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In extrusion processes, melting strongly influences the development of product end-use properties such as tensile strength. For effective monitoring and control of these properties, it is essential to describe the melting process quantitatively. Obtaining a high-fidelity quantitative description of the melting process, however, remains a challenging problem. This paper proposes and employs an empirical modeling approach (similar to the identification" of dynamic systems from input/output data) to model the melting process. The recently developed "pulse perturbation technique" is used to generate the input/output data. Each parameter of the identified model can be associated with a distinct melting mechanism thus providing valuable quantitative insights into the melting process. Based on the melting data presented in  the model is used to analyze the effect of extruder operating conditions on the melting of semi-crystalline amorphous and rubbery polymers."
Conventional analysis such as MOLDFLOW divides the injection molding process into two different stages: filling and cooling. Filling analysis assumes both the cavity and core temperatures keeping constants during filling stage, while cooling analysis assumes the part temperatures in anywhere being constants. In this study, the temperatures between mold and part are assumed unknown and determined by solving both polymer and mold thermal problems. After ejection, the mold temperatures, inheriting from the last cycle, are memorized and used as the initial values for next cycle simulation. To keep the geometrical information consistency, both the part and mold are represented by solid models. The dual domains and conventional Galerkin methods are employed to solve the filling and cooling problems respectively. The coupled method can simulate the transient and more complicate thermal problems.
Three dimensional parts comprised of polyolefins such as polypropylene have low levels of polar functional groups on the surface and have poor wettability and adhesion properties, making it difficult to apply other functional layers such as dyes, inks, adhesives and coatings. To enhance surface polarity, surface treatments such as flame, corona or plasma can be applied to improve wettability and adhesion. Plasma can specifically be used as a preparatory treatment for the photografting approach recommended in this paper to achieve high stability in treatment and permanent changes to the surface.
In this work the weldability of bio-renewable nanocomposites was studied. Soybean proteins were denatured in a glycerin solvent and plasticized with a screw extruder. The glycerin contained clay platelets that were exfoliated with high power ultarsonics (2.2 kW @ 20 kHz). Various levels of exposure to the ultrasonic energy were used to exfoliate the clay platelets resulting in nanocomposites with various levels of exfoliation. It was also seen that these materials were not effectively welded with hot plate welding; however, success was found with vibration welding where significant material pullout was seen at the faying surfaces after tensile testing.
This paper reviews the use of diffractive optics for beam shaping of high-power lasers (100 W) for micro-welding of plastics. By using Fourier transformations on twodimensional complex arrays, spatial domain images were transformed into phase domain images. These images were then used to produce a mask for the microlithography etching of a glass diffractive optical element (DE). An 80 W fiber laser with a wavelength of 1084 nm was coupled in air to the lens to shape the beam into predetermined patterns. These patterns were then reduced with standard optics to a desired size. The images were focused at the faying surface of two plastic components in a through-transmission weld configuration. Weld quality was assessed based on fidelity, burst pressure and consistency. The resulting welds were able to support burst pressures as high as 0.6 MPa. In addition weld features as small as 300 ?m were also produced.
This paper reviews work done to determine weld strength as a function of temperature history fields at the faying surfaces of welds. In order to simplify the resulting models, isothermal conditions were assumed by welding relatively thin films with impulse welding. Furthermore, the weld geometry was clearly defined by accurate placement of an overlap weld geometry. It was found that healing of the weld can be better defined as a function of time and temperature instead of temperature alone, as historically done. By combining squeeze flow of asperity peaks and reptilian diffusion models into one model, it was shown that by using an Arrhenius Equation as a function of temperature and time one can accurately predict weld strength and degree of healing.
This paper reviews a coupled temperature, molecular diffusion and squeeze flow model that was used to predict the quality and size of micro-welds in plastics. Weld size and quality predictions that were based on previously presented standard heat source models models and temperature fields, were compared to experimental results. In this case, microwelds as small as 11 ?m in width were produced with through transmission infrared welding. It was found that the predictions were in very good agreement with the experimental results. The model was able to predict weld size without the need for defining a temperature range as previously reported. This model was then further developed to predict the theoretical limit of weld size based on heat source spatial relationship. It is predicted that sub-micron welds are achievable.
