Silicon-containing Arylacetylene Research Articles

Thermal curing and degradation behaviour of silicon-containing arylacetylene resins

Silicon-containing aryacetylene resins (PSAs) have already shown potential application as heat-resistant materials due to their excellent thermal stability. The formation and degradation of structures in cured PSAs are very important to evaluate the thermal properties during their applications. Herein, the thermal curing and degradation behavior of PSAs with different substituents were investigated by DSC, FT-IR, Py-GC-MS, TGA and TG-GC-MS. DSC and FT-IR analysis reveals that the curing reaction is dominated by the crosslinking reaction of CCH and SiCC, meanwhile, the reactive substituents (such as SiH and SiCHCH2) could promote the CCH and SiCC reaction with higher conversion. Py-GC-MS was used to detect the pyrolysis products at 650 °C and 750 °C, respectively, and the results could provide important information about the curing reaction and structures of cured PSAs. The curing reaction of PSAs mainly contains cyclotrimerization and Diels-Alder reaction of CCH and SiCC, and some addition reaction to form polyene structure. The main structures in cured PSAs contain a lot of phenyl rings, some aromatic fused rings and a little of polyene structure, moreover, their contents in cured PSAs are dependent on the substituents of the precursors. The TGA results show that the substituents of SiH and SiCHCH2 can effectively improve the crosslinking index of the cured PSA-H and PSA-V, and endow them with better thermal stability. Additionally, the degradation behavior of cured PSAs have been well studied by TG-GC-MS. When the temperature is 400 °C, the SiCH3 and some aliphatic structure begin to degrade and form CH4, and with the temperature increasing to 500 °C, the unsaturated and aliphatic structures decompose into C2H4 and C2H6, and after 600 °C, the aromatic rings and fused rings in cured PSAs are dehydrogenated and release H2. In addition, the content of the degradation products and their forming temperature are also related with the substituents.

The strengthening and toughening effects of a novel octa(propargyl propyl sulfide) POSS (OPPSP) on silicon-containing arylacetylene (PSA) resin

A novel octa(propargyl propyl sulfide) POSS (OPPSP) was synthesized by the thiol-halogen reaction between octa(mercaptopropyl) POSS (POSS-SH) and propargyl chloride under phase transfer catalysis. Furthermore, OPPSP was employed as a reinforcing agent to prepare a modified silicon-containing arylacetylene (OPPSP-PSA) resin. The resulting OPPSP-PSA thermoset with 10wt% of OPPSP exhibits 80.5% and 92.8% increment in flexural strength and impact fractured energy as compared to pristine PSA thermoset. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) are used to observe the dispersion of OPPSP in the fractured surfaces of samples. The results show that both the nano-dispersion of POSS cages and the POSS-enriched “particles” are possible mechanisms behind the improved mechanical properties.

Synthesis and properties of silicon-containing arylacetylene resins with polyhedral oligomeric silsesquioxane

A series of silicon-containing arylacetylene resins containing polyhedral oligomeric silsesquioxane (PS resins) were synthesized by the hydrosilylation reaction between poly(dimethylsilyleneethynylenephenyleneethynylene) (PMSEPE) and octakis(dimethylsiloxy)octasilsesquoixane ( ) in the presence of a platinum catalyst (Pt-dvs). The chemical structures and properties of PS resins were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, rheological analysis, differential scanning calorimetry, dielectric measurement, thermogravimetric analysis, and scanning electron microscopy. The results show that PS resins can be crosslinked to form thermosets at temperatures less than 260°C. With the increment of , the dielectric constants of the thermosets gradually decrease from 2.91 to 2.73. The thermooxidative stabilities of PMSEPE thermosets are obviously improved with the incorporation of . POLYM. ENG. SCI., 55:316–321, 2015. © 2014 Society of Plastics Engineers

Preparation and properties of silicon-containing arylacetylene resin/benzoxazines blends

A series of aniline-based bifunctional benzoxazines (BZs) were synthesized using solventless or solvent method via the Mannich condensation reactions. The chemical structures of these BZs were confirmed using Fourier-transform infrared and proton-nuclear magnetic resonance spectroscopies. The polymer blends were prepared by mixing silicon-containing arylacetylene (poly(dimethylsilyleneethynylenephenyleneethynylene) (PSA)) resin with BZ in weight ratios at 110°C until a homogeneous viscosity liquid was obtained. The resultant blends were characterized by solubility tests, rheological analyses, differential scanning calorimetry, dynamic mechanical analyses and thermogravimetric analyses. The good solubility and low melt viscosity of the blends indicated excellent processability. The curing reactions resulted in the formation of interpenetrating polymer networks. The cured blends exhibited high glass transition temperatures (T gs) and thermal stabilities. The compressive strength and flexural strength of the blend casts improved when compared with pristine PSA.

