+ Correlating Additives to Deterioration in Historical Rubber Objects Jessica Lafrance

+ Havea Brasiliensis tree cis-1, 4 polyisoprene A dispersion of rubber particles in water 60% water, 36% solid components, 1-1.5% protinacious substances, 1-2.5% resinous substances, 1% sugar, less than 1% ash (Waentig 2008) Must be cured after harvesting After curing it is light in colour, soft, tacky, little mechanical strength Limited number of crosslinks between polymer chains What is Rubber?

+ The Purpose of Additives Mesoamericans coated rubber with earth to reduce the tack Rubber pioneers tested numerous additives to change the properties, most common additives are those related to vulcanisation, others include: Fillers Accelerators Stabilizers Special ingredients Additives were also added for for economic reasons

+ Deterioration of Rubber Oxidation, reactions with sulfur compounds, ozone Accelerated by heat and light Oxidation: new cross links form - rubber hardens, old cross links break – softening, polymer chain breaks – flaking and crumbling Sulfur: creation of hydrogen sulfide, ketones, aldehydes and acids Ozone: addition of double bonds at the surface to form brittle ozonides Additives have an effect on these processes Example: Blooms of waxes or oils on the surface, the absorption of antioxidants by other additives reducing their effectiveness, accelerated deterioration due to minerals

+ This Research Is there a relationship between specific additives and deterioration? Can this be seen through changes in manufacture over time? Is the relationship between the amount of additives present and the level of deterioration linear? Does the inclusion of carbon black have as a great of a protective effect in the presence of other additives prone to UV degradation? Do the additives have a strong effect on the formation of protective surface on rubber?

+ Experimental WORK IN PROGRESS The sample material must meet the following criteria: a) one sample type must include carbon black as an additive, the other sample type must not; b) the type of object must span a wide timeline of production to allow for samples to be taken from objects at intervals in production history (for example, one object from every decade of production); c) the object must have been employed during its working life and exposed to the stresses of use. FTIR-ATR, P-GC, SEM Determination of current level of deterioration and physical properties Correlations will be made between the data and mapped

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