Molecular Structure of the Hard Segments in Flexible Foams

Abstract

The main basis of structure-property-relationships of polymeric materials is a good characterization of the structure under study. Such is the case for cross linked polyurethanes such as flexible foams. To overcome the problems of solubility of these materials, a selective degradation process was used, leaving the hard segments unaffected. These were then analyzed by MALDI-TOF (Matrix Assisted Laser Desorption-Ionization Time of Flight mass spectrometry). Using these techniques, the length distribution of the hard segments was examined. It was found that the length of the hard segments decreases much slower for polyester foams than for polyether foams. This fact was attributed to a lower solubility of the hard segments in polyethers, which leads to an earlier onset of phase separation. Thus, both mobility and reactivity of the segments in the segregated hard domains are reduced. This fact also explains why the length of the hard segments is only slightly dependent on the water content, or the index, at least in polyether foams. Chemical differences such as the incorporation of polymeric MDI or reactive catalysts could also be shown. Furthermore, this work shows for the first time that presence of cyclic hard segments could be established in a foam.

MALDI-TOF mass spectrometry in the analysis of synthetic polymers

“…That it is possible to characterize the molecular structure of the hard segments of the polyurethane foams widely used in the automotive industry with respect to chain length distribution and end groups has been demonstrated in the authors' lab [91]. It was found that the length of the the hard segments decreases much more slowly for polyester foams than for polyether foams.…”

Reaction Monitoring of Toluenediisocyanate (TDI) Polymerization on a Non-Mixable Aqueous Surface by MALDI Mass Spectrometry

“…[1][2][3] The ability of MALDI TOF MS to monitor the molecular-weight distribution of synthetic polymer samples makes the technique useful for identifying the chemical composition and end-functional groups of polymer samples. [4][5][6] MS techniques have been mainly applied to the investigation of polymer segments, prepared by the hydrolysis of high-molecular-weight polymers.…”

Ageing of Flexible Polyurethane Foams and Determination of their Service Life under Different Climatic Conditions

“…The noted differences in the behaviour of PPU-E-35-0.8 and PPU-75 during climatic ageing are due primarily to the difference in their structure and to the effect of hydrolytic degradation of polyurethanes, fragments of which have different stability [19][20][21][22][23][24][25]. In particular, in terms of susceptibility to hydrolytic degradation, the main fragments of polyurethane foam macromolecules can be placed in the following order: ester > allophanate > biuret > urea > urethane > ether.…”