Synthesis of α-hydroxy-ω-amino poly(ethylene oxide) and its use in reaction injection moulding (RIM)

Summary Computer simulations show that oligomers with two different terminal groups with dissimilar reactivities for isocyanates give a delayed viscosity rise in polyurethanes. This is a desired behaviour for RIM processes. Therefore, an -hydroxy--amino poly(ethylene oxide) (HAPEO) has been prepared. The synthesis was carried out by the ethoxylation of 2-hydroxyethyl phthalimide as a blocked amine. Hydrazinolysis appears to be the best way to obtain the deblocked oligomer. The product properties were compared with an oligomeric diamine ether (Jeffamine D2000). The gel time of HAPEO (M_n=500) and JAD2000 (M_n=2000) was the same (2 sec.). The product with HAPEO had a higher modulus, a comparable impact and tensile strength and a lower elongation at break.     

Melt compounding of polypropylene‐based clay nanocomposites

Polypropylene (PP)‐based nanocomposites containing 4 wt% maleic anhydride grafted PP (PP‐g‐MA) and 2 wt% Cloisite 20A (C20A) were prepared using various processing devices, viz., twin‐screw extruder (TSE), single‐screw extruder (SSE), and SSE with an extensional flow mixer (EFM). Two processing methods were employed: (I) masterbatch (MB) preparation in a TSE (with 10 wt% C20A and clay/compatibilizer ratio of 1:2), followed by dilution in TSE, SSE, or SSE + EFM, to 2 wt% clay loading; (II) single pass, i.e., directly compounding of dry‐blended PP‐g‐MA/clay in TSE, SSE, or SSE + EFM. It has been indicated that the quality of clay dispersion, both at micro‐ and nanolevel, of the nanocomposites depends very much on the operating conditions during processing, such as mixing intensity and residence time, thus affecting the mechanical performance. Besides that the degradation of the organoclay and the matrix is also very sensitive to these parameters. According to results of X‐ray diffraction, field emission gun scanning electron microscopy, transmission electron microscopy, and mechanical tests, the samples prepared with MB had better overall clay dispersion, which resulted in better mechanical properties. The processing equipment used for diluting MB had a marginal influence on clay dispersion and nanocomposite performance. POLYM. ENG. SCI., 47:1447–1458, 2007. © 2007 Society of Plastics Engineers     

Electronic content delivery and forensic watermarking

Today, digital content distribution is already common practice for media types like audio. It is expected that in the near future, systems like Video-on-Demand will also increase in popularity. Many Digital Right Management (DRM) models exist enforcing the copyrights associated with the distributed content. We argue that a simplified model based on so-called forensic watermarks is a viable alternative approach that closely mimics the current model of physical music and video distribution by providing a reasonable compromise between the conflicting interests of consumers and content owners. In this paper, we address the forensic watermark DRM model and introduce a generalized architecture for the distribution server and the forensic watermark tracker. In this model, important attack scenarios are identified as being the ‘copy attack’ and the watermark ‘rendering’. We show that it is more difficult to successfully work out these attack scenarios by (i) integrating a content identification and watermarking system and (ii) making the watermark (both the carrier signal as well as the payload) content dependent. In addition to these security aspects, we also focus on efficiency of the distribution server. By separating the computational efforts in so-called pre-coding and on-line computational phases, the required signal processing resources of the distribution server can be reduced significantly. The general architecture including security and efficiency requirements are analyzed in a practical example of Electronic Music Delivery (EMD). We show that computational complexity can be reduced up to a factor 4 compared to a straightforward approach. In practice, it means that with current state-of-the art computers (Pentium IV, 1 GHz) watermark embedding speeds of about 40 times Real Time (RT) can be achieved. In addition to the embedding architecture, we also demonstrate an efficient method for detecting watermarks in a forensic watermark tracker. Having multimedia identification fingerprints available (required for working with content-dependent watermarks), the efficiency of watermark detection can be enhanced by using them as side information. Again, in our EMD prototype, we demonstrate that (depending on the parameter settings) the detector can run up to 50 times faster than a blind detector, in which the original or the fingerprint is not available.     

A measure of the bullwhip effect in supply chains with stochastic lead time

In this paper, we exactly quantify the bullwhip effect, the variance amplification in replenishment orders, for cases of stochastic demand and stochastic lead time in a simple two-stage supply chain with one supplier and one retailer. In most of the previous research, the impact of order lead time on the bullwhip effect in supply chains with pre-specified demand processes is investigated mostly for cases of deterministic lead time. In this paper, we deal with a first-order autoregressive, AR(1), demand process and investigate the behavior of a measure for the bullwhip effect with respect to autoregressive coefficient and stochastic order lead time. Extension to a mixed first-order autoregressive-moving average, ARMA(1,1), demand process is also considered.     

