Determination Of Hydroxyl Value Research Articles

NMR Analysis of Thermally‐Oxidized Hydroxyl‐Terminated Polybutadiene (HTPB)

AbstractNuclear magnetic resonance spectroscopy was employed to monitor the change in chemical structures, olefin units (cis, trans and vinyl) and hydroxyl value on stabilized Hydroxyl‐terminated polybutadiene (HTPB) under accelerated ageing condition. Thermal ageing of HTPB was carried out at 65 °C for 10‐weeks and periodically withdrawn sample for NMR analysis. 1H and 13C NMR spectroscopy provided detailed structural information for all HTPB samples, including the quantification of olefin units and the determination of hydroxyl value. The analysis revealed a decrease in signal intensity, particularly for the olefin near or at the molecular end, suggesting that they were oxidized before those in the middle position within the chain. The quantitative assessment of olefin units indicates a slight decrease of 2 % in 1,2‐vinyl unit after 10‐weeks of ageing. The NMR spectra did not show any detectable signals corresponding to epoxides, peroxides or alcohols in any HTPB samples. However, a slight increase in the OH value was observed after 8 and 10 weeks of ageing, suggesting the possible incorporation of new hydroxyl groups due to thermal‐oxidation. The antioxidants used to stabilize HTPB exhibited limited effectiveness in preventing degradation reactions, even after 4 weeks of ageing at 65 °C.

Determination of hydroxyl value of vegetable oils‐based polyols through ring‐preopening, solvent‐extraction, and acetylation method

AbstractVegetable oils‐based polyols prepared by epoxidation‐hydroxylation often have the phenomenon of the coexistence of epoxy and hydroxyl groups due to different ring‐opening degrees. The acylation method recommended by the American Society of Testing Materials (ASTM) standard (D1957‐86) and the Association of Official Analytical Chemists (AOAC) standard (965.32) is applicable only to fatty alcohols in oils and fats and their derivatives but not to vegetable oils‐based polyols since the residual epoxy groups in vegetable oils‐based polyols lead the tested hydroxyl value (OHV) to be higher than the actual OHV. A method combining ring‐preopening of residual epoxy groups, ether extraction of ring‐preopened vegetable oils‐based polyols, and subsequent acetylation by acetic anhydride‐acetic acid was established for OHV determination of vegetable oils‐based polyols. The accuracy of the method was verified by the known theoretical OHVs of short‐chain alcohols and simulated vegetable oils‐based polyols. The absolute values of relative deviations for OHVs of short‐chain alcohols and simulated vegetable oils‐based polyols were within 1.0% and 3.1%, respectively, which indicates the feasibility of the established method in eliminating the negative effects of residual epoxy groups in vegetable oils‐based polyols on OHV determination as well as accurately determining and evaluating the OHV of vegetable oils‐based polyols. The method can broaden the range of OHV determination up to 1800 mg KOH/g. The ratio of acetic anhydride and acetic acid and reaction time are key factors affecting the complete degree of acetylation, which can be regulated mutually in accurately determining the OHV of vegetable oils‐based polyols according to the practice. It is the first time, to our best knowledge, to establish a method to eliminate the negative effects of residual epoxy groups in vegetable oils‐based polyols on OHV determination. The established method provides a feasible method for polyol industry to accurately evaluate the product quality of vegetable oils‐based polyols.

Facile method based on 19F-NMR for the determination of hydroxyl value and molecular weight of hydroxyl terminated polymers.

A new, facile and low-sample consuming technique for the determination of hydroxyl values (OHVs) in poly(hydroxyalkanoate)s (PHAs) is herein presented. After a fast, uncatalyzed and non-destructive trifluoroacetylation of all PHA hydroxyl groups, OHVs are calculated through 19F-NMR measurements, comparing integral values of the only two signals in the spectra: the fluorinated hydroxyl groups and the internal standard (trifluorotoluene) signals. Furthermore, the combined ex situ functionalization with a simple workup of the fluorinated polymer allowed to obtain spectra with an improved signal/noise ratio and short acquisition time if compared to 1H-NMR-based methods. The results obtained by 19F-NMR measurements are then validated by the established standard method based on acid/base titration and the 1H-NMR-based method. The proposed approach shows to be valuable not only for low molecular weight PHAs, but also for high molecular weight samples, which typically cannot be analysed by conventional 1H-NMR-based methods due to the very low concentration of hydroxyl terminal groups. Thanks to the observed high reliability, the method was also successfully applied to evaluate the OHVs of various commercial hydroxyl terminated polymers with different molecular weights in order to further show its wide applicability.

