Homogeneously Dispersed Poly(propylene)/SiO2 Nanocomposites with Unprecedented Transparency

Summary: Physico‐chemical interactions between hydrophobic polyolefin materials and hydrophilic inorganic nanoparticles such as surface‐hydroxylated SiO₂ have not been well understood so far. In this study, the effects of particle size and content of SiO₂ nanoparticles on isothermal growth rate of PP spherulites in various PP/SiO₂ nanocomposites were investigated by polarized optical microscopy. It was unexpected to find that hydrophilic SiO₂ nanoparticles can be homogeneously dispersed in a PP matrix. Spherulite growth rates of PP in PP/SiO₂ nanocomposites decrease significantly with increasing SiO₂ content and decreasing particle size. Most interestingly, the spherulite growth rate was zero for PP/16 nm‐SiO₂ nanocomposites with SiO₂ content above 2.5 wt.‐% resulting in a highly transparent film.

Photographs of 200 µm‐thick PP and PP/16 nm‐SiO₂ (5 wt.‐%) sheets in front of a graphic pattern.     

Thermal Degradation and Flammability Properties of Poly(propylene)/Carbon Nanotube Composites

Nanocomposites based on poly(propylene) and multi‐wall carbon nanotubes (up to 2 vol.‐%) were melt blended, yielding a good dispersion of nanotubes without using any organic treatment or additional additives. Carbon nanotubes are found to significantly enhance the thermal stability of poly(propylene) in nitrogen at high temperatures. Specifically, the nanotube additive greatly reduced the heat release rate of poly(propylene). They are found to be at least as effective a flame‐retardant as clay/poly(propylene) nanocomposites.     

Polymorphism and Thermal Behaviour of Syndiotactic Poly(propylene)/Carbon Nanotube Composites

Summary: Nanocomposite materials were obtained by blending multi‐wall carbon nanotubes (CN), obtained by acetylene catalytic chemical vapour deposition (CVD) on Co/Fe‐modified NaY zeolite, with syndiotactic poly(propylene) (sPP). The nanotubes, well dispersed in the polymer matrix, favour the crystallization of the sPP helical chains and significantly improve the sPP thermal stability either in nitrogen or in air. The morphology of the sPP affects the behaviour of the sPP degradation in air.

Thermogravimetric analysis in air of pure sPP and the nanocomposite material.     

Thermal Degradation and Kinetics of Poly(3-hydroxybutyrate)/Organoclay Nanocomposites

Poly(3-hydroxybutyrate)/Cloisite30B (PHB/30B) nanocomposites were prepared by solution-intercalation method. The influence of 30B content on the thermal stability of PHB was investigated. With the addition of 3 wt. % of 30B the highest thermal stability of PHB was achieved. The kinetic analysis of the non-isothermal degradation was performed using the isoconversional Friedman method and invariant kinetic parameters method.     

Isotactic Poly(propylene)/Monoalkylimidazolium‐Modified Montmorillonite Nanocomposites: Preparation by Intercalative Polymerization and Thermal Stability Study

Summary: Poly(propylene)/monoalkylimidazolium‐modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl₄/MgCl₂/MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability.

X‐ray diffraction patterns of PP/IMMT (MMT = 2.2 wt.‐%) nanocomposite before and after processing.     

Formation and Detection of Clay Network Structure in Poly(propylene)/Layered Silicate Nanocomposites

Summary: The study of the structure and the rheological properties of poly(propylene) (PP)/montmorillonite (MMT)/maleinated PP (MAPP) composites strongly suggests that a silicate network may form under certain conditions. Network formation could not be proven unambiguously with the usual techniques, i.e., with TEM and by plotting the frequency dependence of viscoelastic properties. Cole‐Cole plots detect the network very sensitively. A certain number of silicate layers are needed to create a house‐of‐cards structure. A threshold concentration of MAPP exists in the investigated system, which depends on the silicate content.

Cole‐Cole representation of the viscoelastic properties of PP/OMMT/MAPP nanocomposites.     

Polyethylene and Poly(propylene)/Clay Nanocomposites

Polyethylene and polypropylene nanocomposites were investigated with focus on mechanical and barrier properties. Structure was observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Four types of nano-filler were used: Nanofil 5, 8, 9 and 3000. In case of polyethylene nanocomposites the dispersion and intercalation was to low extent. Mechanical and barrier properties were worse compared to pure PE. In case of polypropylene with Nanofil 5, 9 and 3000 tensile strength was better compared to pure PP. Also PP with Nanofil 9 and 3000 had better barrier properties than pure PP for both O₂ and CO₂. This was explained by better intercalation and dispersion of the filler documented by XRD measurement and TEM observation.     

