A Characterization and properties of nitrocellulose: UNIVERSAL CALIBRATION FOR GPC OF NITROCELLULOSE

Antonio Moran1, Veronica Leon1, Jesus Fernandez1, Federico Leon2, Amalio Garrido2, Miguel Angel Florez2

1Expal Propellant Systems, Javali Viejo, España

2Maxam Corp Holding, Madrid, España

 

Gel permeation chormatography has been a hot topic during the last decade between the people interested in Nitrocellulose. As a general rule and due to the imposibility to access to nitrocellulose narrow standards, the calibration curve for the GPC analysis is obtained making use of polystyrene standards. In 1967 H. Benoit and al. showed that the calibration curve Log(Mw) vs Volume obtained with a polymer standard is not a universal calibration curve  that can be used with any other polymer. However, they demostrated that making use of the hydrodinamic volume that is related with Mw by the Mark-Houwink parameters a calibration curve of the logarithm of the Hydrodinamic volume of the polymer standars versus the volume behaves like a universal calibration curve and may be used to know the Mw of other polymers.

Taking into account that the Mark-Houwink parameters for nitrocellulose in THF have been published and that the Bergerac Type Viscosity is directly related with the molecular weight of nitrocellulose, an evaluation of the potential to improve the exactness of GPC results for nitrocellulose by use of universal calibration has been done by comparing for several samples of nitrocellulose the values for the molecular weight obtained by GPC/universal calibration with the one expected by its Bergerac Type Viscosity.

A Characterization and properties of nitrocellulose: Near Infrared Spectroscopy for the Quality control of Felting Combustible Cartridge Cases: From samples to analysis
  1. Chaveroux, R&D department, EURENCO

 

Felting Combustible Cartridge Cases (CCC) contribute to performances of 155mm and 120mm artillery munitions due to the presence of energetic material as nitrocellulose in their formulation. Felting CCC are manufactured from pulps made up of Nitrocellulose, Kraft, stabilizer, resin and flocculent. At each step of the pulp manufacturing, controls of the nitrogen and nitrocellulose stabilizer contents of the pulps are unavoidable. These Quality controls take a lot of time due to preparation and analyses of samples causing a non-optimized preparation time of pulps. EURENCO R&D department investigates Near InfraRed Spectroscopy (NIRS) to determine nitrogen and nitrocellulose stabilizer contents of the Felting CCC at different steps of the production in a shorter time.

NIRS is based on study of interaction between an electromagnetic ray and the material. For this reason NIRS is very sensitive to chemical and physical properties of the sample (surface state, density…). This investigation starts with development of a new machine designed for the preparation of Felting CCC pulp reproducible samples for NIRS analysis.

The development of the quantitative calibration models for nitrogen and nitrocellulose stabilizer contents was performed and estimated by the EURENCO R&D department. This setting up shown a good correlation between nitrogen and nitrocellulose stabilizer contents determined by reference analysis (respectively Dewarda nitrogen content and gaz chromatography) and by NIRS

 

A Characterization and properties of nitrocellulose: SIZE EXCLUSION CHROMATOGRAPHY AND CORRELATION BETWEEN DEGREE OF POLYMERIZATION AND VISCOSITY TYPE BERGERAC

Nicolas. BRUN – Claude  GUILLAUME

MANUCO

 

Size exclusion chromatography has been is used a lot for nitrocellulose in the last decade. A lot of work has been done for the determination of the degree of polymerisation using different kind of detectors and also external calibration with polystyrene standard.

 

The viscosity type BERGERAC is used since 1982 and can be connected with the degree of polymerisation.

This specific viscosity type BERGERAC analysis will be detailed  and correlation between degree of polymerisation obtained by SEC and viscosity type will be presented.

A Characterization and properties of nitrocellulose: Oscillatory rheology of plasticised Nitrocellulose binder formulations – an update on results

Adam Halford

 

At the previous symposium, oscillatory rheology was presented as a dynamic mechanical assessment technique for plasticised nitrocellulose binder formulations. The method allows for the characterisation of the binders’ change in mechanical properties as a result of thermally accelerated ageing.
The gel like binder sheets have now completed their respective isothermal ageing trials and further rheological data has been obtained. The deformation techniques performed on the binders include stress and temperature sweeps and creep ringing. Different stabilisers have been utilised within the formulations and the extent of the ageing effects varied depending on which stabiliser was employed.
Also, repetition of previous experimentation has been carried out to determine whether storing plasticised nitrocellulose binders at sub-ambient temperatures for extended periods of time is a viable method to maintain mechanical properties.
©

A Characterization and properties of nitrocellulose: Identifying differences between wood- and cotton-based cellulose and its nitrated product: an analytical approach

Monique van Hulst and Yvonne Vogels
TNO, Defense, Safety and Security, Department Energetic Materials, The Netherlands
e-mail: monique.vanhulst@tno.nl

