Organosilicon-functionalized polyolefins,a kind of designable and versatile polymer: From preparation to applications

Functionalization of polyolefins has been a challenging but promising issue since their invention, with the promise of retaining inherent properties and overcoming the low reactivity and poor compatibility. Organosilicons are widely used for polymer modification to improve thermal stability, hydrophobicity, compatibility, and permeability. Since the advent of alkoxysilane-grafted polyethylene in 1960s, organosilicon-functionalized polyolefins (Si-PO) have been extensively prepared, investigated, and developed. The structure of Si-PO is designable due to the flexible chemistry of organosilicons; crosslinked, long chain branched, and star-shaped polyolefins are available after the introduction of alkoxysilanes, chlorosilanes, hyrdosilanes, or alkylsilanes into polyolefins, and generally these polymers are more compatible to fillers than commercial polyolefins due to stronger interaction. In addition, functionalization of polyolefins with stable organosilicon components such as polysiloxane and polysilsesquioxane can improve thermostability, hydrophobicity, gas permeability, and aging resistance; such polyolefins are usually grafted or block polymers. In this review, Si-PO is classified according to the functional organosilicon component, namely alkoxysilane, chlorosilane, hydrosilane, alkylsilane, polysiloxane, and polysilsesquioxane; their preparations are discussed minutely and summarized with manifold examples. Silicon-containing structures impart the unique properties of organosilicons to polyolefins; applications of Si-PO as compatibilizers, processing aids, battery separators, and separating membranes have been widely reported and are discussed here.     

Fused Deposition Modeling of Polyolefins: Challenges and Opportunities

Polyolefins are the largest class of commercially available synthetic polymers that are extensively used in a variety of applications from commodities to engineering owing to their low cost of production, good physico-mechanical properties, light weight, good processability, and recyclability. Compared to conventional molding techniques, fused deposition modeling (FDM)-based 3D printing is a smart manufacturing technology for thermoplastics due to its low cost, ease of production of complex geometrical parts, rapid prototyping, and scalable customization. FDM 3D printing can be an ideal manufacturing technology for polyolefins to manufacture various complex parts. However, FDM 3D-printing of polyolefins is challenged bycritical printing problems like high warpage, dimensional inaccuracies, poor bed adhesion, and poor layer-to-layer adhesion. In this review, a fundamental understanding of polyolefins and their FDM 3D-printing process is established, and the recent progress of FDM 3D printing of polyolefins is summarized. Furthermore, strategies to overcome warpage and to improve mechanical strength of the 3D-printed polyolefins are provided. Finally, future prospectives of FDM 3D-printing of polyolefins are critically discussed to inspire prospective research in this field. It is believed that this review article can be tremendously useful for research work related to FDM of polyolefin-based materials.     

聚烯烃表面改性对润湿性影响的研究进展

表面改性能有效提高聚烯烃的表面润湿性,从而扩大聚烯烃的应用领域。本文介绍了近几年国内外通过等离子体处理、表面光接枝、辐射接枝、化学接枝、等离子体接枝等方法对聚烯烃表面润湿性改性的研究进展。并介绍了各种改性对聚烯烃润湿性的影响。     

Processing highly filled pre‐compounded pellets on single screw extruders

This article discusses, in general terms, several approaches to producing highly filled plastics. Emphasis is on wood flour, with polyolefins as an example. Processing other highly filled polymer and filler choices follows the same logic. Successful approaches include the single screw machine being fed pre‐pelletized material. A large pelletizing twin screw compounder selected for compounding for its output rate isolates the complexities of the compounding step from the profile lines, which have their own unique challenges, such as sizing and cooling the part at good quality and with good tolerances. Operating a few big pelletizing twin screw machines would allow the simple single screw lines of various sizes to run at decent efficiencies on big or small profiles. Since not one machinery approach has monopolized this application to date, some of the major processing and equipment comparisons are discussed. J. VINYL. ADDIT. TECHNOL. 12:83–86, 2006. © 2006 Society of Plastics Engineers     

Flame-retardant thermoplastics. I. Polyethylene–red phosphorus

Red phosphorus is a highly effective flame retardant for polyolefins. The low additive levels of red phosphorus in polyethylene make it an attractive route to nonhalogen flame-retardant systems. The mode of action of the red phosphorus has been investigated. Results indicate that the red phosphorus is effective both in the vapor and condensed phase. In the gas phase, PO species produced from the combustion of red phosphorus quench radical processes. In the condensed phase, the red phosphorus substantially lowers the heat of oxidation and traps radicals. This improved thermal stability results in a decrease in fuel production during burning.     

