Search

A good way of achieving compatibility in polymer blends of poly(styrene-co-acrylonitrile) (S/AN) and bisphenol A polycarbonate (PC) is the chemical modification of S/AN in the melt. A catalyzed reaction of the nitrile groups with a substituted 2-amino alcohol or 2-amino phenol resulted in a conversion of nitrile groups of 55–75% in 60 min. The introduced heterocyclic structures were ethyl hydroxymethyl oxazoline (EHMOXA) and benzoxazole (BenzOXA), respectively. The use of dibutyltin oxide as a catalyst led to the highest efficiency. The modified polymer was characterized by Fourier transform infrared and NMR spectroscopy, elemental analysis, and reactions with organic acids and anhydrides. The modified S/AN showed good technical compatibility (single glass-transition temperature) with PC in blends made from solution and from the melt. All blends were characterized with oscillating rheometry and differential scanning calorimetry. Rheological measurements showed that EHMOXA–S/AN reacted with PC and had crosslinked structures, whereas BenzOXA–S/AN showed compatibilization without any (crosslinking) reaction. The melt blends of BenzOXA–S/AN and PC showed a downward shift in the complex viscosity due to the influence of the BenzOXA group. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2322–2332, 2003

Soluble and thermally stable polycarbonate polyurethane elastomers were synthesized through a solvent-free and nonisocyanate melt transesterification process. The conditions of this process were studied, and the optimum conditions were as follows: the catalyst dibutyltin oxide dosage was 0.125 wt %, the raw material molar (n) ratio of dimethyl 1,6-hexamethylene dicarbamate (HDC) to poly(carbonate macrodiol) (PCDL) was n(HDC)/n(PCDL) = 1:0.99, the reactants were prepolymerized under 100°C for 1 h and then under 185°C and a high vacuum for 4 h. Three different PCDLs were selected to participate in the reaction under the conditions mentioned previously, and their structures were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The products obtained from this process were still stable under 280°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41377.

A crystalline condensate of dibutyltin oxide and tributyl phosphate (Sn-P-c) was more effective than the stannous octoate and dibutyltin dilaurate in accelerating the curing of the epoxy resin/4,4′-diamino diphenyl sulfone (DDS) system, based on an equal tin concentration. Water took part in the reaction and played an important role in the morphology and mechanical properties of the cured resin when Sn-P-c was used as the accelerator. In the presence of Sn-P-c, water first reacted with glycidyl ether to yield glycerol ether; the yielded hydroxyl group may further catalyze the amino/epoxy group reaction. In the absence of water or polar hydroxyl additives, Sn-P-c did not completely dissolve in the resin systems, and the cured resin was translucent material with poor mechanical strength. In the presence of a small amount of water, the cured material became transparent. Both flexural strength and maximum deflection were increased greatly. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1229–1236, 2001

When a crystalline Bu2SnO-Bu3PO4 condensate was used as a catalyst for the curing of the Epon 828/DDS system, the addition of hydroxyl group to epoxy group took place. On the basis of this reaction, direct employment of poly(tetramethylene) glycols (PTMG) as toughener for the epoxy resin system was successful. Morphology of the modified resin depended on the molecular weight and the concentration of PTMG. With the incorporation of a small amount of PTMG, the critical fracture energy of the cured resin was improved greatly, while the flexural strength and the modulus were less influenced. A slight enhancement in glass transition temperature (Tg) of the modified resin was found up to the PTMG concentration of 5 phr; further increase of the PTMG concentration caused a significant lowering of Tg. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1237–1242, 2001

PE and PBT are known to be incompatible polymers. A grafted copolymer PBT-EVA has been generated as a compatibilizer in situ during the processing operation by redistributive transesterification between PBT and EVA in the presence of dibutyl tin oxide (DBTO). This copolymer has been isolated by selective extractions from PBT/EVA/DBTO (49.5/49.5/1% in weight) blend after processing in the melt. It has been evidenced by a 1H-NMR study. This copolymer presents all the resonances of PBT and EVA sequences and some others that have been assigned specificaly to grafting. To achieve these assignments, a model compound obtained by transesterification of EVA with methyl benzoate has been used. When the melt conditions enable synthesis of the grafted copolymer PBT-EVA in situ during processing operations, important changes in the morphology of PE/PBT/EVA/DBTO blends are observed. SEM analysis shows a decrease of PBT particle size and a good adhesion between the PBT and PE phase. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2457–2469, 1997

The ester–amide exchange reaction between polyamide 6 (PA6) and ethylene-vinyl acetate rubber (EVM) with dibutyltin oxide (DBTO) as a catalyst took place during melt blending, leading to the formation of PA6-grafted EVM copolymer (EVM-g-PA6) and acetamide-terminated PA6. The exchange reaction extent, expressed by the percentage content of the acetate groups taking part in the exchange reaction, was 5.9 mol %, and the yield of EVM-g-PA6 copolymer was 6.8 wt % for PA6/EVM/DBTO (60/40/1) blend at 230°C for 60 min. The number-average molecular weight of PA6 branches in EVM-g-PA6 was ∼278 g/mol as evaluated from nuclear magnetic resonance spectra. The reaction kinetic parameters were calculated according to a second-order reversible reaction mechanism. The rate constant was dependent on the catalyst concentration, PA6/EVM ratio, and shearing conditions. In this article, the characterized ester–amide exchange reaction between PA6 and EVM will guide the fabrication of novel EVM-based graft copolymers and high-performance PA6/EVM thermoplastic elastomers for engineering applications.