Gradient polymeric materials

Abstract

Data on gradient polymeric materials that possess broadly varying mechanical, optical, and other properties are generalized. The term "gradient materials of the first type" refers to materials that possess a gradually variable elasticity modulus in the range of 3-2000 MPa for the same material that possesses no layers or interfaces, pasting, heat sealing, etc. They are produced as either transpar ent molds or composites with various reinforced fillers. The synthesis of these materials is based on the formation of polymer networks containing bulky cross linked points with short flexible fragments linking them. These networks have been computer simulated using the physical approach developed by the authors and the chosen software, which allows one to calculate polymer properties based on their chemical structure and the implementation of computerized synthesis of polymers with pre scribed properties. The term "gradient materials of the second type" refers to materials with abruptly changing elasticity modulus and transition zone between the glassy and the rubbery states. GRADIENT POLYMERIC MATERIALS 109 pound. Since the search for such a structure is one of the objectives of this method, consistent description of structures in the method of atomic constants and in CPOS must be provided. The table of atoms and the table of relatedness that sets the selection of atoms and types of bonds in the compound structure are fundamental for CPOS software. The application of this method induces the suit ability of forming these tables for every processed formula of the repeating unit. The problem of the user's communication with the software is of special interest. The image of the structure represents a planar dis position of atoms linked by definite types of bonds. If necessary, correspondence to linear Wiswesser for mulas [10] or Morgan's record form [11] is set using tables of atoms or relatedness. The problem of unique interpretation of the repeating unit structure indicated on the display is of importance. For this purpose, the presence of information about atoms, groups of atoms, and bonds in the database is monitored by the program. The program is compatible with Windows 95 or more recent versions.The Cascade program allows one to calculate more than 60 properties of polymers and copolymers. The most fundamental properties in accordance with the review are the van der Waals volume, Hildebrand solubility parameter, surface energy, refractive index at room temperature, dielectric constant at room temperature, glass transition temperature, dependence of glass transition temperature on molecular mass, temperature of onset of intensive thermal degradation, interface tension at the polymer-polymer boundary, and the elasticity modulus of rubber (rubber like plateau).The software enables one to calculate the properties of copolymers, homogeneous mixtures of poly mers, etc. The Cascade program enables the calculation of 16 characteristics for low molecular weight organic liquids. Calculation of Elasticity Modulus for Polyme...

Effect of a Reinforcing Layer on the Mechanical Loss Tangent of Vibration-Absorbing Materials

“…Increase in the mechanical loss tangent (both relative to the values of VTP-1V specimens without a reinforcing layer and for similar specimens with a metal reinforcing layer) at T = 100°C may be due to the influence of the binder of the reinforcing layer. As is known, the maximum mechanical losses in polymers are observed above their glass transition temperature in the zone of the most strongly developed relaxation effects [28,29]. The glass transition temperature of the epoxy rubber adhesive film used as the binder, according to data of thermomechanical analysis (TMA), lies in the range 90-110°C.…”

Achievements in polycondensation and condensation polymers

“…Owing to variation in the concentration of these groups, gradient PU composite materials with differ ent moduli were prepared [106]. The kinetics of for mation of isocyanurate networks in the polymer was studied via IR and NMR spectroscopy [107,108].…”

Reaction kinetics and properties of MDI base poly (urethane-isocyanurate) network polymers

“…Since the trimerization of isocyanate occurs easily and controllably to form a clear trifunctional isocyanate ring, this reaction is an ideal candidate for the synthesis of a clear polymer network [ 3–5 ]. The trimer reaction of isocyanate can be used to prepare many kinds of materials, such as resin [ 6 ], foams [ 7 ], aerogel [ 8 , 9 ], hydrogel [ 10 , 11 ], polyurethane gradient material [ 12 , 13 ], shape memory material [ 14 ], etc. and it has been applied to aerospace, aviation, biology, medicine, shipbuilding and other fields.…”

“…Korshak et al [ 18 ] discussed in detail the formation mechanism, catalyst selection, reaction temperature and time of TDI-Based Poly (urethane-isocyanurate) network, and considered that the formation of isocyanurate ring can be regarded as the result of the attack of C atom and N atom on isocyanurate ring in isocyanate trimer after PGE epoxy ring is opened, The best reaction condition is to use bisphenol A diglycidyl ether as catalyst and heat the reaction at 177–230 °C for 8–10 h. Dekamin et al [ 19 ] used TDI and poly(propylene glycol) as raw materials to prepare polyurethane isocyanurate network by prepolymer method in the presence of tetrabutylammonium phthalimide-N-oxyl (TBAPINO) or tetraethylammonium 2-(carbamoyl)benzoate (TEACB) as effective and metal-free cyclotrimerization catalysts. Based on the above reaction mechanism, Askadskii et al [ 12 , 13 ] prepared complex amine catalyst with N, N-Dimethylbenzylamine (DMBA) and epoxy resin(ED-22), which was used as the catalyst for cyclotrimerization to synthesize poly (epoxy-isocyanurate) network. Due to the presence of complex amine catalyst, the cyclotrimerization reaction is selective and the side reactions are reduced.…”