反应性单体改性PP/PS共混物结晶与熔融行为

制备了三种反应性单体和两种PP接枝物改性的PP／PS共混物,用DSC研究了改性PP／PS共混物的结晶与熔融行为。结果表明：PS的加入提高了PP的结晶温度,两种接枝物的加入进一步提高共混物中PP的结晶温度,少量反应性单体对结晶温度影响不大,但高用量时则明显提高共混物的结晶温度;外加接枝物或者反应性单体对共混物中PP的熔融温度影响不大,但是熔融峰形与结晶温度高低有关。     

颗粒内受限聚合法制备PP/POE/PS合金

以等规聚丙烯/乙烯-辛烯共聚物(PP/POE)合金颗粒为扩散基体, 苯乙烯(St)为扩散单体, 利用颗粒内受限聚合法制备了PP/POE/PS三元合金. 结果表明, 对于POE质量分数为20%~40%的PP/POE合金颗粒, St均可扩散至直径为4 mm的颗粒中心部位, 在POE非晶相中生成相尺寸为几十至几百纳米的PS球. 在PP/POE合金颗粒的不同部位, 因POE相尺寸及单体的吸附量不同, 生成的PS相尺寸也不同, 在颗粒中心部位生成的PS球最小. 研究了St在PP/POE(质量比80: 20)颗粒中的扩散-聚合行为, 结果表明, St在合金颗粒中的扩散速率和扩散饱和值远大于在纯PP颗粒中的扩散速率和饱和值, 这主要是因为PP/POE合金颗粒中的非晶POE相有利于扩散. 改变单体投料量可以获得具有不同PS含量的PP/POE/PS三元合金. 结晶性能研究结果表明, PS在非晶POE相中的优先分布会使POE相体积增大, 从而使PP的结晶温度和熔融温度降低. 随着PS量的进一步增大, 分布在PP中的PS对PP有结晶成核作用.     

The influence of nano‐PS particle on structure evolution and electrical properties of PP/PS

The polypropylene‐g‐polystyrene (PP‐g‐PS) copolymers with different grafting ratios are used as compatibilizers to control the size of polystyrene (PS) particles at nanometer scale in polypropylene (PP) matrix. Then the PP/PS insulating nanocomposites (containing 10 wt % PS calculated from PS and PP‐g‐PS) are manufactured. With the increase in grafting ratio of PP‐g‐PS, the size of PS particle is reduced and the interfacial adhesion is enhanced. Meanwhile, the dielectric properties, DC breakdown strength and volume resistivity are increased with the decreasing of PS particle size. The spherulite size of PP is decreased and the boundary between crystals and amorphous regions is blurred or even disappears due to the presence of PS nanoparticles. This evolution of PP structure is attributed to the serious entanglements of PP and PS molecular chains. Finally, the correlation between morphological structure and electrical properties is ultimately established based on the in‐depth understanding of the molecular chain movement, crystal structure, and phase morphology. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 706–717     

Mechanical properties and characteristic of surface treated bamboo fiber reinforced PP/PS blends

Bamboo fiber (BF) as organic filler is characterized by mechanical properties analysis and morphology examination for polypropylene (PP) and polystyrene (PS) matrix blends. Effects of different filler content on tensile strength, flexural properties, and impact strength are proposed. It is observed from scanning electron microscopy (SEM) studies that addition of BF is beneficial in increasing mechanical strength via increasing the interface dispersed phase. The optimum tensile properties and impact properties of BF content were at 40 wt% for PP/PS/BF composite on melt mixing conditions. The results showed a significant improvement in mechanical properties of PP/PS/BF ternary blend composite. Comparing with untreated BF, content of carbon and nitrogen of treated BF decreased to 66.57 and 2.31%, oxygen content increased to 21.07%, and silicon content increased from 0 to 10.04%. The element ratio of O/C, N/C, and Si/C changed to 31.65, 3.47, and 15.08, respectively.     

Combined effect of compatibilizer and carbon nanotubes on the morphology and electrical conductivity of PP/PS blend

In this work, maleic anhydride grafted styrene–ethylene–butadiene–styrene copolymer (SEBS‐g‐MA) and carbon nanotubes (CNTs) were introduced into the immiscible polypropylene/polystyrene (PP/PS) blend. Among the three polymer components, SEBS‐g‐MA has the strongest affinity to CNTs; thus, it exhibits dual effects to adjust the phase morphology of the blends and the dispersion state of CNTs in the blends. The experimental observations obtained from morphology characterizations using scanning electron microscope and transmission electron microscope confirm the selective localization of CNTs at the interface of the immiscible PP/PS blend. As a consequence, largely decreased percolation threshold is achieved when most of CNTs are selectively localized at the interface region between PP and PS. Copyright © 2014 John Wiley & Sons, Ltd.     

