2.2.4. Efectos jurídicos en las victimas y en las sentencias del delito de abuso
2.2.4.1 Efectos jurídicos en la víctima de abuso sexual
An explosion, deflagration or other reactivity hazard involves conversion of stored chemical energy of the component into mechanical or heat energy, and it is the uncontrolled release of this stored energy that causes the damage in a reactive chemical incident, volitional in the case of high energetic materials. The reactivity of a substance is normally assessed by performing calorimetric measurements.50 Information about the amount of energy released and the rate of energy released for a energetic material can be obtained by performing calorimetric tests. There are several various calorimetric measurements possible. Moreover decomposition experiments are also important.
TGA:
The thermogravimetric Analysis (TGA) provides a graph of mass loss vs. temperature over a specified temperature range (up to 2000 °C). This analytical technique is widely used in polymer science, inorganic chemistry, fuel science, and geology to measure the loss of volatile components or thermal stability of a sample and can also be used for the investigation of explosives. The experiments are usually run with a temperature ramp of 5 or 10 °C min-1 and can be carried out in inert atmospheres, such as nitrogen, to study thermal stability or volatility,
characteristic of a material and, where the losses are in discrete steps, the TGA experiment can offer quantitative data on the course of a decomposition. The TGA also can be run in an isothermal mode, where the rate of weight loss at a fixed temperature is measured. This type of experiment can be used to predict loss rates of volatiles or decomposition rates for materials.
The following procedure describes a general TGA experiment, measurements deviating from this procedure will be stated: The samples were subjected to TGA analysis in a nitrogen atmosphere in open Al2O3 crucibles (sample weight ~ 1 − 5 mg) at a heating rate of 5 °C min-1
with a thermogravimetric analyzer (Setaram DTA−TGA 92)51 in the temperature range from 30°C − 750 °C. For the removal of moisture, the samples were dried in vacuo (if possible) for 24 h at 40°C.
DSC:
A differential scanning calorimetry (DSC) can provide an overall indication of exothermic activity of the composition activity of the compound being tested and can help to assess potential reactive hazards. In a DSC, a sample and a reference are subjected to a continuously increasing temperature, and heat is added to the reference to maintain it at the temperature as the sample. This added heat compensates for the heat lost or gained as a consequence of an overall endothermic or exothermic reaction. When the heat generation (Watts) in the sample exceeds a particular value, the heat supply to the sample is cut-off, and this additional heat gain is attributed to exothermic activity within the sample. This cut-off value depends on the sensitivity of the particular instrument. In the case of an exothermic (endothermic) reaction, a peak is observed in a DSC thermograph. A base line is constructed from the initial heating mode, and another line is drawn to coincide with the initial rise due to the exotherm (endotherm). The temperature at the intersection of the two lines is called the onset temperature and corresponds to a detectable level of heat due to a chemical reaction. The energy released (-∆H) during the process is calculated as the area under the heat-supplied (Watts) and time curve. DSC is a popular screening tool because it is safe, since it involves a small amount of sample (for energetic materials less than 1mg is appropriate).
The kinetics of exothermic reactions are important in assessing the potential of materials and systems for thermal explosion. These parameters are for example accessible from the onset
detected onset temperature is thus a measure of the reaction kinetics. There is considerable argument about such interpretation52, and therefore we decided to use the Standard Test Method for Arrhenius Kinetic Constants for Thermally Unstable Materials from American Society for Testing and Materials (ASTM) according to the ASTM protocol E 698 – 99 to estimate parameters like activation energy (Ea).53 The theoretical background of this procedure is based
on the work of Ozawa54 and Kissinger55.
Autocatalytic and nth-order kinetics are the main features of decomposition reactions. They can be expressed as follows: For nth order kinetics,
k n dt d ) 1 ( α α = − (1)
where α, the extent of decomposition, is defined as α = ∆Ht/∆HTotal, were ∆Ht and ∆HTotal are
the enthalpy of the decomposition reaction at time t and the enthalpy of the decomposition reaction at the end of the decomposition, respectively; they can be determined from DSC thermograms (Peak maxima). The rate constant (k) can be expressed as
k=Ae−Ea/RT (2) where A is the frequency factor. Then,
RT E A dt d k a n = − − = ln ) 1 ( ) / ( ln ln α α . (3)
When the order of this reaction is properly assumed, a plot of ln k versus 1/T provides A and Ea. Kissinger55 proposed that
Eaβ(RTp2)=Ae−Ea/RTp (4)
where β = dT/dt is the heating rate. By taking the logarithm of Eq. (4), we obtain the Kissinger equation: ) / )( / 1 ( ln ) / ln( 2 T E R E AR T p a a p = + − β (5)
From a plot of ln( / 2)
p T
β
− versus 1/Tp, where Tpis the peak temperature, and fitting to a straight line, the activation energy Ea can be calculated from the slope. The general equation for
the reaction rate under isothermal conditions has been written as: f ATne Ea RT
dt
dα = (α) − / (6)
Under non-isothermal condition, at a constant heating rate β = dT/dt, an explicit temporal dependence of Eq. (6) can be derived, and together with Doyle’s approximation56 the linear equation of Ozawa-Flynn-Wall54 can be obtained:
) / 1 ( log 4567 . 0 p a T d d R E =− β (7)
From a plot of log versus β 1/Tpand fitting a straight line, the activation energy, Ea, can also be
obtained from the slope. By using the Kissinger as well as the Ozawa method the activation energy can be determined without knowing the order of reaction.
