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Pyrolysis, fire behaviour and mechanical properties of a blend of poly(butylene terephthalate) (PBT) with a phosphorus polyester (PET-P-DOPO) are investigated and compared with PBT/aluminium diethylphosphinate (AlPi-Et) composites. The PBT/PET-P-DOPO is immiscible and exhibits gas-phase and condensed-phase activity, whereas AlPi-Et in PBT results mainly in flame inhibition. Only higher loadings of AlPi-Et yield significant condensed-phase activity. Using the same phosphorus content, PBT/PET-P-DOPO and PBT/AlPi-Et exhibit similar reductions in fire load (22%) and flame spread (17% assessed by fire growth rate, FIGRA), compared with PBT. In contrast to AlPi-Et, the addition of PET-P-DOPO does not decrease the tensile strength of PBT. Thus, PET-P-DOPO is an interesting alternative to low-molecular-weight flame retardants.
Flame retarded poly(butylene terephthalate) (PBT) is required for electronic applications and is mostly achieved by low molar mass additives so far. Three phosphorus-containing polyesters are suggested as halogen-free and polymeric flame retardants for PBT. Flame retardancy was achieved according to cone calorimeter experiments showing that the peak heat release rate and total heat evolved were reduced because of flame inhibition and condensed-phase activity. The presented polymers containing derivatives of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide form immiscible blend systems with PBT. Shear-rheology shows an increase in storage moduli at low frequencies. This is proposed as quantitative measure for the degree of phase interaction. The phase structure of the blends depends on the chemical structure of the phosphorus polyester and was quite different, depending also on the viscosity ratio between matrix and second phase. A lower viscosity ratio leads to two types of phases with spherical and additionally continuous droplets. Addition of the flame retardants showed no influence on the dielectric properties but on the mechanical behavior. The polymeric flame retardants significantly diminish the impact strength because of several reasons: (1) high brittleness of the phosphorus polyesters themselves, (2) thermodynamic immiscibility, and (3) weak phase adhesion. By adding a copolymer consisting of the two base polymers to the blend, an improvement of impact strength was obtained. The copolymer particularly acts as compatibilizer between the phases and therefore leads to a smaller phase size and to a stronger phase adhesion due to the formation of fibrils.
Dampening of energetic properties and the effects of blending proportions of isododecane on the diffusive burning behaviour of peroxy-fuels are experimentally studied. Blended peorxy-fuels are obtained by adding isododecane in the proportions of 25 wt.%, 50 wt.% and 75 wt.%, respectively, in technical pure peroxy-fuels. The fuels were burned in form of pool fires with diameters 0.02 m ≤ d ≤ 1 m. The mass burning rates and relative flame lengths are found to be weakened with increasing diluent proportions. By measuring the mass burning rates and visible flame lengths of pool fires of different samples of fuel blends an optimum blending criterion is developed. Furthermore, it is shown that the dilution proportions and flame characteristics can be correlated by empirical equations.
Numerous new tin catalysts that enable the synthesis of cyclic polylactides with broad variation in their molecular mass were recently developed. The abundance of cyclics in matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra is, however, frequently reported to greatly exceed that of linears. Thus, the MALDI ionization behavior of various end-capped linear poly(L-lactide)s and one cyclic poly(L-lactide) was investigated and compared.
Neat compounds and various blends of cyclic and linear species were prepared and studied under identical conditions with regard to sample preparation and instrumental condition, except for the laser power. For this purpose, two different MALDI-TOF mass spectrometers were applied.
Our results reveal that cyclics indeed show a slightly better ionization in MALDI, although their ionization as a neat compound seems to be less effective than that of linear polylactides. The ionization of most linear polylactides investigated does not depend on the end group structure. However, linear polylactides containing 12-bromododecyl end groups reveal an unexpected saturation effect that is not caused by fragmentation of the polymer or the end group, or by electronic saturation of the detector digitizer. Furthermore, polylactides with a 2-bromoethyl end group did not show such a saturation effect.
An overestimation of cyclic species in MALDI-TOF mass spectra of poly(L-lactide)s must be considered, but the commonly assumed peak suppression of linear polymers in mixtures of both structures can be excluded.
RATIONALE
The fast and univocal identification of different species in mixtures of pollen grains is still a challenge. Apart from microscopic evaluation and Raman spectroscopy, no other techniques are available.
METHODS
Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry was applied to the analysis of extracts of single pollen grains and pollen mixtures. Pollen grains were fixed, treated and covered with matrix directly on the MALDI target.
RESULTS
Clearly resolved MALDI ion intensity images could be obtained enabling the identification of single pollen grains in a mixture.
CONCLUSIONS
Our results demonstrate the potential and the suitability of MALDI imaging mass spectrometry as an additional method for the identification of pollen mixtures.