Chemistry and Adhesive Properties of Phenylethynyl-Terminated Phenylquinoxaline Oligomers

As part of a program to develop high performance/high temperature structural resins for potential aeronautical applications, phenylethynyl-terminated phenylquinoxaline oligomers were prepared, characterized, thermally cured and the cured resins were evaluated as adhesives. The phenylquinoxaline oligomers were prepared by conventional and aromatic nucleophilic displacement routes and chain terminated with mono or di(phenylethynyl) groups. The oligomers were melt pressed into thin films, compression molded into tensile and compact tension specimens, and fabricated into titanium-to-titanium single lap shear adhesive specimens. The oligomers were generally compression molded for 1 hr at 350°C under pressures ranging from 0.10 to 1.4 MPa. The phenylquinoxaline oligomer prepared via aromatic nucleophilic displacement exhibited better processability and higher tensile shear strengths than those of the oligomers prepared via the conventional synthetic route. The synthesis, physical and mechanical properties of these oligomers and their cured polymers are presented.     

Solid state features and mechanical properties of PEI/PBT blends

Extrusion‐blended and injection‐molded PEI/PBT blends were found to be miscible whatever the composition. The processability of the blends clearly improved with the presence of PBT. The melt pressure at the exit was seen to be a parameter as representative of the processability of the blends as the torque of blending. In the blends with 80 and 90% PBT, a positive volume of mixing and the maintenance of the crystallinity of PBT were seen. However, in the rest of the blends, negative volumes of mixing and important decreases in the crystallinity of PBT were found. These solid state features gave rise to a ductility similar to that of the pure PEI and to a synergism of the modulus of elasticity and of the yield stress in the 90/10 and 80/20 blends such that the values were higher than those of either of the pure components. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 885–892, 2001     

Processability characteristics and physico‐mechanical properties of natural rubber modified with rubber seed oil and epoxidized rubber seed oil

The processability characteristics and physico‐mechanical properties of natural rubber (NR) modified with raw rubber seed oil and epoxidized rubber seed oil have been studied. The modified mixes showed higher scorch time and lower cure rate, crosslink density, and ultimate state of cure compared to an unmodified mix. The thermal stability of the vulcanizates was practically unaffected by the modification. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1413–1418, 2000     

3种流动分散剂在丁基橡胶胶料中的应用研究

对比研究流动分散剂RL16,WB16和AC617对丁基橡胶胶料性能的影响.结果表明:3种流动分散剂均能提高胶料的流动性和填料的分散性,RL16和WB16的改善效果优于AC617;加入RL16和WB16的胶料焦烧时间和t90有所延长,硫化胶的100％和300％定伸应力减小,拉断伸长率增大,而AC617对硫化胶的物理性能影响较小;加入RL16和WB16的硫化胶耐热空气老化性能和耐压缩永久变形性能有所下降,影响程度略高于AC617.     

Rheological study on tetrafluoroethylene/hexafluoropropylene copolymer and its implication for processability

Tetrafluoroethylene/hexafluoropropylene copolymers (FEPs) are widely used in diverse fields due to their outstanding performances in chemical resistance, thermal stability, and insulation. However, their processsability is poor, exhibiting narrow stable flow region and remarkably early melt fracture. Herein, we tried to explore the origin of such poor processability in a rheological way, because melt rheology behaviors are highly related to their processing processes. The shear rheology results indicate that FEPs exhibit multiple flow regions. The flow curve of FEP608 was obtained, and its η₀ value was calculated to be 1.70 kPa s⁻¹ at 360°C. Extensional rheological data suggest that FEPs have much lower e and B values when compared with those of common polymers, suggesting their weaker elasticity during extrusion. Based on such rheological results, the poor processability of FEPs is ascribed to their high viscosity induced by special interchain interaction associating with F atom, which can easily cause accumulated elastic energy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Novel acetylene‐terminated polyisoimides with excellent processability and properties comparison with corresponding polyimides

Two novel acetylene‐terminated isoimide oligomers and their corresponding imide oligomers have been synthesized by using trifluoroacetic anhydride or acetic anhydride as dehydrating agent, respectively. Their main structure was confirmed by Fourier transform infrared spectroscopy (FTIR). The isoimide oligomers were amorphous and showed excellent solublility in many common solvents, such as acetone and tetrahydeofuran, whereas the imide oligomers cannot dissolve in them. Differential scanning calorimetry and rheometer were used to study crosslinking behavior and processability of these oligomers. The isoimide oligomers exhibited considerably wider processing window and lower viscosity compared with imide ones. As expected, the isoimide form could be converted to imide form through thermal treatment, which could be demonstrated by FTIR. After the oligomers were cured, the polyisoimides showed similar properties compared with corresponding polyimides. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fluorinated phenylethynyl-terminated imide oligomers with reduced melt viscosity and enhanced melt stability