In most cases of the investigated compounds, it is assumed that the rate constant follows the Arrhenius law and that the exothermic reaction can be considered as a single step; certainly the conversion at the maximum rate is independent of the heating rate, when this is linear. In order to get a better agreement of the activation energies determined according the Kissinger and Ozawa method, following the ASTM protocol, a refinement of the Kissinger activation energy (7) according (9) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛− = ) / 1 ( ) (log 303 . 2 10 T d d D R Ea β (9)
using given D factors in 53 leads to very close agreements.
The following procedure describes a general DSC experiment, measurements deviating from this procedure will be stated: Samples ( ~ 0.3 − 1.5 mg) for DSC measurement were analyzed with a nitrogen flow of 20 mL/min in closed Al-containers with a hole (1 µm) on the top for gas release and a 0.003*3/16-in. disk was used to optimize good thermal contact between the sample and container (according ASTM E 698 – 99)53. The reference sample was
the reference pan were heated in a differential scanning calorimeter (Perkin-Elmer Pyris 6 DSC,57 calibrated by standard pure Indium and Zinc) at heating rates of 2, 5, 10, 15 and 20 °C. In the most cases the decomposition points are given at a scan rate of 10°C/min. For the removal of moisture, the samples were dried (if possible) in vacuo for 2 h at an appropriate.
Bomb calorimetry
For all calorimetric measurements a Parr 1356 bomb calorimeter (static jacket) equipped with a Parr 207A oxygen bomb for the combustion of highly energetic materials was used.58 The samples (ca. 80 – 100 mg) were loaded in (energetically) calibrated Parr gelatine capsules (0.9 mL) and a Parr 45C10 alloy fuse wire was used for ignition. In all measurements a correction of 2.3 (IT) calories per cm wire burned has been applied and the bomb was examined for evidence of noncombusted carbon after each run. A Parr 1755 Printer was furnished with the Parr 1356 calorimeter to produce a permanent record of all activities within the calorimeter. The reported values are the average of three single measurements. The calorimeter was calibrated by combustion of certified benzoic acid (SRM, 39i, N.I.S.T) in oxygen atmosphere at a pressure of 3.05 MPa. Typical experimental results of the constant volume combustion energy (∆cUm) of the compounds are summarized in corresponding Chapters and are assigned. The standard molar enthalpy of combustion (∆cHm°) was derived from
nRT U Hm c m c =∆ +∆ ∆ ° (∆ =
∑
i nn (products, g)−
∑
ni (reactants, g);∑
ni is the total molar amount of gases in products or reactants). The enthalpy of formation, ∆fH°, for each of the corresponding salts were calculated at 298.15 K using designed Hess thermochemical cycles.Explosion experiments
For the analysis of the explosion gases of all compounds, a specially equipped IR-cell was loaded with about ~ 2 mg of the sample and evacuated. The sample holder of the IR cell was heated rapidly to 450°C to initiate the explosion. The explosion products were allowed to expand into the gas cell and the IR spectrum was recorded. For the recording of the mass spectra, a sample of about 1 mg of the compounds was rapidly heated to 450°C to initiate the explosion in a one side closed glass tube (length: 500 mm; diameter: 5 mm) connected to the
spectrometry (JEOL MStation JMS 700)59 using electron impact (EI) mode (mass range 1 – 120; 1 scans per second). In order to analyze the gases from the stepwise decomposition of the compounds, a specially equipped IR-cell was loaded with the compounds (~ 2 mg) and evacuated. The sample holder of the IR cell was heated at a rate of 1°C/min (CARBOLITE 900°C Tube Furnace type MTF 9/15)60 and the reaction products were allowed to expand continuously into the gas cell. During this heating, IR-spectra were recorded continuously as a function of the heating rate using a Perkin-Elmer Spektrum One FT-IR57 instrument.
3.3.2 Sensitivity Test1
Calorimetric tests capture temperature-time response of a substance and are performed to detect thermal instability. However, the energy stored within the substance can be released by a variety of stimuli. Sensitivity is defined as the ease with which a substance subjected to external stimuli, such as shock, impact or heat, can undergo detonation.61 A few of the techniques used to determine the sensitivity1 of a material are discussed below.
