Aage Stori

Modification of polyolefin surfaces by plasma‐induced grafting

Polar monomers have been grafted onto polyolefin surfaces with the aid of inert gas plasma. In the first stage, an inert gas plasma (argon plasma) was used to generate free radicals on the polyolefin surface. In the second stage, the plasma generator was turned off and a vinyl monomer introduced as a vapor. Monomer was surface grafted by free radical polymerization. After cleaning and drying, the samples were analyzed by XPS, IR, and contact angle. LD–PE was successfully grafted with acrylic acid, glycidyl methacrylate, methyl acrylate, and 2-hydroxy ethylacrylate. The grafting of acrylic acid was studied in more detail, and the rate of grafting was observed to increase with increasing monomer pressure and to decrease with time. The increasing of grafting temperature was found to reduce the degree of grafting. This last factor can be explained by the reduced concentration of monomer at the polymer surface or by a deactivation of surface radicals.

Reflection-absorption FT-IR studies of the specific interaction of amines and an epoxy adhesive with GPS treated aluminium surfaces

Abstract Aluminium surfaces were silanised with γ-glycidoxypropyltrimethoxysilane and the silane films were then further treated with different amines. Investigation before and after treatment, using reflection-absorption FT-IR spectroscopy, strongly indicated that a chemical reaction between the amines and the silane films took place, as observed in the intensity reduction of the epoxy band at 910 cm −1 . Increased SiOSi crosslink density was also observed. Treatment with dicyandiamide also showed the appearance of a band which was assigned to the formation of a covalent bond between the curing agent and the epoxy ring of the silane. The results partly explains the improved durability of GPS treated aluminium surfaces after bonding with one-component epoxy adhesives.

Silanisation of adhesively bonded aluminium alloy AA6060 with γ-glycidoxypropyltrimethoxysilane. I. Durability investigation

The wedge test was used to determine the durability of adhesively bonded joints of pretreated aluminium alloy AA6060 in a hydrothermal environment. Testing of joints bonded with the one-component epoxy adhesive XD4600 showed that the durability was higher for surfaces that were grit-blasted with alumina than for alkaline etched, FPL-etched, and sulphuric acid anodised surfaces. All these surfaces performed much better than those abraded with ScotchBrite®. It was discovered that increased surface roughness improved the durability, while increased surface contamination reduced the durability of the bonded joints. On a very rough surface such as the grit-blasted, the effects of surface contamination were more than outweighed by the effects of surface roughness. Treatment of some of the pretreated surfaces with a 1% aqueous solution of γ-glycidoxypropyltrimethoxysilane significantly improved the durability, but the ranking between the pretreatments was the same as before the silane treatment. The silane treatment also reduced the initial crack lengths of the wedge test specimens. The best performance was seen by the grit-blasting plus silane treatment, which performed much better than the well-established FPL-etch.

Investigation of phase behaviour in the melt in blends of single-site based linear polyethylene and ethylene–1-alkene copolymers

Abstract In this work, results obtained by blending different single-site based linear polyethylenes with different ethylene–1-alkene copolymers are presented. Several morphology maps are created, and phase separation in the blends is detected. The extent of phase separation is found to be significantly wider in both temperature and composition than reported earlier, and no closed loops of phase separation is observed. This might partly be explained from the more even comonomer distribution found in single-site materials compared to materials made by other processes. The type of short chain branches is found to be of limited (if any) importance to the extent of phase separation while a difference in molecular weight of the blend components seems to affect the extent of phase separation. Furthermore, in blends containing butyl branches, the extent of phase separation is found to be reduced if the amount of comonomer is reduced.

Thermal analysis of single-site polymers in binary blends of low-molecular-weight linear polyethylene and high-molecular-weight branched polyethylene

Abstract The cocrystallization phenomenon has been studied by blending a low-molecular-weight linear polyethylene (LPE) with a high-molecular-weight lightly branched ethylene–hexene copolymer, as a function of blend composition and cooling rate. The materials are based on single-site catalysts. Differential scanning calorimetry indicates that the upper limit on the degree of branches for cocrystallization with LPE is lower than observed in blends with Ziegler–Natta based materials, in accordance with results obtained by other authors on different single-site blend systems. The effect of the cooling rate on blends with low LPE content is probed, and the observed behaviour is discussed in light of earlier observations on similar blends.

Blends of single-site linear and branched polyethylene. II. Morphology characterisation

Abstract In this work, the morphology of a low-molecular weight single-site based linear polyethylene and several high molecular weight single-site ethylene–hexene copolymers, as well as their blends are investigated in the solid state using differential scanning calorimetry, transmission electron microscopy, atomic force microscopy and optical microscopy. Such model blends are believed to be important to elucidate the structure of polyethylene with a bimodal molecular weight distribution. The lamellae- and spherulite structure in the blend components and in the blends, and the ability to cocrystallise from the melt are found to be highly dependent on the amount of comonomer incorporation in the branched blend component.

Silanization of adhesively bonded aluminum alloy AA6060 with γ-glycidoxypropyltrimethoxysilane. II. Stability in degrading environments

Alkaline etched aluminum alloy AA6060 treated with of γ-glycidoxypropyltrimethoxysilane was investigated. The stability of the silane films in degrading environments was investigated by exposing them to acidic and alkaline solutions at 40°C, followed by analysis with reflection-absorption infrared spectroscopy. Desorption of the silane from the surface occurred at pH 4, and at a much slower rate at pH 7, while the silane film was stable at pH 8. Two models for the degradation of the silanized aluminum surface in an acidic environment were proposed: one involving simultaneously hydrolysis of the siloxane network and corrosion of the underlying aluminum surface, and the other involving only corrosion of the aluminum surface. The durability of the silane treated surface was determined using wedge tests on joints made with XD4600 one-component epoxy adhesive. The durability was significantly reduced in highly acidic environment (pH 2), but no significant differences in durability were observed in the pH range from 4 to 11, except that the durability was slightly higher in higher alkaline environment during the initial period of testing. Better durability in an alkaline environment is connected to a better stability of both the siloxane network and the aluminum surface in this environment.