Rheologic and mechanical properties of multiwalled carbon nanotubes-reinforced poly(trimethylene terephthalate) composites

This paper investigates the rheologic and mechanical properties of melt-blended poly(trimethylene terephthalate) (PTT)/multiwalled carbon nanotube (MWCNT) composites and the effect of acid treatment of MWCNT on these properties. The microstructure of the composites was studied by SEM and TEM in terms of the dispersion state of the nanotubes and the polymer–nanotube interaction. Incorporation of MWCNTs into PTT matrix resulted in an increase in both complex viscosity and moduli than those of neat PTT. A dramatic increase in the melt viscosity of composites observed with loading of MWCNT in the range of 0.5 and 2 wt% showed the formation of interconnected network of MWCNT in the polymer matrix at a rheologic percolation threshold. Acid treatment of MWCNT showed significant effect on the rheologic properties of PTT and led to the enhancement of both complex viscosity and moduli due to strong interfacial interaction between acid-treated MWCNT and PTT matrix. The effect of acid treatment was also evident by mechanical properties of the PTT/MWCNT composites. The untreated MWCNT showed only increase in modulus of PTT matrix; whereas, after acid treatment, both tensile strength and modulus of PTT matrix enhanced significantly.     

Morphology development and size control of poly(trimethylene terephthalate) nanofibers prepared from poly(trimethylene terephthalate)/cellulose acetate butyrate in situ fibrillar composites

Formation of nano-fibrillar composite structures provides an effective method for preparing thermoplastic nanofibers. By mixing two immiscible thermoplastic polymers in a twin screw extruder, poly(trimethylene terephthalate) (PTT) formed nano-fibrillar morphology in cellulose acetate butyrate (CAB) matrix, and then PTT nanofibers were obtained from PTT/CAB in situ fibrillar composites after removing the matrix phase of CAB. Blend ratio, shear rate, and draw ratio were three important parameters in the extrusion process, which could affect the shape and size of nanofibers. By varying the process conditions, average diameter of PTT nanofibers could be controlled in the range of 80–400 nm. Besides this, the mechanism of nano-fibrillar formation in PTT/CAB blends was also studied by collecting samples at different stages in the extruder. The morphology developmental trends of PTT dispersed phase with different blend ratios were nearly the same. From initial to metaphase and later phase development, the PTT dispersed component undergo the formation of sheets, holes, and network structures, then the size reduction and formation of nanofibers.     

Effect of multi-walled carbon nanotubes on mechanical and rheological properties of poly(trimethylene terephthalate)

This paper investigates rheological and mechanical properties of poly(trimethylene terephthalate) (PTT) in presence of multi-walled carbon nanotubes (MWCNTs). Morphological characterization by scanning electron microscope and transmission electron microscope showed uniform distribution of MWCNTs in the PTT matrix. Incorporation of MWCNTs into PTT matrix resulted in higher complex viscosity (η), storage (G′) and loss modulus (G″) than those of neat PTT, especially in low-frequency region. The dramatic increase in melt viscosity of PTT observed upon incorporation of MWCNTs in the range of 0.25–1 wt% could be due to the formation of interconnected network of MWCNTs in the polymer matrix, and thus, this can be regarded as rheological percolation threshold concentration. Cole–Cole plot showed change in slope and also shift in G′ versus G″ plot, which suggested change in microstructure upon MWCNT addition. The reinforcing effect of MWCNTs was also confirmed by dynamic mechanical analysis, where, by adding CNTs, a noticeable increase in storage modulus of PTT was observed. However, addition of MWCNTs showed no significant effect on the tensile properties of PTT due to poor interfacial interaction between CNTs and polymer matrix.     

Electromagnetic interference shielding behavior of poly(trimethylene terephthalate)/multi-walled carbon nanotube composites

Poly(trimethylene terephthalate) [PTT]/multiwalled carbon nanotube [MWCNT] composites having varying amounts of MWCNTs were fabricated with an aim to investigate the potential of such composites as an effective light weight electromagnetic interference (EMI) shielding material in the frequency range of 12.4-18 GHz (Ku-band). PTT/MWCNT composite with shielding effectiveness (SE) of 36-42 dB was obtained at 10% (w/w) MWCNT loading. Shielding mechanism was studied by resolving the total SE into absorption (SE_A) and reflection loss (SE_R). PTT/MWCNT composite showed absorption dominated shielding; thus it can be used as microwave, radar absorbing and stealth material. The effect of MWCNT loadings on electrical conductivity (σ) and dielectric properties of PTT and the correlation among conductivity, tan δ, absorption loss and reflection loss were also studied.     

