Computer simulation studies of the miscibility of poly(3-hydroxybutyrate)-based blends

By means of the molecular dynamics simulation method, the miscibility of poly(3-hydroxybutyrate)/polyethylene (PHB/PE) blend has been investigated. Two glass transition temperatures of the PHB/PE are found by scrutinizing its volume-temperature curve, and this result is qualitatively in agreement with the experimental results. To further analyze the miscibility of poly(3-hydroxybutyrate)-based blends, the Flory-Huggins parameters of PHB/PE, poly(3-hydroxybutyrate)/poly(ethylene oxide) (PHB/PEO), poly(ethylene oxide)/polyethylene (PEO/PE) have been calculated via a Monte Carlo scheme, and the morphology of the PHB/PEO and the PHB/PE blend has been simulated using dissipative particle dynamics method. The time evolution of dividing interface for PHB/PEO/PE blend shows a dynamic phase separation process. All these results indicate that PHB and PEO tend to mix together, whereas PE aggregates to form PE-rich domains in the PHB/PE and PHB/PEO/PE blends.     

The effect of interfacial miscibility on the cell morphology of polyethylene terephthalate/bisphenol a polycarbonate blend foams

Annealing polyethylene terephthalate (PET)/polycarbonate (PC) blends enhance the transesterification reaction and increase the amount of copolymer at the interface of both polymers. The copolymer enhances the compatibility of PET with PC, because it contains both PET and PC blocks, which causes the interface between PET and PC to become fuzzy. When the PET/PC undergoes batch physical foaming with CO₂, the copolymer significantly changes the resulting cell morphology, that is, the annealing time. Before annealing or in the absence of the copolymer, bubble nucleation occurs and dominates growth at the interface. When the PET/PC blends are annealed, the interface impedes bubble nucleation and growth. The polymer is stretched at the interface by bubble growth, forming fibril‐like structures connecting two polymer domains at the interface. Increased annealing time causes the interface to become more homogeneous and makes heterogeneous bubble nucleation difficult. At higher copolymer concentrations, the interface of PET and PC becomes fuzzy and the cell morphology becomes like those of foamed homogeneous polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

The Role of Phase Migration of Carbon Nanotubes in Melt-Mixed PVDF/PE Polymer Blends for High Conductivity and EMI Shielding Applications

In this work, the effects of blend ratio and mixing time on the migration of multi-walled carbon nanotubes (MWCNTs) within poly(vinylidene fluoride) (PVDF)/polyethylene (PE) blends are studied. A novel two-step mixing approach was used to pre-localize MWCNTs within the PE phase, and subsequently allow them to migrate into the thermodynamically favored PVDF phase. Light microscopy images confirm that MWCNTs migrate from PE to PVDF, and transmission electron microscopy (TEM) images show individual MWCNTs migrating fully into PVDF, while agglomerates remained trapped at the PVDF/PE interface. PVDF:PE 50:50 and 20:80 polymer blend nanocomposites with 2 vol% MWCNTs exhibit exceptional electromagnetic interference shielding effectiveness (EMI SE) at 10 min of mixing (13 and 16 dB, respectively-at a thickness of 0.45 mm), when compared to 30 s of mixing (11 and 12 dB, respectively), suggesting the formation of more interconnected MWCNT networks over time. TEM images show that these improved microstructures are concentrated on the PE side of the PVDF/PE interface. A modified version of the “Slim-Fast-Mechanism” is proposed to explain the migration behavior of MWCNTs within the PVDF/PE blend. In this theory, MWCNTs approaching perpendicular to the interface penetrate the PVDF/PE interface, while those approaching in parallel or as MWCNT agglomerates remain trapped. Trapped MWCNTs act as barriers to additional MWCNTs, regardless of geometry. This mechanism is verified via TEM and scanning electron microscopy and suggests the feasibility of localizing MWCNTs at the interface of PVDF/PE blends.     

氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物及其马来酸酐接枝共聚物增韧聚对苯二甲酸乙醇酯共混材料的辐射效应

采用双螺杆熔融共混的方法制备了含三羟甲基丙烷三丙烯酸酯(TMPTA)的聚对苯二甲酸乙二酯/氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物（PET/SEBS）和聚对苯二甲酸乙二酯/马来酸酐接枝氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物（PET/SEBS-g-MAH）共混材料,并在Co-60源中对其进行辐照。 通过对共混材料的力学性能、相态结构测和凝胶含量分析,对比研究了辐射对以上2种共混材料结构及性能的影响。 扫描电子显镜观察和凝胶含量分析结果表明,在适量TMPTA存在时,辐射有效地改善了PET/SEBS体系的相容性。 冲击强度的变化证实了这种增容效应,当SEBS的质量分数为20%、TMPTA质量分数为1%,经50 kGy辐照后,冲击强度达到17.3 kJ/m2。 当在SEBS分子链上引入马来酸酐官能团,辐照后,体系的相态结构变化并不明显,冲击强度最大值仅为11.5 kJ/m2,明显低于不含马来酸酐官能团的体系。     

Solvatochromic studies on the hydrogen-bond donating and dipolarity/polarizability properties of the polyethylene oxide/silica interface

The polarity of the polyethylene oxide(PEO)/silica interface in 1,2-dichloroethane as solvent is classified by means of linear solvation energy (LSE) relationships . The properties of the bare silica particle surface and the silica/PEO interface is expressed by two terms: the dipolarity/polarizability (π*) of the interface and the hydrogen-bond donating ability (α) of the surface silanols. These terms can be defined by using the Kamlet–Taft solvent parameters α and π* as a reference system. The interfacial polarity parameters α and π* were calculated by means of correlation analyses of the energy of the UV/vis absorption maxima of the surface polarity indicators: di-cyano-bis(1,10-phenanthroline) iron II, bis-4,4′-(N,N-dimethylamino) benzophenone, and 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridino)phenolate when adsorbed onto the PEO/silica particle surface. The experimental values of the E _T(30) parameter of the PEO/silica interface are compared with independently calculated values employing specific LSE relations derived for well-behaved regular solvents and functionalized silicas. PEO adsorption on silica causes a decrease in the value of the α parameter of the silica surface and an evident increase in the dipolarity/polarizability of the interface. Received: 16 December 1998 Accepted in revised form: 8 January 1999     

First‐principles study of the TiN(111)/ZrN(111) interface

The TiN(111)/ZrN(111) interface was studied by first‐principles method to provide the theoretical basis for developing the TiN/ZrN coatings. Twelve geometry structures of TiN(111)/ZrN(111) interfaces were established. The calculated interfacial work of adhesion reveals that the N‐terminated TiN/N‐terminated ZrN interface with TL site shows the strongest stability. For this TiN(111)/ZrN(111) interface, the results of the partial density of state indicate that the chemical bonding at the interface appeals both ionic and covalent characteristic, which is same as that in the bulk materials. The partial density of states for Zr, Ti, and N atoms at the interface are very similar with those in the bulk, which reveals that the electronic structure transition at the interface is smooth. The results of charge density and charge density difference demonstrate that the lost charge of Ti atom is larger than that of Zr atom, indicating that TiN is more ionic than ZrN. Calculations of the work of fracture indicate that the mechanical failure of the ZrN(111)/TiN(111) interface will take place at the interface. Besides that, the calculation result of the TiN(111)/ZrN(111) interface implies that the TiZrN₂ phase might be formed at the interface because the contacting of the N―N bond is the most stable.     

