Impact of nanoclay on physicomechanical and thermal analysis of polyvinyl alcohol/fumed silica/clay nanocomposites

Polyvinyl alcohol (PVA)/fumed silica/clay nanocomposites are prepared via solution intercalation by exploiting phase separation based on the bridging of particles by polymer chains. PVA/fumed silica/clay nanocomposites are characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and thermogravimetric analysis. Mechanical properties are determined by universal testing machine. From FTIR results, it indicates that IR spectrum for PVA/fumed silica/clay nanocomposites, especially PVA/fumed silica/clay (1.30E) nanocomposites, is much broader than pure PVA and other clay nanocomposites. The better interfacial bonding between PVA/fumed silica/clay (1.30E) nanocomposites are reflected in the improvement of the mechanical properties as well as thermal stability. The surface area analysis result proves that the PVA/fumed silica/clay (1.30E) nanocomposites have higher surface area and pore volume with less pore size. With the addition of 1.30E clay to the composite system, the tensile strength and modulus had shown the highest values as well as higher activation energy for thermal decomposition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41843.     

Starch crosslinked with poly(vinyl alcohol) by boric acid

Starch was crosslinked with poly(vinyl alcohol) (PVA) by boric acid. A suitable plasticizer and defoamer were added to obtain the brei. A film from the starch and PVA (SP film) was prepared by casting. The effects of various factors, such as the crosslinking temperature, the PVA content, and the amounts of glycerol and boric acid, on the tensile strength and breaking elongation were studied. The results showed that the SP film prepared by boric acid crosslinking had excellent mechanical properties. The film‐forming properties, transmittance, and water resistance of the SP film were also investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1394–1397, 2005     

Synthesis of walnut-like polyaniline by using polyvinyl alcohol micellar template with excellent film transmission

Though there have been many reports on various morphologies of polyaniline (PANI), the research on fabricating new morphologies remains to be explored. In this work, with the help of polyvinyl alcohol (PVA) micelles as templates, walnut-like PANI having a rough periphery is successfully synthesized at room temperature by a static reaction. In addition, the effects of the amount of PVA, the concentration of HCl solution and the type of surfactant on the morphologies of PANI are studied in detail. Outcomes demonstrate that the fabrication of PANI walnuts is a result of the cooperation effect of the amount of PVA and the concentration of HCl solution. Moreover, PANI walnuts exhibit good thermal stability, which begins to degrade at up to about 300°C. Thin film coated by PANI walnuts possesses excellent transmittance. When PANI sample is prepared in the presence of 0.50 g PVA and 0.010 M HCl solution, the film transmittance can reach a maximum of 74% at 1200 nm. The sample presented herein have potential to be used in optical devices.     

Gallic acid crosslinked peanut protein-corn starch composite edible films produced at alkaline pH with ultrasound application

Corn starch and peanut protein blend films were prepared with and without gallic acid addition (0.25%, w/v) at pH 7, 9, and 11 by casting. The ultrasound (160 W, 20 kHz, 10 min) treatment was applied to the film-forming solutions. This study aimed to develop biopolymer-based films with gallic acid and to determine the interactions of components at different pHs and with ultrasound. The barrier, optical, mechanical, and thermal properties of films were examined. Moreover, structural characterization of films was conducted by Fourier transform infrared (FTIR), x-ray diffraction, and trinitro benzenesulfonic acid assay to enlighten the crosslinking interactions of gallic acid with biopolymers at different pHs. At neutral pH, gallic acid behaved as plasticizer. By acting as a crosslinker at pH 9, gallic acid provided the lowest moisture content, darker and more opaque appearance, enhanced barrier performance and thermal stability. The crosslinking degrees of gallic acid-enriched films were 49.1% (pH 7), 77% (pH 9), and 67.4% (pH 11). Additionally, gallic acid increased antioxidant capacity. The ultrasonication adversely affected the film properties by breaking bonds in the film structure. Peanut protein-corn starch-gallic acid films under mild alkaline conditions exhibited outstanding thermal stability, mechanical durability, light, and water barrier characteristics, making them appropriate for sustainable food packaging applications.     

