Thermal Analysis of Medical Materials
On Demand Webinar

Thermal Analysis of Medical Materials

On Demand Webinar

This webinar presents thermal analysis techniques used to characterize medical materials

Medical materials
Medical materials

Medical materials and compounds can be characterized using various thermal analysis techniques. Thermal Analysis is an excellent method of testing many different chemical and physical properties such as the glass transition temperature, moisture content, composition, long-term stability and a material’s behavior during decomposition. Such analyses give the producers confidence that their products are made to the right standard and are uncontaminated.

The importance of quality testing in the healthcare industry

Continuing developments in medical science have revolutionized human healthcare. The goal of human healthcare is not only the treatment of disease and injury but also the diagnosis and prevention of potentially harmful conditions. Medical products can only serve their purpose if adequate quality control measures are implemented.

In recent years, there has been an increase in the use of thermal analysis techniques in medicine-related fields such as the production of medical devices, research into and development of new medical products and the production of medical supplies. This is particularly relevant to the testing of wound care and other dermal and oral treatment products.

Thermal analysis of medical materials

The most important effects that can be analyzed by DSC are the melting point, melting range and melting behavior.

DSC is also used to determine the heat of fusion, purity, polymorphism, the glass transition, and oxidation stability.

The main applications of TGA are evaporation, desorption and vaporization behavior, thermal stability, decomposition kinetics, and the analysis of composition.

TMA is normally used to study the expansion or shrinkage of materials and the glass transition and Coefficient of Thermal Expansion, CTE.

DMA is the most sensitive method for characterizing the glass transition of materials, crystallization behavior and is often used for studying the effects of humidity on materials, such as wound dressings.

English

Thermal Analysis of medical materials

Slide 0: Thermal Analysis of medical materials

Ladies and Gentlemen,

Welcome to the METTLER TOLEDO webinar on the “Thermal Analysis of medical materials”.

 

In the healthcare industry, quality testing of products, materials and ingredients is vital since incorrect or contaminated products could have a detrimental effect on the health of a patient undergoing treatment.

 

Thermal Analysis is an excellent method of testing many different chemical and physical properties such as the glass transition temperature, moisture content, composition, long-term stability and also a material’s behavior during decomposition. Such analyses give the producers confidence that their products are made to the right standard and are uncontaminated.

 

During the course of this webinar, I would like to describe a selection of interesting application examples that demonstrate the usefulness of thermal analysis in the healthcare industry.

 

Slide 1: Contents

This slide lists the topics I want to cover.

 

I will first discuss the most important effects and properties that can be investigated by thermal analysis in the healthcare industry and the techniques used to measure them.

 

The techniques discussed here include:

Differential Scanning Calorimetry or DSC as it is usually called;

Thermogravimetric Analysis, or TGA;

Thermomechanical Analysis, or TMA and

Dynamic Mechanical Analysis, or DMA.

 

With each technique I shall present a number of examples that illustrate how thermal analysis can be used to qualify medical products.

 

Finally, I shall summarize the different thermal analysis techniques and their application fields and list a number of useful references for further information and reading.

 

Slide 2: Introduction

Continuing developments in medical science have revolutionized human healthcare. The goal of human healthcare is not only the treatment of disease and injury but also the diagnosis and prevention of potentially harmful conditions. Medical products can only serve their purpose if adequate quality control measures are implemented. In recent years there has been an increase in the use of thermal analysis techniques in medicine-related fields such as the production of medical devices, research into and development of new medical products and the production of medical supplies. This is particularly relevant to the testing of wound care and other dermal and oral treatment products.

 

During the seminar, I will present thermal analysis applications from the previously mentioned fields. Please note that information for pharmaceutical applications can be found in the ‘Thermal Analysis in the Field of Pharmaceuticals’ webinar.

 

Slide 3: Industries and Applications

Thermal analysis is widely used and unsurprisingly, it finds applications in many fields within the medical industry.

