SPE Library

In this work conductive nano composite has been prepared by incorporating multiwall carbon nanotubes (MWCNT) in polyvinylidene fluoride (PVDF) by melt blending method. The creep behavior of PVDF composite is studied by compression test. To study the time and stress dependent piezoresistive behavior of the prepared composite, mechanical testing was synchronized with electrical resistance measurement. Comparison of mechanical creep with the creepdependent resistance implied that there is a conducting percolation attributed to the physical contacts between MWCNT and a mechanical network formed by the molecular chains of the polymer matrix and the interaction between the filler and the matrix.

Research on biodegradable materials has been stimulated due to environmental and economic concerns. The blends of polycaprolactone and a starch based material were prepared by compounding with a twin-screw Brabender. DSC TGA and DMTA were used to characterize the blends and indicated some degree of interaction between the neat polymers. With respect to the neat PCL DSC results of the blends revealed peak shift and depression in either the melting or melt crystallization point and the glass transition temperatures obtained from the maxima loss tangent peaks of DMTA were also shifted. TGA studies showed decreased thermal stability of the PCL rich phase blends with increasing wt.% starch based material. Tensile test concluded improved modulus in the blends in comparison with the neat PCL. (Ref.9)

Bamboo fiber may withhold great potential as an alternative to wood, and bamboo can be a raw material to fabricate a composite material and its applicability is being widely investigated. Cellulose fibers can be aligned to the length of the bamboo providing maximum tensile and flexural strengths and rigidity. Increased research in the recent years has considerably contributed to the use of bamboo fibers as a reinforcing material for broader applications. However, it is difficult to obtain polymer/bamboo fiber composite having its excellent mechanical properties, because the bamboo fibers covered with lignin show lack of interfacial adhesion. Therefore, it is necessary to enhance the interfacial adhesion by extracting lignin without microstructure disruption and adding silane coupling agents. In this research the influence of silane coupling agent, composites with pristine bamboo fiber, delignified bamboo fiber, and delignified and silane treated bamboo fiber were newly prepared and investigated, respectively.

Nowadays various technologies are capable of producing hybrid plastics/metal-composites. However they all have disadvantages due to several manufacturing steps and limitations in the achievable complexity of the part geometry. An innovative approach to produce plastics/metal-composites is to combine the injection molding of plastics and the die casting of metals to a new hybrid multi-component process within a single mould and on a single machine. Combining the plastics injection molding and the die casting of low-melting metal alloys plastics parts with integrated electrically conductive tracks can be produced. A selection of promising results concerning this new process is presented.

Nowadays, various technologies are capable of producing hybrid plastics/metal-composites. However, they all have disadvantages due to several manufacturing steps and limitations in the achievable complexity of the part geometry. An innovative approach to produce plastics/metal-composites is to combine the injection molding of plastics and the die casting of metals to a new hybrid multi-component process within a single mould and on a single machine. Combining the plastics injection molding and the die casting of low-melting metal alloys, plastics parts with integrated electrically conductive tracks can be produced. A selection of promising results concerning this new process is presented.

Applications in the automotive, medical and electronics industries continue to drive improvements in polymer performance. Specifically, greater UV resistance, greater chemical resistance, higher service temperature, and processing stability are becoming more essential for consumer product components. Styrene-ethylenebutylene-styrene (SEBS) copolymer rubbers, SEBS/polypropylene blends, TPEs and polypropylenes are emerging as high performance materials integral to handles, grips, elastic components, oil gels for telecommunications, medical parts, automotive gaskets and hoses. TPEs in particular are being employed to replace plasticized low durometer PVC due to safety concerns as a component material for medical devices. The bond strengths of these polymers with specially formulated adhesives with and without atmospheric plasma surface modification were investigated. The results of bond strength improvement tests are presented.

Layered silicates used as nano filler are suitable for improving the mechanical properties of polymers. As an alternative to melt compounding an in-situ polymerisation process for the production of PA6-nanocompounds is investigated. During the in-situ process the layered silicates are dispersed in the monomer caprolactam leading to an intercalation process. The following anionic activated polymerisation process itself takes place in corotating twin screw extruder. The production of a polyamide compound containing 0 2 and 4 wt.-% nano-scaled silicates was successful. The in-situ produced compounds were injection moulded and their mechanical properties were analysed.

