The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Research of Screw Configurations on Dispersing Nano-Particles in Polymer
Melt compounding is one of the methods in dispersing nano-particles in polymer. In this paper, 12 different screw configurations in co-rotating intermeshing twin-screw extruder for preparing nano-particles/polymer composite (by Melt compound processing) were studied. The physical property test and TEM of extrudates were carried out. The results show that VCR which characterized as having highly tensile effects, are much more preferred in the melting zone of the intermeshing twin-screw rather than in the melt conveying zone, as well as the forward kneading block which have remarkable shearing performance. While the reversed kneading block and NIMPE elements being set in melt conveying zone of the twin-screw will have much more advantage over those in the melting zone.
The Effect of Sorbitol Based Nucleating Agents on Tear Strength in Polyethylene Film
Ziegler-Natta (Z-N) based polyethylenes have been generally known to display higher tear strengths in blown film applications, especially in the machine direction, than their metallocene-based counterparts. Z-N films display an oriented lamellar morphology, while the metallocene film morphology is more spherulitic and hence less oriented. The objective of this work, in part, was to try to duplicate the Z-N film morphology in metallocene films by adding nucleating agents that orient during film blowing. It was shown that addition of sorbitol based nucleating agent to metallocene based films gives rise to increased lamellar orientation and hence improved tear strength since the nucleant forms an oriented gel in the melt.
Optimization Model Based on a Heuristical Method for Barrier Films Design
This paper presents an optimization model based on a heuristical method to support the design of plastic barrier packaging for food and beverage. The goal is to minimize the cost of a multilayer film structures satisfying the end product requirements. The technical conditions for every layer and its polymer material (support, tie and barrier materials) are considered.The algorithm of this optimization model was evaluated by means of numerical experiments considering accuracy and precision for obtaining the target results. The oxygen and water vapor barriers for several multilayer films up to seven layers were measured and compared with the results of the model.
Polypropylene - Polyethylene Multilayer Films
In this study, we investigated the properties and some structural parameters of multilayer and blends films of polypropylene (PP) and polyethylene (PE) obtained from the extrusion blowing process. Three PP’s (a homopolymer, copolymer and a high melt strength PP compound) and one LLDPE were used. In general, tensile strength and modulus were larger in MD than TD and tear resistance higher in TD than MD, with some differences between the different sets of polymers. The modulus and strength were lower for the films made from the blend. Haze depended strongly on the PP used and whether it was pure, multilayer or blend, with the lowest haze obtained for the multilayer films made of copolymer PP and the highest with the multilayer films with homopolymer PP. Other properties such as oxygen permeability will also be discussed. The oriented crystalline structure of the PP’s was such that b-axis oriented in ND-TD plane and c-axis oriented in MD. PE crystalline morphologies at the interface were different for the different PP’s multilayer films and blends. PP had similar crystalline orientation for blends and co-extruded films but not PE.
Optimise Organoclay Exfoliation in Polymer Nanocomposites by Customising the Extrusion Temperature Gradient
This is a communication article describing a novel and simple approach to optimise the exfoliation and dispersion of organoclay layered-silicate in the extrusion processing of polymer nanocomposites. A range of HDPE nanocomposites were processed by configuring the extrusion temperature gradient in a single-screw compounder. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of organoclay exfoliation, which is directly associated with the various property improvement in nanocomposites, was influenced by the extrusion temperature gradient. These nanocomposites exhibited significant difference in their rheological flow characteristic and mechanical properties, owing to the difference in the resultant organoclay structures. Regardless of the level of organoclay exfoliation, all the nanocomposites exhibited better processability and improved mechanical properties compared to the virgin HDPE. The elongation at break of all the nanocomposites was considerably greater than the virgin HDPE despite recording an increase in crystallinity.
Comparative Study between Metallocene Polyolefin Blends Modified by Beta-Irradiation and a Silane Crosslinking Process
Three binary groups of metallocene blends of ethylene- 1-Octene copolymer (80 and 50 weight %) with two metallocene ethylene-1-Octene copolymers of different crystalline density and a metallocene EPDM were made in a co-rotating twin-screw extruder. The first group corresponds to blends without chemical modification. In the second group the dispersed phase was grafted with vinyl-triethoxy silane by means of a reactive extrusion process (SIOPLAS). The blends of the third group were crosslinked with Beta-Radiation at 200 KGy as final dose. The gel content of the crosslinked blends showed higher values for those blends crosslinked by Beta- Irradiation than SIOPLAS process. DSC using a heat treatment known as Successive Self- Nucleation/Annealing (SSA) and DMA techniques were used to analyze the effect of the comonomer content on the crystalline morphology of the crosslinked materials. Important changes in crystalline morphology of the blends due to the crosslinking process were observed.