 

When working with a biobased product, batch-to-batch properties of the material may vary
widely, depending on their origin. These dissimilarities can result in products with different
properties. This is also the case for the production of nitrocellulose. The physicochemical
properties of the cellulose and its influence on the final nitrocellulose product are not fully
understood yet.
For this reason the differences between cellulose originating from different sources, have
been investigated using a range of analytical techniques in an attempt to obtain more insight
how and if certain physicochemical properties affect the nitration of these cellulose types to
produce nitrocellulose.
Four cotton-based and three wood-based cellulose samples have been used for this
investigation. These seven samples have been analyzed before and after nitration using the
following techniques: X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM),
Differential Scanning Calorimetry (DSC), Size-Exclusion Chromatography (SEC) and
Elemental Analyses (EA). This presentation will discuss some of the findings resulting from
this study.

A Characterization and properties of nitrocellulose: Intoduction of the CHN elemental analysis of Nitrocellulose at AWE

Nicola Barnett

 

AWE has recently had a brand new CHN elemental analyser installed and commissioned. Method development is now underway to accurately and consistently measure the nitrogen content of nitrocellulose samples. This will include analysis of historical nitrocellulose and nitrocellulose formulations so we can better understand the connection between nitrogen content and behaviour/chemical properties. A short presentation will be given on the progress of this method development and any results achieved to encourage discussion and input from the wider community.

A Characterization and properties of nitrocellulose: An update on the progress towards reliable nitrocellulose molecular mass distribution at AWE

Nicola Barnett and Dr Emma Stubbs

 

AWE presented our initial progress at the 7th NC Symposium, since then we have:

 

  • Finished the method development and validated this triple detector method
  • Analysed historical formulations for comparisons to old data and new baseline values
  • Started to investigate the shoulder peak present in many samples analysed – this investigation is currently in progress

 

A presentation to give an overview of previous requirements, the new method and to look at the analysis this new method has enabled us to perform as well as looking at the progress of the investigation into the shoulder peak present in some samples.

A Characterization and properties of nitrocellulose: STATUS OF NATO-STANDARD FOR NITROCELLULOSE TESTING (STANAG/AOP 4178)

Beat Vogelsanger 1, Michael Ramin 1, Marc Müller 1, Patrick Folly 2  

1 NITROCHEMIE WIMMIS AG, Switzerland

2 Federal Department of Defence, armasuisse, Thun, Switzerland

 

The two most widely used compilations of nitrocellulose (NC) testing procedures are NATO Standard STANAG 4178 ‘Test Procedures for Assessing the Quality of Nitrocellulose’ and US Specification MIL-DTL-244 ‘Detail Specification Nitrocellulose’. The actually valid documents are STANAG 4178 Ed. 2 (last revised in 2009; promulgated 2013), and MIL-DTL-244C (implemented in 2014), respectively.

 

STANAG 4178 is currently under revision, leading to AOP-4178 Ed. 3. Changes introduced in this document are based, amongst others, on the outcome of an international survey (conducted in spring 2016 by armasuisse) and an international workshop on nitrocellulose testing (hold in June 2016 in Montreal, Canada). Main changes are:

  • Document has been fully rewritten, many parts have been rephrased / clarified, redundant information has been removed.
  • The few still existing differences between STANAG 4178 Ed. 2 and MIL-DTL-244C have been eliminated. This means that the 16 test procedures that are contained both in STANAG/AOP-4178 and MIL-DTL-244C are now identical in both documents.
  • Nitrogen Content of nitrocellulose: FAS/FS Titration ­Method has been improved; new NIR-Method has been included; methods that are no longer in use have been omitted.
  • 5°C Abel Heat Test and Grit Test have been omitted.
  • An alternative Viscosity Test method which is also suitable for low viscosity NC grades has been included in addition to the MIL Viscosity Test.
  • Method for Fibre Length Distribution has been considerably improved.
  • For Fiberization Quality / Agglomerates, the unsatisfactory method based on wet sieving has been replaced by the more robust / sensitive elutriation method.
  • If test methods have been found to be only suitable for comparative testing, this has been clearly stated (e.g. for Molecular Mass Distribution and Fibre Length Distribution).

 

The final draft of AOP-4178 Ed. 3 is currently under discussion within NATO and should be submitted for ratification soon.

