Determination of the heat of fusion of isotactic poly(methyl methacrylate)

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Abstract
The heat of fusion (ΔHu) of isotactic poly(methyl methacrylate) (PMMA) was determined from the combined linear regression analysis of x‐ray diffraction data and differential scanning calorimetry. By means of two sample preparation techniques to reduce crystallinity, a thermal pretreatment in which a partial melt and quench cycle was utilized, and a mechanical mixture in which a semicrystalline and amorphous material were blended, a value for ΔHu = 1200 ± 80 cal/mole (100 g) was found. The present result represents the first measurement of ΔHu for an acrylic polymer and yields G(‐units) = 12 from cryoscopic measurements for the chemical changes caused by high energy irradiation.