Melt Processing Of Poly Research Articles

Probing into the nucleation and reinforcing effects of poly (vinyl acetate) grafted cellulose nanocrystals in melt-processed poly (lactic acid) nanocomposites

Blending poly (lactic acid) (PLA) with cellulose nanocrystals (CNCs) to fabricate nanocomposites is a valuable strategy to improve the properties of PLA without sacrificing its biodegradability. However, the nucleation and reinforcing mechanisms of CNCs for semi-crystalline PLA matrix are still elusive in melt-processed PLA/CNC nanocomposites. Herein, poly (vinyl acetate) (PVAc) chains were grafted onto the surface of CNCs via an efficient radical polymerization in an aqueous medium, making CNCs suitable for conventional melting processing techniques. It is found that the dispersion state of CNCs in the PLA matrix and the interface interaction between PLA and CNCs can be tailored by varying the PVAc grafting density. Further studies show that well-dispersed CNCs play a positive role in reinforcing PLA. But unexpectedly, the nucleation effect is suppressed even though the homogeneous dispersion of CNCs is achieved with higher PVAc grafting density because the rich PVAc chains at the interface dilute the PLA chains, thus hindering the nucleation and spherulite growth of PLA. This research sheds light on the nucleation and reinforcing mechanisms of polymer grafted CNCs, and will provide theoretical guidance for the industrialization of high-performance bio-based nanocomposites.

Evaluation of the Equilibrium Melting Temperature and Melting Behavior of Poly(Phenylene Sulfide) Crystals.

Focusing on the melting process of poly(phenylene sulfide) (PPS) crystals, one of the high-performance resins with a very wide range of applications, we attempted to clarify the melting process and derive the equilibrium melting temperature with structural analysis using X-ray scattering and thermal measurements. Two melting points were observed in the crystallized PPS films by DSC measurements. We focused on the low-temperature melting point, in situ small-angle and wide-angle X-ray scattering measurements using synchrotron radiation and DSC thermograms indicate the melting of microcrystals because of thickening of the amorphous part from small-angle X-ray scattering results. In addition, the Hoffman-Weeks plot based on the results of fast scanning calorimetry showed that the melting temperature is almost parallel to the straight line where melting temperature and crystallization temperature are equal, indicating that the melting is of a metastable structure. The melting point on the high temperature side was attributed to the melting of lamellar crystals. The equilibrium melting point was derived from the Hoffman-Week and Gibbs-Thomson plots as 318 °C.

Thermoelectric Properties of N-Type Poly (Ether Ether Ketone)/Carbon Nanofiber Melt-Processed Composites.

The thermoelectric properties, at temperatures from 30 °C to 100 °C, of melt-processed poly(ether ether ketone) (PEEK) composites prepared with 10 wt.% of carbon nanofibers (CNFs) are discussed in this work. At 30 °C, the PEEK/CNF composites show an electrical conductivity (σ) of ~27 S m-1 and a Seebeck coefficient (S) of -3.4 μV K-1, which means that their majority charge carriers are electrons. The origin of this negative Seebeck is deduced because of the impurities present in the as-received CNFs, which may cause sharply varying and localized states at approximately 0.086 eV above the Fermi energy level (EF) of CNFs. Moreover, the lower S, in absolute value, found in PEEK/CNF composites, when compared with the S of as-received CNFs (-5.3 μV K-1), is attributed to a slight electron withdrawing from the external layers of CNFs by the PEEK matrix. At temperatures from 30 °C to 100 °C, the σ (T) of PEEK/CNF composites, in contrast to the σ (T) of as-received CNFs, shows a negative temperature effect, understood through the 3D variable-range hopping (VRH) model, as a thermally activated hopping mechanism across a random network of potential wells. Moreover, their nonlinear S (T) follows the same behavior reported before for polypropylene composites melt-processed with similar CNFs at the same interval of temperatures.

