Microporous polypropylene sheets containing CaCO3 filler: Effects of stretching ratio and removing CaCO3 filler

Microporous polypropylene sheets are prepared by biaxially stretching polypropylene sheets containing CaCO₃ filler. Here, the stretching ratio is one of the most important factors in the preparative process, and removing the CaCO₃ filler also affects the sheet properties. Their effects were studied in relation to the properties and the structure of the microporous polypropylene sheets. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1543–1553, 1998     

Influence of the CaCO3 nanoparticles on the molecular orientation of the polypropylene matrix

The presence of aggregates of CaCO₃ nanoparticles in an isotactic polypropylene matrix processed by extrusion promotes the apparition of residual stresses. These stresses are removed with a thermal treatment of the composite, but a higher molecular orientation is then produced. The chain orientation inside the sample is nonhomogeneous due to the presence of the aggregates of nanoparticles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 947–952, 2003     

Influence of high power ultrasound on physical–chemical properties of polypropylene films aimed for food packaging: barrier and contact angle features

Investigation was focused on the impact of high power ultrasound (HPUS), also called thermosonication, on the oxygen permeation properties (permeability, solubility and diffusion coefficients) of barrier films aimed for food packaging. For this purpose, biaxially oriented polypropylene (BOPP) coated with acrylic/polyvinylidene chloride (BOPPAcPVDC) and biaxially oriented coextruded polypropylene (BOPPcoex) were used. The physical–chemical profile of the samples was determined using goniometry. There is a significant impact only of extreme HPUS conditions (the longest time and the highest amplitude) on the permeability, solubility and diffusion coefficients of oxygen through the BOPP films. The highest influence on the oxygen permeability in both investigated BOPP samples involved an HPUS with an amplitude of 100% during a 6 min treatment. However, BOPP samples showed different sensitivities at lower HPUS treatments. © 2017 Society of Chemical Industry     

Kinetic interpretation of influence of sodium chloride concentration and temperature on xanthan gum dispersion flow model

The present study derives a fixed‐concentration (0.4%) xanthan gum dispersion flow model for different molar concentrations of sodium chloride (0–0.25M) and different temperatures (20–70°C). The Ostwald–de Waele model is used in all cases. A temperature rise reduces the shear‐thinning characteristics of the systems, although the power law index is much less sensitive to changes in temperature when NaCl is added, even in very small amounts. The lowest consistency values correspond to the dispersions formulated in the absence of salt, the highest values are observed for molar values of ≥0.15, and there are decreases in consistency upon raising the temperature in all cases. The viscous behavior of the dispersions is interpreted using the Eyring equation. The activation energy and the free volume decrease when the shear rate is increased. The addition of NaCl, regardless of the molar concentration involved, provokes an important decrease of the activation energy. The free volume is independent of the molar concentration of NaCl for molar values >0.025. These results are related to the structure of the dispersions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 332–339, 2002     

Influence of nanovermiculites with a high aspect ratio and stretch orientation on the microstructure of polypropylene films

In this article, we present a process for preparing organovermiculites, which consist of expanded vermiculite (EVMT)–poly(vinyl alcohol) (PVOH) created by the mechanical ball‐milling of EVMT in a PVOH–water solution. We then discusses the influence of EVMT–PVOH on the barrier performance, crystallization behavior, thermal stability, and mechanical properties of modified blown polypropylene (PP) films. EVMT was intercalated and exfoliated by PVOH macromolecules to obtain a kind of hybrid EVMT–PVOH. PVOH served as both an intercalating agent into EVMT and a compatibilizer between EVMT and PP. Compared with the original (unmodified) PP, when the EVMT loading ranged from 0.1 to 2.0%, although the crystallinity decreased for most PP films, the thermal stability and mechanical properties all improved. Moreover, EVMT platelike particles with a high aspect ratio (ca. 550) dispersed in the PP matrix also improved the barrier properties of the modified PP films, which was in accordance with the Nielsen model. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42846.     

Study on the properties of nano‐TiO2 particles modified silk fibroin porous films

Using the freeze‐drying method, Nano‐TiO₂/silk fibroin porous films were synthesized with different ratios of TiO₂ to silk fibroin solution. Through scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), tensile strain, and water‐solubility tests, the structures and properties of these porous films were characterized. The SEM results indicated that the pores of the nano‐TiO₂/silk fibroin porous films were uniformly distributed by the freeze‐drying method. The XRD analysis indicated that the formation of nano‐TiO₂ particles might induce a conformational transition of silk fibroin from the typical Silk I to the typical Silk II structure partly with an increase in the crystallinity of the porous films. Compared with the pure silk fibroin porous films, the mechanical properties of nano‐TiO₂/silk fibroin porous films were improved, and its heat transition temperature was also enhanced; however, the water‐solubility of this material was diminished. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of extrusion,stretching and poling on the structural and piezoelectric properties of poly (vinylidene fluoride‐hexafluoropropylene) copolymer films

