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Abstract In this work, four different organomontmorillonites (OMMts): Nanomer[R] I.30E, Dellites[R] 43B and 67G and Nanolin[R] DK2 were selected to prepare OMMt-poly (lactic acid) (PLA) nanocomposites blown films, using a [...]

This article is aimed at investigating the effect of a calcined kaolin filler (CKao) on polyethylene terephthalate (PET). The influence of a silane coupling agent, chain extension, and post extrusion uniaxial hot-stretching on the final properties of the produced composites were studied as well. PET-CKao films were prepared via melt blending using a twin-screw extruder followed by stretching above the glass transition temperature at controlled conditions. The morphology of the composites before and after stretching was observed by SEM. Rheological measurements were also performed to characterize the polymer melts. Mechanical and optical properties as well as the oxygen transmission rate of the composites were also investigated. The results showed that addition of CKao particles, even at low filler content, improved drastically the mechanical and barrier properties compared to the neat PET. This effect was more pronounced in case of hot-stretched samples. The main drawback observed with these CKao particle composites was an increased haze. Processing parameters including stretching temperature and stretching ratio were found to have a significant effect on the final properties; however, the influence of the stretching rate was negligible., INTRODUCTION Polyethylene terephthalate (PET) is a commodity grade polyester, which has found many applications such as textile fibers and food packaging materials due to its good chemical resistance, thermal stability, [...]

In this study, the effect of uniaxial stretching on the thermal, oxygen barrier and mechanical properties of aliphatic polyamide 6 (PA6) and aromatic Poly(m-xylene adipamide) (MXD6) nylon films as well as their in-situ polymerized nanocomposites with 4 wt% clay were studied. Cast films were prepared by extrusion process and rapidly cooled using an air knife. The precursor films were uniaxially stretched at 110C with draw ratios varying from 1.5 to 5. DSC results showed that the cold crystallization temperature ([T.sub.cc]) of the uniaxially stretched MXD6 and MXD6/clay films drastically shifted to the lower temperatures when draw ratio increased. The aromatic nylon films had lower oxygen permeability than those of the aliphatic films, due to more rigidity and chain packing. However, the oxygen permeability of the stretched films increased with draw ratio (DR) up to a critical value for each sample, while further stretching resulted in a reduction in the oxygen permeation. This phenomenon was related to the changes in free volume upon uniaxial stretching. The ability of different geometrical models to describe the experimental relative permeability data was investigated. The Bharadwaj model that took into account clay orientation was the most successful one to predict the oxygen barrier characteristics of the stretched nanocomposites at high draw ratios. The Young's modulus and tensile strength of the aliphatic and aromatic nylons increased with uniaxial deformation, while the flexibility and elongation at break of the former decreased with increasing DR. A larger increase in the Young's modulus of the uniaxially stretched nanocomposite films compared with the neat samples was observed and could be related to the improvement in the clay orientation as well as a better alignment of the crystalline phase due to incorporating the clay platelets in the polymer matrix. In contrast, the flexibility of the stretched MXD6 improved remarkably (ca., 25 times) compared with the precursor film (DR = 1) when the draw ratio increased to 1.5. This could be related to the effect of hot stretching on the enhancement of polymer chains relaxation and mobility at low draw ratios., INTRODUCTION Improving the barrier properties of commercial thermoplastics to the permeation of atmospheric gases such as oxygen or water vapor, and consequently increasing the shelf-life of food products, is one [...]

In many industrial sectors, the surface properties of polymers are of particular importance. This applies, for instance, to painting, printing, and any coating on surface of polymeric objects. Hydrophilicity and wettability characteristics are known to be determined by the chemical makeup of the polymer surface. Blending with an additive or a polymer containing high-energy functional groups is widely recognized as a potential technique to overcome disadvantages of low surface energy of polymers due to its convenient processing. Surface migration of polyethylene glycol (PEG) in Polyethylene Terephthalate (PET) host was investigated using a low-molecular-weight PEG (8 kDa) because of its good hydrophilicity, low toxicity, biocompatibility, and chain mobility. A twin-screw extruder was used to blend the materials and prepare the polymer blend films. The results of surface characterizations showed that PEG renders the PET surface more hydrophilic, but not high enough for many applications. In a second approach, the addition of a third component, polystyrene (PS), to the blend in a small amount resulted in a remarkable surface enrichment of PEG at the polymer/air interface for the ternary polymer blend (PET-PEG-PS). Surface analysis revealed that the surface concentration of PEG in the ternary polymer blend film was significantly larger than that of the binary one. POLYM. ENG. SCI., 55:349-358, 2015. © 2014 Society of Plastics Engineers, INTRODUCTION Surface wettability is an important property of polymer surfaces and is strongly dependent upon the composition. A proper control of the surface wettability has been the subject of considerable [...]

