Lab sessions in Polymer Technology

The unique molecular structure of polymers means that they can be processed by heating and thus be elastic and soft, or brittle and hard.
Processing is done by extrusion and injection moulding, fibre spinning and compression moulding. With these methods, we can study how different bioplastics can be used in different products.

Equipment

In processes for processing polymeric materials, the following instruments are used:

• Micro-compounder for processing small quantities of polymers (approx. 20 g/batch) into granules
• Injection moulding unit belonging to the micro‑compounder for producing test specimens for mechanical testing of plastic materials
• Double-screw extruder for the production of plastic mixtures, plastic film and plastic filaments for 3D printers, as well as the possibility of injection moulding test pieces for mechanical testing
• 3D printer with double filament nozzles, for additive manufacturing of plastic components
• Hydraulic press for moulding smaller plates (20x20 cm) from various polymers and mixtures
• Piston spinning machine for the production of mono- and multifilament fibres from polymers and their mixtures, the equipment can be used for cold and hot elongation of the fibres, which can be used for the production of textile materials by weaving or knitwear manufacturing

Research in Polymer Technology develops and studies polymeric materials for a circular bioeconomy. This includes plastics, composites, textile fibres and textile structures, which are studied in terms of manufacturing and processing, properties and use, as well as recycling.

Tensile testing is a basic materials science and engineering test that measures a material's resistance to applied force. For thermoplastic polymers and composites, this test provides crucial data on their mechanical properties, including tensile strength, elongation, and modulus of elasticity.

This data is vital for:

• Choice of materials
• Design
• Quality control
• Research and development

Thermoplastic polymers and composites are used in a variety of applications, from the automotive and aerospace industries to consumer products. Understanding their tensile strength properties is crucial to ensure their performance and safety.

Skills and Expertise

Our team has a strong foundation in materials science, with a particular focus on polymer and composite behaviour. We are highly skilled at conducting tensile testing, including the operation of the necessary equipment and software. Our expertise extends to an in-depth understanding of relevant testing standards such as ASTM and ISO. In addition, we are proficient in interpreting stress-strain curves and analysing resulting test data. We also have hands-on experience in sample preparation and handling, ensuring accurate and reliable test results.

Available equipment

• Universal Test Machines (UTMs): These machines apply controlled tensile forces to samples. They are equipped with load cells and extensometers to measure force and elongation
• Tools for sample preparation: Equipment for cutting, shaping and preparing samples to exact dimensions.

Analysis and testing

• Key parameters measured: Tensile strength, elongation, tensile modulus (Young's modulus)
• Test Standards: ASTM and ISO standards
• Types of analysis: Stress-strain curve analysis, statistical analysis of test data, fracture mode analysis, analysis of environmental impact on tensile strength properties.

Bending testing determines a material's ability to resist deformation under bending loads. It measures properties such as flexural strength and flexural modulus, which are essential for applications where materials are subjected to bending stresses.

This data is vital for:

• Choice of materials
• Design
• Quality control
• Research and development

A sample is placed on two support points, and a load is applied to a specific point between the supports (three-point bending). The force and deflection of the sample are measured. The data is used to calculate flexural stress and elongation, resulting in values for flexural strength and modulus. Thermoplastics and composites are used in various bending applications, such as beams, panels, and structural components. Bending testing provides crucial data to ensure the structural integrity and performance of these materials.

Skills and expertise

Our team has significant skills and expertise in material mechanics, with a specialized focus on bending behaviour. We are skilled in using bending testing equipment and data acquisition systems, ensuring accurate data collection. We have a strong understanding of relevant testing standards, including ASTM and ISO. Our capabilities extend to interpreting flexural stress-strain data and calculating crucial flexural properties. In addition, we have expertise in sample preparation, a critical aspect of achieving reliable and accurate test results.

Available equipment

• Universal Test Machines (UTMs): Configured with bending fixtures for three-point bending tests.
• Data Collection System: Software and hardware to record and analyse test data.

Analysis and testing

• Key parameters measured: Flexural strength, flexural modulus, deflection
  Test Standards: ASTM and ISO standards
• Types of analysis: Flexural stress-strain curve analysis, calculation of flexural strength and modulus, fracture position analysis, statistical analysis of test results, comparisons of flexural properties between different materials or under different test conditions.

Impact testing assesses a material's ability to withstand sudden impacts or shocks. It measures the toughness of the material, which is its ability to absorb energy before it cracks. This is vital for applications where materials are subjected to impact, such as automotive components, aircraft structures, sporting goods, and packaging.