Melt-processed poly (vinyl alcohol)/corn starch/nanocellulose composites with improved mechanical properties

Corn starch (CS) and cellulose nanofibrils (CNFs) were incorporated into biodegradable poly (vinyl alcohol) (PVA) to prepare mechanically robust and sustainable composites through melt-processing. Based on the regulation and control of hydrogen bonding network, CS and CNFs can extend the processing window and improve the thermoplasticity of PVA composites. Fourier transform infrared spectroscopy and Raman spectra analysis indicate that the intra- and inter-molecular hydrogen bonds of PVA are broken, accompanied by the formation of new hydrogen bonds among PVA, CS and CNFs during the melt-processing treatment. Thermal analysis shows that the processing window of PVA composite is significantly broadened to 131.46 °C. The tensile strength, modulus and elongation at break of the composites reach to 28.19 MPa, 1572.54 MPa and 10.72% by the incorporation of 10 wt% CS and 10 wt% CNFs. This strategy is not only expected to provide a direction for preparing complex three-dimensional products of PVA by melt-processing, but also provide a method to enhance the mechanical properties of other biodegradable plastics.

Poly(vinyl alcohol)/artificial marble wastes composites with improved melt processability and mechanical properties

The melt-processing of poly(vinyl alcohol) (PVA) is a great challenge due to its melting temperature (Tm) is very close to the initial decomposition temperature (Ti). Herein, artificial marble wastes (AMWs), a kind of calcium carbonate powder coated with unsaturated polyester, are employed as functional fillers into PVA matrix to improve its melt processability. Strong interfacial interaction is established between AMWs and PVA molecules through hydrogen bonding, and the formamide/water compound plasticizer is adopted to facilitate the intermolecular complexation between AMWs and PVA molecules. Benefiting from the nucleation effect of AMWs, the crystallite size of PVA is evidently decreased. As a result, a greatly expanded melt-processing window (Ti -Tm, 76.9 °C) of PVA is realized. The tensile strength of resulting composites is significantly improved by 35.4% with the incorporation of 10 wt% AMWs. We believe that our strategy will enlarge the potential applications of PVA via melt-processing and provide a new insight into the utilization of AMWs in high valuable and high-performance composites.

Kinetic modelling of thermal degradation and non-isothermal crystallization of silk nano-discs reinforced poly (lactic acid) bionanocomposites

The present work investigates the effect of novel biofiller, ‘crystalline silk nano-discs (CSNs)’, on thermal stability and crystallization behaviour of melt-processed poly (lactic acid) (PLA)/CSN nanobiocomposites which are very much important for polymer processing. The PLA/CSN nanobiocomposites are obtained through melt extrusion technique. Thermogravimetric (TGA) data revealed that incorporation of ~ 1 wt.% CSNs in PLA enhanced onset degradation temperature (Tonset) ~ 10 °C, and this improvement in thermal stability is due to the formation of network-like structures. Activation energies (Ea) of nanobiocomposites, determined from model-free (Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose methods) and model fitting (Coats–Redfern method) approaches, increased in comparison with PLA, indicating that CSNs impede thermal degradation process. Possible mechanism is proposed for thermal degradation process of nanobiocomposites using Criado’s method. Hyphenated TGA-Fourier transform infrared is utilized to identify evolved gaseous products during degradation of silk, CSNs, PLA and nanobiocomposites. Differential calorimetry data was analysed by Jeziorny, Liu-Mo and Tobin models. It was found that CSNs act as heterogeneous nucleating agents, hence improve non-isothermal crystallization kinetics of PLA.

Preparation of hydrolysis of poly(acrylonitrile‐co‐methyl acrylate) membranes via thermally induced phase separation: Effects of hydrolysis conditions and additives

ABSTRACTIn this work, melt processable poly(acrylonitrile‐co‐methyl acrylate) [(P(AN‐MA)] was hydrolyzed first and then formed into microporous membrane via thermally induced phase separation. In order to optimize the hydrolysis condition and fabricate hydrophilic PAN‐based membranes, a series of hydrolysis experiments were performed to indicate the influence of hydrolysis temperature, alkaline species and time. The structure and properties of hydrolyzed P(AN‐MA) [H‐P(AN‐MA)] membranes were also investigated. It was found that with the increase of hydrolysis temperature, pure water flux (PWF) increased first and then decreased. When the hydrolysis temperature increased to 30 °C, the PWF of the H‐P(AN‐MA) membrane was up to the maximum of 6712.7 L/m2 h, which increased by 1661.6 L/m2 h, compared with the P(AN‐MA) membranes. When 1 wt % sodium dodecyl sulfate (SDS) was incorporated into the diluents, the PWF increased dramatically, especially in high hydrolysis temperature. When the hydrolysis temperature was up to 70 °C, the PWF of H‐P(AN‐MA) membranes containing 1 wt % SDS increased by 2.3 times compared to the sample without SDS under the same condition. With 2 wt % amino functionalized multi‐walled carbon nanotubes (MWCNTs‐NH2) employed as the additive, the tensile strength was up to 4.55 MPa. When 1 wt % SDS and 0.5 wt % MWCNTs‐NH2 were mixed together, the bovine serum albumin rejection increased from 31.2% to 40.9%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46380.

