Spheroidal nitrocellulose

The key to the successful application of high performance, pourable nitrocellulose plastisols lies in a reasonably priced, high quality source of fine-particle, at least partially colloided, spheroidal nitrocellulose. Here we are speaking of particles much finer than the well-known ball powder, produced by the Olin Mathieson Chemical Co. for small arms for over 30 years (7). Actually, particles on the order of 5-50/x diameter appear to be required to assure a reasonable continuum of uniformly plasticized nitrocellulose binder in a propellant containing 45% or more of combined crystalline oxidizer and powdered metal fuel. Such a continuum of binder is necessary to assure acceptable mechanical properties and reproducible burning characteristics of the finished propellant. Preincorporation of a certain content of the water-insoluble solids within the nitrocellulose microspheres is an effective means of helping to assure this continuum of binder and alleviates the requirements for extremely small ball size. The use of a total of 45% or more of crystalline oxidizer and (generally) metal fuel is essential if the propellant is to be competitive with other modern propellants now in service. 

It is an oily substance of density (at 20 C) 1.408. On a hot plate, temperature 245-380 C, it gave a violent explosion similar to that of nitroglycerine. Below 245 C it evaporated and above 380°C took on a spheroidal shape and burned quietly. It is more sensitive to impact than nitroglycerine, and is a good solvent for nitrocellulose. 

A new description of slurry-cast propellants ( Plastisol Propellants ) has been given by Camp (44]. Fine particle spheroidal nitrocellulose is the base of the... 

Spheroidal nitrocellulose is first dispersed in a solution of plasticizers and stabilizers followed by adding metal powder (if used) and oxidizers. The temperature of mixing is maintained below 30 C to avoid an excessive gclatinization and an increase of viscosity. After forming the charge it is cured at 40 -60 C for a few days. Rubber lining with a cross-Jinked adhesive system was used to protect the outer surface of the charge. 

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