In this study, rheological, crystal structure, barrier, and mechanical properties of polyamide 6 (PA6), poly(m-xylene adipamide) (MXD6) and their in situ polymerized nanocomposites with 4 wt% clay were studied. The extent of intercalation and exfoliation as well as type of crystals, crystallinity, and thermal transitions were investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Dynamic rheological measurements revealed that incorporation of nanoclay significantly increases complex viscosity of MXD6 nanocomposites at low frequencies, which was related to the formation of a nanoclay network and exchange reaction between MXD6 chains. The comparative study of dynamic characteristics (G' (ω) and G' (ω)) for aliphatic and aromatic polyamide nanocomposites with their neat resins as well as the relaxation spectra for both polymer systems confirmed the possibility of the aforementioned phenomena. Although, the crystallinity of MXD6 films was lower as compared to PA6 films, the permeability to oxygen was more than 5 times better for the former. Incorporating 4 wt% clay enhanced the barrier property, tensile modulus, and yield stress of PA6 and MXD6 nanocomposite films in both machine and transverse directions without sacrificing much puncture and tear resistances. The PA6-based films showed higher tear and puncture strength as compared to MXD6 films., INTRODUCTION Insufficient barrier properties of commercial thermoplastics to the permeation of atmospheric gases such as oxygen and water vapor are a major problem in the packaging industry. In particular, a [...]

Nanocomposites based on isotactic polypropylene (tPP) and titanium dioxide ([TiO.sub.2]) nanoparticle containing 1-15 vol% (4.6-45.5 wt%) of the nanoparticle were prepared by the melt blending process. The effect of an [...]

Four single-site metallocene catalyst based polyethy-lenes (mPEs), one ultra low density polyethylene, one conventional linear low density polyethylene (LLDPE), and one low density polyethylene (LDPE) were selected to characterize the effect of side chain branches on physical and mechanical properties. Rheological experiments were carried out to extract complex viscosity and elasticity as a function of frequency. Elonga-tional viscosity tests were also performed to assess long chain branching. For some mPEs, sparse long chain branching improved shear thinning and elasticity of the chains in melt state. During elongation, mPEs with a narrow linear chain distribution showed initially greater melt strength whereas for longer elongation, the mPEs with long chain branching lead over in strength. Cast films were produced from the mPEs and their physical (such as crystallinity, crystal size) and mechanical properties were tested. A double melting peak was observed in the differential scanning calorim-etry thermograms of the mPE films. A relatively sharp strain hardening behavior in tensile tests was observed for the mPEs films when compared to LLDPE. Fourier transform infrared was used as an effective and fast method to investigate side chain length. It was found that the positioning of side chain, co-monomer length, and content influence the melting behavior of mPE films. POLYM. ENG. SCL, 52:1089-1098, 2012. ©2011 Society of Plastics Engineers, INTRODUCTION Low density polyethylene (LDPE) was the first polyethylene discovered by ICI (England). A free-radical polymerization under high temperature-pressure resulted in a highly branched structure that hinders melt crystallization and [...]

In this study, the orientation, mechanical as well as the optical properties of multilayer films of nanoclay filled poly (lactic acid) (PLA) as the core layer and polyethylene (PE) as the skin layer obtained from the film blowing process were investigated. The effect of nanoclay content in the range of 1-7.5 wt% was considered. The orientation of the polymers crystal unit cells, alignment of clay platelets as well as the extent of intercalation and exfoliation were studied using wide angle X-ray diffraction (WAXD). The measurement of d-spacing of the 001 plane (normal to platelets plane) of the clay tactoids indicated intercalation of the silicate layers in the PLA nanocomposite multilayer films. The Young modulus and tear resistance along the machine and transverse directions (MD and TD, respectively) improved significantly with the presence of the nanoparticles and percentage of nanofiller studied. The haze of the nanocomposite films decreased with clay concentration up to 5 wt% and increased by further addition of the nanoclay. POLYM. ENG. SCI., 51:2151-2158, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION It is well established that the effective dispersion of anisotropic particles with high aspect ratios such as short fibers, plates, and whiskers within a continuous polymer matrix, in combination [...]