Hybrid Latex Particles: Preparation with Miniemulsion Polymerization

This research developed a novel poly(trifluoropropylmethylsiloxane) (PTMS)/montmorillonite nanoparticles, for technologic applications. PTMS /MMT nanoparticles were prepared by the miniemulsion polymerization method. Montmorillonite clay was encapsulated within a fluorinated cyclosiloxane (1,3,5-tris(trifluoropropylmethyl)cyclotrisiloxane) to give stable water based nanocomposite latex, using miniemulsion polymerization technique. The resulting composite latex was characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and RX diffraction. The particles stability was investigated by sedimentation and surface tension measurements. An efficient cationic/nonionic surfactant mixture was used in order to achieve the best compatibility with the monomer. TEM and RX data revealed the partial embedding of montmorillonite in the spherical polymer based nanoparticles. According to DLS measurements, the encapsulated clay particles conserve their size throughout the polymerization process. The melt processing of poly(trifluoropropylmethylsiloxane) matrix to encapsulate the montmorillonite clay was also carried out for comparison purposes.

Hybrid Latex Particles: Preparation with Miniemulsion Polymerization

This research developed a novel poly(trifluoropropylmethylsiloxane) (PTMS)/montmorillonite nanoparticles, for technologic applications. PTMS /MMT nanoparticles were prepared by the miniemulsion polymerization method. Montmorillonite clay was encapsulated within a fluorinated cyclosiloxane (1,3,5-tris(trifluoropropylmethyl)cyclotrisiloxane) to give stable water based nanocomposite latex, using miniemulsion polymerization technique. The resulting composite latex was characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and RX diffraction. The particles stability was investigated by sedimentation and surface tension measurements. An efficient cationic/nonionic surfactant mixture was used in order to achieve the best compatibility with the monomer. TEM and RX data revealed the partial embedding of montmorillonite in the spherical polymer based nanoparticles. According to DLS measurements, the encapsulated clay particles conserve their size throughout the polymerization process. The melt processing of poly(trifluoropropylmethylsiloxane) matrix to encapsulate the montmorillonite clay was also carried out for comparison purposes.

Effect of banana fibers and plasticizer on melt processing of poly(vinyl alcohol)

Abstract Poly(vinyl alcohol) (PVOH) resin is one of the most widely used water-soluble biodegradable polymer. Because of thermal degradation, PVOH exhibits limited melt processing and lacks moldability. The effects of adding glycerol as plasticizer and banana fibers (BF) to PVOH on its moldability and mechanical property were investigated. Melt blending of PVOH with glycerol and/or BF was performed in an internal mixer. The blended materials were then compression molded to produce tensile specimens. Various characterization techniques were employed to study the mechanical properties, compatibility, and crystallization behavior of the PVOH blends. By melt blending with glycerol, PVOH could be processed but decreased the tensile modulus, tensile strength, and crystallization temperature. Furthermore, the addition of BF enhanced the mechanical and thermal properties and crystallization temperature of plasticized PVOH due to compatibility between the two components. Apart from enhancing the mechanical properties and thermal stability, the incorporation of BF can reduce the production cost.

