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Hydroxyl is an important functional group and knowledge of its content is required in many intermediate and end-use products such as polyols, resins, lacquer raw materials and fats (petroleum industry). The test method to be described determines primary and secondary hydroxyl groups. The hydroxyl number is defined as the mg of KOH equivalent to the hydroxyl content of 1 g of sample.The most frequently described method for determining the hydroxyl number is the conversion with acetic anhydride in pyridine with subsequent titration of the acetic acid released: H3C-CO-O-CO-CH3 + R-OH -> R-O-CO-CH3 + CH3COOH. However, this method suffers from the following drawbacks: - The sample must be boiled under reflux for 1 h (long reaction time and laborious, expensive sample handling) - The method cannot be automated - Small hydroxyl numbers cannot be determined exactly - Pyridine has to be used, which is both toxic and foul-smellingBoth standards, ASTM E1899-08 and DIN 53240-2, offer alternative methods that do not require manual sample preparation and therefore can be fully automated: The method suggested in ASTM E1899-08 is based on the reaction of the hydroxyl groups attached to primary and secondary carbon atoms with excess toluene-4-sulfonyl-isocyanate (TSI) to form an acidic carbamate. The latter can then be titrated in a non-aqueous medium with the strong base tetrabutyl- ammonium hydroxide (TBAOH). The method suggested in DIN 53240-2 is based on the catalyzed acetylation of the hydroxyl group. After hydrolysis of the intermediate, the remaining acetic acid is titrated in a non-aqueous medium with alcoholic KOH solution. The present work demonstrates and discusses an easy way to determine the hydroxyl number according to ASTM E1899-08 or DIN 53240-2 with a fully automated titrimetric system for a great variety of industrial oil samples.

The presence of excessive water in plastics adversely affects the performance of polymeric goods which is why water determination is of crucial importance. This article describes the accurate and straightforward determination of the water content using the Karl Fischer Oven Method in ten different plastic types that are not amenable to direct Karl Fischer titration. The experiments revealed that besides the determination of the oven temperature, sample preparation is one of the most important steps of the analysis, especially in case of hygroscopic plastic samples.

The Combustion IC system presented allows the automated determination of organic halogen and sulfur compounds in all flammable samples. Both combustion digestion, which is automatically controlled with a flame sensor, and the professional Liquid Handling guarantee highest precision and trueness. This poster describes the determination of the halogen and sulfur content in a certified polymer standard, a coal reference material as well as in latex and vinyl gloves.

Indication of the titration endpoint of the weakly alkaline or weakly acidic terminal groups in non-aqueous solution is frequently not easy. An improvement is possible by using a suitable titrant (TBAH = tetrabutylammonium hydroxide for terminal carboxyl groups; perchloric acid for terminal amino groups).An improvement in the evaluation can also be achieved by choosing benzyl alcohol as the solvent.The choice of electrode combination and the measuring setup is also important. Differential potentiometry using the three-electrode technique results in a great improvement in titrations in poorly conducting solutions. Noisy signals are eliminated.

This Application Bulletin describes a simple polarographic method to determine monomeric styrene in polymers. The limit of determination lies at 5 mg/L. Before the determination, styrene is converted to the electrochemically active pseudonitrosite using sodium nitrite.

Maleic and fumaric acid can be reduced electrochemically to succinic acid. In acidic solutions a differentiation of the two acids is not possible since both are reduced at the same potential. On the other hand, separation at pH 7.8...8.0 is easily possible since fumaric acid is now more difficult to reduce at the lower proton concentration (as a result of cis-trans isomerism) than maleic acid.

