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Inner parts properties strongly affect the global mechanical behavior of molded semi-crystalline parts. During the last years an IKV research group tried to bridge the gap between simulation of inner properties and structural analysis. By a self-developed software to simulate inner properties arising during injection molding and programmed subroutines for Abaqus a so-called integrative simulation was realized. Results of this simulation chain will be presented and discussed focusing on a plastics pipe fitting made out of polypropylene.
Shelf life is an important quality for medical components. It is uncertain at what point physical aging affects the chemical resistance of medical components. The breakdown of chemical resistance in the polymer can result in adverse effects in the field.As a polymer ages there is usually a reduction in molecular weight, which can lead to greater susceptibility to chemical attack. The objective of this research is to attempt to draw correlations between accelerated aging at elevated temperatures and room temperature aging to better identify when molecular weight reduction and increases susceptibility to chemical attack occurs.
This paper will show how the microcellular injection molding process compares to conventional injection molding for an injection molded part with tight tolerances. A critical part from a laser printer was used as an example in the study. The part was first injection molded using the conventional injection molding process then analyzed using the microcellular injection molding process. The Moldflow® injection molding simulation software was able to accurately predict the part warpage which agreed well with the real injection molded part. The predicted part warpage in microcellular injection molding process was better than in the conventional injection molding process.
Besides a lot of positive aspects of foam injection molding (FIM), the achievable surface qualities are rather poor in many cases. Occurring silver streaks, melt eruptions and cold-displaced polymer melt areas cause more uneven and non-uniform part surfaces in comparison to conventional injection molding. That is the reason why foamed parts are often excluded as visually exposed parts. A comprehensive understanding of the effects arising during the filling phase establishes new possibilities to increase the surface qualities in foam injection molding. New research shows that different process variants of FIM such as breathing" molds gas-counterpressure structured and coated cavity surfaces can increase the surface quality effectively."
The structure-rheology relationship is investigated in three polyethylenes namely high density polyethylene (HDPE), a metallocene linear low density polyethylene with no chain branching (mLLDPE) and a metallocene polyethylene containing long chain branching (mLLDPE-LCB). Shear and extensional rheology measurements were carried out in the linear viscoelastic regime and correlated to the molecular weight, molecular weight distribution and long chain branching. Shear rheology showed that HDPE exhibits a viscosity profile whereby the Newtonian behavior is not completely attained as shown by the slope of the storage modulus in the terminal region. mLLDPE was found to possess the longest and well-defined Newtonian region and the highest transition to the non-Newtonian region. In the presence of long chain branching (LCB), the terminal region is not apparent while the onset of shear thinning is decreased. Such behavior can be related to the effects of MWD and LCB and was corroborated using extensional viscosity measurements, which showed slight deviation from the LVE envelope for broader molecular weight distribution and strain hardening in the presence of long chain branching.
The ionic conductivity of linear segmented thermoplastic polyurethane (TPU) in-situ reacted with alkali metal salts as well as their blends of TPU and modified polysiloxane is investigated. The relationship between ion conductivity and cationic size in TPU electrolytes is discussed with different salts. We focused on investigating two particular types of salts such as LiClO4 and KI. Differential scanning calorimeter (DSC) and Fourier transform infra-red (FTIR) spectroscopy was used to determine the interaction of salts with TPU. The temperature dependency of TPU electrolytes is also studied by using the modified LCR meter.
The water injector is the centerpiece of the complete system configuration for the water injection technique. For a stable and reproducible process cycle, a well operating injector system is one of the basic demands. It is still unclear how the injector design effects the stability of the process and important part properties. Thus, different injector concepts have been developed and evaluated practically with different polymers. The first results presented in this paper suggest, that the injector orifice diameter and the ambient shape of the injector closure cap influence directly the part quality and the process stability.
