Thermal curing and degradation behaviour of silicon-containing arylacetylene resins

Abstract

1 Silicon-containing aryacetylene resins (PSAs) have already shown potential 2 application as heat-resistant materials due to their excellent thermal stability. The 3 formation and degradation of structures in cured PSAs are very important to evaluate 4 the thermal properties during their applications. Herein, the thermal curing and 5 degradation behavior of PSAs with different substituents were investigated by DSC, 6 FT-IR, Py-GC-MS, TGA and TG-GC-MS. DSC and FT-IR analysis reveals that the 7 curing reaction is dominated by the crosslinking reaction of C≡C-H and Si-C≡C-, 8 meanwhile, the reactive substituents (such as Si-H and Si-CH=CH 2 ) could promote 9 the C≡C-H and Si-C≡C-reaction with higher conversion. Py-GC-MS was used to 10 detect the pyrolysis products at 650℃ and 750℃, respectively, and the results could 11 provide important information about the curing reaction and structures of cured PSAs. 12 The curing reaction of PSAs mainly contains cyclotrimerization and Diels-Alder 13 reaction of C≡C-H and Si-C≡C-, and some addition reaction to form polyene structure. 14 The main structures in cured PSAs contain a lot of phenyl rings, some aromatic fused 15 rings and a little of polyene structure, moreover, their contents in cured PSAs are 16 dependent on the substituents of the precursors. The TGA results show that the 17 substituents of Si-H and Si-CH=CH 2 can effectively improve the crosslinking index 18 of the cured PSA-H and PSA-V, and endow them with better thermal stability. 19Additionally, the degradation behavior of cured PSAs have been well studied by 20 TG-GC-MS. When the temperature is 400℃, the Si-CH 3 and some aliphatic structure 21 begin to degrade and form CH 4 , and with the temperature increasing to 500℃, the 22 unsaturated and aliphatic structures decompose into C 2 H 4 and C 2 H 6 , and after 600℃, 23 the aromatic rings and fused rings in cured PSAs are dehydrogenated and release H 2 . 24In addition, the content of the degradation products and their forming temperature are 25 also related with the substituents. 26 27 Key words： 28 Silicon, arylacetylene, cure, degradation 29 3 1

Silicon‐containing fluorenylacetylene resins with low curing temperature and high thermal stability

“…Thus, it can be used as an internal standard to measure the conversion of the reactive groups at different temperatures by calculating the relative intensity of reactive groups, as shown in eq. …”

“…The relative contents of phenyl ring volatile and its derivatives for DEF are up to 42.28%, which could be from the pyrolysis of fluorenyl rings (as shown in Scheme ) due to instability of C 9 on fluorenyl ring, and a little bit cyclotrimerization [Scheme (a)]. Also identified products contained a few of naphthyl rings and their derivatives which were formed by Diels–Alder reaction [Scheme (b)]. Besides, a lot of phenanthryl ring volatiles and their derivatives were found in the pyrolysis products of DEF which could be produced by the reaction between fluorenyl rings and alkynyl units [Scheme (c)] .…”

Synthesis and characterization of thermosetting polyacetylene‐terminated silicone resins

“…The ─C≡CH absorption band at 3296 cm −1 completely disappeared, indicating that ─C≡CH completely reacted during the curing process. Whereas, the infrared absorption band of ─C≡C─ (2160 cm −1 ) groups was still observed and slightly reduced after the curing process, that is the result of the incomplete Diels–Alder reaction at internal alkyne groups …”

Star‐shaped silicon‐containing arylacetylene resin based on a one‐pot synthesis using zinc powder catalysis with improved processing and thermal properties

“…Surprisingly, the T d5 value and yield of SSA resin were optimal when the molar ratio of the reactants was adjusted to DEB:TCS = 6:1 (entry 8). In the entry 8, the alkynyl groups in DEB are involved in the cyclotrimerization reaction to form pre‐polyarylacetylene (pre‐PAA) and the alkynyl groups in pre‐PAA may be cured with the acetylenyl groups in the SSA resin to form a more highly crosslinked aromatic polymer. The crosslinked structure has a positive effect on the thermal stability of SSA resin.…”

“…On the one hand, the resin catalyzed by zinc power is a viscous liquid at room temperature due to the presence of partial olefinic bonds at the terminal ends of the structure, which are beneficial for processability . On the other hand, there have been more alkynyl groups in the structure of SSA resins when compared to linear PSA resins, which is conducive to the more terminal alkynes among the molecules being available to be involved in the cyclotrimerization reaction to form groups with good thermal stability, such as benzene and naphthalene rings . Therefore, the SSA resins will have an excellent processability and high thermal stability, meanwhile have a low curing temperature.…”