Immobilization of bacteriocin nisin into a poly(vinyl alcohol) polymer matrix crosslinked with nontoxic dicarboxylic acid

This work is focused on novel methodology of poly(vinyl alcohol) crosslinking by non‐toxic dicarboxylic acid, glutaric acid. The cross‐linked system was used as a matrix for immobilization of bacteriocin nisin. Effect of the crosslinking degree on physico‐chemical, morphology, mechanical, and thermal properties of poly(vinyl alcohol) films were investigated by using swelling test, Fourier transform infrared spectroscopy, scanning electron microscopy, stress–strain analysis, differential scanning calorimetry, and thermogravimetry. Release profile of the nisin from the cross‐linked poly(vinyl alcohol) was studied by high performance liquid chromatography. Antibacterial activity of the prepared systems was tested by agar diffusion test and dilution and spread plate technique. Results showed suitability of glutaric acid as effective crosslinking agent of poly(vinyl alcohol) that acts synergistically with bacteriocin nisin against the tested Gram‐positive and Gram‐negative bacterial strains. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43674.     

CR composites with improved processing safety crosslinked via Heck's reaction

The aim of this study was to optimize the composition of the chloroprene rubber (CR) composites crosslinked via the Heck-type reaction to ensure their safe processing at elevated temperature. The developed curing system consisting of iron (III) acetylacetonate (Fe(acac)) and triethanolamine (TEOA) demonstrates high activity and more eco-friendly composition in comparison with metal oxide system, commercially used for CR crosslinking. However, the high activity of Fe(acac)/TEOA system results in a short scorch time, which is the greatest disadvantage regarding the safe processing of CR rubber and thus, must be improved. Therefore, CR compounds with Fe(acac) in the presence of different additives were studied. The longest scorch times (t₀₂) were observed for rubber compounds with urotropine (U), N-cyclohexyl-2-benzothiazole sulfenamide (CBS) or salicylic acid. Moreover, vulcanizates containing these additives exhibited higher tensile strengths and elongation at breaks compared to CR crosslinked with Fe(acac)/TEOA system.     

Thermal and surface characterization of plasticized starch polyvinyl alcohol blends crosslinked with epichlorohydrin

Starch‐polyvinyl alcohol (PVA) blends in 2:8 wt % were prepared with various plasticizers such as polyethylene glycol (PEG‐200, PEG‐400) and glycerol. The crosslinking of starch‐PVA blends by epichlorohydrin was carried out in the presence of a plasticizer in situ. The obtained films were analyzed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), dynamic mechanical and thermal analysis (DMTA), and X‐ray photoelectron spectroscopy (XPS), and remarkable changes in thermal stability and glass‐transition temperature have been observed on plasticizing and crosslinking in different concentrations. Different kinetic models such as Coats–Redfern, Broido, Friedman, and Chang were used to calculate the kinetic parameters of thermal decomposition. The results suggest that the thermal stability and activation energy of thermal decomposition passes through maxima at a critical concentration of plasticizer and increases with increasing crosslinker concentration. High‐resolution C 1s XPS analysis was used to provide a method of differentiating the presence of various carbons associated with different environment in the films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 25–34, 2006     

聚乙烯醇/淀粉/凤仙透骨草提取物复合膜制备及性能

以聚乙烯醇(Polyvinyl alcohol,PVA)、淀粉(Starch,ST)为原料,凤仙透骨草提取物(Impatiens balsamina extract,IBE)为抗菌剂,通过共混法制备抗菌复合膜,通过FTIR、XRD、SEM和热重分析对复合膜的形貌和结构进行表征及对力学、光学、阻隔、抑菌等性能测试分析。结果表明,IBE与PVA/ST基膜复合良好,制备的PVA/ST/IBE抗菌复合膜对大肠杆菌、白色葡萄球菌和枯草杆菌具有良好的抑菌作用,抑菌性能随着IBE含量的增加而逐渐提高；同时具有良好的力学强度,IBE添加量为12.5 mL的复合膜拉伸强度达到22.97±0.68 MPa,断裂伸长率相比PVA/ST基膜提升了79.22%；透明度有所下降,透光率下降了11.90%；氧气阻隔性能良好,氧气透过系数为1.771±0.196×10_-12 ^cm₃^.cm/(cm₂^.s.Pa),在环保包装、食品保鲜等领域具有广阔的应用前景。     

Cyclic and monotonic testing of free and constrained recovery properties of a chemically crosslinked acrylate

A chemically crosslinked acrylate network was submitted to various thermomechanical strain and stress recoveries whilechanging the experimental parameters in order to better define the benefits and the limits of using chemically crosslinked polymers for multicycle applications or applications under external constraints. The results showed that the free recoveries and the constrained recoveries remained the same at the first cycle and during the next ones. It was also shown that the low stress usually generated by a crosslinked network when submitted to a constrained recovery can be significantly increased by choosing suitable experimental conditions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39813.     

