Thermoplastic Poly Vinyl Alcohol Research Articles

Effect of sodium 2‐acrylamido‐2‐methylpropanesulfonate on the structure and properties of thermoplastic polyvinyl alcohol copolymers

AbstractThermoplastic poly(vinyl alcohol) (PVA) with water‐soluble behavior has received great attention. In this work, a thermoplastic PVA was prepared via solution radical polymerization of vinyl acetate, vinyl pivalate and sodium 2‐acrylamido‐2‐methyl propane sulfonate (SAMPS). The effects of SAMPS content on the structure and properties of modified poly(vinyl alcohol) (MPVA) were investigated. On increasing the proportion of SAMPS, the characteristic band of –OH moved to a larger wavenumber. Compared to PVA, the melting temperature (Tm) of MPVA decreased from 223.1 to 161.5 °C at 0.03 mol of SAMPS, and the initial thermal decomposition temperature (Td) of MPVA increased from 244.3 to 262.2 °C at 0.05 mol of SAMPS. The crystallinity of the resin reduced from 51.46% to 10.21%. The enlarged difference between Td and Tm ensured the preparation of MPVA by thermal processing. The maximum tensile strength and elastic modulus of the obtained sheets were 137.56 and 2639.32 MPa, respectively. The introduction of SAMPS reduced the alcoholysis degree from 99.03% to 95.80%. The high alcoholysis degree of MPVA meant that it could be dissolved in water at 60 °C. This type of thermoplastic PVA shows a promising application on film and textiles that require water solubility. © 2024 Society of Chemical Industry.

Thermal oxidation of degradation products from thermoplastic polyvinyl alcohol: Determination on oxidation temperature and residence time

The degradable protective articles made of thermoplastic polyvinyl alcohol (TPVA) are widely used in nuclear power plants, and they are thermally decomposed after use to reduce solid waste. However, in the real decomposition of TPVA, the temperature in the oxidation reactor is not self-sustaining; as a result, the degradation products contain a lot of CO, resulting in more pollution and energy waste. In this paper, jet stirred reactor (JSR) and Chemkin software were used to study the reaction kinetics characteristics of the oxidation process of degradation products from TPVA in the range of 550 °C–700 °C. Both experiments and kinetic simulation show that a higher average temperature of the oxidation reactor is needed to achieve lower CO emissions. When using 5% or 10% TPVA degradation solution, the average temperature should not befall below 625 °C or 675 °C. The corresponding residence time should be greater than 6 s and 5 s respectively. The combination of research findings and engineering practice provides great help to the optimization of the actual work process.

Properties and Structure of Thermoplastic Polyvinyl Alcohol/Polyamide Sea-Island Fibers.

Ultra-fine fibers derived from sea-island fibers have attracted great attention due to their excellent overall performance. However, green and efficient splitting of sea-island fibers is still a challenging task. In this work, thermoplastic polyvinyl alcohol (TPVA) was prepared by the physical blending of plasticizer. The modified TPVA showed a high decomposition temperature (285 °C) and a wide thermoplastic processing window. This made TPVA match well with polyamide 6 (PA6) to form conjugated melts at 250 °C. Corresponding PVA/PA6 sea-island fibers were first reported to realize water-splitting instead of alkali-extraction of "sea" polymers. The effects of sea/island mass ratios and different spinning speeds on the properties of PVA/PA6 sea-island pre-oriented yarn (POY) were investigated. A higher spinning speed enhanced the orientation-induced crystalline behavior of fiber, therefore increasing the tensile strength of fibers. As the increase of spinning speed from 1000 to 1500 m/min, the crystalline degree of corresponding POYs increased from 9.9 to 14.3%. The plasticizer in PVA did not diffuse to the PA matrix during spinning. However, PVA could induce the crystallization of PA6 via interfacial hydrogen bonding. When the spinning speed was 1500 m/min, and PVA/PA6 was 7:3, the tensile strength reached the highest value of 1.67 cN/dtex. The uniform diameters of ultra-fine PA6 fibers (2-5 μm) were obtained by an environment-friendly water-splitting process. The "sea" phase (TPVA) in sea-island fiber could be removed quickly by boiling water treatment in 3 min. This green and energy-saving sea-island fiber splitting technique is of great significance in reducing CO2 emissions during the preparation of super-fine fibers.