 

The table summarizes different applications which generally fall into two categories. In research and development, thermal analysis is used to check that products and compounds will have suitable properties for their application, for example, the effect of time, temperature and moisture on use and storage properties. The other category of quality control checks materials used in medical supplies and medical devices. Such testing includes the determination of purity of a substance, the level of crystallinity, glass transition temperatures and compositional analysis. The moisture content and influence of relative humidity can also be studied.

 

Slide 4: Thermal Analysis

But let’s start at the beginning. What exactly is Thermal Analysis?

 

The ICTAC definition of thermal analysis is:

“A group of techniques in which a physical property of a substance is measured as a function of temperature whilst the substance is subjected to a controlled temperature program”.

 

The schematic diagram on the right shows a simple temperature program with isothermal and linear segments.

 

The lower half of the slide illustrates typical events and processes that occur when a sample is heated, for example, the melting process at which the sample changes from the solid to the liquid state, and oxidation; where a sample exposed to air or oxygen will start to oxidize and finally decompose.

We use thermal analysis techniques to investigate all of these effects.

 

 

Slide 5: Thermal Analysis                                             Techniques  

 

This slide shows the most important thermal analysis techniques used to characterize medical materials and compounds, namely:

 

Differential Scanning Calorimetry, or DSC dee ess see. This is the most widely used thermal analysis technique. The picture shows a DSC sensor with a sample (colored red) and reference crucible.

Thermogravimetric Analysis, or TGA tee gee ay. The picture shows the sample (colored red) and is contained in a pan which is attached to the balance mechanism.

Thermomechanical Analysis, or TMA tee em ay. Here we see the sample (colored red) positioned between the fixed and moving quartz probes.

Dynamic Mechanical Analysis, or DMA dee em ay. The picture shows one of the several available sample clamping assemblies, in this case compression mode.

 

I will explain these techniques in more detail in the following slides and describe some application examples.

 

 

Slide 6: Differential Scanning Calorimetry (DSC)

Let’s begin with DSC. This technique allows us to determine the energy absorbed or released by a sample as it is heated or cooled. There are several different types of DSC instruments:

 

The standard METTLER TOLEDO DSC 1 measures from minus one hundred and fifty degrees Celsius (–150 °C) to plus seven hundred degrees (700 °C) at heating rates of up to three hundred Kelvin per minute (300 K/min). Samples are normally measured in small crucibles made of aluminum, alumina or other materials using two to twenty milligrams of sample.

 

The METTLER TOLEDO Flash DSC 1 expands the heating rate to an amazing two million four hundred thousand Kelvin per minute (2,400,000 K/min) and the cooling rate to two hundred and forty thousand Kelvin per minute (240,000 K/min). To achieve this, the Flash DSC 1 uses very small sample sizes of about one hundred nano-grams (100 ng) and no sample crucibles - the sample is in direct contact with the sensor. The ultra-fast heating and cooling rates allow the simulation of industrial process conditions where materials undergo extremely rapid heating or cooling.

 

Another powerful DSC technique is high-pressure DSC, or HPDSC for short. The METTLER TOLEDO HP DSC 1 can analyze samples under inert gas or reactive gas atmospheres at pressures of up to ten mega-pascals (10 MPa). This suppresses undesired vaporization of samples or enables the stability of samples to be studied under increased oxygen pressures.

 

The schematic curve on the left shows a typical DSC measurement curve of a semi-crystalline polymer. Exothermic effects (heat evolved) point in the upward direction and endothermic effects (heat absorbed) downward. The features seen on the curve are interpreted and explained in the table on the right, they are:

One, the initial deflection or start-up transient of the DSC (due to sample and crucible heat capacity);

Two, the baseline where no thermal effects occur;

Three, a glass transition with enthalpy relaxation;

Four, cold crystallization;

Five, melting of the crystalline fraction; and finally

Six, oxidative exothermic decomposition.

 

 

Slide 7: Differential Scanning Calorimetry (DSC)

DSC is used to study the thermal behavior of materials, in particular physical transitions and chemical reactions. Most of the events involved are related to enthalpy changes observed with increasing or decreasing temperatures.

