Nguyen Vu Giang

Effect of TiO2-Crystal Forms on the Photo-Degradation of EVA/PLA Blend Under Accelerated Weather Testing

Photo-degradation of poly (ethylene-co-vinyl acetate) (EVA)/poly (lactic acid) (PLA) blend and EVA/PLA/TiO2 nanocomposites was carried out under accelerated weather testing conditions by alternating cycles of ultraviolet (UV) light and moisture at controlled and elevated temperatures. The characters, properties, and morphology of these materials before and after accelerated weather testing were determined by Fourier transform infrared spectroscopy, colour changes, viscosity, tensile test, thermogravimetric analysis, and field emission scanning electron microscopy. The increases in the content of oxygen-containing groups, colour changes; the decreases in viscosity, tensile properties, and thermal stability of these materials after accelerated weather testing are the evidence for the photo-degradation of the blend and nanocomposites. After accelerated weather testing, the appearance of many micro-holes and micro-pores on the surface of the collected samples was observed. The photo-degradation degree of the nanocomposites depended on the TiO2-crystal form. Rutile TiO2 do not enhance the degradation, but anatase and mixed crystals TiO2 nanoparticles promoted the degradation of the nanocomposites. Particularly, the mixed crystals TiO2 nanoparticles showed the highest photo-catalytic activity of the nanocomposites.

Tensile, rheological properties, thermal stability, and morphology of ethylene vinyl acetate copolymer/silica nanocomposites using EVA-g-maleic anhydride

In this article, we present a study on the properties of ethylene vinyl acetate copolymer/silica nanocomposites prepared in absence and presence of EVA-g-maleic anhydride as a compatibilizer between silica nanoparticles and ethylene vinyl acetate matrix. A series of ethylene vinyl acetate/silica nanocomposites with different contents of silica nanoparticles were prepared by solution method. EVA-g-maleic anhydride with 0.5 wt% maleic anhydride groups was added to all ethylene vinyl acetate/silica nanocomposites. Fourier transform infrared, field emission scanning electron microscopy, rheology behavior, and thermogravimetry analysis were used to characterize the structure, morphology, rheological, and thermal properties of the nanocomposites, respectively. The Fourier transform infrared spectra and field emission scanning electron microscopy micrographs showed that the hydroxyl groups on the surface of silica nanoparticles interact with maleic anhydride groups in EVA-g-maleic anhydride and lead to a finer dispersion of individual silica nanoparticles in the ethylene vinyl acetate matrix. The rheological properties and thermal stability of ethylene vinyl acetate/silica nanocomposites were significantly increased after adding EVA-g-maleic anhydride into the nanocomposites. Mechanical properties including tensile strength and elongation at break of the nanocomposites were mainly affected by the content of silica nanoparticles. For the tensile strength as well as elongation at break of the nanocomposites, a maximum value was observed at the content of 0.5 wt% of silica nanoparticles. The addition of EVA-g-maleic anhydride into ethylene vinyl acetate/silica nanocomposites resulted in a further improvement of mechanical properties of the nanocomposites.

Using Rutile TiO2 Nanoparticles Reinforcing High Density Polyethylene Resin

The TiO2 nanoparticles were used as a reinforcement to prepare nanocomposites with high density polyethylene (HDPE) by melt blending process. The original TiO2 (ORT) was modified by 3-glycidoxypropyltrimethoxysilane (GPMS) to improve the dispersion into HDPE matrix. The FT-IR spectroscopy and FESEM micrographs of modified TiO2 (GRT) demonstrated that GPMS successfully grafted with TiO2 nanoparticles. The tensile test of HDPE/ORT and HDPE/GRT nanocomposites with various contents of dispersive particles indicated that the tensile strength and Young’s modulus of HDPE/GRT nanocomposites are superior to the values of original HDPE and HDPE/ORT nanocomposites. At 1 wt.% of GRT, the mechanical properties of nanocomposites were optimal. In DSC and TGA analyses, with the presence of GRT in the nanocomposites, the thermal stability significantly increased in comparison with pure HDPE and HDPE/ORT nanocomposites. The better dispersion of GRT in polymer matrix as shown in FESEM images demonstrated the higher mechanical properties of HDPE/GRT nanocomposites to HDPE/ORT nanocomposites.

