Determination of Complex Mixtures of Airborne Isocyanates and Amines.Part 3. Methylenediphenyl Diisocyanate, Methylenediphenylamino Isocyanate and Methylenediphenyldiamine and Structural Analogues after Thermal Degradation of Polyurethane

A method for the determination of individual components of complex mixtures is presented. The technique used is based on ir-absorbance measurements for stearic acid at 1700 and at 935 cm−1 when the concentration range exceeds 0.50% wt/vol; for isopropenyl stearate at 1145 and at 865 cm−1; for stearic anhydride at 1030 cm−1 and mixed stearic-acetic anhydride at 1000 cm−1. The baseline method was used in all absorbance measurements. Absorbance-concentration relationships obeyed Beer's law from 0 to 2.0% wt/vol for most compounds; the exception being stearic acid (at 1700 cm−1), where linearity was limited to a maximum 0.50% wt/vol. Due to spectral interference between the two anhydrides at low concentration ratios, an empirical percent transmission ratio method was used to estimate the relative concentration of each. Binary and ternary systems were studied and the standard deviations of the differences between theoretical and calculated values indicate that this method is reliable.

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The Effect of External Conditions on Ignition Temperature of Thermoplastic Polyurethane Elastomers

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.838-841.14 ◽

2013 ◽

Vol 838-841 ◽

pp. 14-17

Author(s):

Ivana Turekova ◽

Zuzana Szabova ◽

Tomas Chrebet ◽

Jozef Harangozo

Keyword(s):

Thermal Degradation ◽

Ignition Temperature ◽

Thermoplastic Polyurethane ◽

Thermo Gravimetric Analysis ◽

Gravimetric Analysis ◽

Polyurethane Elastomers ◽

External Conditions ◽

Thermoplastic Polyurethane Elastomers ◽

The Impact

The paper reports a study of the impact of moisture and age of pellets, as well as an external condition, on the thermal degradation of the thermoplastic polyurethane elastomers. Because thermoplastic polyurethane elastomers are hydroscopic polymer, moisture will have a significant impact on thermal degradation. For determination of the effect of moisture and age were used the thermo gravimetric analysis, differential scanning calorimeter and ISO STN 871: Plastics. Determination of ignition temperature using a hot-air furnace.

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Fast and selective HPLC-DAD method for determination of pholcodine and related substances

Macedonian Journal of Chemistry and Chemical Engineering ◽

10.20450/mjcce.2011.28 ◽

2011 ◽

Vol 30 (2) ◽

pp. 139 ◽

Cited By ~ 6

Author(s):

Ana Petkovska ◽

Hristina Babunovska ◽

Marina Stefova

Keyword(s):

Quality Control ◽

Degradation Products ◽

Ammonium Hydroxide ◽

Gradient Elution ◽

Reversed Phase ◽

Real Sample Analysis ◽

Related Substances ◽

Structural Analogues ◽

Reliable Methods

Quality control of pharmaceuticals requires development of fast, efficient and reliable methods for determination of active compounds as well as known and very often unknown impurities within defined concentration ranges. In this work, a simple and rapid HPLC-UV-DAD method for identification and quantification of pholcodine process related impurities and some degradation products was developed and validated. Pholcodine and its five structural analogues such as morphine, codeine, thebaine, oripavine, and papaverine were separated in less than 10 minutes using reversed phase LiChrospher C-8 column. For optimal chromatographic performance with reproducible retention times, gradient elution with 2% ammonium hydroxide in water and acetonitrile was used. The method was validated by establishing its selectivity, specifity, sensitivity, linearity, intra- and inter-day precision and robustness. All tested parameters confirmed that the method is suitable for determination of pholcodine and its five impurities in pharmaceutical drug samples. The results obtained from real sample analysis give support to the suitability of the proposed method for the purpose of quality control.

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Cleavage of the Graft Bonds in PVDF–g–St Films by Boiling Xylene Extraction and the Determination of the Molecular Weight of the Graft Chains

Polymers ◽

10.3390/polym11071098 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1098 ◽

Cited By ~ 1

Author(s):

Chen ◽

Seko

Keyword(s):

Molecular Weight ◽

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Thermal Degradation ◽

Gel Permeation Chromatography ◽

Extraction Time ◽

Gel Permeation ◽

Irradiation Graft ◽

Nuclear Magnetic

To determine the molecular weight of graft chains in grafted films, the polystyrene graft chains of PVDF–g–St films synthesized by a pre-irradiation graft method are cleaved and separated by boiling xylene extraction. The analysis of the extracted material and the residual films by FTIR, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) analyses indicates that most graft chains are removed from the PVDF–g–St films within 72 h of extraction time. Furthermore, the molecular weight of the residual films decreases quickly within 8 h of extraction and then remains virtually unchanged up to 72 h after extraction time. The degradation is due to the cleavage of graft bonds, which is mainly driven by the thermal degradation and the swelling of graft chains in solution. This allows determination of the molecular weight of graft chains by GPC analysis of the extracted material. The results indicate that the PVDF–g–St prepared in this study has the structure where one or two graft chains hang from each PVDF backbone.

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