Layered silicates used as nano filler are suitable for improving the mechanical properties of polymers. As an alternative to melt compounding, an in-situ polymerisation process for the production of PA6-nanocompounds is investigated. During the in-situ process, the layered silicates are dispersed in the monomer caprolactam, leading to an intercalation process. The following anionic activated polymerisation process itself takes place in corotating twin screw extruder. The production of a polyamide compound containing 0, 2 and 4 wt.-% nano-scaled silicates was successful. The in-situ produced compounds were injection moulded and their mechanical properties were analysed.

Silicon solar cells lose 0.45% of power for every 1oC increase in temperature. If solar modules could dissipate heat more efficiently, the operating cell temperature would be lowered, increasing the module power output. In this paper, we present findings in using encapsulants with improved thermal conductivity to increase the heat transfer from solar cells into the environment. The outdoor performance of solar modules built with the improved encapsulant shows that 1-2% power gain can be achieved compared with the standard encapsulant. Further, modules with the improved encapsulant are anticipated to have better long-term reliability as compared with the standard encapsulant.

Biotechnology, information and medical industries have a high growth potential. A key technology for those industries is the replication of micro- and nanostructures. Precise micro- and nanostructured parts with functional surfaces can be produced economically by injection moulding. The whole process chain (thermal mould condition, moulding, demoulding) must be analysed carefully. To enable the precise production of such structures a new technique for variothermal injection moulding was developed at the IKV. An innovative laser heating unit was designed and built. The laser unit was implemented into an injection mould. Using this technique selective parts of the cavity could be heated with high temperature gradients of up to 300K/s. Preliminary measurements were done to correlate the laser power and the temperature change on the mould surface. A pyrometer and a laser control unit were implemented to realise a precise temperature profile on the mould surface without a temperature overshoot.

The effect of the degree of substitution (DS) of carboxymethylated starch (CMS) as green corrosion inhibitor of carbon steel on 200 mgL-1 NaCl solution was investigated. Physical/chemical structure of CMS was studied by Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (13C-NMR). DS of this bio-polymer was determined by back-titration. Its inhibitive properties were evaluated using polarization curves and electrochemical impedance spectroscopy. CMS acts as corrosion inhibitor and the protection level is highly dependent on the degree of substitution. The formation of a chelate between carboxylate groups and ferrous cations allows the inhibition mechanism of CMS to be explained.

Melt blowing is an extrusion process that produces nonwoven webs with fine fibers that are approximately 1 to 10 microns in diameter and find applications in filtration, sound and liquid absorbency and thermal insulation. We have introduced multiple layers within each microfiber and shown that novel web properties can be obtained. The number of layers within each micro fiber was varied from 2 to 27, although layers as high as a thousand can be achieved. We have shown that synergistic mechanical properties can be obtained in a controlled manner. The processing-structure-property behavior of multilayer melt blown webs will be discussed.

Processing undried polycondensates as PET or PA using a melt degassing single screw extruder is a real alternative to the conventional energy- time- and cost-consuming pre-drying process. Due to the industrial demand of processing recycled and low priced materials the moisture content or/and the resin mixture can substantially vary from batch to batch. This leads to a deviant molecular weight degradation and an unsteady final product quality. The paper presents an approach to compensate these variations in the feedstock in a closed-loop control. It is based on the direct influence of the degassing pressure on the moisture evaporation of the melt. The product quality is estimated online in the extrusion process e.g. via melt viscosity and is controlled by the degassing pressure in the extruder.

Processing undried polycondensates as PET or PA using a melt degassing single screw extruder is a real alternative to the conventional energy-, time- and cost-consuming pre-drying process. Due to the industrial demand of processing recycled and low priced materials, the moisture content or/and the resin mixture can substantially vary from batch to batch. This leads to a deviant molecular weight degradation and an unsteady final product quality. The paper presents an approach to compensate these variations in the feedstock in a closed-loop control. It is based on the direct influence of the degassing pressure on the moisture evaporation of the melt. The product quality is estimated online in the extrusion process, e.g. via melt viscosity, and is controlled by the degassing pressure in the extruder.

