Authors:S. M. Sabzevari, S. Alavi-Soltani, and B. Minaie
state. Vitrification is the point at which the resin changes from the rubbery state to the solid glassy state. The TTT diagram may be augmented by adding iso-conversion, iso-glass transitiontemperature (iso- T g ), and iso-viscous contours as well as
Authors:Jorge Amim Jr., Leandro S. Blachechen, and Denise F. S. Petri
) were added to carboxymethyl cellulose acetate butyrate (CMCAB), which acted as a plasticizer for CMCAB, leading to dramatic reduction of glass transitiontemperature of CMCAB, namely, Δ T g = −158 and −179 °C, respectively. The aim of this study is to
Authors:Bedřich Smetana, Simona Zlá, Aleš Kroupa, Monika Žaludová, Jaromír Drápala, Rostislav Burkovič, and Daniel Petlák
deviations in comparison with those of the second and third DTA runs. This is probably caused by poorer thermal contact between the sample and crucible during the first run. Only transitiontemperatures from the second and third heating cycles were used for
The definition of the glass transition temperature, Tg, is recalled and its experimental determination by various techniques is reviewed. The diversity of values of Tg obtained by the different methods is discussed, with particular attention being paid to Differential Scanning Calorimetry
(DSC) and to dynamic techniques such as Dynamic Mechanical Thermal Analysis (DMTA) and Temperature Modulated DSC (TMDSC).
This last technique, TMDSC, in particular, is considered in respect of ways in which the heterogeneity of the glass transformation
process can be quantified.
The relationship between transition temperatures and copolymer composition was studied by DSC. Three types of copolymers were
studied: styrene-acrylonitrile (SAN), vinyl chloride-vinyl acetate (VC-VA), and ethylene vinyl acetate (EVA). SAN's and VC-VA's
are amorphous copolymers, whereas EVA's are semi-crystalline copolymers. The variation of the glass transitions and the crystalline
melting are discussed in this study.
The study of homogeneous distribution coefficients in determining the transition temperatures of isomorphologically analogous
components and in predicting the existences of some new unstable compounds has been carried out in detail with special references
to vitriols of nickel, manganese, zinc, copper and magnesium. In the course of the investigation with NiSO4·7H2O as host and54Mn as guest, the transition temperature of orthorhombic NiSO4·7H2O was shown to be 26.5 °C, and with orthorhombic ZnSO4·7H2O and MgSO4·7H2O as host and copper sulphate as guest, the limits of existences of orthorhombic CuSO4·7H2O and newly predicted CuSO4·6H2O were found to be 13.5° to 44 °C and 44° to 51 °C, respectively. In addition, the transition temperatures of orthorhombic
MnSO4·7H2O (10 °C), stable NiSO4·7H2O (30.5±5 °C) and orthorhombic ZnSO4·7H2O (39 °C) were verified. The new method of approach is very simple, reproducible and easily adaptable.
The linear expansions of two materials have been measured, a double-base propellant and a carboxyl-terminated polybutadiene. The glass transition temperature,Tg and expansion coefficients below and aboveTg have been calculated. The influence of the heating and cooling rates and sample thickness has been investigated. The results show that the value ofTg is dependent on the rates of heating and cooling but not on the sample thickness. Extrapolating to zero rate gives the sameTg for both heating and cooling. The expansion coefficients are not influenced by the rates of heating and cooling or by the sample thickness.
The glass transition temperature of a copolymer depends not only on chemical composition but also on its comonomer sequences. This experimental fact is explained by Barton's and Johnston's equations. Their equations, though complicated, become simple, if a suitable parameter is used to describe the comonomer sequences. It is shown that with these new expressions, their equations can be used to understand glass transition temperatures of two additional types of copolymers, compatible multiblock copolymers and homopolymers with various tacticities treated as steric copolymers.
Authors:E. Collar, C. Marco, O. Laguna, S. Areso, and J. García-Martínez
A discussion on the influence of grafted polar groups (succinic anhydride and succinil-fluorescein) in glass transition behaviour of atactic polypropylene is shown in this work, on the basis of the reaction conditions used to obtain the modified polymers, kind and amount of grafted groups, and the degradation processes which may take place. The Box-Wilson experimental design methodology for two independent variables (reactant concentration to obtain the modified polymer) has been used to follow variations in glass transition temperatures. The existence of undesired degradation processes is considered as independent of the grafting reactions, and the model predictions seem to agree with this latter.
Micro-thermal analysis (μTATM) is a technique in which thermal analysis is performed on surfaces of test specimens on a small (ca. 2×2 μm) scale. Like
any thermal analysis technique, interpretation of results benefits from accurate temperature information and knowledge of
the precision of the resultant measurement. However, temperature calibration for such methods is more challenging than with
its macro relatives since the calibrant comes into direct contact with the AFM sensor. This paper describes suitable calibration
procedures for different types of transitions namely for first order transitions (melting points) and for glass transition
temperatures using organic chemicals and polymers.