Search results

As there is a strong inducement to develop new colored inorganic materials to substitute the current industrial pigments that are based on toxic metals hazardous to health and the environment, the purpose of this paper is to invent environmentally benign rare earth-based colorants as viable alternatives to the traditional toxic pigment formulations. Herein, the authors developed a series of rare earth pigments having the general formula Ca0.1 Ln0.9 PO4 ( Ln = Y , Pr , mixed rare earth oxides, RE and Di). After studying all the optical properties, the authors have gone for some coloring application in plastic like PMMA.

The designed pigments were synthesized by traditional solid-state method. Stoichiometric amounts of each reagent were mixed in an agate mortar and the mixtures were calcined at optimized temperature 1000 °C for 4 h in electric furnace followed by auto–cooling. The samples were characterized by X-ray diffraction diffraction, UV–vis spectroscopy, scanning electron microscope (SEM), particle size distribution, color coordinates determination, acid/alkali test, thermo gravimetric (TG) analysis and CIE–1976 L*a*b* color scales. Among the various lanthanide ions and calcium ion as dopant, the pigment composition shows various hues ranges from green to yellow. The designed pigments consist of non–toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates like PMMA.

The present investigations establish that various color hues can be achieved by the incorporation of suitable chromophore metal ions like calcium in various rare earth host lattice by tuning of the band gaps. The coloring mechanism is based on the strong absorption of the pigments in the blue and red regions due to electronic transitions of the micro states of rare earth ion. The pigment composition shows various hues ranges from green to yellow. The coloring mechanism is based on the tuning of band gap by the dopant like calcium in various rare earth host lattice. In addition, this pigment was chemically and thermally stable. Finally, it has applied in plastics like PMMA.

Mechanism of the color appearance using band calculations and on possible applications of rare earth phosphate powders as pigments in plastics and paints have not been explored much. However, the properties of the Ca-doped rare earth phosphate implies that this material has a potential to be applied as a satisfactory pigment for coating or coloring except for glaze, which may cause a side reaction at high temperatures, especially taking into consideration the economics and ecologies. The possibility of Ca2+ incorporation in CePO4 with monazite structure-type has been established.

The designed pigments consist of non-toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates. Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.

There is a strong incentive to design new colorants based on inorganic materials to substitute for industrial pigments that are based on heavy elements hazardous to health and the environment. However, several industrial yellow pigments such as cadmium yellow (CdS), chrome yellow (PbCrO4) and nickel titanium yellow (TiO2-NiO-Sb2O3) contain the harmful elements (e.g. Cd, Pb, Cr and Sb) for the human body as well as the environment. The designed pigments consist of non-toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates. Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.

There is a strong incentive to design new colorants based on inorganic materials to substitute for industrial pigments that are based on heavy elements hazardous to health and the environment. However, several industrial yellow pigments such as cadmium yellow (CdS), chrome yellow (PbCrO4) and nickel titanium yellow (TiO2-NiO-Sb2O3) contain the harmful elements (e.g. Cd, Pb, Cr and Sb) for the human body as well as the environment. So, the authors have developed new class of inorganic pigments that are both non-toxic and environmentally unimpeachable, while preserving or even exceeding the optical, thermal and chemical characteristics of the existing commercial pigments. The developed colorants find practical applications in polymer matrix like PMMA.

This article is an attempt to discuss pigments used in the paint, printing ink, plastics and rubber industries in a general way, prior to their more detailed description by specialists in the subsequent articles in this issue of the journal.

Water‐borne coatings Increasing use of water‐borne emulsion coatings for original equipment manufacturers (OEM) and product finishes is requiring greater efficiency in coalescing‐aid solvents, an Eastman Chemical Co. representative said at a recent Chicago Society for Coatings Technology meeting. Eastman's Ronald K. Litton said emulsions designed for OEM and industrial applications have higher glass transition temperatures than emulsions used in architectural paints. That requires higher levels of coalescing aid to achieve good film formation. As a result, coalescing‐aid efficiency with a given emulsion system is a key factor, both from environmental (lower‐volatile organic compound (VOC)) and economic standpoints. Several properties should be examined when a coalescing aid is selected for water‐borne emulsion industrial coatings. The formulator should consider the evaporation rate and solubility parameter of the coalescing aid, along with its distribution pattern in a specific emulsion system. Those properties are important in defining the efficiency of a coalescing aid in terms of its ability to lower the minimum film‐forming temperature (MFFT) of an emulsion system. The coalescing aids also must be hydrolytically stable to provide minimum loss of efficiency due to ageing, Litton said. He showed several charts designed to assist formulators in the selection of optimum coalescing aids for emulsion systems. At the same conference, James T.K. Woo of The Glidden Co. discussed the grafting of high‐molecular‐weight epoxy resins with styrene‐methacrylic acid monomers, producing a water‐reducible copolymer. Grafting takes place at the aliphatic carbons of the epoxy resin, according to carbon‐13 NMR spectroscopy. The study was a follow‐up to a paper presented 14 years ago. Woo said recent research indicates that five grafting “peaks” were identified on a 400 megacycle carbon‐13 nuclear magnetic resonance spectroscopy instrument. The paper provided several theoretical calculation on grafting. Three of the graft peaks resulted from grafting at the secondary methylene carbons ‐CH2‐ and two resulted from grafting at the tertiary carbon ‐CH‐. The ratio of grafting at ‐CH2‐ to ‐CH‐appears to be 2.7:1 — lower than the 4:1 ratio of protons present on the aliphatic carbons that are susceptible to hydrogen abstraction leading to grafting. That indicates that the tertiary hydrogen is somwhat more susceptible to grafting than the methylene hydrogens, he said.