Design of aluminum trihydroxide and P‐N core‐shell structures and their synergistic effects on halogen‐free flame‐retardant polyethylene composites

In order to improve the performance of inorganic/organic composites, aluminum trihydroxide (ATH) core composites with a styrene‐ethylene‐butadiene‐styrene block copolymer grafted with maleic anhydride (MAH‐g‐SEBS) shell phase, and P‐N flame retardant as a synergistic agent, were prepared through an interface design. The effects of polyethylene glycol (PEG) content on the interfacial interaction, flame retardancy, thermal properties, and mechanical properties of high‐density polyethylene (HDPE)/ATH composites were investigated by small angle X‐ray diffraction, rotational rheometer, limiting oxygen index, thermogravimetric analysis (TGA), and tensile testing. The ATH synergistic effects of P‐N flame‐retardant improved the combustion performance of HDPE/ATH/PEG(3%)/MAH‐g‐SEBS/P‐N (abbreviated as HDPE/MH3/M‐g‐S/P‐N) composite by forming more carbon layer, increased the elongation at break from 21% to 558% compared to HDPE/ATH, and increased the interface thickness from 0.447 to 0.891 nm. SEM results support the compatibility of ATH with HDPE increased and the interfacial effect was enhanced. TGA showed the maximum decomposition temperature of the two stages and the yield of the residue at high temperature increased first and then decreased with the increase of PEG content. Rheological behavior showed the storage modulus, complex viscosity, and the relaxation time initially increased and then decreased with the increase of PEG content indicating PEG, M‐g‐S, and ATH powder gradually formed a partial coating, then a full coating, and finally an over‐coated core‐shell structured model.     

一类新型PTC复合材料的制备及性能

一类新型ＰＴＣ复合材料的制备及性能杜伟坊,杜海清（湖南大学材料科学及应用化学研究所,长沙,４１００８２）关键词正温度系数,聚乙烯,ＹＢａ_２Ｃｕ_３Ｏ_（７－ｘ）具有正温度系数（ＰＴＣ）的材料在其转化温度附近具有电阻率大幅度上升的特点,因而在温度检测与?..     

Rheological properties and interfacial slip of a multilayer structure under dynamic shear

Interfacial slip between polymer melt under steady shear has been studied using a simplified multilayer structure. In this investigation, interfacial slip under dynamic shear was studied by calculating the angular displacements of the multilayer structure and its component layers. On the basis of the angular displacements, a slip index was defined to quantify the degree of interfacial slip. A relationship governing the rheological behavior of the multilayer structure under slip and nonslip condition was established. These results were correlated with equations derived from consideration of energy equilibrium in the multilayer structure. Polymer multilayer structures of high‐density polyethylene/polystyrene and liquid crystal polymer(LCP)/poly ethylene naphthalate(PEN) were investigated. Of all the polymers investigated, large interfacial slip was found at LCP/PEN interface under dynamic shear. The high rigidity and alignment along the interface of LCP molecules was believed to prevent chain entanglement in the interfacial layer and therefore promote interfacial slip at the interface. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2683–2693, 2005     

Anisotropy analysis of energy in Ag/Si twist interface

The energies in three combinations of Ag(001)/Si(111), Ag(011)/Si(111) and Ag(111)/Si(111) twist boundaries have been calculated using the modified embedded atom method (MEAM). The results show that the interface energies corresponding to Ag(111)/Si(111), Ag(001)/Si(111) and Ag(011)/Si(111) increase successively and the lowest energies 365, 717.7 and 996.1 mJ m^?2 corresponding to each interface appear at twist angles θ of 30, 0 and 25.24°, respectively. Considering minimization of interface energy, we can conclude that the Ag films deposited on Si(111) substrate will result in a (111) preferred orientation, especially at a twist angle of θ = 30°. Copyright © 2005 John Wiley & Sons, Ltd.     

Preparation and characterization of PE and PE-g-MAH/montmorillonite nanocomposites

Polyethylene (PE) was chemically modified with grafting maleic anhydride (MAH) monomer on its backbone at first. Then the melt-direct intercalation method was employed to prepare two kinds of nanocomposites, polyethylene (PE)/organic montmorillonite (Org-MMT) and maleic anhydride grafted polyethylene (PE-g-MAH)/Org-MMT nanocomposites. X-ray diffractometery (XRD) was used to investigate the intercalation effect and transmission electron microscopy (TEM) to observe the dispersion of Org-MMT interlayers in matrixes. The results show that an intercalated structure would be acquired on mixing the PE and Org-MMT; and an almost exfoliated system would be obtained by mixing the PE-g-MAH and Org-MMT. Moreover, further measurements via thermogravimetric (TGA) and differential scanning calorimetry (DSC) showed that both of the nanocomposites had a higher thermal decomposition temperature and a higher crystallization temperature when compared to the original matrix. At the same time, the thermal and crystal properties for the PE-g-MAH prepared in this experiment are also discussed.     