Interrelationship of thermal and mechanical properties of poly(ethylene terephthalate)/poly(ethylene 2,6-naphthalate)/graphene nanocomposites

In the present work, attempts were made to investigate the thermal and mechanical properties of melt-processed poly(ethylene terephthalate) (PET)/poly(ethylene 2,6-naphthalate) (PEN) blends and its nanocomposites containing graphene by using differential scanning calorimetry and tensile test experimenting. The results showed that crystallinity, which depends on a blend ratio, completely disappeared in a composition of 50/50. By introducing graphene to PET, even in low concentrations, the crystallinity of samples increased, while the nanocomposite of PEN indicated reverse behavior, and the crystallinity was reduced by adding graphene. In the case of PET-rich (75/25) nanocomposite blends, by increasing the nano content in the blend, the crystallinity of the samples was enhanced. This behavior was attributed to the nucleating effect of graphene particles in the samples. From the results of mechanical experiments, it was found in PET-rich blends that by increasing the PEN/PET ratio, the modulus of samples decreased, whereas in the case of PEN-rich blends, a slight increment of modulus is seen as a result of the increment of the PEN/PET ratio. The two contradicting behaviors were attributed to the reduction of crystallinity of PET-rich blends by enhancement of PEN/PET ratio and the rigid structure of PEN chains in PEN-rich blends. Unlike the different modulus change of PET-rich and PEN-rich blends, the nanocomposites of these blends similarly indicated an increment of modulus and characteristics of rigid materials by increasing the nano content. Furthermore, the same behavior was detected in nanocomposites of each polymer (PET and PEN nanocomposites). The alteration from ductile to rigid conduction was related to the impedance in the role of graphene plates against the flexibility of polymer chains and high values of graphene modulus. J. VINYL ADDIT. TECHNOL., 2015. © 2015 Society of Plastics Engineers

Melt-processed poly(vinyl alcohol) composites filled with microcrystalline cellulose from waste cotton fabrics

Waste cotton fabrics (WCFs), which are generated in a large volume from the textile industry, have caused serious disposal problem. Recycling WCFs into value-added products is one of the vital measures for both environmental and economic benefits. In this study, microcrystalline cellulose (MCC) was prepared by acid hydrolysis of WCFs, and used as reinforcement for melt-processed poly(vinyl alcohol) (PVA) with water and formamide as plasticizer. The microstructure and mechanical properties of the melt-processed PVA/MCC composites were characterized by Fourier transform infrared spectra, Raman spectra, differential scanning calorimetry, thermal gravimetric analysis, X-ray diffraction, tensile tests and dynamic mechanical analysis. The results indicated that MCC could establish strong interfacial interaction with PVA through hydrogen bonding. As a result, the crystallization of PVA was confined and its melting temperature was decreased, which was beneficial for the melt-processing of PVA. Compared with the unfilled PVA, the PVA/MCC composites exhibited remarkable improvement in modulus and tensile strength.

Structures and properties of thermoregulated acrylonitrile–methyl acrylate sheet containing microphase change materials

AbstractA series of melt processable poly(acrylonitrile–methyl acrylate) copolymers with a feeding ratio of 85/15 mol% (abbreviated as 85/15 AN/MA below) containing 0–25 wt% of microencapsulated phase change materials (micro‐PCMs) were synthesized by aqueous precipitation polymerization. The number average sequence lengths (NASLs) and tacticity of 85/15 AN/MA were determined using 13C‐NMR. The results showed that the NASL of contiguous AN sequences is 10.00 and the tacticity is atactic with approximately 51% m and 49% r diads (the relative orientation of two adjacent cyanogroup). 85/15 AN/MA containing various contents of micro‐PCMs were processed into sheets in melt condition at 210°C and 20 MPa. The structures and properties of the copolymers and sheets containing micro‐PCMs were studied by using Fourier transform infrared spectroscopy, nuclear magnetic resonance (1H‐NMR), scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, X‐ray diffraction, and dynamic mechanical analysis. The composition of AN/MA copolymer agreed well with its monomer feed ratio. The melting enthalpy of the sheets containing 25 wt% of micro‐PCMs was approximately 25 J/g, which increased steadily as the micro‐PCMs content increased. The modulus of the sheets decreased with the micro‐PCMs content increased. The glass transition temperature (Tg) of the sheets was in the range of 79.7–81.7°C, which also increased with the micro‐PCMs content increasing. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Properties of melt-processed poly(hydroxybutyrate-co-hydroxyvalerate)/starch 1:1 blend nanocomposites

Melt blending of 1:1 poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and glycerol-plasticized starch (TPS) was performed in the presence of an organically-modified montmorillonite, incorporated at 2.5, 5, 7.5 and 10 wt% amounts. Scanning electron micrographs (SEM) revealed the role of the organoclay as a compatibilizing agent for the immiscible blend. The blends were also characterized by X-ray diffraction (XRD), tensile tests, humidity absorption and soil burial biodegradation tests. The results indicated improved properties of the hybrid materials in relation to TPS alone, with a faster biodegradation rate than PHBV.