Evaluation of Techniques for Determination of Hydroxyl Value in Materials for Different Industrial Applications

When some materials need to be characterized, the hydroxyl number (IOH) determination is especially useful, mainly for those applied in the aerospace field. Usually, this characterization is performed by wet chemistry, using methodologies involving several steps, such as derivatization. This is a time-consuming and costly step. On the other hand, when the analysis is performed by Fourier transform infrared (FT-IR) spectroscopy, the most used region is the medium infrared (MIR) and transmission techniques are usually employed. However, FT-IR methodology developed error is usually not discussed. FT-IR methodology was developed in near infrared (NIR) and MIR regions, including non-conventional techniques, such as universal attenuated total reflection (UATR) and transflectance (near infrared reflection accessory [NIRA]), and transmission, to determine IOH in surfactants, used in aerospace catalysts/cosmetic products, and polyesters, applied in paints. According to the samples’ characteristics, surfactants were analyzed by transmission/solution and, as received, by NIRA. Polyesters were analyzed by UATR and NIRA, as received. The IOH values for all samples were also measured by wet chemistry and/or potentiometry (supplier’s data) and used as reference. Good linear correlations were observed between 0.939 and 0.976, being considered with good precision, and between 88% (NIRA) and 98% (MIR) of the results were explained by developed methodologies.

A Fast and Effective Pyridine-Free Method for the Determination of Hydroxyl Value of Hydroxyl-Terminated Polybutadiene and Other Hydroxy Compounds

ABSTRACTHydroxyl-terminated polybutadiene (HTPB) is the workhorse propellant binder for launch vehicle and missile applications. Accurate determination of the hydroxyl value (OHV) of HTPB is crucial for tailoring the ultimate mechanical and ballistic properties of the propellant derived. This article describes a fast and effective methodology free of pyridine based on acetic anhydride, N-methyl imidazole, and toluene for the determination of OHV of nonpolar polymers like HTPB and other hydroxyl compounds. This method gives accurate and reproducible results comparable to standard methods and is superior to existing methods in terms of user friendliness, efficiency, and time requirement.

Synthesis and film properties of epoxy esters modified with amino resins from glycolysis products of postconsumer PET bottles

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225–250°C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water‐soluble crystallizable fraction and water‐insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and 1H‐NMR analysis. Glycolysis product was used for synthesis of PET‐based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea‐formaldehyde and melamine‐formaldehyde resins for synthesis of epoxy ester–amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET‐based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino‐resin‐modified epoxy ester resins that have improved physical and chemical surface coating properties. POLYM. ENG. SCI., 55:2519–2525, 2015. © 2015 Society of Plastics Engineers

A single‐sample method to determine the hydroxyl values of polyols using mid‐FTIR spectroscopy

A single‐sample Fourier transform infrared (FTIR) method suitable for automation was developed to determine the hydroxyl value (OHV) of lipid‐based polyols. It is a modification of the original split‐sample FTIR method using the reaction of p‐toluenesulfonyl isocyanate (TSI) with OH groups and measures the carbamate band formed in the differential spectrum before and after the reaction. In the new method, the TSI‐isocyanate absorption is measured before and after the reaction, the area change being proportional to the OHV of the sample, but is sensitive to moisture. Moisture compensation is achieved by monitoring the CO2 produced by the water‐TSI reaction and correcting for its additional contribution to isocyanate loss. The method was validated by assessing polyol mixtures containing added water, comparing the results to those from the moisture independent split‐sample FTIR method. The single‐sample FTIR procedure had similar accuracy and reproducibility as the split‐sample method when CO2 moisture compensation was implemented. The procedure was not affected by carboxylic acids but can be affected by the presence of amines. The advantage of the new OHV FTIR method is that it requires only a single sample to be prepared and analyzed, making it amenable to automation as well as reducing sample preparation time, solvent, and reagent use.Practical applications: This paper provides an automatable, rapid, and accurate FTIR‐based method for determination of hydroxyl value of polyols, which is a critical parameter of polyols and polyurethane production. The method can be employed by commercial laboratories and researchers working in this area for quality control and to facilitate improvement and development of new products.An FTIR method is described to measure hydroxyl values of polyols using the reaction with isocyanate employed in other methods. The new approach is suitable for automation and moisture compensation is achieved in the same experiment by measuring CO2 produced. Method validation indicates that the method is accurate compared to theoretical values.

