3D printability of highly ductile poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)-EMAA blends

In this work, ionomers were employed to improve the adhesion between 3D printed layers of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG), a commonly used polymer in 3D printing. The printability, rheology, and mechanical properties of PETG were tailored by incorporating poly(ethylene-co-methacrylic acid) neutralized with sodium (EMAA), a soft ionomer. PETG/EMAA polymer blends were prepared by melt extrusion to yield filaments for 3D fused filament fabrication (FFF) printing in different compositions by weight: 70/30, 50/50, and 30/70. The filaments and 3D printed samples were characterized by scanning electron microscopy, rheological and tensile tests. The results revealed that the interaction between PETG and EMAA favored the production of 3D printed samples with enhanced adhesion of layers, ductility, and toughness compared to neat PETG. Increases of 83.5 times in toughness and 86.4 times in ductility were achieved. The blends 30/70 and 50/50 presented the best printability in terms of adhesion between printed layers and mechanical properties.     

Thermal,rheological, mechanical,and dyeing property studies of poly(ethylene‐co‐trimethylene terephthalate) copolymer filaments

The thermal and rheological properties of poly(ethylene‐co‐trimethylene terephthalate) (PETT) copolymer are investigated. The thermal behavior of PETT copolymers is dependent on the composition. The PETT‐15 and PETT‐85 copolymers can crystallize, whereas the PETT‐30 copolymer cannot crystallize at 5°C/min cooling rate. The copolymers have a good thermal stability, even though the addition of poly(trimethylene terephthalate) (PTT) chain causes a disadvantage to the thermal stability of the copolymers. Moreover, the PETT copolymers are a typical pseudoplastic fluid exhibiting shear thinning. With increasing the shear rate or the content of PTT units, the flow activation energy decreases and the sensitivity of the shear viscosity to the melt temperature declines. The PETT copolymer filaments have intermediate elastic recovery and dyeability between poly(ethylene terephthalate) (PET) and PTT filaments. With increasing the PTT content, the elastic recovery and dyeability of PETT copolymer filaments increase. That is to say, introducing PTT units as a minor component into the macromolecular chains is an available means to improve the properties of PET filament. The obtained PETT copolymer filaments blend the advantage of the mechanical property of PET and the elastic and dyeability of PTT filament together into one polymer and possess a softer feeling and a higher extension. POLYM. ENG. SCI., 50:1689–1695, 2010. © 2010 Society of Plastics Engineers     

聚乳酸的成型加工及其降解性能

研究了可生物降解材料－－聚乳酸（PLLA）的流变性能、纺丝成型性能及降解性能,发现PLLA熔体为切力变稀流体,非牛顿指数n=0.93,具有良好的挤出成型性能。同时,通过PLLA纤维和薄膜在不同环境中的降解实验,表明聚乳酸是一种良好的生物降解医用材料和环保塑料。     

Resorbable materials of poly(L-lactide). V. Influence of secondary structure on the mechanical properties and hydrolyzability of poly(L-lactide) fibers produced by a dry-spinning method

Fibers of poly(L -lactide) (PLLA) with a loosened fibrillar structure were produced by solution spinning from a good solvent (chloroform) in the presence of various additives (camphor, polyurethanes). No decrease in mechanical properties was observed as compared with PLLA fibers spun from a good solvent only. In vitro degradation studies showed that the rate of degradation of PLLA fibers with the loosened fibrillar structure was increased approaching that found for fibers composed of the homopolymer of glycolide or copolymers of glycolide and L-lactide. Helices on the fiber surface caused by melt fracture during spinning of the fibers leads to higher knot strengths of the hot-drawn PLLA fiber up to 70% of the tensile strength.     

Polypropylene/poly(ethylene terephthalate) microfibrillar reinforced composites manufactured by fused filament fabrication

In the present work, microfibrillar composites (MFCs) consisting of polypropylene (PP) and poly(ethylene terephthalate) (PET) were successfully produced by melt extrusion and cold stretching. The resulting filaments were then printed using fused filament fabrication. The morphological results demonstrate that the highly oriented PET fibrils after stretching are still well preserved in the printed components. Since the printing process defines the alignment of the fibrils in the final component the fibers can be perfectly adapted to the load paths. Comparative analyses of the mechanical properties reveal that the PET fibrils act as an effective reinforcement in the 3D printed components, resulting in the superior mechanical performance of the PP/PET MFCs compared to a PP/PET blend and a neat PP. Due to the combination of material and innovative processing, the study opens up a new way of using the morphology-based enormous potential of polymer fibers for lightweight, cost-effective and recyclable full polymer solutions in compact components.     