Preparation and Properties of Modified Silicon-containing Arylacetylene Resin with Bispropargyl Ether

A novel silicon-containing arylacetylene resin (MSAR) modified by dipropargyl ether of bisphenol A (DPBPA) and dipropargyl ether of perfluorobisphenol A (DPPFBPA) was prepared separately. The curing behaviors of modified resins, DPBPA/MSAR and DPPFBPA/MSAR, were characterized with differential scanning calorimeter (DSC). The kinetic parameters of modified resins were obtained by the Kissinger and Ozawa methods. The results of dynamic mechanical analysis (DMA) revealed that the glass transition temperature (Tg) of the cured DPBPA/MSAR reached 486 °C. According to the thermogravimetric analysis (TGA), the decomposition temperature (Td5) of the cured resins and char yield (Yc, 800 °C) decreased as the dipropargyl ether loadings increased, especially in air. With the same weight loading, thermal stability of DPBPA/MSAR was better than that of DPPFBPA/MSAR. The carbon fiber (T300) reinforced composites exhibited excellent flexural properties at room temperature with a high property retention at 300 °C.

Preparation and Properties of Silicon-Containing Arylacetylene Resins with Octa(maleimidophenyl)silsesquioxane

Modified silicon-containing arylacetylene resins (DMSEPE-OMPS) were prepared from poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) and Octa(maleimidophenyl)- silsesquioxane (OMPS). The curing reaction of DMSEPE-OMPS resin was studied by FT-IR and DSC techniques. Thermal stability and dielectric properties of cured DMSEPE-OMPS resins were determined. FT-IR and DSC analyses indicate that thermal polymerization of DMSEPE-OMPS resin occurs in the curing process. Thermal stabilities of cured DMSEPE-OMPS resins under N2 and air atmosphere decrease gradually with the increment of OMPS components. The incorporation of OMPS can obviously reduce dielectric constant of DMSEPE-OMPS resins.

Characterization of a modified silicon-containing arylacetylene resin with POSS functionality

A modified silicon-containing arylacetylene resin with a well-defined organic-inorganic POSS functionality was successfully synthesized by Huisgen azide-alkyne 1,3-dipolar cycloaddition. The POSS hybridized resin exhibits excellent thermal properties which were characterized by differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). Scanning electron microscope (SEM) was used to characterize fracture surface of the hybridized polymer. The results show that phase separation occurs. The POSS moieties are aggregated each other in the polymer to form 200–400 nm domains.

Synthesis and Characterization of a New Thermosetting Boric Acid Ester

A new thermosetting boric acid ester modifier containing unsaturated bonds (abbreviated TBCE) was prepared. Structure, hydrolytic stability, curing properties and and thermal properties of the boric acid ester were studied by FT-IR, DSC and TGA. The result indicated that the obtained boric acid ester was soluble in most common solvents and was easily processed. The thermogravimetric analysis of silicon-containing arylacetylene resin modified by TBSE (abbreviated MSAR) showed that char yield at 800°C was 87% under nitrogen and 49% under air, and Td5 (temperature of 5% weight loss) were 570°C and 580°C respectively.

Thermal stability of the copolymers of silicon-containing arylacetylene resin and acetylene-functional benzoxazine

Acetylene-functional benzoxazine resin (AFBEN) was used to modify silicon-containing aryacetylene resin (SCAAR). The thermal stability, degradation and ablation mechanisms were investigated. Based on the results of Py/GC/MS methods, we concluded that the cross-linking reactions of poly(dimethylsilyleneethynylene–phenyleneethynylene)(DMSEPE, a class of SCAAR) were due to (1) the Diels–Alder reaction between Ph–C C and C C, (2) the ring trimerization of C C and (3) radical polymerization of C C to form polyene structure. During the curing of AFBEN, polyene was the main product of the polymerization of ethynyl in AFBEN and the activation of the para positions of the aniline ring increased due to the introduction of ethynyl. XRD and XPS results showed that SiO 2 and SiC formed on the surface of the composites in the process of ablation.