Polyethylene terephthalate (PET) melt-spun fibers were modified with multiwall carbon nanotubes (MWCNT) to obtain conductive microfibers smaller than 90 µm in diameter. Physical properties such as crystallinity and orientation of as-spun fibers were studied by X-ray diffraction, Raman spectroscopy, and microscopy techniques at different draw ratios (DR) and MWCNT concentrations. Morphological and orientation analysis of MWCNT after melt-spinning process showed agglomerates formation and highly oriented CNTs. The study of the orientation of PET crystalline phase in drawn fibers proved that the addition of nanoparticles decreases the orientation of crystalline units inside the fibers. The orientation of MWCNT as well as that of PET chains was studied using Raman spectroscopy at different DR and a high degree of CNT orientation was observed under high DR conditions. Mechanical and electrical properties of as-spun fibers were also investigated. Our results showed that it was possible to achieve conductive fibers at a MWCNT concentration of 2% w/w, and more conductive fibers using higher DR were also obtained without increasing the MWCNT concentration. Mechanical properties results showed interestingly high value of maximum tensile strain at break ([ζ.sub.max]) of nanocomposite fibers, up to three times more than pure PET fibers. POLYM. ENG. SCI., 50:1956-1968, 2010. [C] 2010 Society of Plastics Engineers, INTRODUCTION Specific properties of polyethylene terephthalate (PET) such as high drawability have made this polymer one of the most important polymers in textile industry, as demonstrated by the large body [...]

Photonic bandgap Bragg fibers feature periodic sequence of layers of different materials. In those particular waveguides, the wave path is controlled by a periodical spatial modification of the refractive index. Depending on the periodicity of the structure and on the refractive index contrast, a specific wavelength range is propagated along the fiber axis. In this work, we developed all-polymeric photonic bandgap Bragg fibers based on polystyrene (PS)/polymethyl methacrylate (PMMA) alternating layers. We describe a novel and efficient method for the preparation of the fibers preforms, and we present the fibers drawing process and the transmission properties of the resulting Bragg fibers. POLYM. ENG. SCI., 50:1122-1127, 2010. [C]2009 Society of Plastics Engineers, INTRODUCTION Polymeric photonic crystals waveguides have recently attracted considerable interest. Compared with conventional glass waveguides, polymeric materials offer several advantages: low cost, low processing temperatures, possibility of combining different materials, [...]

Blends of a long-chain branched polypropylene (LCB-PP) and a linear polypropylene (L-PP) were prepared using a twin-screw extruder. Linear viscoelastic properties such as complex viscosity, storage modulus, and weighted relaxation spectrum were determined as functions of LCB-PP content. Shear data obtained from commercial rheometers as well as from a slit-die rhe-ometer were used to verify the Cox-Merz relation for the neat components as well as for a blend. Elonga-tional properties were obtained using a Sentmanat Extensional Rheometer (SER) unit mounted on an Advanced Rheometric Expansion System (ARES) rheometer and the converging die. A significant strain hardening was observed for the neat LCB-PP as well as for all the blends, but the strain hardening decreased with increasing strain rate. The apparent steady elongational viscosity values evaluated using the converging die were observed to be comparable at high deformation rates to those obtained from the SER unit, but the differences increased as the strain rate decreased. POLYM. ENG. SCI., 50:191-199, 2010. ©2009 Society of Plastics Engineers, INTRODUCTION In comparison with polyethylene, polypropylene (PP) has higher melting point, lower density, higher chemical resistance, and better mechanical properties, which makes it more interesting for many industrial applications. Due [...]

Three Polyvinylidene fluoride (PVDF) different in molecular structure were used to produce nanocomposities films by cast extrusion with a particular emphasis on maximizing the β crystal phase content. The PVDF/clay compounding followed by cast film production was carried out through melt extrusion using a twin screw extruder equipped with a slit die. X-ray diffraction (XRD) results showed that clay melt intercalation is almost similar for all three PVDFs. The XRD results also revealed that nanocomposite films from PVDF with branched chain structure (PVDFB) generated the greatest amount of β phase. FTIR spectroscopy measurements confirmed the XRD results but also revealed that significant stretching of the melt films at the die or rapid cooling would adversely affect the formation of β phase. The amount of β phase obtained based on nanoclay compounding was compared with that obtained from conventional method: stretching of molded PVDF film with initial α phase. Stretching of PVDF film at 60°C yielded pure β phase that means complete transformation of α to β From mechanical properties, tensile tests were carried out on PVDF nanocomposite films to evaluate mechanical strength. PVDF with low molecular weight exhibited a very low strain at break while branched PVDF and high molecular weight PVDF could sustain more strain. POLYM. ENG. SCI., 49:200-207, 2009. [C] 2008 Society of Plastics Engineers, INTRODUCTION Polymer/Clay nanocomposites have been the focus of significant attention in recent years and new applications are introduced progressively. This is mostly because a small amount of nanoclay enhances significantly [...]

