| Polymers have been applied more and more extensively in ammunition in recent years. Nitrocellulose (NC) binder and plastic belt just are the typical polymers. Binder is a key part in gun propellant, to a great extent, whcih affects the energy performance and mechanical properties of gun propellant. Nitrocellulose (NC) binder has been widely used in single-base, double-base and tri-base gun propellants, while the cryogenic mechanical properties of NC are relatively not good due to its high glass transition temperature, which limits its application in gun propellant. Glycidyl azide polymer (GAP) which is a novel energetic binder being is considered as the key component of gun propellants due to its insensitivity and high energy. The pendant azide group of GAP main chain results in low mechanical properties of gun propellants, so it is necessary to improve the mechanical properties of GAP binder. In this paper, NC and GAP were modified by the reinforcing mechanism of polymers in order to obtain the complementary of energetic binder which hopes to meet the demands of gun propellant and propellant. Recently, plastic belt especially PA66and POM have been widely used in new kinds of projectiles. The tensile strength of potassium titanate whisker reaches to7000MPa, and it also shows well wear resistance, heat resistance and low cost. So in this paper, potassium titanate whisker is tried to modify PA66and POM. The main work is as follows:Gap-based polyurethane elastomer (GAPE) with different hard segment contents were synthesized with4,4’-Diphenylmethane diisocyanate (MDI),1,4-butylene glycol(BDO) as hard segments and GAP as soft segments. The results showed that with33wt%of hard segment, the stiffness and flexibility of GAPE-2were better. The αf of GAPE-2at low temperature was larger. What’s more, the low-temperature fragility parameter and activation energy of GAPE-2were lower, respectively,55.6and271.0kJ·mor-1. As the mass fraction of hard segment increased from30%to36%, the density GAPE increased from1.35g-cm-3to1.52g·cm-3. With33wt%of hard segment, the tensile strength of GAPE-2was up to maximum13.3MPa, which was equivalent to about209%higher than that of GAPE-1with30wt%of hard segment and87.3%higher than that of GAPE-3with33wt%. And the breaking elongation of GAPE was better.Two series of blends of GAPE/NC (WN=12.0%),GAPE/NC(WN=13.5%) were prepared by solution mixing. The properties of the blends were analyzed by means of true Density, FTIR spectroscopy, dynamic mechanical analysis (DMA) and tensile testing. The Tg at low temperature of GAPE/NC (WN=13.5%) was below-3℃. The Tg at low temperature of GAPE/NC (WN=12.0%) was below-10℃. The mechanical properties of NC at low temperature were improved. When the mass fraction of GAPE was30%, the blends of GAPE/NC (WN=12.0%) exhibited good compatibility. When the mass fraction of GAPE was40%, the blends of GAPE/NC (WN=13.5%) exhibited good compatibility.What’s more, the low-temperature brittleness and flexibility of the two ratio were better. When the mass fraction of GAPE was30%, the tensile strength of GAPE/NC (WN=12.0%) was43.3MPa and its elongation was33.5%, which was5times more than that of NC. When the mass fraction of GAPE was30%, the tensile strength of GAPE/NC (WN=13.5%) was63.5MPa and its elongation was30.5%.Based on the modification of the mechanical properties of the nitrocellulose by GAPE, two blends of GAPE/TEGN/NC were prepared by solution mixing. With the GAPE content increasing, the tensile strength and the elongation of samples increased first and then decreased. When the mass fraction of GAPE-3(with36wt%of hard segment) was5%, the tensile strength of the blends increased from24.7MPa to32.1MPa and the elongation of the blends increased from37.0%to54.4%. When the mass fraction of GAPE-2(with33wt%of hard segment) was5%, the tensile strength of the blends increased from24.7MPa to32.4MPa and the elongation of the blends increased from37.0%to58.5%. TG showed that the decompostion temperature of GAPE/TEGN/NC was105℃while the decompostion temperature of TEGN/NC was127℃. This suggested that GAPE could promote the thermal decomposition process and reduce the temperature of thermal decomposition. The DMA analysis showed that the compatibility got better with GAPE adding.The polyurethane prepolymer was synthesized based on diphenylmethane4,4’-diisocyanate (MDI) and GAP, and then the prepolymer was grafted onto NC, the graft-polymer was gained. Experiments showed when the mass fraction of GAP was50%, the ε of the graft-polymer could increase to61.7%. It was obviously higher than the ε of NC. The DMA analysis indicated that the chain flexibility increased. What’s more, The lower Tg was-9.5℃, it illustrated that the mechanical properties at low temperature were improved.In order to meet the requirements of the mechanical strength and dimensional stability of plastic belts, potassium titanate whisker were used to modify PA66and POM. When the mass fraction of potassium titanate whisker was30%, the tensile strength of POM increased from55.9MPa to86.0MPa, increased by53.8%and the tensile strength of PA66increased from68.2MPa to127.6MPa, increased by87.1%. When injection temperature was210℃, mold temperature was90℃and injection pressure was55MPa, the tensile strength of ZA343was89.1MPa. When injection temperature was315℃, mold temperature was60℃and the injection pressure was60MPa, the tensile strength of ZN262B was127.6MPa. |
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