B Safety, stability and ageing of NC and NC based material: Life Assessment of Nitrocellulose-Based Energetic Materials: LOVA, Flare and CCC

M. R. Andrews†, C. Collet†, R. Millar†*, E. Schultz‡
†Munitions Safety Information Analysis Center (MSIAC) NATO Headquarters, B 1550, BZ S040, B-1110, Brussels, BEL
*MSIAC Stokes Fellow, DOSG, MoD, UK
‡Eurenco, FRA; formally of MSIAC

 

Nitrocellulose (NC), with its variable energetic content, solubility with energetic and non-energetic plasticisers, and formation of structural materials, makes it a very versatile material. This flexibility has allowed nitrocellulose to be used in multiple products within the energetics community, from propellants, to ignitor compositions, combustible cartridge cases to flares.
Known stability issues of nitrocellulose and nitrate ester plasticised propellants have led, through scientific understanding, to the development of numerous standards and surveillance programs. The main international standard for propellant stability characterisation is AOP-48 Ed 2 (2008). This work ensures the safety and suitability for service for these propellants. However, AOP-48 Ed 2 use is limited to NC containing single base (SB), double base (DB), triple base (TB) propellants only and to those with a minimum stabiliser content.
The gaps in the guidance currently provided by AOP-48 need to be discussed and addressed. This is the case for several low content nitrocellulose-based materials, such as Low Vulnerability Ammunition (LOVA) and some Infrared Decoy Flares, which have stabiliser content below the AOP-48 requirement.
Another area that requires development of guidance for life assessment is migration of energetic plasticisers for non-standard propellant materials. For example, Combustible Cartridge Cases (CCC) can be filled with SB, DB or TB propellant grains. Migration of plasticisers from the DB grains into the CCC could lead to a reduction in the life of the cartridge.
This paper will review the use of propellant-based AOPs, STANAGs and other techniques for determining life assessment of these nitrocellulose-based energetic materials. It will also highlight potential safety issues and propose methodology for capturing the required safety information.

B Safety, stability and ageing of NC and NC based material: Evaluation of a ‘stabiliser cocktail’ for a plasticised nitrocellulose explosive binder system
  1. Hope, S. Connors, P. Jenkins, D. Lewis

An accelerated aging trial was conducted to investigate the use of a ‘stabiliser cocktail’ in stabilising Nitrocellulose (NC) containing Polymer Bonded Explosives (PBX). A mixture of nitrocellulose and energetic nitro plasticisers can be used as a polymer matrix, when mixed with a crystalline explosive filler to form a PBX. The mechanical properties of these PBXs are directly related to the NC molecular mass and can therefore be adversely affected by NC degradation with age.

NC is thermally unstable and homolytic cleavage of the weak CO-NO2 bond (Figure 1.) generates free radical nitrogen oxides (NOχ•). These NOχ• radicals can promote further thermolysis degradation resulting in chain scission of the NC backbone. This form of degradation is inevitable due to the inherent weakness of the CO-NO2 bonds. Further alternative degradation pathways including hydrolysis (Figure 2.) and oxidation (Figure 3.) can also be triggered if NC is exposed to initiating reagents.

 

 

To slow the rate of NC degradation by limiting autocatalytic reactions and increase the life of the PBXs, a stabiliser, typically a NOχ• scavenger, is added to a binder system. However, by establishing these known degradation pathways of thermolysis, hydrolysis and oxidation this investigation looks at the potential of using a ‘stabiliser cocktail’ as an alternative means to single stabiliser binder compositions. The ‘stabiliser cocktail’ is comprised of specific stabilisers to target specific degradation reactions.

The study used sheets of binder, manufactured without the explosive filler, at multiple temperatures for extended periods.  In order to examine the stability of the binder, the molecular weight of NC was analysed by gel permeation chromatography (GPC) and the stabiliser concentration was also monitored by high performance liquid chromatography (HPLC).

Ageing the samples at multiple temperatures allows use of Arrhenius kinetics to model and assess the stabilisers individually and as a collective ‘cocktail’. Further, by ageing at different humidity levels and levels of headspace oxygen, these specific degradation pathways can be isolated. The extent to which the stabilisers were effective under these different environments can therefore be determined to assess if a ‘stabiliser cocktail’ is a step forwards in increasing the lifetime of NC containing PBXs and propellants.

© British Crown Owned Copyright 2017/AWE

B Safety, stability and ageing of NC and NC based material: STABILITY TESTING OF NITROCELLULOSE

Michael Ramin, Beat Vogelsanger, Marc Müller, Beate Pausch   

NITROCHEMIE WIMMIS AG, Switzerland

 

Stability testing of nitrocellulose is essential in order to avoid or at least to reduce safety-relevant incidents during storage and use of this energetic compound. According to NATO Standard STANAG/AOP-4178, stability of nitrocellulose can be tested by any of the three following methods: 132°C Bergmann-Junk Test, 132°C Bergmann-Junk-Siebert Test, or 134.5°C Heat Test (‘Methyl Violet Test’), respectively.