Effects of an itaconic acid comonomer on the structural evolution and thermal behaviors of polyacrylonitrile used for polyacrylonitrile‐based carbon fibers

The influence of an acid comonomer on the structural evolution and thermal behaviors of a polyacrylonitrile (PAN) terpolymer containing about 4.19 wt % methyl methacrylate and 0.98 wt % itaconic acid (IA) during a heating treatment were studied by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry (TG) and compared with the PAN homopolymer. From the results of FTIR spectroscopy and DSC, we found that the presence of the IA comonomer promoted cyclization reactions at a faster rate and broadened the exothermic peak; this eased the concentration of heat release. By comparing the results of the TG data, we found that the presence of the IA comonomer promoted dehydrogenation reactions and the formation of a large quantity of better ladder structures. In additional, the better ladder structures that formed were easier to convert from ladder structures into graphitelike structures. The activation energy of random scissions at about 300°C was calculated by the Kissinger method. The results show that the presence of the IA comonomer inhibited the random scission reactions to some extent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40834.     

Poly(vinylidene-co-hexafluoropropylene) membrane modified with glass fibers and polyvinyl pyrrolidone: Mechanical and electrochemical properties

The polymer electrolytes based on poly(vinylidene-co-hexafluoropropylene) (PVDF-co-HFP) have been widely studied and applied in devices for its excellent electrochemical and mechanical properties. Here, porous PVDF-co-HFP membrane modified with glass fibers (GFs) and polyvinyl pyrrolidone (PVP) were fabricated by phase-transfer method. When the dosage of GFs exceeded 1 wt%, the composite membranes exhibited 6.11 MPa tensile strength. When the dosage of GFs and PVP reached 1% (PVP₁GF₁), respectively, the composite membranes in porous network structure possessed the highest electrolyte uptake of 251.02%, the thermal stability of 343°C and the ionic conductivity of 3.05 × 10⁻³ S cm⁻¹. Electrochromic device (ECD) was assembled with PVP₁GF₁ electrolyte, showing quick responses between the bleached and the color states within 3 s. The PVDF-co-HFP composite electrolyte was expected to be effective substitutes for liquid electrolytes used in ECDs.     

Water states and thermal processability of boric acid modified poly(vinyl alcohol)

To further improve the processability of water plasticized poly(vinyl alcohol) (PVA), boric acid (BA), which can rapidly form reversible crosslinked structure with the hydroxyl groups of PVA, was adopted as a modifier, and the water states, thermal performance, and rheological properties of modified PVA were investigated. The results showed that ascribing to the formation of the crosslinked structure between PVA and BA, the content of nonfreezing water in system increased, indicating that the bondage of PVA matrix on water enhanced, thus retarding the tempestuous evaporation of water in system during melt process and making more water remained in system to play the role of plasticizer. Meanwhile, this crosslinked structure shielded part hydroxyl groups in PVA chains, leading to the further weakening of the self‐hydrogen bonding of PVA, and guaranteeing a lower melting point and higher decomposition temperature, thus obtaining a quite wide thermal processing window, i.e., ≥179°C. The melt viscosity of BA modified PVA slightly increased, but still satisfied the requirements for thermal processing, thus reinforcing the flow stability of the melt at high shearing rate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43246.     

Mechanical,acoustic, and thermal performances of shear thickening fluid–filled rigid polyurethane foam composites: Effects of content of shear thickening fluid and particle size of silica

Shear thickening fluid (STF) features a rheological property, and rigid polyurethane (PU) foams feature low thermal conductivity and excellent acoustic insulation. In this study, an STF/PU rigid foam composite sandwich structure was designed using different contents (0, 0.5, 1, or 1.5 wt %) of STF that contained 14 nm, 40 nm, or 75 nm silicon dioxide (SiO₂). The effects of STF content and silica size on the cell structure, mechanical performance, acoustic absorption, and thermal performance of the STF/PU foam were explored. The test results show that STF/PU foam exhibited three characteristic acoustic absorption peaks, and the maximum acoustic absorption coefficient reached 0.841. STF addition increased compression, bending strength, and maximum acoustic coefficient, as well as initial mass loss temperature. STF-filled PU foam composites containing 14 nm and 40 nm SiO₂ had a mild rise in thermal insulation. The rigid STF/PU foam composites with a cell structure had the maximum thermal conductivity of 0.22 W m⁻¹ K⁻¹ and sound absorption coefficient of 0.841, which confirm that they are a good candidate for sound-absorbing energy conservation materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47359.     

