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Lamination of poly(tetrafluoroethylene) (PTFE) film to a copper foil or to an epoxy-based print circuit board (PCB) substrate (FR4[R]) was carried out. Lamination was achieved during surface graft copolymerization of glycidyl methacrylate (GMA) on an Ar plasma pretreated PTFE film at elevated temperature and in the presence of an epoxy resin adhesive. The plasma pretreatment introduces peroxides which are thermally degraded into free radicals to initiate the graft polymerization of GMA on the PTFE surface. The graft copolymerization with concurrent lamination is carried out in the complete absence of a polymerization initiator or system degassing. The modified surfaces and interfaces are characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The adhesion strength between the PTFE film and copper or the FR4[R] substrate was assessed by the T-peel strength test method. The adhesion strength was affected by plasma pretreatment time, as well as the grafting and curing temperature. The PTFE/GMA-epoxy resin/Cu and PTFE/GMA-epoxy resin/FR4 assemblies exhibit significant higher interfacial adhesion strengths compared to those assemblies in which only epoxy resin or GMA was used. They also exhibit better interfacial adhesion reliability. The PTFE/GMA-epoxy resin/Cu and PTFE/GMA-epoxy resin/FR4[R] joints delaminated by cohesive failure inside the bulk of PTFE film. The results suggest that the enhanced adhesion between the graft-modified PTFE film and copper or FR4[R] surfaces is attributable to the formation of covalent bonds between the tethered GMA graft chains on PTFE and the network of epoxy resin.

The essential oils obtained by hydrodistillation of the leaves and rhizomes of Homalomena sagittifolia Jungh. were analysed by capillary GC and GC-MS; 59 constituents were identified in the leaf oil, monoterpene hydrocarbons being the major chemical class with α-pinene (22.2%) and β-pinene (17.2%) dominating. Among the sesquiterpenoids present, the most abundant was neointermedeol. The rhizome oil yielded 49 identified constituents and was characterized by a very high level of linalool (61.9%). Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A differential-mode ultra-wideband (UWB) bandpass filter on a microstrip line is proposed and implemented with good common-mode suppression. A sixth-stage branch-line differential-mode bandpass filter is designed with the specified UWB passband. By introducing two pairs of open-circuited stubs in the symmetrical plane, the differential-mode frequency response remains unchanged but its common-mode counterpart is reshaped to achieve the stopband in the overall UWB. A filter is then fabricated for experimental verification of the proposed technique. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband bandpass filter with good upper-stopband performance is presented. A wide stopband above the desired passband is realised relying on three transmission zeros of capacitive-ended parallel coupled lines. A modified multiple-mode resonator is formed with a self-contained stopband. By linking this resonator with two interdigital coupled lines, an ultra-wideband bandpass filter is constituted. Predicted results are verified by experiment in a frequency range of DC to 25 GHz. [ABSTRACT FROM AUTHOR]

Moss samples were collected from the island of Singapore and analysed for a range of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). Although all compounds analysed have been banned from use in Singapore, they were detected in all samples collected. Among the hexachlorocyclohexanes (HCH), beta-HCH was the most dominant isomer, while trans-chlorane was found to be the most dominant cyclodiene pesticide. High levels (79.12 ng g(-1)) of PCBs were detected in mosses collected from a nearby island due to active accumulation of pollutants associated with boat emissions. Significant spatial variations in the levels of organic pollutants in Singapore were largely absent, indicating that air masses moving over the island deposit OCPs and PCBs in a uniform pattern. A comparison of moss pollutant levels with available data from Czech Republic showed that dichlorodiphenyldichloroethylene (p,p'-DDE), dichlorodiphenyltrichloroethane (p,p'-DDT) and PCB levels in Singapore are the highest. The presence of these compounds suggests that they are still used in the region and are environmentally recalcitrant.