Diffusion of additives and deterioration with passage of time in polypropylene

The diffusion of additives and the deterioration with the passage of time in polypropylene (PP) were studied by using the UL flaming test and the oxygen index test to measure the flame retardancy. The weight change was also measured. The decreases with the lapse of time were observed for multiple flame retardants. Aliphatic brominated compounds showed the best result for flame retardancy in the initial stage of combustion. The best flame retardants for PP to inhibit the deterioration of flame retardancy with the passage of time were brominated hydrocarbon with more than two aromatic rings connected by a functional group or isocyanurate, and phosphates connected with a branching aliphatic hydrocarbon. The weight of the loss was plotted as a function of aging time and temperature to elucidate why the flame retardancy deteriorated. The apparent diffusion constant depends on the temperature and the rate was expressed with the Arrhenius equation. The concentration of flame retardant in PP was calculated by the constant and the equation at arbitrary time after thermal aging. The relation between the performance and chemical structure of the additives was also discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Studies on the diffusion characteristics of some aromatic solvents into polypropylene film

The sorption properties of the solvents benzene, toluene, and xylene into polypropylene films at 40, 60, and 80°C have been investigated. The diffusivity and permeability of the solvents into polypropylene films were found to increase in the order of solvent, benzene, toluene, and xylene at the different temperatures studied. The properties were also found to be temperature dependent. The zsolubility of the solvents into polypropylene films was found to be highest in toluene, followed by xylene, and least in benzene. However, a general increase in solubility with temperature was observed for all the solvents studied. The calculated values of activation energy of diffusion did not show any relationship with solvent properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1985–1989, 2006     

Interactions between sorbitol-type nucleator and additives for polypropylene

The thermal properties of a sorbitol-type nucleating agent (viz. 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol (TBPMN)) were examined in this study, and the influence of common processing additives assessed. In addition, we describe a novel approach to monitor in situ the self-assembly of the nucleator in presence of additives by optical microscopy. The performance of sorbitol compounds is closely associated to their chemical structure and ability to self-assemble. TBPMN formed elongated fibrils from the melt under inert atmosphere, in molted polypropylene, or in presence of antioxidants. However, calcium stearate (CaSt) and glycerol monostearate hampered growth, and yielded thinner fibrils. In presence of the additives, melting point depression of the nucleator occurred, and resulted in a lower degree of crystallinity upon cooling. Performance evaluation of the nucleator in polypropylene blends revealed an increased crystallization temperature when antioxidants were present, while CaSt inhibited nucleator activity. The effect of mono-glycerides was found highly dependent on the processing conditions. Noteworthy, blends containing all the additives displayed the highest performance. This study highlights the importance of the preparation method of polymer additive blends to achieving the best performance in the final product. Characterization was performed by thermogravimetric analysis, Fourier-transform infrared spectroscopy, optical microscopy, and differential scanning calorimetry.     

Preparation and properties of nano SiO2 core-shell structured additives and their nanocomposite with polypropylene

To improve the performance of traditional nucleation additives and their compatibility with other additives, as well as to solve complex problems in practical applications, SiO₂ precursors were reactively grafted in situ with the symmetrical hydroxyl groups of the nucleation agents. With this approach, the dissymmetrical part of the nucleation agents plays an important role. As a result, the prepared composite additive—the nanoparticle precursor (NPP0)—produces excellent results. The NPP0-PP composite has a transparency of over 93%, haze lower than 15%, and a heat distortion temperature (HDT) of 142°C, which is more than the 110°C of the pure PP matrix. In addition, it maintains over 90% of the mechanical properties with a deformation coefficient less than 1%. This indicates a strong nanoeffect. Translated from Polymeric Materials Science & Engineering, 2006, 22(1): 146–150 [译自: 高分子材料科学与工程]     

Effect of multistratification and film depth on the visualized dynamic sorption behavior of perylene in cellulose acetate films by a confocal laser scanning microscope technique