Structure and Oxygen Barrier of Polyhydroxylated Dendritic Polyols
Dendritic polymers exhibit properties that often differ dramatically from those of the more traditional polymer types. Only minimal research has been done in the past to understand gas transport behavior of these unique polymers.In the present work, oxygen barrier properties of a series of inexpensive dendritic aliphatic polyesters (Boltorn™) containing multiple functional hydroxyl groups have been studied as a function of relative humidity (RH) and temperature. The structure of these HB polyols was also modified by cross-linking with linear aliphatic, 1,6- hexamethylene diisocyanate (HDI), to improve the mechanical properties and to reduce the water sensitivity.
Compatibilisation Protocol for the Processing of Polypropylene Organoclay Nanocomposites
The effects of compatibilisers on the structures and properties of polypropylene organoclay nanocomposites, produced through maleation or acrylation with a range of chain functionalized oligomers were investigated using wide-angle (WAXD) and small-angle X-ray diffraction (SAXD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and mechanical analysis. Results showed that optimal nanocomposite properties, exfoliation and dispersion of the clay particles in the PP matrix required wetting of the clay substrates by a low molecular weight and high functionality compatibiliser, loaded at moderate concentration.
An Investigtion of Metallocene and Ziegler-Natta Catalysed LLDPE/Clay Nanocomposites
The influence of controlled-chain branching in a metallocene-catalysed LLDPE (mPE) and random chain branching in a conventional LLDPE (zPE) on the exfoliation behaviour of an organoclay was investigated. Both X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed the clay exfoliation level to be significantly higher in the metallocene LLDPE. Rheological analysis suggested that higher shear stress during the processing of metallocene polyethylene, attributed to the narrower molecular weight distribution was responsible for this phenomenon.
Impact of Titanium Dioxide Surface Characteristics on Extrusion Processing
Interfacial interactions between the titanium dioxide pigment surface and the polymeric matrix have a significant impact on the energy requirements for incorporation and the rheology of the resulting compound. This study investigated the effect of screw geometry and operating conditions on dispersion performance and torque loading during twin-screw compounding of three different grades of titanium dioxide pigments with different surface treatments into highly loaded polyethylene masterbatches. It was found that the screw design and operating conditions where the pigments performed best were quite different for the three grades. It was found that low intensity mixing sections and cooler barrel temperature settings seemed to favor the pigment with a compatibilizing hydrophobic surface treatment and high intensity mixing sections and hotter barrel temperature settings favored the pigments that did not have such a surface treatment. It was also found that by optimizing screw designs, much higher throughputs and better dispersion could be achieved.
Twin Screw Extrusion of the Reactive Blends of Thermoplastic Polyurethanes and Poly(Vinyl Chloride)
The reactive blending of Poly (Vinyl Chloride) (PVC) and Thermoplastic Polyurethanes (TPU) was performed by using a counter-rotating, intermeshing twin-screw extruder. The blending technique consists of two sequential stages of mixing and reaction respectively. In the first stage, the PVC is pre-blended with monomers of the TPU (soft segment and chain extender). In the second stage, the polymerization of the TPU in-situ with the PVC takes place upon the addition of the third monomer of the TPU (diisocyanate). In this study, the novel in-situ reactive extrusion technique and the procedure for producing PVC/TPU blends are discussed.
Single Site Catalysts and Dual Reactor Technology Create More Freedom in Pe Rotomolding Resin and Product Designs
While polyethylene continues to be the resin of choice for rotational molding, advancements in material design are still required. From a structure-property perspective, a thinner lamellar thickness of a polyethylene resin may lead to a higher tie chain formation probability. It is also believed that longer polymer chains with proper comonomer incorporation enhance this probability. Single site catalysts and octene comonomer usage enable the design of rotomolding resins with superior properties compared with conventional Ziegler-Natta resins. This paper combines our fundamental understanding of this topic with experimental data.
Characterization of Reactive Blends of Thermoplastic Polyurethanes and Poly(Vinyl Chloride)
In this study, a novel reactive blending technique was used to produce PVC/thermoplastic polyurethane (TPU) blends. The blending technique consists of two sequential stages of mixing and reaction. In the first stage, the PVC is pre-blended with two monomers of the TPU (soft segment and chain extender). In the second stage, the in-situ polymerization of the TPU with the PVC takes place upon the addition of the third monomer of the TPU (diisocyanate). TPU monomers were changed in order to determine the effect of chemical structure and isomers on the miscibility with the PVC and the tensile properties of the resultant blends.