The technology of halogen-free flame retardant phosphorus additives for polymeric systems

Halogen-free flame retardant additives based on phosphorus function by developing a protective char. A variety of additives are available, ranging from the element itself, in the form of amorphous red phosphorus, to specialty organophosphorus compounds, and examples of their use in a range of thermoplastics are given. Intumescent formulations based on phosphates are especially designed for polyolefins. The behavior of a typical intumescent system is described with respect to flame retardant performance, thermal stability, water sensitivity, and filler compatibility.     

Polyolefin properties for rigid food packaging

Polyolefins are used in many rigid plastic packages that are developed for food applications. Generally, the polyolefins used are selected for a balance of cost, ease of molding, and performance properties in a finished package. In this paper some of the physical and sorption properties of polyolefins that are critical to rigid plastic packages are discussed. Initially, a brief review of the performance requirements of plastic food packages will be presented. This is followed by discussions of specific properties of polyolefins such as impact resistance, adhesion and thermal resistance, and how they may be enhanced by coextrusion. Additionally, the sorption of food components such as flavors into polyolefin walls of packages is discussed. Here, the applicable theoretical considerations for sorption and their value for analyzing experimental data are presented. Finally, specific sorption properties of d-limonene in ethylene-propylene copolymers and their effects on package performance and design are reported and discussed.     

聚烯烃塑料光降解研究进展

介绍了聚烯烃塑料光降解机理及其影响因素、聚烯烃光降解剂和光降解的可调控性,并对聚烯烃光降解的发展趋势进行了展望。聚烯烃塑料的光降解性能与其化学成分、官能团,添加剂及应力等环境条件有关。光降解剂的选择、光降解剂与稳定剂的匹配,是实现聚烯烃塑料降解可调控性的重要技术途径。开发专用光降解剂及相关复合产品,提高聚烯烃塑料光降解率与可调控性,改善环保性且降低成本是该研究领域的主要方向。     

Synthesis, characterisation and decomposition of 1,3-benzene disulfonyl azide; a cross-linking agent for polyolefins

We have studied the thermal decomposition of 1,3-benzenedisulfonyl azide (1,3-BDSA), and verified that sulfonyl nitrenes formed are able to cross-link polyolefins, including PP. The decomposition was studied with DSC, TGA, and the GC–MS analysis of gaseous products. Both the decomposition of pure 1,3-BDSA and 1,3-BDSA dissolved in a polyolefin were studied. Decomposition occurs by loss of nitrogen giving sulfonyl nitrenes. In the polyolefin nitrenes cross-links the carbon chains by C–H insertion. Cross-linking of PP was verified with SEC. SEC showed no signs of decomposition of PP. Decomposition in the polyolefin was a first order reaction with a half-life of 25.7 s at 200 °C. Hence, 1,3-BDSA is suited for processing with polyolefins. Decomposition of pure 1,3-BDSA is more complicated with unwanted products such as SO₂ and benzene being formed, thereby emphasising the need for good blending when used in polyolefins.     