The objective in this study is to establish a model for the prediction of tensile properties using various types of polyethylene films (LLDPE, HDPE, and LDPE). A series of blown films were produced by varying three process parameters: take-up ratio, blow-up ratio, and frost line height. The tensile properties of the resulting films were investigated in relation to their microstructural characteristics. The microstructural parameters were determined by differential scanning calorimetry, wide angle X-ray diffraction (WAXD) pole figures, SAXS (small angle X-ray diffraction), and birefringence measurements. The orientation parameters of the films were measured by WAXD and birefringence. They were determined for both crystalline and amorphous phases. The crystalline content, lamellar thickness, and crystal sizes were obtained from DSC and WAXD. The SAXS technique was used to find the average length of the crystalline and amorphous layers. A model for the tensile modulus is proposed and correlated to some structural parameters including crystallinity, orientation factors for crystalline c-axis and amorphous phase, lamellar thickness, crystal size, the average length of the crystal layer, and long spacing period. The measured modulus and the calculated one were compared and a reasonable agreement was found between them for all series of films. POLYM. ENG. SCI., 47:1430-1440, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION For many years, the dependence of mechanical properties on the morphological structure of the polymer has been the subject of research works. Many investigations have been reported concerning complex [...]

Five different polypropylene resins were characterized by rheology to study the effect of melt rheology on the row-nucleated lamellar structure development during the cast film process. The arrangement and orientation of the crystalline and amorphous phases were examined by WAXD (wide angle X-ray diffraction) and FTIR (Fourier transform infrared) methods. Tensile tests were carried out to examine the effect of orientation on the behavior of the samples. It was found that the molecular weight evaluated from rheology and the processing conditions played a crucial role on the orientation of the crystalline and amorphous phases and, in turn, affected significantly the tensile response. The molecular weight was the main parameter that controlled the orientation and it was found that the resin with a higher molecular weight had a tendency to form a planar crystalline morphology as the draw ratio increased. It was also observed that a planar morphology was associated with a suppression of the yield behavior in the tensile measurements. POLYM. ENG. SCI., 47:1170-1178, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION A row nucleated lamellar structure as an initial morphology has been a matter of concern for developing microporous membranes based on a three-stage process (melt-extrusion/annealing/uniaxial-stretching) [1, 2]. In this [...]

Fluorescence quenching of phenanthrene (Ph) and anthracene (An) fluorophores by maleic anhydride (MAH) and n-octadecenylsuccinic anhydride (ODSA) quenchers in solid polypropylene (PP) films were studied. Results were compared with fluorescence quenching of the same fluorophores by MAH and ODSA quenchers in chloroform solution. Contrary to the results obtained in solution, it was observed that fluorescence emission of Ph fluorophore in PP films was more efficiently quenched by ODSA than by MAH. This was due to the better miscibility of Ph with ODSA than with MAH. When An fluorophore was used instead of Ph, it was observed that its fluorescence intensity in PP films was notably reduced by the addition of MAH. This was mainly due to the Diels--Alder reaction, which consumed a part of the An molecule. However, fluorescence intensity of An strangely increased with the addition of ODSA instead of MAH. Because of short lifetime of An (around 6 ns), ODSA had no quenching effect on An. POLYM. ENG. SCI., 47:192-199, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION Fluorescence quenching of polyaromatic molecules by electron deficient molecules was extensively studied in liquid solutions and both dynamic (collisional) and static fluorescence quenching mechanisms were developed [1-3]. The collisional [...]