Preparation and Rheological and Mechanical Properties of Poly(butylene succinate)/Talc Composites for Material Extrusion Additive Manufacturing

In this paper, poly(butylene succinate) (PBS) with a low melting point and a similar performance to polyethylene is employed as a printing material; talc is introduced into the matrix to enhance the melt strength of pure PBS during printing. The PBS/talc composite 3D printing filament is prepared by melt extrusion, and the thermal, mechanical, morphological, and rheological properties of the composites are investigated. The results show that the addition of talc to PBS leads to an increase in crystallization temperature. In addition, the tensile and flexural strengths of the injection‐molded specimens increase when the talc concentration increases. However, the mechanical properties of the printed specimens exhibit an opposite variation trend due to their distinct forming process. The printing temperature is 135 °C, which is far lower than those of commercial grade polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) printing filaments. Scanning electron microscopy (SEM) images show that increasing the talc concentration creates better printed formability and well‐organized fracture surface structures. By comparing printed fishbones, the results suggest that the presence of talc leads to a good printing performance with the composite. Furthermore, the rheological results reveal that η^*, G′, and G″ are enhanced by the addition of talc.     

Miscibility and rheological properties of poly(vinyl chloride)/styrene–acrylonitrile blends prepared by melt extrusion

Styrene–acrylonitrile (SAN) with acrylonitrile (AN) concentrations of 11.6–26 wt % and α‐methylstyrene acrylonitrile (αMSAN) with a wide range of AN concentrations are miscible with poly(vinyl chloride) (PVC) through solution blending. Here we examine the rheological properties and miscibility of PVC/SAN and PVC/αMSAN blends prepared by melt extrusion for commercial applications. We have investigated the rheological properties of the blends with a rheometer and a melt indexer. The PVC/SAN and PVC/αMSAN blends have a low melting torque, a long degradation time, and a high melt index, and this means that they have better processability than pure PVC. The miscibility of the blends has been characterized with differential scanning calorimetry, dynamic mechanical thermal analysis, and advanced rheometrics expansion system analysis. The miscibility of the blends has also been characterized with scanning electron microscopy. The SAN series with AN concentrations of 24–31 wt % is immiscible with PVC by melt extrusion, whereas αMSAN with 31 wt % AN is miscible with PVC, even when they are blended by melt extrusion, because of the strong interaction between PVC and αMSAN. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Production of Green Star/Linear PLA Blends by Extrusion and Injection Molding: Tailoring Rheological and Mechanical Performances of Conventional PLA

In this work, bio-based products composed of blends of a star-shaped poly(d ,l -lactide) (star-PDLLA) and a conventional linear poly(l -lactide) (linear-PLLA) are produced by typical large-scale manufacturing techniques for thermoplastic blends. In the first case, the two polymers are blended through melt extrusion, producing pellets that are subsequently compression-molded into the final bio-based polymer films. Alternatively, the star/linear poly(lactide) (PLA) materials are developed by direct blending through injection molding, a process that generally applies after a preblending extrusion step to ensure proper mixing. Thermomechanical degradation induced by the different processes is evaluated, and the performances of the final star/linear PLA products are thoroughly compared. The effect of the short-branched, amorphous, star polymeric component on thermal, mechanical, and rheological properties of the conventional PLLA is comprehensively investigated, revealing that the star-PDLLA incorporation promotes the formation of a more flexible and tougher material with reduced capability of crystallization. Most importantly, star-PDLLA decreases the melt viscosity of the final material, while increasing the shear-thinning behavior, hence facilitating melt flow during manufacturing. Such properties lead to enhanced material ductility and processability, with respect to typically brittle and viscous conventional PLLA-based materials. Moreover, the tuning of final material performances can be achieved by simply varying the star-PDLLA content.     