A simple model was developed for the steady state phase of the vibration welding process using the lubrication approximation. The model predicts temperature and pressure at the interface, molten fluid film thickness, shear stress and shear rate as functions of weld pressure, amplitude, frequency, and penetration velocity. The melt viscosity was estimated, using the penetration velocity obtained from meltdown velocity, since data for melt viscosity of polyamide-6 at vibration molding conditions were not available. The model predicts temperature at the interface in a reasonable range, 7-37°C above the melting peak temperature. The overall predictions of the model are reasonable and they should be helpful in optimization of vibration welding process parameters.
An unconventional embossing method is evaluated in which de-embossing is avoided to prevent the deformation or damage of the polymer microstructure on the substrate due to one or more of the following issues involved in hot embossing process: higher feature density, higher aspect ratio, bad surface quality and under-cuts. In this study, a PDMS mold is used to transfer a SU-8 structure to a water-soluble polymeric stamp under low pressure and low temperature, which is used as the rigid tool in the following hot embossing and can be reused by being dissolved in water, an environmentally benign solvent. This method has potential uses in the replication of high aspect ratio microstructure on polymeric materials that cannot be easily achieved using other methods.
Carbon-filled epoxy composites were developed as potential materials of bipolar plates in proton exchange membrane fuel cells (PEMFCs). The synergistic effect of combining graphite and carbon black on conductivity of composites was investigated. All composites provided much higher in-plane electrical conductivity than the Department of Energy (DOE) target value of 100 S/cm, although through-plane conductivity was measured to be about 50 S/cm. The chemical stability of these materials was checked by using acid reflux in boiling aqueous sulfuric acid solution with a pH of 2. The thermal properties of these composites was investigated through DSC and TGA.
Polystyrene nanocomposites were obtained via melt compounding, using montmorillonite modified with various surfactants. The interlayer distance, thermal stability and surface tension of the resulting organoclays were determined. Moreover, the resulting PS nanocomposites were evaluated using X-ray diffraction and thermogravimetric analysis (TGA). The mechanical and barrier properties were also determined. The results show significant differences in thermal stability, and mechanical and barrier properties of the nanocomposites depending on the composition and interfacial properties of the surfactant.
We have prepared several types of recycled materials from waste poly-(ethylene terephthalate) (PET) through different compounding conditions. As a result, modified recycled- PET (R-PET) with strength similar to virgin PET has been successfully developed. In this paper, structure and mechanical properties of the modified R-PET immersed in hot water were investigated on the basis of tensile test, impact test, Gel Permeation Chromatography (GPC), and Differential Scanning Calorimetry (DSC).
A series of poly (ethylene co-vinyl alcohol) (EVOH) / montmorillonite layered silicate (MLS) nanocomposites were processed using a mini-extruder and evaluated by xray diffraction, transmission electron microscopy (TEM) and thermal analysis to determine the polymer/MLS interactions and morphologies. The nanocomposite materials were produced using different concentrations of MLS (3, 10 and 15% by weight) and EVOH that were equilibrated to 95% humidity and to dry conditions prior to processing. Most samples displayed an intercalated morphology with no significant changes with the presence of moisture.
Thermal stability and mechanical properties of polymeric nanocomposites consisting of functionalized silica nano-particles (average diameter 75nm) embedded in polymethyl methacrylate (PMMA), with and without surface grafting of PMMA, were studied. Results from differential scanning calorimetry show an increase of Tg upon the introduction of the nano-particles, however, only to a limited extent. Similar results were observed in dynamic mechanic thermal analysis. The storage modulus also showed a slight increase less than 5%. Samples with PMMA grafted particles synthesized via in-situ polymerization in supercritical CO2 did not show an anticipated drastic improvement. This may result from the plasticizing effect of the stabilizer used the dispersion polymerization.