Melt processing of poly(vinyl alcohol) through adding magnesium chloride hexahydrate and ethylene glycol as a complex plasticizer

AbstractThe melt processing of poly(vinyl alcohol) (PVA) was achieved using magnesium chloride hexahydrate (MgCl2·6H2O) and ethylene glycol as a complex plasticizer. The interaction between the complex plasticizer and PVA was studied by Fourier transform infrared spectroscopy (FT‐IR). The PVA films were characterized using X‐ray diffraction (XRD), differential scanning calorimetry, thermogravimetric analysis (TGA), scanning electron microscope, and dynamic thermomechanical analysis (DMA) techniques. The band shift of the observed peak around 3335 cm−1 in the FT‐IR spectra indicates that the complex plasticizer MgCl2·6H2O and ethylene glycol could form strong interactions with PVA and thus interrupt the intermolecular and intramolecular hydrogen bonding in PVA. The XRD results show that the addition of the complex plasticizer would significantly destroy the crystallites of PVA and result to the decrease of the degree of crystallinity of PVA. The melting point was reduced from 229°C of pure PVA to around 170°C after the plasticization. The TGA studies show that with the complex plasticizer, the thermal stability of PVA is improved. PVA plasticized by 30 wt% MgCl2·6H2O and 10 wt% ethylene glycol shows the tensile strength of 33 MPa and the elongation at break of 362%. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Gas permeability of melt-processed poly(ether block amide) copolymers and the effects of orientation

Poly(ether block amide) (PEBA) thermoplastic elastomers are used in many different applications, with recent development being on those which show promise as high gas flux membranes. PEBA copolymers with high polyether soft block content are possible candidates for gas separation applications due to their high permeability relative to current commercially used polymers and good selectivity for acid gases such as CO2. To be effective and efficient, the high flux must be maintained over the course of production and use. A series of PEBA copolymers containing poly(tetramethylene oxide) and polyamide-12 was studied to explore the influence of mechanical orientation and copolymer composition on gas permeability and morphology. Upon uniaxial orientation, several compositions of PEBA copolymers exhibited a significant decrease in permeability, both in the oriented and elastically recovered states. Copolymer composition strongly influenced the degree of change seen in the permeability upon orientation. WAXS and DSC were used to identify strain-induced crystallization that occurred during orientation. Rubbery materials can crystallize under high strains, and PEBA is no exception. Strain-induced crystallization of the polyether blocks produced a tortuous path for gas diffusion, resulting in as much as a 3.5× decrease in permeability for oriented PEBA films. To maintain high flux for membrane applications, elastic recovery and thermal treatment proved beneficial in reversing the effects of uniaxial orientation on PEBA copolymers.

Processing of poly(lactic acid)/organomontmorillonite nanocomposites: Microstructure, thermal stability and kinetics of the thermal decomposition

The degradation during the melt processing of poly(lactic acid) (PLA) and its nanocomposites with different contents (0.5 and 2.5%) of an organomodified montmorillonite (OMMT) promoted physical and chemical changes in their properties. Extrusion and injection of PLA/OMMT nanocomposites have been responsible for a decrease in molecular weight. Exfoliation/intercalation phenomena and loss of crystallinity have been detected by means of X-ray diffraction. The thermal stability of the materials has been assessed by thermogravimetric analysis (TG). An integral method based on the general analytical solution as well as differential and special methods have been used to study the kinetics of the thermal decomposition. It has been demonstrated that activation energy had a significant dependence on conversion. The trend of variation has been found to be different for nanocomposites compared to that for the polymer matrix, thus confirming a different competition between the main reaction mechanisms ( cis-elimination and intramolecular transesterification).