The sorption behavior of a fluorescent reagent into a polymer film was visualized by confocal laser scanning microscopy (CLSM), and the effects of the additives, film types, and film depth on the diffusion coefficient (D) of the fluorescence reagent were examined. Perylene and cellulose acetate (CA) were used as a fluorescent reagent and a polymer material, respectively. Perylene dissolved in the additives triethylene glycol diacetate (TEGDA) and glycerol triacetate (GTA) was added to the CA film. Then, the evaluation of two types of CA films, a closed‐system cellulose acetate (CCA) sample and an open‐system cellulose acetate (OCA) sample, was conducted. At optimized CLSM conditions (with a scanning range at a 20‐μm depth from the CA film surface with 1‐μm intervals and a scanning speed of 1 fps), the sorption of perylene at the inner CA film was determined. The D values of perylene in the CA film were calculated pursuant to Fick's second law. Higher D values of perylene mixed with TEGDA versus those of perylene mixed with GTA were commonly obtained for the CCA sample (TEGDA: 8.9 × 10⁻¹⁵ m²/s > GTA: 1.7 × 10⁻¹⁵ m²/s) and the OCA sample (TEGDA: 11 × 10⁻¹⁵ m²/s > GTA: 3.3 × 10⁻¹⁵ m²/s) because of the higher chemical affinity of TEGDA with perylene than that of GTA. Perylene indicated a higher D value and was homogeneously distributed in the case of the OCA sample; we found that diffusivity and distribution of perylene in CA film were largely affected by the multistratification treatment. We also proved that the deeper the film depth was, the lower the diffusivity of perylene was, regardless of the types of additives and films. The factors considered for the film‐depth dependence of D were a gradual increase in the diffusion pathway for perylene caused by additive diffusion and the concentration dependence of the perylene D. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Study of crater structure formation on the surface of biaxially oriented polypropylene film

Biaxially oriented polypropylene (BOPP) film accounts for a large amount of polypropylene since it is well suited for food packaging films or industrial films, because of its high performance in terms of mechanical and optical properties. Recently machine speed has been increasing to obtain higher production rate and film thickness has become thinner to reduce the environmental load. To meet the demands, many researchers have been investigating stretchability of PP by connecting the stretching force at the yield point and crystalline structure. Many other studies have been conducted regarding the surface structure of BOPP. Although there were some cases that crater‐like film surface roughness was formed on BOPP films, the formation mechanism of craters has not been clarified. In this report, new hypothesis of the crater‐like film surface roughness formation mechanism is proposed by observing the transformation of crater from sheet to BOPP film and by investigating the relationship between the stress–strain curve and surface roughness change. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Application of confocal laser scanning microscope technique to visualize dynamic sorption behavior of perylene in cellulose acetate film

Additives distributed in a polymer film were visualized by a confocal laser scanning microscope (CLSM) in this study. Cellulose acetate (CA) was used as the polymer film material. Perylene as a fluorescence reagent and glycerol triacetate (GTA) as a plasticizer for CA, respectively, were selected and mixed for visualizing the absorption of perylene into CA. Under optimized CLSM conditions of an objective lens (dry, 20×) and diode laser (408 nm, 290–330 μW), a fluorescent penetrant, perylene, in GTA solution was detected in CA casting film within around 9 μm depth of the film in 60 minutes after starting the sorption study. It was also found that the fluorescence intensity of perylene became lower with the film depth. This finding suggested that CLSM could visualize the sorption behavior of perylene as a dynamic diffusion process. Analytical conditions, such as a scanning range along the Z axis (±10 or ±30 μm from an air‐contact surface of the CA film) and a scan speed (1 or 30 fps) of CLSM, did not affect the fluorescence intensity of the sorbed perylene. It was concluded that a newly developed analytical methodology using CLSM was sufficient for visualizing the perylene penetrant across the cross‐sectional distribution of the CA film, being capable of monitoring the sorption behavior of compounds in polymer materials without any destruction of a given absorbed film. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

聚丙烯加工稳定化技术最新进展

介绍了国外的抗氧剂、阻燃剂等加工助剂应用方面的研究成果,包括不同稳定剂对加工性能的影响以及各种稳定剂加入到聚丙烯树脂中的方法。     

Influence of synergists: The influence of hydroperoxide decomposers on phenolic inhibitors consumption in oxidized polypropylene

