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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Biaxial Orientation in Polyethylene Films: Comparison of Infrared Spectroscopy and X-Ray Techniques
In this study, blown low density polyethylene (LDPE) films were produced under different processing conditions. The orientation of the films was characterized in terms of their biaxial crystalline, amorphous and global orientation factors using birefringence, Fourier Transform Infrared Spectroscopy (FTIR) with a tilted incidence technique and X-ray pole figures. It is well established that FTIR can measure crystalline axes orientation for polyethylenes, as well as the orientation of the amorphous phase. On the other hand, X-ray pole figures determines the orientation of the crystalline axes, and in combination with birefringence can yield the amorphous phase orientation. The results from those techniques are compared and discussed in terms of the accuracy of the techniques and the contributions of different specific entities in FTIR measurements.
Effect of Extrusion Die Geometry on Molecular Orientation of Unfilled Polyethylene
The effect of die geometry on molecular orientation of unfilled polyethylene has been investigated. Four dies with similar exit geometry but having a combination of two different entry angles and two land lengths have been used with a 63.5mm diameter single screw extruder. Extrudate samples were collected using a haul-off rate equivalent to the calculated die exit velocity, to prevent post-die deformation. A range of haul-off rates was also imposed. Orientation was inferred from reversion tests. Land length was found to have the greatest influence on extrudate orientation, but effects due to entry angle were also observed.
Permeability and Mechanical Performance of 3-Layer EVOH/LLDPE Barrier Films with Blended Middle-Layers
EVOH Barrier films are typically 5-layer films comprising a central EVOH layer, tie layers and external polyethylene layers. In this paper, the barrier and mechanical properties of three-layer barrier films were investigated. As a possible mean to increase layer adhesion, the core EVOH layer was blended with linear low density polyethylene over a broad composition range. The tear strength, impact resistance, tensile properties and oxygen permeability were measured as a function of EVOH content. Good oxygen barrier properties were found for LLDPE concentration below 50%. The balance between interfacial adhesion, mechanical properties and oxygen permeability over the possible range of composition for central layer is discussed.
The Mechanical Properties and Crystallization Behaviour of Pigmented Propylene-Ethylene Random Copolymer
Samples of a commercial propylene-ethylene random copolymer containing 0% to 8% phthalocyanine blue pigment were injection moulded using mould temperatures 40°C to 80°C. Thermal analysis (DSC and DMTA) performed on all the samples show the presence of two distinct crystalline phases. The relative predominance of each phase was affected by the mould temperature and the nucleating effect of the phthalocyanine pigment. This binary phase morphology was shown to have a significant effect on the mechanical performance of the polymer, with great reductions in impact performance being recorded for pigmented samples.
Structure and Properties of the ? Nucleated Injection Molded Polypropylenes: Time Stability of ? Phase and Impact Strength
It is known that ?-phase of isotactic polypropylene (iPP) can improve toughness of samples. Notch impact strength of samples containing different amounts of novel ?-nucleating agent NU100 has been measured. Injection molding, WAXD, DSC, optical microscopy and Charpy impact tests were used to prepare samples and characterize the structure and impact strength. For the first time, measurements of the impact strength and the ?-phase content were carried out immediately after injection molding and then the same values were determined after 2 years. It was found that ?- phase is not time-dependent and also notch impact strength of samples does not change with time.
Morphology and Mechanical Property Relationship in Polypropylene Composites
Two high-crystallinity polypropylene (PP) based, inorganic filler-reinforced composites, i.e., PP/R-talc and PP/CaCO3 nanoparticles, were prepared and investigated. The mechanical properties of PP/R-talc and PP/CaCO3 composites were investigated using tensile test, flexural test, Izod impact test, and dynamic mechanical analysis. In addition, the morphology of the samples was studied by transmission electron microscopy and differential scanning calorimetry. Improvements of 150% and 30% in tensile moduli of PP/R-talc and PP/CaCO3 samples, respectively, can be attributed to the good filler particle dispersion and proper stress transfer between the matrix and mineral filler reinforcement.
Impact Modification of Calcium Carbonate Filled Polypropylene
Commercially available octene-copolymers were used to alter the impact performance of a high melt flow polypropylene, both neat and filled with 20% calcium carbonate. Materials were compounded on a co-rotating twin-screw extruder before being injection molded and tested for Gardner and Izod impact properties. Tensile and flexural properties were also measured. Twin screw compounding conditions had a marked affect on properties. High shear conditions were favored in order to realize high impact properties. Modifiers with higher comonomer content showed the best improvement in impact properties. The improvement in impact performance showed a non-linear relationship with modifier content.
Surface Grafting of Polyacrylamide from Polyethylene-Based Copolymer Film
Atom transfer radical polymerization (ATRP) was used to grow polyacrylamide from the surface of ethyleneacrylic acid copolymer (EAA) film. The surface functionalization required initiator immobilization and surface graft polymerization. All reaction steps were conducted at 24 ± 3 °C; polymerization was done in aqueous solution. For initiator immobilization, the carboxylic acid groups on EAA film were converted to acid chloride groups; further reaction with ethanolamines gave hydroxyl groups onto which 2-bromoisobutyryl bromide initiator was attached. FTIR data indicated that 1.64 ± 0.09 times higher initiator density was achieved by using diethanolamine, relative to ethanolamine. Acylamide monomer was polymerized from the initiator via ATRP to yield non-distorted, transparent films.
