Zr). Melting characteristics in terms of effects of solid feeding rate, temperature, screw speed and channel depth on the predicted Zr were discussed to further our understanding on melting performance of polymer melt in intermeshing corotating twin-screw extruder.
A Dynamic Model for Multiple Steady States in Reactive Extrusion
Authors: Janssen L. P. B. M. , Rozendal P. F. , Hoogstraten H. W. , Cioffi M.
Published: December 2013

The existence of multiple stationary values of the fully filled length in reactive extrusion is studied on the basis of a mathematical model describing dynamic extruder behavior. The extruder is modelled as a plug flow type of reactor. Through the introduction of travel time for a fluid element in the extruder, time dependent viscosity models following from rheokinetics can be used. Special attention is paid to ionic and radical polymerization reactions. Hysteresis behavior for stationary values of the fully filled length exists when die resistance and rotational speed are varied. The effects of reaction rate, viscosity levels and degree-of-fill on stable operation at high conversions are studied. The mathematical dynamic model presented here can account for some of the experimentally observed dynamic phenomena in the reactive extrusion of radical polymers.
Bulk Polymerization of ε-Caprolactone in an Internal Mixer and in a Twin Screw Extruder
Authors: Kim B. J. , White J. L.
Published: December 2013

Bulk polymerization of ε-caprolactone has been carried out both in a laboratory internal mixer (Brabender Plasticorder) and in a modular intermeshing co-rotating twin screw extruder. Various initiators, such as titanium n-butoxide, aluminum triisopropoxide, and sodium hydride were used to polymerize ε-caprolactone in an internal mixer. The continuous polymerization of ε-caprolactone was performed using aluminum triisopropoxide under a range of processing conditions, including barrel temperature profiles, throughput, and screw speed. This polymerization was investigated for various ratios of monomer to initiator. GPC analysis demonstrated that significant quantities of oligomers were produced together with high molecular weight polymer at different reaction temperatures. H NMR detected the hydroxylation of growing chain end group for bulk polymerization at high barrel temperature. The molecular weight was reduced along the screw axis once the maximum molecular weight was obtained after the first kneading disk block. Increasing screw speed caused further reductions in molecular weight.
Use of the Fast-cool pVT Data for Shrinkage Analysis in Injection Molding
Authors: Han S. , Wang K. K.
Published: December 2013

The prediction of shrinkage and warpage of crystalline polymers is quite difficult. This is because of the complications of the crystallization process and associated material property changes. Particularly, the pVT behavior is dependent on the cooling rate during injection molding. Traditionally, the pVT data were measured in a device where the cooling rate is very slow compared to that in the actual injection molding process. This cooling-rate dependent pVT data is considered to affect the shrinkage and warpage calculation significantly. In the present study, a method has been developed to obtain pVT behavior at the same cooling rate as in the actual injection molding process. Obtaining other material data such as viscosity, thermal conductivity and heat capacity at the cooling rate of the actual injection molding process has also been considered.

Injection-molding experiments have been conducted to measure the shrinkage of a part using semi-crystalline polymers. The polymers used in this study are polyamide 66 (PA 66) and polybutylene terephthalate (PBT).

Simulation has been done to calculate the shrinkage using the cooling-rate dependent material properties. Using the fast-cool pVT behavior, the agreement between the simulation and the experiment improved significantly compared to the traditional approach.
In-line Ultrasonic Monitoring of Filler Dispersion during Extrusion
Authors: Tatibouët J. , Huneault M. A.
Published: December 2013

Mechanical and rheological properties of filled polymers are very sensitive to the filler dispersion. Classical methods for evaluating dispersion are based on optical or scanning electron microscopy observations on extruded specimens. They cannot be used in-line and are generally time consuming. We present here an in-line characterisation technique to evaluate the dispersion of calcium carbonate, CaCO3, in polypropylene. The technique is based on the monitoring of velocity and attenuation of ultrasounds in the flowing material. These properties are measured in a specially instrumented die placed at the end of a single screw extruder. Measurements were made for filler concentrations up to 60 wt.%. In-line data are compared to dispersion indexes measured by an optical method on 25 micron thick films.