Micro structure and Fractography of Multiwalled Carbon Nanotube Reinforced Unsaturated Polyester Nanocomposites

In this study unsaturated polyester resin (UPR) was reinforced with different concentration of predispersed multiwalled carbon nanotube (MWCNT). The rheology, structural analysis, fracture behavior, morphology, and thermal analysis of nanocomposites were carried out as a function of MWCNT content. Shear thinning behavior exhibited distinguishable dispersion quality of 0.3 wt% MWCNT in UPR matrix. Structural analysis reveals that MWCNT enhanced the nucleation of nanocomposites. The crystallinity of nanocomposites was increased by 71% after incorporation of 0.3 wt% MWCNT. Bending strength (BS) and bending modulus (BM) of nanocomposites were increased as well as 0.3 wt% MWCNT exhibited crack shielding in nanocomposites.The glass transition (Tg) and melting transition (Tm) of nanocomposites was increased by 68C and 108C respectively as compare to neat UPR. Additionally thermal stability of 0.3 wt% MWCNT incorporated nanocomposites was significantly improved as compare to UPR and nanocomposites which contained 0.1 and 0.5 wt% MWCN

PREPARATION AND CHARACTERIZATION OF LOW MOLECULAR WEIGHT CHITOSAN WITH DIFFERENT DEGREES OF DEACETYLATION BY THE ACID HYDROLYSIS METHOD

Objective: The objective of this research is to prepare Low Molecular Weight Chitosan (LMWC) by the acid hydrolysis method, using dilute hydrochloric acid (2M). LMWC has superior properties compared to the High Molecular Weight Chitosan (HMWC), especially in terms of water solubility, antibacterial and antifungal properties. These could open new potential applications for LMWC in sectors such as the cosmetics, food, and pharmaceutical industries. Methods: In this work, the acid hydrolysis method was used to produce LMWC with different molecular weights starting from 500 kDa and 93% degree of deacetylations (DDA). The molecular weights of the produced grades were determined by applying Mark-Houwink equation while the %DDA was determined and verified by the use of the 1st derivative UV method and 1HNMR method, respectively. The depolymerization reactions were carried out with different time intervals to produce totally deacetylated LMWC of 30 kDa, 15 kDa, and 7.5 kDa. The LMWC was characterized by FTIR, XRD, and DSC to evaluate the functionality, microstructure and thermal properties. Results: The FTIR spectra revealed that there is no significant difference in the main skeletal structure of the LMWC and HMWC. On the other hand, the XRD and DSC results showed that the LMWC of different molecular weights and degrees of deacetylation are of semi-crystalline structure, similar to the HMWC. Conclusion: The obtained results showed that the used acid hydrolysis procedure can produce LMWC grades of desired specifications, yields, and quality which are suitable for use in different applications

Characterization of microcrystalline cellulose isolated through mechanochemical method

Mechanochemical process, which involves simultaneous ultrasound and alkali treatment, has been used to isolatemicrocrystalline cellulose (MCC) from raw oil palm empty fruit bunch (REFB) fibre. Three steps have been used to preparethe MCC, namely removal of lignin, removal of hemicellulose and finally production of MCC. The crystallinity index inMCC is found to be 81% which is 54% higher than that of REFB and 45% higher than that of cellulose. Besidescrystallinity, the crystal size (28.03Å) of MCC is also enhanced noticeably by 53% as compared to the REFB and 28% ascompared to cellulose. The degradation temperature, and the residue content reveal the excellent thermal stability of MCCextracted through this mechanochemical technique

Preparation and characterization of low molecular weight chitosan with different degrees of deacetylation by the acid hydrolysis method

Objective: The objective of this research is to prepare Low Molecular Weight Chitosan (LMWC) by the acid hydrolysis method, using dilute hydrochloric acid (2M). LMWC has superior properties compared to the High Molecular Weight Chitosan (HMWC), especially in terms of water solubility, antibacterial and antifungal properties. These could open new potential applications for LMWC in sectors such as the cosmetics, food, and pharmaceutical industries. Methods: In this work, the acid hydrolysis method was used to produce LMWC with different molecular weights starting from 500 kDa and 93% degree of deacetylations (DDA). The molecular weights of the produced grades were determined by applying Mark-Houwink equation while the %DDA was determined and verified by the use of the 1st derivative UV method and1HNMR method, respectively. The depolymerization reactions were carried out with different time intervals to produce totally deacetylated LMWC of 30 kDa, 15 kDa, and 7.5 kDa. The LMWC was characterized by FTIR, XRD, and DSC to evaluate the functionality, microstructure and thermal properties. Results: The FTIR spectra revealed that there is no significant difference in the main skeletal structure of the LMWC and HMWC. On the other hand, the XRD and DSC results showed that the LMWC of different molecular weights and degrees of deacetylation are of semi-crystalline structure, similar to the HMWC. Conclusion: The obtained results showed that the used acid hydrolysis procedure can produce LMWC grades of desired specifications, yields, and quality which are suitable for use in different applications

