Structure-property relationships in polyurethanes from lignin
| dc.contributor.author | Saraf, Vasudev P. | en |
| dc.contributor.department | Chemical Engineering | en |
| dc.date.accessioned | 2021-10-26T20:09:48Z | en |
| dc.date.available | 2021-10-26T20:09:48Z | en |
| dc.date.issued | 1983 | en |
| dc.description.abstract | Lignin based polyurethane films were synthesized by solution casting from hydroxypropyl lignins and diisocyanates. Kraft and steam explosion lignin, hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI), were used for the study. It was found necessary to use stoichiometric excess amounts of diisocyanates in the synthesis of the thermosetting polyurethanes. The investigation primarily addresses the effect of synthesis variables and soft segment incorporation on the thermal and mechanical properties. The first part of the study examined the effect of lignin type, of diisocyanate type and of composition (NCO/OH ratio). Stoichiometric excess was found to cause a significant increase in the glass transition temperature. Use of HDI resulted in films with lower moduli as compared to TDI. NCO/OH stoichiometry variation had no noticeable effect on modulus or tensile strength. In the second part of the study involving incorporation of soft segments, four polyethylene glycols were used. No soft segment phase in the network was detectable by differential scanning calorimetry or dynamic mechanical analysis. The glass transition temperature of lignin phase dropped by as much as 70°C for HDI and 115°C for TDI based polyurethanes with inclusion of glycols up to 25% of the polyol weight. The swelling tendencies showed an expected increase with glycol content. Effect on mechanical properties were more pronounced in HOI than in TDI based polyurethanes. The modulus and tensile strength decreased, and the ultimate strain values increased with polyethylene glycol content. Last part of the study involved synthesis and characterization of kraft polyurethanes with polybutadiene glycol with functionality in excess of 2.0. The miscibility of this phase with hydroxypropyl lignin phase was found to be poor as observed by scanning electron microscopy. Glass transition temperature for the lignin phase increased with polybutadiene glycol content of the polyurethane in contrast to observations on polyethylene glycol modified polyurethanes. There were no significant improvements in tensile properties. The incompatibility of soft segments was seen to result in a more condensed lignin phase, and was thus found to be the major limitation in its applicability in modification of the network properties. The study demonstrates the utility of concept of network modification in the synthesis of lignin based thermosetting polyurethanes. By proper choice of synthesis variables, and with the use of glycols of sufficient compatibility, significant improvements in properties can be realised in these polyurethanes. | en |
| dc.description.degree | M.S. | en |
| dc.format.extent | xi, 135 leaves | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.uri | http://hdl.handle.net/10919/106007 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Polytechnic Institute and State University | en |
| dc.relation.isformatof | OCLC# 10281958 | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject.lcc | LD5655.V855 1983.S2685 | en |
| dc.subject.lcsh | Lignin | en |
| dc.subject.lcsh | Polyurethanes | en |
| dc.title | Structure-property relationships in polyurethanes from lignin | en |
| dc.type | Thesis | en |
| dc.type.dcmitype | Text | en |
| thesis.degree.discipline | Chemical Engineering | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | M.S. | en |
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