Selection of the optimum concentration range for reflectance spectrophotometric analysis

Two graphical methods for selecting the optimum range and determining the maximum accuracy of reflectance spectrophotometric analysis are discussed. Results obtained with the use of two systems (Rhodamine B, which absorbs in the visible region of the spectrum, and aspirin, which absorbs in the ultraviolet region, both adsorbed on silica gel) are employed to illustrate how the methods might be employed in practice. Experimental results are contrasted with those expected by application of the Kubelka-Munk equation. The results indicate that the minimum relative error in concentration to be expected in reflectance spectrophotometric analysis is about 6% per 1 % reading error, and that the optimum range for analysis can be arrived at after plotting the reflectance data for either of the two systems discussed, whether the system conforms to the Kubelka-Munk equation or not.     

Fractionated crystallization and morphology of PP/PS blends in the presence of silica nanoparticles with different surface chemistries

The fractionated crystallization behavior of polypropylene (PP) droplets in its 20/80 blends with polystyrene (PS) in the presence of hydrophilic or hydrophobic fumed silica nanoparticles was studied by using differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It was found that the fractionated crystallization of PP droplets in the PS matrix was promoted by adding a low content of hydrophobic or hydrophilic nanoparticles due to their morphological refinement effect. However, discrepancies in the fractionated crystallization behavior of PP droplets occurred as the nanoparticle content increased. The crystallization became dominated by the heterogeneous nucleation effect of high content of hydrophilic nanoparticles, which possibly migrated into PP droplets during mixing and significantly suppressed their fractionated crystallization. In contrast, the morphological refinement effect still played a dominated role in promoting the fractionated crystallization of PP droplets in PP/PS blends filled with higher content hydrophobic nanoparticles as a result of the efficiently morphological refinement effect.     

Evaluation of Morphology and Deformation Micromechanisms in Multilayered PP/PS Films: An Electron Microscopy Study

Nanostructured polymers and ultra-thin polymer layers are used more and more in technical applications like nanotechnology and microelectronics. Therefore, it is really important to understand the size-scale dependent properties as bulk polymers become thinner and more two-dimensional. Here the morphology as well as the macroscopic and the microscopic deformation behaviour of multilayered films of polypropylene (PP) and polystyrene (PS) have been investigated. For investigation different microscopic techniques and tensile testing were used. The films were prepared by multilayer coextrusion, whereas the composition of PP and PS and the film thickness – and therefore the thickness of each layer – varied. The thinnest calculated thickness of a single layer was about 5 nm. It is shown that the PP/PS films consist usually of homogeneous layers with only few defects. As the composition of PP/PS deviates strongly from 50/50 or the films get thinner the number of defects increases and the layered system turns to irregular lamellar system. In macroscopic tensile tests the small PS layers affect the elongation at break enormously: Most of the samples are brittle. For the films with a composition of PP/PS 90/10 and the film PP/PS 70/30 with a film thickness of 25 µm an elongation at break of 66% and higher could be reached. Transmission electron microscopy on these samples shows that the layers are characterized by plastic yielding in local deformation zones.     

Large impact in electrical properties of polypropylene by improving the filler-matrix interface effect in PP/PS blends

Inorganic nanoparticles are widely used to improve space charge behavior, DC breakdown strength and other electrical properties of polymer insulating materials, but the uniform distribution of inorganic nanofillers in matrix is difficult due to their agglomeration and bad compatibility with the polymeric matrix. In this paper, polypropylene (PP)/polystyrene (PS) blends were prepared to suppress space charge accumulation and improve DC breakdown strength. Polypropylene-g-polystyrene (PP-g-PS) graft copolymer was used as compatibilizer to improve the compatibility of PP matrix and PS filler. The evolution of microstructure of PP/PS blends were investigated by scanning electron microscope (SEM), the space charge distributions were measured by a pulsed electro-acoustic (PEA) system, and DC breakdown strength was also tested. The morphologies show that the size of PS particles reduced to 310 nm when the content of PP-g-PS graft copolymer increased to 24 wt%, and the interaction between PP matrix and PS particles enhanced. The presence of PS particles in all PP/PS blends suppressed the space charge accumulation compared to neat PP, but the DC breakdown strength in uncompatibilized blend was lower than neat PP. The increasing of content of PP-g-PS improved the DC breakdown strength with the maximum value of 408.9 kV/mm was obtained. This may attribute to excellent interface structure formed between PP matrix and PS particles.     

