Thermomechanical curves

The effect of aromatic diamine residues on the heat resistance of polyimides is less clear cut. It was only by comparing thermomechanical curves of polypyromellitimides obtained from 3,3-diamino-4,4 -dichlorodiphenylmethane, and l,l-dichloro-2,2-di(3-amino-4-chlorophenyl)-ethylene that the system containing the 1,1-dichloroethylene group was found to be less heat resistant. With polyimides prepared from other dianhydrides this rule holds true as well but is less distinct. 

Fig. 13a-c. Thermomechanical curves for a unfilled epoxy binder, b epoxy syntactic foam with dressed glass microspheres, c syntactic foam with undressed filler (1) iiiitial sample and (2) sample after 2 months in contact with water us)... 

Thermomechanical, torsional and derivatographic measurements were carried out. The addition of BPA/DC results in an increase in Tg values by 32 °C at 40 phr dicyanate and by 54 °C at 80 phr dicyanate. The disappearance of the maximum in the high-elastic region of the thermomechanical curve during the repeated measurement confirms that the high-temperature postcuring is needed to reach complete crosslinking. 

Simultaneously, thermomechanical investigations were performed [28], obtained under continuous impact of compressing stress (100 g/cm3) on the sample in accordance with the technique [62], Glass transition temperatures, shown in the Tables, are determined from the primary deviation of thermomechanical curve run in the area of positive deformations. Depending on the spatial structure of the cycle, synthesized atactic and syndiotactic polymers are characterized by almost equal glass transition temperatures, Tg. 

Figure 4. Thermomechanical curves for copolymers with 1,3- and 1,5- disposition of cyclotetrasiloxane fragments in PDMS backbone 1, 2, 3, 4, 5 for copolymers with 1,3-disposition of...

Smirnova and coworkers studied the influence of various types of ionizing radiations on the physiomechanical characteristics of a statistical polymer of butadiene and acrylonitrile. Although the polymer is a statistical polymer, the nature of its thermomechanical curve indicates a block nature of the polymeric basis of the rubber there is a... 

Figure 7.38 Thermomechanical curves for (1-3) styrene copolymers containing (1, 2) 3% DVB and (5) 34% DVB, (6) polydivinylbenzene, and (3, 4) hypercrosslinked network prepared by crosslinking styrene-0.57% DVB copolymer with monochlorodimethyl ether to 100% Loading (2, 4, 5) lOg and (1, 3, 6) 400g per bead. (Reprinted from [202] with permission of Wiiey Sons, inc.)...

Figure 7.40 Effect of the heating rate on the position of thermomechanical curves of the network obtained by crossiinking styrene-0.57% DVB copoiymer with MCDE to 100% (1) 2.5, (2) 5, (3) 10, and (4) 20°C/min ioading 400g per bead. (Reprinted from [202] with permission of Wiley Sons, Inc.)...

Figure 6.19 Thermomechanical curves of comb-type methylcyclosiloxane copolymers. Where curve 1 copolymer XXXIX, curve 2 XXXVIII, curve 3 XXXVII and curve 4 XXXVI.

Fig, 11, Thermomechanical curves of the butadiene-acrylonitrile copolymer vulcanizates, filled with polystyrene. 

The modified polystyrene exerts a strengthening effect toward the elastomers, which is illustrated in Fig. 10. As could be concluded from the thermomechanical curves, this effect is caused by the ability of the discrete phase particles to undergo deformation, which leads to equalization of stress in the deformed sample (Fig. 11). Our investigations support the idea that interfacial grafting greatly improves the properties of elastomer and plastomer mixtures. 

Thereby, for chosen experimental objects were determined unknown parameters of developed mathematical model hyperelastic state constant, weighting coefficient and relaxation spectmm properties. Prediction results of thermomechanical curves trend successfully demonstrated prediction abihty of introduced mathematical description of thick cross-linked polymers viscoelastic pliability in all their physical states (Figure). 

The glass and fusion ten )eratures were determined from thermomechanical curves derived on a Kargin balance. The IR absorption spectra were obtained on a UR-10 spectrophotometer from samples made in the form of films or pellets with KBr. The turbidimetric titration of copolymer solutions was conducted with methanol. The optical density was measvired on a PEK-I photoelectric colorimeter. 