Three types of poly (vinylidene fluoride‐hexafluoropropylene) (PVDF–HFP) copolymer films were prepared by extrusion, stretching as well as simultaneously stretching and static electric field poling (SSSEP), respectively, and measured by the differential scanning calorimetric, wide angle X‐ray diffraction, fourier transformation infrared‐attenuated total reflection, and Dynamic mechanical analysis. The experimental results showed that the films prepared by stretching and SSSEP have higher crystallinity and β phase than by extrusion. SSSEP improved the chain orientation enormously both in crystalline and amorphous regions, resulting in the highest storage modulus. Because of the lower β phase content, the extruded films exhibited the lowest piezoelectric coefficient d₃₃. For the stretched and SSSEP films, although the β phase content was similar, the d₃₃ was distinct because of the different potential energy for the rotation of the dipoles. In addition, the SSSEP films gave the maximum d₃₃ (24 pC/N), higher than the other PVDF–HFP copolymer films that have been reported. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 858–862, 2007     

在盐酸法磷酸氢钙生产中应用硅酸钠和氯化钾脱氟剂的实验研究

使用贵州开阳磷矿粉盐酸法生产饲料级磷酸氢钙,实验研究利用硅酸钠和氯化钾脱氟剂脱氟的条件及效果,并与石灰乳脱氟工艺对比,每吨饲钙产品的单耗低于石灰乳脱氟工艺,磷矿粉和盐酸分别低100 kg和740kg,产品质量符合HG2636—2000要求。     

Influence of stearic acid treatment of filler particles on the structure and properties of ternary‐phase polypropylene composites

In this study, ternary‐phase polypropylene (PP) composites containing an ethylene–octene copolymer (EOR) and calcium carbonate (CaCO₃) were investigated. Particular consideration was given to the influence of stearic acid treatment of the filler on the phase morphology and mechanical properties of the composites. In composites containing an uncoated filler, a separate dispersion of the elastomer and filler particles in the PP matrix was observed. The use of filler treated with stearic acid had no effect either on the dispersion or the interaction of the filler and the polymer components. However, the surface‐treated filler was found to promote the β‐hexagonal crystallization of PP and gave a composite with lower T_{c onset} and T_c values. As a consequence, differences in mechanical properties, in particular, impact strength, were exhibited in which calcium carbonate with stearic acid treatment was apparently more effective in increasing the impact strength of the composites in comparison with the composites containing the uncoated filler. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3445–3454, 1999     

Influence of polymer swelling and dissolution into food simulants on the release of graphene nanoplates and carbon nanotubes from poly(lactic) acid and polypropylene composite films

The study compared the effects of swelling and dissolution of a matrix polymer by food simulants on the release of graphene nanoplates (GNPs) and multiwall carbon nanotubes (MWCNTs) from poly(lactic) acid (PLA) and polypropylene (PP) composite films. The total migration was determined gravimetrically in the ethanol and acetic acid food simulants at different time and temperature conditions, while migrants were detected by laser diffraction analysis and transmission electron microscopy. Swelling, thermal analysis, and scanning electron microscopy were applied to characterize the degradation of polymer films at the migration conditions. The release of nanoparticles was found in a high‐temperature migration test of 4 h at 90 °C. The hydrolytic dissolution of the PLA polymer in the food simulants caused a migration of GNPs (>100 nm) from the PLA/GNP/MWCNT films into the simulant solvents, while the entangled MWCNTs formed a network on the film surface, preventing their migration from the PLA composite films. In contrast, the PP polymer slightly swells in ethanol solvents, allowing some short carbon nanotubes to be released from the surface and cut edges of the PP/MWCNT film into food simulants. Mathematical modeling of diffusion was applied that accounts for type of polymer, time–temperature conditions, and solvent concentration; model parameters were validated with experimental results. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45469.     

Real‐time Raman spectroscopic measurement of crystallization kinetics and its effect on the morphology and properties of polyolefin blown films

The nonisothermal crystallization half‐time (t_0.5), defined as the time taken for a polymer film to reach half of its equilibrium crystallinity, was estimated from Raman spectroscopic measurements of crystallinity during blown film extrusion of a linear low‐density polyethylene (LLDPE) and an isotactic polypropylene (i‐PP). The crystalline a‐ and c‐axis orientation of LLDPE and i‐PP films, respectively, increased with decreasing crystallization half‐time. The transverse direction tensile modulus and tear strengths for LLDPE films also increased with decreasing half‐time. However, for i‐PP films, only the transverse direction tear strength increased with decreasing t_0.5, while the machine direction properties did not show a significant dependence on half‐time. Our real‐time Raman spectroscopy studies provide experimental evidence to theories proposed in the literature 1 - 3 with regards to the influence of the nonisothermal crystallization process (along the film axis) on the imparted final film structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1740–1747, 2005     