Physico-Mechanical Properties,Thermo-Oxidation Resistance, Specific Interaction, and Morphology of the Polymer Blend Based on Polyethylene and Poly(Methyl Methacrylate) with and without Polyethylene-g-maleic Anhydride

Abstract The effect of addition of linear low density polyethylene-g-maleic anhydride (LLDPE-g-MA) on the physico-mechanical properties, thermo-oxidation resistance, phase interaction, and morphology of polymer blends based on LLDPE and poly(methyl methacrylate) (PMMA) was studied. It was shown that the physico-mechanical properties of the mixing of LLDPE/PMMA blends was increased with the addition of compatibilizer LLDPE-g-MA content to the polymer blends. The shift phenomena of the characteristic absorption peak of C=O group in the polymer blends using LLDPE-g-MA affirm that the compatibilizer LLDPE-g-MA was able to interact with PMMA [on the Fourier Transformation Infrared Spectroscopy (FTIR) spectra]. The compatibilizer reduced the particle size of PMMA phase in LLDPE phase and increased the miscibility and compatibility between LLDPE and PMMA. The physico-mechanical properties of the polymer blends depended on the component polymer ratios and the content of LLDPE-g-MA. From experimental results, it was clear that the polymer blend material had good physico-mechanical properties and morphology at the ratio of LLDPE/PMMA 90/10 (wt./wt.) and 1.5 wt.% LLDPE-g-MA.

Sustainable composite materials based on ethylene-vinylacetate copolymer and organo-modified silica

Abstract Silica nanoparticles (SNPs) were modified by different amounts of 3-aminopropyltriethoxysilane (APTES). Nanocomposites based on ethylene vinyl acetate copolymer (EVA) and modified SNP (m-SNP) were prepared by the melt mixing method. They were characterized by Haake torque measurement, differential scanning calorimetry (DSC), horizontal burning test, scanning electron microscopy. Accelerated weather testing of the nanocomposites was performed according to ASTM D4329 (cycle A) for 168 h. The Haake torque indicates that the relative melt viscosity of EVA/m-SNPs is slightly higher than that of EVA/SNP nanocomposites. The DSC and burning test results show that m-SNPs decrease crystallinity degree and flammability of EVA. After accelerated weather testing, the relative amount of C=O groups in EVA/m-SNP nanocomposites is lower than that in EVA/SNP nanocomposites. Micro crack of EVA/m-SNP nanocomposite is smaller than that of EVA/SNP nanocomposite. In our study, the EVA/m-SNP nanocomposites with good tensile properties, flame and weather resistance can be used as sustainable materials in some technique fields.

SYNTHESIS OF EVAgMA AND ITS EFFECTS ON TENSILE PROPERTIES AND MORPHOLOGY OF ETHYLENE VINYL ACETATE COPOLYMER/BAMBOO FLOUR AND POLYPROPYLENE/ BAMBOO FLOUR COMPOSITES

Thermoplastic composites reinforced with natural fillers (WPCs) have being attracted many attentions in recent years. The biggest challenges for WPCs production have to face is the poor adhesion and interaction between the components in the composites. This study investigates the technique to overcome these challenges without the treatment and surface modification of natural additive fillers. The obtained experimental results showed that using maleic anhydride grafted ethylene vinyl acetate copolymer (EVAgMA) with 1.16 wt.% of MA could enhance the adhesion and interaction of bamboo flour (BF) with EVA and polypropylene (PP) matrices. These expressed through the improvement of tensile properties and mophological structure of EVA/BF composite and PP/BF composite with the presence of EVAgMA. Tensile strength of EVA/BF and PP/BF composites at the same 50 wt% of BF, increased 67 and 12%, respectively when EVAgMA was introduced.

Synthesis and characterization of (4-arm-star-PMMA)/PMMA-g-SiO2 hybrid nanocomposites

Abstract This study provides a route to prepare 4-arm star poly(methyl methacrylate) (4sPMMA)/PMMA grafted SiO2 (PMMA-g-SiO2) hybrid nanocomposites that can be used as 3D printing material and filler for dental materials. First, 4sPMMA was synthesized via atom transfer radical polymerization with low metal catalyst concentration. Modified colloidal silica nanoparticles (MCSPs) were synthesized by grafting 3-methoxypropyl trimethoxysilane (MPS) onto the surface of colloidal silica nanoparticles (CSPs) and then dispersed in the solution of methyl methacrylate monomer in dioxane. The mixture of 4sPMMA and MCSPs solutions was degassed and replaced in an oil bath at 70–75°C; the reaction was continued with α,α′-azobis(isobutyronitrile) as an initiator for 24 h to form 4sPMMA/PMMA-g-SiO2 hybrid nanocomposites. Viscosity measurement showed that viscosity of the hybrid was increased with increasing MPS loading used in modification of CSPs, which verified that PMMA had been grafted onto MCSPs. Fourier transform infrared spectra of the hybrid nanocomposites demonstrated the strong molecular interaction between MCSPs and polymer matrix, and 1H NMR spectra confirmed the formation of PMMA-g-SiO2. Field emission scanning electron microscopy and transmission electron microscopy images revealed that MCSPs were well dispersed in polymer matrix with the size of about 20–30 nm. Thermal stability of the hybrid nanocomposites was improved compared with PMMA made from free radical polymerization.