This data is vital for:

• Choice of materials
• Design
• Quality control
• Research and development

A sample is subjected to a sudden shock from a pendulum or a falling weight. The absorbed energy during the impact is measured, for example, in Charpy impact tests. Thermoplastics and composites can exhibit varying impact resistance depending on their composition and structure. Impact testing ensures that these materials can withstand real-world impact scenarios, contributing to product safety and reliability.

Skills and expertise

Our team has a thorough understanding of impact mechanics and fracture behaviour. We are skilled at using impact testing equipment and data acquisition systems, ensuring accurate and reliable data collection. We have in-depth knowledge of relevant testing standards, including ASTM and ISO. Our capabilities extend to interpreting impact test results and analysing fracture surfaces to gain valuable insights. In addition, we have expertise in sample preparation, a critical aspect of ensuring consistent and accurate test results.

Available equipment

• Charpy Impact Tester: These machines use a pendulum to punch a notched sample. These machines drop a weight on a sample from a controlled height.

Analysis and testing

• Key parameters measured: Impact Strength, Fracture Mode
• Test Standards: ASTM and ISO standards
• Types of analysis: Measurement of impact energy.

Thermal analysis involves measuring the physical and chemical properties of materials as a function of temperature or time. It provides crucial information about a polymer's behaviour under varying thermal conditions.

• Differential scanning calorimetry (DSC): DSC measures the heat flow associated with transitions in materials as a function of temperature. It helps to determine glass transition temperature (Tg), melting point (Tm), crystallization temperature (Tc), enthalpy changes related to these transitions, hardening behaviour. DSC is vital for understanding how a polymer's structure affects its thermal behaviour.
• Thermogravimetric Analysis (TGA): TGA measures the change in a material's weight as a function of temperature or time. It helps determine thermal stability, decomposition temperatures, composition analysis (e.g., filler content, moisture content). TGA is essential for assessing a polymer's resistance to thermal degradation.

Skills and expertise

Our team demonstrates expertise in thermal analysis, which includes: accurate sample preparation, precise selection of experimental parameters (heating rates, atmospheres), accurate data interpretation, and a deep understanding of the relationship between thermal properties and polymer structure. We are also adept at combining DSC and TGA data to achieve a comprehensive material understanding. This expertise is supported by staff with strong backgrounds in polymer chemistry, materials science, and analytical chemistry.

Available equipment

• DSC instruments with precise temperature control and sensitive heat flow measurement capabilities.
• TGA instruments with high-resolution scales and ovens with controlled atmosphere.
• Data collection and analysis software.
• TGA instruments linked to FTIR to enable analysis of emitted gases.

Analysis and testing

• DSC: Determination of glass transition temperature (Tg) for amorphous polymers, measurement of melting point (Tm) and crystallinity grade of semicrystalline polymers, curing characterization of thermosetting plastics.
• TGA: Evaluation of thermal stability of polymers under different atmospheres (e.g. air, nitrogen), quantification of the amount of filler, additives or moisture in polymer formulations, oxidation induction time test (OIT).

This lab module focuses on the production of filled polymer composites through a two-step process that includes compounding and injection moulding. In the first step, the polymer matrix is mixed with different types of fillers (e.g. fiberglass, natural fibres, or minerals) using a double-screw extruder. This allows for a homogeneous dispersion of the fillers in the polymer and creates a reinforced mixture with improved mechanical and thermal properties. After that, the material is granulated and used in the second stage of injection moulding, where sample bodies or components are manufactured according to specific geometries.

Competence

• Experience in polymer processing and material development
• Knowledge of optimization of process parameters for compounding and injection moulding
• Ability to analyse material properties and perform mechanical and thermal tests

Equipment

• Double screw extruder for compounding
• Injection Moulding Machine for Sample Production
• Granulation Equipment

Analyses

• Tensile testing, impact testing and bending testing
• Thermal analyses (DSC, TGA)
• Microscopy for Evaluation of Filler Dispersion

In this lab phase, textile composites are manufactured by lamination of polymer matrices and textile reinforcement materials using hot pressing. The process involves the placement of textile reinforcements (e.g. glass fibre, carbon fibre or natural fibres) and impregnation with polymers (thermo- or thermosetting plastic). The material is then placed in the hot press where temperature, pressure and time are optimized to obtain a homogeneous and well-bonded composite. This method is particularly suitable for the production of planar panels and prototypes for structural applications.

Competence

• Expertise in textile composites and lamination techniques
• Experience in optimizing press parameters (temperature, pressure, time)
• Knowledge of mechanical and morphological properties of textile composites

Equipment

• Hot press for lamination
• Equipment for material preparation (cutting, pre-impregnation)

Analyses

• Mechanical tests (tensile, flexural and interlaminar shear)
• Microscopic analysis of fibre-matrix bonding
• Thermal and moisture resistance analyses