Контроль качества готовых полимерных и пластмассовых изделий

Illustration QC of finished plastic products

 

High-performance polymers are used in virtually any industry and found in most consumer products. The carefully designed properties of these polymers are achieved through very precise and complex production steps. To ensure that the polymers conform to the specifications, quality control of the finished products is a key aspect in the production chain.

Metrohm offers dedicated solutions for the determination of many parameters, such as:


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Regulatory compliance in quality testing

Our instruments are suitable for a variety of analyses in compliance with ASTM, ISO, and DIN standards.

> See how you can comply with international standards using Metrohm instruments

 

Spectroscopy for polymer testing

Spectroscopic techniques offer several advantages when it comes to analyzing polymer samples. Generally, sample preparation is kept to a minimum or not required at all, and the measurements are nondestructive. As a result, the entire procedure is simple and time-saving – providing accurate results within seconds.

With the NIRS DS2500 Analyzer from Metrohm, you can perform reflectance measurements for polymers in any environment. This compact and robust analyzer allows you to measure multiple parameters simultaneously.

> Learn more about the NIRS DS2500 Analyzer

> See what parameters you can analyze with a NIRS DS2500 Analyzer

Checking additives in finished plastics

Polymer additives are used to modify polymers in various ways: to create a particular color, to make the material easier to process and longer lasting, to change the appearance, or to make it softer and more flexible, to name but a few. Hence, the content of these stabilizers in the finished product must be checked to confirm that it conforms to the requirements.

Using spectroscopy, you can determine low levels of additives directly in intact polymer pellets. Metrohm has developed an exemplary application for the determination of a light stabilizer (Tinuvin 770) and an antioxidant (Irganox 225), illustrating the scope and ease of use of spectroscopy.

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Проверка уровня сополимера в готовых пластмассах

Невозможно переоценить влияние последовательного порядка различных мономерных звеньев в полимерах. Этот порядок определяет основные свойства конечного продукта.

Спектроскопия позволяет определять уровни сополимера в полимерных гранулах без пробоподготовки, обеспечивая легкое и быстрое подтверждение качество продукта.

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Быстрая идентификация переработанного пластика с помощью рамановский спектроскопии

Работа с пластиковыми отходами - одна из важнейших задач человечества в настоящем и будущем. Однако для переработки отходов нужно знать, с каким типом материала предстоит работать.

Рамановская спектроскопия идеально подходит для идентификации функциональных групп в полимерах и для выявления деталей полимерных структур. Методы, которые работают в сфере НИОКР и производства, также актуальны в индустрии переработки пластмасс. Здесь важно отсортировать пластик по типу материала. Рамановская спектроскопия может эффективно различать такие материалы, как ABS, PE, PS, PET и PMMA в отходах, независимо от цвета, поверхностной воды, деформации или грязи - и все это в течение нескольких секунд и без какого-либо контакта с материалом.

> Подробнее об анализаторе Mira M-1

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Thermostability testing of PVC

PVC and other chloride-containing polymers are among the most versatile and useful synthetic materials available. However, these materials have a low thermostability. At elevated temperatures, these polymers degrade and release hydrogen chloride (HCl). This so-called PVC dehydrochlorination is a serious drawback, but can be largely eliminated by the addition of thermal stabilizers. The finished product’s thermostability, however, has to be checked as part of quality control.

The determination of HCl is described in the ISO 182 Part 3 standard. The method used for determining the thermostability of polymers involves heating of polymer samples, transferring the HCl gas that forms into a solution, and measuring the conductivity of the solution.

Metrohm offers a dedicated instrument for this measurement: the 895 Professional PVC Thermomat. With this instrument, you can analyze multiple PVC samples simultaneously and control the entire process on your computer.

> Learn more about the 895 Professional PVC Thermomat

It goes without saying that Metrohm supplies not only the instruments but also the applications for determining the thermostability of PVC and other chloride-containing polymers. Read more in the documents you can download below.

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Water determination in plastics

Polymers readily absorb water. The properties of plastics can be compromised by the presence of excessive amounts of moisture. In the pellet molding process, for example, residual moisture reacts with the molten polymer and thus deteriorates its physical and chemical properties. Therefore, the water content of polymers has to be checked to ensure appropriate product quality.

One commonly applied method for water determination in polymers is loss on drying (LOD). However, LOD does not determine the water content, but rather the total content of volatile components. Besides, the determination of the LOD is extremely time-consuming.

Метод: кулонометрическое титрование по Карлу Фишеру

В качестве альтернативы LOD, Metrohm предлагает кулонометрическое определение воды - технику, проверенную временем, которая доказала свою ценность в бесчисленных применениях.