Two novel fluorinated phenyethynyl-contained endcapping agents, 4-(3-trifluoromethyl-1-phenylethynyl)phthalic anhydride (3F-PEPA) and 4-(3,5-bistrifluoromethyl-1-phenylethynyl)phthalic anhydride (6F-PEPA) were synthesized, which were employed to synthesize two fluorinated model compounds, N-phenyl-4(3-trifluoromethyl)-phenylethynylphthalimide (3F-M) and N-phenyl-4(3,5-bitrifluoromethyl)-phenylethynyl phthalimide (6F-M). The thermal cure kinetics of 3F-M and 6F-M were analyzed using DSC and compared to the unfluorinated derivative, N-phenyl-4-phenylethynylphthalimide (PEPA-M). The thermal cure temperatures of 3F-M and 6F-M were 399 and 412 °C, which were 22 and 35 °C higher than that of PEPA-M, respectively. The thermal cure kinetics of 3F-M and 6F-M best fit a first-order rate law, although 3F-M and 6F-M reacted slower than PEPA-M. However, the exothermic enthalpy of 3F-M and 6F-M were only half of PEPA-M. Based on the model compounds study, a series of fluorinated phenylethynyl-terminated imide oligomers (F-PETIs) with different calculated molecular weights (Calc'd M_n) were synthesized by thermal polycondensation of 2,3,3′,4′-biphenyltetracarboxylic acid dianhydride (a-BPDA) and 3,4′-oxydianiline (3,4′-ODA) using 3F-PEPA or 6F-PEPA as the endcapping agent. The substituent effects of the trifluoromethyl (−CF₃) groups on the thermal cure behavior and melt processability of F-PETIs were systematically investigated. Experimental results reveal that the melt processability of F-PETI was apparently improved by the reduced resin melt viscosities and the enhanced melt stability due to the incorporation of the −CF₃ groups in the imide backbone. All of those F-PETIs exhibit outstanding thermal and mechanical properties.     

Early development of a biodegradable energetic elastomer

The expected depletion of oil resources and a greater awareness for the environmental impact of plastic products have created a strong interest toward energetic polymers that are not only biodegradable but also obtainable from renewable resources. In this work, a copoly(ester/ether) was synthesized from polyepichlorohydrin and sebacoyl chloride using pyridine as a Lewis‐base catalyst. The chlorinated polymer was azidified with NaN₃ in dimethyl sulfoxide solutions. The success of the reaction was confirmed by ¹H‐NMR, ¹³C‐NMR, and Fourier‐transform infrared spectroscopy. Two types of polyurethane networks were synthesized from the nonenergetic and the energetic copolymers, adding polycaprolactone triol and using L ‐lysine diisocyanate as a nontoxic curing agent. The two resulting polyurethanes were soft thermoset elastomers. The polyurethanes were chemically and mechanically characterized, and their biodegradability was evaluated in compost at 55°C. The nonenergetic and the energetic polyurethanes showed a glass‐transition temperature of −14°C, and −23°C, respectively. The weight loss of the polyurethanes during the composting experiments was monitored. It increased almost linearly with time for both materials. After 20 days, the nonenergetic samples lost about 50% of their mass because of the biodegradation mechanism. Instead, the energetic elastomers lost only about 25% of their initial mass after 25 days. The experimental results revealed that the azide pendant group in the soft segment (the polyether segments) is the main factor that controls the physical, mechanical, and degradation properties of these polyurethane networks. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of full bio-based,fast degradable,and high strength copolyesters: Poly(butylene succinate-sebacicate-salicylicate-malicate)

The presence of petroleum-based monomers in the backbone of poly(butylene succinate-co-adipate) (PBSA) restricts its application in light of increasingly stringent environmental regulations. In this study, a novel full bio-based biodegradable random copolymer poly(butylene succinate-sebacicate-salicylicate-malicate) (PBSSeSa-c-M) was designed and synthesized. The comprehensive study encompassed the structural alterations, properties, and degradation resulting from the inclusion of salicylicate sebacicate and malicate units. The incorporation of salicylic acid effectively enhanced the tensile modulus of the copolymer, due to the effect of rigid benzene ring. Meanwhile, the addition of sebacic acid regulated the degradation rate. The introduction of malic acid significantly improved the rheological properties, endowing the copolymer with exceptional processability. The obtained high molecular weight PBSSeSa-c-M exhibited outstanding film-blowing processability with an intrinsic viscosity of 1.58 dL/g and melt flow rate of 7.34 g/10 min. The tensile modulus reaches 235.43 MPa that is comparable to commercial PBSA. Besides, the degradation of PBSSeSa-c-M reaches 18.92% over 4 weeks, far higher than that of PBSA. In conclusion, this work provides a design and synthesis for a new kind of biodegradable copolyester that satisfies the requirement of rapid degradation in single-use plastics.     

复合抗氧剂对聚丙烯抗氧化性能的研究

采用了5种1010和168国产复合抗氧剂,对其在1102K聚丙烯中的抗氧化性能进行了研究。结果表明:加入复合抗氧剂可以缩短聚丙烯的熔融时间、提高熔体强度、延长抗氧化时间、改善1102K聚丙烯的热稳定性及加工稳定性。