In this study, linear low-density polyethylene films were produced using different processes (film blowing and biaxial orientation) and processing conditions. The orientation of the films was characterized in terms of their biaxial crystalline, amorphous, and global orientation factors using birefringence, tilted incidence polarized Fourier Transform Infrared Spectroscopy (FTIR), and X-ray diffraction pole figures. Evaluation of a simplified FTIR procedure without the use of the tilted method for the determination of crystalline orientation factors proposed in the literature is also evaluated and assessed. The results indicate that FTIR overestimate the crystalline orientation factors, particularly for the crystalline a-axis. Significant discrepancies are also observed for the b-axis orientation, which may be due to an overlap of the amorphous phase contribution. Those differences are larger for films with low orientation, such as blown films. Amorphous phase orientation from FTIR depends on the band used and is not necessarily in agreement with that determined from the combination of X-ray and birefringence. The simplified FTIR procedure is proven to be inadequate in the case of linear low-density polyethylene blown films studied having a random lamellar crystalline morphology. POLYM. ENG. SCI., 46:1182-1189, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION Semicrystalline polyolefin films represent a large segment of the plastics industry. The most widely used biaxial processes for films are the standard film blowing process (for various polyethylenes, PE), [...]

The purpose of this study is to investigate the biaxial stretchability. the structure developed, molecular orientation and shrinkage of linear low-density octene copolymers (LLDPEs) biaxially stretched using a laboratory biaxial stretcher. Seven resins having different molecular characteristics were used in this study. The effect of stretching temperature and rate on stretchability is assessed. Biaxial orientation factors for the crystalline axes as well as that of the amorphous phase were determined using FTIR spectroscopy and shrinkage of oriented films was measured. The results indicate that the high molecular weight tail (Mz) and comonomer content play important roles in orientation of the resins. Higher Mz, MWD and resin content eluting above 90°C (by TREF technique) tend to increase orientation, and finally, some correlation between orientation and Mz, MWD and resin content eluting above 90°C and between shrinkage and amorphous orientation were observed., INTRODUCTION Polyethylenes are by far the most widely used resins in the film industry. They are used for a variety of applications and in different film processes; blown film, cast [...]

The micromechanical behavior of poly(ethylene terephthalate), PET, modified with a metallocene polyolefin copolymer (mPE) was investigated. Uniaxial deformation tests were performed using a tensile stage in a scanning electron microscope. [...]

We report the solid-state die-drawing of polypropylene and blends of polypropylene with a polyethylene elastomer to produce highly oriented products with enhanced mechanical properties. The blends showed an improvement in [...]

R. J. YAN (a) A. AJJI (b) D. M. SHINOZAKI (a) Crystalline syndiotactic styrene/p-methyl styrene copolymer (SPMS) has been oriented by tensile drawing at various temperatures between the glass transition [...]

Highly oriented high-density polyethylene (HDPE) and polypropylene (PP) were obtained by solid state extrusion near, but below, the melting temperature. Draw ratios of 6 and 11 were obtained using properly designed dies, preformed billets and lubrication for different extrusion temperatures. Orientation induced significant changes in properties and morphology that are related to the final draw ratio. The draw ratio was observed to decrease with an increase in extrusion speed due to the molecular relaxation occurring because of local heating during deformation. An increase in the degree of crystallinity was observed for the oriented polymers as well as a large improvement in the tensile modulus. Significant molecular relaxation and elastic recoil were observed during processing. Extrusion speed strongly increases the extent of relaxation, and, consequently, reduces many of the mechanical properties., INTRODUCTION Orienting semicrystalline polymers by solid state forming improves the strength and modulus in the orientation direction and produces a high degree of crystal alignment (1-3). There are several solid [...]

Orientation of initially amorphous poly(ethylene terephthalate) films and sheets was carried out by means of tensile drawing in a tensile tester, roll-drawing using a series of four rolling stations, and by die-drawing. The drawing temperature was 80 and 90 ° C and drawing rate ranged from 2 to 20 cm/min in the different processes. Crystallinity was observed to increase with draw ratio for all these processes. The onset of crystallinity development depends on the drawing rate. The glass transition temperature was essentially constant and crystallization temperature decreased with increasing draw ratio. The trans conformers content was observed to increase with draw ratio at the expense of the gauche conformers for the three processes. The orientation of the trans conformers increases readily from the beginning of draw and saturates rapidly. The orientation of the gauche conformers was negligible. Some differences are observed for the behavior of the 1020 and 730 [cm.sup.-1] benzene ring bands, which may be due to differences in the benzene ring configuration at the surface as a result of different deformation mechanisms for the die and roll-drawing. However, further investigations to elucidate this hypothesis are needed. The mechanical properties obtained in the longitudinal direction increased for all the processes. In the transverse direction, the roll and die-drawing processes induced a decrease in modulus and strength with increasing draw ratio, similar to that observed for uniaxial orientation. This indicates that these processes are mainly uniaxial, despite the plane strain nature of the deformation., INTRODUCTION Properties of polymers can be enhanced significantly through orientation processes either in the solid state, in the rubbery state, or from the melt. On the other hand, replacement of [...]