Characterization and comparison of properties of cryogenic conditioned CNT reinforced thermoset (epoxy) and thermoplastic (poly vinyl alcohol) composite yarns

Carbon nanotube (CNT) fiber/yarn reinforced composites are considered as a new generation of advanced materials for applications in aerospace and space industry. In this study, two types of CNT composite yarns were produced by twisting CNT films and infiltrating with thermoset epoxy (EP) and thermoplastic poly vinyl alcohol (PVA) resins. The tensile strength of CNT/PVA and CNT/EP composite yarn was 409.91 MPa and 206.87 MPa, much higher than that of pure CNT yarn (129.94 MPa). After mono-cryogenic condition, the mechanical and electrical properties of CNT/EP and CNT/PVA composite yarns were both enhanced due to the structure reorder of the CNT bundles and improvement of interfacial bonding. However, after 60 times cyclic-cryogenic conditions, CNT/EP composite yarn showed a ∼10% degradation of tensile strength; while CNT/PVA composite yarn exhibited 6% increment. This study provides fundamental data of the CNT reinforced thermoset and thermoplastic composite yarns for their practical applications in cryogenic environment.

Preparation and properties of PBAT/PLA composites modified by PVA and cellulose nanocrystals

AbstractCellulose nanocrystal (CNC) was prepared through the hydrolysis of concentrated sulfuric acid using commercial bagasse pulp as a raw material. The performance of the developed CNC was tested through the atomic force microscope, particle size measurement, and zeta potential analysis. The melt blending method was adopted to prepare thermoplastic polyvinyl alcohol (TPVA) and CNC‐TPVA using the glycerol (GI)‐dicondensed triethylene glycol (TEG) complex. The TPVA and CNC‐TPVA were blended with poly(butylene adipate‐coterephthalate) and polylactic acid composite material (COM) through melt extrusion granulation and blown film, and then explored the effect of CNC on the UV aging properties of materials. The complex plasticizer could effectively break the PVA hydrogen bond and reduce its melting point. It had been observed that CNC had good interface compatibility with PVA, and CNC did not affect the crystallinity of PVA, but it could weaken the hydrogen bond between GI, TEG, and PVA, thereby reduce the plasticizing effect of PVA. Compared TPVA‐COM with CNC‐TPVA‐COM, detailed information of crystallization, the thermal stability of materials and mechanical properties was presented in the UV aging process, it was found that the cross‐section of CNC‐TPVA‐COM was rough, and its unevenness formed a striped structure, and its hydrogen bond strength, diffraction peak strength and anti‐aging performance were all improved.

Preparation and Properties of Bio-Based Flame Retardant Polyvinyl Alcohol

Polyvinyl alcohol (PVA) has been widely used in the fields of medical, food and packaging due to its excellent biocompatibility, good fiber-forming and film-forming properties. However, the high flammability of PVA has greatly limited its wider applications. The flame-retardant PVA was prepared by melt blending of a bio-based flame retardant (prepared from lignin, phosphoric acid and carbamide) with thermoplastic PVA (TPVA). The chemical structure, morphology, thermal properties, mechanical properties, fire property and fluidity of this flame retardant PVA were investigated by Fourier transform infrared spectrometer(FTIR), field emission scanning electron microscope(SEM), thermogravimetric analyzer(TGA), impact tester, universal testing machine, horizontal-vertical burning tester, limiting oxygen indexer(LOI) and melt flow rate meter(MFR). The results showed that the prepared flame retardant had good compatibility with the PVA substrate; The impact strength, melt flow rate, fire property and char residue of this PVA material increased with the content of bio-based flame retardant. When the content of flame retardant was of 20%, the five indices including impact strength, melt flow rate, UL-94 level, LOI and char residual were 11.3 KJ/m2, 21.2 g/10 min, V-0 UL-94 level, 33.1%, and 19.2%, respectively. This research can promote the high-value utilization of lignin and the application of PVA in the fields of fire protection.

Rheological and physical properties of a nanocomposite of graphene oxide nanoribbons with polyvinyl alcohol

