Polyethylene Terephthalate Matrix Research Articles

Effect of matrix morphology on the wear and friction behavior of alumina nanoparticle/poly(ethylene) terephthalate composites

The friction and wear properties of poly(ethylene) terephthalate (PET) filled with alumina nanoparticles were studied. The nanoparticle loading was varied from 1 to 10 wt.%. The nanocomposite samples were tested in dry sliding against a steel counterface. The results show that the addition of nanoparticles can increase the wear resistance by nearly 2× over the unfilled polymer. The average coefficient of friction also decreased in many cases. The nanocomposites form a more adherent transfer film that protects the sample from the steel counterface, although the presence of an optimum filler content may be due to the development of abrasive agglomerates within the transfer films in the higher wt.% samples. This study varied both crystallinity and weight percent of filler in a PET matrix in an attempt to separate the effects of nanofillers and crystallinity on the tribology.

Mechanical and rheological studies on polyethylene terephthalate‐montmorillonite nanocomposites

AbstractIn this work, a detailed investigation of the rheological and mechanical properties of nanocomposites based on polyethylene terephthalate (PET) and montmorillonite clays is presented. A series of additives [maleic anhydride (MAH), pentaerythritol (PENTA), and alkylammonium chlorides from amines of various chain lengths] were used as compatibilizers. The influence of the additives on the mechanical and rheological behavior of the PET matrix was evaluated separately, through their individual contributions. To shed more light on the reported decrease in melt viscosity of organoclay composites with respect to the matrix viscosity, observed in nylon and PET nanocomposites, the polymer molecular weight was related to the resulting rheological and mechanical properties of the systems. Results reveal that the PET nanocomposites behave quite differently in shear as opposed to elongation. The viscoelastic properties in shear present low values when the molecular weight decreases because of the processing operations. However, properties under tension increase over those of the matrix, manifesting the presence of a network formed between the clay and the polymer. Polym. Eng. Sci. 44:1094–1102, 2004. © 2004 Society of Plastics Engineers.

Rubber toughened semicrystalline PET: influence of the matrix properties and test temperature

This article is concerned with the effect of the inherent matrix properties (matrix molar mass and crystallinity) as well as the temperature on the impact behaviour of rubber toughened semicrystalline polyethylene terephthalate (PET). The dispersed phase consists of a blend of an ethylene- co-propylene rubber (EPR) and a copolymer of ethylene and 8 wt% glycidyl methacrylate (E-GMA8) acting as a compatibilising agent, leading to PET/(EPR/E-GMA8) blends. The influence of the matrix molar mass on the impact behaviour of rubber toughened PET is found to primarily originate from its effect on the blend phase morphology, rather than from an inherent effect of the molar mass itself. The dispersed phase particle size is seen to decrease with increasing PET molar mass. A direct correlation between the impact strength and the interparticle distance could be established. A critical interparticle distance (ID c) of 0.1 μm could be determined, independent of the PET molar mass. The brittle–ductile transition temperature ( T bd) of the blends with a varying matrix molar mass also displayed a strong correlation with the interparticle distance, independent of the matrix molar mass. However, this correlation appears to depend on the crystalline characteristics of the PET matrix material since an incompletely crystallised PET matrix leads to an increase of the T bd.

The Influence of Injection-Molding Variables and Nucleating Additives on Thermal and Mechanical Properties of Short Glass Fiber/PET Composites

Investigation of thermal and mechanical characteristics of short glass fiber reinforced polyethylene terephthalate (PET) has been carried out, focusing on the influence of three of the variables involved in the injection-molding process: mold temperature, holding pressure time and closed mold time. Mold temperature plays a decisive role in controlling crystallinity development of PET matrix, which is directly correlated with the values of tensile strength and elongation at rupture. Holding pressure time acts improving piece compaction. Longer closed mold times lead to the highest values of developed crystallinity. Moreover, sodium benzoate, titanium dioxide and an ionomer have been added in order to study efficacy as nucleating agents.