Applied Dielectric Spectroscopy of Polymeric Composites

In this article a theoretical background for understanding dielectric phenomena in heterogeneous polymeric composites is presented, and the application of these principles to practical problems is illustrated by experimental examples. First a short overview of the existing theoretical mixing formulae is given, the differences in these approaches are discussed, and the areas of application are indicated. Conditions for the appearance of an interfacial relaxation process are delineated; limitations of the theories are given. Experimental examples include immiscible polymer blends, mineral-filled polyolefins, thermoset composites, and conductive composites. In the first example, AC dielectric spectroscopy is used to monitor the phase separation process and to evaluate interactions between the separated phases. In the second example, the effect of filler permittivity, volume fraction, and surface treatment is discussed with respect to the AC and DC dielectric properties. It is shown that in mineral-filled polyolefins, water adsorbed at the matrix-filler interface plays an important role. In the third example, the effect of filler purity (and conductivity) on the dielectric properties is demonstrated. Nonelectrical-grade glass powder causes a strong interfacial polarization and electrode polarization in an unsaturated polyester resin, whereas electrical-grade glass fiber reinforcement leads to minor property changes. In the final example, the effects of processing conditions on the AC conductivity and permittivity of conductive composites is discussed. Extensive shear and orientation cause a shift of the percolation threshold, thus reducing the conductivity. Thus it is shown that dielectric methods can be used to investigate problems in processing technology.     

Review of life cycle assessment on polyolefins and related materials

Abstract

Life cycle assessment (LCA) is a sustainability measurement tool that identifies the environmental impacts of a product. The uniqueness of the LCA lies in its methodology, which aggregates all environmental burdens throughout the product’s life cycle, providing many variables for optimisation of the product (or process). Having occupied a major market share, the environmental impacts associated with the manufacturing and disposal of polyolefins are quite high. The main theme of this paper is to review the reported LCA studies on polyethylenes and polypropylenes including recycled plastics, biobased materials, which are competing with polyolefins, and polyolefin composites. The widely claimed green product ‘recycled plastic’ is analysed in detail from an LCA perspective, and key points, which determine its sustainability, are discussed. The environmental impacts associated with the manufacturing of polyolefins and their bioalternatives are highlighted. The few published studies of polyolefin composites on different applications are also discussed.     

Ultra‐high‐molecular‐weight functional siloxane additives in polymers. Effects on processing and properties

Two new types of solid siloxane additives for plastics are described which give improved benefits compared to previous silicone additives. Ultra‐high‐molecular‐weight (UHMW) siloxanes are used in the new additives; traditional silicone plastic additives have used much lower molecular‐weight silicones. The siloxane is converted into solid forms, either masterbatch pellets or powders, that are easy to feed, or mix, into plastics during compounding, extrusion, or injection molding. Ultra‐high‐molecular‐weight siloxanes can be compounded into masterbatch pellets at higher siloxane concentrations than previously possible, e. g., up to 50%. They impart improved processing and release, lower coefficient of friction, and broader performance latitude compared to conventional lower‐molecular‐weight silicones. These benefits can be delivered at reduced siloxane levels with increased concentration at the surface interface with a new functionalized UHMW siloxane which provides unique surface segregation characteristics. Ultra‐high‐molecular‐weight siloxanes have been formulated into powders that can also act as processing aids and mechanical property modifiers for highly filled polymers such as fire‐retardant systems. This paper uses polyolefins as a model. However, many of the effects shown in polyolefins have also been seen in other resin systems.     

Landwirtschaftliche Untersuchungen mit ”︁New Crops„ in den USA

Agronomic Research with New Crops in the USA In the US the term: “new crop” is used for specialty crops with mostly industrial application. The following groups of plants are discussed: starch crops (Amaranth, Pearl Millet), oil crops (Crambe, Cuphea, Jojoba, Lesquerella, Meadowfoam), fibre crops (kenaf) and gum producing crops (Guar, Guayule). Reasons for developing new crops are: overproduction by conventional crops, self sufficiency of the US economy, and means for soil-and water conservation such as preventing erosion and having more efficient water use in arid land field crop production. In agricultural production new crops often have problems that are not easy to overcome and which partly prevent their acceptance by agriculture. Such problems are: characteristics of the un-domesticated plant that prevent large scale production; a long term commitment to obtain better plant types by means of plant breeding, as well as along lasting financial support; little or no adaption to the climate; problems with the processing and marketing of new products.     