A Primary Method for the Determination of Hydroxyl Value of Polyols by Fourier Transform Mid‐Infrared Spectroscopy

AbstractA primary Fourier transform infrared (FTIR) method was developed to determine the hydroxyl value (OHV) of polyols produced from edible oils. The method is a modification of American Society for Testing and Materials 1899‐08, using toluene as the solvent to dissolve the sample and to carry the reactive reagent p‐toluenesulfonyl isocyanate (TSI). TSI reacts with OH groups to produce a carbamate, a functional group that can be measured spectrally between ~1780 and 1690 cm−1 in the differential spectrum that is obtained from spectra collected before and after the reaction. Commercially available 1‐nonanol, which has a defined OHV, is used to develop a calibration. The OHV for a variety of 1° and 2° alcohols, as well as petrochemical and lipid‐based polyols, were then measured to evaluate the performance of the method and to assess the effects of moisture on the results. The FTIR OHV were in accord with the results obtained by AOCS method Cd 13‐60 and were demonstrated to be unaffected by the presence of moisture in the sample. The new TSI‐FTIR method is simpler, much faster (~10 min), and more reproducible and accurate than the AOCS OHV titrimetric methods and is not affected by carboxylic acids, amines or moisture.

A Spectroscopic Method for Hydroxyl Value Determination of Polyols

AbstractA relatively simple method is described for routine determination of hydroxyl values for a wide range of hydroxyl containing compounds including soybean oil polyols, polyols derived from soy meal, polyether polyols and ethylene glycol as well as their blends. This method is based on reacting the hydroxyl compound with hexamethyldisilazane (HMDS) and determining the FTIR peak area of the silylated product at 1,251 cm−1. The method is simple, accurate and reproducible. It is not limited to a specific family of polyol compounds. It does not require any special equipment, hazardous chemicals and can be carried out by non‐technical staff as a rapid and convenient method for quantitative determination of hydroxyl values. An excellent linear correlation was obtained between this spectroscopic method and conventional titration methods for different polyols over a wide range of hydroxyl values. Furthermore, unlike the titration methods the current method is not affected by the presence of acid, base or small amounts of water in the test sample.

Synthesis of EB-curable hyperbranched urethane acrylate from palm oil oleic acid

Hyperbranched urethane acrylate (HBPUA) from oleic acid of palm oil has been synthesised by a three-step reaction. Dipentaerythritol was initially reacted with 2, 2-bis (hydroxymethyl) propionic acid in a solution medium aided by p-toluene sulfonic acid as the catalyst. This mixture was then used as the core (HBP) and reacted with palm oil oleic acid to form the hyperbranched polyol (HBP-1). The hyperbranched polyurethane acrylate (HBPUA) was prepared by reacting HBP-1 resin with diisocyanate and hydroxyl-containing acrylate monomer in the presence of 0.1–2 wt% dibutyltin dilaurate as a catalyst. The reaction was confirmed by several analyses, i.e., determination of hydroxyl value (OHV), Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy analyses. HBPUA was found curable when subjected to electron beam (EB) irradiation. The thermal stability of EB cured films of HBPUAs was determined by thermogravimetric analyser (TGA). The thermal decomposition of HBPUAs showed good thermal stability up to 450°C.

Investigation of the effect of hydrolysis products of postconsumer polyethylene terephthalate bottles on the properties of alkyd resins

AbstractHydrolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 200–230°C and molar ratios of PET/H2O were taken as 1/5; 1/10; 1/20. The reaction products, when extracted with boiling water, yielded a water soluble crystallizable fraction (WSCF) and a water insoluble fraction (WIF). These fractions were characterized by acid and hydroxyl value determinations and DSC analysis. WSCF and WIF were used for preparation of alkyd resins. Five long oil alkyd resins were prepared from phthalic anhydride (PA) (reference alkyd resin) or hydrolysis products of the waste PET (PET‐based alkyd resin), pentaerithrithol (PE), soybean oil fatty acid (SOFA), and ethylene glycol (EG). Film properties and thermal degradation stabilities of these alkyd resins were investigated. Drying time, hardness, alkaline resistance, and thermal oxidative degradation resistance of the PET‐based alkyd resins are better than these properties of reference resin. The results show that hydrolysis products of waste PET obtained from postconsumer bottles are suitable for manufacturing of alkyd resins. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Non-destructive method for determination of hydroxyl value of soybean polyol by LS-SVM using HATR/FT-IR

