Tailoring of Three‐Phase Crystalline Systems in Isotactic Poly(propylene)

Summary: A novel method for the tailoring of unique three‐phase crystalline systems in isotactic poly(propylene) has been proven. It is based on a synergistic application of a specific β‐nucleating agent and high pressure during crystallization. The formation of a γ phase was supported by elevated pressure and high temperature during crystallization; under these conditions the growth of both β and α phases was significantly suppressed. Nevertheless, during the course of crystallization at lower pressure and/or lower temperatures, strong β‐nucleation efficiency favored the formation of a β phase.

     

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.     

Shear‐Controlled Micro/Nanometer‐Scaled Super‐Hydrophobic Surfaces with Tunable Sliding Angles from Single Component Isotactic Poly(propylene)

Summary: With the proper selection of shear and thermal conditions, super‐hydrophobic polymeric surfaces (contact angle > 150°) with tunable sliding angles (from less than 1° to higher than 90°) can be prepared from pure isotactic poly(propylene) (iPP) without any further modification with low‐surface‐energy components under ambient atmosphere. The formed surfaces have naturally good thermal properties, chemical and moisture resistance, low density, and potentially low manufacturing cost.

SEM images of formed super‐hydrophobic surfaces and related two extreme sliding angles (contact angles of these surfaces are higher than 150°).     

Conductive Composites Based on Metallocene Isotactic Poly(propylene): Preparation and Properties

Summary: The research deals with the preparation and the further comprehensive characterization of metallocene polypropylene-based composite materials by incorporation of carbon black nanoparticles. Composites containing up to 10 wt% of carbon black were prepared by direct melt mixing in a single screw extruder Brabender Extrusiograph type 30/25D with attached static mixer at melt temperature of 200 °C and a screw speed of 30 rpm, according to a two-step process. Some composites were treated with 3 wt% maleic anhydride grafted polypropylene (MAH-PP). The rheological behaviour of the miPP nanocomposites was determined by cone/plate rheological measurements at 180 °C. The composites were characterized by SEM for morphological details and uniaxial stress-strain measurements for determining the mechanical parameters. Electric conductivity of injection molded plates from these composites was investigated. The different miPPs studied are ranked in an ascending order according to their increasing molecular weight concerning the magnitude of their rheological parameters. The maleic anhydride compatibilizer leads to lower viscosity values even at high shear gradients and to better homogenization of the nanofiller in the polymer matrix. The processing conditions, carbon black concentration and viscosity of the virgin polymer have an impact on the final conductivity of the miPP/carbon black composites.     

Nucleating Effect and Dynamic Crystallization of a Poly(propylene)/Talc System

The addition of nucleating agents to semicrystalline polymersis largely used in the processing industry of plastic materials to improve some properties of polymers as well as for economical and technological reasons. In this work, the influence of talc concentration on the nucleation efficiency of poly(propylene) (PP), as well as on the non-isothermal kinetics of the crystallization of that system were determined by differential scanning calorimetry (DSC). The nucleating efficiency was determined by Fillon's method, and the dynamic nucleation by Ozawa's method at cooing rates of 2, 5 and 10°C min^–1. The results show that both the degree of crystallinity and the crystallization temperature increase with the filler content and decrease at higher cooling rates and that Ozawa's (n,) exponent and the nucleation efficiency increase with temperature and filler content. It was also shown that the nucleating efficiency of talc in poly(propylene) is comparable to the best heterogeneous nucleating agents available. This revised version was published online in August 2006 with corrections to the Cover Date.     

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。     

Large Plastic Deformation of Isotactic Poly(propylene) (iPP) Evaluated by WAXD Techniques

Summary: Commercial isotactic poly(propylene) (iPP), obtained in bars, was annealed and submitted to different levels of plastic deformation by uniaxial plane compression using a special device which permits well controlled temperature and strain rate. The evolution of the microstructure was followed at different degrees of deformation by wide angle x-ray diffraction (WAXD) techniques. The spherulite fragmentation process, lamellar orientation and destruction of the crystallites is argued, according to collected analytical data in the flow direction (FD), the loading direction (LD) and the lateral or constrain direction (CD). The evaluation of the WAXD patterns in terms of diffraction line position, intensity and width, permits to affirm that, while the large plastic deformation occurs, the crystalline net suffers anisotropic deformation, the crystallites become preferentially oriented along the flow direction and the crystalline phase diminish in amount indicating lesser and smaller crystallites. The gradual lamellae fragmentation occurs, starting with apparent crystalline size of approximately 30 nm for the non-deformed material and gradually decreasing to approximately 15 nm for the 70% deformed one.     