Electrical conductivity and shielding effectiveness of poly(trimethylene terephthalate)/multiwalled carbon nanotube composites

Poly(trimethylene terephthalate) (PTT)/multiwalled carbon nanotube (MWCNT) composites have been fabricated to evaluate the potential of PTT composites as electromagnetic interference (EMI) shielding material. The room temperature electrical conductivity, complex permittivity, and shielding effectiveness (SE) of PTT/MWCNT composites were studied in the frequency range of 8.2–12.4 GHz (X-band). The dc conductivity (σ) of composites increased with increasing MWCNT loading and a typical percolation behavior was observed at 0.48 vol% MWCNT loading. The highest EMI SE of PTT/MWCNT composites was ~23 decibel (dB) at 4.76 vol% MWCNT loading which suggest that these composites can be used as light weight EMI shielding materials. The correlation among the SE, complex permittivity, and electrical conductivity was also studied. The EMI shielding mechanism of PTT/MWCNT composites was studied by resolving the total EMI SE into absorption and reflection loss.     

Miscibility and melting properties of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) blends

The miscibility and melting properties of binary crystalline blends of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) (PEN/PTT) have been investigated with differential scanning calorimetry (DSC). The glass transition and cold crystallization behaviors indicated that in PEN/PTT blends, there are two different amorphous phases and the PEN/PTT blends are immiscible in the amorphous state. The polymer–polymer interaction parameter, , calculated from equilibrium melting temperature depression of the PEN component was −1.791 × 10⁻⁵ (300 °C), revealing miscibility of PEN/PTT blends in the melt state.     

Alternating-layered spherulites in thin-film poly(trimethylene terephthalate) by stepwise crystallization schemes

Structuring of multi-layered spherulites in aryl polyester of poly(trimethylene terephthalate) (PTT) by stepwise crystallization was attempted. Characterization of feasibility was performed by polarized-light microscopy (POM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). Two- or three-layered spherulites could be developed in PTT by subjecting to stepwise crystallization. Sequence and number of layers in spherulites can be designed by altering the steps of temperatures with proper holding time. Time must be allocated properly in the multiple steps if three different textures are to be structured into one single PTT spherulite by stepwise crystallization. Coexistence of multiple lamellar thicknesses and various degrees of crystal perfection were supported by DSC results. The various crystalline regions of the layered spherulites in PTT develop upon stepwise crystallization exhibit the same unit cell as demonstrated by WAXD crystallographs.     

Thermal stability and thermal degradation kinetics of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) blends

The kinetics of thermal degradation of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) (PEN/PTT) blends with different weight ratio were investigated by thermogravimetry analysis from ambient temperature to 800 °C in flowing nitrogen. The kinetic parameters, including the activation energy E _a, the reaction order n, and the pre-exponential factor ln(Z), of the degradation of the PEN/PTT blends were evaluated by three single heating rate methods and advanced isoconversional method developed by Vyazovkin. The three single heating rate methods used in this work include Friedman, Freeman–Carroll, and Chang method. The effects of the heating rate, the calculation methods, and the content of the PEN component on the thermal stability and degradation kinetic parameters of the PEN/PTT blends were systematically discussed. The PEN/PTT blends which degraded in two distinct stages were stable under nitrogen, also, the maximum rate of weight loss increased linearly with increasing of heating rate and decreased with increasing of PEN content. The obtained kinetics data suggested that the introduction of PEN component increased the activation energy, enhanced the stability of the blend system, and affected the process of degradation of PEN/PTT blend.     

聚磷酸铵阻燃r-PET合金的性能研究

研究了聚磷酸铵(APP)对回收PET(r-PET)合金阻燃性能和力学性能的影响.阻燃和热稳定性结果表明,加入24份APP可使合金阻燃等级达到Ⅴ-0级,受热分解速率降低,残炭量增加且生成的炭层高温热稳定性好.力学性能结果表明,随着APP含量增加,r-PET合金的拉伸强度、弯曲强度和弯曲模量均逐渐增加,但韧性降低.     

Crystal morphology,mechanical property and non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) copolymer binary blends

The crystal morphology, impact strength and nonisothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) (PTT/PEO-MA) copolymer blends were studied by using the polarized optical microscopy, impact tester and differential scanning calorimetry (DSC). Avrami theory modified by Jeziorny, Ozawa and Mo theories were used to study the non-isothermal crystallization kinetics of the blends, respectively. The results suggest that these methods are suitable for analyzing the crystallization kinetics of the PTT/PEO-MA blends. The PEO-MA component, serving as a nucleation agent in blends, can increase the start crystallization temperatures and accelerate the crystallization rate of the blends. The crystal dimensions are predominantly three-dimensional growths, judged from the Avrami exponent n and the Ozawa exponent m, but the spherulites in blends are much smaller than those in pure PTT. The crystallization active energy suggests that the PEO-MA component can make the PTT component easy to crystallize in blends. The blend has the highest Izod impact strength as PEO-MA content is 3wt.%. Considering both the crystallization kinetic analyses results and the crystal morphology of the blends, the modified Avrami method is believed to be the most useful in reflecting the crystallization of the blends.     