Effect of diblock copolymers on dynamic mechanical properties of polyethylene/polystyrene blends

A systematic investigation of the dynamic mechanical properties of high-density polyethylene (HDPE)/high-impact polystyrene (HIPS)/copolymer blends was carried out. Blends of 80/20 weight percent of HDPE/HIPS were prepared in the melt state at 180°C in a batch mixer. Synthesized pure diblock (H77) and tapered diblock (H35) copolymers of hydrogenated polybutadiene (HPB) and polystyrene (PS) were added at different concentrations (1, 3, and 5 wt %), and the dynamic mechanical properties were investigated. The results show that: (1) both the tapered and the pure diblock copolymers enhance the phase dispersion and the interphase interactions; (2) structure and molecular weight are both important parameters in the molecular design of copolymers; (3) important effects occur when only small amounts of copolymer are added (up to the interface saturation concentration SC); (4) a micellar structure formation is possible when the copolymer is in excess in the blend; (5) the effect of the copolymer structure on the SC and the critical micellar concentration (CMC) is more pronounced than the effect of molecular weight. These concentrations are found to be lower for the tapered diblock copolymer. The analysis of the dynamic mechanical thermal analysis (DMTA) results obtained for the 20/80 HDPE/HIPS blend leads to the conclusion that the copolymers also enhance the interactions between heterogeneous phases. Similar conclusions based on electron microscopy were reported in the literature. DMTA shows great potential to relate macroscopic observations to the state of a copolymer in an immiscible blend.     

Enhanced Reproducibility of Positive Temperature Coefficient Effect of CB/HDPE/PVDF Composites with the Addition of Ionic Liquid

Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC) effect is of great significance for large-scale application of polymer based PTC composites, owing to its contribution to the security and reliability. Herein, we developed a carbon black(CB)/high density polyethylene(HDPE)/poly(vinylidene fluoride)(PVDF) composite with outstanding PTC reproducibility, by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([OMIm][NTf_2]) into the composite. After multiple repeated temperature cycles, the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%. Our studies revealed that [OMIm][NTf2] contributes to the improvement of PTC reproducibility in two ways:(i)it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends;(ii) it inhibits the crystallization of PVDF through the dilution effect, leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF. This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.     

Solubilization and location of phenethylalcohol, benzaldehyde, and limonene in lamellar liquid crystal formed with block copolymer and water

Three fragrances, phenethylalcohol, benzaldehyde, and limonene (that differ in their polarity), were solubilized in lamellar liquid crystal using the polyethylene oxide-polypropylene oxide-polyethylene oxide, (EO27PO61EO27), P104 triblock copolymer, and water. The interlayer spacing of the lamellar liquid crystal were established using small angle X-ray scattering (SAXS). The SAXS data are used to calculate the interfacial area per polyethylene oxide (PEO) block and to determine the location of each fragrance in the association structure. The results show the presence of phenethylalcohol at the interface while part of benzaldehyde contributing to the interface and the other part being located inside the polar/apolar domains. The third fragrance, limonene, did not participate in the formation of the interface and is located inside the apolar domain.     

EFFECT OF DISPERSION OF MICA IN MATRIX ON YOUNG''''S MODULUS OF MICA FILLED POLYETHYLENE

The correlation between Young's modulus of mica-filled high density polyethylene (HDPE), low density polyethylene(LDPE) and the state of dispersion of plasma-treated mica in the polymer matrices was studied. The modulus and the number average diameter of mica aggregates in matrix were determined with tensile testing and image analysis respectively. The interface structure of the filler/matrix and the bulk structure of matrix were examined through the dielectric spectrometry, differential scanning calorimetry (DSC) and dynamic viscoelastic spectrometry. The results show that the Young's modulus of the filial polyethylene depends to a great extent upon the state of dispersion of filler in matrix, but it is independent of the interface structure and bulk structure. The better the dispersion, the higher the Young's modulus.     

