unsaturated polyester

Unsaturated polyester resins (UPRs) including ortho, iso, bisphenolic and vinylester are the most widely used thermosetting polymeric resins in the form of coating and matrix in the industry, making up around three quarters of all thermoset resins used in the industry. The major advantages of UPRs include low cost, low viscosity, good mechanical properties and chemical resistance, lightness, low moisture absorption, curing without the formation of volatiles, and simple processing with conventional processing methods. UPRs have been used  in a wide variety of applications including composites, coatings, sealants, chemical and fuel storage tanks, and high-performance components for the construction, marine and land transportation, and electrical industries. However their high shrinkage after curing, low fire resistance and  environmental pollution due to volatile styrene have limited their use. In the past decades, the use of nanofillers in polymers to form polymer nanocomposites has attracted attention due to the ability to combine the advantages of nanofillers and polymers. In addition, the development of nanocomposites of UPRs has made these resins desirable for current and emerging applications that require high specific strength, electromagnetic shielding and improved thermal stability. However, due to the high tendency of nanoparticles to agglomerate, the main challenge in the preparation of nanocomposites is to achieve a homogeneous distribution of nanofillers in the matrix, which is the main key to achieving the desired properties. Therefore, the aim of this study is to evaluate extensive research in this field and to recognize the existing limitations related to the manufacture of these nanocomposites. For this purpose, firstly, the types of nanofillers are categorized and the mixing of nanofillers with UPRs is introduced. Then, the effect of adding nanofillers on the properties of these nanocomposites is reviewed according to the research works done in this field.

Double base propellant consists of two main components, nitrocellulose and nitroglycerin and nitroglycerin fickian diffusion from inter to surface of propellant, is the main problem of this type of propellants. Thus, providing a model for predicting migration during storage and also practical solutions in decreasing of nitroglycerine migration is one of the favorite subjects for propellant specialists. One of the ways to decrease migration, is using of modified inhibitor based on mineral unsaturated polyesters contain mineral fillers. Herein, at the first, several unsaturated polyester inhibitor in the presence of mineral filler (nano clay, modified nanoclay, silica, alumina trihydrates,15%, and alumina trihydrates, 30%) were synthesized and the influence of nitroglycerin was modeled by immersion test and the diffusion coefficients were calculated. The results showed that the modified unsaturated polyester inhibitor has a diffusion coefficient of 1.027×10-4 cm2/s that in the presence of alumina three hydrates as the mineral filler, the penetration coefficient decreased to 6.777×10-6 cm2/s. Also the relative migrated mass at the infinitive time to the mentioned inhibitor was 6.4622 and it is decreased to 2.469 in the presence of mineral filler. So, presence of filler in the inhibitor matrix, can significantly decreases nitroglycerin diffusion, increasing the safety and the lifetime of propellant .

Unsaturated polyesters are used as a inhibitor in double base rocket propellant grains. In this paper, the effect of chain length glycol, filler addition, varying amounts of styrene and adding compounds containing halogens on the gel time, the exothermic peak temperature, viscosity, tensile strength, percent elongation, strong bonding with the propellant, the amount nitroglycerin migration in unsaturated Polyester will be reviewed. The results showed that a significant improvement of nitroglycerin migration, gel time, exotherm peak temperature and mechanical properties when polyester chain length is reduced. It also reduces water absorption and nitroglycerin was observed with increasing concentrations of styrene monomer to 40 percent in polyester systems. The use of flame retardant materials such as EACGP also Showed improved resistance to flame and oxygen index polymer.

Thermal properties, flammability and mechanical properties of three different kinds of unsaturated polyester resins, ortho, iso and vinyl ester and an epoxy resin based on diglycidyl ether of bisphenol-A were investigated. Since these resins are widely used in the composite industry it is vital to recognize their properties. For this purpose, viscosity, burning rate, limiting oxygen index (LOI) and flexural properties were measured. Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis were also performed. The viscosity of unsaturated polyester resins which was in the range of 300 to 450 cp showed an advantage compared to the viscosity of epoxy resin which was in the range of 600 to 1000 cp. The low viscosity property which is usually seen in unsaturated polyester resins is very important from the processing point of view, which in turn helps to ensure a simple processing. The ortho resin showed the highest conversion and conversion rate among the three unsaturated polyester resins. The vinyl ester resin showed a higher conversion than the iso resin. The results showed that the vinyl ester resin had the highest thermal resistance, flammability and mechanical properties among the unsaturated polyester resins used in this work. On the other hand, although the epoxy resin showed the highest burning rate but it had the highest carbon residue or char yield (12.4%) and LOI (20.2%), and consequently the highest thermal resistance. The results of flexural test showed that the epoxy resin had the highest flexural strength (116 MPa) and modulus (4.1 GPa) and the lowest deflection-at-break (2.8%) and toughness in comparison with the unsaturated polyester resins used in this work.