scholarly journals Ligno-Cellulosic Fibre Sized with Nucleating Agents Promoting Transcrystallinity in Isotactic Polypropylene Composites

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1259 ◽  
Author(s):  
Armin Thumm ◽  
Regis Risani ◽  
Alan Dickson ◽  
Mathias Sorieul
Keyword(s):  
Isotactic Polypropylene ◽  
Mechanical Performance ◽  
Fibre Surface ◽  
Regenerated Cellulose ◽  
Nucleating Agents ◽  
Scanning Calorimetry ◽  
Mechanical Pulp ◽  
Polypropylene Composites ◽  
The Matrix ◽  
Final Composite

The mechanical performance of composites made from isotactic polypropylene reinforced with natural fibres depends on the interface between fibre and matrix, as well as matrix crystallinity. Sizing the fibre surface with nucleating agents to promote transcrystallinity is a potential route to improve the mechanical properties. The sizing of thermo-mechanical pulp and regenerated cellulose (Tencel™) fibres with α- and β-nucleating agents, to improve tensile strength and impact strength respectively, was assessed in this study. Polarised microscopy, electron microscopy and differential scanning calorimetry (DSC) showed that transcrystallinity was achieved and that the bulk crystallinity of the matrix was affected during processing (compounding and injection moulding). However, despite substantial changes in crystal structure in the final composite, the sizing method used did not lead to significant changes regarding the overall composite mechanical performance.

scholarly journals Nucleating agents based on graphene and graphene oxide for crystallization of the β-form of isotactic polypropylene

2019 ◽  
Vol 55 (4) ◽  
pp. 1436-1450 ◽  
Author(s):  
Jan Broda ◽  
Marcin Baczek ◽  
Janusz Fabia ◽  
Dorota Binias ◽  
Ryszard Fryczkowski
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Isotactic Polypropylene ◽  
Reduced Form ◽  
Pimelic Acid ◽  
Nucleating Agents ◽  
Scanning Calorimetry ◽  
Functionalized Graphene Oxide ◽  
Reduced Graphene ◽  
Carboxylic Groups

Abstract During the investigations, functionalization of graphene oxide synthesized using modified Hummers’ method and its reduced form was performed. Mixtures of graphene oxide and reduced graphene oxide with pimelic acid and calcium hydroxide were prepared for functionalization. During the reaction, the molecules of pimelic acid were attached to the surface of graphene sheets. By forming links between the carboxylic groups of pimelic acid and graphene oxide, the durable connection was achieved. The functionalized graphene oxide and the reduced graphene oxide were used as additives in isotactic polypropylene crystallization. The influence of additives on crystallisation in non-isothermal conditions was examined using polarized optical microscopy and differential scanning calorimetry. The effect of the additives on the polypropylene structure was analysed using wide-angle X-ray scattering. For both functionalized compounds, the nucleating ability towards β-form of polypropylene was detected. Both additives showed the increase in the nucleation rate and promotion of growth of the β-form crystals. Nucleation efficiency similar to other nucleating agents used in the crystallization of the β-form of polypropylene was revealed.

Interfaces in Fibre Reinforced Cements

1987 ◽  
Vol 114 ◽  
Author(s):  
A. Bentur
Keyword(s):  
Mechanical Performance ◽  
Fibre Surface ◽  
Special Structure ◽  
Analytical Models ◽  
The Matrix

ABSTRACTThe microstructure of the matrix in the vicinity of the fibre surface is quite different from the microstructure of the bulk paste matrix. This can have an important effect on the processes that take place at the interface, such as crack-fibre interaction and debonding. The present paper describes the special structure of this zone, in monofilament and bundled fibre reinforced cements, and discusses its effects on some characteristics of the mechanical performance of the composites, which cannot be predicted by analytical models assuming a uniform matrix up to the fibre surface. The modification of the microstructure at the interface as a means for improving properties in some composites is described.

scholarly journals Biocomposites from Rice Straw Nanofibers: Morphology, Thermal and Mechanical Properties

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2138 ◽  
Author(s):  
José Carlos Alcántara ◽  
Israel González ◽  
M. Mercè Pareta ◽  
Fabiola Vilaseca
Keyword(s):  
Rice Straw ◽  
Mechanical Performance ◽  
Cellulose Nanofibers ◽  
Nucleating Agent ◽  
Mechanical Analysis ◽  
Nanocomposite Films ◽  
Chemical Extraction ◽  
Poly Vinyl Alcohol ◽  
Scanning Calorimetry ◽  
The Matrix

Agricultural residues are major potential resources for biomass and for material production. In this work, rice straw residues were used to isolate cellulose nanofibers of different degree of oxidation. Firstly, bleached rice fibers were produced from the rice straw residues following chemical extraction and bleaching processes. Oxidation of rice fibers mediated by radical 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) at pH 10 was then applied to extract rice cellulose nanofibers, with diameters of 3–11 nm from morphological analysis. The strengthening capacity of rice nanofibers was tested by casting nanocomposite films with poly(vinyl alcohol) polymer. The same formulations with eucalyptus nanofibers were produced as comparison. Their thermal and mechanical performance was evaluated using thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. The glass transition of nanocomposites was shifted to higher temperatures with respect to the pure polymer by the addition of rice cellulose nanofibers. Rice nanofibers also acted as a nucleating agent for the polymer matrix. More flexible eucalyptus nanofibers did not show these two phenomena on the matrix. Instead, both types of nanofibers gave similar stiffening (as Young’s modulus) to the matrix reinforced up to 5 wt.%. The ultimate tensile strength of nanocomposite films revealed significant enhancing capacity for rice nanofibers, although this effect was somehow higher for eucalyptus nanofibers.