Structures and Properties of Injection-Molded Biodegradable Poly(Lactic Acid) Nanocomposites Prepared with Untreated and Treated Multiwalled Carbon Nanotubes

Structural, mechanical, thermal, and electrical properties of low-loaded (0−1.5 wt%), untreated, and treated (with heat and nitric acid) multiwalled carbon nanotubes (MWCNTs)/poly (lactic acid) (PLA) nanocomposites have been studied. Among all synthesized composites, acid-treated 1.0 wt% MWCNTs reinforced PLA shows superior tensile strength and modulus to those shown by other samples. All nanocomposites including the pure PLA exhibit the orthorhombic β-form crystalline structure with low degree of crystallization, as demonstrated by X-ray diffraction study. Differential scanning calorimetry (DSC) of injection molded samples, respectively, reveals an enhancement of PLA crystallinity by 8% and 14% for untreated and treated nanotubes, relating to the observed improvement in mechanical properties. Nanocomposites show double melting behavior when crystallized nonisothermally by DSC, whilst the pure PLA shows single melting character. Thermogravimetric analysis discloses that the MWCNTs-loaded sample degraded faster than PLA. Surface resistivity of the nanocomposites is found to be dropped drastically by a factor of 1013 with a low loading of MWCNTs (1.5 wt%). A detailed discussion and correlation of the observed structures and properties are presented in this study. POLYM. ENG. SCI., 54:317–326, 2014. © 2013 Society of Plastics Engineer

Tailoring the dispersibility of non-covalent functionalized multi-walled carbon nanotube (MWCNT) nanosuspension using shellac (SL) bio-resin: Structure-property relationship and cytotoxicity of shellac coated carbon nanotubes (SLCNTs)

This study first reports the use of natural thermoplastic bio-resin shellac (SL) to functionalize multi-walled carbon nanotubes (MWCNTs). The MWCNTs were coated with 5, 10, and 15 wt% SL solutions to fabricate SLCNT nanocomposites which are highly dispersible and stable in solution. Enhanced surface charge imparted long-term stabilization of SLCNT nanosuspension. Microscopic analysis revealed distinct dispersion of nanotubes and a thin layer of SL on the surface of nanotubes in the nanocomposite system. FTIR and Raman spectroscopy confirmed well interaction between SL and MWCNT in the nanocomposites. It was disclosed by the microstructure analysis that the SL concentration affects the lattice parameters of SLCNT nanocomposites. The thermal stability of SLCNT was impressive compared to MWCNT. According to the ROS (reactive oxygen species) generation profile and cell viability study, SLCNTs have reduced adverse effects on cells. Therefore, the results confirm that shellac can significantly improve the stability of MWCNT and reduce the cytotoxicity to facilitate their widespread applications

Modification of structure and properties of well-dispersed dendrimer coated multi-walled carbon nanotube reinforced polyester nanocomposites

This work reveals the structure and properties of dendrimer coated multiwall carbon nanotube (DMWCNT) reinforced unsaturated polyester resin (UPR) nanocomposite. Rheology, as well as the shear thinning behavior of nanosuspension exhibits the dispersion of DMWCNT in UPR matrix. The Raman spectra of DMWCNT-UPR nanocomposites along with the Fourier-transform infrared (FTIR) spectra of DMWCNT and DMWCNT-UPR nanocomposites indicate the interaction between DMWCNT and UPR in the nanocomposite system. Additionally, the surface morphology of DMWCNT and DMWCNT-UPR nanocomposites reveals well dispersion of DMWCNT in DMWCNT-UPR nanocomposites. X-ray diffraction (XRD) profile demonstrates structural properties of pristine UPR and nanocomposites. The Transmission Electron micrograph and Field Emission Scanning Electron micrograph show the fractured surface morphologies of DMWCNT-UPR nanocomposites. Comparative stress-strain behavior shows the deformation mechanism of DMWCNT-UPR nanocomposites

Fabrication and characterization of modified multi walled carbon nanotube reinforced unsaturated polyester nanocomposites

