Enhanced propellant performance via environmentally friendly curable surface coating

Surface coating of granular propellants is widely used in a multiplicity of propellants for small, medium and large caliber ammunition. All small caliber ball propellants exhibit burning progressivity due to application of effective deterrent coatings. Large perforated propellant grains have also begun utilizing plasticizing and impregnated deterrent coatings with the purpose of increasing charge weights for greater energy and velocity for the projectile. The deterrent coating and impregnation process utilizes volatile organic compounds(VOCs) and hazardous air pollutants(HAPs) which results in propellants that need to be forced air dried which impacts air quality. Propellants undergo temperature fluctuations during their life. Diffusion coefficients vary exponentially with variations in temperature. A small temperature increase can induce a faster migration, even over a short period of time, which can lead to large deviations in the concentration. This large concentration change in the ammunition becomes a safety or performance liability. The presence of both polymeric deterrents and nitroglycerin(NG) in the nitrocellulose matrix and organic solvents leads to higher diffusion rates. This results in continued emissions of VOCs and HAPs. Conventional polymers tend to partition within the propellant matrix. In other words,localized mixing can occur between the polymer and underlying propellant. This is due to solvent induced softening of the polymer vehicle over the propellant grain. In effect this creates a path where migration can occur. Since nitrate esters, like NG, are relatively small, it can exude to the surface and create a highly unstable and dangerous situation for the warfighter. Curable polymers do not suffer from this partitioning due to "melting" because no VOC solvents are present. They remain surface coated. The small scale characterization testing, such as closed bomb testing, small scale sensitivity, thermal stability,and chemical compatibility, will be presented. The 30 mm gun demonstration firing data at hot, cold, and ambient temperatures will also be presented.

The Influence of Poly(Vinyl Alcohol)on Oil Release Behavior of Polylactide-Based Composites Filled with Linseed Cake

In order to limit the negative impact of industry on natural environment,ecological alternatives to conventional polymers are being proposed.One of the most popular“green”polymers is polylactide,which can also be successfully applied as a matrix of composites.The application of ground linseed cake as a filler for polylactide-based composites is in line with the idea of Circular Economy,and moreover it provides a modifying effect on the polymer by increasing its crystallinity and reducing its brittleness.This effect is caused by the presence of linseed oil which can be released to the polymeric matrix in a non-controlled way.In order to control the miscibility of the oil and the polymer,we modified the filler particles with poly(vinyl alcohol)before introducing it to the polylactide.We concluded that poly(vinyl alcohol),which does not mix with oil,encapsulated the active ingredients inside the filler particles.We evaluated the mechanical properties of the composites containing 5,10,20 and 30 wt%of the filler in a static tensile stress and by means of dynamic mechanical thermal analysis.Crystallinity and thermal properties were tested using differential scanning calorimetry as well as thermogravimetric analysis.Composites’microstructure was evaluated by Scanning Electron Microscopy.It was found that modifying the oil-rich filler with poly(vinyl alcohol)helps to reduce its release to the matrix and thus limits the plasticizing effect of linseed cake.This result was in accordance with our hypothesis.