Copolyester Research Articles

Bicomponent melt-spinning of filaments for material extrusion 3D printing

In material extrusion (MEX) 3D printing, the layer-by-layer structure often presents challenges such as poor adhesion, void formation and rough surfaces, which can compromise the mechanical properties of printed parts and limit their applications. This study investigates whether 3D printing from bicomponent core-sheath filaments instead of printing from conventional monofilaments provides a potential solution to some of the described issues. Based on different material selections, various bicomponent filaments, comprising a rigid core and a soft sheath, were produced through co-extrusion and overcoating extrusion techniques. Tensile properties of 3D-printed specimens with different raster angles (0° vs 45°) from bicomponent filaments are compared to the properties of reference specimens printed from conventional monofilaments. While similar mechanical properties were observed for some 3D-printed specimens from bicomponent filaments (e.g., polylactic acid (PLA)-based), as compared to reference specimens, some core-sheath combinations of polyamide (PA) demonstrated a noticeable improvement of the mechanical properties of 3D-printed specimens, particularly for 45° raster angles. In particular, bicomponent filaments comprising a carbon fiber reinforced PA (PACF) core and a pure PA sheath exhibited improved processability and enhanced structural strength. Moreover, two overcoated filaments consisting of polyethylene terephthalate (PET) and polyphenylene sulfide (PPS) monofilament cores with a copolyester (CoPES) sheath were prepared for 3D printing. 3D-printed parts made from PET/CoPES overcoated filaments exhibited good compatibility and satisfactory results when printed at temperatures above the melting point of PET. These findings demonstrate the potential of bicomponent filaments to enhance both printability and mechanical performance of 3D-printed parts, offering new avenues for material selection and design optimization in various 3D printing applications.

Evaluation of Fused Deposition Modeling Materials for 3D-Printed Container of Dosimetric Polymer Gel.

Accurate dosimetric verification is becoming increasingly important in radiotherapy. Although polymer gel dosimetry may be useful for verifying complex 3D dose distributions, it has limitations for clinical application due to its strong reactivity with oxygen and other contaminants. Therefore, it is important that the material of the gel storage container blocks reaction with external contaminants. In this study, we tested the effect of air and the chemical permeability of various polymer-based 3D printing materials that can be used as gel containers. A methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride gel was used. Five types of printing materials that can be applied to the fused deposition modeling (FDM)-type 3D printer were compared: acrylonitrile butadiene styrene (ABS), co-polyester (CPE), polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) (reference: glass vial). The map of R2 (1/T2) relaxation rates for each material, obtained from magnetic resonance imaging scans, was analyzed. Additionally, response histograms and dose calibration curves from the R2 map were evaluated. The R2 distribution showed that CPE had sharper boundaries than the other materials, and the profile gradient of CPE was also closest to the reference vial. Histograms and dose calibration showed that CPE provided the most homogeneous and the highest relative response of 83.5%, with 8.6% root mean square error, compared with the reference vial. These results indicate that CPE is a reasonable material for the FDM-type 3D printing gel container.

Parameters Characterization of Dielectric Materials Samples in Microwave and Millimeter-Wave Bands

In this work, an optimized broadband method using multilayer transmission lines to characterize dielectric permittivity and loss tangent of material samples is presented. For this purpose, a microstrip line loaded with a piece of the selected dielectric to be characterized is used. From two-port measurements, and using different length lines, the propagation constant can be obtained. To minimize random errors and to improve the accuracy, an overdetermination of the method increasing the number of lines measured and a criterion to choose the optimal line lengths is considered. First, the measurement method itself is applied to uncovered microstrip lines and an accurate model of the substrate is obtained. Second, the lines are covered with several materials, made by fused deposition modeling (FDM) additive manufacturing technique, such as acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), high impact polystyrene (HIPS), thermoplastic polyurethane (TPU), copolyester (CPE), FLEX, polyethylene terephthalate glycol (PETG), and nylon. A model of the transmission line considering the cover is developed, and an electromagnetic (EM) simulator is used to indirectly determine the cover material electrical parameters. Results show excellent agreement with EM simulations in the 0.1-67-GHz frequency band, so they assess the suitability of the proposed method.