 

The table summarizes the DSC applications that are most used to characterize medical materials.

The main applications concern melting and crystallization behavior and polymorphism in medical compounds. DSC measurements additionally provide information about transition enthalpies and specific heat capacities. Finally, evaporation and chemical reactions are also important medical applications of DSC as they can be used when assessing shelf life.

 

The picture on the right of the slide shows an open DSC furnace with sample and reference crucibles.

 

Slide 8: Application 1: DSC                                 Phase transitions

The first DSC application example illustrates the interaction of several flavonoids with a model membrane. Flavonoids are medically active molecules with different biological effects, such as antiviral, anti-inflammatory or anti-oxidative activity. The model membrane used here is DPPC or dipalmitoylphosphatidylcholine. It is a phospholipid and consists of a lipid bilayer. The incorporation of flavonoids into the DPPC and the resulting liposomes of the DPPC model membrane can be used as drug delivery systems. The incorporated flavonoids alter the fluidity of the DPPC membrane and change the transition temperatures from the gel phase to the liquid crystalline phase of the DPPC matrix.

Four different flavonoids with different structures and incorporation rates were prepared in the DPPC matrix. The figure shows DSC curves of the main transition from the gel phase to the liquid crystal phase of the DPPC. It can clearly be seen that the various flavonoids influence the transition temperatures of the membrane material and these can be used to study the quality of the interaction and the incorporation into the drug delivery system. 

Slide 9: Application 2: DSC                                                    Stent

In recent years PLA or polylactide has established itself as a valuable material for medical implants that benefit from being biodegradable. The implants are used as plates, screws, pins or stents. The desired effect for these implants should be to remain in the body during the healing process, followed by slow disintegration once the healing is complete. Different types of PLA are used, in order to match the implant’s degradation time to the healing time, which can take between several months to several years. The two main factors that determine how long the material will remain intact before degradation are the chemical composition and the level of crystallinity.

 

In the present slide an example is shown for a DSC measurement of a PLA stent, used to keep arteries open. The glass transition temperature and the crystallinity provide information on the chemical composition of the material. The DSC measurement is a quick and simple test that gives the glass transition temperature and the crystallinity from a small amount of material. Once these parameters have been correlated to the implant’s degradation time, it is a simple matter to check how any formulation shall perform when implanted in the body.

 

Slide 10: Application: DSC-Photocalorimetery               UV Curing

The slide shows the curing behavior of a dental filling material where the cure process is effected by the use of blue light. Modern tooth fillings consist of materials that have a low viscosity when prepared, making them easy to apply to the tooth cavity and form to the desired shape. As soon as they are in place they can be rapidly cured with the application of visible or UV light. The graph shows DSC Photocalorimeter curves for the first and second exposures for three different exposure times. The curves in the upper right of the diagram correspond to the difference between the first and second exposure curves. It shows the actual degree of cure of the system.

The figure shows that the curing is very fast. The optimal curing time and the degree of cure can thus be tested very easily and quickly using a DSC instrument with a UV or visible lamp accessory.

 

 

Slide 11: TGA/DSC

Now let’s turn our attention to thermogravimetric analysis, or TGA.

In this technique, the mass of a sample is continuously measured as it is heated in a defined atmosphere. We simply put a few milligrams of the sample into a crucible, heat it and continuously record the weight change. This allows us to obtain information about the composition of the sample.

The schematic curve on the left shows the typical TGA measurement curve of a medical preparation. The different effects are numbered next to the curve and explained in the table. These are:

One: heating begins, and volatile components such as moisture and residual solvent, if present, vaporize;

Two: loss of water of crystallization;

Three: at about three hundred degrees Celsius, the sample undergoes decomposition;

Four: inorganic fillers or ash remain.

 

The METTLER TOLEDO TGA/DSC instruments can simultaneously measure heat flow, just like a DSC which can be very useful in determining the cause of weight loss or gain.

 

Slide 12: Thermogravimetric Analysis (TGA)

 

The picture on the right shows a view of the open furnace of a TGA/DSC instrument, and in particular the sample holder with positions for the sample and reference crucibles. The standard crucibles are made of alumina.