Derivative spectrophotometry in the determination of phenyl-beta-naphthylamine used as an antioxidant in rubber mixtures

A method for the determination of phenyl-beta-naphthylamine (PBN) in ternary mixtures by second-derivative spectrophotometry is described. The procedure works without any separation step of PBN from the other polymer additives. By applying the second-derivative spectrophotometry, Beer's law was valid over the range 0.25-10 micro g mL(-1). The proposed method has been applied to the determination PBN in synthetic ternary mixtures and rubber samples. A comparative study of the results obtained using the second and the third-derivative spectrophotometric methods is presented and evaluated. The derivative spectrophotometric method indicated that the amount of PBN found after extraction from the rubber samples was 0.97+/-0.02 g/100 g of sample.     

The influence of adding marble and granite dust on the mechanical and physical properties of PP composites

Journal of Thermal Analysis and Calorimetry - The purpose of this work is to investigate the opportunity of re-using M&G wastes to get novel PP composites. Recycling of marble and granite...     

The relationship between purely stochastic sampling error and the number of technical replicates used to estimate concentration at an extreme dilution

For any analytical system the population mean (μ) number of entities (e.g., cells or molecules) per tested volume, surface area, or mass also defines the population standard deviation $ (\sigma = \sqrt {\mu } ) For any analytical system the population mean (μ) number of entities (e.g., cells or molecules) per tested volume, surface area, or mass also defines the population standard deviation (s = ?{m} ) (\sigma = \sqrt {\mu } ) . For a preponderance of analytical methods, σ is very small relative to μ due to their large limit of detection (>10² per volume). However, in theory at least, DNA-based detection methods (real-time, quantitative or qPCR) can detect ≈ 1 DNA molecule per tested volume (i.e., μ ≈ 1) whereupon errors of random sampling can cause sample means ([`(x)] \overline x ) to substantially deviate from μ if the number of samplings (n), or “technical replicates”, per observation is too small. In this work the behaviors of two measures of sampling error (each replicated fivefold) are examined under the influence of n. For all data (μ = 1.25, 2.5, 5, 7.5, 10, and 20) a large sample of individual analytical counts (x) were created and randomly assigned into N integral-valued sub-samples each containing between 2 and 50 repeats (n) whereupon N × n = 322 to 361. From these data the average μ-normalized deviation of σ from each sub-sample’s standard deviation estimate ( s<sub>j</sub> ;  j = 1  to  N;  N = 7  [ n = 50 ]  to  180  [ n = 2 ] )\left( {s_j ;\;j = 1\;{\hbox{to}}\;N;\;N = 7\;\left[ {n = 50} \right]\;{\hbox{to}}\;180\;\left[ {n = 2} \right]} \right) was calculated (Δ). Alternatively, the average μ-normalized deviation of μ from each sub-sample’s mean estimate ([`(x)]_j {\overline x_{\rm{j}}} ) was also evaluated (Δ′). It was found that both of these empirical measures of sampling error were proportional to ^{{ - 2}}?{n ·m} \sqrt[{ - 2}]{{n \cdot \mu }} . Derivative (∂/∂n · Δ or Δ′) analyses of our results indicate that a large number of samplings (n ? 33±3.1) (n \approx {33}\pm {3}.{1}) are requisite to achieve a nominal sampling error for samples with a μ ≈ 1. This result argues that pathogen detection is most economically performed, even using highly sensitive techniques such as qPCR, when some form of organism cultural enrichment is utilized and which results in a binomial response. Thus, using a specific gene PCR-based (+ or −) most probable number (MPN) assay one could detect anywhere from 0.2 to 10⁵ CFU mL⁻¹ using 6 to 48 reactions (i.e., 8 dilutions × 6 replicates per dilution) depending on the initial concentration of the pathogen and volume sampled.     

A computational methodology for accurate predictions of rate constants in solution: Application to the assessment of primary antioxidant activity

The accurate prediction of rate constants for chemical reactions in solution, using computational methods, is a challenging task. In this work, a computational protocol designed to be a reliable tool in the study of radical‐molecule reactions in solution is presented. It is referred to as quantum mechanics‐based test for overall free radical scavenging activity (QM‐ORSA) because it is mainly intended to provide a universal and quantitative way of evaluating the free radical scavenging activity of chemical compounds. That is, its primary antioxidant activity. However, it can also be successfully applied to obtain accurate kinetic data for other chemical reactions in solution. The QM‐ORSA protocol has been validated by comparison with experimental results, and its uncertainties have been proven to be no larger than those arising from experiments. Further applications of QM‐ORSA are expected to contribute increasing the kinetic data for free radical‐molecule reactions relevant to oxidative stress, which is currently rather scarce. © 2013 Wiley Periodicals, Inc.     