Effect of 3D Printing Parameters on the Refractive Index, Attenuation Coefficient, and Birefringence of Plastics in Terahertz Range

The refractive indices, attenuation coefficients, and level of birefringence of various 3D printing plastics may change depending on the printing parameters. Transmission terahertz time‐domain spectroscopy was used to look for such effects in Copolyester (CPE), Nylon, Polycarbonate (PC), Polylactic acid, and Polypropylene. The thickness of each sample was measured using an external reference structure and time‐of‐flight measurements. The parameters varied were printer nozzle size, print layer height, and print orientation. Comparison of these parameters showed that a printer’s nozzle size and print layer height caused no change in real refractive index or attenuation coefficient. A change in printing orientation from vertical to horizontal caused an increase both in real refractive index and in attenuation coefficient. In vertically printed samples, the increase in birefringence was proportional to the increase in layer height and inversely proportional to nozzle size. There was no measurable intrinsic birefringence in the horizontally printed samples. These effects should be taken into account in the design of FDM 3D printed structures that demand tailored refractive indices and attenuation coefficients, while also providing a foundation for nondestructive evaluation of FDM 3D printed objects and structures.

Initial Bacterial Adhesion and Biofilm Formation on Aligner Materials.

The present study aims to assess the initial bacterial adhesion and biofilm formation on different aligner materials. A total of four different aligner materials, CA-medium (CAM), copolyester (COP), Duran (DUR), Erkodur (ERK), were tested. Stimulated human saliva was obtained from six healthy volunteers. Salivary bacteria were harvested by centrifugation, and 1 mL of the salivary suspension was injected onto each sample surface for 2 h and 3 days, respectively. The samples were then washed twice with 5 mL 0.9% NaCl solution, and non-adherent bacteria were removed. The adherent microorganisms were dislodged from the sample surfaces after ultrasonication for 4 min in 1 mL 0.9% NaCl on ice. After the incubation of the adherent salivary bacteria under both aerobic and anaerobic conditions on Columbia blood agar plates at 37 °C and 5% CO2 and in anaerobic jars overnight, several dilutions thereof were used for the determination of CFUs. This protocol was applied three times, obtaining an average of nine independent measurements for each material group. Overall, the differences between the tested aligner materials as well as between the materials and controls were not of statistical significance (p > 0.05). Regarding initial bacterial attachment and biofilm formation, the tested aligner materials are comparable to enamel and metal orthodontic brackets and can be therefore considered for clinical use. The four tested aligner materials CAM, COP, DUR, ERK showed no significant differences in initial microbial attachment and biofilm formation of aerobic and anaerobic species compared to enamel and conventional brackets.

Properties of Thermoplastic-Bonded Plywood: Effects of the Wood Species and Types of the Thermoplastic Films.

There are a lack of proper adhesives that meet the wood industry requirements of being environmentally friendly, low cost, and easy to use; thus, the application of thermoplastic polymers, especially films, is promising. This work expands our knowledge about the possibility of using thermoplastic films for the production of environmentally friendly plywood. The effects of the adhesives type and wood species on the properties of plastic film bonded plywood were studied. Sliced veneers of two hardwoods (birch and beech) and one softwood (spruce) were used in the experiments. Three types of thermoplastic films—low-density polyethylene (LDPE), co-polyamide (CoPA), and co-polyester (CoPE)—were used as an adhesive for bonding plywood samples. Melamine–urea–formaldehyde (MUF) resin was used as a reference. The influence of the type of adhesive and wood species as well as their interaction on the properties of plywood was significant. The lowest bonding strength demonstrated plywood samples bonded by LDPE, and the highest bonding strength in the samples was shown in those bonded by CoPA. A significant difference was found between softwoods and hardwoods in terms of their influence on the physical and mechanical properties of plywood samples. From the obtained data, it follows that softwoods provide much lower values of bending strength (MOR), modulus of elasticity (MOE), and bonding strength than hardwoods. The obtained bonding strength values of plastic-bonded plywood panels ranged from 1.18 to 2.51 MPa and met the European standard EN 314-2 for Class 1 (dry conditions) plywood.

Phase Coarsening in Polycarbonate and Amorphous Copolyester Blends

Phase Coarsening in Polycarbonate and Amorphous Copolyester Blends

Halloysit Nanotüp Takviyeli Kopoliester Termoplastik Elastomer Kompozitler: Isıl ve Mekanik Özelliklerin İncelenmesi

