國立虎尾科技大學 |

Development of biocomposites based on cellulosic reinforcements.

紀錄類型:	書目-語言資料,手稿 : Monograph/item
正題名/作者:	Development of biocomposites based on cellulosic reinforcements./
作者:	Sojoudiasli, Helia.
面頁冊數:	1 online resource (158 pages)
附註:	Source: Dissertation Abstracts International, Volume: 76-04C.
Contained By:	Dissertation Abstracts International76-04C.
標題:	Chemical engineering. -
電子資源:	click for full text (PQDT)

Development of biocomposites based on cellulosic reinforcements.
Sojoudiasli, Helia.

Development of biocomposites based on cellulosic reinforcements. - 1 online resource (158 pages)

Source: Dissertation Abstracts International, Volume: 76-04C.

Thesis (Ph.D.)--Ecole Polytechnique, Montreal (Canada), 2017.

Includes bibliographical references

Interesting properties of cellulosic reinforcements such as their low density, renewability, biodegradability, absence of health hazard and high abundance have favored their use in polymer composites. The key issue for polymer composites based on cellulosic reinforcements is the incompatibility between these hydrophilic fillers and non-polar common matrices such as polypropylene (PP) or polylactide (PLA). The main objective of this dissertation is to develop polymer biocomposites with enhanced mechanical properties based on cellulosic reinforcements.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

Subjects--Topical Terms:

555952
Chemical engineering.
Index Terms--Genre/Form:

554714
Electronic books.

Development of biocomposites based on cellulosic reinforcements.
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500 $a Source: Dissertation Abstracts International, Volume: 76-04C.
500 $a Advisers: Pierre Carreau; Marie-Claude Heuzey.
502 $a Thesis (Ph.D.)--Ecole Polytechnique, Montreal (Canada), 2017.
504 $a Includes bibliographical references
520 $a Interesting properties of cellulosic reinforcements such as their low density, renewability, biodegradability, absence of health hazard and high abundance have favored their use in polymer composites. The key issue for polymer composites based on cellulosic reinforcements is the incompatibility between these hydrophilic fillers and non-polar common matrices such as polypropylene (PP) or polylactide (PLA). The main objective of this dissertation is to develop polymer biocomposites with enhanced mechanical properties based on cellulosic reinforcements.
520 $a In the first phase the rheological, mechanical and morphological properties of flax fiber polypropylene composites were investigated. PP grafted maleic anhydride (PPMA) and PP grafted acrylic acid (PPAA) were utilized as compatibilizers. Compounding resulted in a decrease of the mean fiber length by about 70%. It has been observed that both compatibilizers, besides enhancing fiber/polymer interaction, can lead to plasticization and the balance between these competing effects determined the overall rheological behavior of the composite. PPMA and PPAA were effective compatibilizers for PP/flax fiber composites, but their efficiency depended on their melt flow index (MFI) and grafted group content. The tensile modulus of the composite containing 30 wt% flax fibers was improved by 200% and the tensile strength improved by 60% in comparison with the neat PP. The PPMA with the highest content of MA was found to be the most efficient in improving the interface between the PP matrix and the flax fibers, however the plasticizing effect of this coupling agent was significant.
520 $a In the second phase the rheological, mechanical, morphological and thermal properties of PP/cellulose nanocrystal (CNC) composites prepared in the molten state were investigated. PPMA was used as a compatibilizer for this system. The effect of two different processing temperatures with two different molecular weight PPs has been investigated. Degradation of the PP in the presence of CNCs at high processing temperature was shown to have a significant effect on the rheological behavior. The tensile modulus of composites containing 2 wt% CNCs was improved by about 30% and the tensile strength was increased up to 16%, in comparison with the neat matrices. The tensile strain at break of the composites decreased by 17% up to 75% with respect to the matrix, depending on the processing conditions and PP grade. For low molecular weight PP the composites processed at higher temperature showed better mechanical properties. On the other hand, better mechanical properties were obtained for the high molecular weight PP-based composites processed at lower processing temperature. Preparing the low molecular weight PP composites via twin-screw extrusion was shown to be more efficient than using an internal batch mixer. The tensile modulus of the PP/CNC composites could be fairly well described by a model proposed by Nielsen based on the Halpin-Tsai equation. Finally, it was observed that the PP/CNC composites exhibited a good ductility, with their strain at break varying between 43 and 73% of the PP value in comparison to the PP/ flax composites, which were brittle and their strain at break was less than 0.06 of that of the matrix.
520 $a In the last phase, the potential use of dimethyl sulfoxide (DMSO) as a dispersing medium for CNCs and modified CNCs (mCNC) was investigated. Cellulose nanocrystals have been modified via grafting an organic acid chloride on the surface of the nanoparticles. The efficiency of surface modification has been confirmed by X-ray photoelectron spectroscopy (XPS). The rheological properties of CNC suspensions did not change significantly with time at room temperature, but the CNC suspensions at 70 °C underwent gel formation, even at a very low concentration (1 wt%) after one day. For suspensions containing 3 wt% CNCs, the complex viscosity at 70 °C increased by almost 4 decades after one day. For the mCNCs in DMSO a weak gel was formed from the first day and temperature did not affect the gelation and changes in the complex viscosity after one day were marginal. The rheological properties of the mCNC gels at 70 °C were found to be much lower than those of the CNC gels. Finally, the effect of adding 10 wt% of polylactide (PLA) to the solvent on the rheological properties of CNC and mCNC suspensions was investigated. PLA did not prevent gel formation for the CNC suspensions. However, the reduced viscosity and storage modulus of the CNC and mCNC suspensions in PLA/ DMSO were considerably lower than those of samples without PLA. This has been attributed to poor interactions between the nanoparticles and the PLA chains and the decreased influence of the Brownian motion due the increased viscosity of the suspending medium. To the best of our knowledge this is the first time that the gelation of CNC and mCNC suspensions at very low content in a polar non-aqueous, safe solvent like DMSO has been investigated.
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