Poly(ethylene succinate), poly(trimethylene succinate) and a series of poly(ES-co-TS)s were synthesized through a direct polycondensation process. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. Their thermal properties were characterized using differential scanning calorimeter. The compositions and the sequence distributions of the copolyesters were determined by analyses of 1H-NMR and 13C-NMR spectra. The sequence distributions of ES and TS units were found to be random. X-ray diffractograms were obtained for polyesters crystallized isothermally.
Although the family-mold has an advantage to reduce the cost, molding defects frequently occur by an excessive packing the smaller-volume cavity, especially when the two cavities have a large volumetric difference. In this study, we developed a variable-runner system for the filling balance of the cavities by changing the crosssectional area of a runner. We applied the variable-runner system to the cavities having filling imbalance, and achieved a fair filling balance. The filling balance was checked with the temperature and pressure sensors in the cavity. We also examined the influence of the injection speed to the balancing capability of the variable-runner system.
As in many other technologies, the cost effective production of polymer-bonded magnets is an important factor. The volumetric ratio of sprue volume to part volume is very high due to the integration of e.g. coils for the induction of the magnetic field inside the mold. Therefore, the injection molding process of polymer-bonded magnets produces a lot of scrap material. This material has to be reprocessed to reduce the production costs of polymer-bonded magnets because the hard-magnetic fillers are very expensive. The effects of multiple reprocessing on the magnets properties are scientifically investigated.
Production and processing of plastics has always been a very promising industry and research field. However, for further success in this field strong educational background is necessary. Croatia signed in 2001 the Bologna declaration and in 2005 the first generation of students started their education according to the Bologna process. The implementation of the Bologna declaration has caused a lot of changes in the educational process in the fields of plastics. This paper will present the situation and the possibilities for students in the fields of plastics at four Croatian Universities (in: Zagreb (the biggest one), Osijek, Rijeka and Split) and also, research works and specific fields of interest in the Croatian educational and research institutions and the possibilities that are offered to industry experts in this area.
Business world is exposed to accelerated, revolutionary changes, driven by results of scientific research and fast technical progress, globalization process, the growing use of the Internet and the development of ebusiness. Companies are trying to adjust to these changes and at the same time they are fighting against rising costs and competition. The situation is much worse for companies from the so-called countries in transition, like Croatia. They went through a very painful process of changing the ownership, losing their markets and jobs and through process of reorganization on every level and at the same time trying to adjust their way of work to the challenges of the modern world. The situation in the Croatian plastics and rubber industry will be presented, its way of adjusting to the changing business conditions and the main organizational and managerial changes that occurred in the Croatian plastics and rubber companies during the process of transition.
In this paper, we introduce a new type of small scale compounder. The compounder developed is for mixing of polymeric samples of 0.5 ~ 10 g. It consists of a heated cylindrical metal having two cylindrical cavities connected through a narrow channel and two cylindrical pistons, which squeeze molten polymers from one cavity to the other cavity through the narrow channel. During mixing procedure, the molten polymers flow from one cavity to the other cavity, repeatedly, and this operation generates the extensional flow in the converging and the diverging geometry. Because the compounder has mixing chamber of very simple geometry, the cleaning is very easy and the material lost is very small. We evaluated the mixing efficiency of the compounder by comparing with the commercialized small scale-mixers including a cup and rotor batch mixer, an internal batch mixer and a recirculating conical twin screw extruder. It was found that the compounder developed has many advantages over the existing small scale mixers.