Preparation and properties of poly(lactic acid)/lignin-modified polyvinyl acetate composites

Poly(lactic acid)(PLA) has good application in the field of packaging because of its good biodegradability, tensile strength, and film-forming properties. However, the disadvantages of high brittleness and high cost limit the wider application of PLA. PLA/lignin-modified polyvinyl acetate (L-PVAc) composites with excellent toughness were prepared by melt blending PLA with modifier L-PVAc. The mechanical properties, thermal properties and morphology of the composites were characterized to evaluate the effect of L-PVAc content on the properties of the composites. The results showed that the introduction of L-PVAc could increase the impact strength, elongation at break, glass transition temperature, melting temperature and the degree of crystallinity of PLA/L-PVAc composites. When the L-PVAc content reached up to 20.0 wt%, the impact strength, elongation at break, glass transition temperature, melting temperature and the degree of crystallinity of the composites were increased by 298.2%, 167.5%, 3.8%, 1.8%, and 78.8%, respectively compared to pure PLA due to the good toughness of PVAc and heterogeneous nucleation of lignin. This research can promote the high-value utilization of lignin and the application of PLA in the fields of clothing, agriculture, medical and hygiene.     

Thermal,mechanical, and surface characterization of starch–poly(vinyl alcohol) blends and borax‐crosslinked films

Starch–poly(vinyl alcohol) (PVA) blends with different compositions were prepared and crosslinked with borax by in situ and posttreatment methods. Various amounts of glycerol and poly(ethylene glycol) with a molecular weight of 400 were added to the formulations as plasticizers. The pure starch–PVA blends and the crosslinked blends were subjected to differential scanning calorimetry, thermogravimetry, and X‐ray photoelectron spectroscopic studies. Broido and Coats–Redfern equations were used to calculate the thermal decomposition kinetic parameters. The tensile strengths and elongation percentages of the films were also evaluated. The results suggested that the glass‐transition temperature (T_g) and the melting temperature strongly depended on the plasticizer concentration. The enthalpy relaxation phenomenon was dependent on the starch content in the pure blend. The crosslinked films showed higher stability and lower T_g's than pure PVA and starch–PVA blends, respectively. High‐resolution X‐ray photoelectron spectroscopy provided a method of differentiating the presence of various carbons associated with different environments in the films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1313–1322, 2005     

3D printing of copper particles and poly(methyl methacrylate) beads containing poly(lactic acid) composites for enhancing thermomechanical properties

Poly(lactic acid) (PLA) composite filaments with different copper (Cu) contents as high as 40 and 20 wt% of poly(methyl methacrylate) (PMMA) beads have been fabricated by twin-screw extruder for 3D printing. A fused-deposition modeling (FDM) 3D printing technology has been used to print the PLA composites containing hybrid fillers of Cu particles and PMMA beads. The morphology, mechanical, and thermal properties of the printed PLA composites were investigated. The tensile strength was slightly decreased, but storage modulus and thermal conductivity of PLA composites were significantly improved by adding Cu particles in the presence of PMMA beads. The PLA composites with hybrid fillers of 40 wt% of Cu particles and 20 wt% of PMMA beads resulted in thermal conductivity of 0.49 W m⁻¹ K⁻¹ which was three times higher than that of the bare PLA resin. The facilitation of the segregated network of high-thermally conductive Cu particles with the PMMA beads in PLA matrix provided thermally conductive pathways and resulted in a remarkable enhancement in thermal conductivity.     