The influence of sulphur‐ and phosphorum‐containing substances (hydroperoxide decomposers) on the kinetics of the consumption of two phenolic antioxidants in polypropylene (PP) was studied. The induction periods of PP autoxidation at 130°C were measured in the presence of inhibiting compositions that consisted of phenolic inhibitors and decomposers of hydroperoxide. Obtained results indicated that the influence of the hydroperoxide decomposer became significant when the concentration of the phenolic antioxidant became close to critical value. It also was shown that the efficiency of the hydroperoxide decomposer significantly depended on the mechanism of the transformation of the phenolic inhibitor; and first of all on the nature of its transformation products. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2239–2243, 2002     

Aging of air-corona-treated polypropylene film

X-ray photoelectron spectroscopy (ESCA), wettability measurements, and an ink adhesion test were used to characterize changes in the surface properties of air-corona-treated polypropylene (PP) films upon aging under a variety of storage conditions. No changes in ESCA O/C atomic ratios as a function of aging were observed for corona-treated PP films. The wettability data indicated a slight decrease in wettability upon aging. Aging did not affect ink adhesion for the particular PP and ink studied. The responses obtained were independent of the various film storage conditions employed. The slight decrease in wettability observed upon aging was attributed to reorientation of oxidized functionalities within the surface region.     

聚丙烯流延膜专用料的研制与开发

介绍了上海石油化工股份有限公司开发的聚丙烯流延膜专用料的性能、生产工艺、种类及用途。     

Solubility of high molecular weight,sterically hindered amines in polypropylene

The dissolution of four sterically hindered amines with molecular weights from 1364 to 2758 was studied in polypropylene in the interval, 60–130°C. The solubility of the additives at 100°C passes through a maximum during time and the maximum solubility increases with increasing additive molecular weight. The rearrangement of the polymer structure during additives dissolution is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 883–889, 2000     

Flame surface modification of polypropylene film

Contact-angle measurements, the ASTM standard wetting test for polyolefin films, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize flame-treated polypropylene (PP) films. Two combustion models, STANJAN and PREMIX, were then used to determine the chemical and physical properties of the flames used to treat the PP films. Both the flame equivalence ratio and the position of the PP film in the flame are important variables in determining the extent of oxidation and improvement in wettability obtained by flame treating. The optimal equivalence ratio for the flame treatment of PP is 0.93, while the optimal luminous flame-to-film distance is 0-2 mm. Modeling of the combustion processes occurring in the flame provides evidence that the extent of treatment correlates closely with the concentrations of H, O, and OH radicals present in the flame. The extent of surface modification of the flame-treated PP does not appear to correlate with either the flame temperature or the concentraion of oxygen molecules. The mechanism of surface oxidation by flame treatment probably involves polymer-radical formation by O and OH, followed by rapid reaction of the polymer radicals with O, OH, and O₂.     

Experimental determination of concentration dependence of nitrogen diffusivity in polypropylene

This study determines the diffusivity of nitrogen as a function of its concentration in polypropylene at 170, 180, and 190°C in the range, 0.99–6.75 MPa. Isothermal pressure decay experiments are utilized to obtain the uptake of nitrogen by polypropylene with time. These data when used with a detailed mass transfer model, and the principles of variational calculus allow the determination of the nitrogen diffusivity. It is found to be a peak function with values in the range of 3.88 × 10^?9 to 12.94 × 10^?9 m² s^?1. Suitable correlations are found to represent the diffusivity in terms of pressure and nitrogen concentration at the three temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Plastic behavior of monoclinic polypropylene under hydrostatic pressure in compressive testing

The plastic deformation of monoclinic isotactic polypropylene is studied in compressive testing with particular attention to the effect of hydrostatic pressure up to 300 MPa, in the temperature range 20–60°C. The coefficients of the Coulomb criterion are fairly consistent with those assessed from the comparison of the tensile and compressive yield stresses at atmospheric pressure, in the same temperature range. The high friction coefficient of polypropylene is ascribed to a strain‐induced order‐to‐disorder transition from the monoclinic to the smectic form accompanied by an increase of specific volume. This local and transient phase change is assumed to result from the mobile conformational chain defects that govern the elementary mechanism of plasticity in the crystalline phase of polypropylene consisting of 3/1 helix chains. A comparative discussion is made with polyethylene that displays a much lower friction coefficient. The dislocation‐based approach that is proposed in relation to the viscoelastic relaxation processes provides a new insight into the molecular grounds of the elementary mechanism of plasticity of polypropylene. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1241–1247, 1999     