Synergistic inhibition effect of trisodium phosphate and sodium benzoate with sodium dodecyl benzene sulphonate on the corrosion of Mg-Al-Zn-Mn alloy in 30% ethylene glycol containing chloride ions

The enhanced efficiency of the sodium dodecyl benzene sulphonate (SDBS) by the addition of trisodium phosphate and sodium benzoate on the corrosion inhibition of Mg-Al-Zn-Mn alloy in aqueous ethylene glycol solution (30%) containing chloride ions was studied by potentiodynamic polarization technique and electrochemical impedance spectroscopy method. The combination of SDBS with trisodium phosphate and sodium benzoate resulted in synergistic effects on the inhibition efficiency. The inhibition efficiencies decreased with the increase in the medium temperature. The mixture of inhibitors acted predominantly as anodic types and the adsorption of the inhibitors on the surface of the alloy obeyed Langmuir adsorption isotherm.     

Gel formed during the solid‐state graft copolymerization of styrene and spherical polypropylene granules. I. Influence of reaction conditions on the gelation and its mechanism

Graft copolymers of polystyrene (PSt) with spherical polypropylene (PP) granules were synthesized by solid‐state reaction. In the copolymerization as a by‐product some gel was formed. The effects of the amount of free radical initiator, feed ratio of St monomer, species of free radical initiator, and composition of the spherical polyolefin granules on the grafting degree of PSt and the gelation were studied. It is found that larger amount of initiator used, and higher feed ratio of St monomer lead to a higher grafting degree and higher content of gel. During the cross‐link reaction process, both styrene and free‐radical participate in the reaction that discloses the reason of the increment of gel with the increment of styrene consumption or initiator consumption. Using PPR, which is a random copolymer of 95.1 mol % propylene units and 4.9 mol % ethylene units, as grafting matrix, higher grafting degree and higher content of gel can be reached than that using isotactic PP as grafting matrix. Using tert‐butyl peroxy benzoate (TBPB) as initiator, under the same conditions there were more PSt grafted to the spherical PP granules and more gel formed than that using benzoyl peroxide (BPO) as initiator. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3682–3687, 2007     

Influence of the support structure on the activity,stability, and metal leaching of a polymer‐supported organotin chloride catalyst

Polymer‐supported organotin chlorides have been synthesized by suspension copolymerization of organotin‐functionalized styrenic monomers using a precipitating porogen. Their activities as reducing catalysts have been evaluated in the reduction of bromoadamantane by sodium borohydride. The influence of the length of the spacer arm between the tin atom and the polymer backbone on the activity and the tin leaching of the supported catalyst have been studied. The nature of the alkyl groups (butyl or phenyl) attached on the tin atom plays an important role on the stability toward successive reuse of the supported catalyst. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1297–1308, 2001     

Influence of curing agent and compatibilizer on the physicomechanical properties of polypropylene/nitrile butadiene rubber blends investigated by positron annihilation lifetime technique

A series of thermoplastic vulcanizates of polypropylene (PP)/nitrile butadiene rubber (NBR) (50/50) have been prepared by melt‐mixing method, using phenolic resin/SnCl₂ as the curing system and maleic anhydride‐functionalized PP (PP‐g‐MA) and carboxylated NBR (NBRE‐RCOOH) as the compatibilizing system. Triethylenetetramine was also employed to promote the reaction between the functionalized polymers. The effects of curing agent and compatibilizer on the mechanical and morphological properties have been studied. A novel technique based on positron annihilation lifetime spectroscopy has been used to measure the free volume parameters of these systems. The positron results showed minimum free volume size and free volume fraction at 5.0% of the curing agent suggesting some crosslinking in the rubber phase. The reduction in free volume holes at 2.5% of the compatibilizer is interpreted as improvement in the interfacial adhesion between the components of the blend. The observed variation of free volume fraction is opposite to the tensile strength and exhibits the correlation that, lesser the free volume more is the tensile strength at 2.5% of the compatibilizer in the blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4672–4681, 2006     

Influence of thermal treatments,molecular weight,and molecular weight distribution on the crystallization of β‐isotactic polypropylene

Six samples of isotactic polypropylene were examined to study the influence of the thermal treatments and the molecular weights and their distribution on the β‐crystallization of the polymer. The highest amount of the β‐phase was obtained by isothermal crystallization and in correspondence of high average molecular weights and wide molecular weight distributions. Small‐angle X‐ray scattering pointed out that a partial β‐crystallization seems not to influence the lamellar morphology parameters. Differential scanning calorimetry measurements, at different heating rates, allowed us to confirm that the multiple melting endotherms behavior of the β‐phase is to be correlated to a melting–recrystallization–melting mechanism. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1008–1012, 2004