Photodegradation of low-density polyethylene with prooxidant and photocatalyst

Low-density polyethylene (LDPE) composite films with trisilver phosphate (Ag₃PO₄) and cadmium selenide (CdSe) particles as photocatalysts and manganese stearate as prooxidant were prepared. The film samples were irradiated under UV and visible light and their photodegradation were evaluated using Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The carbonyl index of the photocatalyst containing samples was very higher than the pure irradiated LDPE and even prooxidant containing film. The morphologies of the irradiated composite films were completely changed and had many cavities and cracks. The thermal stability of the composites was very lower than the pure polyethylene. However the crystallinity of the LDPE films with photocatalysts was enhanced contrarily the LDPE film with manganese stearate. Generally the results showed that the combination of the prooxidant with photocatalyst have synergistic effect on the photodegradation of the LDPE and can be used to accelerate the degradation of the polyethylene films.     

Physico-mechanical properties of poly (vinyl alcohol), poly (vinyl alcohol)/boric acid,and poly (vinyl alcohol) nanocomposites incorporated with amino-functionalized and pristine halloysite nanotubes films

Eco-friendly poly(vinyl alcohol) (PVA), PVA/boric acid, PVA/halloysite nanotubes (HNTs), and PVA/amino-functionalized HNTs (APTES-HNTs) films were fabricated by a solution casting technique. The samples were characterized by fourier transform infrared, X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and energy-dispersive spectroscopy. The characterization results proved the chemical and physical interactions between the PVA and different additives. The viscoelastic behavior of the films was evaluated by DMA and creep analysis. The storage modulus, loss factor, and both α_α and β_β transitions affected by APTES-HNTs as a potential filler to form effective cross-links. APTES-HNTs existence enhanced creep-recovery beyond expectations. Tensile and impact strength were measured to understand samples' mechanical stability. PVA/APTES-HNTs and PVA/boric acid showed more yield behavior after the elastic limit. Furthermore, the subsequent rupture and impact strength were increased significantly compared with neat PVA and PVA/HNTs. The viscoelastic and mechanical behaviors were linked to each other by the area under Tanδ curve and the work of rupture and impact strength, which their linear correlation coefficient is statistically significant at 95% confidence limits. It seems that the presence of APTES-HNTs provides new cross-links, which altered (improved) the physico-mechanical properties of PVA, offering a bionanocomposite suitable for further applications. From the literature, possible explanations are provided for these observations.     

Free-radical emulsion copolymerization of styrene with butadiene and vinyl triethoxysilane with a cumene hydroperoxide redox initiator

The emulsion free-radical copolymerization of vinyl triethoxysilane (VTES) with styrene (St) and butadiene (Bd) was initiated by cumene hydroperoxide and ferrous sulfate at 0 °C. The effects of VTES on the copolymerization conversion, reaction time, gel content, latex particle size, thermal stability, and mechanical properties were thoroughly investigated. The success of this reaction was confirmed by the peaks attributed to both Si─O─Si groups at 1065 cm⁻¹ and the Si─O─C bond at 1046 cm⁻¹. A kinetics analysis showed that the conversion decreased with increasing VTES mass in the monomer feed. Compared with that in the St–Bd copolymer, the latex particle size increased slightly with increasing VTES mass. The Mooney viscosity and gel content results show that a large fraction of precrosslinking molecular chains was formed in the rubber particles. The thermogravimetric analysis results indicate that the thermal stability of the copolymers increased with increasing VTES concentration. The 300% modulus and tensile strength of the St–Bd–VTES copolymer increased with the mass of VTES at first and then decreased after 3 phr VTES, whereas the elongation at break decreased with increasing VTES mass. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47896.     

Synergistic flame retardant effect of piperazine salt and ammonium polyphosphate as intumescent flame retardant system for polypropylene

Amino trimethylene phosphonic acid piperazine (ATPIP) salt, as a novel charring agent, is prepared via a simple ionic reaction in distilled water using amino trimethylene phosphate (ATMP) and piperazine as raw materials. The synergistic flame retardant effect of ATPIP and ammonium polyphosphate (APP) as an intumescent flame retardant (IFR) is investigated by various characterization and testing methods. The results show that the polypropylene (PP)/modified APP with piperazine (MAPP)/ATPIP ternary blend passes UL-94 V-0 rating and achieve a limiting oxygen index (LOI) of 30% at a loading level of 25 wt% IFR (MAPP:ATPIP = 3:1). Meanwhile, the total smoke production (TSP) value of IFR-PP samples is 3.3 m², which decreases by 93.2% compared with that of pure PP, exhibiting excellent smoke suppression performance. Besides, the analysis of gaseous pyrolysis products and char residue indicates that the IFR-PP samples show a synergistic flame-retardant mechanism including the gas phase and the condensed phase.