 

In the first part of the presentation, advantages and shortcomings of these three tests are discussed, and results of comparative testing are presented. For that purpose, several NC samples were tested with 132°C Bergmann-Junk (BJ), 132°C Bergmann-Junk-Siebert (BJS) and 134.5°C Heat Test (MV; 1 min resolution). It was found that the results of the three test methods correlated well with each other. In particular, all test methods plausibly confirmed increasing stability of the samples of the same nitrocellulose batch that were taken consecutively of the ongoing stabilisation process. Furthermore it turned out that the 132°C BJ Test is somewhat stricter than 132°C BJS and 134.5°C MV Tests.

 

First results of a study using modern spectroscopy detection methods aiming to replace the conventional tests methods mentioned above will be presented in the second part of the presentation.

B Safety, stability and ageing of NC and NC based material: “8.12”Tianjin Explosion Accident and Industrial NC

Sichuan Nitrocell Corp. (SNC)
P.R. of China
Zhang Renxu, Peng Huan

 

0 Introduction of “8.12” Tianjin Explosion

Tianjin explosion incident in China (on Aug. 12, 2015) has been condidered as
one of the largest chemical explosion in history in China. Accordding to the
State Council investigation team, the direct cause of the accident is due to
the loss of nitrocellulose wetting agent, the NC is partially drying under high
temperature, thus the exothermic accelerating decomposition finally caused
spontaneous combustion. Further more, nitrocellulose in the adjacent
containers and other hazardous chemicals caught fire and led to long time
and large area burn, which finally caused the ammonium nitrate and other
hazardous chemicals in the area getting explosion.

1 Accident Analysis

How has Nitrocellulose been Identified as the initial ignition material:
◆Man-made destruction or lightning strikes or external sources of ignition?
◆The fire position is determined by monitoring the video
◆ Screening fire source by physical&chemical properties analysis,
experimental verification, video comparison, on-site evidence analysis and
other methods, one by one
Causes of Spontaneous Combustion of Nitrocellulose:
◆The loss of wetting agents lead partly drying
◆Under the effect of days of high temperature , accelerating decomposition
exothermic heat to spontaneous combustion
In fact, we all believe that the real cause is unstable of the product itself

2 RESEARCH ON COMPARISON OF Bergman-Junk test and Abel test

In order to gurrantee accuracy of stability test, WONIPA Executive Committee
proposes an implementation of the Bergman-Junk stability test method by
all the WONIPA member companies, taking place of Abel test to do industrial
NC stability analysis.
For different grades of industrial NC and NC chips, we use Bergman-Junk test
to do stability test, then compare with Abel test results.
The research includes:
◆Sample pretreatmen
◆The loading height influence on B-J test
◆Comparison of titration on B-J test
Thus we get the result of comparison of B-J test and Abel test.

3 THE POSSIBILITY OF IMPROVING Abel Test

To improve the characterization of the Abel test
Qualitative→quantitative
Judgement by the human eye→Judgement by Instrument
By Gas detection tube?/ resistance change?

4 FURTHER EFFORTS NEED TO BE DONE

As a self-decomposing compound, further research on the stability of
Nitrocellulose needs to be done, aiming to increasing the safty of NC’s
storage, transportation and use.

B Safety, stability and ageing of NC and NC based material: Nitrogelatin: Making a Process Safer Using a ‘Less Safe’ Material

Bob Wall & Mark Bradley, Roxel UK

 

Roxel UK is the chief UK manufacturer of solid rocket propellant. The primary products are rocket motors made from either single (NC), double (NC & NG) or triple base (NC, NG & nitramines) powders which give low signature, minimum smoke propellants with good insensitive munitions (IM) properties.

 

Since 1990 Roxel UK has manufactured double base solid rocket propellant using NC/NG ‘paste’ as the principal energetic ingredient. This NC/NG paste is manufactured on site by Roxel UK and dried before use.  Historically dry paste is used because 1) Everyone connected with UK Cast Double Base (CDB) propellant manufacture had used it, 2) Roxel UK and the wider industry was not aware of any viable alternatives, and 3) Casting powder containing solely NC was insufficiently energetic to meet customer needs. However from a safety standpoint, it was always suspected that if an incident was to occur it would be serious, especially given the labour intensive nature of drying NC/NG paste and the subsequent exposure time of the operatives.

 

In 2010 Roxel UK instigated a programme to formally assess the burning response of dry NC/NG paste to a variety of stimuli, especially to heat and electrostatic discharge. The results of this programme increased the impetus to find a replacement material and/or an alternative manufacturing process.

 

In 2012 Roxel UK became aware of the existence of a material known as nitrogelatin (NGel). Nitrogelatin is similar to the blasting explosive gelignite, having NG adsorbed on NC with ethanol also included in the matrix. Nitrogelatin is made up from 15% NC, 80% NG and 5% ethanol. Therefore nitrogelatin can be considered an NC/NG paste with a lower NC content when compared with those already used in propellant manufacture at Roxel UK, except having a different physical form. Nitrogelatin is both qualified for use in gun propellant manufacture and available in the same NC grades currently qualified for rocket propellant, lowering risk for eventual in-service use.