Reinforcing effect of organoclay in rubbery and glassy epoxy resins,part 1: Dispersion and properties

The reinforcing effect of organoclay in two epoxy matrices, one rubbery and one glassy, was studied. The rubbery and glassy epoxy matrices were chosen to have a very similar chemistry to minimize its impact on the comparison of properties. The epoxy resin was EPON? 828, and the two hardeners were amine‐terminated polyoxypropylene diols, having different average molecular weights (MW) of 2000 and 230 g/mol, namely Jeffamine® D‐2000 and Jeffamine® D‐230, respectively. The nanocomposites were prepared with the organoclay Cloisite® 30B from Southern Clay Products. The quality of dispersion and intercalation/exfoliation was analyzed by means of X‐ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the curing reactivity and the thermal stability of the epoxy resin systems, respectively. Tensile properties and hardness of epoxy resin and epoxy nanocomposites were measured according to ASTM standards D638‐02 and D2240‐00, respectively. Fracture surfaces were also analyzed by FEGSEM. These two epoxy systems as well as their nanocomposites display totally different physical and mechanical behavior. It is found that the quality of clay dispersion and intercalation/exfoliation, and the mechanical behavior of the glassy and rubbery epoxy nanocomposites are distinct. The results also indicate that the presence of the clay does not significantly affect the T_g of either the rubbery or the glassy epoxy; however, the fracture surface and mechanical properties were found to be influenced by the presence of nanoclay. Finally, several different reinforcing mechanisms are proposed and discussed for the rubbery and glassy epoxy nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Self-reinforced poly(ethylene terephthalate) composites by hot consolidation of Bi-component PET yarns

Self-reinforced polymer composites or all-polymer composites have been developed to replace traditional glass-fibre-reinforced plastics (GFRP) with good lightweight, mechanical and interfacial properties and enhanced recyclability. Poly(ethylene terephthalate) (PET) is one of the most attractive polymers to be used in these fully recyclable all-polymer composites, in terms of cost and properties. In this work, unidirectional all-PET composites were prepared from skin–core structured bi-component PET multifilament yarns by a combined process of filament winding and hot-pressing. During hot-pressing, the thermoplastic copolyester skin or sheath layers were selectively melted to weld high-strength polyester cores together creating an all-PET composite. Physical properties of the resulting composites including thickness, density and void content were reported. The effect of processing parameters, i.e. consolidation temperature and pressure on mechanical properties and morphology was investigated in order to balance good interfacial adhesion with residual tensile properties of the composite.     

Conductive network formation in the melt of carbon nanotube/thermoplastic polyurethane composite

This research concerns the effect of conductive network formation in a polymer melt on the conductivity of multi-walled carbon nanotube/thermoplastic polyurethane composite systems. An extremely low percolation threshold of 0.13 wt.% was achieved in hot-pressed composite film samples, whereas a much higher CNT concentration (3–4 wt.%) is needed to form a conductive network in extruded composite strands. This is explained in terms of the dynamic percolation behaviour of the CNT network in the polymer melt. The temperature and CNT concentration needed for dynamic percolation to take effect were studied by the conductivity versus temperature behaviour of extruded strands, in an attempt to optimise the processing conditions.     

Cardanol–glycols and cardanol–glycol-based polyurethane films

The syntheses of cardanol–glycols (CGs) and CG-based polyurethane (CGPU) films have been investigated. The characterization of CGs and CGPU films were determined by IR, ¹H-NMR spectra as well as a swelling test and DSC studies. The increase of molecular weight of glycols leads to a decrease of cardanol content in CGPUs and hence decreases crosslinking density of the films, which strongly affects the swelling property and glass transition temperature. The autooxidation-polymerization of CGPUs through the double bonds of the cardanol side chain, catalyzed by cobalt salt, resulting the crosslinking films was also discussed. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:507–510, 1997     

All-cellulose composites of regenerated cellulose fibres by surface selective dissolution

All-cellulose composites of Lyocell and high modulus/strength cellulose fibres were successfully prepared using a surface selective dissolution method. The effect of immersion time of the fibres in the solvent during composite’s preparation and the effect of the starting fibre’s structure on their properties were investigated. Scanning electron microscopy, X-ray diffraction, dynamic mechanical analysis, and tensile testing were used to assess the structure and properties of the composites. These all-cellulose composites of regenerated cellulose fibres demonstrate a promising route to biocomposites with excellent mechanical and thermal properties which can also be tuned depending upon a selection of fibres and preparation parameters.     

Carbon fiber cardanol-epoxy composites

Carbon fiber composites based on tetrafunctional epoxy resin N,N,N′,N′-tetraglycidyl-2,2-bis[4-(4-aminophenoxy)phenyl]propane modified with cardanol were investigated. The differential scanning calorimetric technique was used to study the curing reaction of the neat resins. The dielectric properties of the composites were compared. The use of cardanol in epoxy resins at cardanol/epoxy molar ratios less than 0.3/1 improved the chemical resistance as well as the mechanical properties of the composites, such as the flexural strength and modulus, tensile strength and modulus, and interlaminar shear strength. Higher cardanol contents decreased such properties. The highest properties of the composites were observed with the epoxy-cardanol resin having a cardanol/epoxy molar ratio of 0.3/1. © 1996 John Wiley & Sons, Inc.