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Serendipity has been a major player in most dye discoveries, and phthalocyanines are no exception. The true account of their discovery in 1928 is given using information provided by one of the individuals involved (Ron Greig). One of the inventors, Drescher, after making a key observation as to the nature of the insoluble blue impurity formed in the routine manufacture of phthalimide from phthalic anhydride, was killed weeks later when, on his beloved Sunbeam motorcycle, he had a head-on collision with a steamroller on his way to work. The unique properties of phthalocyanine dyes and pigments make them the colorant of choice for most blue and green colours. Thus most blue and green cars, including sports cars, are coloured by phthalocyanine pigments. In addition to these traditional uses, phthalocyanines are also finding extensive use in modern hi-tech areas. They are used for their colour as, for example, cyan dyes in ink jet printing, and in colourless applications such as infrared absorbers in security. The discovery, traditional and hitech applications of phthalocyanines are described in detail in this paper.

The effects of three organic colorants on photo-initiated crosslinking and photo-oxidation degradation of polyethylene (PE) samples irradiated by microwave excited (MWE) UV lamp in the melt and the related mechanism have been studied by gel content and thermal extension rate determinations, X-ray photoelectron spectroscopy (XPS), mechanical property tests, UV spectroscopy, and light microscope. The data from the gel content and thermal extension rate determinations of photo-crosslinked polyethylene (XLPE) samples show that the three colorants can decrease the efficiency of photo-initiated crosslinking of polyethylene to some different degree, in which the effect of red colorant is the largest among the three colorants. The colorized samples of 1 mm thickness are easily to be crosslinked to a satisfactory gel content of about 70% by the MWE lamp and optimized reaction conditions, such as the concentration of colorant, irradiation time, and so on. The XPS results give the evidence that the colorants can accelerate the surface photo-oxidation during the photo-crosslinking of polyethylene. The photo-oxidation products such as -CH₂-O- and -C(C=O)- groups on the surface of XLPE samples with the colorants apparently increase with increasing the irradiation time. The data from the mechanical tests show that the colorants reduce the tensile strength and improve the elongation at break of XLPE samples. All the above results show that the effects of the three colorants on photo-initiated crosslinking and photo-oxidative degradation decrease with the order of red > blue > green colorants. The light microscope photos show that the colorant can disperse well in PE resin. The mechanism of the colorant effects can be elucidated by comparison of the UV absorption spectra of photo-initiator and colorants. This is because the colorants absorb the same UV wavelength regions as photo-initiator, and thus decrease the photo-crosslinking efficiency of photo-initiator and accelerate the surface photo-oxidation of XLPE materials.

After the Industrial Revolution, in the 21st century, mankind is facing the harsh test of economic growth and environmental protection. Colorant research contains cross-field creative thinking that has been added to develop our Cultural Creative Industry to reduce the pollution by artificial dyes. The extensive usage of biomaterials is not only for natural dyeing but also for the development of biotechnology and pharmaceutical products to fight viruses.