 

Nitrogelatin offers Roxel UK a number of advantages over NC/NG paste including improved handling, reduced number of processes and operator exposure, reduced energy use, consistency, burning response and operator health & safety. However, as NC/NG paste is considered to be a HT3 material and nitrogelatin is a HT1 material, this presents an unusual problem – proposing to make a process safer by introducing a theoretically more hazardous material.

 

Subsequent material trials performed at Roxel UK and at external testing facilities have shown that whilst ‘officially’ more hazardous, nitrogelatin has so far been demonstrated to be safer to use and handle in double base solid rocket propellant manufacture. It has been shown that the actual physical form of the material makes a significant difference to its burning response. Subsequently, small-scale propellant manufacture has been successfully demonstrated and production scale-up trials, including final propellant properties, are now underway. If these trials are successful, it is anticipated that nitrogelatin will replace NC/NG paste in future products.

B Safety, stability and ageing of NC and NC based material: Sharing Safety Lessons Learned From Experience

Mark Hardman Managing Director

Roxel (UK Rocket Motors) Limited

 

On the morning of Friday, 16th November 2012 at approximately 8.15 a.m. at Roxel (UK Rocket Motors) Limited Summerfield Site, a Cast Double Base (CDB) Charge was being visually examined, using a fibre optic borescope, when it accidentally ignited.  This resulted in a fire within the building involving approximately 5 kg of propellant.  Three people were in the building at the time and fortunately nobody was injured and nobody outside of the building was put at risk.

 

The Company’s own independent investigation concluded that it fell short of its own standards and Roxel pleaded guilty to two offences relating to the potential risk of injury to the three people and a third offence under COMAH.

 

A number of key learning points resulted from the incident relating to Communications; Process & infrastructure; and the methodology for Fire and Explosive Risk Assessments (FERAs).  These and a number of associated topics will be covered by this paper.

 

B Safety, stability and ageing of NC and NC based material: Chemiluminescence: Investigating the thermo-chemical decomposition mechanism of nitrocellulose

M Parker, N Mai, I Wallace and P P Gill

 

Chemiluminescence is an extremely sensitive technique for the detection of NOx gas. Many conventional explosives contain nitro or nitrate ester groups that on decomposition evolve oxides of nitrogen. The rate of evolution of these gases can be used as a means of assessing the rate of decomposition of these explosives.

A number of researchers have used chemiluminescence analysis to measure low temperature decomposition of explosives and their constituents. An advantage of this technique is its capability to measure parts per billion levels of NO and NO2 at temperatures similar to those encountered by explosives in service. The technique has been successfully used to determine the temperature dependence of the decomposition of nitrocellulose (NC) and it has been used to establish the activation energy for the decomposition mechanisms (thermolysis and hydrolysis) of NC.

Operating in a continuous swept mode the technique can rapidly investigate the intrinsic decomposition chemistry of NC under a variety of conditions (humidity and temperature).  Switching to a closed loop experiment the secondary ‘auto catalytic’ decomposition chemistry of NC can be studied.

This paper describes the investigation of the effect of humidity on the NC degradation in real-time at conditions similar to those experienced in operational and storage conditions.  We also report a rigorous investigation of the robustness of the Chemiluminescence technique to a variety of experimental factors such as gas flow, sample geometry.

B Safety, stability and ageing of NC and NC based material: Study of Nitrocellulose Self-ignition Temperature

Petra Loudová, Jiří Schejbal, Jaroslav Štěpán, Oldřich Večerek

SYNTHESIA, a. s., Pardubice, Czech Republic

 

Testing of nitrocellulose (NC) deflagration temperature (or NC self-ignition temperature) belongs to the family of tests used for verifying proper NC stabilization. The method is described in STANAG 4491 or in ADR (European Agreement concerning the International Carriage of Dangerous Goods by Road). In this method, the nitrocellulose sample is heated in a test tube immersed in metal bath at a rate of 5°C/min, from 100°C until self-ignition occurs. As soon as the NC self-ignites, the corresponding metal bath temperature is recorded as NC sample deflagration temperature.

The above mentioned method with 5°C/min temperature gradient is useful for fast verification of achieved NC stabilization level and typical results of properly stabilized NC are above 180°C. But for particular NC type and same testing instrument, the self-ignition typically occurs within ± 1°C, even for different lots (and therefore different stability results). Such a narrow temperature interval of results is not sufficient for more detailed study.

In presented work, the method was modified using slower temperature gradients and even constant temperature levels. Several hundred samples of different NC grades and types were tested by these modified methods. Obtained results are compared to conventional stability tests (Bergman-Junk 132°C heat test). Different impacts, like temperature stability, NC nitrogen content or sample origin and their possible influences to the results are discussed. Considering these influences, the method does not represent a suitable alternative to commonly used stability tests, in industrial environment of NC production plant.

