Kjell Olafsen

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.

Reaction of poly(vinyl alcohol) and dialdehydes during gel formation probed by 1H n.m.r.—a kinetic study

Abstract Proton n.m.r. has been used to study the reaction between poly(vinyl alcohol) (PVA) and two different dialdehyde crosslinkers during gel formation (gels for improved oil recovery applications). The rate of formation of covalent bonds between PVA and glutaraldehyde in acidic saline water solutions was found to be of first order with respect to both the H 1 concentration and the formal dialdehyde concentration. The activation energy was found to increase with increasing dialdehyde concentration and increasing pH (3.2–4.7). The corresponding reaction rate of formation of covalent bonds between PVA and butenedial in the PVA/2,5-dimethoxy-2,5-dihydrofuran system at the same pH and temperature was found to be an order of magnitude less. Also, the activation energy was higher by approximately 50% as compared with the PVA/glutaraldehyde system. Possible reaction pathways for the generation of PVA-dialdehyde gels are discussed.

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.

Probing the gelation of polyvinylalcohol-water glutaraldehyde within a porous material by 1H n.m.r. — a preliminary investigation

Abstract Proton n.m.r. relaxation times ( T 1 , T 2 ), chemical shift and line width of the solvent water protons in a polyvinylalcohol (PVA)-glutaraldehyde-water solution confined in a porous material (glass beads) revealed no significant changes during crosslinking and gel formation. Also, the self-diffusion coefficient was constant and identical to the self-diffusion coefficient of bulk water (2 × 10 −5 cm 2 s −1 ) during the reaction. Due to the smaller self-diffusion coefficient of the polymer molecules the solvent water resonance peak could be completely removed from the spectrum by applying a pulse gradient spin-echo technique, leaving only the signal from the polymer amenable for detection. In spite of the broadening effect caused by susceptibility differences between the solid porous matrix and the confined fluid, the PVA peaks were easily resolved. The observed distribution of self-diffusion coefficients of PVA could be approximated by three single diffusion coefficients ranging from 10 −6 to 10 −9 cm 2 s −1 at 25°C. The slower diffusion coefficient was found to decrease by almost an order of magnitude during the reaction with a rate of change of approximately 3 × 10 −5 s −1 at 80°C.

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.

GELATION KINETICS OF POLYMERS CONFINED IN WATER/ OIL-SATURATED POROUS MATERIALS PROBED BY NMR

Abstract The gelation of polyvinylalcohol with glutaraldehyde confined in a water/ oil (= 3/1 in volume ratio) saturated sandstone (Bentheimer) was characterized by H NMR spin-lattice relaxation rate (1/ T)measurements and Pulse Field Gradient (PFG) NMR diffusion measurements. The gelation rate was found to be (12.8 ± 1.3) 10−1 5−1 at 340 K, which is approximately an order of magnitude faster than in bulk solution. In comparison, the gelation rate within the same porous material containing no oil phase was even faster, by a factor of 2.