El branding y el consumidor

2.1 Introduction

In 2000 Petrovic et al. synthesised polyurethanes from halogenated and non- halogenated soybean oil.94 Epoxidised soybean oil 2.1 was ring-opened with methanol, hydrochloric acid, hydrobromic acid or hydrogen (Fig. 2.1) giving monomers with a range of hydroxyl values (Table 2.1).

Figure 2.1: Halogenated and non-halogenated ring-opened soybean oil 2.2-2.5.

Polyol Conversion (%) Hydroxyl value Functionality

Soy-OCH32.2 93 199 3.7

Soy-Cla2.3 94 192 3.8

Soy-Bra2.4 100 182 4.1

Soy-H 2.5 89 212 3.5

a _{All values were calculated on the basis of the analyzed Cl and Br contents and under the assumption that each halogen was}

accompanied by a hydroxy group.

34 Polyols 2.2-2.5 were subsequently polymerised using two isocyanates, PAPI 2901 (a crude MDI, MDI = 4,4’-methylenebis(phenylisocyanate)) and Isonate 2143L (a liquid MDI prepolymer containing carbodiimide bonds) (Fig. 2.2).95 Polymers exhibited high Tg values (above RT) and gave relatively high tensile strength materials with low elongation at break (Table 2.2).

Figure 2.2: Structures of PAPI 2901 and Isonate 2143L.

Polyol Tg

a

(°C) TS (MPa) Elongation (%) YM(MPa) PAPI Isonate PAPI Isonate PAPI Isonate PAPI Isonate Soy-Met 2.2 72 70 45 46 8.4 9 986 979

Soy-Cl 2.3 77 73 48 46 7.5 8.9 1204 1190 Soy-Br 2.4 75 68 44 40 7.7 7.3 1102 955 Soy-H2 2.5 31 34 19 16 29.0 15.4 383 362

a_{Tg determined by DSC. TS = tensile strength, YM = Young’s Modulus}

Table 2.2: Physical properties comparison of soybean oil polyols polyurethanes.

In 2004 Petrovic et al. synthesised six polyurethanes from polyols derived from canola, midoleic sunflower, soybean, linseed, sunflower and corn oils.156 The aim was to identify the effect different triglyceride structures had on the properties of any subsequent MDI derived polyurethanes. The group found that while the position of

35 the reactive sites (Fig. 2.3) in the polyurethanes had little effect on the properties, the cross-linking densities were more important. As expected, higher cross-linking densities gave superior mechanical properties with higher Tg’s (Table 2.3). Mobility of the chains in the networks was inversely proportional to the cross-linking density.

Polyol Tg a

(°C) TS (MPa) Elongation (%) FM (MPa)

Canola 32 22.9 131 353 Midoleic Sunflower 24 14.8 168 10 Soybean 31 20.2 108 312 Linseed 77 56.3 8 2015 Sunflower 32 21.7 107 443 Corn 30 17.7 122 309

a_{Tg determined by DSC. TS = tensile strength, FM = Flexural Modulus}

Table 2.3: Physical properties of 6 renewable polyurethanes derived from different polyols.

Figure 2.3: Reactive sites on different fatty acid chains of triglycerides.

In 2008, Coles et al. synthesised six polyurethane samples, three from, HEMP (hempseed oil), HEAR (high erucic acid rapeseed oil) and rapeseed oil with varying fatty acid compositions and three synthetic mimics of the oils (prepared from glycerol and fatty acids) with similar fatty acid profiles in order to establish whether

36 polymers from natural oils could be mimicked synthetically in the lab.157 Functionalisation of the oils was achieved via hydroxylation of the double bonds using peroxotungstate catalyst (Fig. 2.4).89

Figure 2.4: Schematic representation of hydroxylation reaction using tungsten.

Subsequent polymerisation with MDI also showed the polymers were sensitive to subtle changes in fatty acid composition. It also concluded that synthetic mimics of natural triglyceride based polyurethanes could be prepared and that these have similar properties to the natural oil polymers. This is useful when only small quantities of novel natural oils are available as it allows it to be mimicked in the lab on a larger scale.

In recent years, vegetable oils from renewable sources have proved useful monomers for polymer synthesis in industry. The two most common vegetable oils used industrially, soybean and palm oil, are now deemed to be environmentally unfriendly due to i) the subsequent loss of agricultural land for food use or ii) the large amounts of deforestation required for plantations and therefore loss of ecosystems and increase in greenhouse gas emissions.158-161 As a result of this, alternative sources of renewable triglycerides are required, preferably from waste industrial processes. Cocoa butter 2.9 (Fig. 2.6) is a triglyceride extracted from

37 cocoa beans and is comprised of 64 % saturated and 36 % unsaturated fatty acids (Table 2.4). Cocoa beans are harvested, roasted and then ground into a cocoa liquor. This liquor is then pressed to yield the cocoa butter and cocoa mass. The global production of grinds from cocoa beans in 2012/13 was 4.1 million tonnes with estimates for this year to be 4.2 million tonnes.162 The amount of cocoa butter extracted from the cocoa liquor is 54 % therefore last year’s production of cocoa butter was 2.2 million tonnes.163 Cocoa butter is primarily used in the confectionary industry and makes up approximately 20 % of chocolate.164 It is expected in 2014 the global consumption of chocolate to be 7.3 million tonnes therefore, as cocoa butter makes up on average 20 % of chocolate, 1.46 million tonnes of cocoa butter is required. Some of the remaining cocoa butter is used in the production of body lotions and suppositories by pharmaceutical companies, however a significant amount is discarded as waste. Consequently, it is an ideal candidate as a feedstock to make polymeric materials. The triglyceride structure (Fig. 2.6) is heavily saturated; with on average one oleic acid residue per triglyceride. Titrations were carried out to further corroborate the amount of unsaturation and free fatty acid within the cocoa butter starting material, results gave iodine values of 35 showing on average one double bond per molecule. Acid value titrations gave values of 10 which show a presence of 4 % free fatty acid within the starting material. This was also confirmed with GPC analysis of the cocoa butter monomer where a small percentage of free fatty acid can be observed in the GPC trace (Fig. 2.5) at retention times indicative of pure palmitic, stearic or oleic acid samples.

38

Figure 2.5: GPC trace of cocoa butter starting material.

Figure 2.6: Structure of cocoa butter triglyceride.

Fatty acid Cocoa butter (%a) Palm oil (%a)

Palmitic acid (C16:0) 26 42 Stearic acid (C18:0) 38 4 Oleic acid (C18:1) 32 43 Linoleic acid (C18:2) 3 10 Arachidic acid (C20:0) 1 1 a

Fatty acid composition determined by FAME analysis

Table 2.4: Fatty acid composition of cocoa butter compared to palm oil.