Conducting polymer blends of polyaniline nanorods (PANI-NR) and cyanoresin were prepared by in situ polymerization. PANI-NR was synthesized by using the template free method and PANI-NR / cyanoresin blends were prepared by the addition of cyanoresin / dimethylformamide (DMF) solutions to PANI-NR / DMF solutions. Its morphological state has been confirmed. The diameter and length of PANI-NR obtained was approximately 120 ~200 nm and 600 ~ 1200 nm, respectively, and the conductivity of PANINR/ cyanoresin blends was 10-3~10-1 S/cm. The thermal stability of PANI-NR/cyanoresin blends was improved with increasing cyanoresin contents. The effect of dopant types and their blend compositions on the morphology and conductivity of PANI-NR/cyanoresin blends were investigated.
The use of nano-particulates in plastic materials has become a potential alternative due to its versatility on property modification and the ease of batch fabrication. This paper investigates the kneading and mechanical properties of polypropylene added with nano-ZnO powder in sizes of, 10 to 30 nm, through batch kneading and microinjection molding steps. The results showed that the 1wt% ZnO made microgears with a 1.5 mm outer diameter were well duplicated with clear structural definition. The standard deviation in dimension was far less than the designed deviation of 20 ?m. The resulting composites exhibited significant improvement in wear resistance of 50% and mechanical strength of 40% with a small amount of nanofillers, 1wt% and 5wt%, respectively.
Thermoforming consistent parts depend on knowing and controlling several material and process variables, the most important being the quality of the sheet feed stock. The extruded sheet of the same material could vary in terms of polymeric contamination, thickness, thermal stresses, and amount of regrind, volatiles, color, gloss and grain. Mold material and mold temperature could also vary. Many times, effects of such variations manifest during actual thermoforming in form of tearing, wall thinning, shape distortion, fading, pinholes, and grain distortion. We illustrate use of novel equipment for rapid detection of such variables and their effects on thermoformability, sparring need for expensive plant time and material waste.
This paper proposes the solutions predicting the coefficient of the thermal expansion changes of composites which include the sphere, the fiber-like shaped and the disk-like shaped inclusions like two dimensional geometries, which has one aspect ratios, ?? = a1/a3. The analysis follows the procedure developed for elastic moduli by using the generalized approach of Eshelby’s equivalent tensor. This model should be limited to analyze the composites with unidirectionally aligned inclusions and with complete binding to each other of both matrix and inclusions having homogeneous properties.As the results, the coefficients of transverse thermal expansion of composites are predicted to increase more than the thermal expansion of polymer matrix for both disc- and fiber-like shape inclusions.
Polymer nanocomposites based on poly(ethylene 2,6-naphthalate) (PEN) and multiwall carbon nanotube (MWCNT) were prepared by a melt blending process in a twin-screw extruder. The incorporation of MWCNT accelerated the mechanism of nucleation and crystal growth of PEN, this effect being more pronounced at lower MWCNT content. The non-terminal behavior of PEN/MWCNT nanocomposites was related to the dominant nanotube-nanotube interactions at higher MWCNT content, leading to the formation of interconnected structures of MWCNT in the polymer nanocomposites. The incorporation of a very small quantity of MWCNT significantly improved the mechanical properties of PEN/MWCNT nanocomposites.
Laser transmission welding is a technique that uses laser-absorbent and laser-transparent thermoplastics. The energy loss in the transparent part and the depth of laser penetration in the absorbing part depend on the laser absorption coefficient (LAC). This paper presents a novel LAC measurement method for use on absorbing parts. A defocus strategy was used to attenuate the power of the laser beam which was then passed through thin specimens prepared using a microtome. LAC of polycarbonate was measured for carbon black content from 0.0125 to 0.1 wt.%. It was found to increase linearly with carbon black concentration.
Among key success factors for thermoplastic olefins in automotive applications, the cost/part and processability are most important. Today, much of TPO is processed via injection molding. The drive for lighter and hence the thinner wall parts requires compromise between processability and properties. In shaping large parts, thermoforming offers significant advantages over injection molding. However, conventional PP and impact modifiers used in TPOs lack necessary melt strength and/or melt elasticity for thermoforming deep and thick wall parts. Modification is therefore deemed necessary. This paper summarizes properties of a new type of TPO produced via reactive modification with balanced stiffness, impact and thermoformability.
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