Polyurethanes are one of the most commonly used types of plastic. They are produced by the reaction of raw polyols with isocyanates. Depending on the starting material a wide variety of plastics can be obtained. The determination of the acid value, hydroxyl value, and isocyanate content plays an important part in the analysis of raw materials for plastics.The acid number of polyol raw material is usually used in quality control to ensure batch-to-batch uniformity. Additionally it is used as correction factor for calculating the true hydroxyl number. In this Application Bulletin the determination of the acid number according to ASTM D4662 and ASTM D7253 is described.One raw material for polyurethanes are polyols. Polyols contain multiple hydroxyl groups. Therefore, hydroxyl number of a raw material directly correlates to the amount of polyols present and it is thus an important quality control parameter. In this Application Bulletin the determination of the hydroxyl number according to ASTM E1899 and DIN 53240-3 is described.As polyols react stoichiometrically with isocyanates, the knowledge of the isocyanate content is an important quality parameter for the production of polyurethanes. In this document the determination according to EN ISO 14896 method A, ASTM D5155 method A and ASTM D2572 is described.

This Application Bulletin describes the determination of the thermostability of PVC in accordance with ISO 182 Part 3 using the dehydrochlorination method with the 895 Professional PVC Thermomat. The instrument permits fully automatic determination of the stability time. The test is suitable for monitoring the manufacture and processing of PVC products manufactured in the injection molding process, for their final clearance, characterization and for the comparison of PVC products and for testing the effectiveness of heat stabilizers.

Generally speaking, the gas extraction or oven method can be used for all samples which release their water when they are heated up. The oven method is indispensable in cases in which the direct volumetric or coulometric Karl Fischer titration is not possible, either because the sample contains disruptive components or because the consistency of the sample makes it very difficult or even impossible to transfer it into the titration vessel.The present Application Bulletin describes automatic water content determination with the aid of the oven technique and coulometric KF titration, using samples from the food, plastic, pharmaceutical and petrochemical industry.

The presented titration system can be used for the fully automated determination of the hydroxyl number (HN) according to ASTM E1899 and EN ISO 4629-2. The method allows, the determination of polyols and oxooils without boiling under reflux or other sample preparation and is therefore a big benefit for laboratories that have to cope with a high sample throughput.The standards EN 15168 and DIN 53240-3 relay on the same analysis method as in ASTM E1899.

The present Application Bulletin elucidates several applications for the polymer industry that can be carried out with the aid of NIR instruments. This Bulletin contains analyses of a wide range of parameters in a very large array of samples. The hydroxyl number is one of the best-known of the parameters that can be determined rapidly using near-infrared spectroscopy. The determination of the hydroxyl number in different areas and in different polyol types is also a part of this Bulletin. Each application describes the sample and the instrument that was originally used for the analysis, as well as the recommended instruments and the results.

This method is applicable to all samples containing glycerin in the absence of other triols or other compounds that react with periodate to produce acidic products. Glycerin may be determined in the presence of glycols. A periodate solution reacts slowly with diols and triols in acidic aqueous media at room temperature. A quantitative amount of formic acid is generated from the reaction with glycerin (a triol). The reaction with diols produces neutral aldehydes. The amount of formic acid generated by this reaction is determined by titration against sodium hydroxide.

Determination of sodium, ammonium, and potassium in polyethers using cation chromatography with direct conductivity detection.

Determination of sodium and potassium in a polyol solution using cation chromatography with direct conductivity detection.

The determination of halogens and sulfur in waste products is important. The inline combination of the Mitsubishi Combustion Module with the Metrohm IC is a suitable method for this type of samples. The recovery rates are analyzed with a certified reference material, e.g., a low-density polyethylene (LDPE).Keyword: pyrohydrolysis

Latex gloves are used in clean room environments in order to prevent contaminations. The use of gloves that release corrosive halogenides or sulfate is forbidden in nuclear power plants. The total content of halogen and sulfur is determined by means of Combustion Ion Chromatography. An eluate test is carried out to check the elutable percentage of halogens and sulfate from gloves. Sample preparation is comprised of preconcentration and matrix elimination (MiPCT-ME), as described in AN-S-304.Keyword: pyrohydrolysis

Combustion Ion Chromatography combines pro-hydrolytic sample combustion and the absorption of emerging combustion gases in an oxidizing, aqueous solution that is then channeled to an ion chromatograph for the analysis of halogenides and sulfur (as sulfate). The combustion and analysis of the certified reference materials (ZRM) makes clear the reliability of Metrohm Combustion Ion Chromatography.Keyword: pyrohydrolysis