氯化聚丙撑碳酸酯增容聚丙撑碳酸酯/秸秆粉复合材料的制备及性能

聚丙撑碳酸酯(PPC)是一种新型热塑性生物降解材料,但其热性能及力学性能较差,应用受到限制。以秸秆粉这种农作物副产品作为增强体改性PPC,既可以提高PPC的力学性能同时又可开发利用秸秆资源。氯化聚丙撑碳酸酯(CPPC)是聚丙撑碳酸酯(PPC)经过氯化得到的,对天然纤维表面具有良好的浸润性和粘结性。本文以CPPC为增容剂,通过熔融共混法制备了PPC/秸秆粉复合材料。采用扫描电子显微镜(SEM)、拉伸实验、动态力学性能测试(DMA)及转矩流变仪对复合材料的结构及性能进行了表征,重点考察了CPPC的添加量对复合材料力学和流变性能的影响。结果表明,当CPPC质量分数为1.8%时,可使添加质量分数为30%秸秆粉的PPC复合材料拉伸强度提高38%,模量提高30%。同时,CPPC的引入使复合材料的粘度下降,改善了PPC/秸秆粉复合材料的加工性能。因此,作为增容剂的CPPC为制备高性能PPC/天然纤维复合材料提供了新的解决办法。     

Thermal,Mechanical and Morphological Behavior of Poly(propylene)/Wood Flour Composites

The comparative studies on the thermal, mechanical and morphological behavior of compression molded poly(propylene) (PP)/wood flour (WF) composites were performed using wood flours (WFs) of different origins. The comparison has been made on the basis of results obtained from thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile testing. It has been demonstrated that an addition of 5 wt.-% of maleic anhydride grafted polypropylene (PP-g-MA) has a significant effect on the morphological and thermomechanical behavior of the composites. Although, microscopic examinations revealed no significant differences in the morphology of the compatibilized composites, a remarkable improvement of thermal degradation behavior was observed. From the view point of mechanical properties, the composites with high amount of filler (60 wt.-%) showed similar behavior irrespective of the origin of wood flour.     

Poly(methyl methacrylate)/Methacryl-POSS Nanocomposites with Excellent Thermal Properties

Poly(methyl methacrylate) (PMMA) nanocomposites containing (methacryloxy)propyl polyhedral oligomeric silsesquioxane (methacryl‐POSS) were prepared by bulk‐polymerization process. The structures of the products were characterized by FTIR, solid‐state NMR, TEM, XRD, DSC, TGA, XPS and UV‐Vis spectra. The hybrid materials were found to be largely homogeneous. DSC and TGA results indicate that the thermal properties of PMMA nanocomposites are significantly improved. The glass transition temperature (T_g) and thermal decomposition temperature (T_dec) of the nanocomposites increased by 58 and 110°C, respectively. The bulk hybrid material maintains excellent optical transparency in visible region.     

High‐Performance Exfoliated Poly(propylene)/Clay Nanocomposites by In Situ Polymerization with a Novel Z–N/Clay Compound Catalyst

Highly exfoliated poly(propylene) (PP)/clay nanocomposites with obvious improvements in both the tensile strength and toughness have been prepared by a novel TiCl₄/MgCl₂/imidazolium‐modified montmorillonite (IOHMMT) compound catalysts. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with a high isotacticity and molecular weight, but also to a highly exfoliated structure even at high clay content levels (as high as 19 wt.‐%).

     

The Role of Oxidation in the Migration Mechanism of Layered Silicate in Poly(propylene) Nanocomposites

Summary: Evidence of clay migration from the core to the surface of poly(propylene)/montmorillonite nanocomposites is provided. A three‐ to fivefold increase in the clay concentration of the surface is obtained during isothermal heating in oxidative atmosphere. The mechanism of migration is investigated by means of attenuated total reflectance Fourier transform infrared spectrometry. It is shown that oxygen plays a fundamental role in the migration mechanism.

ρ_Si versus c for the annealed samples.     