Effects of pore size in 3-D fibrous matrix on human trophoblast tissue development.

The effects of pore size in a 3-D polyethylene terephthalate (PET) nonwoven fibrous matrix on long-term tissue development of human trophoblast ED27 cells were studied. Thermal compression was used to modify the porosity and pore size of the PET matrix. The pore size distributions in PET matrices were quantified using a liquid extrusion method. Cell metabolic activities, estradiol production, and cell proliferation and differentiation were studied for ED27 cells cultured in the thermally compressed PET matrices with known pore structure characteristics. In general, metabolic activities and proliferation rate were higher initially for cultures grown in the low-porosity (LP) PET matrix (porosity of 0.849, average pore size of 30 microm in diameter) than those in the high-porosity (HP) matrix (porosity of 0.896, average pore size of 39 microm in diameter). However, 17beta-estradiol production and cell differentiation activity in the HP matrix surpassed those in the LP matrix after 12 days. The expression levels of cyclin B1 and p27kip1 in cells revealed progressively decreasing proliferation and increasing differentiation activities for cells grown in PET matrices. Also, difference in pore size controlled the cell spatial organization in the PET matrices and contributed to the tissue development in varying degrees of proliferation and differentiation. It was also found that cells grown on the 2-D surface behaved differently in cell cycle progression and did not show increased differentiation activities after growth had stopped and proliferation activities had lowered to a minimal level. The results from this study suggest that the 3-D cell organization guided by the tissue scaffold is important to tissue formation in vitro.

Matrix morphology and fibre pull-out strength of T700/PPS and T700/PET thermoplastic composites

The main objective of this fundamental study was to investigate effects of processing conditions and resulting matrix morphology on interfacial bond strength of fibre reinforced thermoplastic composites. Using a hot stage microscope, single fibre pull-out samples were produced with T700S high strength carbon fibre and two semicrystalline thermoplastic matrices, polyphenylene sulphide (PPS) and polyethylene terephthalate (PET), respectively. Processing temperatures and cooling histories were the major variables in sample preparation. The T700S fibre had no clear effect on the surrounding PPS and PET matrix morphology, as long as direct cooling at constant rates was selected. A transcrystalline phase around the fibres could be induced in the T700S/PPS system, if isothermal crystallization was carried out at 227°C. Fibre pull-out tests were conducted at room temperature and two basic failure paths were observed, i.e. debonding at the fibre-matrix interface and cohesive failure of the matrix close to the fibre surface. The results indicate that slow cooling rate and a resulting coarse spherulitic morphology around the fibres correlate with high interfacial shear strength. In fact somewhat higher strength values were obtained for samples with transcrystalline layers around the fibres.

Influence of spinning velocity on mechanical and structural behavior of PET/nylon 6 fibers

AbstractInfluence of spinning velocities on the mechanical and structural properties of polyethylene terephthalate (PET)/nylon 6 blend fibers have been reported. Fibers of PET/nylon 6 containing a small percentage of nylon (5% by weight) have been melt‐spun at 3 different spinning velocities (2,900; 3,200; 3,600 m/min). The fibers have been characterized by thermal, morphological, structrual, and mechanical analysis. Various techniques such as SEM, DSC, X‐ray diffraction, hot water shrinkage (HWS), viscosity, and birefringence have been used. SEM analysis revealed that in the blend, nylon 6 is well‐dispersed as spheres in the PET matrix. The blend shows a marked decrease in the melt‐flow index, which in turn leads to a beneficial effect on the rheological properties of the PET without negatively influencing its mechanical characteristics. This finding results in a saving on energetical requirements of the processing, as both temperature and pressure of spinning can be decreased. © 1995 John Wiley & Sons, Inc.