In this study the effect of acrylic-based components, including process aids (PPA), on the rheological properties of rigid PVC formulation is investigated. A statistically designed experiment was set up to cover the effect of composition on the melt viscosity and the melt strength of the compound as a function of temperature. The effect of the acrylic components was studied in relation to the rheological properties such as capillary rheometry and melt strength. In the absence of an acrylic process aid, the PVC compound showed a loss of adhesion at the wall caused by a change in the microstructure and characterized by pressure oscillations and a dip in the melt strength trace. As the temperature is increased, the slippage appears to be minimized and the head pressure stabilized.
Ordered block copolymer materials contain randomly oriented grains with concomitant defects and grain boundaries. Effect of these grain boundaries on mechanical behavior of these materials is not well studied so far. This work investigates different Styrenic block copolymer compositions having spherical, cylindrical and lamellar morphologies. It was observed that by carefully compounding these styrenic block copolymers having different morphologies, it is possible to completely disrupt the local scale order and remove the grain boundaries present in these materials. Evaluation of these mixed systems was done with Small angle x-ray scattering and Transmission electron microscopy. Further, mechanical behavior of these mixed systems was studied.
The preparation of nanoclay-reinforced poly(lactic acid) (PLA) nanocomposites by means of melt processing has been investigated. In order to optimize the dispersion of the nanoclays and the nanoclay-matrix interface, strong interaction between the nanoclay and the polymer matrix is required, preferably at the atomic level. Different chemistries of the organo-nanoclay have been carefully considered in order to optimize the chemical interaction between the organic and inorganic phases during processing. Various processing conditions have been examined with the aim of minimizing the degradation and oxidation of the materials, both the matrix and the organo-nanoclay, while at the same time maximizing clay dispersion and the interaction between the polymer matrix and the clay. X-ray diffraction, field emission gun scanning electron microscopy (FEGSEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were used to characterize the dispersion of the nanoclay, the crystalline structure and the mechanical behavior of the PLA nanocomposites, respectively. The relationship between formulation, structure, and performance is discussed.
Different grades of Polypropylene copolymers being used for automotive interior applications have been evaluated for weldability of the vibration welding process. Vibration Amplitude (VA) and Melting Down Distance (MDD) are key process parameters of the vibration welding process and design consideration, while talc content, density, and melt flow rates are essential to influence material properties. Understanding of effects of both vibration amplitude and MDD will greatly help to optimize product design and increase manufacturing flexibility.DOE procedures to evaluate material weldability for the vibration welding process have been suggested by Park. In the same paper, how to define weldability for the material has been suggested. For more conclusive evaluation, both welding strength and failure modes of the welded plaques need to be investigated. Effects of the vibration amplitude and MDD on those key material properties have been studied by evaluating welding strength, elongation, and failure modes of welded plaques. Optimal vibration amplitudes associated with optimized melting down distances for all resins evaluated are provided in this paper.
This paper provides technical detail of key technologies selected as finalists during the 2005 Automotive Innovation Awards Ceremony. Process related innovations such as headliner with self reinforcing sunroof opening, partial mold behind integrated trim panel, fascia appliqué, thick sheet Paintless class A thermoformed rocker pane, bonded metal/plastic hybrid front end carrier and Material related innovations such are Cross linked expanded PE soft foam for seat halo, PP/PS/Nano composites for interior applications, New PC-silicon copolymers, and reactor TPO MIC for airbag will be discussed first. Exterior Applications such as Panorama Roof Module, class “A” carbon fiber reinforced epoxy fenders, all plastics glass run channel and composite in-bed trunk are described followed by Interior applications such as integrally molded airbag door, HVAC film valve, PUR cast skin, seamless passenger airbag lid are discussed in detail.
We’ve aimed to develop high impact strength materials from waste PET. Recycled PET with impact strength as high as polycarbonate (PC) was successfully developed by reactive compounding with polymer with epoxy group. Structure development of the recycled PET in the reactive compounding was discussed on the basis of fracture surface observation by scanning electron microscope (SEM), Dynamic Mechanical Analyzer (DMA) analysis, Gel Permeation Chromatography (GPC), and Differential Scanning Calorimetry (DSC).
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