 

The adjacent table summarizes the main analytical applications of TGA for medical materials. TGA is mainly used to investigate the composition of materials and to quantify processes such as vaporization, sorption or desorption. It allows us to check the thermal stability of materials and their reaction kinetics.

 

The combination of TGA with a mass spectrometer, combined gas chromatograph–mass spectrometer or a Fourier-transform-infrared-spectrometer allows us to analyze gaseous compounds evolved from a sample. This provides information about the nature of the sample and when combined with DSC data, it gives a powerful tool for the analysis of many substances. .

 

 

Slide 13: Application 1: TGA/DSC                         Biological tissue

In the current application, TGA measurements of artificial bone and cartilaginous scaffolding materials are shown. The two scaffolding materials are combined to form implants to replace damaged articular cartilage which normally heals at a very slow rate.

 

The slide shows the TGA curves of both individual scaffolding materials and their first derivatives or DTG curves. Both scaffolding materials are made from collagen/chitosan mixtures with additional mineral filler added in the bone scaffolding to achieve extra mechanical strength

 

Both scaffolding materials essentially exhibit three mass loss steps, the first of which is due to the loss of moisture. The following two steps result from the decomposition of chitosan and then collagen.

 

The cartilaginous scaffolding material has no residue content left after the complete decomposition of the organic components. The bone scaffolding material has 55% inorganic residue left, the same amount of inorganic content in human bones. With the help of several TGA measurements, the artificial bone scaffolding material mixing ratio was adjusted so that the scaffolding material composition exactly matched that of the human bone composition.

 

Comparison of the first derivative curves in the lower part of the figure shows that the decomposition of the organic constituents in the bone scaffolding material commences at higher temperatures compared to the cartilaginous layer. This is probably due to a stabilizing influence of the inorganic filler material interacting with the collagen and chitosan.

 

Slide 14: Application 2: TGA/DSC                                     Moisture

The current slide shows a TGA measurement of absorbable surgical suture. Absorbable suture disintegrates in the body and has the advantage that it need not be removed when healing is complete. There are several different mechanisms for absorption of the suture by the body. In one instance the fiber hydrolyses when it comes into contact with water present in the tissue. For this to occur, the suture should only come into contact with water once it is in the tissue and not before. Production and storage of the suture should therefore exclude as much water as possible. Determination of the moisture content of a new suture pack is an important quality control criterion.

One easy way to determine the water content of newly unpacked sutures is by thermogravimetric analysis. The slide shows measurement of the freshly unwrapped surgical suture, heating from room temperature up to 700 degrees Celsius. Above 200 degrees the suture decomposes, which is visible from percentage weight loss step evaluations shown in blue. More important in this case is the loss of moisture occurring below circa 160 degrees Celsius, which is evaluated in green. This is the water content of the suture and is shown to be only about 0.1 percent of the total mass. This result was independently confirmed by Coulometric Karl Fischer titration experiments.

Slide 15: Thermomechanical Analysis (TMA)

We now move on to thermomechanical analysis, or TMA. This technique measures the dimensional changes of a sample as it is heated or cooled.

 

The schematic curve on the left shows results from a typical TMA measurement on a sample mounted in compression, with a small load applied. The two main effects are numbered next to the curve and explained in the table. These are:

One: expansion below the softening point;

Two: softening with plastic deformation under the influence of the applied load.

 

Slide 16: Thermomechanical Analysis (TMA)

The table summarizes different analytical applications of TMA for medical materials.

 

The main application is the measurement of length changes due to heating or cooling, and in particular the determination of the coefficient of thermal expansion or CTE.

 

The technique is also excellent for determining glass transition temperatures, for studying softening behavior – especially for thin layers or coatings – and for observing polymorphism. Measurements of the swelling of materials in solvents can also be performed.

 

The picture on the right shows a typical TMA configuration where a ball-point probe is in contact with a blue sample resting on a flat support. The probe penetrates the sample as it softens.

