ISSN:0022-233X    

DOI:10.1080/00222337408065808

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Dynamic thermal methods of analysis are becoming increasingly important for polymer characterization. These techniques are based on measuring changes in certain physical properties continuously and automatically upon variation of the sample temperature. This presentation reviews thermal analysis in general, and briefly describes the features and applications of several commonly used thermal methods, such as differential thermal analysis, differential scanning calorimetry, thermogravimetry, thermomechanical analysis, electrothermal analysis, thermo-optical analysis, and thermal evolution analysis. General references are given for the various techniques.

ISSN:0022-233X    

DOI:10.1080/00222337408065809

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The curing reaction of bisphenol A diglycidylether with 4,4′-diaminodiphenylmethane (DDM) was studied by thermoanalytical methods. The overall reaction was monitored through the exothermic heat of reaction by differential scanning calorimetry (DSC), and a method is developed for predicting isothermal conversion-time curves over a wide temperature range from the results of two dynamic DSC scans. The reaction mechanism is not specified but it is assumed not to change with conversion, and the rate is assumed to be controlled by a single rate constant of the Arrhenius form. A series of fully cured resins prepared with varying DDM concentration is characterized by penetrometer, thermal expansion, and DSC methods. The Tg's of these resins are compared with those obtained using the stoichiometric quantity of DDM and reacted to different calorimetric degrees of cure. The Tgof the resin increases by about 70[ddot];C in the final 10% of the curing reaction where ΔH measurements are least sensitive, so that the final stages of cure are best monitored by Tgmeasurements.

ISSN:0022-233X    

DOI:10.1080/00222337408065810

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Seven organic peroxide initiators for the polymerization of diallyl-o-phthalate prepolymers were studied using differential scanning calorimetry. Included were t-butyl perbenzoate, dicumyl peroxide, α,α′-bis(t-butyl peroxy) diisopropyl-benzene, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3, di-t-butyl peroxide, and t-butyl hydroperoxide. Heats of reaction and reaction rate constants are presented for each initiator at 1, 2, 3, and 4 phr of diallyl-o-phthalate prepolymers. The differences in reaction temperature and rate are discussed. Effects of four types of commonly used fillers (asbestos floats, ground quartz, calcium silicate, and clay) on the heats of reaction of diallyl-o-phthalate prepolymers using t-butyl perbenzoate and dicumyl peroxide initiators show the large inhibiting effect of untreated kaolinite clays on this polymerization.

ISSN:0022-233X    

DOI:10.1080/00222337408065811

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Polymer single crystals or lamellae are widely used in models for more complex systems such as fibers, films, or bulk polymer. Determination of important thermodynamic and physical properties for the crystals is often frustrated by their tendency to reorganize on heating. Partly as a consequence of this, the melting ranges for high molecular weight polymers are often quite broad. A novel technique has been developed which permits a more detailed examination of the melting/morphology relationships that exist in single crystals. This has led to the observation that high molecular weight polyethylene (PE) single crystals possess much narrower melting ranges than had been previously reported. It has been possible to determine distinct transformation temperatures for the {100} and {110} fold sectors that exist in some PE crystals. Melting point determinations have been made on a series of isothermally crystallized PE crystals using DTA. Narrow multiple peaked thermograms were obtained, and peak position and ratio could be related to morphological differences between the crystals.

ISSN:0022-233X    

DOI:10.1080/00222337408065812

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Thermoanalytical techniques are valuable tools for the characterization of thermosetting polymers. Examples are given of the application of thermal methods to the identification of filled and unfilled epoxy and amino resins. Various thermo-analytical methods of following the curing of thermosetting polymers are considered. Thermal techniques are essential to the study of degradation reactions; the decomposition of a melamine formaldehyde resin is discussed in detail. It is concluded that the usual methods of thermal analysis alone are insufficient to characterize fully the degradation of amino resins.

ISSN:0022-233X    

DOI:10.1080/00222337408065813

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Samples of full-thickness rat skin from birth to 3 years were characterized by thermal analysis. The techniques involve differential scanning calorimetry, thermomechanical analysis, and thermogravimetry.

ISSN:0022-233X    

DOI:10.1080/00222337408065814

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Practical rubber formulations are complex mixtures of polymer (s), fillers, plasticizers, curatives, and processing aids. Classical methods exist for determining many of the components of these systems but are too time consuming for routine use in quality control or problem solving activities. Thus a need has existed for more rapid procedures. Previous studies of gum, compounded, and cured elastomers showed that thermogravimetry (TG) can provide information regarding the polymer, oil, carbon black, mineral filler, and ash content of vulcanizates. The present study extends this approach to multicomponent polymer and carbon black systems to determine whether components of similar thermal characteristics can be effectively analyzed. Vulcanizates containing binary (natural rubber (NR)/ethylene propylene terpolymer (EPDM) or ternary (NR/EPDM/styrene-butadiene rubber) blends were successfully analyzed by the standard, dynamic TG method.IsothermalTG was shown to have significant potential for analyzing blends of FEF and SRF carbon blacks (CB) in a standard formulation. Two additional approaches, derivative TG (DTG) and normal probability analysis are examined for potential applicability in these analyses. The former has apparent value for polymer blend analysis; the latter, based on preliminary data, may have value in the analysis of some CB blends.

ISSN:0022-233X    

DOI:10.1080/00222337408065815

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The dehydrohalogenation of several alternating and random vinyl chloride/acrylonitrile copolymers was characterized by thermogravimetry. The polymers were made in solution, and the conversions were kept below 5% to insure uniform sequence distributions. Hydrogen chloride was generated within a relatively narrow temperature range somewhere between 200 and 300°C depending on the sequence distribution, relative viscosity, and composition. The weight-loss during the dehydrohalogenation could be attributed completely to the hydrogen chloride available in the copolymer. Alternating copolymers were significantly more stable than random copolymers were significantly more stable than random copolymers at the same relative viscosity. For a given sequence distribution or composition, stability decreased with decreasing relative viscosity. The stability decreased as acrylonitrile content was increased from 23 to 57%.

ISSN:0022-233X    

DOI:10.1080/00222337408065816

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

It is difficult to estimate the degree of thermal degradation which has taken place in complex parts composed of cellulosics and polymeric insulation unless complete failure has occurred. There is a definite need for a parameter which can quickly and easily measure the relative degree of thermal attack on organic insulation subjected to various known environmental and processing conditions. This paper reports preliminary work using derivative thermogravimetry to perform this function. Derivative thermogravimetric analysis (TGA) was used to produce a value, TGA Index, related to the peak height of the major TGA derivative signal. This TGA Index was found to correlate with the copper number of insulating paper measured after thermal degradation. The application of TGA Index to evaluation of polymer degradation after thermal shock, water absorption, and accelerated UV attack is also discussed. Finally, preliminary studies on the use of derivative TGA to evaluate coatings exposed to various outdoor environments around the country are reported.

ISSN:0022-233X    

DOI:10.1080/00222337408065817

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor