Polymers relative thermal stability

Fig Relative thermal stability of polymers as determined by weight loss on heating at 5°C/min in nitrogen in thermogravimetric analysis. 

Relative Thermal Stability of Selected Polymers Based on the Temperature at Which Their Half-Life Th Is 30 min... 

Figure 10.8. Relative thermal stability of polymers by TGA (6). PVC = polyvinylchloride PMMA = polymethylmethacrylate PI = polyimide...

The relative thermal stabilities obtained by dynamic thermogravimetry above 200°C and by isothermal methods at 220°C are given in Figs. 51 and 52. (A) is a slightly branched polymer sample produced using benzoyl peroxide. Polymer (B) is a linear syndiotactic sample prepared at low temperature. The figures show that copolymers (C) and (D) are both much less stable than (A) and (B). Tertiary hydrogen and tertiary chlorine are... 

A comparison of the relative thermal stability of a number of different polymers was described by Newkirk (44). The TG curves, as shown in Figure 4.39, were heated rapidly in nitrogen to about 340CC and then more slowly. An order of stability is readily observable polylmethyl methacrylate) < polystyrene < Mylar and nylon < polyethylene < Lexan. 

In another TG study, Chiu (45) compared the relative thermal stabilities of five polymers, as shown in Figure 4.40. These polymers, poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA), high-pressure polyethylene (HPPE), polytetrafluoroethylene (PTFE), and an aromatic poly-pyromellitimide (PI), were all heated under identical conditions in the... 

Comment on the relative thermal stabilities of the polymers made from compounds where Ar is either... 

The formation of miscible rubber blends slows the rate of crystallization (Runt and Martynowicz, 1985 Keith and Padden, 1964) when one of the components is crystallizable. This phenomenon accounts for data that show lower heats of fusion that correlate to the extent of phase homogeneity (Ghijsels, 1977) in elastomer blends. Additionally, the melting behavior of a polymer can be changed in a miscible blend. The stability of the liquid state by formation of a miscible blend reduces the relative thermal stability of the crystalline state and lowers the equilibrium melting point (Nishi and Wang, 1975 Rim and Runt, 1520). This depression in melting point is small for a miscible blend with only dispersive interactions between the components. 

Barikani, M. Hepburn, C. (1987). The relative thermal stability of polyurethane elastomers. 3 Influence of chain extender system. J. Cell. Polym., 6(3), 47-66. 

Related polymers (130), also relatively low molecular weights (Mn up to 4400) and tolylmethylthiomethyl or naphthylmethylthiomethyl side chains, were obtained by uncatalyzed and catalyzed melt condensation of diacids (131), p-tolylmethylthiomethylsuccinic acid (131a), or 1-naphthylmethylthiomethylsuccinic acid (131b) with 2,2 -oxydiethanol (132) (306). Polymers showed thermal stabilities of up to 220 or 280°C, respectively. 

Relative Thermal Stability of the Polymers Prepared from Bis(l,2-hydroxyketo) Ligands... 

TGA is often used to determine the relative stability of materials. This is carried out by observing the onset temperature, in a given atmosphere, of the decomposition of the polymer. Since the majority of polymers are used in real life scenarios, the atmosphere usually chosen is air. It is also possible though to assess relative thermal stability of materials that are used in service under adiabatic conditions, for example rubber seals that are immersed in oil. It is always important to remember in these cases though that the actual lifetime of the material will also be influenced by the media that it contacts and not just the temperature that it is exposed to. 

Polycarbonate blends with PBI may be used to improve the blend miscibility by intermolecular interactions (hydrogen bonding) as compared to polyimides, and subsequently improved relative thermal stability. Due to the high temperature performance attributes of PBI and PBO, blending would be expected to enhance further the thermal characteristics and end-uses, and with good solubility in typical solvents for the individual polymer resins. 

Block copolymers can contain crystalline or amorphous hard blocks. Examples of crystalline block copolymers are polyurethanes (e.g. B.F. Goodrich s Estane line), polyether esters (e.g. Dupont s Hytrel polymers), polyether amides (e.g. Atofina s Pebax grades). Polyurethanes have enjoyed limited utility due to their relatively low thermal stability use temperatures must be kept below 275°F, due to the reversibility of the urethane linkage. Recently, polyurethanes with stability at 350°F for nearly 100 h have been claimed [2]. Polyether esters and polyether amides have been explored for PSA applications where their heat and plasticizer resistance is a benefit [3]. However, the high price of these materials and their multiblock architecture have limited their use. All of these crystalline block copolymers consist of multiblocks with relatively short, amorphous, polyether or polyester mid-blocks. Consequently they can not be diluted as extensively with tackifiers and diluents as styrenic triblock copolymers. Thereby it is more difficult to obtain strong, yet soft adhesives — the primary goals of adding rubber to hot melts. 

Silicones This term is given to a wide range of polymers including fluids, rubbers and thermosetting resins. Although rather expensive relative to most other plastic they are particularly noted for their thermal stability and their water repellency. 

The polymer has an impact sensy of 40cm at the 50% point using a BM machine with a 2kg wt (RDX, 28cm), a thermal stability of 13 mins using a 1.3g sample with Kl-Starch indicator paper (Ref NC, 10 mins, no color), also, a rel vise of 1.50 centipoises at 25° using a 1% acet soln Ref PJ. Blatz et al, Research In Nitropoly-mers And Their Application To Solid Smokeless Propellants , Report No 907, Aerojet-General Corp, Azusa, Calif ONR Contract N7 onr-462, Task Order I and Contract NO as 54-399-C (15 Dec 1954), 16 17... 

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