Поскольку большинство полимеров нерастворимы, влага извлекается из образцов полимера под действием тепла, а испаряющаяся влага переносится в кулонометрическую ячейку потоком сухого газа-носителя. Так называемая методика с использованием печи является хорошо отработанной методикой подготовки образцов при титровании по Карлу Фишеру и рекомендуется в различных нормах (например, ASTM D 6869-03 или ISO 15512).

> Подробнее об этой теме читайте в пресс-релизе

> Узнайте больше об автоматизированном кулонометрическом титровании Карла Фишера

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БИК-спектроскопия: быстрая и неразрушающая

Хотя кулонометрическое определение воды является золотым стандартом для определения влажности в пластмассах, БИК-спектроскопия может быть быстрой и неразрушающей альтернативой. Для демонстрации, мы разработали приложение для определения воды в контактных линзах.

> Подробнее о Metrohm NIRSystems

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Halogens and sulfur in polymers: Combustion Ion Chromatography

When organic materials containing halogens and sulfur undergo combustion, they develop toxic, hazardous gases. To eliminate this risk in case of a fire, some plastics have to be checked in view of their halogen and sulfur content. Determining these parameters should be as reliable, accurate, and – not least – time-saving as possible.

Combustion Ion Chromatography (CIC) is a highly suitable method for this purpose. In this inline technique, the sample undergoes pyrohydrolytic combustion and the compounds of interest are turned into gaseous form and directly absorbed by a solution. This solution is then analyzed by ion chromatography. The coupling of the digestion and the analysis instrument allows you to increase sample throughput as well as the precision and correctness of the results.

CIC is highly reliable – testing has shown a recovery rate between 99% and 102.4% (using a certified polyethylene granulate containing known quantities of chlorine, bromine, and sulfur, see TA-049 below).

CIC in quality testing of halogen-free electrical cables and wiring

Nowadays, halogen-free (also known as zero-halogen) electrical cables and wiring are increasingly used. DIN EN 62321-3-2 stipulates CIC for determining total bromine in electric and electronic products. CIC is a helpful tool for determining whether the investigated polymers comply with laws, standards, and requirements (IEC 60502-1, RoHS, etc.).

> Learn more about combustion ion chromatography

> Browse more combustion ion chromatography applications for polymers

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Voltammetry: Determination of residuals and impurities

Voltammetry is a versatile technique that determines electrochemically active substances, e.g., inorganic or organic ions but also neutral organic compounds. Users benefit from a wide range of applications and at the same time from comparatively low investment and operation costs, short analysis times, and high precision and sensitivity.

Остаточные мономеры: стирол в полистироле

После полимеризации стирола в конечном продукте все еще могут присутствовать небольшие количества токсичного канцерогенного стирола. Поэтому необходимо определить остаточное содержание стирола в полистироле. Это можно легко сделать с помощью вольтамперометрии.

> Узнайте больше о вольтамперометрии

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Metal impurities in plastics

Voltammetry is capable of determining metals in any plastic. For voltammetric analysis, the plastic samples have to be prepared in order to remove the organic components. Typically, this is done via mineralization (microwave digestion), combustion, or, alternatively, via extraction (with a mineral acid). This same procedure can of course also be applied to raw materials (read more here).

Examples of metals that can be voltammetrically determined in PET include:
  • antimony,
  • cobalt, and
  • titanium.

> Learn more about voltammetry

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Сдвигая границы с проводящими полимерами

In general, synthetic polymers are isolators. However, if they possess an extensive π electron system, they can (semi)conduct electricity.

The most common conducting polymer (CP) materials are polyaniline, polypyrrole as well as polythiophene and its derivatives. By incorporating doping ions or substituents, metal-like conductivities and other exceptional properties are obtained – from organic light-emitting diodes (OLEDs) to polymer solar cells or conducting polymer-based supercapacitors devices and electrodes. To investigate the electrochemical properties of the conducting polymers or of polymer electrolytes during electrodeposition, in-situ measurements such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry are required. In these leading-edge technologies, researchers all over the world rely on Metrohm Autolab instruments.

> Learn more about electrochemistry from Metrohm Autolab

Further applications and products

End-group titration in polymers and resins

Today’s polymers and resins are produced with tailor-made properties. In the context of structure and property, functional groups play a decisive role, which is why the acid number and the hydroxyl value are often determined.

Read the application Read more about this on the Feedstock QC page

Webinar: Titration Solutions for Difficult Polymer Samples

If you're interested in moisture as well as hydroxyl and acid number titration of difficult polymer samples, then you should watch this webinar.

Go to the webinar

Titration for monitoring enzymatic degradation of bioplastic

Bioplastics are either biobased or biodegradable or both. Polyhydroxybutyrate (PHB) is both. The polyester is a polymeric storage substance of bacteria that is enzymatically degraded at a later stage. The enzymatic PHB degradation can be effectively monitored with acid-base titration.

Read more about biosynthetic and biodegradable PHB