A selection of organic and inorganic pigments has been evaluated in an epoxy powder coating system and the results are tabulated and discussed.

Surfex '88 is the first UK exhibition with the new Akzo Corporate Identity to operate in a more market orientated structure. Within the chemical division of Akzo a group has been formed to promote the wide range of Akzo chemicals for coatings applications. Among the products that can be discussed will be:

The purpose of this paper is to study the effects of water immersion‐freeze‐thaw treatment on the physical properties, flexural strength (FS) and morphology of wood‐polypropylene composites containing pigments.

Wood‐polypropylene composites containing brown, green and grey pigments were compounded in a conical twin‐screw extruder. A composite manufactured without any pigment addition was used as a reference. The amount of pelletized wood, polypropylene and coupling agent (MAPP) was kept constant. The moisture content, thickness swelling (TS), FS and surface colour of the composites were measured before and after water immersion‐freeze‐thaw cycling. Scanning electron microscopy (SEM) was used to study the morphology of the composites.

FS and dimensional stability were reduced after exposure to water immersion‐freeze‐thaw cycling for all composites. The surface properties (colour and roughness) of the composites also changed after exposure to water immersion‐freeze‐thaw cycling. The degree of change depended on the presence of pigment and the type of polypropylene (neat or recycled), however.

This study is a part of an ongoing study on weathering of wood‐polymer composites (WPC) containing different additives. The results of this study were obtained from accelerated laboratory experiments.

Inorganic pigments are widely used as additives in plastics, because they have an excellent UV absorption, good IR‐reflective properties and heat stability. The research revealed that metal‐containing pigments had an effect on degradation in quality of wood‐polypropylene composites exposed to water immersion‐freeze‐thaw cyclic treatment. The addition of metal‐containing pigments to composite formulation resulted in a higher susceptibility of wood‐polypropylene composites to water absorption, and as a consequence to a higher drop of FS compared to composites made without pigment. The polymer matrix plays an important role in the protection of WPC against weathering.

This paper will help in understanding possible problems in the durability of wood‐polypropylene composites compounded with metal‐based pigments when they are exposed to water immersion‐freeze‐thaw cyclic treatment.

The fluorescence of organic dyes is associated with the individual molecules of the dyes, and in order for them to fluoresce efficiently, they must be molecularly dissolved and in fairly low concentrations from about 1 to 4%. In the pure solid state or in very concentrated solutions the dyes have almost no fluorescence and appear as dark or dirty red, yellow and green powders or solutions. The individual molecules of the dyes are so close together that they simply quench or reabsorb their own fluorescent light. Since the dyes are organic in nature it is necessary to have a medium or carrier in order to put them into solution, and to have a pigment it is necessary that this medium be a solid. The type of material which meets these requirements for the dyes is an organic resin, and daylight fluorescent pigments are actually transparent organic resin particles containing dyes in solution which are capable of fluorescing.

The surge of interest in speciality colourants in recent years shows no signs of diminishing despite the scarcity of some of the dyestuffs and pigments necessary to achieve unusual effects. Such an upward trend may be common to many industries, but suppliers of daylight fluorescent pigments have not been the slowest to develop new effects for innovative customers. Shortly after the introduction by Sterling Industrial Colour Ltd of its FLARE 920 Series of high strength polyamide based daylight fluorescent pigments for blow moulded plastics, it was discovered that this range could be combined with other speciality colourants to achieve startling effects, not only in plastics but in a variety of other applications. Previously fluorescent pigments were used alone and against a white background for best effect in inks, paints and plastics because the slightest contamination was known to reduce the fluorescent effect. But the exceptional strength of the FLARE 920 range permits its reduction with pearlescents and/or opaque whiteners in all these and other applications.