Experimental results are given by thermomechanical curves that allow determining temperature ranges for existence of ... 

Reaction 2 in Scheme 10.2 was used to prepare polymers based on 1,4-butanediol (m = 4, polymer 4), 1,6-hexanediol (m = 6, polymer 5), and 1,9-nonanediol (m = 9, polymer 6). The Hf content of these polymers is 42-45 wt %. Their molecular weight was determined by analyzing the shape of the thermomechanical curve (Table 10.2). 

Other example thermomechanical curves but for materials based on the single diisocyanate DBDI and SS macrodiols of variable molecular weights are shown in Table 3.6. The isocyanic index I ranged between 100-110 [17, 250]. 

The behavior of samples derived from polyurethane isocyanmate networks imder conditions of thermomechanical and TGA analyses were considered. Figure la shows thermomechanical curves of seven samples containing different quantity of polyurethane (PU) component and TDI, also differing by the elasticity modulus values. 

As found in previous observations [8], polyisocyanurate networks display two transitions with respect to their composition the first is low-temperature transition associated with devitrification of the rubbery phase, and high-temperature related to devitrification of the glassy phase. Hence, both transitions are temperature-shifted towards one another, and the progress of such shift depends on the microphase composition. Therefore, Figure lb presents separately thermomechanical curves of polyurethane isoeyanurate samples related to the low-temperature area. 

The character of thermomechanical curve of PAO showed that the tested samples revealed a rather rigid structure with high glass and viscous flow temperatures. The values of glass and viscous flow temperatures from thermomechanical data (Fig. 2) were found to be around 393 K and 468 K, respectively. 

The goal of this study was to compare the properties of network polymer formed by DGET self-cure at a temperature of the isotropic state (ZSO C) in the liquid crystalline state (169" C) without a magnetic field, ch provides anisotropy on domain level and in the presence of the magnetic field, that provides anisotropy on the macroscopic level A typical view of thermomechanical curves of the polymers obtained by TMA is presented in Figure 7. A dashed line corre onds to the thermomechanical curve without any loading (dilatometric condition). 

As one can see thermomechanical curve has a bimodal view at the first scan that disappears at the second scan of the sample. Glass transition temperature at the second scan is slightly increased. These results point to incomplete conversion of the polymers cured at 169" C due to difiusion control of the cure reaction at the latest stages (at a>0.85). It is interesting to note that such view of the thermomechanical curve is characteristic even of the polymer obtained at the DGET isotropization temperature (250T). 

The observed bimodality of the thermomechanical curves of cured DGET testifies for the fact that the forming polymers are stnicturaDy essentially inhomogeneous. The inhomogeneity could be on a molecular or/and siqiramolecular level On a molecular level the observed bimodal thermomechanical curve could be e7q>lain6d by bimodahty of the molar mass distribution of the polymer tested. There is, however, no chemic reason to expect the molar mass distribution of the polymer formed to be bimodal in the case under consideration. 

Thus, the observed bimodality of thermomechanical curves can be attributed to the essentially different deformation behavior of the amorphous and LC phases of the polymer. 

Figure 7. Thermomechanical curve of the polymer in the direction peipendicular to the direction of the applied magnetic field. First scan (1) second scan (2). Dashed line is a dilatometric curve.

Figure 7.43 TMA curve for polyfethylene terephthalate) (PET) fiber, (a) Thermal stress curve and (b) thermomechanical curve [32]...

Fig, 193. Thermomechanical curves of block copolymers of epoxide resin and nitrile rubber [42], 1) Epoxide resin 2) block copolymer with a 5 1 weight ratio of the resin and rubber 3) the same,... 

FIGURE 14.21 Thermomechanical curves of PVC-PMMAblends (Mcneill andNell, 1970)... 

Fig. 7. Thermomechanical curve of data obtained for partially cured samples , sample A , sample B -, sample C , sample E.

The parameters from equations (3.310) and (3.311) are determined from the thermomechanical curves of system durability. 

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