Thermal, Rheological and Basic Properties Laboratory

Thermal analysis by differential scanning calorimetry (DSC)

Differential scanning calorimetry is a thermoanalytical technique that measures the difference in the amount of heat required to increase the temperature of a sample and an inert reference as a function of temperature. Both the sample and the inert reference are maintained at the same temperature throughout the experiment by a controlled temperature program. This technique can be used to evaluate chemical reactions (such as thermal degradations or oxidation processes), identification of primary transitions (melting and crystallization processes), and second-order transitions such as glass transitions which can occur in the sample under certain analysis conditions. Tests are conducted according to ISO 11357 standards.

The LATEP has a highly sensitive Mettler Toledo DSC3+ system that operates within a temperature range of -150 to 700 °C.

Thermogravimetric analysis (TGA)

Thermogravimetric analysis is a method in which changes in physical and chemical properties of materials are measured as a function of increasing temperature ramp (with constant heating rate), generally extended to its decomposition temperature. The weight loss curve (TGA) and its first derivative (DTGA) is used to evaluate the weight loss of a sample.

Most of TGA curves show weight loss, which it is associated to chemical reactions (decomposition and separation of crystallization water, combustion, reduction of metallic oxides) and physical transformations (evaporation, vaporization, sublimation, desorption, drying). Exceptionally, weight gains may be observed due to reactions with gaseous components of the purge gas yielding non-volatile compounds, adsorption of gaseous products in the samples. Tests are conducted according to ISO 11358 standards.

The LATEP is equipped with a robotic TGA/DSC1 (model: SDT650) from TA Instruments, capable of operating from room temperature up to 1500 °C.

Heat deflection temperature (HDT)

The heat deflection temperature (HDT) is the temperature at which a specimen of plastic material, that is rigid at room temperature, deforms under a specified load (0.45, 1.8 or 8.0 MPa) as a consequence of a controlled increasing temperature ramp (heating rate of 50 or 120 °C/h). This method can only be applied to materials which are rigid at room temperature. The test procedure is described in ISO 75 and ASTM D648 standards.

LATEP has a HDT6/VICAT equipment from Ceast. This instrument has six independent test stations, and works in a temperature range from room temperature to 300 °C.

VICAT softening point

Vicat softening point is the temperature at which a standard indenter (3 mm long, circular cross section, and area 1.000 ± 0.015 mm²) penetrates 1 mm into the surface of a plastic test specimen, that is rigid at room temperature, under definite load conditions (10 N or 50 N) and when the temperature is raised at a uniform rate (50 ºC/hour or 120 ºC/hour). The test procedure is described in ISO 306 and ASTM D1525 standards.

LATEP has a HDT6/VICAT equipment from Ceast. This instrument has six independent test stations, and works in a temperature range from room temperature to 300 °C.

Melt flow index (MFI)

Melt flow index is defined as the mass of polymer, in grams, flowing in ten minutes through a nozzle of a specific inner diameter (2.095 mm) and length (8 mm) under certain conditions of stress and temperature.

The value of the melt flow index depends on the molecular structure of the polymer (molecular weight, molecular weight distribution, degree of chain branching, etc.). This value is an indirect measure of molecular weight. The melt flow index, along with the analysis of possible distortions at the extrudate will determine the processing method for the polymer. The testing procedure follows ISO 1133 standards.

LATEP has two plastometers: one from CEAST, operating between 23-400 °C, and another from ZWICK/ROEL, operating between 50-550 °C.

Capillary Rheometry

Rheology studies the relationship between force and deformation in a material. Capillary rheometer is designed for characterizing polymer melts at high shear rates and it is the most effective instrument for measuring shear viscosity at high shear rates. The polymer melt is forced through a capillary of known dimensions. Knowing the dimensions, the flow-rate can be converted into a value for the shear rate and the pressure drop into a value for the shear stress. The true stress – true shear rate curve of the polymeric material under study can be determined. These tests are carried out outside the limits of linear viscoelastic region (LVR) and the capillary flow process resembles many industrial processes such as extrusion and injection moulding. The test procedure is described in ISO 11443 standard.

The LATEP features an RH2000 capillary rheometer from Malvern Instruments, with a temperature range of 25 – 500 °C and an extrusion speed of up to 600 mm/min.

Dynamic Rheology

Rheology studies the relationship between force and deformation in a material. Oscillatory rheometer is a versatile equipment to study polymers in the melt state. It can perform tests in oscillation, flow or creep modes. This kind of rheometer allows to work in the linear viscoelastic region (LVR) or outside the limits of LVR. In this equipment, the specimen is held between two parallel plate. The specimen is subjected to a sinusoidal torque. In the oscillation mode, the viscoelastic properties of a material are determined from the measured torque, the displacement, and the specimen dimensions. The test procedure is described in ISO 6721 standard.

LATEP has an oscillatory rheometer with a parallel-plate geometry from TA Instruments (model DHR-2) which works in the angular frequency range from 0 to 300 rad/s. Also, the rheometer has an environmental test chamber (ETC) accessory which employs a combination of radiant and convective heating and has a temperature range of 23 °C to 600 °C.

Fourier transform infrared spectroscopy (FTIR)

Infrared spectroscopy is a relevant tool for the identification of a polymer through the study of its vibration spectrum after the interaction with infrared radiation. The vibration frequency depends on the chemical nature of the atoms involved in the vibration, and on the vibration mode (stretching or bending). Infrared radiation wavelengths extend from 1.0 mm to 714 nm (10-4000 cm^-1), although the most commonly used is the mid-wavelength infrared, between 2.5 and 20.5 μm (4000-400 cm^-1).

The LATEP is equipped with a Nicolet iS50 FT-IR spectrophotometer from Thermo Fisher Scientific, capable of operating in transmission mode or attenuated total reflectance (ATR) mode, with a working range of 7000 to 400 cm^-1.

Spectrophotometer for color, gloss, fluorescence, and hue measurement

Used for measuring and analyzing the color of surfaces and materials to ensure color consistency in manufactured products.

The LATEP uses a Color2view pro X spectrophotometer from BYK, with a gloss measurement range of 20º to 60º, color geometry of 45°c:0°, and a fluorescence spectral range of 300 – 760 nm. The test procedures follow ASTM E 313 and ASTM D 2457 standards.

Spectrophotometer for transparency and haze measurement

Measuring the transparency and "haze" of transparent and translucent materials is crucial in many industrial sectors. This property is essential for materials like glass, plastics, and films used in applications requiring optical clarity, such as screens, windows, and packaging.

The LATEP uses a Haze-gard i spectrophotometer from BYK with a measurement range of 0 – 100 %, following the ASTM D 1003 standard.

Scanning Electron Microscope (SEM) with SED and EDX detectors

The SEM is an advanced, versatile tool for material characterization and detailed surface analysis, ideal for examining the topography and composition of polymers, metals, ceramics, and composites.

The laboratory is equipped with a Phenom XL SEM from Thermo Scientific, providing images with up to 14 nm resolution, and features an EDS (Energy Dispersive X-ray Spectroscopy) system for elemental analysis.

Density

The density is a basic physical property of the material that is directly related to other physical properties and its final application.

LATEP has an hydrostatic balance to evaluate density by the immersion method. In this method, first of all the specimen is weighed in the air, and then the same specimen is dipped into water or ethanol to measure its apparent weight. These two measurements are compared to determine the density. The testing procedure follows ISO 1183 standards.

The laboratory is also equipped with an Industrial Physics Ray/Ran gradient column for determining polymer density.