 

Slide 17: Application 1: TMA                       Softening & Thickness

 

Multilayer packaging films used in the medical industry need to fulfill a wide range of requirements, such as the extension of shelf life, protection during transportation, provision of barrier functionality, tear resistance, sales appeal, and so on.

 

In order to meet all of these needs, modern packaging materials consist of various different thin polymer layers bonded together to form a multilayer film, which then provides the required properties that cannot be obtained from a monolayer film alone. Since the individual polymer layers exhibit different melting points or temperatures, information about the different layers can be obtained from thermomechanical analysis.

 

This slide presents the results of the analysis of a zero point one millimeter (0.1-mm) multilayer film. The TMA curve was measured using a compressive force of zero point one newton (0.1 N) and a heating rate of five Kelvin per minute (5 K/min). The results of this measurement were used to determine the thickness of the individual layers of the multicomponent film. The identification of the different layers was performed using the melting peaks in the first derivative of the TMA curve. The melting temperatures 106, 118, 178 and 189 degrees Celsius, indicate the presence of low density polyethylene, linear low density polyethylene, polyamide 12 and polyamide 11, respectively. The melting peaks in the first derivative can be integrated to obtain the layer thickness of the individual components in the film. A check on accuracy can be made by adding the individual thicknesses to see that they total to the original value. Here the answer is +0.5 microns, which is acceptable due to thermal expansion that has occurred on heating.

 

The evaluation of the two linear low density polyethylene layers around 120 degrees Celsius (120 °C) is difficult because the peaks overlap one another. The double peak obtained cannot be resolved which indicates that the multilayer film contains two separate linear low density polyethylene layers of similar thickness. The inserted microscopic cross sectional image confirms the TMA measurements of the individual film thicknesses.

 

Slide 18: Application 2a: TMA              Glass transition & Softening

Nowadays adhesives are increasingly used in many industrial applications and this is also true in medical practice. Adhesive bandages or plasters are stuck to the skin with adhesive, simple wounds are glued together for fast closure, artificial joints are cemented in place using bone cement and new applications are continually emerging.

 

This slide shows both TMA and DSC measurements of an adhesive from -80 degrees to 170 degrees Celsius. The black, upper curve is the TMA measurement, the lower, red, curve is the DSC measurement. The most prominent effect is the softening, which starts at about thirty degrees Celsius. In the TMA measurement the probe penetrates into the sample and the sample height decreases. In fact, two different softening steps are observed. The first occurs at about forty eight degrees Celsius, the second at about one hundred and one degrees Celsius. The results are confirmed by the red DSC curve, where a very broad melting process can be observed over the whole softening temperature range.

 

At lower temperatures, the adhesive exhibits a very clear glass transition in the DSC trace at about -minus 36 degrees Celsius, exhibiting the typical heat capacity step seen at Tg. The TMA curve shows a small change in the rate of expansion of the sample (for the scale plotted- see next slide), with the onset observed at minus 36.6 degrees Celsius, a difference of about 0.8 degrees Celsius, which is typical between measurements from these two instruments (note: DSC Tg determined at 10 degrees Kelvin per minute).

 

 

 

Slide 19: Application 2b: TMA-DLTMA         Gel Point of Adhesive

The same TMA curve as that shown in the previous slide is now displayed in an expanded scale from -100 to 30 degrees Celsius to emphasize the glass transition, Tg and the sol point. The adhesive becomes rubbery after Tg, but only flows significantly once the gel structure has broken down, sol point.  In the previous slide this was only visible as a small effect due to the scale chosen.

 

The material analyzed here is a thermoreversible gel, it can change from liquid to solid on cooling and solid to liquid on heating, as opposed to a thermoset material that forms irreversible crosslinks as it gels and then cures.

 

Dynamic Load TMA or for short, DLTMA was used to analyze this sample. With DLTMA a constant magnitude alternating load is applied to the sample probe and as the sample softens the resultant amplitude increases.

