Pigment & Resin Technology

H.L. Manock

2000 Pigment & Resin Technology

doi: 10.1108/03699420010334295

Waterborne polyurethane dispersions (PUDs) continue to show growth in commercial usage due to the ever increasing environmental legislation to reduce VOC in coating and adhesive materials. The transition from solvent‐based to waterborne has also been facilitated by advances in both the chemistry and technology employed and the formulation expertise required. This has resulted in coating performance that cannot only match but in some cases surpass their solvent‐based counterparts. This paper gives an overview of PUDs and introduces urethane/acrylic hybrids, giving an insight into the chemistry and technology. Particular emphasis is given to new developments and the application areas where they are finding increasing use. Some formulating techniques are also illustrated.

Lijun Qiao; Allan J. Easteal; Clive J. Bolt; Philip K. Coveny; Robert A. Franich

2000 Pigment & Resin Technology

doi: 10.1108/03699420010334303

Four different approaches were taken to improve the water resistance of poly(vinyl acetate) (PVAc) emulsion adhesives. The improved wood adhesives were tested according to the ISO 9020 standard. Tensile storage modulus (E’) and glass transition temperature of the polymer films were measured using dynamic mechanical thermal analysis to quantify the influence of different approaches on those variables. Gel fraction and swelling ratio of the polymer film were measured to evaluate internal crosslink density. The experimental results showed that blending melamine/urea/formaldehyde (MUF) resin with PVAc emulsions modified the water resistance considerably and the film had a high E’ since an interpenetrating network‐type structure was formed in the polymer. The advantages and limitations of each modification were assessed on the basis of comparison of the results.

G. Batis; N. Kouloumbi ; P. Pantazopoulou

2000 Pigment & Resin Technology

doi: 10.1108/03699420010334312

The use of coatings (organic and inorganic) for the protection of reinforced concrete is widespread. The advantages of inorganic coatings are that they are stable in UV‐radiation, non‐combustible, do not foul and have a microcrystalline texture, while organic coatings have the advantage of low permeability of carbon dioxide, sulphur dioxide and water. The aim of the present work was to compare, in the presence of chloride ions, the performance of an acrylic dispersion and a silicate coating, when the latter was or was not combined with a corrosion inhibitor (N‐N’‐dimethylaminoethanol). The behaviour of the silicate coating was examined as its use is increasing due to environmental reasons and as it can be applied for the rehabilitation of old structures. Half‐cell potential measurements, mass loss and carbonation depth measurements, as well as chloride diffusion rate revealed that the acrylic dispersion provides better protection of reinforcing steel in concrete than the silicate coating, but the combination of the silicate coating with the corrosion inhibitor provides the best level of concrete protection.

A. Kalendová

2000 Pigment & Resin Technology

doi: 10.1108/03699420010334321

The anticorrosion protection of metal using organic coatings destined for applications at temperatures in a range of 200‐500°C is a specific problem, both from the binder base and appropriate anticorrosive pigment points of view. A prospective and efficient solution is provided by using anticorrosive spinel‐type pigments. The stability of spinel‐like compounds consists of the stabilities of their compositions and structures, which manifest themselves in the stability of physicochemical structures thereof, also in constancies of color and application properties.