Orientation and crystallinity in film casting of polypropylene

In the cast film process a polymer melt is extruded through a slit die, stretched in air, and cooled on a chill roll. During the path in air the melt cools while being stretched. Film casting experiments were carried out with an isotactic polypropylene resin. The temperature and width distributions were measured along the draw direction. Further, the crystallinity and Hermans orientation factor were measured on the final film. The process was described by a simple thermomechanical model derived elsewhere. The evolution of the molecular orientation parameters was calculated on the basis of a dumbbell model coupled with velocity and temperature distributions provided by the thermomechanical model. The experimental crystalline orientations of the final films collapsed into a single step‐shaped curve (from low to high orientation) if plotted versus the stress calculated by the model at the frozen line. The experimental values of the crystallinity and Hermans orientation factors are discussed on the basis of predictions of the dumbbell model for melt orientation at the frozen line and the crystallinity data obtained in quiescent conditions under the same cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1981–1992, 2002; DOI 10.1002/app.10422     

Functionalization of polypropylene film by radiation grafting of acryloyl chloride and subsequent esterification with Disperse Red 1

Polypropylene (PP) films were grafted with acryloyl chloride by γ‐irradiation, and the grafted films were reacted with an azo dye, Disperse Red 1. The films were characterized by X‐ray diffraction, scanning electron microscopy, atomic force microscopy, and differential scanning calorimetry. It was found that the grafting takes place first on the film surface, and with increase in the radiation dose the grafting penetrated inside of the film, decreasing the crystallinity of the PP film. The surface of the films was homogeneous, and a mesophase was observed for the film grafted with the dye through a polarized optical microscope. The dye underwent trans to cis photoreaction, whereby the red films became colorless by the irradiation of UV light at room temperature, although the color was recovered on standing, and more quickly when heated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 172–178, 2004     

聚丙烯薄膜与铜箔的粘接

通过聚丙烯薄膜和铜箔的表面处理和胶粘剂的选择,对它们的粘接进行了研究,经胶接接头的剥离强度和耐溶剂性能测试,筛选出粘接强度高、耐溶剂性能良好粘接接头,结果铜箔和聚丙烯薄膜的最高的剥离强度可达到14N/cm,与不经任何处理的空白试样相比,增加近7倍。     

氯化聚丙烯溶度参数的研究

氯化聚丙烯是对聚丙烯材料有很好的粘结力 ,为了进行基础的应用研究 ,用浊度法对其溶度参数进行了测定 ,得到其溶度参数为 16 .72～ 2 1.15 (J/cm3 ) 1/ 2 。氯化聚丙烯溶解性能实验表明 :氯化聚丙烯属于弱极性物质。在溶度参数接近时 ,一般弱极性溶剂为良溶剂 ,中等极性溶剂为微溶溶剂。还用三维溶度参数对CPP的溶解性能进行了讨论。     

Accelerated ageing of polypropylene stabilized by phenolic antioxidants under high oxygen pressure

Polypropylene (PP) samples stabilized by a hindered phenol (Irganox 1010) were submitted to thermal ageing at 80°C in air at atmospheric pressure or in pure oxygen at 5.0 MPa pressure. Both the polymer oxidation and the stabilizer consumption were monitored by Infrared spectrometry and thermal analysis. The stabilizer efficiency, as assessed by the ratio induction time/stabilizer concentration is almost constant at atmospheric pressure even when the stabilizer concentration is higher than its solubility limit in PP (0.4% or 24 × 10^?3 mol L^?1). In contrast, at high pressure, the efficiency decreases almost hyperbolically with the stabilizer concentration when this latter is higher than 6.0 × 10^?3 mol L^?1. The results indicate the existence of a direct phenol‐oxygen reaction negligible at low oxygen pressure but significant at 5.0 MPa pressure. The reality of this reaction has been proved on the basis of a study of the thermal oxidation of a phenol solution in a nonoxidizable solvent. A kinetic model of PP oxidation in which stabilization involves three reactions has been proposed. It simulates correctly the effect of oxygen pressure and stabilizer concentration on carbonyl build‐up and stabilizer consumption. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008