Study on characteristics, properties, and morphology of poly(lactic acid)/chitosan/hydroquinine green nanoparticles

Abstract Poly(lactic acid)/chitosan (PLA/CS) green nanoparticles containing hydroquinine (Hq) were prepared by emulsion method. The content of Hq was 10–50 wt% compared with the weight total of PLA and CS. The characteristics of these nanoparticles were analyzed by Fourier transform infrared (FTIR), differential scanning calorimetry, field emission scanning electron microscopy (FESEM), and particle size analysis. The wavenumbers of C=O, C=N, OH, and CH3 groups in FTIR spectra of the PLA/CS/Hq (PCHq) nanoparticles shifted in comparision with neat PLA, CS, and Hq that proved the interaction between these components. The FESEM images and particle size analysis results showed that the basic particle size of PCHq nanoparticles ranged between 100 and 200 nm. The Hq released from PLA/CS nanoparticles in pH 2 and pH 7.4 solutions was determined by ultraviolet-visible method. The obtained results indicated that the linear regression coefficient of calibration equation of Hq in the above solutions approximates 1. The Hq release from the PCHq nanoparticles includes fast release for the eight first testing hours, and then, controlled slow release. The Hq released process was obeyed according to the Korsmeyer-Peppas kinetic model.

Study on change of color and some properties of high density polyethylene/organo-modified calcium carbonate composites exposed naturally at Dong Hoi-Quang Binh

This paper presents the study on the UV-Vis spectra, change of color and some properties of high density polyethylene/organo-modified calcium carbonate (HDPE/m-CaCO 3 ) composites exposed naturally in Dong Hoi district, Quang Binh province (Vietnam). From June 2014 to June 2016, the samples of HDPE/m-CaCO 3 composites were tested naturally on outdoor shelves at Dong Hoi sea atmosphere region (at Dong Hoi, Quang Binh). The change of UV-VIS spectra, color and some properties of the HDPE/m-CaCO 3 composites depend on geographic, weather and climatic factors (solar radiation, temperature, humidity, etc.). In the UV-VIS spectra, the band at 265 nm showed the formation of the carbonyl groups such as ketone, lactone carbonyl and aliphatic ester which were occurred in photo-degradation process of HDPE/m-CaCO 3 composites. The results of color change indicated the surface of the samples of HDPE/m-CaCO 3 composites was lightened continuously with increasing natural exposure time and increased in total color difference value and significant loss in both redness and yellowness. Da*, Db* values and electrical breakdown of HDPE/m-CaCO 3 composites were decreased while their Dl*, DE, dielectric constant and dielectric loss were increased with rising natural exposure time. Dielectric constant of HDPE/m-CaCO 3 composites was in the range of 1.75 to 2.1 and dielectric loss of HDPE/m-CaCO 3 composites went up from 1.7 to 3.2 for 0 to 24 months. The electrical breakdown of HDPE/m-CaCO 3 composites reduced due to the decrease in the relative crystalline degree of the samples caused by the scission photo-degradation of HDPE macromolecules in HDPE/m-CaCO 3 composites for natural exposure time. Keywords. HDPE/CaCO 3 composites, photo-degradation, natural exposure, color change, electric properties, UV-Vis spectroscopy.

Tensile, electrical properties and morphology of polyethylene/modified fly ash composites using ultraflow

This paper presents relative melt viscosity, tensile, electrical properties and morphology of high density polyethylene (HDPE)/organo-modified fly ash (MFA) and HDPE/MFA/ultraflow (UTF) composites which were prepared by melt mixing method. Relative melt viscosity of HDPE was decreased with adding MFA and UTF into HDPE. Tensile properties (tensile strength, elongation at break and Young’s modulus) of HDPE/MFA/UTF composites were increased with rising UTF content to 5 wt.% and thereafter, they were dropped with the UTF content more than 5 wt.%. Electric properties (dielectric constant, dielectric loss and volume resistivity) of the HDPE/MFA and HDPE/MFA/UTF composites were investigated. The obtained parameters showed that the HDPE/MFA composites have electric insulation higher than HDPE/MFA/UTF composites. Morphology of the composite materials with and without using UTF was also studied by Field Emission Scanning Electron Microscopy (FESEM) images. The results indicated that the MFA was dispersed more regularly and less agglomerated in HDPE matrix with adding UTF into the HDPE/MFA composites.