Blends of polyethylene terephthalate with Co[poly(ethylene terephthalate‐p‐oxybenzoate)] I. Crystallization kinetics by DSC study

AbstractThe dynamic and isothermal crystallization behaviors of polyethylene terephthalate (PET) blended with two types of co[poly(ethylene terephthalate‐p‐oxybenzoate)] copolyesters with different compositions, i.e., POB/PET = 20/80 (P28) and POB/PET = 80/20 (P82), has been studied by using differential scanning calorimetry (DSC). Both of these copolyesters in 10 wt % increase crystallization rate of PET in a manner similar to that of a nucleating agent. It is found that sample P28, which is an isotropic copolyester, accelerates the crystallization rate more significantly than that of P82, which is a thermotropic copolyester. The Avrami exponents n and rate constants k of these samples based on DSC studies were obtained in order to discuss the crystallization kinetics of PET accelerated by these copolyesters. The crystallization rate of the blends is also increased by 8 min blending due to the increased uniformity of the copolyester dispersed in the PET matrix. © 1994 John Wiley & Sons, Inc.

Determination of benzene residues in recycled polyethylene terephthalate (PETE) by dynamic headspace-gas chromatography.

A dynamic headspace-gas chromatography (HS/GC) method was developed to quantitate benzene in recycled PETE material derived from 21 PETE beverage bottles. The analytical system consisted of a purge-and-trap apparatus which was interfaced directly with a gas chromatograph/flame ionization detector. Cryofocusing and non-cryofocusing GC systems were used. The technique was applied to spiked PETE test samples which were prepared at various benzene concentrations ranging from 100 ppb to 117 ppm. The initial spiked benzene concentration in the PETE test samples was determined gravimetrically. The HS/GC technique was limited by the slow desorption rate of benzene from the PETE matrix; as a result, multipurges were performed at 60 degrees C. Regression analysis was done on the multipurge data to develop a desorption model which would predict the total amount of benzene in the PETE. The calculated results agreed with the experimental recoveries within +/- 10%. Recovery depended on the initial benzene level in the PETE and ranged from 70 to 90% after the first five purges.

Fracture of glass-fibre reinforced poly(phenylene sulphide)

An extensive study of the fracture behaviour of an injection-moulded PET (polyethylene terephthalate)/glass-composite system has recently been completed [1-8]. The PET matrix is generally considered to be ductile, while PPS (polyphenylene sulphide) is considered brittle. Therefore, for comparative purposes, a study of the brittle PPS matrix reinforced by short glass fibres would be of interest. This is the thrust of the present investigation. A PPS matrix reinforced with 40 wt % E-glass fibres was made by injection molding. The mechanical lifetime data were obtained by stressrupture testing [4, 5]. The microstructure was examined by scanning electron microscopy (SEM). The through-thickness microstructure is shown in Fig. 1. The surface of this SEM micrograph was cut parallel to the mold-fill direction (MFD) and to the thickness of the plaque. Near the surfaces of the plaque, the glass fibres are oriented approximately parallel to the MFD, whereas in the centre the fibres lie more nearly normal to the MFD. Two kinds of compact tension specimens are used: the L specimen is cut so that the fibre axis lies parallel to the loading axis; the T specimen has the fibre axis normal to the stress axis. Thus, in the L configuration, the main crack must run perpendicular to the fibres and in the T configuration, parallel to the fibres. A dead load is applied to the specimen until the specimen fails by part-through failure. The environment is controlled by a corrosion cell, within which the specimen is immersed during the whole lifetime of stress-rupture testing. Two kinds of aggressive environments are used, 10 vol. % HCI solution and 10 wt % NaOH solution, and compared with stress-rupture under air. Data for mechanical lifetime under air, 10% HC1 and 10% NaOH are shown in Fig. 2. Both the L (Fig. 2a) and the T (Fig. 2b) geometries are shown. The curves in Fig. 2 are the 0.25 and 0.75 reliability (R) curves, representing a law of the form [4]