The overactive bladder syndrome (OAB) is defined as a symptom complex which is characterized with frequent urination, urinary incontinence and a strong, sudden urge to urinate even when the bladder is not full. About 10% of the total population have OAB and it occurs in every age group. Apart from the medical, oral therapy, the so called intravesical instillation is used as well. In order to minimise the numerous side effects of the oral therapy like dry mouth, dizziness or depressions a biodegradable, active agent carrying implant for the intravesical therapy of the OAB was aspired. After a project period of two years a biodegradable, active agent carrying polymer implant could be developed.

New non-fluoro process aid additives performance to improve flow properties of polycarbonate (PC) and polypropylene (PP) are discussed. The new formulations provide increased output and reduce torque during processing of the polymers by improving the flow properties while maintaining stability as indicated by measurement of melt flow index. It was found that in the case of their use in PC, the effect is achieved without causing hydrolysis of the polymer. The new additives are effective at very low addition levels (0.05%) and one of the formulations can be used for clear PC or FDA applications.

A new injection molding for metal powder green part was put forward in detail in this paper. Vibration force field generated by electromagnetic field in the whole process of plasticization, injection and packing, implementing dynamical plasticization metering, injection and packing was introduced. An in-depth experiment study on the effect of vibration force field on metal powder 316L/binder under steady and dynamic injection conditions was carried out with an experiment equipment and dynamic injection machine. Experimental results show that the filling pressure will be reduced when the vibration is introduced, the flow of melts becomes more uniform and the distribution of different components is also more uniform in the green parts during the dynamic injection molding. The mixing dispersion and distribution effect are better and the density is also larger than the green part's with traditional injection molding. The existing of vibration can effectively promote not only the microcosmic structure and also quality of metal powder green part.

In an ongoing search for ways to design lower cost, lighter weight, more durable products, appliance and subcomponent manufacturers are increasingly substituting plastic components for parts once made of metal or glass. By nature, plastics are highly corrosion resistant and require no surface treatment to withstand exposure to corrosive materials. Plastics can be easily formed into complex shapes, allowing designers to reduce the number of parts in an assembly; however, many times these components need to be connected in the final assembly. Whether bonding plastic to plastic or plastic to another material, adhesives offer several major benefits. Whereas mechanical fastening methods concentrate the stress in one spot, with adhesives, the load is spread over a wide area, reducing the amount of concentrated stress on the joint. Mechanical fasteners such as rivets, nuts, and bolts require holes to be drilled into the assembly, and frequently interfere with the aesthetic styling of the product. Neither ultrasonic nor solvent welding can bond plastic to metals or glass ƒ?? only adhesives can provide such a bond. In many cases, adhesives are the low cost fastening method compared to mechanical fasteners, which must be inventoried, require pre-assembly preparation, and are labor intensive. Adhesives are one-size-fitsall, and can be easily automated in a production environment. The newest and fastest growing adhesive technology for instant plastic bonding applications are enhanced Cyanoacrylates (CAs) (Instant adhesives, often referred to as super glues) and ultraviolet (UV) and visible light curing adhesives, CAs and Light curing adhesives are ideally suited for in-line, automated dispensing and curing. These adhesives can cure rapidly, while providing long open time.

There has been no adequate laser welding method for fluorocarbon polymer such as PFA and PTFE. An innovative CO2 laser welding method [1] is applied for overlapped PFA polymer film sheet. The features of the welding procedure are: to use a solid heat sink transparent to CO2 laser beam to use no pigmentation or dye for radiation absorption enhancement and to sustain thermal damage on the surface. The feasibility of the procedure was confirmed to be usable for joining of thinner PFA film sheet than 0.3 mm. The laser welding machine in a production line was manufactured to weld the top of the circular tube of variable area flow-meters with film disk.

There has been no adequate laser welding method for fluorocarbon polymer such as PFA and PTFE. An innovative CO2 laser welding method is applied for overlapped PFA polymer film sheet. The features of the welding procedure are: to use a solid heat sink transparent to CO2 laser beam, to use no pigmentation or dye for radiation absorption enhancement, and to sustain thermal damage on the surface. The feasibility of the procedure was confirmed to be usable for joining of thinner PFA film sheet than 0.3 mm. The laser welding machine in a production line was manufactured to weld the top of the circular tube of variable area flow-meters with film disk.