 

C Synthesis processing of NC and preparation processing of NC based material: InFuse™ Nitrocellulose: Production, Propellant, and Potential

Milca Fils-Aime, Douglas Messner, Matt Ridgley, Stephen Velarde

Orbital ATK/New River Energetics, Radford Army Ammunition Plant, Radford, VA, USA

 

Orbital ATK has developed a new type of nitrocellulose, termed InFuse™, that has several unique properties and potential uses as an alternative to traditional wood pulp or cotton based nitrocellulose. The early novelty of InFuse™ NC was its production from pre-shaped, commercially available celluloses that could ideally reduce much of the labor burden associated with manufacturing conventional shaped (spherical, cylindrical) propellant. While exhibiting many of the same properties as conventional NC, InFuse™ NC possesses many distinctive attributes such as:  increased solubility in common solvents, improved response to small scale initiation stimuli, significantly higher bulk density, and more energy per unit mass. The presentation will cover pilot scale production, characterization, propellant development, and other potential uses for InFuse™ nitrocellulose.

C Synthesis processing of NC and preparation processing of NC based material: A Universal Kinetic Model for the Nitration of Cellulose Fibers in Mixed Acids

Authors:

Presenter

Francis Sullivan1

Coauthors

Laurent Simon2, Nikolaos Ioannidis3, Subhash Patel3, Zohar Ophir4, Costas Gogos2, Michael Jaffe4, Shakeel Tirmizi4, Peter Bonnett1, and Philip Abbate1

 1US Army Armament Research, Development and Engineering Center, Picatinny Arsenal, NJ 07806, USA

2Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering, New Jersey Institute of Technology, University Heights, Newark NJ 07102, USA

3Polymer Processing Institute, New Jersey Institute of Technology, University Heights, Newark NJ 07102, USA

4 New Jersey Innovation Institute at New Jersey Institute of Technology, University Heights, Newark NJ 07102, USA

 

A model has been developed to describe the reaction kinetics of natural cellulose fibers in mixtures of nitric acid, sulfuric acid, and water during the production of highly nitrated nitrocellulose.  Nitration experiments were conducted using cellulose fibers obtained from cotton linters and wood pulp fibers derived from a variety of tree species and pulping processes to provide insight into factors affecting the rate and extent of reaction for the nitration of cellulose in mixed acids.  This work provided considerable insight into the mechanism of the chemical reaction and demonstrated that fiber properties alone do not play a significant role in the reaction kinetics or extent of reaction in the range of acid mixtures commonly used in industrial scale nitrocellulose production.  A semi-empirical kinetic model describing the conversion of cellulose to nitrocellulose was developed, and this model agrees closely with experimental results over the entire range of temperatures, fiber types, and reaction times studied.  The finding that this kinetic behavior is independent of fiber properties is particularly important because it implies that the range of cellulose fibers that is suitable for industrial scale nitrocellulose production may be much broader than the limited number of cellulose sources that have traditionally been used.

C Synthesis processing of NC and preparation processing of NC based material: Review of the fibre structure of cotton and wood cellulose/nitrocellulose and influence on nitration and solvent reactivity

Mario Paquet

General Dynamics Ordnance and Tactical Systems-Canada Valleyfield, Canada

 

Structural biomaterials like fibrous cellulose have evolved naturally and are very well adapted to their structural roles by using simultaneously a series of different structures to ensure mechanical strength.   The geometry of these structures has significant impact on the material mechanical properties and can significantly increase the energy it can absorb before mechanical failure.

 

Fibrous cellulose preparation/nitration and fibrous nitrocellulose processing modifies the material structure at several levels in different manners.  Preparation of propellant extrudable paste using gelatinization and paste processing can also significantly alter the multi-layered structure by retaining, eliminating, altering or reshaping it in ways which can affect among other things, the combustion and mechanical resilience of the final propellant and its ability to retain over time these two important properties.

 

This presentation is a summary conceptual review of the fibre structure of cotton and wood cellulose and nitrocellulose, how it is formed and the influence this structure may have on the response of fibrous cellulose and nitrocellulose to nitration and solvent reactivity.

 

 

C Synthesis processing of NC and preparation processing of NC based materia: New raw materials for the production of cellulose nitrates

Lauri Valtola R&D Manager

Nammo Vihtavuori Oy., FI-41330 Vihtavuori, Finland

 

 

Nammo Vihtavuori is focused on manufacturing high-end gunpowder products for a demanding customer sector (competitions, shooters, demanding enthusiasts, hunters, specialized organizations and public authorities). In order to ensure the highest quality, Vihtavuori gunpowder factory makes a very large part of the required stages of the products and raw materials, unlike most of the gunpowder manufacturers themselves.