Polyisobutene (PIB) is an important raw material for a large range of products. Quality control requires the determination of the fluorine content. This task is easily done by Metrohm Combustion IC applying flame sensor technology and Inline Matrix Elimination.Keyword: pyrohydrolysis

The Restriction of Hazardous Substances Directive (RoHS) requires to reduce the halogen content in several organic materials used in electrical and electronic equipment. In this context, there is a huge interest for using halogen-free polymers. To check for halogens in polymers according to standard IEC 60754, Metrohm Combustion IC applying flame sensor technology and Inline Matrix Elimination is an indispensable method. The examined polymeric material contains halogens at a level of up to 1%.

The manufacture of ultrapure water for the pharmaceuticals industry or the semiconductor industry requires high-quality ion exchangers. Metrohm Combustion Ion Chromatography is an indispensable tool in this connection for testing the purity of anion exchange material. The output sample was wet and had to be dried at 105 °C in a special oven with waste air evacuation.Keyword: pyrohydrolysis

The EU directive for limiting the use of certain hazardous substances in electrical and electronic devices and IEC 61249-2-21 define limit values for halogen contents in materials that are used in electronics. Metrohm Combustion IC with ion chromatography determination permits precise, rapid and automated halogen determination in raw materials that are used in printed circuit boards according to IEC 61189-2.Keyword: pyrohydrolysis

Halobutyl rubber is frequently used in the production of pharmaceutical stoppers. It is ideal for this application due to its low permeability to gases and its chemical resistance. Chlorinated and brominated butyl rubber stoppers are analyzed for their halogen and sulfur content. Halogen and sulfur compounds are released by pyrohydrolysis and analyzed by subsequent ion chromatography (IC).

Polystyrol is brominated to increase flame retardation. The brominated polystyrene finally consists of 25 to 35% of bromine. The determination of bromine by combustion ion chromatography (CIC) requires a specially optimized absorption solution to trap all bromide. This work shows the optimization of the absorption solution for high-bromine samples.

Polymer materials that are used for building and decoration purposes need to be flame resistant. To reach the required level of resistance flame-retardants are added to the plain polymer. Flame-retardants are often haloorganic compounds. The use of such components and the respective concentration of introduced halogens can be determined by Combustion IC. The recovery over the full system is tested with acertified reference material (CRM).

Organic halides must be monitored in the environment. Combustion ion chromatography (CIC) is used for accurate halogen analysis in solids following EN 17813:2023.

The International Standard ISO 17463 describes the determination of the anticorrosive properties of high impedance organic protective coatings on metals. This technique uses cycles composed of electrochemical impedance spectroscopy (EIS) measurements, cathodic polarizations and potential relaxation. This application note shows the compliance of the Metrohm Autolab PGSTAT M204 and flat cell with the standard ISO 17463.

The water content of plastic chips is determined according to Karl Fischer. Because of the low water content of the sample, the oven method (200 °C) and coulometric titration have to be used.

The presence of water in expandable polystyrene (EPS) can have a negative impact on the thermal insulation properties, as it increases thermal conductivity. If EPS is exposed to a high moisture environment, additional water may be absorbed, which can further affect thermal insulation.Direct analysis of the moisture content by Karl Fischer titration requires the water to be extracted from the EPS, which involves several time-consuming steps. Therefore, determination of the water content with an oven system is preferred. As EPS expands when heated, the use of sample boats, as required by ASTM D6869, is not possible, as the EPS will contaminate the oven system. This Application Note describes the determination of water content in EPS using an oven system with closed sample vials. A determination takes about 7 to 14 min depending on the water content of the sample and the sample size.

The water content, also called moisture content, of plastics is an important quality parameter, as it affects the properties and processability of some plastics. A high water content can lead to degradation of the plastic by hydrolysis or cause surface imperfections. Additionally, it can affect the physical properties of some plastics.For this analysis, the oven technique is used, as volatile compounds present in plastics will interfere, if the water content is directly determined by coulometric Karl Fischer titration. The water content determination in polycarbonate pellets, performed with the 885 Compact Oven Sample Changer and 899 Coulometer, is described in this Application Note.