Controlled and high throughput fabrication of poly(trimethylene terephthalate) nanofibers via melt extrusion of immiscible blends

Immiscible blends of cellulose acetate butyrate (CAB) and poly(trimethylene terephthalate) (PTT) were melt extruded through a two strand rod die. The extrudates were hot-drawn at the die exit at different draw ratios. PTT fibers were obtained by removal of the CAB matrix from the drawn extrudates, and the morphology evolution of the formed fibers was investigated by scanning electron microscopy. PTT nanofibers with an average diameter of 55 nm were produced by controlling the drawing ratio.     

Crystal morphology, mechanical property and non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) copolymer binary blends

The crystal morphology, impact strength and nonisothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) (PTT/PEO-MA) copolymer blends were studied by using the polarized optical microscopy, impact tester and differential scanning calorimetry (DSC). Avrami theory modified by Jeziorny, Ozawa and Mo theories were used to study the non-isothermal crystallization kinetics of the blends, respectively. The results suggest that these methods are suitable for analyzing the crystallization kinetics of the PTT/PEO-MA blends. The PEO-MA component, serving as a nucleation agent in blends, can increase the start crystallization temperatures and accelerate the crystallization rate of the blends. The crystal dimensions are predominantly three-dimensional growths, judged from the Avrami exponent n and the Ozawa exponent m, but the spherulites in blends are much smaller than those in pure PTT. The crystallization active energy suggests that the PEO-MA component can make the PTT component easy to crystallize in blends. The blend has the highest Izod impact strength as PEO-MA content is 3 wt.%. Considering both the crystallization kinetic analyses results and the crystal morphology of the blends, the modified Avrami method is believed to be the most useful in reflecting the crystallization of the blends.     

The surface characteristics of organoclays and their effect on the properties of poly(trimethylene terephthalate) nanocomposites

Biobased materials developed in conjunction with nanotechnology are poised to achieve a significant presence in the world market for polymeric materials. An example of an engineering polymer that can be partially derived from biomass is poly(trimethylene terephthalate). One of its raw materials, 1,3-propanediol, can be derived from corn sugar. In the present study we used a fully petroleum-based resin as an analog to the biobased material. Five organically modified montmorillonite clays were characterized via moisture uptake studies to determine the hydrophilic/hydrophobic nature of their surfaces. Nanocomposites were produced via melt compounding followed by injection molding with 5 wt.% organoclay loading to determine which modification gave the best balance of mechanical and thermal properties. It was found that the tensile modulus increased by up to 35% and the tensile stress at break by up to 50%. The heat deflection temperature of the nanocomposites versus the neat polymer increased by up to 33 °C. From these results, one organoclay was selected for detailed study over a loading range of 0–5 wt.%. The testing revealed that over this range, changes in the mechanical properties may go through a maximum (e.g. strength) or increase/decrease to a plateau (e.g. modulus, elongation at break). X-ray diffraction and transmission electron microscopy were also used to characterize the nature of the organoclay/polymer interaction. Biobased poly(trimethylene terephthalate)/organoclay nanocomposites are expected to exhibit properties similar to the petroleum-based resin.     

Properties of biocomposites from waste seashells and poly(methyl methacrylate)

The paper presents the preparation of biocomposites from waste seashells as reinforcement and poly(methyl methacrylate), abbreviated as PMMA as the matrix. The used seashells belong to the snow‐white Bahamian species of tiger lucine (Codakia orbicularis) from the Island of Coco Cay. Seashells were grinded and homogenized with poly(methyl methacrylate) powder, with the seashell powder content ranging between 2 and 14 wt%, and finally hot pressed. Morphology of prepared composites was analyzed by scanning electron microscopy, and it was determined that the particle distribution was homogenous with no agglomeration. Mechanical properties (microhardness, compressive strength, Young's modulus) of biocomposite materials produced from different amount of waste seashells in poly (methyl methacrylate) were determined and analyzed. The best overall combination of mechanical properties was achieved when 6 wt% of seashell particles below 50 μm size were added to poly (methyl methacrylate).