Polymers blushes

Borisov OV, Zhulina EB (2008) Responsive polymer blushes a theoretical outlook. In Galaev I, Mattiasson B (eds) Smart polymers applications in biotechnology and biomedidne. 

The interaction of blood with PVC-P based on a phthalate and trimellitate plasticiser has shown that there is a higher reactivity for the trimellitate, which correlated with the plasticiser distribution at the polymer surface (316). Another important aspect is for the medical packaging to be suitable for sterilisation of the contents. Details are available of improving the gamma irradiation stability of PVC-P in order to retain colour (447). In addition to unacceptable colour formation, excessive shifts in pH and extractables can occur in inappropriately stabilised PVC-P (301). An additive system, based on materials approved for medical use, has been developed to give low extractables and low blush with good colour and processability (239). The effects of different plasticisers... 

Methyl isoamyl ketone (5-methyl-2-hexanone) n. CH3COC2H4CH(CH3)2. A colorless liquid with a pleasant odor, used as a solvent for cellulose esters, acrylic resins, and certain vinyl polymers. It has a high solvent power and low evaporation rate, making it useful as a retarder solvent that promotes flow-out of coatings and reduces blushing. 

Blushing Blushing occurs as a milky opalescence within a film of lacquer. Blushing can occur when a liquid coating absorbs water from the environment or object, causing the dissolved polymer to precipitate. 

The external evidence of attack may be blushing (loss of gloss), chalking, change in color of the product, or extreme brittleness as in Fig. 9.52. These effects are often readily observed on epoxy and polyester polymers when they have been boldly exposed to the environment. However, mechanical tests will usually be required to reveal the extent of degradation of either thermoplastic or thermosetting resins unless they have been exposed for decades to direct sunlight, as in Fig. 9.52. 

Often mixtures of solvents give better results than individual solvents. Frequently, small amounts of the plastic to be cemented are dissolved in the solvents to form bodied cements. These additions of polymer aid in gap filling and accelerate setting. They also reduce shrinkage and internal stresses. If the evaporation rates of the solvents used are too high due to excessive volatUity of the solvent, crazing or blushing often results. 

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