Impact Sensitivity
During impact tests, the impact of a drop-weight on a substance is assessed. The sample, placed between two flat, parallel, hardened steel surfaces, is subjected to an impact by dropping a weight. The impact may result in initiation depending on the sensitivity of the material, weight mass, and its drop height (impact energy). Initiation is observed by sound, light effects, smoke, or by inspection. The BAM impact apparatus, known to give fairly reproducible results, is shown in Figure 1.6. Typically drop weights having a mass of 1, 2, 5 or 10 kg are used and the lowest energy required to create a detonation is recorded. Thus drop-weight and drop-height at which the initiation of the sample occurs are the main parameters determined from impact testing. The drop height at which detonation is observed is thus a measure of impact sensitivity of an explosive. A typical experiment runs as following: A small amount of pre-weighed sample, usually around 20 mg, is placed in a brass cup for each test. 6 µm HMX was tested previously as a standard, giving value of 34 kg cm for five consecutive negative results. Drop heights are measured with falling of 1 and 5 kg mass and a minimum drop height considered for six consecutive drops at a specific height and mass with no change in sample. The result is rated as “+”, if the lowest impact energy an explosion occurred (in six single trials) is ≤ 2 J. “+” indicates that the corresponding compound is too dangerous for transport. In the case of no explosion or impact > 2 J the result is rated as “-“. Table 1.2 gives some examples.
Table 1.2. Impact sensitivity of selected examples
Substance Impact energy [J] result
Ethylnitrite 1 + N2H5ClO4 (dry) 2 + Pb(N3)2 2.5 - Lead styphnate 5 - Nitroglycerin (NG), liquid 1 + Hg(ONC)2 1 + PETN (dry) 3 - RDX (dry) 5 - Tetryl (dry) 4 -
Friction Tester
The sample is placed on a rough ceramic plate and a force (created by different weights on the lever) is loaded on the sample trough a stationary pin in contact with the plate. The plate is motor driven trough a complete cycle pass beneath the pin. The test sample is subjected to the friction created by the rubbing of the pin against the plate. Normally the test is run with a pin load of 5 − 10 − 20 − 40 − 60 − 80 − 120 − 160 − 240 − 360 N or values in between depending of the weight and the used groove. Each experiment is evaluated with respect to “no reaction”, decomposition (change of color, smell) or explosion (bang, crackle, spark formation, ignition) and continued, by changing the pin load, until no explosion occurred within six single tests. A compound is classified as not friction sensitive if each single test with a friction load of 360 N was evaluated as decomposition or “no reaction”. The result is rated as “+”, if the lowest friction load an explosion occurred (in six single trials) is < 80 N. “+” indicates that the corresponding compound is too dangerous for transport. In the case of no explosion or friction ≥ 80 N the result is rated as “-“. Table 1.3 gives some examples.
Table 1.3. Friction sensitivity of selected examples
Substance Friction energy [N] result
HMX (dry) 80 - N2H5ClO4 (dry) 10 + Pb(N3)2(dry) 10 + Lead styphnate 2 + TNT 360 - Hg(ONC)2 10 + PETN (dry) 60 + RDX (dry) 120 - Hexanitrostilben 240 - Koenen Test
Figure 1.8. Koenen Test
The Koenen Test measures the effect of strong heating under confinement. The sample is contained in a drawn steel tube (27 cm3) equipped with an closure, which allows orifice plates with various apertures of diameters 1.0, 1.5, 2.0, 2.5, 3.0, 5.0, 8.0, 12.0 o 20.0 mm (Figure 1.8). The tube is heated with four calibrated propane burners. The result reported from such a test is the largest size orifice at which the tube is fragmented.
Table 1.4. Fragmentation degree Types of
Fragments Description result
0 Thimble is unchanged −
A T. plate is dented in −
B T. plate and sides are dented in −
C T. plat is broken −
D T. is teared up −
E T. is put in two parts −
F T. is destroyed in three or more big pieces, which can be connected Explosion G T. is destroyed into little pieces, top is
undamaged Explosion
H T. is damaged in a lot of little pieces, the top is damaged too Explosion
The first experiment is performed with a nozzle plate of any diameter. If an explosion occurs the next test will be done with an orifice plate with a 50 % bigger port diameter. This procedure is repeated until no explosion occurs. The appearance of the fragmentation degree decides if an explosion occurred or not. Table 1.4 shows the possible outcomes. A decomposition which leads to a partitioning of the thimble in three or more fragments is called an explosion. The valuation of a substance in order to its thermal sensitivity is combined in Table 1.5.
Table 1.5. Validation guidelines
Valuation Port diameter [mm]
non sensitive Ø < 2
few sensitive 2 ≤ Ø < 10
sensitive 10 ≤ Ø < 16
very sensitive 16 ≤ Ø < 20 extreme sensitive Ø ≥ 20
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