Synthesis and Characterization of SAR/SiO<sub>2</sub> Hybrid Materials with High Thermal Stability

A silicon-containing arylacetylene resin, poly[(dimethylsilyl)eneethynylene phenyleneethynylene] with methoxy silyl terminal group (abbreviated MSAR) was synthesized. The resin and tetraethoxysilane (abbreviated TEOS) were used to prepare silicon-containing arylacetylene resin (abbreviated SAR) /SiO2 hybrid materials by a sol-gel method. Both the curing process of the xerogel and thermal properties of the hybrid materials were studied by FT-IR, DSC and TGA. The thermogravimetric analysis of the hybrid materials showed that Td5 (temperature of 5% weight loss) was 696°C and char yield was 92.1% at 800°C in nitrogen. A Si-C-O ceramic residue was obtained in high yield(86.8%) by sintering up to 1450°C in nitrogen.

A New Silicon-Containing Arylacetylene Resin With Amine Groups as Precursor to Si−C−N Ceramic

A new preceramic precursor was prepared by chlorination and ammoniation reaction of poly(methylsilyleneethynylenephenyleneethynylene) (MSEPE), [−SiH(CH3)− C≡C−C6H4−C≡C−]n. The obtained amine-modified silicon-containing arylacetylene resin (MSEPE-An) was a liquid polymer at room temperature and could be thermally cross-linked at temperatures lower than 200°C. The chemical structure of MSEPE-An was characterized by FTIR, 1H NMR, and GPC. The pyrolysis of the cured MSEPE-An was carried out in N2 atmosphere up to 1450°C to produce a Si−C−N ceramic composite. The ceramic composite was analyzed by FTIR and X-ray diffraction techniques. The electromagnetic wave absorption properties of a paraffin sample with 10 vol% Si−C−N ceramic powders were characterized in a frequency range of 2–18 GHz, according to a conventional reflection/transmission technique. Experimental results demonstrated that the Si−C−N ceramic composite provided good electromagnetic wave absorption performance.

Study on the copolymers of silicon-containing arylacetylene resin and acetylene-functional benzoxazine

An acetylene-functional benzoxazine (AFBEN) which was used to modify poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) was synthesized by a solventless procedure. The modified resins (DMSEPE/AFBEN) were obtained by blending DMSEPE and AFBEN in different amount. The thermopolymerization of DMSEPE/AFBEN resins were investigated by DSC technique. The dynamic mechanical analysis showed that the storage modulus (E) of the cured DMSEPE/AFBEN resin containing less than 30 wt% AFBEN did not decrease at the temperature lower than 500 °C. When the AFBEN loading increased from 20 to 100 wt%, a decrease in glass transition temperature from 523 to 342 °C was observed. The thermal stability of the cured DMSEPE/AFBEN resins was determined by thermogravimetric analysis (TGA) in N2 and air. The TGA results showed the cured DMSEPE/AFBEN resins had good thermal stability. The carbon fiber (T700) reinforced DMSEPE/AFBEN composites exhibited excellent mechanical properties (flexural strength: 1,694 MPa) at room temperature and high strength remaining of 76% at 300 °C.

Fiber reinforced silicon-containing arylacetylene resin composites

A silicon-containing arylacetylene resin (SAR), a poly(dimethylsilyleneethynylene phenyleneethynylene) (PMSEPE), was synthesized. The PMSEPE is a solid resin at ambient temperature with a softening temperature about 60°C and soluble in some solvents like tetrahydrofuran. The melt viscosity of the PMSEPE resin is less than 1 Pa·s. The resin could cure at the temperature of lower than 200°C. Fiber reinforced PMSEPE composites were prepared from prepregs which were made by the impregnation of fibers in PMSEPE resin solution. The composites exhibit good mechanical prop- erties at room temperature and 250°C. The observation on fracture surfaces of the composites reinforced by glass fibers and carbon fibers demonstrates that the adhesion between the fibers and resin is good. The results from an oxyacetylene flame test show that the composites have good ablation performance and XRD analyses indicate that SiC forms in the residues during the ablation of the composites.