EPDM Elastomer and Biothermoplastic Polyester-based Silicate-layered Multifunctional Nanocomposites Incorporated with Poly(MA-alt-α-olefin)-g-APTS-SiO2 NPs and PP-g-MA by Reactive Extrusion Nanotechnology

Multifunctional polymer blend nanocomposites consisting EPDM elastomer as a matrix polymer, bioengineering polyesters (PLA and PCL), PP-g-MA compatibilizer and covalently encapsulated colloidal alternating reactive copolymer-g-γ-aminopropyl trimethoxysilane-silica nanoparticles as reactive compatibilizer nanofillers, and organoclay (reactive ODA-MMT and complexable DMDA-MMT) nanofillers were fabricated in melt by a one-step reactive extrusion nanotechnology. The effects of bioengineering polyesters and their molecular mass, origin of organology, and reactive PP-g-MA compatibilizer were evaluated. Unique nanostructures, lower particle sizes and crystallinity, SEM–TEM morphologies, higher thermal behaviors, good mechanical and rheological properties of thermoplastic multifunctional nanocomposites were evaluated.     

Influence of fused filament fabrication parameters on tensile properties of polylactide/layered silicate nanocomposite using response surface methodology

This study aimed at assessing and optimizing the influence of printing speed and extrusion temperature in a fused filament fabrication (FFF) process on the tensile properties of a polylactide/layered silicate nanocomposite. Mathematical models using Doehlert designs were formulated to examine factor and interaction effects. The models were corroborated by measurements using capillary rheology, tomographic images, and crystallinity analyses to find physical explanations for the differences in tensile properties. The tensile properties were a non-monotonic function of printing speed, which may be due to various deposition defects that influence the porosity of composite tensile specimens. This study provides new insights into FFF process optimization regarding rheological behavior and mesostructure of nanocomposite by highlighting new modes of deposition defects that originate from process parameter settings and materials. The results contribute to the properties mastery of FFF-processed materials.     

Structure-property relationships for thermoplastic block terpolymers containing poly(styrene-p-tert-butylstyrene) copolymer end segments

Terpolymers containing polybutadiene as a central segment and diblock or random copolymer terminal units of equimolar amounts of styrene and p-tert-butylstyrene have been synthesized and evaluated. The structure property relationships were examined by a combination of transmission electron microscopy (morphology), dynamic viscoelasticity measurements, and melt rheological evaluations. The presence of p-tert-butylstyrene was found to lead, under certain circumstances, to thermoplastic elastomers exhibiting good phase separation and mechanical properties at ambient temperature along with Newtonian melt viscosities at low shear rates at elevated temperatures. This latter behavior is in contrast with that exhibited by conventional poly(styrene-diene-styrene) triblock copolymers.     

Synthesis,characterization and properties of novel biodegradable multiblock copolymers comprising poly(butylene succinate) and poly(1,2‐propylene terephthalate) with hexamethylene diisocyanate as a chain extender

In this exploration of novel biodegradable polyesters, multiblock copolymers based on poly(butylene succinate) (PBS) and poly(1,2‐propylene terephthalate) (PPT) were successfully synthesized with hexamethylene diisocyanate as a chain extender. The amorphous and rigid PPT segment was chosen to modify PBS. The structures of the polymers were characterized using ¹H NMR and ¹³C NMR spectroscopy, gel permeation chromatography and wide‐angle X‐ray diffraction; the physical properties were investigated using thermogravimetric analysis, differential scanning calorimetry, mechanical testing and enzymatic degradation. The results indicate that the copolymers possess satisfactory mechanical and thermal properties, with impact strength 186% higher than that of PBS homopolymer, while tensile strength, flexural strength, thermal stability and melting point (T_m) are slightly decreased. Crystallization and biodegradation rates are still acceptable at 5 wt% PPT, although they are decreased by the introduction of PPT. The addition of appropriate amounts of PPT can improve the impact strength effectively without an obviously deleterious effect on tensile strength, flexural strength, thermal stability, T_m, crystallization rate and biodegradability. This study describes a convenient route to novel multiblock copolymers comprising crystallizable aliphatic and amorphous aromatic polyesters, which are promising for commercialization as biodegradable materials. Copyright © 2011 Society of Chemical Industry     

Reactive compatibilization and properties of recycled poly(ethylene terephthalate)/polyethylene blends

Summary Blends of recycled poly(ethylene terephthalate) (R-PET) and high-density polyethylene (R-PE), obtained from post-consumer packaging materials, were prepared both by melt mixing and extrusion processes and compatibilized by addition of various copolymers containing functional reactive groups, such as maleic anhydride, acrylic acid and glycidyl methacrylate. The effect of the type and concentration of compatibilizer, as well as the mixing conditions, on the phase morphology, thermal behaviour, rheological and mechanical properties of the blends was investigated. The results indicated that addition (5÷10 pph) of ethylene-co-glycidyl methacrylate copolymer (E-GMA) allows for a marked improvement of processability and physical/mechanical performances of R-PET/R-PE blends. Received: 1 March 2001/Revised version: 15 November 2001/ Accepted: 28 January 2002     