Boron nitride by pyrolysis of the melt-processable poly[tris(methylamino)borane]: Structure, composition and oxidation resistance

Evolution of structure and composition of the melt-processable poly[tris(methylamino)borane] (PTMB) during its conversion to ceramics was studied by TGA, FTIR, Raman, XRD, XPS and elemental analysis (EA). The results show that the ceramic yield was greatly improved from 60.22 to 74.4 wt% at 900 °C by curing in NH 3 prior to pyrolysis. The carbon impurity in the precursor can be removed effectively in NH 3 whereas no similar result occurred in N 2. In NH 3, 93 wt% of carbon was removed at 600 °C and the carbon content in the pyrolyzed product at 900 °C was only 0.37 wt%. At the same time, the conversion from polymer to ceramics was almost completed at 900 °C. Moreover, the sample acquired at 900 °C was amorphous boron nitride (BN), while that of further annealing at 1600 °C showed characteristic of turbostratic BN ( t-BN). Additionally, the BN with nearly stoichiometric composition exhibited good oxidation resistance even up to 900 °C in air.

Melt processing of poly(L‐lactic acid) in the presence of organomodified anionic or cationic clays

AbstractPoly(L‐lactic acid) (PLA) films are in use for various types of food packaging; however, a wider range of applications would be possible if the barrier properties of these films could be improved. To make such improvements, combinations of PLA with two nanofillers, laurate‐intercalated Mg‐Al layered double hydroxide (LDH‐C12) and a cationic organomodified montmorillonite (MMT) clay (Cloisite® 30B), were investigated. The dispersion of these fillers in PLA by melt processing was explored using two methods, either by mixing the nanofillers with PLA granulate immediately before extrusion or by preparation and subsequent dilution of PLA‐nanofiller masterbatches. After melt processing of these materials, PLA molecular weight, thermal stability, film transparency, morphology, and permeability characteristics were determined. Direct addition of LDH‐C12 drastically reduced the PLA molecular weight. Although this reduction in molecular weight was still very significant, it was less when a PLA/LDH‐C12 masterbatch was processed. In contrast, there was no significant reduction in PLA molecular weight when processing with Cloisite® 30B. However, film transparency was compromised when either LDH or MMT nanofillers were used. Evidence from DSC analyses showed a significant increase in heat of fusion when LDH‐C12 was dispersed in PLA compared with Cloisite® 30B, likely indicating a difference in nucleating properties. Complementary optical purity analyses suggested that racemization as a result of processing could influence the PLA crystallinity as determined by DSC in certain cases. A reduction in thermal stability when incorporating LDH‐C12 could be a direct result of PLA molecular weight reduction. XRD and TEM analyses showed that both Cloisite® 30B‐ and LDH‐C12‐based PLA composites yielded exfoliated and intercalated morphologies, but nanofiller agglomeration was also seen when LDH‐C12 was used. PLA/Cloisite® 30B nanocomposite films exhibited significant enhancement in oxygen and water vapor barrier properties, but no such improvement was found in PLA/LDH‐C12 nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Investigation of liquid sensing mechanism of poly(lactic acid)/multi-walled carbonnanotube composite films

The liquid sensing mechanism of melt-processed poly(lactic acid) (PLA)/multi-walledcarbon nanotube (MWNT) composite films was investigated for the influence of MWNTloading, solubility parameters of solvents used, solvent transport behaviours, resultantelectrical resistance changes, as well as crystallization of the PLA matrix. Thediffusion, sorption and permeation coefficients of neat PLA and the composites wereestimated, indicating that MWNT network structures block solvent moleculesfrom penetrating into the polymer matrix. Solvent-induced crystallization of thepolymer matrix was observed. Isothermally crystallized composites showed reducedresistances, a significant decrease of sorbed solvent content and a reduction of theresulting resistance changes on the solvent contact. In the context with sensingresults on MWNT mats, it was proposed that the liquid sensing mechanism ofPLA/MWNT composites consists of the overall electrical resistance changes causedby the structural variation of the conductive MWNT network in the polymermatrix and additional interactions between the MWNT and solvent molecules.