不对称茂金属[Me~2C(Cp)(Ind)]ZrCl~2催化剂制备支化聚乙烯的 研究

本文报道以[Me~2C(Cp)(Ind)]ZrCl~2为主催化剂,MAO为助催化剂,仅以乙烯为单体制备支化聚乙烯的结果。     

天然橡胶/聚乙烯共混体相容性的研究

本工作首先对橡胶/聚乙烯共混体系的相容性进行了计算,推测聚乙烯的非晶部分和橡胶间有一定的互容性,提出了橡胶和聚乙烯相互作用模型。然后用动态力学方法、有效网链密度测定、密度测定和广角X-射线衍射方法对天然橡胶分别未交联和交联的天然橡胶(NR)/低密度聚乙烯(LDPE)共混体系的相容性进行了验证。实验结果表明,LDPE非晶部分和NR之间存在一定的相互渗透。     

新型络合吸附剂的研究(Ⅳ)──铜(Ⅱ)、镍(Ⅱ)模板高分子多乙烯多胺吸附剂的记忆性

研究了铜(Ⅱ)、镍(Ⅱ)离子模板高分子多乙烯多胺络合吸附剂的动态吸附金属离子的行为。5个周期的动态吸附结果表明,合成的铜(Ⅱ)、镍(Ⅱ)模板吸附剂分别对铜(Ⅱ)和镍(Ⅱ)金属离子具有稳定的吸附能力,其动态饱和吸附量达4.357mmolCu(Ⅱ)/g[铜(Ⅱ)模板吸附剂]、3.153mmolNi(Ⅱ)/g[镍(Ⅱ)模板吸附剂];相对误差分别为±1.5%和±2.2%.     

Date palm fibre filled recycled ternary polymer blend composites with enhanced flame retardancy

Flammability of recycled polypropylene (PP)/low density polyethylene (LDPE)/high density polyethylene (HDPE) ternary blends containing date palm fibres is investigated in this study. Melt blending is used for the composite preparation and the palm fibres induce good mechanical strength to the blend composites. The effect of flame retardant magnesium hydroxide, is studied through the limiting oxygen index analysis and cone calorimeter studies. Morphology of the palm fibres in presence of fire retardant reveals interesting facts of base hydrolysis. Since the polymers used are recycled ones and the fibres are obtained from the date palm leaves, the whole composite manufactured stands as low cost, less energy consuming and environmental friendly. Though the flame retardant reduced the mechanical properties, the palm fibres strengthened the whole composite thus helping to achieve the flame retardancy and mechanical properties simultaneously. Flame retardancy is correlated with the thermal degradation and thermal conductivity of the blend fibre composites as well.     

Effect of compatibilizer on morphology and properties of HDPE/Nylon 6 blends

The compatibilization effect of linear low‐density polyethylene‐grafted maleic anhydride (LLDPEgMA) and high‐density polyethylene‐grafted maleic anhydride (HDPEgMA) on high‐density polyethylene (HDPE)/polyamide 6 (Nylon 6) blend system is investigated. The morphology of 45 wt %/55 wt % polyethylene/Nylon 6 blends with three compatibilizer compositions (5 wt %, 10 wt %, and 15 wt %) are characterized by atomic force microscopic (AFM) phase imaging. The blend with 5 wt % LLDPEgMA demonstrates a Nylon 6 continuous, HDPE dispersed morphology. Increased amount of LLDPEgMA leads to sharp transition in morphology to HDPE continuous, Nylon 6 dispersed morphology. Whereas, increasing HDPEgMA concentration in the same blends results in gradual morphology transition from Nylon 6 continuous to co‐continuous morphology. The mechanical properties, oxygen permeability, and water vapor permeability are measured on the blends which confirm the morphology and indicate that HDPEgMA is a better compatibilizer than LLDPEgMA for the HDPE/Nylon 6 blend system. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 281–290