 

The upper curve shows the results of the DLTMA measurement. In this measurement, the force changes periodically between plus zero point one (+0.1) to minus zero point one newton (–0.1 N). The sol point is reached when the resultant amplitude becomes much larger. For the measured adhesive this means that the usable range is between zero and about 40 degrees Celsius.

 

Slide 20: Application 3: TMA                        Swelling & Dissolution

Capsules and tablets are often coated with polymers that swell and become permeable in gastric fluid to release the drugs contained within the tablet. The swelling behavior can be studied using the TMA swelling accessory as is shown in the upper right corner of the slide.

 

As an example, a slice of a soft, gelatin-based capsule coating was measured in a salt solution that was adjusted to have a pH of around 2.5, which is equal to the pH in the stomach.

 

At time zero, the measurement was started and liquid was simultaneously injected into the TMA swelling accessory containing the gelatin shell taken from the capsule. The thickness of the gelatin shell increases with time, due to the uptake of liquid. The expansion of the gelatin in the acidic salt solution reaches maximum after about fifteen minutes, after which time the film starts to dissolve and becomes permeable. This can be observed in the TMA curve as a decrease in the thickness.

 

Slide 21: Dynamic Mechanical Analysis (DMA)

Dynamic Mechanical Analysis is a technique that is used to measure the mechanical properties of a viscoelastic material as a function of time, temperature and frequency when the material is deformed under a periodic oscillating stress.

 

The schematic diagram on the left shows the results of a DMA measurement of a crash-cooled semicrystalline polymer. The curves display the storage modulus, gee prime, the loss modulus, gee double prime, and the loss factor tan delta as a function of temperature.

 

The different events seen in the curves are numbered next to the curve and explained in the table. They are:

One: secondary relaxation, observed as a peak in the tan delta curve and a small drop in the storage modulus curve, gee prime;

Two: the glass transition, seen as a reasonably large peak in the tan delta curve and as a decrease in the storage modulus curve, gee prime;

Three: cold crystallization of the polymer. The stiffness and hence the storage modulus, gee prime, increase, together with some activity in tan delta.

Four: recrystallization accompanied by a peak in tan delta and frequently a rise in gee prime;

Five: melting of the crystalline fraction with a drastic decrease in both the storage modulus, gee prime and loss modulus, gee double prime.

 

Slide 22: Dynamic Mechanical Analysis (DMA)

The table lists the main analytical applications of DMA for medical materials.

 

In general, DMA provides information about the viscoelastic behavior of amorphous components, for example the glass transition, Tg and sub-Tg relaxations.  It can be used to determine the elastic modulus, loss modulus and damping factor.

 

DMA gives information on the softening temperature, and is used for assessing the miscibility of polymer blends and the dynamic mechanical behavior of polymer coatings and coating materials.

 

It is also widely used in a controlled humidity environment to study the effect of moisture on material properties.

 

The picture on the right shows a sample installed in the DMA ready for measurement in a bending mode.

 

Slide 23: Application 1: DMA                                                 Melting/Crystallization

DMA analysis can give valuable information during the development of new materials. The current example, shows a study of the influence of copolymer composition on its mechanical properties. This slide shows the DMA analysis of a copolymer of poly--caprolactone and polytetrahydrofurane or PCL-PTHF. This copolymer is a candidate for a new orthopedic cast material.

 

Traditionally, plaster of Paris is used to immobilize limbs during the healing of bone fractures. The disadvantage of plaster of Paris is that it weakens when it becomes wet, whilst the new material studied here is unaffected. Its melting temperature of 60 degrees Celsius would suggest that it is too hot to apply to human skin. However because it only solidifies with significant supercooling, the material can be applied safely to the skin at temperatures of around 30 degrees Celsius. After it has solidified on the skin it remains stable up to a higher temperature. The degree of supercooling depends on the mixing ratio of the poly--caprolactone and polytetrahydrofurane.

 

The results on the slide show the levels of rigidity and resultant limb support for different mixing ratios as measured in the DMA in shear mode. The storage modulus of the different composition materials was first measured during heating up to 80 degrees, showing the softening of the material occurring as it melts at around 60 degrees. After a short isothermal segment, the materials were cooled to -20 degrees to observe the degree of supercooling required to initiate crystallization.