Nano dolgular polimerlerin ısıl ve mekanik özelliklerini geliştirmek için sıklıkla kullanılan malzemelerdir. Halloysit (HNT) içi boş tüp şeklinde doğal bir alümina silikat nano dolgudur. Bu çalışmada, termoplastik elastomer ailesinin bir üyesi olan kopoliester (COPE) polimerinin ısıl ve mekanik özellikleri organofilik yüzey modifikasyonu yapılmış HNT (Org-HNT) dolgusu ile geliştirilmeye çalışılmıştır. Değişik oranlarda (3,5 ve 7 phr) Org-HNT içeren kompozitler bir dahili karıştırıcı yardımıyla eriyik harmanlama metodu ile hazırlanmıştır. Elde edilen kompozitlerin morfolojik, reolojik, ısıl ve mekanik karakterizasyonları saf COPE ile karşılaştırmalı olarak incelenmiştir. Taramalı elektron mikroskobu (SEM) analizi, 3 ve 5 phr Org-HNT içeren kompozitlerin matris içinde göreceli daha homojen ve ince bir dağılım sergilediğini, 7 phr Org-HNT kullanıldığında ise nanotüplerin agregat şeklinde kaldığını göstermiştir. Org-HNT varlığında COPE’nin erime sıcaklığı artma eğilimi göstermiş ve bununla birlikte nanotüplerin nükleasyon ajanı etkisi ile kristalizasyon sıcaklığı yaklaşık 8°C artmıştır. Kompozitlerin elastik modül değerleri ve Shore sertlikleri Org-HNT miktarının artması ile doğru orantılı olarak artarak, 7 phr Org-HNT içeren kompozitte saf COPE ile karşılaştırıldığında yaklaşık %55’lik modül artışı bulunmuştur. COPE’nin başlangıç bozunma sıcaklıkları Org-HNT’lerin iyi dağılım gösterdiği 3 ve 5 phr kompozitlerinde gelişme gösterirken 7 phr kompozitinde azalmıştır. Bununla birlikte bütün kompozitlerin maksimum bozunma hızları saf COPE’den daha düşük değerler almıştır.

Intrinsic high thermal conductive co-polyester based on offset π-π stacking

It has been known that phonon mean free path along polymer chains is much larger than in transverse directions because weak interaction between polymer chains leads to chain distortion and entanglement. In order to improve intensity of intermolecular interaction, a series of co-polyesters (CPE) containing different content of offset π-π stacking structure in side chains were synthesized by means of polycondensation and transesterification in this work. WAXD patterns unfolded diffraction peak at 2θ of 27.6°, standing for structure of offset π-π stacking. On enlarging intensity of offset π-π stacking interaction, specific heat capacity of CPE increased from 1.140 Jg−1K−1 to 1.410 Jg−1K−1 and thermal diffusivity rose from 0.194mm2s−1 to 0.245mm2s−1. As a result, CPE sample exhibited excellent thermal conductivity (TC) of 0.381 Wm−1K−1, which is around twice that of traditional thermoplastics. Hence offset π-π stacking interaction could strengthen capacity of heat absorption and thermal conduction at the same time, which might be a good candidate for enhancing thermal conductivity of intrinsic polymers. Furthermore, strong π-π interaction in side chains could maintain modulus when temperature is over glass temperature. And the Young modulus grew from 0.14 GPa to 0.44 GPa with the augment of offset π-π stacking structure.

Effect of Poly(ethylene glycol) Crystallization on Ionic Conduction and Dielectric Response of Imidazolium-Based Copolyester Ionomers

A molecular-level understanding of ion and polymer dynamics in imidazolium–poly(ethylene glycol) (PEG) copolyester ionomers having different counteranions [PF6– vs (CF3SO2)2N–], alkylene spacer len...

Study on the Characteristics of Walnut Shell/Co-PES/Co-PA Powder Produced by Selective Laser Sintering.

Agricultural and forestry wastes are used as materials for selective laser sintering (SLS) to alleviate resource shortage, reduce the pollution of the environment, lower the cost of materials, and improve the accuracy of parts produced by SLS. However, the mechanical properties of wood–plastic parts are poor, and thus they cannot be applied widely. In order to improve the mechanical properties of wood–plastic parts, a new type of walnut shell polymer composite (WSPC) was prepared by a polymer mixing method and was used to produce parts via SLS. Additionally, the dimensional accuracy, morphologies, density, and mechanical properties of the WSPC parts were studied. The results showed that the addition of a small amount of copolyamide (Co-PA) powder could effectively improve the mechanical properties and decrease the density of the WSPC parts. By increasing the amount of Co-PA powder and decreasing that of copolyester (Co-PES) powder, the mechanical properties first increased, then decreased, and finally increased again; in addition, the density first decreased then increased. By increasing the preheating temperature, the mechanical properties and density of the WSPC parts were enhanced.

