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Improvements in the Structural Integrity of Resin Based Combustible Cartridge Cases (CCC) at Elevated Temperatures

Dey A., Athar J., Gogoi S., Navle P. B., Sikder A. K.

Central European Journal of Energetic Materials

2015

Vol. 12, no. 1

117--127

An advanced, solvent-less resin based Combustible Cartridge Case (CCC), designed to resolve the inherent problems of shrinkage and limited mechanical strength associated with the gelatinisation of nitrocellulose, has already been developed. The felt-moulded components contain thermoplastic polyvinyl acetate (PVAc) resin as the binder and the enhanced mechanical strength is achieved by carrying out hot compaction of dry felts at an elevated temperature (105 ± 2 °C). Presently, resin based technology is adopted for tank gun ammunition and also for the developed modular CCCs, i.e. the Modular Combustible Case (MCC) for different types of artillery gun ammunition. However, during exhaustive trials conducted with the resin based CCCs in 120 mm tank gun ammunition at three temperatures, i.e. -10, 27 and 55 °C, severe geometrical deformation was noticed when the rounds were conditioned at 55 °C for 24 h., adversely affecting the loading of rounds into the gun chamber. This was attributed to the combined effects of softening of the resin at that temperature and the load of the projectile/ shell (14.4 kg) experienced by the CCC region during conditioning of the round in the horizontal mode. In order to resolve this problem of deformation, PVAc resin was required to be modified. The PVAc resin was modified to the form of a nanocomposite. PVAc nano composite was prepared by dispersing organically modified nano clay, i.e. Cloisite 30B, into the resin before making the CCCs. The nanocomposite of PVAc resin was characterized by FTIR, DMA, softening point measurement etc. The results showed a remarkable improvement in the glass transition temperature (Tg) and in the softening temperature of the modified PVAc resin. This modified PVAc resin was used to prepare CCCs. Furthermore, these CCCs were coated with hexamethylene diisocyanate (HMDI) on the inner and the outer surfaces. The isocyanate coating becomes crosslinked in the matrix, thereby improving the softening point as well as the mechanical properties of the CCCs. These modified CCCs were repeatedly tested at 55 and 60 °C for 24 h. After testing, it was found that no deformation had taken place and the assembled rounds were easily loaded into the gun chamber. The use of the PVAc nanocomposite in the preparation of resin based CCCs, followed by isocyanate coating, is an effective means of achieving the required improvement in structural integrity of the resin CCCs at elevated temperatures.

PVAc glue as a binding agent in particleboards

Kowaluk G., Fuczek D.

Drewno : prace naukowe, doniesienia, komunikaty

2009

vol. 52, nr 182

17-24

The increasing demands concerning formaldehyde content in/emission from particleboards force search after alternative bonding agents. One of such bonding agents can be polivinyloacetate (PVAc) glue. Unfortunately its high viscosity makes it difficult to apply the glue using methods for urea-formaldehyde glues. The viscosity change as dry mass decreases can be the reason for low strength of particleboards produced with such glue. The results show that bending strength and internal bond strength of particleboards produced with the use of PVAc glue is lower than for panels produced with the use of UF resin.

Rosnące wymagania dotyczące zawartości oraz emisji formaldehydu z płyt wiórowych zmuszają do poszukiwań alternatywnych środków wiążących. Jednym z takich klejów może być klej polioctanowinylowy. Niestety jego wysoka lepkość utrudnia nanoszenie metodami stosowanymi dla klejów mocznikowo-formaldehydowych. Zmiana lepkości poprzez obniżenie zawartości suchej masy kleju może być powodem niskiej wytrzymałości płyt wiórowych wytworzonych z udziałem takiego kleju. Wyniki badań wykazały, iż wytrzymałość na zginanie, jak również wytrzymałość na rozciąganie prostopadłe płyt wytworzonych z użyciem kleju PVAc jest niższa niż dla płyt wytworzonych z użyciem żywicy UF.