title: Production and assessment of Poly(Lactic Acid) matrix composites reinforced with regenerated cellulose fibres for fused deposition modelling

authors: Gauss, Christian

subjects: 3D printing technology

abstract: Additive manufacturing can be a valuable tool to process polymeric composites reinforced with bio-based fibres, extending their use and opening new opportunities for more environmentally friendly materials. In this work, poly(lactic acid) (PLA) composites reinforced with regenerated cellulose fibres (lyocell) were processed into novel filaments and used for 3D printing. The Young's modulus of the filaments increased with the addition of fibres, but substantial porosity was observed in formulations with 20 and 30 wt% of fibre content. Nonetheless, the composites were easily printed, and the formulation with 10 wt% of fibres presented the best tensile properties of 3D printed samples with average tensile strength, Young's modulus, and strain at break of 64.2 MPa, 4.56 GPa, and 4.93%, respectively. It has been shown in this study that the printing process contributes to fibre alignment with small variations depending on the printing speed. Printed composite samples also had superior thermo-mechanical stability with a storage modulus up to 72 times higher than for neat PLA at 80 °C after the composite samples were heat-treated. In general, this work supports the potential use of regenerated cellulose fibres to reinforce PLA for 3D printing applications.

text: Production and assessment of Poly(Lactic Acid) matrix composites reinforced with regenerated cellulose fibres for fused deposition modelling Additive manufacturing can be a valuable tool to process polymeric composites reinforced with bio-based fibres, extending their use and opening new opportunities for more environmentally friendly materials. In this work, poly(lactic acid) (PLA) composites reinforced with regenerated cellulose fibres (lyocell) were processed into novel filaments and used for 3D printing. The Young's modulus of the filaments increased with the addition of fibres, but substantial porosity was observed in formulations with 20 and 30 wt% of fibre content. Nonetheless, the composites were easily printed, and the formulation with 10 wt% of fibres presented the best tensile properties of 3D printed samples with average tensile strength, Young's modulus, and strain at break of 64.2 MPa, 4.56 GPa, and 4.93%, respectively. It has been shown in this study that the printing process contributes to fibre alignment with small variations depending on the printing speed. Printed composite samples also had superior thermo-mechanical stability with a storage modulus up to 72 times higher than for neat PLA at 80 °C after the composite samples were heat-treated. In general, this work supports the potential use of regenerated cellulose fibres to reinforce PLA for 3D printing applications.

year: 2022-09-23

title: Enzyme activity and dynamics: xylanase activity in the absence of fast anharmonic dynamics

authors: Dunn, Rachel V.

subjects: cryoenzymology

abstract: The activity and dynamics of a simple, single subunit enzyme, the xylanase from Thermotoga maritima strain Fj SS3B.1 have been measured under similar conditions, from -70 to +10 °C. The internal motions of the enzyme, as evidenced by neutron scattering, undergo a sharp transition within this temperature range; they show no evidence for picosecond-timescale anharmonic behaviour (e.g. local diffusive motions or jumps between alternative conformations) at temperatures below -50 °C, whereas these motions are strongly activated at higher temperatures. The activity follows Arrhenius behaviour over the whole of the temperature range investigated, -70 to +10 °C. The results indicate that a temperature range exists over which the enzyme rate-limiting step is independent of fast anharmonic dynamics.

text: Enzyme activity and dynamics: xylanase activity in the absence of fast anharmonic dynamics The activity and dynamics of a simple, single subunit enzyme, the xylanase from Thermotoga maritima strain Fj SS3B.1 have been measured under similar conditions, from -70 to +10 °C. The internal motions of the enzyme, as evidenced by neutron scattering, undergo a sharp transition within this temperature range; they show no evidence for picosecond-timescale anharmonic behaviour (e.g. local diffusive motions or jumps between alternative conformations) at temperatures below -50 °C, whereas these motions are strongly activated at higher temperatures. The activity follows Arrhenius behaviour over the whole of the temperature range investigated, -70 to +10 °C. The results indicate that a temperature range exists over which the enzyme rate-limiting step is independent of fast anharmonic dynamics.

year: 2000

title: E Kui Rāwinia

authors: Maxwell, Te Kahautu

abstract: E Kui Rāwinia; this composition is a lament to a Te Whakatōhea chieftainess who married the paramount Ngāti Porou rangatira Tokorua (Toko) Te Kani. This composition recites the genealogical ties between the East Coast iwi to Te Whakatōhea. The composition paints a spiritual journey for Rāwinia to return to her birth place Ōpōtiki. The journey names geographical features of importance to map her journey home. This composition gained first place for composition. Performed by Ōpōtiki Mai Tawhiti at the Te Matatini World Championship Kapa Haka competition.

text: E Kui Rāwinia E Kui Rāwinia; this composition is a lament to a Te Whakatōhea chieftainess who married the paramount Ngāti Porou rangatira Tokorua (Toko) Te Kani. This composition recites the genealogical ties between the East Coast iwi to Te Whakatōhea. The composition paints a spiritual journey for Rāwinia to return to her birth place Ōpōtiki. The journey names geographical features of importance to map her journey home. This composition gained first place for composition. Performed by Ōpōtiki Mai Tawhiti at the Te Matatini World Championship Kapa Haka competition.

year: 2015