Effect of Hyperbranched Polyester on Modification of Epoxy Resins Cured with Anhydride

Epoxy resins are widely used in coatings, adhesives and polymer composites, but the applications of cured epoxy resins are often restricted by their poor toughness. HBP can be used as toughener to improve the toughness of epoxy resins due to its high-dens…     

Fully aromatic liquid crystalline homopolyesters and copolyesters of 1,1′-binaphthyl-4,4′-diol

A series of fully aromatic, thermotropic polyesters based on 1,1′-binaphthyl-4,4′-diol, BND, was prepared by the melt polycondensation method and characterized for their thermotropic behavior by a variety of experimental techniques. The homopolymer of BND with terephthalic acid formed a nematic melt at 353°C. In contrast, the polyester from BND and 2,6-naphthalenedicarboxylic acid had a melting transition, T_m, above 400°C, so it was not possible with the equipment available to determine whether it formed a nematic melt. All of the copolymers of BND formed nematic melts at much lower T_m values than those of its respective homopolymers, as expected, because of the copolymerization effect of the added monomer. Moreover, all of the copolymers had higher glass transition temperatures, T_g, than those of other liquid crystalline polyesters and higher thermal stabilities. © 1994 John Wiley & Sons, Inc.     

Polymeric phosphonium salts as a novel class of cationic biocides. V. Synthesis and antibacterial activity of polyesters releasing phosphonium biocides

Polyesters were prepared which retained phosphonium biocides as counter ions of sodium sulfonate moieties incorporated into the polymers, and surface antibacterial activity of the polyester films against Staphylococcus aureus and Escherichia coli was explored. These films exhibited a high surface antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity was affected by the structure and the compositional ratio of the phosphonium salts. Amount of the released phosphonium salts was very small, so that liberation of the phosphonium biocides can be expected to occur over a long period. Morphological changes of the cells of S. aureus and E. coli in contact with the polyester films were evaluated by scanning electron microscopy. It was found that the surface antibacterial activity of the polyester films was rather bacteriostatic than bactericidal as evidenced by no morphological changes of the bacterial cells in contact with the phosphonium biocides © 1993 John Wiley & Sons, Inc.     

Rheological behavior in blends of PET with ionomeric polyester

The rheological behavior and the morphology in blends of polyethylene terephthalate (PET) with ionomeric polyester were investigated over a wide range of different blending ratios. The ionomeric polyester is derived from PET modified through copolycondensation with sulfonate moiety, sodiosulfo isophthalate (Na-SIP), iso-phthalic acid (IPA) and polyethylene glycol (PEG). The results showed that the apparent viscosity and non-Newtonian index of the PET/ionomeric polyester blend system had a nonlinearity change with the change of the blend ratio of PET/ionomeric polyester. The anomaly of the viscous flow activation energy change was found as the content of ionomeric polyester was about 40% (w/w) in the blend system, suggesting the presence of physical cross-linked structure formed by strong polar tangling points and the phase separation owing to poor compatibility between the PET and ionomeric polyester. The morphology and thermal behavior of the blends were observed, respectively, with differential scanning calorimetry (DSC) and atomic force microscopy (AMF).     

Preparation, characterization and effect of annealing on performance of cellulose acetate/sulfonated polysulfone and cellulose acetate/epoxy resin blend ultrafiltration membranes

Polymeric membranes based on cellulose acetate (CA)--sulfonated polysulfone blends at three different polymer compositions were prepared by solution blending and phase inversion technique, characterized and subjected to annealing at 70, 80 and 90 °C. The permeate water flux, separation of bovine serum albumin and its flux by the blend membranes before and after thermal treatment, have been compared and discussed. Similarly, CA and epoxy resin (diglycidyl ether of bisphenol-A) were blended in various compositions, in the presence and in the absence of polyethyleneglycol 600 as non-solvent additive, using N,N^′-dimethylformamide as solvent, and used for preparing ultraflltration membranes by phase inversion technique. The polymer blend composition, additive concentration, casting and gelation conditions were optimized. Blend membranes were characterized in terms of compaction, pure water flux, water content and membrane resistance. The effects of polymer blend composition and additive concentration on the above parameters were determined and the results are discussed.     

