Protein-functionalized cellulose fibrils, having various amounts of covalently bonded proteins at their surface, were successfully extracted from the tunic of Pyura chilensis tunicates using successive alkaline extractions. Pure cellulose fibrils were also obtained by further bleaching and were used as reference material. Extraction yields of protein-functionalized cellulose fibrils were within the range of 62-76% by weight based on the dry initial tunic powder. Fourier-transform infrared and Raman spectroscopy confirmed the preservation of residual protein at the surface of cellulose fibrils, which was then quantified by X-ray photoelectron spectroscopy. The protein-functionalized cellulose fibrils were found to have relatively high crystallinity and their cellulose I crystalline structure was preserved upon applying alkaline treatments. The extracted cellulosic materials were found to be constituted of fibrils having a ribbon-like morphology with widths ranging from ∼30 nm up to ∼400 nm. These protein-functionalized cellulose fibrils were found to have outstanding thermal stability with one of them having onset and peak degradation temperatures of ∼350 and 374 °C, respectively. These values were found to be 24 and 41 °C higher than for bleached cellulose.

ABSTRACT:The mechanical behavior of semicrystalline Nylon 11 was studied at strain rates between 10 Ϫ3 and 8800 s Ϫ1. X-ray diffraction and DSC were employed to examine the crystal structure and the crystallinity content. The as-received material comprised a mixed structure of a predominately triclinic (␣) form. DSC revealed that the material gave rise to two melting peaks. The compressive flow stress of Nylon 11 experienced a large increase at 1200 s Ϫ1 and decreased at higher strain rates. The maximum level of the flow stress corresponded with a higher level of crystallinity and a structure mainly of a pseudohexagonal form. The subsequent drop in stress at higher rates was associated with a decrease in the crystallinity content and a mixed crystal structure, different from that observed in the as-received material. After compression, the low melting peak disappeared and the material melted over an increased temperature range.

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During low rate deformation in tension semi-crystalline polymers can undergo a strain induced c r y s m o n during deformation which leads to increases in flow stress. This work extends studies of crystallinity in the polymers PM, PEEK and PET to compression at high strain rates at a variety of temperatures. All three polymers show large increases in crystallinity when tested at high rates with PEK and PEEK showing increases only at rates of 10' 1s. It is speculated that the rapid increases in flow stress reported in polymers at high strain rates may be due to the rapidity of strain induced crystallisation at these strain rates.Rksumk: Pendant une deformation B basse vitesse en traction, les polymkres semi-cristallins peuvent subu une cristallisation induite par deformation qui conduit B une augmentation de la contrainte d'ecoulement. Ce travail concerne 1'Ctude de la cristallinit6 des polymkres PEK, PEEK et PET provoquee par la deformation en compression I vitesses de dkformation klevdes et I differentes temp8ratures. Les trois polymeres montrent une forte augmentation de cristallinitk lorsqu'ils sont testes B grande vitesse; le PEK et le PEEK ne montrant qu'une augmentation qulB partir d'une vitesse de 10' 1s. On suppose que I'augmentation rapide de la contminte d'6coulement revel6e par les polymkres vitesse &levee pourrait dtre due B la rapidit6 de la cristallisation induite B ces vitesses de deformation correspondantes.

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