In this paper, we study the relaxation behavior of initially amorphous poly(ethylene terephthalate) (PET) films drawn, at 80 ° C using a draw rate of 2 cm/min, to a draw ratio (Λ) from 1 to 5 and then quenched to room temperature. These films were then heated at different temperatures from 68 to 80 ° C for different times and their orientation determined. The orientation measurements were performed by transmission infrared spectroscopy and the bands used for the determination of orientation were those at 1340 and 970 [cm.sup.-1] for the trans conformers, normalized using the 1410 [cm.sup.-1] benzene ring vibration. The crystallinity was determined by thermal analysis. It is shown that when PET is drawn to Λ values up to 2-2.5 (before stress-induced crystallization), the orientation relaxes rapidly at temperatures close to the glass transition temperature of PET. For Λ values of 3 or higher, the orientational relaxation of the amorphous regions is hindered. This effect is ascribed to the development of strain-induced crystallites, which are believed to act as pseudo-crosslinks., INTRODUCTION The orientation of thermoplastics affords an excellent approach to the improvement of their strength in the direction of elongation. In this context there have appeared numerous studies in the [...]

Polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET)-based composites for proton exchange membrane fuel cell bipolar plates (BPs) were prepared at different crystallization temperatures and characterized by X-ray diffraction, differential scanning calorimetry, and resistivity setup. Composite conductivity was made possible by using a mixture of carbon black (CB) and graphite (GR). To improve composite processability, its viscosity was reduced by adding a small amount of cyclic butylene terephthalate (c-BT) oligomer and thermoplastic polyolefin elastomer. In the PVDF/PET-based composite, it was found that PVDF phase could crystallize easily but PET crystallization was difficult. Because of the CB/GR additives, the formed crystals in PVDF/PET phases had a poor perfection degree and showed a lower melting temperature when compared with pure PVDF and PET. It was observed that PET nucleation was accelerated but not that of PVDF. According to through-plane resistivity results, composite crystallization temperature range was divided into two parts (below/above 170°C), in which a different variation behavior of through-plane resistivity was observed. It has been proved that the resistivity was mainly governed by the network of CB/GR developed inside the PET phase, and decreasing the crystallinity of PET led to a decrease of through-plane resistivity, which is desirable for BPs. POLYM. ENG. SCI., 52:25522558, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Energy consumption is becoming higher than before because of the rapid increase of society's development and human's needs. In the near future, traditional fossil energy will not be enough [...]

Polymer blends are mixtures of at least two polymers and/or copolymers comprising more than 2 wt% of each macromolecular component. Most blends are immiscible, and need to be compatibilized. The compatibilization must not only ensure improvement in performance, but it must be reproducible, insensitive to forming stresses and repeated processing. This review on compatibilization of polymer blends is prepared in three parts: (i) description of the interface/interphase; (ii) compatibilization by addition of a copolymer (with a special emphasis on the use of block copolymers); and (iii) reactive compatibilization., INTRODUCTION Polymer blends are mixtures of at least two macro-molecular species, polymers and/or copolymers. For practical reasons, the name blend is given to a system only when the minor component [...]

In this study, blends of virgin and recycled polyethylene (PE) and poly(vinyl chloride) (PVC), with a methylmethacrylate-ethylacrylate copolymer as a processing aid, were prepared in the molten state. Different additives such as ethylene-vinylacetate copolymers, ethylene-methacrylic acid ionomer, and two peroxides (dibenzoyl and dicumyl), in the presence of a coupling agent, were used to compatibilize the blend or possibly induce graft structures. The blends' morphologies, tensile properties, and impact properties were studied. For blends with low copolymer concentration (below 3 wt%) the mechanical test data indicated a good performance. In the case of blends with ethylene methacrylic acid ionomer, improvements in the mechanical properties were obtained also at higher additive concentrations. Of the two peroxides, better results were obtained using the dibenzoyl one. The morphological studies indicated that the blends that showed good mechanical properties were better dispersed and had improved interphase adhesion., INTRODUCTION It has been recognized that neat poly(vinyl chloride) (PVC) is a largely useless thermoplastic material as it readily degrades at normal processing temperatures, releasing hydrochloric acid. To bypass these [...]

