Thermal Analysis UserCom 15

Introduction

Toners, as used in modern laser printers and photocopiers are, in fact, complicated mixtures that consist of a thermoplastic base material to which different ingredients such as flowing agents, pigments, UV-stabilizers and other additives have been mixed. The glass transition temperature of the base material and the melting temperatures and melting enthalpies of the additives are characteristic for the toner. These properties can be easily and reliably determined by thermal analysis, in particular with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). This article describes how the two techniques were used to measure a toner sample, and compares the results and information obtained. The work was done with a DSC821^e and a DMA/SDTA861^e .

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Introduction

The Laboratoire d’Electronique de Technologie et d’Instrumentation (LETI) specializes in the application of photosensitive resins for lithographic processes in the semiconductors industry (transistors for integrated circuits). The ever-increasing miniaturization of transistors is the driving force behind numerous technological advances. Currently, the best possible resolution that can be achieved for isolated lines is 40 nm, and 60 nm for lines in dense patterns.

These limits are most probably due to the different resin components presently used. The current challenge is therefore to develop new resin formulations (chemically amplified resists or so-called CARs) that will allow a resolution of 20 nm to be obtained.

CARs are multi-component mixtures consisting of a polymer matrix (the combination of two polymers), a photo acid generator, PAG, and other additives, depending on the properties desired. In order to improve the properties of CARs, the production process has to be optimized. This in turn requires an understanding of the physicochemical behavior of each component of the CAR and its effect on the process. The LETI-LTM (Laboratoire de Technologie Microélectronique) and the “Laboratoire de Thermodynamique des Solutions et des Polymères” cooperate in this area of research. Temperature-modulated DSC (ADSC), FTIR and thickness measurement techniques are used to investigate the influence of the different resin components on resolution in the lithographic process. The main advantage of ADSC is that the glass transition temperature and the thermal effects associated with the lithographic process (vaporization and cross-linking) can be determined in one single measurement [1].

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Literature

[1] Resolution limit of negative tone chemically amplified resist used for hybrid lithography. Influence of the molecular weight. L. Pain, C. Higgins, B. Scarfoglière, S. Tedesco, B. Dal’Zotto, C. Gourgon, M. Ribeiro, T. Kusumoto, M. Suetsugu and R. Hanawa. Journal of Vacuum Sciences and Technology. B., 2000, 18(6), 3388.

Introduction

Plastic blends represent the largest fraction of plastic materials that occurs in the recycling of plastics from waste packaging. These mixed plastics consist mainly of polyolefines, i.e. polyethylene and polypropylene. For material recycling purposes, the fraction can be processed via dissolution. Recycling via dissolution is in fact a process that results in recycled material with properties superior to those obtained with the usual melting procedure [1].

To produce material of high quality with reproducible material properties, it will however be necessary to develop new methods that can separate the polyolefinic material into its individual components, i.e. into low-density (LDPE) and high-density polyethylene (HDPE), and polypropylene (PP) [2].

The composition of the recycled plastic is of course a measure of the efficiency of the separation. We have therefore developed a method to determine the composition of polyolefinic samples. The method uses DSC measurements and is particularly interesting in that it not only distinguishes between polyethylene and polypropylene, but also between high- and low-density polyethylene.

The basic principle of the method is to describe the melting enthalpies (measured in the melting curve) of a polyolefinic sample by the mass fractions (which follow from the sample composition) and the standard melting enthalpies of the components involved.

The melting curve of a mixture cannot however be described exactly by the sum of the pure melting curves. Correction factors have to be introduced. Theses are determined iteratively from the measurement results of a series of polyolefinic samples of known composition.

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Literature

[1] Klein, F., “Verfahrensentwicklung, Werkstoffeigenschaften und Wirtschaftlichkeitsbetrachtung für das Kunststoffrecycling über Lösen von Mischthermoplasten.”, Schriftenreihe Kunststoff-Forschung Band 48, Technische Universität Berlin.
[2] N.N., DKR im Blick 03/2000, Deutsche Gesellschaft für Kunststoffrecycling mbH

Introduction

Curing reactions play an important role in the manufacture of polymeric materials. Besides so-called prepregs and coatings, composites are worth mentioning here in particular. Composites are an important class of materials because of their mechanical properties and low weight. They usually consist of glass fiber or carbon fiber material that is held together by a cured resin. The resin and the fiber give the material its characteristic properties. Composite materials are often used in areas where safety is of major importance, e.g. in the construction of aircraft and automobiles. This means that the curing behavior of the resin must be precisely monitored and characterized.

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Introduction

When learning a new method, it is always a good idea to measure a system whose behavior is well known and documented under particular conditions. The thermal decomposition of CuSO₄ ⋅ 5 H₂O is a good example of this, and the interpretation of the TGA curve poses no problems for the beginner.

Experimental details

The measurements were performed with a TGA/SDTA851^e (range: 5 g; resolution 1 μg), coupled to an Inficon Themostar QMS mass spectrometer (mass range 1-300).

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Introduction

Thermomechanical analysis (TMA) measures the dimensional changes of a sample as a function of temperature. The online coupling of TMA with mass spectrometry (MS) allows the simultaneous measurement of decomposition gases and blowing or foaming agents and their effect on sample dimensions. For example, it is possible to investigate the delamination of printed circuit boards to determine the temperatures at which particular decomposition products are formed, or to follow the behavior of plastics on blowing or foaming. TMA combined with a gas analyzer (MS or FTIR) allows the dimensional changes caused by decomposition processes to be rapidly investigated or foaming processes to be optimized. A METTLER TOLEDO STAR^e system TMA/SDTA840 was coupled to an Inficon Thermostar QMS300 mass spectrometer (mass range 1-300) by means of a heated capillary in much the same way as for the TGA-MS coupling [1].

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Literature

[1] Evolved Gas Analysis, Collected Applications for Thermal Analysis, Mettler-Toledo GmbH (2001), page 5 and following pages