以聚丙二醇二苯甲酸酯为给电子体的丙烯聚合催化剂

 采用聚丙二醇二苯甲酸酯(PPGDB)为内给电子体制备了一种新的丙烯聚合催化剂MgCl2/PPGDB/TiCl4. 该催化剂用于丙烯聚合时,除了具有与以邻苯二甲酸二异丁酯为给电子体的催化剂相当的活性和立体定向性外,其特点在于所得产物的分子量分布较宽(Mw/Mn＞8.0). 采用红外光谱研究了催化剂中PPGDB与MgCl2的作用机制,结果表明PPGDB中的酯官能团和醚官能团可同时与MgCl2配位. 这种双官能团的配位作用是所得聚合物分子量分布较宽的主要原因.     

Isothermal Crystallization of Isotactic Poly(propylene) Studied by Superfast Calorimetry

The isothermal crystallization behavior and the structure and morphology of isotactic poly(propylene) (iPP) and iPP/hydrogenated hydrocarbon resin (HR) 90/10 blend were analyzed. To cover the entire temperature range, isothermal crystallizations were studied using superfast calorimetry at a high cooling rate in the range 0 to 110 °C, and by conventional DSC at a low cooling rate in the range 120 to 140 °C. Structural and morphological changes due to the different thermal treatments were also analyzed. The complete crystallization curve ranging from T_g to T_m showed bimodal crystallization behaviors for both iPP and iPP/HR 90/10 blend. This result is explained by taking into consideration the polymorph properties of iPP. It is in fact assumed that the curve from T_g to 60 °C referred mainly to the crystallization kinetics of the iPP mesomorphic form by homogeneous nucleation, whereas the curve from 60 °C to T_m mainly represented the crystallization kinetic curve for the monoclinic α form by heterogeneous nucleation. This hypothesis is confirmed by the analysis of the structures obtained using wide angle X‐ray experiments. Moreover, the addition of HR to iPP causes a drastic reduction in the crystallization rate of iPP in both regions due to the diluent effect of the miscible resin.

     

Poly(propylene carbonate)/poly(3‐hydroxybutyrate)‐based bionanocomposites reinforced with cellulose nanocrystal for potential application as a packaging material

Poly(propylene carbonate) (PPC) is an aliphatic polycarbonate synthesized from carbon dioxide and propylene oxide. Poly(3‐hydroxybutyrate) (PHB) is a type of thermoplastic polyester produced by biological fermentation. The blending of PHB with PPC can effectively enhance the mechanical properties and barrier properties of PPC. Bionanocomposites of PPC/PHB enhanced by cellulose nanocrystal (CNC) are prepared via a two‐step process using polyethylene glycol as a carrier. Results show that the oxygen barrier properties of the composites increased with the increase of the CNC content. When the CNC content is 1 wt%, the oxygen barrier performance increases nearly 18 times. The assumed model can predict the barrier performance of composites with the combined influence of morphology and CNC distribution. This will make PPC/PHB/CNC nanocomposites a very promising degradable material for food packaging application.     

Synthesis of Stereoblock Elastomeric Poly(propylene)s Using a (2‐PhInd)2ZrCl2 Metallocene Catalyst in the Presence of Co‐Catalyst Mixtures: Study of Activity and Molecular Weight

The effect of adding various aluminum alkyls (R = Et, i‐Bu) on the polymerization of propylene is studied using a (2‐PhInd)₂ZrCl₂ pre‐catalyst. A mild deactivating effect is found upon addition of TIBA, whereas TEA shows a sharp deactivating effect. Increasing amounts of AlR₃ results in a significant activity increase for TIBA, but an activity plateau for TEA. AlR₃ imposes remarkably different effects on the molecular weight and stereochemical microstructure of polymers. As the TIBA concentration increases, $\overline {M} _{{\rm v}} $ increases at first, growing from 49 000 to 72 000, but subsequently drops to 40 000. For TEA, $\overline {M} _{{\rm v}} $ decreases sharply, plummeting from 49 000 to 17 000. Both TIBA and TEA increase the mmmm pentad content from 7.9 to 23.5% and 17.6%, respectively.