In this article, we investigate the effect of weld lines on the tensile mechanical properties of unmodified and copolymer modified high density polyethylene (HDPE) and polystyrene (PS) blends. The homopolymers were melt blended in the proportion of 20 wt% HDPE and 80 wt% PS using a twin screw extruder at a temperature of 200 ° C. The results show that the mechanical properties are generally lower when weld lines are present. The decrease of the mechanical properties is much more pronounced for the blends. The addition of small amounts of a commercial styrene/butadiene copolymer significantly improves the strength and the elongation at break of this blend. An optimum copolymer concentration was observed at 3 wt%. This value coincides with the interphase saturation concentration of the copolymer obtained from the analysis of the DMTA (dynamic mechanical and thermal) properties of the blends. The copolymer was also found to induce important changes in the morphology of the blend. The interdiffusion of the polymer fronts in the weld region was also improved by the presence of the copolymer. It is believed that these two aspects contribute to the enhanced properties obtained with copolymer modified blends in presence of weld lines. An important effect of the injection temperature on the tensile strength and the elongation at break of welded samples with copolymer modified blends was observed. The effect of mold temperature on these properties was less important mainly at low injection temperatures. Only a slight effect of these two parameters was observed for the tensile modulus in the range of mold and injection temperatures considered in this study., INTRODUCTION The injection molding process is one of the most important polymer processes by which polymeric resins are converted into useful finished products. A wide variety of complex geometry articles [...]

An elongational rheometer coupled with a primary extrusion device has been used for the detection of flow limitations in the extrusion of linear low density polyethylenes (LLDPE). The shear rate for the onset of flow defects (fd) was found to decrease with increasing branch length in the LLDPE copolymer, but the severity of fd was greater in butene- than in hexene- and octene-copolymers. Studies of partially fractionated LLDPE showed that the critical shear rate for the onset of fd was closely related to the minimum molecular weight in the distribution of molecular weights. In addition, evaluations of bond strengths in LLDPE/metal joints showed that the same molecular weight parameter significantly affected that performance criterion. In combination, the experimental findings provided confirmation of sporadic adhesive failure (slip/stick effect) as the mechanism responsible for the occurrence of observed flow defects. Its manifestation is attributable to the thermodynamic drive that promotes the preferential localization of low molecular weight moieties at surfaces and at interfaces of polyolefins such as LLDPE.

R. J. YAN [a] A. AJJI [b][*] D. M. SHINOZAKI [a] Blends of syndiotactic styrene/p-methyl styrene copolymer (SPMS) and poly(styrene)-block-poly(ethene-co-butylene)-block-polystyrene (SEBS) as well as their uniaxial drawing behavior and performance [...]

R. E. PRUD'HOMME [*] The effect of processing conditions on the structure and properties of roll drawn poly(ethylene terephthalate) (PET) was examined. It was found that, when roll drawing amorphous [...]

Orientation of polymers plays an important role in polymer processing operations and in properties of oriented polymers. Well-established processes such as film blowing, cast film tentering, and fiber spinning and [...]

Film and fiber processes represent a large segment of the plastics industry and the R & D activities of many research labs. These processes take advantage of orientation of polymer [...]

Ultrasonics has been used for the determination of the mechanical properties of oriented semicrystalline polymers through time-of-flight measurements of elastic waves propagating in various directions within the material. While being nondestructive, such a method allows one to obtain more mechanical moduli with a better accuracy than the conventional tensile tests, especially regarding the shear properties and the Poisson's coefficients. Until now, the approach used to interpret the data was approximate and not rigorous. We present here a self-consistent rigorous approach for interpreting time-of-flight data based on the group velocity including allowance for lateral displacement of the transmitted beam. Results are presented for roll-drawn PET with various draw ratios. These samples are considered to have transversely isotropic symmetry. For the Young's moduli, comparisons are made with conventional tensile tests and the differences observed are interpreted in terms of viscoelastic effects considering both the amorphous and crystalline phases., 1. INTRODUCTION One approach for the production of polymers with high mechanical performance consists in orienting the chain structures by drawing or extrusion in the solid state. When an unoriented, [...]