This Application Note describes the determination of copolymer levels in polyethylene (PE) and polyvinylacetate (PVA) pellets using NIRS. The determination of the composition of the polymer blends takes less than 30 seconds and requires no sample preparation. The second derivative spectra are analyzed by means of the linear least-squares regression method.

This Application Note shows that NIR spectroscopy is an excellent tool for determining low concentrations of additives in finished polypropylene pellets. This is demonstrated by monitoring the UV stabilizer Tinuvin 770 and the antioxidant Irganox 225. The application of multiple linear regression (MLR) models minimizes interferences that originate from different coating thicknesses and interferences in the polymer pellets.

This Application Note describes a fast, nondestructive, and reliable NIRS method for the determination of the hydroxyl number in polyols. Results are available in real-time for which reason NIRS is highly suited for in-process quality control. Second-derivative spectra and linear least-squares regression provide results that match very well with those obtained by titration.

During polymerization, real-time determination of hydroxyl and acid numbers of polyols provide important information about molecular weight and the reaction end point. This Application Note sheds light on the practical aspects of process monitoring in a polyol batch process using NIRS methodology. Real-time process monitoring with NIRS is the key to lower production costs and better product quality.

The determination of the water content of soft contact lenses using NIR spectroscopy is described in this Application. A liquid sample kit with gold diffuse reflector was used for measuring the lenses in transflexion mode. A PLS model was developed for predicting the water content.

Determination of the diethylene glycol content, isophthalic acid content, intrinsic viscosity (ASTM D4603), and the acid number (AN) of polyethylene terephthalate (PET) is a lengthy and challenging process due to the sample’s limited solubility and the need to use different analytical methods. This application note demonstrates that the DS2500 Solid Analyzer operating in the visible and near-infrared spectral region (Vis-NIR) provides a cost-efficient and fast solution for a simultaneous determination of these parameters in PET. Vis-NIR spectroscopy allows for the analysis of PET in less than one minute without sample preparation or using any chemical reagents.

This Application Note shows that near-infrared spectroscopy with its exceptionally short analysis times significantly accelerates quality monitoring of polymer granulates and raw materials. Polyethylene (PE) und polypropylene (PP) can be identified in parallel. PE density is also determined in the same measurement.

Functional group and viscosity analysis (ASTM D789) of polyamides can be a lengthy and challenging process due to the sample’s limited solubility. This application note demonstrates that the DS2500 Solid Analyzer operating in the visible and near-infrared spectral region (Vis-NIR) provides a cost-efficient and fast solution for a simultaneous determination of the intrinsic viscosity as well as the amine, carboxylic, and moisture content in polyamides. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows for the analysis of polyamides in less than a minute.

This Application Note demonstrates the feasibility of Vis-NIRS for the simultaneous determination of multiple chemical and physical parameters in epoxy resins. Vis-NIRS is a fast alternative to conventional lab methods: it accelerates raw material inspection, process monitoring, and final product control.

Determination of isocyanates (ASTM D7252) is a challenging procedure due to the reactivity of these organic species with atmospheric moisture, as well as their toxicity. Furthermore, HPLC analysis typically used for this kind of analysis involves sample preparation steps and chemicals, with each measurement taking up to 20 minutes to complete. This application note demonstrates that the XDS RapidLiquid Analyzer operating in the visible and near infrared spectral region (Vis-NIR) provides a chemical-free and fast solution (under one minute) for determination of isocyanate content.

Polyvinyl alcohol (PVA) is a linear polymer, used in a variety of medical products (e.g. eye drops). Here, the degree of alcoholysis is an important index for the water solubility, viscosity, and adhesion of the product. The degree of alcoholysis is defined as the percentage of hydroxyl functional groups compared to the total functional groups accessible in the molecule. Conventional alcoholysis determination can take up to six hours per sample. Compared to the primary method, analysis with near-infrared spectroscopy (NIRS) only takes one minute. The following application note describes the determination of the degree of alcoholysis by NIRS.