The scope of this study was to bring new and never before discussed ideas to the table regarding the development and production of next generation high-end gunpowder products. This project focused on vegetable-based celluloses, specifically cellulose fibres extracted from vegetable cells called parenchyma cells. Parenchymal cellulose is highly sustainable and cost-effective alternative for wood- or cotton based cellulose. Another aspect is the strategic importance of a readily available raw material. A critical shift from wood and cotton based raw materials to food industry waste streams will drastically lower the cost of the cellulose products.

Laboratory scale nitration tests were performed and the results were compared with the wood- or cotton based raw materials.

 

Nammo Vihtavuori is focused on manufacturing high-end gunpowder products for a demanding customer sector (competitions, shooters, demanding enthusiasts, hunters, specialized organizations and public authorities). In order to ensure the highest quality, Vihtavuori gunpowder factory makes a very large part of the required stages of the products and raw materials, unlike most of the gunpowder manufacturers themselves.

The scope of this study was to bring new and never before discussed ideas to the table regarding the development and production of next generation high-end gunpowder products. This project focused on vegetable-based celluloses, specifically cellulose fibres extracted from vegetable cells called parenchyma cells. Parenchymal cellulose is highly sustainable and cost-effective alternative for wood- or cotton based cellulose. Another aspect is the strategic importance of a readily available raw material. A critical shift from wood and cotton based raw materials to food industry waste streams will drastically lower the cost of the cellulose products.

Laboratory scale nitration tests were performed and the results were compared with the wood- or cotton based raw materials.

C Synthesis processing of NC and preparation processing of NC based materia: Manufacturing and Evaluation of Kraft AFP-001 Propellant

Lucas R. Lopez, Daniel Lee

U.S. Army ARDEC

Picatinny Arsenal, NJ 07806

 

BAE Systems made several lots of AFP-001 propellant with Kraft nitrocellulose (NC).  The team used chemical and physical analyses and ballisticperformance to identify any differences between baseline and Kraft AF001.Transition of AFP-001 propellant to Kraft NC has proven difficult.  Kraft AF001 burnsfaster than the sulfite baseline.  As result it does not meeting the requirements of the specifications.  Numerous changes in grain geometry and manufacturing parameters have been implemented to offset the burn rate increase. This paper describes the manufacturing and evaluation of the Kraft AF001 propellant.

D Effect of NC on performance propellant and explosives: NC from kraft cellulose

Several lots of Grade A and Grade B NC has been made with dissolving wood pulps from two CONUS sulfate pulp millsat Radford Army Ammunition Plant (RFAAP).  Lots meeting the requirements of MIL-DTL-244C were used to produce four propellants that were subsequently characterized and ballistically tested. Propellants manufactured were the single base propellants M1MP used in the M67 Propelling Charge for 105mm, and the AFP-001 for the 30mm GAU-8/A ammunition, the double base RPD596 used in the tank M865 cartridge, and Ball Powder® WC868 used in the small caliber ammo 5.56 mm cartridge. Characterization tests included vacuum thermal stability testing, differential scanning calorimetry, accelerated long term aging, friction sensitivity, and impact sensitivity. Propellant performance was assessed in accordance with the corresponding specifications, including ballistic assessments. All lab and ballistic assessments were conducted with standard production propellants as controls.

 

This project has demonstrated that acceptable lots of NC can be made with sulfate dissolving wood pulp. Propellants made with sulfate wood pulp-based NC met their respective requirement of the specifications. This project has diminished the risks associated with transitioning current sulfite dissolving wood pulp to a CONUS sulfate source for the production of high quality nitrocellulose at RFAAP.

D Effect of NC on performance propellant and explosives: Propellant qualification An overview of propellant qualification strategy.

Nigel Rutter

UK MoD DE&S DOSG

 

A presentation providing a brief overview of recent UK reviews of propellant qualification methods for an update to AOP 7 Chapter 10 UK National section.

 

Given the ever-changing world of material obsolescence what tests should we employ to replace those deemed obsolete? The presentation will examine analytical tests currently employed, questioning their validity for our current needs and the reasonswhy some older methods are being consigned to the history books.Recent research work will be presented examining current propellant test methods.

 

Over recent years the UK has undertaken several Nitrocellulose research and propellant qualification programmes determining the ideal physical and chemical criteria fornitrocellulose and propellant manufacture.A definitive answer for Nitrocellulose and certain propellant types has yet to be fully established.

