Polyurethane-urea network

Step Non-linear Network Polymers Epoxy resins Melamine Phenolic Polyurethanes Urea... 

Das, S., Banthia, A. K., Adhikari, B. (2006). Removal of chlorinated volatile organic contaminants from water by pervaporation using a novel polyurethane urea-poly/(methyl metacrilate) interpenetrating network membrane, Chem. Ena. Sri.. 61, 6454-6467. 

M. Matsuo, T. K. Kwei, D. Klempner, and H. L. Frisch, Structure Property Relations in Polyacrylate-Poly(urethane-urea) Interpenetrating Polymer Networks, Polym. Eng. Sci. 10(6), 327 (1970). Polyacrylate/polyurethane urea lENs. Polyurethane/ureapolyacrylate lENs. Morphology via electron microscopy. 

Melgar-Lesmes P, Morral-Rmz G, Solans C, Garcia-Cehna MJ. Quantifying the bioadhesive properties of surface-modified polyurethane-urea nanoparticles in the vascular network. Colloids SurfB Biointerfaces 2014 118 280-8. 

It was determined that a dense physical network having ciosslinking points forming hard domains is characteristic of segmented polyurethane ureas. This physical network limits swelling of SPUU in organic liquids that carmot dissolve hard domains. 

The effect of preliminaiy strain on the sorption of liquids of various chemical structure by segmented polyurethane and polyurethane ureas was investigated. It was shown that the swelling degree increases after strain as a result of partial destmction of domain structure and decrease in effective density of the physical network formed by hard domains. 

Expression [6.6.8] describes the kinetics of the normal absorption of liquid in the presence of which the spatial polymer network remains unchanged (absence of chemical network destraction). In the case of micro-heterogeneous materials with block stmcture, such as segmented polynrethanes and polyurethane ureas, the absorption of the liquid should not lead to the chemical network destmction, and to the destmction of the physical network having crosslinking points forming hard domains. 

Not only are these reactions of importance in the development of the cross-linked polyurethane networks which are involved in the manufacture of most polyurethane products but many are now also being used to produce modified isocycuiates. For example, modified TDI types containing allophanate, urethane and urea groups are now being used in flexible foam manufacture. For flexible integral foams and for reaction injection moulding, modified MDIs and carbodi-imide MDI modifications cU"e employed. 

By means of chemical reactions thermosetting plastics form three-dimensional structures. In the example above the nitrogen compound urea reacts with formaldehyde (methanal), in which process three molecules combine and a molecule of water is formed. In this example two H atoms react, but all other H atoms ( ) enter into the same reaction. Since urea is a three-dimensional molecule, the network will also be three-dimensional. For instance switches and sockets are made of UF. Other thermosetting plastics are polyurethane PU (insulation) and melamine-formaldehyde MF (panels). 

Many thermoset polymers of major commercial importance are synthesized by step-growth polymerization, as the case of unsaturated polyester, polyurethanes, melamines, phenolic and urea formaldehyde resins, epoxy resins, silicons, etc. In these systems, the crosslinking process, which leads to a polymer network formation, is usually referred to as curing. 

The catalyst or add source can consist of ammonium phosphate or polyphosphate salts, phosphoric add-derived amides or alkyl or halo-alkyl phosphates. Charring agents are based on molecular structures that can form cross-linked networks such as pentaerythritol, sorbitol, melamine, and phenol-formaldehyde resins. Other polymeric systems capable of intumescence are some polyamides and polyurethanes. Blowing agents help form a porous structure in the char and can fadlitate its formation. Common blowing agents are based on urea and urea-formaldehyde resins, melamines, and polyamides that can liberate moisture. 

G. C. Berry and M. Dror, Modification of Polyurethanes by Interpenetrating Polymer Network Formation with Hydrogels, Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Pap. 38(1), 465 (1978). Polyether-urethane-urea block copolymers with crosslinked HEMA, NVP, or acrylamide. IPNs and gradient IPNs for biomedical purposes. Strength, water swellability, and good blood compatibility. 

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