This research presents a non-destructive modification of multi-walled carbon nanotube (MWCNT) and fabrication of MWCNT reinforced unsaturated polyester resin (UPR) nanocomposite. In this work, pre-dispersion of MWCNTs was performed in the tetra hydro furan (THF) solvent. In addition, pre-dispersion and post- dispersion time was optimized as 1.5 hour and 2 hour, respectively. The pre-dispersed MWCNT reinforced UPR (THF-MWCNT-UPR) nanocomposite exhibited better properties as compared to directly dispersed MWCNT reinforced UPR (MWCNT-UPR) nanocomposite. The optimum amount of MWCNT was evaluated through mechanical properties of nanocomposites contained 0.05 to 0.5 wt% MWCNT. The experimental tensile modulus (TM) of 0.3 wt% MWCNT reinforced 0.3CNT-UPR nanocomposite linearly fitted with Halpin –Tsai equation. Therefore, 0.3 wt% MWCNT was suggested as the optimum quantity. The nondefect modification of MWCNT was carried out with hyper branched polyester (HBP) and shellac (SL) functional polymers. The structural and thermal properties of 10 wt% HBP and SL coated HBCNT and SLCNT was noticeably improved as compared to pristine MWCNT. Moreover, 10 wt% HBP and SL coated HBCNT and SLCNT nanotubes remarkably reduced the curing temperature of nanosuspensions. Therefore, 10 wt% was considered as the optimum amount of HBP and SL to modify MWCNT. Optimum HBP coated MWCNT incorporated (OHBPCNT-UPR) nanocomposite became stiff. Conversely, optimum SL coated MWCNT incorporated (OSLCNT-UPR) nanocomposite became tough as compared to MWCNT reinforced nanocomposite. Different ratios of HBCNT and hydroxyl (OH) functionalized MWCNT (OHCNT) were incorporated in UPR to fabricate hybrid (HBOHCNT-UPR) nanocomposites. The ratio of HBCNT and OHCNT was optimized as 2:1 through the curing behavior of hybrid nanosuspensions. The comparative study was carried out among non-covalent and covalent functionalized as well as hybrid MWCNT reinforced UPR nanocomposites. Hybrid MWCNT incorporated nanosuspension exhibited the lowest curing temperature as compared to non-covalent and covalent functionalized MWCNT incorporated nanosuspensions. The hybrid nanocomposite exhibited the highest stiffness among nanocomposites which was individually fabricated with HBCNT and OHCNT. The mixture of non-covalent functionalized and covalent functionalized MWCNT jointly reinforced the properties of UPR

Influence of Carbon Nano Tubes on the Thermo-Mechanical Properties of Unsaturated Polyester Nanocomposite

To date nano fillers are renowned reinforcing agent for polymer materials. In this work, unsaturated polyester (UPR) nanocomposites were fabricated by 0.1, 0.3 and 0.5 wt% multi walled carbon nanotubes (MWCNTs) through solution dispersion and casting method. The influence of MWCNT content was investigated by thermo-mechanical properties. Dispersion of nanotubes was observed by fracture morphology. The strength of nanocomposites rose with raising the CNT content. Moreover, DSC thermograms of nanocomposites represent noticeable improvement of glass transition temperature (Tg), melting temperature (Tm) and enthalpy (ΔHm). Micro-crystallinity of nanocomposites increased with increasing the CNT content. Moreover, the stiffness increased with increasing the CNT content

Toughening Effect of Liquid Natural Rubber on The Morphology and Thermo-Mechanical Properties of the Poly(Lactic Acid) Ternary Blend

In this work, poly(lactic acid) (PLA) was melt blended with liquid natural rubber (LNR) and linear low-density polyethylene (LLDPE) to fabricate a PLA–LNR–LLDPE ternary blend. The torque rheology demonstrates the melt mixing behavior of PLA–LLDPE binary and PLA–LNR–LLDPE ternary blends. Mechanical properties of ternary blend illustrate the highest toughness as compared to neat PLA and PLA–LLDPE binary blend. Fracture morphology reveals the plastic deformation behavior in the ternary blend which is illustrated in TEM micrograph. The cold crystallization temperature of the ternary blend appears at a lower temperature as compared to the binary blend. The thermal stability of PLA is improved due to blending with LLDPE and LNR. The ternary blend exhibits greater storage modulus in the glassy state as well as in the rubbery state as compared to neat PLA and binary blend. Finally, LNR performed as an effective compatibilizer between PLA and LLDPE