 

Given this gap in knowledge how do we approach the future wherequalification protocols and test methods for new propellants formulations are needed? Is it possible to use the older protocols and methodologygiven the material differences in new propellant formulations? Should we be looking for new techniques? What analysis and qualification criteria should we apply in the future

D Effect of NC on performance propellant and explosives: Compatibility and ballistic properties of graphene oxide modified nitrate esters for novel propellant formulation

P Yahya; M Moniruzzaman*
; P. P. Gill
Centre for Defence Chemistry, Cranfield University, Defence Academy of the UK
Shrivenham, SN6 8LA, United Kingdom
Email: kharisma.k.yahya@cranfield.ac.uk

 

Improvement of ballistic properties, stability and survivability of conventional propellants is of
great interest to the defence industries. Graphene is one of the latest nanomaterials that has
attracted tremendous attention within the energetic community for improving heat of
combustion, stability, burning rate, ignition properties and mechanical properties of energetic
materials. Diethylene glycol dinitrate (DEGDN) is a liquid nitrate ester with a lower
sensitivity than nitroglycerine and is being used in double base propellant formulation (JA2
propellant). The main disadvantages of DEGDN are its vulnerability to migration in the
propellants and susceptibility to decomposition. Additionally, the slow decomposition of
nitrocellulose (NC) is a major drawback in conventional propellants. Improving stability,
ballistic properties, survivability and mechanical properties of a double based propellant
using graphene is the key focus of this presentation. Prior to developing a suitable propellant
formulation it is important to investigate the compatibility, energy performance, stability and
migration properties of DEGDN in graphene modified NC.
We report here the stability, heat of combustion and migration behaviour of Graphene oxide
(GO) modified DEGDN and NC/DEGDN compositions. DEGDN was synthesized by
conventional nitration process of diethylene glycol. The effect of dispersion of three
graphene compositions (<1% w/w) on the enthalpy of combustion and migration properties
of DEGDN will be assessed using differential scanning calorimetry (DSC) and
thermogravimetric (TGA) analysis. The burning property of GO modified DEGDN/NC
composition was assessed at ambient conditions using a high speed camera and cross
compared with unmodified composition. The stability of GO dispersed DEGDN and NC after
aging at 65ºC is established using NMR and Raman spectroscopy. The results offer better
understanding of processability, compatibility, ballistic properties, performance and
survivability of a GO modified novel double based propellant.

D Effect of NC on performance propellant and explosives: Characterization of ageing of double base propellants by not often used measurement properties

Manfred A. Bohn

Fraunhofer ICT, D-76318 Pfinztal, Germany

e-mail: Manfred.Bohn@ict.fraunhofer.de

 

Nitrocellulose (NC) based double base (db) rocket propellants (RP) are further on in use because of adaptable properties in burning rate and their low signature. The slow ageing during storage is often seen as a major disadvantage. However, this is not the case in reality. If properly manufactured with carefully selected ingredients, in-service times up to 20 years at normal thermal loads (10 to 30°C) can be obtained easily. To secure the in-service time handling of db RP motors, one should use the proven ageing indicators: decrease of primary (added at manufacture) stabilizer, decrease of molar mass of NC, heat generation rate determined by heat flow microcalorimetry (HFMC). They are used to determine the state of chemical ageing and to predict residual in-service time. Further ageing indicators are tensile strength at break, mass loss and gas generation. DMA (dynamic mechanical analysis) can answer special questions. On the base of these methods, the adapted concept for the health monitoring of db RP can be established and implemented.

 

In this paper properties are used, which are not often applied, to characterize several db RP. The properties are: gas generation, mass loss, molar mass decrease and dynamic mechanical analysis. The intended aspect is, to find out differences in ageing behaviour of differently stabilized db RP.

 

Finally, some remarks on the evaluation of so-called ‘green’ stabilizers should help to get suitable assessment of them.

 

 

Keywords

Double base propellants, stabilizer decrease, molar mass degradation, heat generation rate, DMA, gas generation

D Effect of NC on performance propellant and explosives: Proposed Upgrading of Kraft Cellulose Specification

Lucas R. Lopez, Kristy Klein, Mo Elalem

U.S. Army ARDEC

Picatinny Arsenal, NJ 07806

Is there a need for a Kraft (sulfate) cellulose specification?  In our opinion, the answer is yes.  The reason is simple.  All celluloses are not equal and their range of property variations may have significant effects on the resulting properties of the NC and subsequent propellants produced with them. In order to ensure uniformity of products generated from cellulose sources a specification delineating acceptable cellulose properties is necessary.

The military specification MIL-C-20330A for Kraft wood pulp, which was written in 1962, addresses cellulose purity (alpha cellulose, alkali soluble matter and pentosane), and contaminants (ether extractive matter, ash and silica and lignin), but doesn’t include other known properties that may affect nitration, propellant manufacturing and performance.

This White Paper identifies and provides an explanation for each of the desired chemical and physical properties that will ensure the quality and consistency of cellulose used in the manufacturing of NC including the basis for the recommended upper and lower limits.  It concludes by providing a detailed purchase specification for Kraft cellulose that will serve as the basis for the revision of MIL-C-20330A specifications.