This paper presents the use of least-squares support vector machine (LS-SVM) for quantitative determination of hydroxyl value (OHV) of hydroxylated soybean oils by horizontal attenuated total reflection Fourier transform infrared (HATR/FT-IR) spectroscopy. A least-squares support vector machine (LS-SVM) calibration model for the prediction of hydroxyl value (OHV) was developed using the range 1805.1–649.9 cm −1. Validation of the method was carried out by comparing the OHV of a series of hydroxylated soybean oil predicted by the LS-SVM model to the values obtained by the AOCS standard method. A correlation coefficient equal to 0.989 and RMSEP = 4.96 mg of KOH/g was obtained. This study demonstrates a better prediction ability of the LS-SVM technique to determine OHV in hydroxylated soybean oil samples by HATR/FT-IR spectra.

Optimising Multivariate Calibration by Robustness Criteria

Regular maintenance of (multivariate) near infrared (NIR) calibration models is a crucial but time-consuming step to ensure a successful NIR application in industry. Naturally, robustness of these models is essential to minimise both maintenance time and cost. In this paper, a method combining Taguchi philosophy, experimental design and artificially-derived spectra, is proposed to evaluate and improve the robustness of NIR calibrations. This approach is based upon a typical industrial NIR application, the determination of hydroxyl value of ester products. Experiments have been designed to investigate which parameters (control and signal) influence the performance of the calibration. Two calibration models have been selected for the robustness investigation. One benchmark model was based on general criteria applied for NIR calibration and another based on Taguchi's criteria. Artificially-derived spectra were produced by adding severe fluctuations of simulated wavelength shifts into original spectra for both models, then, the models' performance was evaluated six months after the calibration. The model selected based on Taguchi's criteria, is clearly more tolerant to wavelength shifts and less sensitive for overfitting in comparison with the “benchmark” model.

Determination of hydroxyl value in fats and oils using an acid catalyst

A method for the rapid determination of the hydroxyl value of oils, fats and related products is described. The method uses toluene-p-sulphonic acid as a catalyst and this allows the sample, dissolved in toluene, to be acetylated in 10 min at room temperature. The fatty acid anhydrides formed during the acetylation are decomposed with aqueous sodium hydroxide and tert-butanol, and are then titrated with hydrochloric acid. The addition of an aliquot of the sample to the blank after the decomposition of the acetic anhydride reduces the number of titrations required to two.

Enthalpimetric determination of hydroxyl values of glycerol-alkylene oxide polyethers and butane-1,4-diol-adipic acid polyesters

Direct-injection enthalpimetry has been used to measure the hydroxyl values of some polyethers and polyesters. A determination in duplicate can be carried out in a few minutes, and it requires relatively little operational skill. The technique clearly has great potential as a method for industrial plant control. The accuracy of determinations is ± 1 to 2 per cent., which is adequate for commercial purposes, although the method is not as precise as some more lengthy procedures.

Determination of organic hydroxyl groups by nuclear magnetic resonance spectroscopy by using trimethylsilyl derivatives

A nuclear magnetic resonance spectroscopic method is presented for the determination of hydroxyl values in mixtures of organic compounds. A nine-fold enhancement of sensitivity is obtained by the formation of trimethylsilyl derivatives, which makes the method especially useful for the determination of low hydroxyl values. The method can be applied to the rapid determination of the hydroxyl values of fatty acids, esters, polymerised fatty acids, polyesters, tertiary alcohols and certain phenols. O-Nitrophenols and highly hindered phenols fail to give correct results, as do hydroxy-compounds of low relative molecular mass, which give volatile trimethylsilyl derivatives. Epoxides and non-enolised ketones do not interfere in the determination. Certain shortcomings of methods for the determination of hydroxyl values based on acetylation and differential titration are discussed.

Determination of Hydroxyl Value of Alcohols by Near-Infrared Spectroscopy

Determination of Hydroxyl Value of Alcohols by Near-Infrared Spectroscopy