Thermal Properties of Poly(L-lactide)/Calcium Carbonate Nanocomposites

Summary: Thermal properties of nanocomposites prepared of poly(L-lactide) (PLLA) and CaCO₃ applying differential scanning (DSC) calorimetry and thermogravimetry (TG) were studied. Nanocomposites were prepared by extrusion process at 170 °C. DSC measurements show that CaCO₃ has no influence on glass transition and melting point of PLLA but lowers its cold crystallization temperature. There is no difference in glass transition temperature of PLLA before and after extrusion. High temperature thermal stability of the PLLA in the composites is poorer than neat PLLA. Kinetic parameters also indicate greater reactivity of the system upon CaCO₃ addition.     

水辅助加工法制备聚丙撑碳酸酯/淀粉共混物

分别采用普通熔融共混法和水辅助加工法,制备了具有不同共混形态的聚丙撑碳酸酯(PPC)/淀粉共混物,并研究了淀粉分散形态对共混物的玻璃化转变温度(Tg)、流变以及力学性能的影响。研究结果表明,采用普通熔融共混法时,淀粉未发生糊化,并以原颗粒状分散于基体中;而采用水辅助加工法时,淀粉发生糊化,并在挤出过程中原位形成纤维结构。当淀粉以纤维形式分散于PPC基体中时,其与PPC间的界面接触面积显著增加,二者的相互作用增强,PPC/淀粉共混物的Tg、储能模量以及复合黏度显著提高。力学性能测试结果表明,当淀粉质量分数为30%,采用水辅助加工法制备的PPC/淀粉共混物的拉伸模量相比于纯PPC提高了67.7%。     

聚丙撑碳酸酯的辐射效应

研究了室温条件下聚丙撑碳酸酯(PPC)在钴-60和电子加速器辐照过程中的响应行为。结果表明,聚丙撑碳酸酯是一种辐射裂解型聚合物,其分子量随着辐射剂量的增加而减小。1mm厚PPC片材在室温和N2气保护条件下,其裂解G值为Gs,γ-ray=10.81;Gs,EB=4.9。不同的裂解G值表明,O2气在聚丙撑碳酸酯的辐射裂解过程中有重要影响。红外光谱研究表明,辐射后聚丙撑碳酸酯在3474cm-1处的峰宽峰高增加,表明其裂解后端—OH基增加。由于裂解作用,辐射后聚丙撑碳酸酯的抗张强度和断裂伸长率均下降。在通常的辐射消毒剂量范围内(25~50kGy),PPC的保留抗张强度大于23MPa,断裂伸长率大于4%,裂解后试样的力学性能依然能够满足实际应用需要,因此PPC可以经受辐射消毒。     

Thermophysical Properties of Poly(propylene)-based Composite Polymer

The thermal diffusivity and the thermal conductivity of polypropylene-based composite polymer were simultaneously measured with a temperature wave analysis method. We can measure the thermal properties under cooling process which are important to consider the polymer processing. The effect of filler in the composite was analyzed by thermal diffusivity and thermal conductivity as a function of temperature. The thermal conductivity of particle dispersed composite was confirmed as a reasonable value and was explained with a series model. This revised version was published online in July 2006 with corrections to the Cover Date.     

聚乳酸/蒙脱土纳米复合材料的结构和热性能

聚乳酸/蒙脱土纳米复合材料的结构和热性能;聚乳酸;蒙脱土;纳米复合材料;插层     

New Poly(propylene glycol)‐ and Poly(ethylene glycol)‐Based Polymer Gelators with L‐Lysine

Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.

Structures of the polymer gelators synthesized here.     

Improving the Thermal Behavior and Flame-Retardant Properties of Poly(o-anisidine)/MMT Nanocomposites Incorporated with Poly(o-anisidine) and Clay Nanofiller

The synthesis of MMT and poly(o-anisidine) (MMT/POA) clay nanocomposites was carried out by using the chemical oxidative polymerization of POA and MMT clay with POA, respectively. By maintaining the constant concentration of POA, different percentage loads of MMT clay were used to determine the effect of MMT clay on the properties of POA. The interaction between POA and MMT clay was investigated by FTIR spectroscopy, and, to reveal the complete compactness and homogeneous distribution of MMT clay in POA, were assessed by using scanning-electron-microscope (SEM) analysis. The UV–visible spectrum was studied for the optical and absorbance properties of MMT/POA ceramic nanocomposites. Furthermore, the horizontal burning test (HBT) demonstrated that clay nanofillers inhibit POA combustion.