 

With increasing polytetrahydrofurane content two effects are observed: the modulus value of the copolymer in the crystalline state decreases, meaning that it can be more flexible and the supercooling becomes more pronounced, shifting the crystallization of the copolymer to lower temperatures and thus allowing application to broken limbs at ambient temperatures. 

 

Slide 24: Application 2: DMA Multiple frequency shear measurement

This slide shows a DMA analysis of nitrile rubber gloves in shear mode. The DMA curves show a temperature range from -80 degrees to 50 degrees Celsius. At the lower end of this range, the gloves have a very high modulus value of about 800 mega Pascal, where the material is in the glassy state. At around -50 degrees Celsius the material starts to soften until the modulus is reduced to a value of about 1 mega Pascal at room temperature; the material is now in the rubbery state and fit for use. The glove material softens as it goes through its glass transition, the glass transition temperature being the lowest temperature at which the rubber gloves can be used. For nitrile rubber gloves, the glass transition temperature and also the chemical resistance are determined by the amount of acrylonitrile groups in the nitrile rubber backbone. Both the glass transition temperature as well as the chemical resistance will increase with higher acrylonitrile content.

 

The DMA measurements were performed at three different frequencies of 1, 10 and 100 Hz. The frequency dependent measurements confirm that we are indeed seeing a glass transition in the measurement. Since the glass transition is a relaxation phenomenon, it will show frequency dependent values of Gee prime, gee double prime and tan delta during the transition.

 

Slide 25: Summary

The table summarizes the most important thermal events that characterize medical materials as well as the techniques recommended for investigating these effects. A box marked red means that the technique is recommended as a first choice; a box marked blue indicates that the technique can also be used.

 

The most important effects that can be analyzed by DSC are the melting point, melting range and melting behavior.

 

DSC is also used to determine the heat of fusion, purity, polymorphism, the glass transition, and oxidation stability.

 

The main applications of TGA are evaporation, desorption and vaporization behavior, thermal stability, decomposition kinetics, and the analysis of composition.

 

TMA is normally used to study the expansion or shrinkage of materials and the glass transition and Coefficient of Thermal Expansion, CTE.

 

DMA is the most sensitive method for characterizing the glass transition of materials, crystallization behavior and is often used for studying the effects of humidity on materials, such as wound dressings.

 

Slide 26: Summary

This slide gives an overview of the temperature ranges of the METTLER TOLEDO DSC, TGA, TMA and DMA instruments.

 

In general, DSC experiments are performed at temperatures between minus one hundred and fifty degrees Celsius and plus seven hundred degrees. The temperature ranges may be different if special equipment or accessories are used.

 

TGA measurements normally begin at room temperature. The maximum possible temperature is sixteen hundred degrees. For medical applications, the temperature range up to one thousand degrees is most important.

 

TMA experiments can be performed between minus one hundred and fifty degrees and plus sixteen hundred degrees.

 

DMA samples are measured in the range minus one hundred and fifty degrees to plus six hundred degrees and often under controlled humidity where the application involves body contact.

 

Slide 27: For More Information on Medical Materials

Finally, I would like to draw your attention to information about medical applications that you can download from the Internet. METTLER TOLEDO publishes articles on thermal analysis and applications from different fields twice a year in UserCom, the well-known METTLER TOLEDO biannual technical customer magazine. Back issues can be downloaded as PDFs from www.mt.com/ta-usercoms as shown at the bottom of the slide.

 

Slide 28: For More Information on Thermal Analysis

Additionally, you can download details about webinars, application handbooks or information of a more general nature from the internet address given on this slide and so ensure that you are always fully up-to-date in thermal analysis.

 

Slide 29: Thank You 

This concludes my presentation on thermal analysis in the field of medical materials. Thank you very much for your interest and attention.

Thermal analysis products are not medical devices and are intended for material research and quality control.

 
 
 
 
 
 
 
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