scholarly journals Structure and Mechanical Properties of Multi-Walled Carbon Nanotubes-Filled Isotactic Polypropylene Composites Treated by Pressurization at Different Rates

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1294 ◽  
Author(s):  
Xiaoting Li ◽  
Wenxia Jia ◽  
Beibei Dong ◽  
Huan Yuan ◽  
Fengmei Su ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Isotactic Polypropylene ◽  
Mechanical Tests ◽  
High Yield ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Polypropylene Composites ◽  
Pressurization Rate ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Isotactic polypropylene filled with 1 wt.% multi-walled carbon nanotubes (iPP/MWCNTs) were prepared, and their crystallization behavior induced by pressurizing to 2.0 GPa with adjustable rates from 2.5 to 1.3 × 104 MPa/s was studied. The obtained samples were characterized by combining wide angle X-ray diffraction, small angle X-ray scattering, differential scanning calorimetry, transmission electron microscopy and atomic force microscopy techniques. It was found that pressurization is a simple way to prepare iPP/MWCNTs composites in mesophase, γ-phase, or their blends. Two threshold pressurization rates marked as R1 and R2 were identified, while R1 corresponds to the onset of mesomorphic iPP formation. When the pressurization rate is lower than R1 only γ-phase generates, with its increasing mesophase begins to generate and coexist with γ-phase, and if it exceeds R2 only mesophase can generate. When iPP/MWCNTs crystallized in γ-phase, compared with the neat iPP, the existence of MWCNTs can promote the nucleation of γ-phase, leading to the formation of γ-crystal with thicker lamellae. If iPP/MWCNTs solidified in mesophase, MWCNTs can decrease the growth rate of the nodular structure, leading to the formation of mesophase with smaller nodular domains (about 9.4 nm). Mechanical tests reveal that, γ-iPP/MWCNTs composites prepared by slow pressurization display high Young’s modulus, high yield strength and high elongation at break, and meso-iPP/MWCNTs samples have excellent deformability because of the existence of nodular morphology. In this sense, the pressurization method is proved to be an efficient approach to regulate the crystalline structure and the properties of iPP/MWCNTs composites.

scholarly journals Maleated polypropylene as coupling agent for polypropylene composites reinforced with Eucalyptus and Pinus particles

BioResources ◽  
2019 ◽  
Vol 14 (2) ◽  
pp. 4774-4791
Keyword(s):  
Degree Of Crystallinity ◽  
Esterification Reaction ◽  
Scanning Electron Micrographs ◽  
Scanning Calorimetry ◽  
Polypropylene Composites ◽  
Maleated Polypropylene ◽  
The Matrix ◽  
Twin Screw ◽  
Coniferous Wood ◽  
Scanning Electron

Waste from the processing of hardwood and coniferous wood generated in the timber industries is difficult to dispose of and can cause considerable environmental impacts, such as soil and groundwater contamination. In this context, composites with varying concentrations of polypropylene, maleated polypropylene, and particulate Eucalyptus and Pinus waste were produced in a twin screw extruder and injection molded as test bodies for tensile and flexural tests. The morphology of the composites was investigated via scanning electron microscopy. The thermal properties were identified through differential scanning calorimetry. The tensile and flexural results for the two waste formulations indicated that the addition of vegetable fillers increased the modulus of elasticity and bending, and the compatibilizer provided increased resistance to stress and maximum deflection. The scanning electron micrographs illustrated the wetting of the cellulosic charge by the thermoplastic polymer with the compatibilizer, which corroborated the possible occurrence of an esterification reaction and hydrogen bonding interactions in the matrix-particle interface. The incorporation of waste in the composite resulted in the reduction of the degree of crystallinity of polypropylene, regardless of the use of the compatibilizer. This was explained by the barrier capacity of the charge, which prevented the growth of the crystals.

scholarly journals Crystallization Behavior and Properties of Glass Fiber Reinforced Polypropylene Composites

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1198 ◽  
Author(s):  
Yuming Wang ◽  
Lihong Cheng ◽  
Xiaoqian Cui ◽  
Weihong Guo
Keyword(s):  
Glass Fiber ◽  
Flexural Modulus ◽  
Nucleating Agent ◽  
Fiber Reinforced ◽  
Scanning Calorimetry ◽  
Polypropylene Composites ◽  
Crystallization Ability ◽  
Glass Fiber Reinforced ◽  
The Matrix ◽  
Different Content

Glass fiber with different content and different kinds of compatibilizers were used to prepare glass fiber-reinforced polypropylene (GFRP) composites. β-nucleating agent with different content was used to prepare β-polypropylene (PP), after which the toughness, crystallization ability and heat resistance were all enhanced. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) showed that the crystallite degree and crystallization ability were all greatly improved and β-PP was in dominant position. At last, both β-nucleating agent and glass fiber were used to modify the PP composites (β-GFRP). The formation of β-form PP made the matrix softer, which was beneficial for energy absorption and enhancement of toughness. The tensile strength, flexural strength and flexural modulus were improved dramatically, which were attributed to the coeffect of framework structure of GF and β-form PP.

