Chapter 13 437 chemistries will affect T g as will blending two polymers with different T g s. The higher the inter- and intra-molecular attractive forces of the polymer the higher the T g .32 An example of the lowering of T g through the use of copolymerization is the incorporation of vinyl acetate into the homopolymer of vinyl pyrrolidone e.g., PVP has a T g of 160°C but when copolymerized with vinyl acetate to produce VP/VA copolymer, the T g of the polymer decreases to 107°C with a 70:30 ratio of VP:VA, 92°C with a 60:40 ratio, and 78°C with a 50:50 ratio. Plasticizers also lower the T g because they disrupt interactive forces between the polymer molecules so that the resultant polymeric film softens. Besides the softening effect of the polymer on the hair, many times the film suffers from being sensitive to humidity. T g can also be lowered by blending polymers with differing T g s. To show this effect, Jachowicz blended various proportions of poly(methylvinylether) (PMVE), a soft hydrophilic polymer with a low T g , with the ethyl ester of PVM/MA copolymer, which forms stiff, hydrophobic films and has a relatively higher T g . As the PMVE polymer ratio was increased, there was observed a lowering of both the T g and the stiffness ratio of the polymer which is defined as the stiffness of the polymer on hair compared to hair itself as measured on the texture analyzer.29 To show the nature of cohesive properties on performance and how this physical parameter can be modified, Wade-Rafferty et al. studied the effect of neutralizers on the cohesive properties of polyacrylate-2 cross-polymer.33 Neutralization with TEA tended to plasticize the resin so that the film created was softer. This was evident by a low elastic modulus as measured through Dynamic Mechanical Analysis (DMA) and a high extension to break with the tensile strength testing of films. TEA, having a relatively large molecular size, interferes with inter-polymeric interaction, thereby softening the film. A harder film resulted using NaOH as the neutralizer for the polyacrylate-2 cross-polymer as shown by a high elastic modulus and low elongation to break in tensile testing.