A Study on Xylitol Based Copolyester for In vitro Degradation Applications

A Study on Xylitol Based Copolyester for In vitro Degradation Applications

Influence of ground tire rubber devulcanization conditions on properties of its thermoplastic vulcanizate blends with copolyester

Devulcanized rubber (DR) was prepared from used truck tires via thermo-chemical devulcanization. Effects of devulcanizing reaction time and temperature were studied, and the DR contained higher sol fraction but had lower crosslink density than un-devulcanized rubber (UDR). Furthermore, the soluble fraction (sol fraction) increased with devulcanizing time and temperature. Devulcanizing for 4min at 180°C was chosen as the most efficient alternative. Then, thermoplastic vulcanizates (TPVs) from blends of copolyester (COPE) with two alternative types of recycled rubber (i.e., DR and UDR) were prepared and their mechanical, morphological, rheological, thermal and swelling properties were investigated. It was found that the dynamically cured DR/COPE blends exhibited higher mechanical and thermal resistance than the dynamically cured UDR/COPE blends. Furthermore, the complex viscosity and storage modulus of the dynamically cured DR/COPE blends decreased with devulcanizing time, due to breakdown of the rubber network and the carbon main chains in rubber molecules. In addition, phase separated micron-sized vulcanized rubber domains were finely dispersed in the COPE matrix, and their size correlated well with the mechanical strength and other related properties. However, the rubber domains agglomerated with excessive devulcanization, causing inferior mechanical strength.

Synthesis of hydrophilic copolyesters and the characterization of their moisture-related cooling properties

A series of copolyesters (Co-PETs) containing poly(ethylene glycol) (PEG), 5-sodiumsulfodimethyl isophthalate (DMS), and dimethyl isophthalate (DMI) were synthesized via the conventional two-step melt-polycondensation method. The synthesized Co-PETs were characterized by 1H-NMR spectroscopy, FT-IR spectroscopy, differential scanning calorimeter (DSC), and thermogravimetric analyzer (TGA). The DSC results showed that the melting temperature (T m) and the heats of fusion (ΔH m) of Co-PETs decreased with increasing the DMS content in Co-PET, while the inclusion of PEG did not affect their thermal properties significantly. The water absorption and the water contact angle of the Co-PET films were found to be significantly affected by the DMS content rather than PEG content. The moisture-related cooling properties of the fabric samples made of Co-PET 5 as well as PET were evaluated by using liquid moisture management tester (MMT) and Q max measurements. The MMT and Q max results indicated that Co-PET 5 fabric containing DMS 1.0 mol% and PEG 10.0 wt% in Co-PET seemed to be a good candidate for the fabric having durable cooling effects.

Preparing copolyester–titanium dioxide nanocomposites with low melting point via in situ hydrolysis, catalysis and esterification process

Copolyester (CP)-titanium dioxide (TiO2) (CPT) nanocomposites with low melting point were synthesized by esterification of terephthalic acid, isophthalic acid, ethylene glycol and 1,4-butanediol monomers in the presence of tetrabutyl orthotitanate (TBOT). TBOT hydrolysis caused the TiO2 nanoparticles to act as catalysts for polymerization. Transmission electron micrographs showed that the TiO2 nanoparticles with the content ranging from 0.2 wt% to 0.4 wt% were well dispersed in the copolyester matrix. The thermal properties of the nanocomposites were assessed by differential scanning calorimetry. The melting point of CPT nanocomposite with 1.2 wt% TiO2 was 201.9°C, significantly lower than that of pure polyethylene terephthalate (above 260°C). Therefore, the obtained CPT nanocomposites with low melting point are potentially better for industrial applications than the commercial product.

Influence of blend ratio on properties of novel thermoplastic vulcanizates based on copolyester/epoxidized natural rubber blends

Novel thermoplastic vulcanizates based on copolyester (COPE) and epoxidized natural rubber with 30 mol% epoxide (ENR-30) were prepared with various blend ratios and their properties were investigated. The main target was to prepare the dynamically cured COPE/ENR-30 blends with low hardness (lower than 80 Shore A) but superior in damping properties. The mixing torque of the blend mixer was captured and it was found that increasing the fraction of rubber increased the final mixing torque. Dynamic mechanical properties of the blends were also determined. It was found that with increasing rubber proportion, storage modulus and complex viscosity were increased but tan δ was decreased. In addition, morphology of the blends shows increasing size of vulcanized rubber domains dispersed in the thermoplastic matrix with increasing of rubber proportion. However, the strength properties decreased in terms of Young’s and 100 % moduli, tensile strength, elongation-at-break, and hardness. This might be attributed to the increasing size of vulcanized rubber domains. Enhanced rubber elasticity and damping properties were observed with increasing rubber content in the blends, as indicated by decreased tension set and tan δ. Furthermore, temperature scanning stress relaxation results show that with increasing rubber content the blends had their relaxation curves shifted upwards and thermal resistance increased. In addition, thermal properties characterized by DSC show the decreasing heat of crystallization (H) of COPE, or decreasing crystallinity, with increasing rubber content.