In Situ Crosslinking Induced Structure Development and Mechanical Properties of Nano-Silica/Polypropylene Composites

2007 ◽  
Vol 334-335 ◽  
pp. 733-736 ◽  
Author(s):  
Tong Hui Zhou ◽  
Wen Hong Ruan ◽  
Min Zhi Rong ◽  
Ming Qiu Zhang
Keyword(s):  
Mechanical Performance ◽  
Filler Loading ◽  
Interfacial Interaction ◽  
Polymer Chains ◽  
Crosslinking Reaction ◽  
Nano Silica ◽  
Polypropylene Composites ◽  
The Matrix ◽  
In Situ Crosslinking

In our previous works, a double percolation mechanism of stress volumes was proposed to explain the special effects generated by small amounts of grafted nanoparticles. Accordingly, it is inferred that strengthening nanoparticle agglomerates and enhancing nanoparticles/polymer matrix interfacial interaction are the key issues to improve mechanical performance of the matrix polymer. To confirm this idea, in-situ crosslinking was adopted to prepare nanocomposites by adding reactive monomers and crosslinking agents during melt compounding of nano-silica with polypropylene (PP). It was found that the grafted polymer chains were successfully crosslinked and chemically bonded to the nano-silica forming crosslinked networks. Meanwhile, matrix molecular chains penetrated through the networks to establish the so-called semi-IPN structure that interconnected nanoparticles by the networks and improved filler/matrix interfacial interaction. As a result, the tiny nanoparticles were well distributed in the matrix and the toughening and reinforcing effects of the nanoparticles on the matrix were brought into play at rather low filler loading, as evidenced by mechanical performance tests. Besides, β-crystal was detected in the nanocomposites experienced in-situ crosslinking reaction.

scholarly journals Mechanical and Functional Properties of Novel Biobased Poly(decylene-2,5-furanoate)/Carbon Nanotubes Nanocomposite Films

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2459
Author(s):  
Giulia Fredi ◽  
Andrea Dorigato ◽  
Mauro Bortolotti ◽  
Alessandro Pegoretti ◽  
Dimitrios N. Bikiaris
Keyword(s):  
Carbon Nanotubes ◽  
Mechanical Performance ◽  
Rietveld Analysis ◽  
Nanocomposite Films ◽  
Scanning Calorimetry ◽  
Homogeneous Microstructure ◽  
Microstructural Investigation ◽  
Crystallinity Degree ◽  
The Matrix ◽  
Multi Walled Carbon Nanotubes

The present work investigates the microstructural, thermo-mechanical, and electrical properties of a promising, but still not thoroughly studied, biobased polymer, i.e., poly(decylene furanoate) (PDeF), and its performance when multi-walled carbon nanotubes (CNTs) are added. After sample preparation by solution mixing and film casting, the microstructural investigation evidences that the fracture surface becomes smoother and more homogeneous with a small fraction of CNTs, and that the production process is suitable to achieve good disentanglement and dispersion of CNTs within the matrix, although some aggregates are still observable. CNTs act as nucleating agents for PDeF crystals, as evidenced by differential scanning calorimetry, as the crystallinity degree increases from 43.2% of neat PDeF to 55.0% with a CNT content of 2 phr, while the crystallization temperature increases from 68.4 °C of PDeF to 91.7 °C of PDeF-CNT-2. A similar trend in crystallinity is confirmed by X-ray diffraction, after detailed Rietveld analysis with a three-phase model. CNTs also remarkably improve the mechanical performance of the bioderived polymer, as the elastic modulus increases up to 123% and the stress at break up to 131%. The strain at break also increases by +71% when a small amount of 0.25 phr of CNTs are added, which is probably the consequence of a more homogeneous microstructure. The long-term mechanical performance is also improved upon CNT addition, as the creep compliance decreases considerably, which was observed for both the elastic and the viscoelastic component. Finally, the films become electrically dissipative for a CNT content of 1 phr and conductive for a CNT amount of 2 phr. This study contributes to highlight the properties of bioderived furan-based polymer PDeF and evidences the potential of CNTs as a promising nanofiller for this matrix.

scholarly journals Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1124
Author(s):  
Zhifang Liang ◽  
Hongwu Wu ◽  
Ruipu Liu ◽  
Caiquan Wu
Keyword(s):  
Mechanical Properties ◽  
Polylactic Acid ◽  
Mechanical Performance ◽  
Tensile Elongation ◽  
Sisal Fiber ◽  
Fiber Reinforced ◽  
Impact Performance ◽  
The Matrix ◽  
Blending Process ◽  
Extension Direction

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

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