(Nano)Fibrillar morphology development in biobased poly(butylene succinate-co-adipate)/poly(amide-11) blown films

Thin films with (nano)fibrillar morphologies were successfully obtained in fully-biobased poly(butylene succinate-co-adipate)/poly(amide-11) blends (PBSA/PA11, 85/15 wt/wt) using an extrusion-blowing process. Impacts of PA11 grade and take-up ratio on the morphology of PBSA/PA11 were particularly highlighted. Scanning electron microscopy analyses indicated that PA11 with high melt volume-flow rates are beneficial to the development of (nano)fibrillar morphologies in PBSA/PA11 blown film. On the contrary, unstable film blowing processing without fibrillar morphologies was attested for PA11 with low melt volume-flow rates. Increasing the take-up ratio during extrusion-blowing of PBSA/PA11 clearly generates finer PA11 (nano)fibrils into PBSA. Fibril diameters down to 300 nm could be reached with an optimal PA11 grade promoting enhanced mechanical properties (higher ductility and toughness). The formation of stable PA11 (nano)fibrils into PBSA is discussed via rheological assessments of viscosity/elasticity ratio. A specific attention was finally paid to the PBSA strain-hardening behavior in PBSA/PA11 using elongational rheological tests. PA11 (nano)fibrillation helps maintaining the strong PBSA strain-hardening and thus play a major role on the processability of PBSA/PA11 blends by extrusion blowing. As a conclusion, the PA11 grade represents a crucial parameter to control the production of PBSA/PA11 blown films with refined (nano)fibrillar structures and enhanced physico-chemical properties.     

In-line monitoring of the thermal degradation of poly(l-lactic acid) during melt extrusion by UV-vis spectroscopy

Melt processing of poly(l-lactic acid) (PLLA) can lead to both molar mass reduction and colour formation, which can alter properties critical for medical applications (e.g. biodegradation rate). In this work, ultra-violet/visible (UV-vis) spectroscopy was applied to in-line monitor the extrusion of PLLA on a co-rotating twin screw extruder. Molar mass, viscosity and in vitro biodegradation behavior of the extrudates were analyzed off-line. UV-vis spectroscopy turned out to be very sensitive to minute colour changes of the melt. For dry PLLA a clear correlation between increasing UV-vis absorption of the melt and molar mass reduction of the extrudates is found. From the dependence of molar mass reduction on processing conditions it is concluded that thermal degradation dominates. The heat input bases on direct heating and on conversion of mechanical energy. The presence of moisture in the polymer does not significantly influence the UV-vis spectra but contributes to further molar mass reduction. In vitro biodegradation of extruded dry PLLA shows that processing parameters have an influence on the biodegradation behavior. A good correlation between the biodegradation rate of the extrudates and the UV-vis absorption of the melt is found. This investigation demonstrates that UV-vis spectroscopy is powerful for real time detecting the thermal degradation of PLLA during melt extrusion.     

聚乳酸/纳米蒙脱土纳米复合材料的制备与挤出发泡研究

采用熔融插层法制备了聚乳酸/有机改性纳米蒙脱土（PLA/OMMT）复合材料,对其复合结构、力学性能、热性能、动态流变性能进行了测试和表征,并研究了复合材料的挤出发泡行为。结果表明,不同含量的OMMT与PLA进行熔融插层会形成不同的插层与剥离结构;3 %的OMMT可以提高PLA的力学性能、改善热性能;OMMT能够提升PLA的熔体强度,同时在挤出发泡过程中起到成核剂的作用,并且能够减弱发泡剂气体向PLA熔体外部的扩散,从而提高PLA挤出发泡的效果。     

Structure and improved properties of PPC/PBAT blends via controlling phase morphology based on melt viscosity

