Superficial Modification Research Articles

Surface modification of a polypropylene film by microwave plasma and the adhesion of a vacuum‐deposited aluminium layer

AbstractIn order to improve the adhesion properties of polypropylene on a thin aluminium layer deposited under vacuum, a superficial modification of the polymer has been carried out by exposing the polymer surface to a microwave plasma from gas of different nature and composition.The concentration of the present species in the sample proximity (downstream) has been measured by emission spectroscopy.Superficial polymer modifications have been analysed by ESCA and by measuring contact angles with polar and apolar liquids. The adhesion measurements have been performed by pull‐off tests.The wettability increase has been attributed to the creation of a very thin superficial layer which is partially soluble in methanol and includes carboxylic and ethylenic functions being observed by ESCA.Wettability and adhesion depend on the composition of the gas mixture used. They increase with the atomic oxygen quantities which are created in the discharge and carried away in post‐discharge by the gas flow. A relationship has been established between the tensile stress values obtained by the pull‐off test and the polar interaction values measured during dewetting.

Chemical Migration from Polypropylene and Polyethylene Aseptic Food Packaging as Affected by Hydrogen Peroxide Sterilization

The possible effects of hydrogen peroxide (HP) sterilization on migration from polypropylene (PP) and polyethylene (PE) food-packaging materials have been investigated. A number of indices have been used to measure any changes in polymer composition, surface characteristics and migration levels into food simulants, brought about by commercial sterilization procedures using HP. These measurements revealed that changes were limited to a slight and superficial modification of the polymer surface. The composition of the polymer and migration levels from the polymer to food simulants were not changed markedly. It is concluded that neither the nature nor the level of migration into food is likely to be influenced significantly by the aseptic-packaging process of polymer sterilization using HP.

Futuristic education

Where we have been is the best indicator of where we are going. This is still true, even in these times of extensive and intensive change, when customs and institutions are revised so frequently and so rapidly as to appear as blurs rather than identifiable constructs. The human animal resists change. Change is contrary to the laws of physics and human nature which has to do with bodies at rest attempting to remain at rest. Argues that nowhere is this more true than in the field of education: we know what worked in the past, we know what is good for students, we know what our public expects of the schools, and we are reluctant to make changes beyond the superficial modification of class schedules, grouping, course title changes, etc, but resist change we must.

Superficial modification of SiC powder by chemical oxidation

Superficial modification of SiC powder by chemical oxidation

Role of tungsten in supported Pt-W reforming catalysts Part I. Modification of platinum activity and selectivity by addition of tungsten

Bimetallic supported Pt-W catalysts are studied for 3-methylhexane reforming. An increase in the activity and selectivity in aromatization is found for Pt-low W/Al2O3 catalysts compared to the classical monometallic Pt/Al2O3 catalyst. Changes in activity and selectivity, for bimetallic catalysts, are attributed to “tungsten moderator interaction” effects between platinum and support which modify the metallic particle sizes. These changes are observed on Pt-high W/Al2O3 and Pt-W/SiO2 catalysts. Superficial carbide formation and modification of the hydrogen chemisorption may be proposed to explain the reactivity of Pt-W catalysts under low hydrogen pressure.

Structured Round Cairns in West Central Wales.

An assemblage of cairns, distinguished by the incorporation of orthostatic elements suggestive of ring structure, is described from an area of central Wales. The morphology and distribution of the sites are discussed in terms of geology, erosional processes and land-use history. It is concluded that the form taken by individual cairns is largely a function of local environmental constraints, their distribution limited by factors of survival and discovery. The susceptibility of the monuments to superficial modification is stressed and caution is urged in the application of classificatory schemes.

The erosion history of Shetland: a review

The Shetland Islands are an inlier of Caledonian rocks rising above the surrounding younger sediments forming the sea floor. They are also an erosional remnant on a stable block, the Shetland-Orkney Platform, which is bounded by deep sedimentary basins. The history of sedimentation in these basins indicates that this erosional remnant may have been formed as a monadnock in Triassic times or earlier and first became an island in Jurassic times. Subaerial erosion was dominant in the area until Jurassic times but since then most erosion in the islands has taken place by cliff retreat due to rising and falling sea level. Erosion platforms, other than the one surrounding the islands at about -82 m (45 fm), are at best poorly developed. The subaerial erosion surface in the islands is probably of great age and in most places shows only superficial modification by glaciation. The islands are now sinking beneath the sea and in consequence show many of the features characteristic of a newly drowned coastline.