Relationship between structure and aromatic solvent permeability of crosslinked polyurethanes based on hyperbranched polyesters

Abstract

This work investigates the relationship between structure and aromatic solvent permeability of polyurethanes based on trimethylolpropane (TMP) as a classical crosslinker and self‐made hyperbranched polyesters (HBPEs) as newly developed crosslinking agents. For this purpose three groups of samples were synthesized using toluene diisocyanate, poly(tetramethylene glycol) and different pseudo‐generation numbers of crosslinkers in the variable hard segment content. The results obtained from characterization tests indicate that replacing TMP by HBPE leads to an increase of crosslink density resulting in significant reduction of sorption capacity and conversely leads to an increase of the diffusion coefficient due to the lower glass transition temperature (Tg) of soft segments. In this way, the toluene permeability of hyperbranched polyurethane (HBPU) is considerably lower than that of classical polyurethane. The HBPUs with sufficient amount of hard segment have the lowest solvent uptake and diffusion coefficient leading to optimal barrier performance. By increasing the generation number of HBPE, the crosslink density of HBPU increases, but the crystallinity as well as Tg of soft segments decrease. These two contradictory changing trends of the structural characteristics cause a slight decrease in sorption coefficient of membranes and an increase of diffusivity. Therefore the barrier performance of HBPUs is weakened with increasing generation number of crosslinkers. © 2015 Society of Chemical Industry

Kinetic and equilibrium sorption of organic liquids and vapors in Matrimid

“…The films submerged in the liquids of interest at the specified temperature were removed, rapidly and carefully blotted dry within 10-15 seconds, and were placed on a balance for mass measurement. This 'blot and dry' technique is seen in several literature examples that examined liquid sorption in polymer films [11,38,39]. It is generally assumed that the mass of penetrant that diffuses and evaporates from the polymer surface is negligible compared to the total equilibrium amount sorbed.…”

The influence of polycaprolactone content on the surface properties of polyurethane networks

“…Values of the swelling rate constant k 2 of PUNs in THF and water generally increase (with minor deviations) with SS content increase, due to the decrease of the crosslinking density of PUNs. Moreover, the existence of microphase separation and the shape and size of the SS and HS have a large impact on the swelling rate and passage of the solvent molecules through the polymer network 30,36 . Functionality of the applied crosslinker is another factor that significantly affects swelling rate of PUNs.…”

“…Moreover, the existence of microphase separation and the shape and size of the SS and HS have a large impact on the swelling rate and passage of the solvent molecules through the polymer network. 30,36 Functionality of the applied crosslinker is another factor that significantly affects swelling rate of PUNs. Namely, crosslinking density of PUNs based on PCL, IPDI, and hyperbranched polyester of the third pseudo generation (BH-30) is approximately twice as big as crosslinking density of PUNs prepared with BH-20.…”

Immobilization of heparin on chitosan-grafted polyurethane films to enhance anti-adhesive and antibacterial properties

“…In our study, although there was a high degree of crosslinking, Tg was found at −54°C since the high molecular weight of the soft segment partly overcame the rigidity provided by crosslinking. 36…”

“…In our study, although there was a high degree of crosslinking, Tg was found at -54°C since the high molecular weight of the soft segment partly overcame the rigidity provided by crosslinking. 36 Thermomechanic properties. The behavior of the materials under dynamic conditions in a certain temperature range and at 1 Hz is given in Figure 4(a).…”