     

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%。     

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.‐%).

     

Modifications of the active sites distribution in the Ziegler‐Natta polymerization of propylene using Lewis acids

Heterogeneous Ziegler‐Natta precatalysts (with phthalate as internal donor) were modified by treatments with various Lewis acids (MCl_n with M = Ga, Sn, Si, and Sb and n = 3, 4, or 5) before their use in the polymerization of propylene. If performed on previously “detitanated” precatalysts, treatments with SnCl₄ and SiCl₄ lead to a slight activation but especially to an increase of the tacticity whereas GaCl₃ and SbCl₅ treatments deactivate the catalyst. The modification method applied to conventional unmodified precatalysts gave similar trends. A significant increase of tacticity (and/or of T_m) and a narrowing of the molecular weight distribution were observed in the case of SnCl₄ and SiCl₄ treatments. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2631–2635, 2010     

Poly(propylene glycol)‐based ammonium ionenes as segmented ion‐containing block copolymers

The synthesis and characterization of series of segmented poly(propylene glycol) (PPG)‐based ammonium ionenes is described. Bromine end‐capped oligomers were successfully synthesized using the reaction of 6‐bromohexanoyl chloride with 1000, 2000, and 4000 g/mol PPGs. ¹H NMR spectroscopy, titration studies, and matrix‐assisted laser desorption ionization‐time of flight (MALDI‐TOF) mass spectrometry revealed the difunctionality of the oligomers. First, a series of PPG‐based ammonium ionenes was synthesized from bromine end‐capped PPG oligomers and N,N,N′,N′‐tetramethyl‐1,6‐hexanediamine. For this series, a single glass transition temperature (T_g) of approximately ?66 °C was observed through differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA) showed the onset of flow ranged from 20 to 80 °C. In addition, a series of PPG‐based ammonium ionenes containing 1,12‐dibromododecane was synthesized to increase the aliphatic hard segment (HS) content and enhance the mechanical properties of the resulting materials. For these, two T_g's were observed using DMA; DMA also showed the onset of flow of ionenes containing higher HS content (33 wt %) occurred in the range of 100–140 °C. Tensile analysis for these ionenes demonstrated an average tensile strength at break ranging from 0.2 to 2.4 MPa. Small angle X‐ray scattering (SAXS) profiles for these ionenes showed that Bragg distances increase linearly with the molecular weight of PPG soft segment. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4159–4167, 2010     

偶联剂对聚氯乙烯－聚丙撑碳酸酯共混体系力学性能的影响

偶联剂对聚氯乙烯－聚丙撑碳酸酯共混体系力学性能的影响王胜杰，黄玉惠，丛广民（中国科学院广州化学研究所广州５１０６５０）关键词聚氯乙烯，聚丙撑碳酸酯，偶联剂，丁腈胶，过氧化苯甲酰，共混聚氯乙烯（ＰＶＣ）是用量巨大的通用塑料，其软性制品需用大量的增塑剂，...     

N‐Heterocyclic Olefins as Organocatalysts for Polymerization: Preparation of Well‐Defined Poly(propylene oxide)

The metal‐free polymerization of propylene oxide (PO) using a special class of alkene—N‐heterocyclic olefins (NHOs)—as catalysts is described. Manipulation of the chemical structure of the NHO organocatalyst allows for the preparation of the poly(propylene oxide) in high yields with high turnover (TON>2000), which renders this the most active metal‐free system for the polymerization of PO reported to date. The resulting polyether displays predictable end groups, molar mass, and a low dispersity (?_M<1.09). NHOs with an unsaturated backbone are essential for polymerization to occur, while substitution at the exocyclic carbon atom has an impact on the reaction pathway and ensures the suppression of side reactions.