Determination of the density of polyethylene (PE) (ASTM D792) is normally a challenging procedure due to reproducibility difficulties. Measurement via FT-IR can be problematic when larger sample sizes must be analyzed due to sample inhomogeneity. This application note demonstrates that the DS2500 Solid Analyzer operating in the visible and near-infrared spectral region (Vis-NIR) provides a reliable and fast solution for determination of the density of PE. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows the analysis of larger, inhomogeneous sample sizes of PE in less than a minute.

Polypropylene (PP) is a general purpose resin widely used in industries such as electronic manufacturing and construction, as well as in packaging materials. PP resins must be melted first in order to be formed into the intended shape, and therefore flow properties are important characteristics which affect the production process. The standard procedure to analyze melt flow rate (MFR) requires a significant amount of work with packing the sample, preheating, and cleaning. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows the analysis of MFR in less than a minute.

Identification of individual polymers with FT-IR spectroscopy can be a challenge due to sample inhomogeneity especially when larger sample sizes need to be analyzed. This application note demonstrates that the DS2500 Solid Analyzer operating in the visible and near infrared spectral region (Vis-NIR) provides a reliable and fast solution for the identification of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP). With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows the identification of larger inhomogeneous sample amounts in less than a minute.

Determination of the vinyl content of silicone rubber is a lengthy and challenging process. First, the vinyl groups must be converted to ethylene by reacting with an acid, followed by the determination of the produced ethylene with gas chromatography (GC).This application note demonstrates that Vis-NIR (visible near-infrared) spectroscopy provides a cost-efficient and fast solution for the determination of vinyl content in silicone rubbers. With the DS2500 Solid Analyzer it is possible to obtain results in less than a minute without sample preparation or any chemical reagents.

PVC (polyvinyl chloride) foils with a PVDC (polyvinylidene chloride) coating are often used for high performance packaging films like pharmaceutical blister packs or in food packaging. In multi-layer blister films, the PVC serves as the thermoformable backbone structure, whereas the PVDC coating acts as a barrier against moisture and oxygen. The Water Vapor Transmission Rate (WVTR) and Oxygen Transmission Rate (OTR) are influenced by the composition and the thickness of the coating. A fast way to monitor PVDC coating thickness is with near-infrared spectroscopy. Results are provided in a few seconds, indicating when adjustments in the polymer production process are necessary.

To monitor the quality of PVC (polyvinyl chloride), it is important to measure the molecular weight during the production process, as this parameter has a significant influence on chemical and mechanical stability as well as fire retardant properties. The standard method to determine PVC molecular weight, defined here as the average weight of the molecules that make up the polymer, is by size exclusion chromatography (SEC). This analytical method is time-intensive and requires trained personnel to perform. Determining the molecular weight of PVC is easier with near-infrared spectroscopy (NIRS). NIRS provides results in just a few seconds and can quickly indicate when adjustments to the production process are necessary.are necessary.

The standard test method for ash content analysis is thermogravimetric analysis (TGA). Although TGA is easy to perform, it is time-intensive and requires the use of nitrogen gas. In contrast to the primary method, near-infrared spectroscopy (NIRS) is a fast analytical technique which can measure multiple parameters including ash content in polymers within one minute.

This Application Note shows the feasibility of NIR spectroscopy for the analysis of density in polyethylene granulates. Compared to the standard method, NIRS analysis shows a lower prediction error when air bubbles are present in PE pellets.

The synthetic rubber known as Bromobutyl (BIIR) has many of the attributes of butyl rubber, but has better adhesion to other rubbers and metals, resulting in substantially faster cure rates. The simultaneous quantification of the bromine content, Mooney viscosity, volatile content, calcium stearate content, and functional bromide in BIIR can be easily performed with near-infrared spectroscopy (NIRS) without the use of chemicals.

Near-infrared (NIR) spectroscopy is able to determine the intrinsic viscosity of rPET in less than one minute without any sample preparation. This Application Note demonstrates that the Metrohm DS2500 Solid Analyzer operating in the visible and near-infrared spectral region (Vis-NIR) offers users an easier way to perform this analysis without the use of toxic chemicals.