Viscoelastic Properties of Homogeneous Block Copolymer/Homopolymer Blends near Microphase and Macrophase Separation Transitions
We studied the anomalous effect of critical composition fluctuations on the viscoelastic properties of block copolymer/ selective homopolymer blends near the microphase and macrophase separation transition point under shear flow. The anisotropy and suppression of composition fluctuations caused by the applied flow field affect strongly the dynamic modulii and viscosity of the blends and render substantial difference compared to those of single block copolymer melt or homopolymer blends. The theoretical derivations were carried out by solving a simplified Langevin equation used by Onuki and Kawasaki with a mean-field approach.
Effect of Reactive Additives on the Properties of Polypropylene/Unsaturated Polyester Blends
Reactive melt modification of a low molecular weight unsaturated polyester (UP) and its blends with polypropylene (PP) were studied. The rheological and morphological properties of the polyester and its blends can be greatly improved not only by adding a peroxide to initiate competing reactions within the blend components that would lead to compatibilization, but also by some organic and inorganic additives such as coagents and alkaline earth metal oxides which can generate ionic crosslinking of the polyester. Extrusion process conditions are discussed along with DSC, FTIR, SEM and other characterization methods utilized to investigate the structure of the modified products.
Morphology Development in PA6/PP System by Chaotic Mixing: Effect of Viscosity Ratio and Composition
Self similar mixing structures produced by chaotic mixing were utilized in this study to produce an array of mixing morphology, such as nested layers, elongated fibrils, droplets and their combinations in the blending of two immiscible polymers, polypropylene (PP) and polyamide-6 (PA6). Experiments were conducted in a specially designed batch chaotic mixer with PA6 as the continuous phase and the results were compared with those obtained in conventional batch mixing devices. The zero shear viscosity ratios were varied between 1 and 30, while the composition of PP phase was varied between 10 and 30wt%. It was found that repeated stretching and folding of the dispersed phase domains initially produced lamellar structures with much thinner layers and delayed the breakup process into fibrils and droplets. Consequently, domains much smaller than equilibrium sizes were obtained. The PP-domains were the smallest for a viscosity ratio of 1 and the largest for a viscosity ratio of 30, while the domain sizes increased with composition in all cases, purportedly through delayed breakup and increasing chances of coalescence.
In-Situ Compatibilization of PP/EPDM Blends during Ultrasound Aided Extrusion
Blends of isotactic polypropylene (iPP) and uncured ethylene-propylene diene rubber (EPDM) were treated by high intensity ultrasonic waves during extrusion. Die pressure and power consumption were measured. The effects of different gap sizes, blend ratios and number of ultrasonic horns were investigated. The rheological properties, morphology and mechanical properties of the blends with and without ultrasonic treatment were studied. In-situ compatibilization of the blends was observed as evident by their stable morphology after annealing and improved mechanical properties. The obtained results indicated that ultrasonic treatment induced the thermomechanical degradations and led to the possibility of enhanced molecular transport and chemical reactions at the interfaces. Processing conditions were established for enhanced in-situ compatibilization of the PP/EPDM blends.
Effect of High Intensity Ultrasonic Waves on Polypropylene, Polyamide 6 and Their Blends
The mechanical, rheological properties and morphology of polypropylene (PP), polyamide 6 (PA6) and their blends treated by high intensity ultrasound have been investigated. A lower head pressure and better mechanical properties are simultaneously achieved in the extrusion of these thermoplastics. A competition between the ultrasonically enhanced polycondensation reaction and degradation was observed for PA6. These enhanced polycondensation and degradation have a different mechanism than the thermally induced reaction. The better strength of ultrasonically treated PA6 is attributed to this reaction, leading to higher molecular weight, higher crystallinity and more uniform crystal size distribution. For PP, the degradation at high amplitude of ultrasound was observed. The mechanical properties of treated PP are maintained at low amplitude of ultrasound. For ultrasonically treated PP/PA6 blend, a competition between degradation and in-situ compatibilization was found. At a certain level of amplitude of ultrasound and a certain blend ratio, the tensile toughness and impact strength of treated blends were almost doubled, and a more stable morphology upon shearing and heating was observed.
Mechanical Properties and Morphology of Ternary PP/EPDM/PE Blends
The effect of high density polyethylene (PE) addition on the mechanical properties and morphology of polypropylene (PP) impact modified with ethylene-propylene- diene monomer (EPDM) has been studied. It was found that the modulus, tensile strength and impact resistance can be improved by PE addition. As predicted by the spreading coefficient, subinclusion morphologies where PE is encapsulated by the EPDM, were observed. The viscosity of the PE and its incorporation position along the twin-screw extruder was also found to play an important role on the final blend morphology and mechanical properties. The effect of the morphology on blends’ properties is discussed.