Nanotribology of Protein- Modified Surfaces
Nanoprobe technology has emerged as an important tool for the study of thin films and biological materials. Atomic force microscopy (AFM) is widely employed to determine surface features at the nano- to microscale, and is increasingly used for evaluation of friction and wear performance at small scales. Hydrophobins are a unique class of amphipathic fungal proteins that exhibit remarkable capability to modify surfaces, both natural and synthetic. Novel rigid rod polymers with high strength to weight ratios are of interest for a wide range of engineering and biomedical applications. The nanotribological properties of spin coated rigid rod polymer and hydrophobin-modified polymer surfaces are reported. Surface roughness analysis is reported for uncoated as well as hydrophobin-coated rigid rod polymer samples.
Material Properties of Thermal Conductive Thermoplastics for Mold Design and Processing Strategies
The use of highly filled thermal-conductive thermoplastics is an innovative approach to directly adjust the thermal conductivity of plastic parts for heating and cooling systems. Compared to standard resins thermal conductive thermoplastics show a higher thermal conductivity in the range of 2 – 20 W/mK. The filler-content and the high thermal conductivity affect directly the flow- and cooling-conditions during injection molding. Therefore, the manufacture of injection-molded parts requires adjusted processing strategies. In this paper properties of thermal conductive thermoplastics relevant to the design of injection-molded parts as well as the effect to relevant processing parameters are introduced.
Retardation of Shrinkage in Phthalosyanine Blue Pigmented Polypropylene Using Nanoclay as Filler
A common problem with crystalline polymers that occurs when an organic pigment is added to the melt matrix is non-uniform or anisotropic shrinkage. A nanoclay has been compounded into polypropylene. An organic pigment masterbatch was made and then added to the nanoclay/polyproplyene (PP) compound. Percent crystallinity was then tested using Differential Scanning Calorimeter (DSC). Percent elongation also was tested using a standard tensile testing machine. Shrinkage differences between colorant with and without nanoclay were measured using the ASTM flame-bar and mold and a two inch disk and mold.
Bioactive Composites for Tissue Regeneration
A wide variety of bioactive composites for bone regeneration have been developed and investigated over the last decades. In order to promote bioactivity, certain types of glasses, ceramics and minerals are incorporated into biodegradable or biostable polymers. In this study, several established and novel fillers such as calcium phosphates, silicates and glasses were screened for bioactivity. Promising candidates were then incorporated into two different grades of poly-?-caprolactone by solution mixing, and testing was conducted in a simulated body fluid to determine in vitro bioactivity. At different time periods the exposed samples were characterized by SEM, EDX and FTIR microscopy in order to investigate the formation of the apatite layer needed for bone ingrowth. The screening results of this work produced suitable polymer/filler combinations for further in vitro and in vivo testing in different types of tissue engineering applications.
Development of Plastic Recycling Companies in the Czech Republic: An Analysis Using Economic Value Added
Extensive use of plastic products in a country like the Czech Republic make the recycling of plastic unavoidable. This also is influenced by a host of factors such as increasing price of raw materials (oil and other semi processed products), growing concern for ecology and environment, etc. However, recycling is not only the technology alone, but it also includes issues such as legislation, both social and most importantly economics. The present study attempts to describe the economic conditions that influence the performance of plastic recycling companies. The paper analyses the conditions of development of plastic recycling companies in the Czech Republic using Economic Value Added (EVA) indicator.
Nucleation and Reinforcement of Carbon Nanofibers on Polystyrene Nancomposite Foam
As the demand for highly functional polymeric materials grows, nanocomposite foams are likely to play a vital role in the future foam industry. In this research work, carbon nanofibers (CNFs) were used as both nucleants and reinforcements for polystyrene (PS) foams. It was found that a microcellular foam structure could be achieved with low fiber loading. Moreover, the nano-scaled dimension of CNFs made them desirable elements to reinforce the cell walls, leading to an enhanced tensile modulus. Intensive shear force exerted by the twin- screw extruder broke the fibers in length and deteriorated their nucleation efficiencies.
Synthesis and Reinforcement of Nylon 6 Copolymers with Phenolics
Block copolymers of nylon 6 with 10, 15 and 20% of poly(ether-esteramide) as elastomeric phase were synthesized by reactive extrusion. These materials are the result of the anionic polymerization of ?-caprolactam in the presence of a linear prepolymer of poly(ether-esteramide) with a Grignard reagent (1). Reinforced copolymers were prepared by melt mixing copolymers containing 15% of elastomeric phase with 3, 5 and 7 phr of phenolic resin in a single extruder; and also copolymers with 10 and 20% of elastomer and 5 phr of phenolic resin. On the other hand, reinforced copolymer with 15% of elastomer phase and 3 phr of resin was also synthesized “in situ” by reactive extrusion.
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