Polyurea/Polyurethanes from Vegetable Oils

A second type of polyol was synthesised, one that contained not only two hydroxyl groups but also a more nucleophilic amine derivative RS(104a). Rapeseed oil was reacted with ethylenediamine, without solvent as in section 2.4.1 to give a fatty amide. The unsaturation was then removed via epoxidation using mCPBA in chloroform, followed by ring opening of the epoxide using orthophosphoric acid at 100 °C to give a diol RS(104a) (Figure 4.20), or in some cases a polyol due to the differing amounts of unsaturation found in the fatty acid chains of rapeseed oil.

Figure 4.20: Example of a diol made from a dihydroxylated fatty amide

On reaction of this polyol RS(104a) with (5.59 g) of MDI in a one to one mole ratio with 100 mL of chloroform we found that gelation occurred almost instantly upon heating the mixture indicating rapid reaction and potential cross-linking of the material. This was to be expected as there are at least three nucleophilic components to the polyol. It is known that changing the temperature and concentration of polymerisation can affect the rates of cross-linking reactions. Carrying the reaction out in a less concentrated solution allowed polymeric material with less cross-linking

130 to be isolated and tests carried out. Terminal amines are often reacted with diisocyanates resulting in polyureas (Figure 4.21). An example of where polyurethanes and polyureas are copolymerised is in spandex, the strong, elastic polymer often used in clothing.202

Figure 4.21: Generic polyurea where R can be an aromatic or aliphatic portion of diisocyanate.

Further polyurethanes were prepared from polyol RS(104a) and MDI using the three commercially available polyols (PEG 400, PEG 3350 and butanediol) in the same way as with the diethanolamine derived polyols (CB(30)/CB102, RS(30)/RS(102)) investigated previously. The thermal and swelling properties were then investigated and compared with the diethanolamine polyurethane set.

PEG/BD Physical properties Pull apart by hand?

N/A Soft elastic solid Yes

BD Hard brittle solid Yes

PEG400 Soft tough solid No

PEG3350 Hard tough solid No

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PEG/BD Cross-link density

(mol/cm3) x10-4 Swell % (water) N/A 297.9 3.6 BD 163.7 5.3 PEG400 104.3 7.4 PEG3350 95.3

Table 4.7: Swelling and cross-link results of polyurethanes derived from RS(104a).

Mechanical testing was unable to be carried out due to failure to produce suitable ‘dog-bone’ samples, as obvious shrinkage was observed during curing. Shrinkage is often found in thermoset polyurethanes, mainly when materials have high exotherms. Although not measured it is likely the large number of polymerisable groups on the polyol (as well as the more nucleophilic amine group) would be responsible for this. The samples however were extremely tough, and relatively resilient towards solvent and water. A general trend was seen with the swelling results. With the higher MWT commercial diols used you found that more swelling occurred in both water and toluene. DSC of these PU samples also yielded no Tg or melt/softening points. Cross-linking density was calculated however, and are shown in Table 4.7. In comparison to those calculated for the PU samples derived from RS(102), CB(102), RS(30), CB(30) the densities for RS(104a) are much higher which is likely to be caused by the terminal amine group and extra alcohol groups found in the side- chains of rapeseed derivatives (Figure 4.20) that is found in this polyol. It can also be noted that the cross-linking density decreases as longer chain diols (e.g. PEG 3350) are introduced. This may be due to the components capable of cross-linking being separated by longer chain diols.

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4.6. Summary and Conclusions

Diols (30) can be made from the amidation of triglycerides (1) with diethanolamine

(62e) and sodium methoxide. Further epoxidation can take place at the unsaturation in the fatty chains to yield functionalised diols (102). These diols (CB(30)/CB(102),

RS(30)/RS(102)) can be used successfully in the preparation of polyurethanes giving solid brittle polyurethanes with a glassy appearance. The addition of commercial polyols (1,4-butanediol, PEG400 and PEG3350) again yield solid PU samples. Significant cross-linking occurred (presumably due to allophanates and biurets) and this was responsible for the brittle materials obtained. Cross-linking was greater for epoxidised monomers (102) where further cross-linking can occur via ring-opening of the epoxides under the reaction conditions (presumably by nucleophilic hydroxyl functionality). The most flexible material (with 125 % elongation on break) RS(102)/PEG400 had the lowest cross-linking density as expected. In general the tensile strength of the PU’s produced were lower than those of Campanella et al who produced materials from monoglycerides of soybean oil (1.7 – 2.3 MPa), although no cross-linking data is presented to allow direct comparisons

PU samples prepared with 1,4-butanediol became more brittle and fell apart very easily. The addition of PEG 400 and 3350 yielded slightly more elastic samples, however they were still fairly brittle to the touch and could be pulled apart by hand.

The PU samples prepared from RS(104a), especially when mixed with PEG400 and PEG3350, gave both a hard tough and soft flexible PU respectively. However with the method used in the preparation of these PU samples shrinkage was observed on curing making it difficult to produce good samples for further testing. Cross-linking density for these polyols indicate a higher amount of cross-linking, which would be

133 attributed to the terminal amine found in this polyol as well as the extra alcohol groups arising from linolenic and linoleic side-chains.

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Chapter 5.0 Synthesis of Polyol Oligomers as Potential Monomers for PU