Poly(propylene carbonate) (PPC)/poly(butylenes adipate-co-terephthalate) (PBAT) blends with various composition ratios were prepared via melt mixing using a twin-screw extruder. The effect of melt viscosities of polymers on mechanical behavior, interfacial interaction, thermal properties, rheological responses, and phase morphology was investigated. Results showed that the phase morphology and properties of PPC/PBAT blends were affected by the composition of the blends and the melt viscosities of the two polymers. Results of tensile tests, FTIR, and dynamic rheological measurement of PBAT-rich blends exhibited a better mechanical properties, intermolecular interactions, and compatibility when compared with PPC-rich blends due to the differences of their melt viscosities. Incorporating of PBAT effectively improved the T_g of PPC and the thermal stability of the blends. The T_c of PPC/PBAT blends markedly increased from 37.5 to 66.8 °C with addition of only 10 wt% PPC, indicating an enhanced crystallization ability of PBAT. The improvement of T_c was helpful for blown film extrusion. SEM microphotographs showed that the size of the dispersed phase particles is much smaller and the distribution is more uniform for PBAT-rich blends, compared with that in PPC-rich blends. The processing stability of blown film extrusion was improved by blending PPC with PBAT. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48924.     

Effects of ultrasonic oscillations on processing behavior and mechanical properties of metallocene‐catalyzed linear low‐density polyethylene/low‐density polyethylene blends

The influences of ultrasonic oscillations on rheological behavior and mechanical properties of metallocene‐catalyzed linear low‐density polyethylene (mLLDPE)/low‐density polyethylene (LDPE) blends were investigated. The experimental results showed that the presence of ultrasonic oscillations can increase the extrusion productivity of mLLDPE/LDPE blends and decrease their die pressure and melt viscosity during extrusion. Incorporation of LDPE increases the critical shear rate for sharkskin formation of extrudate, crystallinity, and mechanical properties of mLLDPE. The processing behavior and mechanical properties of mLLDPE/LDPE blends were further improved in the presence of ultrasonic oscillations during extrusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2522–2527, 2004     

Microscopic morphology,rheological behavior,and mechanical properties of polymers: Recycled acrylonitrile-butadiene-styrene/polybutylene terephthalate blends

In this study, styrene-acrylonitrile-glycidyl methacrylate (SAG) series copolymers were specially designed for producing the recycled acrylonitrile-butadiene-styrene (rABS)/poly(butylene terephthalate) (PBT)/SAG blends, which were prepared through the process of continuous melt blending and batch feeding. The effects of viscosity composition, SAG chemical composition, and SAG content on the morphology, and rheological and mechanical properties of the blends have been investigated. As demonstrated by morphological observation, the variety of viscosity composition of the blends affects the size of dispersed PBT droplets. Moreover, high viscosity of rABS matrix seems to facilitate the formation of smaller dispersed phase size of blends. Various SAG chemical compositions have different stabilities on the morphology of the blends, which affects the deformation, fragmentation, and coalescence of dispersed phase droplets. In addition, a finer phase morphology can be achieved when the density distribution of epoxy group is optimal in SAG copolymer. Rheological characterization manifested that the rheological properties of the blends depends strongly on its composition and structure, while the crosslinking degree is associated with the concentration of reactive groups and extent of reaction. Thereby, the rheological behavior of the blends during processing can be controlled by changing the reactive sequence and adding the quantity of epoxy group. The test on mechanical properties verified that a recycled product with excellent performance can be obtained by altering processing methods and the blends formula, which may be further applied to the 3D printing materials required by fused deposition modeling technology. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48310.     

Synthesis,properties and degradation of polyisobutylene–polyester graft copolymers

The development of copolymers is a promising approach for combining the favorable properties of two polymers and obtaining new properties of the combination. In this work, graft copolymers of polyisobutylene (PIB ) and polycaprolactone or poly(d ,l ‐lactide) were synthesized and studied. Amine‐terminated polyesters were synthesized and were grafted onto an activated PIB backbone synthesized from butyl rubber, a copolymer of isobutylene and 2 mol% isoprene. The polyester content was tuned from 15 to 44 wt% by varying the molar mass of the polyester blocks and the number of molar equivalents used in the grafting reaction. The graft copolymers with higher polyester content underwent nanoscale phase separation, as demonstrated by differential scanning calorimetry and atomic force microscopy imaging. This was found to provide enhanced mechanical properties such as increased tensile strength and Young's modulus relative to the starting rubber or physical blends. Despite the significant polyester content of the graft copolymers and the susceptibility of the polyesters to degradation, the graft copolymers underwent negligible mass loss in 5 mol L^?1 NaOH over a period of eight weeks. These results suggest that polyesters can be incorporated into PIB to tune and enhance its properties, while maintaining high chemical stability. © 2016 Society of Chemical Industry