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Negative Pressure Effects during Pure Triacylglyerol Crystallization

2012; American Chemical Society; Volume: 12; Issue: 10 Linguagem: Inglês

10.1021/cg300901v

1528-7505

Robert W. Lencki, R. John Craven,

Polymer Foaming and Composites

Under certain crystallization conditions, β-tending triacylglyerol (TAG) can form cavities within the crystal network, leading to situations where the macroscopic solid density is less than the melted liquid phase. A similar phenomenon, termed negative pressure effect, has been observed during the crystallization of some synthetic polymers. Crystallization of pure β-tending trilaurin just below its melting point with seeding created a crystal structure with millimeter-sized star-like crystals and large air-filled pores, resulting in a macroscopic density (887.5 ± 2.9 kg m–3) that was significantly less than the liquid TAG (897.9 ± 0.6 kg m–3) just above its melting point (Tm). A moderate degree of supercooling (11.5 °C below Tm) led to a platy crystal habit and a higher macroscopic density (1030 ± 2.1 kg m–3). However, higher degrees of supercooling (>25 °C below Tm) created a very fine microporous crystal network with a lower density of 993.2 ± 2.5 kg m–3. It is evident from this work that negative pressure effects can have a significant influence on the macroscopic density of β-tending TAG.