Laser Induced Breakdown Spectroscopy methodology for the analysis of copper-based-alloys used in ancient artworks

In this paper Laser Induced Breakdown Spectroscopy has been applied for determining the elemental composition of a set of ancient bronze artworks coming from archaeological site of Minervino Murge — Southern of Italy (dated around VII b.C.). Before carrying on the analysis of the archaeological samples, the characterization of the analytical technique has been accomplished by investigating the trueness of the typical assumptions adopted in LIBS, such as Local Thermodynamic Equilibrium, congruent ablation and plasma homogeneity. With this purpose, two different laser pulse durations, 7 ns and 350 fs, have been used. We have focused our attention on LIBS analysis of bronze standards by considering and discussing the bases of both methodology and analytical approach to be followed for the analysis of ancient copper-based-alloy samples. Unexpectedly, regardless from the laser pulse duration, the LIBS technique has shown, by considering an adequate approach on the emitting plasma features, that its peculiarities are anyway preserved so that a fast analysis of ancient copper-based-alloys can be achieved. After verifying the suitability of the methodology, it has been possible to fulfill the typical assumptions considered for the LIBS calibration curves method and use it for ancient bronze artworks analysis.     

Study of the antioxidant activity and total polyphenol concentration of medicinal plants

Infusions of medicinal plants are investigated by potentiometry using a system of K₃[Fe(CN)₆]/K₄[Fe(CN)₆]. Models of some flavonoids, phenol carbonic acids, ascorbic acid, and their mixtures are studied. The total polyphenol concentration in these samples is determined by the Folin–Ciocalteu method. Dependences of antioxidant activity on extraction time are obtained.     

A method to test the detectability of GC/PFPD for an extended concentration range with respect to reduced sulfur compounds

In this study, a possible means to extensively expand the quantifiable range of reduced sulfur compounds (RSC) in air has been investigated by a combined application of GC with pulsed flame photometric detector (PFPD) and a multifunction thermal desorber (TD) system. To comply with the purpose of this study, gaseous RSC standards containing the equimolar concentrations of H(2)S, CH(3)SH, DMS, DMDS, and CS(2 )were prepared at 11 concentration levels (i. e., 10 ppb-10 ppm (over 10(3 )range)). These standards were then used to derive three-point calibrations based on the modified injection through a TD (MITD). If the mean calibration slopes of each concentration level are normalized to that of CH(3)SH, the relative ordering is found as 0.65 (H(2)S): 1 (CH(3)SH): 1.34 (DMS): 2.24 (DMDS). The reproducibility of MITD method, when assessed in terms of relative standard error (RSE) for all calibration slopes, had the most stable pattern for DMDS (5.77%) and the least stable one for H(2)S (12.8%). The sensitivity of the MITD-based calibration generally improved with an increase in concentration levels of standard gas. Based on our study, the MITD technique is useful to extend quantification of GC/PFPD by allowing RSC detection over a 10(3) range.     

RPS／CPE的反应性共混及其对PS／PE的增容作用

用ＦＴＩＲ、ＤＳＣ等方法研究了含恶唑啉官能力的聚苯乙烯（ＲＰＳ）与氯化聚乙烯（ＣＰＥ）之间的反应。ＲＰＳ、ＣＰＥ、ＰＳ、ＰＥ在不同温度下用反应式挤出要熔融共辊，结果表明，ＲＰＳ／ＣＰＥ对ＰＳ／ＰＥ共混物具有增容作用，提高了共混物的力学性能。此反应性共混适宜在较低温度下进行，对ＲＰＳＣＰＥ共混物还进行了动态力学表征，并与ＲＰＳ进行比较以进一步了解共混物的特征。     

动态硫化EPDM／PP共混体系中PP相的结晶度及晶体结构的研究

研究了动态硫化ＥＰＤＭ／ＰＰ共混物中ＰＰ相的结晶度及晶体结构,同时讨论了制备工艺条件以共混物中ＰＰ相的结晶度和晶体结构的影响。结果表明：在动态硫化ＥＰＤＭ／ＰＰ共混物中,硫化的ＥＰＤＭ的分子键没有穿入ＰＰ的晶区,ＰＰ的结晶度随ＥＰＤＭ含量的增加而下降。提高共混温度,加入软化剂或碳黑均使共混物中ＰＰ的结晶度降低,共混时间１５ｍｉｎ时,共混物中ＰＰ相的结晶度最低,但ＰＰ的晶格不受制备工艺条件的影响。