MONTE CARLO SIMULATION OF TRIBLOCK COPOLYMER/HOMOPOLYMER BLEND FILMS

1. INTRODUCTION The extensive applications of block copolymer have been studied in detail due to their special molecular architecture and characteristic [1,2]. Recently, many studies including theoretical analysis and experimental techniques have addressed the polymer blend system of diblock copolymer/homopolymer [3~9]. An early investigation presented a quantitative analysis of homopolymer distributions in well-ordered copolymer microdomains through mixing polystyrene (PS) or poly methyl…     

Effects of various donor: acceptor blend ratios on photophysical properties in non-fullerene organic bulk heterojunctions

In this work, the donor:acceptor ratio effected photophysical properties of non-fullerene organic solar cells are comparatively investigated. Effective transportation of the photo-generated charge carriers can be obtained with the PDBD-T:ITIC ratio variation. There is no significant energy loss variation exists in the process of changing the D:A ratio.     

Ternary upper-critical-solution-temperature behavior in a blend system comprising poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene

 Upper-critical-solution-temperature (UCST) behavior in a ternary blend of poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene is reported. The as-cast ternary blend is immiscible at ambient conditions and comprises two different phases, and, however, turns into a miscible system above the “clarity point” ranging from 160 to 300 °C for different ternary compositions. The maximum clarity point is labeled as the UCST for the ternary system, which is about 295 °C. Above the clarity point, the originally immiscible ternary blend turned into one miscible phase. Owing to the thermodynamic UCST behavior and kinetic hindrance, the immiscible ternary polymer blend can be locked into a pseudo-miscible state if it is heated to a temperature above the clarity point followed by a rapid-cooling processing scheme. The quenched ternary blend can remain in a pseudo-miscible state as long as the service temperature does not exceed the glass-transition temperature of the blend. Received: 17 July 2001 Accepted: 3 October 2001     

Liquefaction of corn stover and preparation of polyester from the liquefied polyol

This research investigated a novel process to prepare polyester from corn stover through liquefaction and crosslinking processes. First, corn stover was liquefied in organic solvents (90 wt% ethylene glycol and 10 wt% ethylene carbonate) with catalysts at moderate temperature under atmospheric pressure. The effect of liquefaction temperature, biomass content, and type of catalyst, such H₂SO₄, HCl, H₃PO₄, and ZnCl₂, was evaluated. Higher liquefaction yield was achieved in 2 wt% sulfuric acid, 1/4 (w/w) stover to liquefying reagent ratio; 160°C temperature, in 2h. The liquefied corn stover was rich in polyols, which can be directly used as feedstock for making polymers without further separation or purification. Second, polyester was made from the liquefied corn stover by crosslinking with multifunctional carboxylic acids and/or cyclic acid anhydrides. The tensile strength of polyester is about 5 MPa and the elongation is around 35%. The polyester is stable in cold water and organic solvents and readily biodegradable as indicated by 82% weight loss when buried in damp soil for 10 mo. The results indicate that this novel polyester could be used for the biodegradable garden mulch film production.     

Exchange reactions occurring through active chain ends: Melt mixing of nylon 6 and polycarbonate

The chemical reactions occurring in the melt mixing of nylon6/polycarbonate (Ny6/PC) at 240°C were investigated. The reaction of equimolar Ny6/PC blends can be reconciled within the overall scheme of an exchange reaction occurring with the attack of active amino terminals on the inner carbonate groups. We have performed the synthesis of low molecular weight amino-terminated nylon 6 and the effect of the active amino terminal groups on the exchange kinetics was investigated. The exchange reaction yields sizeable amounts of copolymer, in fact after 75 min of melt mixing the (initially equimolar) blend contains 30 mol of unreacted PC and 70 mol of Ny6/PC copolymer (all the Ny6 was therefore incorporated in the copolymer). Trifluoroacetylation of nylon 6 was used to produce CHCl₃-soluble Ny6/PC copolymers, that could be analyzed by NMR. The NMR analysis yielded, beside the copolymer composition, evidence of the presence of urethane units interconnecting the Ny6 and PC blocks. The amount of urethane units increased with the reaction time, indicating a reduction of the block size as a function of the extent of exchange. Our study established the structure of the products formed, provided the materials balance of the process, and investigated some salient kinetic aspects. A thermal degradation study was also performed by thermogravimetry and direct pyrolysis mass spectrometry, to identify the products formed in the thermal treatment of the blends and to investigate the possible role of the inner amide groups in the intermolecular exchange reactions occurring between Ny6 and PC. Our results prove that these reactions occur above 300°C, and that only the cleavage of carbonate groups, by means of Ny6 amino end groups, is actually occurring at 240°C. © 1994 John Wiley & Sons, Inc.