Antioxidants and stabilizers LXIX. Effect of products of the oxidation transformation of 4,4′-thio-bis(2-methyl-6-tert-butylphenol) on the oxidation of tetralin

The effect of products of the oxidation transformation of an antioxidant for polyolefins, 4,4′-thio-bis(2-methyl-6-tert-butylphenol), on the oxidation of tetralin initiated with 2,2′-azobis(isobutyronitrile) at 60°C, and with tetralylhydroperoxide at 120°C was investigated. Nearly all investigated sulphur-containing compounds possessed antioxidative activity. Their formation under conditions which inhibit the oxidation of polyolefins and the comparison of their effectivity observed for various modes of the initiation of oxidation show that there exist two mechanisms by which antioxidants containing sulphidic sulphur in their molecule may be operative and indicate which transformation products of the originally present antioxidant take part in the autoxidation. The antioxidative activity of compounds of the thiobisphenol type is lost only after complete transformation into products of a quinoid type and into sulphon.     

聚烯烃的功能化

叙述了聚烯烃通过共聚、接枝、高分子反应、低分子量化、复合化、交联化以及新的催化技术开发所得各种功能性聚烯烃的特点及其应用。     

Polymer modulus and morphology: The tensile properties of polyethylene

The general properties of a novel process for producing high modulus polyolefins are discussed. The technique is an extrusion drawing involving a crystal-crystal transformation. The principal tests have been made on polyethylene and the guidelines have been established for extending the technique to other polyolefins. The characterization of such materials is extensively discussed, particularly in the light of the concept of continuous crystals.     

Liquid crystal polymer-based blends: “Universal grade” polymers?

Polymeric materials can be easily processed with different processing operations thanks to suitable rheological properties. Melt flow index, or grade, which is a measure of the fluidity of the polymers, is the most commonly parameter used to characterize the polymers from the point of view of their melt viscosity. Injection molding requires high grade materials, whereas low grade values are best suited for extrusion. Of course, it would be no doubt of interest if single “universal grade” materials could be used for all processing operations. In this paper it is demonstrated that the blends of low grade polymers with small amounts of liquid crystal polymers can be conveniently used for all processing operations. Mechanical and thermal properties of the polymer matrix are in general retained or, in some cases, improved.     

Formulation and processing of virgin and recycled polyolefin/oil blends for the development of lubricating greases

This work has been focused on the development of polyolefins/oil blends potentially suitable as lubricating greases by studying the effect that some thermo-mechanical processing variables exert on their rheological properties and microstructure. Polyolefin/oil blends have been prepared by dispersing recycled and virgin polyolefins such as high-density polyethylenes (HDPEs) and polypropylenes (PPs) in mineral lubricating oil. Linear viscoelasticity functions have been significantly influenced by processing conditions. The nature of polymers used, specially the content of HDPE, has been found to modify the microstructure of blends yielding lower mechanical stability but, on the other hand, higher values of linear viscoelastic functions.     

Accelerating the degradation of polyolefins through additives and blending

Polyolefins are popular because of their low price, useful properties, broad supply chains, and mature processing facilities, but they do not easily degrade in the natural environment, and hence, the development of degradable polyolefins has attracted increasing interest. Oxidative degradation and blending with natural polymers can accelerate the degradation of polyolefins in natural environments. In this article, we review the research and developments in the acceleration of the degradation of polyolefin blends and composites, including both the fundamental science, such as the degradation mechanisms and characterizations, and application techniques, such as the processing conditions and formulations. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40750.     

An overview of degradable and biodegradable polyolefins

The use of engineering plastics, especially polyolefins has increased significantly in recent decades largely due to their low cost, good mechanical properties and light weight. However, this increase in usage has also created many challenges associated with disposal and their impact on the environment. This is because polyolefins do not easily degrade in the natural environment and hence the need for degradable polyolefins has become a major topic of research. Degradable polyolefins are designed to retain functionality as a commodity plastic for the required service life but degrade to non-toxic end products in a disposal environment. They are typically designed to oxo-degrade while undergoing changes in chemical structure as a result of oxidation in air, thus causing the breakdown of the molecules into small fragments that are then bioassimilated. This article presents (i) a comprehensive review of the chemistry of additives for the degradation of polyolefins, (ii) a patent and scientific literature summary of technologies including commercially available systems, (iii) the mechanisms of degradation and biodegradation, (iv) testing methods and (v) toxicity.