Changes in Mixing Torque, Mechanical and Dynamic Rheological Properties of Epoxidized Natural Rubber and Copolyester Blends as Affected by Epoxidized Natural Rubber Contents

Thermoplastic natural rubber (TPNR) based on epoxidized natural rubber with 30 %mol epoxide (ENR-30) and copolyester (COPE) blends was prepared in a molten state by using roller rotor internal mixer. Effect of various ENR contents on mixing torque together with mechanical and dynamic properties of the ENR-30/COPE blends was investigated. It was found that the mixing torque and complex viscosity increased with increasing contents of the ENR in the blends. This was due to higher polarity the ENR molecules caused interaction and entanglement of the ENR molecular chains with higher viscosity. Furthermore, improvement of elastomeric properties of the ENR-30/COPE blends was clearly observed, especially in the blends with higher proportion of the ENR. These improved elastomeric properties with high elongation at break, low tension set and high storage modulus together with low tan δ. This observation correlated to higher elastic component in the blend caused promoting higher elastic response in combination with increasing of interaction between the ENR and the COPE phases.

Thermoplastic Natural Rubber Based on Blending of Maleated Natural Rubber and Copolyester: Effect of Blend Ratios on Mechanical, Thermal, Dynamic and Morphological Properties

Maleated natural rubber (MNR) was synthesized and formulated to prepare thermoplastic natural rubber (TPNRs) by blending with copolyester (COPE). It was found that tensile strength and hardness of the TPNRs increased with increasing proportions of COPE, while the elongation at break decreased. Furthermore, tension set decreased with increasing proportions of MNR in the blends which reflects enhancing of rubber elasticity. Themogravimetry analysis (TGA) was used to characterize the TPNRs. It was found that the decomposition temperature (Td) of the blend increased with increasing proportions of COPE. Morphological properties were also determined by SEM technique. It was found that the MNR/COPA simple blends with the proportion of rubber 40, 50 and 60 wt % exhibited the co-continuous phase structures.

2,3-butanediol based liquid crystalline random copolyester, synthesis and characterisation

A copolyester was synthesized using 2,3-butanediol as one of the diols with phthaloyl chloride as Diacid chloride. 2,5-ditertiary butyl quinol, was used as another diols for the synthesis of random copolymer. A formation of copolyester was confirmed using Ultraviolet (UV), Fourier Transform Spectroscopy Infrared (FTIR), Nuclear Magnetic Resonance(NMR) spectral techniques. Thermal studies were carried out using Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA). Hot Stage Optical Polarising Microscope (HOPM) was studied to confirm the existences of mesophase. Elemental analysis further confirms the formations for the copolymer. Morphology of the copolyesters was also characterized using Scanning Electron Microscope (SEM). Results of the investigation confirms a relatively new entry copolymer in the family of liquid crystalline copolymers. Key words: Copolyester, thermo gravimetric analysis, differential scanning calorimetry, infrared spectroscopy, nuclear magnetic resonance, scanning electron microscope, characterization.

Synthesis, Characterization and Ultrasonic Determination of Certain Copolyesters Containing Bis (Arylidene) Acetone Moiety in the Main Chain

Six copolyesters were prepared from bis(4-hydroxybenzylidene)acetone (HBAC) and bis(4-hydroxy-3- methoxybenzylidene)acetone (MBAC) (as varying diol, diol-1) with adipoyl chloride, azelaic acid dichloride and sebacoyl chloride and 4-(4-nitrophenylazo)resorcinol (as a common diol, diol-2) by phase transfer catalysed condensation. These copolyesters were characterized by viscometry and spectrometry. DSC thermograms were recorded for all the copolyesters to determine the glass transition temperatures (T g ). The acoustical parameters of all the copolyesters were calculated from the measured ultrasonic velocity (U) and density (ρ) values at different temperatures in N,N-dimethylacetamide (DMAc) solution. The glass transition temperature values were determined from the trend in few calculated acoustical parameters with temperature and compared with those obtained from thermograms taken using differential scanning calorimetry. The molecular interactions at T g in the copolyester solutions have been investigated from these studies.