Influence of Ionomeric Compatibilizers on the Morphology and Properties of Amorphous Polyester/Polyamide Blends
The utilization of sulfonated polyester ionomers as minor component compatibilizers in blends of an amorphous polyester and polyamide was investigated. The blends were prepared using twin-screw extrusion and compared to solution blends to investigate the effect of elevated temperatures and shear mixing on blend miscibility and/or phase behavior. The thermal and mechanical properties of the blends were investigated using dynamic mechanical analysis (DMA) and tensile testing while the phase domain sizes of the solution blends with respect to ionomer content were studied using small angle light scattering (SALS) and phase contrast optical microscopy. Binary blends of the amorphous polyester and polyamide were immiscible with poor mechanical properties, while blends containing the polyester ionomer as a minor component compatibilizer showed a significant reduction in the dispersed domain sizes.
The Effectiveness of SPETG as a Compatibilizer for PC/PETG Blends
The melt-mixed blends of an amorphous copolyester, poly(ethylene-co-cyclohexane 1,4-dimethanol terephthalate) (PETG) and the sulfonated analog of the copolyester (sPETG), with bisphenol-A polycarbonate (PC) were investigated over the entire composition range. Dynamic mechanical analysis (DMA) for the PC/PETG blends showed two, ?-relaxations, which coincided with the glass-transition temperatures of the two respective homopolymers. In contrast, the PC/sPETG blends displayed two ?-relaxations but with a shift of the PC ?- relaxation to lower temperatures. Unlike the PC/PETG blends, the tensile strain at break and yield stress for the PC/sPETG blends follows closely to a linear composition dependence due to greater interaction between the blend components. Analysis of the FT-IR spectra for the PC/sPETG blends indicates an interaction between the sulfonate group of sPETG and the carbonyl group on the PC backbone.
A Study on the Effects of Chaotic Mixer Design and Operating Conditions on the Development of Morphology in Immiscible Polymer Systems
Self-similar mixing structures, a novel feature of chaotic mixing, were utilized in this study to produce an array of mixing microstructures, such as nested layers, elongated fibrils, droplets and their combinations in the blending of two immiscible polymers, polypropylene (PP) and polyamide-6 (PA6). Simulations based on Newtonian flow model were used to compute the Poincaré maps and stretching distribution to determine the effect of shear gap and chaotic mixing parameter, such as angular displacement per period (?), on the degree of mixing produced in a batch chaotic mixing device. Experimental results at low mean shear rates, with PA6 as the continuous phase (90wt%), corroborate with the findings of simulation study.
Thermal and Rheological Properties of Novel Thermoplastic Polyimide Blends
We report the results of our preliminary studies on the thermal and rheological behavior of a new semicrystalline polyimide (PI) type R-BAPB and its miscibility with amorphous PI type R-BAPS having similar chemical structure to the former. To ensure miscibility of the above relatively viscous PI, a prepolymer prepared by melting dianhydride and diacetyl derivatives of aromatic diamine (BAPB type) was blended with thermoplastic R-BAPS at 50/50 and 70/30 wt % ratio. At the start of the chemical reaction, the resulting mixture was completely miscible with a low viscosity of about 50 Pa?s at 300°C that subsequently increased to about 3?104 Pa?s after 1 hr at 300°C. This mixture can provide new PI blends with better processability and thermal properties than a simple thermoplastic mixture of R-BAPS and R-BAPB having the same weight ratio.
Structure and Properties of New Polyimide Bonded Magnets with Enhanced Benefits
We report a new method for preparing thermally-stable and processable polyimide (PI)-bonded magnets via the chemical transformation of PI prepolymers (based on diacetyl derivatives of diamines and dianhydrides) filled with magnetic Nd-Fe-B alloy particles (75-100 ?m). The prepolymers with amorphous structure, after removing of up to 5% volatile, can be melted at 220±10°C to give a fluid with a very low viscosity of 15±5 Pa?s. This low viscosity of the prepolymer facilitates blending it with the magnetic particles at relatively high volume fractions up to 85 vol. %. The resulting PI-bonded magnets were found to exhibit excellent thermal stability, high storage modulus of 10 GPa at 400°C; and a 10% increase in energy product over that of commercially available bonded magnet materials.
Compatibilization of Poly(Phenylene Ether) and Polyamide-6 Blends by Functionalized Polystyrenes
In this paper the compatibilizing effect of a polystyrene which was synthesized via controlled free radical polymerization and endcapped with an epoxy function in the immiscible blends of PPO and PA-6 was investigated. The properties being examined were notched Izod impact and tensile of injection molded parts. Tensile properties during exposure in a xenon arc weatherometer under exterior automotive conditions per SAE J1960 were investigated. The morphology was examined by scanning electron microscope. Results had shown that mechanical properties improved with addition of this functionalized compatibilizer. Blends of PPO/PA-6,6 and PPO/PA-6 were also compared.
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