Dynamic mechanical thermal analysis and isothermal thermogravimetry yield useful information on the temperature dependence
of the mechanical properties and thermal stability of silicone rubbers.
In the thermal mechanical relaxation spectra, only one characteristic phenomenon may be observed.
Isothermal thermogravimetry reveals that the thermal degradation is a first-order reaction. The experimental results provide
a possibility for the calculation of overall (apparent) reaction rate constants characteristic of the thermal decomposition
process, and for the calculation of half-time values.
The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,Ec,Es andEe, respectively. It was found that during strain recoveryEs(>Ee) andEe increase monotonically with increasing load,m1, on the sample. The extrapolated value of Es atm1=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofEc also increased with increasingm1, and atm1=600 g (1.93 t cm−2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,Es,Ec andQ were also investigated for silicone rubber. It was found thatEs (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,Es was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol−1 (atD=1.2) to 56 J mol−1 (atD=1.9). FurthermoreEc (5.58 MPa atm1=133.8 g (429.4 kg cm−2)) increased gradually with increasing m1 and attained 16.6 MPa atm1=548.4 g (1.76 t cm−2). In the case of creep,Q was in the range of 0–11.5 J mol−1 and larger when larger loads,m2 were removed during the later stages of creep.
new polycyclic nitramine 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW)
has been focused as a considerable amount of research recently on investigating
its polymorphs, relative stability, and respective reaction chemistry. It
is known as CL-20 popularly, CL-20 is a very high-energy and relatively high
oxygen balance value crystalline compound whose method of synthesis and detailed
performance data are still classified. 5-oxo-3-nitro-1,2,4-triazole (NTO,
or nitrotriazolone) was an insensitive molecule comparison general explosives,
and the NTO based polymer bonded explosives (PBX) was a low vulnerability
explosive. Both energetic materials are all very important high explosives,
which is used in a variety of military formulations widely owing to the properties
of high energy and desensitization of PBX, many researchers have demonstrated
the usefulness of above two energetic materials in explosive component. In
this work, the thermal decomposition characteristics of explosives CL-20 and
NTO were studied using thermal analytical techniques (TG, DSC), then the compatibility
of above two explosives with silicone rubber, and the decomposition kinetic
parameters such as activation energies of decomposition, the frequency factor
of the decompose reaction are also evaluated by non-isothermal DSC techniques.
The possibility of use of a powder-like polymeric hydrogel of 2-hydroxyethyl methacrylate with 33 wt.% methacrylic acid as potential pharmaceutical adjuvant in the form of a composite powdered material, with silicone rubber in the form of matrices for transdermal therapeutic system has been studied. The effect of solvents and the content of composite hydrogel in matrices on the rate of permeation of an antianginic drug, radioactive labeled glycerol trinitrate (GTN) was evaluated. The results show that hydrogel copolymers are prospective adjuvants for transdermal therapeutic systems.
CNPq, 2005–2007. Development of spectrophotometric and voltammetric methods for determination of antihypertensive drugs.
FAPESP, 2006–2010. Development of polyurethane/graphite and siliconerubber/graphite composite
Authors:Tibor Szili-Kovács, Ágnes Bálint, Györgyi Kampfl, Krisztina Kristóf, György Heltai, Sándor Hoffmann, András Lukács, and Attila Anton
transformation of different nitrogen fertilizer in a soil core incubation and a pot experiment. Cereal Res. Commun.
, P., 1990. Sampling air from dung pats by siliconerubber diffusion chambers
Authors:Jerzy J. Chruściel, Grażyna Janowska, and Marzena Fejdyś
the lengths of dimethylsiloxane segments, on the contents of boron, and on the degrees of branching of macromolecules. The T g values of the most PMVBSs are lower than those for PDMS (oils with linear structure and siliconerubbers