In this work, the physicochemical and rheological properties of a nanocomposite of graphene oxide (GO) and thermoplastic polyvinyl alcohol (PVA) are reported. After adding deionized water to PVA, the sample was heated and mixed. The polymer solution was divided in two portions, each of them containing PVA in water. GO nanoribbons were added to one portion of the PVA solution in water to obtain the nanocomposite suspension (1% w/w). The similarity of the Fourier-transform infrared spectra of PVA and its related nanocomposite was assessed (both having similar peaks, an important observation as it indicated the water absorption on the samples). The scanning electron microscopy images showed that PVA lost its spherical shape in composites due to the GO sheets coating. The characteristic peaks O− ( m/ e 16) and OH− ( m/ e 17) were observed in the time-of-flight secondary ion mass spectrometry negative mode spectra of PVA and nanocomposite of GO nanoribbons with PVA. The analysis of the OH−, O−, C2H−, and C2− peaks of PVA and the nanocomposite of GO nanoribbons revealed that a reduction occurred for GO nanoribbons when coated with PVA. The rheological behaviors of samples in solution were studied and their shear rate versus shear stress were assessed. A non-Newtonian rheological behavior of the nanocomposite of GO nanoribbons with PVA was observed. The dielectric response of the nanocomposite of GO-PVA featured a simultaneous increase of both real and imaginary part of the complex permittivity toward low frequency due to the contribution of charge carriers. These results provide more understanding about the physical, mechanical, and dielectric properties of GO-PVA nanocomposite to make it appropriate in the construction of embedded capacitors. The novelty of our work lies in the rheological and physical properties of this nanocomposite in comparison with those of PVA that have not been previously reported.

Remarkable Mechanochromism in Blends of a π‐Conjugated Polymer P3TEOT: The Role of Conformational Transitions and Aggregation

AbstractA novel mechanism for well‐pronounced mechanochromism in blends of a π‐conjugated polymer based on reversible conformational transitions of a chromophore rather than caused by its aggregation state, is exemplified. Particularly, a strong stretching‐induced bathochromic shift of the light absorption, or hypsochromic shift of the emission, is found in blends of the water‐soluble poly(3‐tri(ethylene glycol)) (P3TEOT) embedded into the matrix of thermoplastic polyvinyl alcohol. This counterintuitive phenomenon is explained in terms of the concentration dependency of the P3TEOT's aggregation state, which in turn results in different molecular conformations and optical properties. A molecular flexibility, provided by low glass transition temperature of P3TEOT, and the fact that P3TEOT adopts an intermediate, moderately planar conformation in the solid state, are responsible for the unusual complex mechanochromic behavior.

Elongational flow properties of thermoplastic polyvinyl alcohol/polypropylene from the melt spinning method

In this investigation, the blend melts of thermoplastic polyvinyl alcohol (TPVA) and polypropylene (PP) were prepared through melt blending with various blending ratios. The melt spinning method was then adopted to determine and analyze the uniaxial elongational flow properties of the blend melts. First, a melt with a fixed blending ratio (TPVA/PP = 60/40) was selected as the sample to examine the effects of drawing ratios and spinning temperatures on the flow behavior. Experimental results demonstrate that the drawing ratio is the major determinant of elongational flow behavior, while temperature variation exerts little influence on flow behavior. Furthermore, the drawing ratio can also be altered through melt throughputs. The major differences between the samples with different melt throughputs were in the variations of thinning ability and the alteration of melt solidification points, leading to completely different elongation rate ranges. However, the elongation rate ranges increased with the drawing ratio. In addition, the elongation rates were initially close to each other, since the drawing ratio is changed by take up speed with same throughput. Moreover, the experimental data indicate that the elongational flow behavior of blend melts is also influenced by blending ratios. As the blending ratios converged, the elongational resistance decreased, and the elongation rate increased, suggesting a high deformation rate. Conversely, as the differences between blending ratios rose, the elongation rate decreased and the elongational resistance increased, such that the TPVA blending proportion was 20% or 80%. The elongational resistance of TPVA that increases with concave downward, and TPVA/PP blend melts exhibited an inflection in the profile of the elongational resistance versus the elongation rate.

Improving the Processability of Water-soluble Films Based on Filled Thermoplastic Polyvinyl Alcohol

Abstract Melt extrusion of polyvinyl alcohol (PVOH) is desirable over commonly practiced solution film casting due to reduced energy input, environmental footprint, and processing cost, however, melt extrusion processing of plasticized polyvinyl alcohol (PVOH) presents a significant processing challenge due to inherent adhension issues of extruded PVOH film to the surface of equipment. This paper reports a method using inorganic fillers such as CaCO3 and talc to facilitate the plasticized PVOH processing for blown films. Parameters are also identified for additional process studies to optimize the mechanical properties of blown films. It was found that the preferred inorganic filler is CaCO3 for the PVOH stickiness reduction. The filled PVOH films were found to have delayed or reduced water solubility. It takes about 7 to 10 minutes for the filled PVOH films to dissolve in water whereas the neat PVOH films are soluble in water instantly. The delayed water solubility may be desirable for certain specialty applications such as packaging of pesticides during shipping and storage. With improved processability by incorporating filler, the melt extrusion produced PVOH film should cost less than the solution-cast PVOH films.

Mechanochemical activation of cellulose and its thermoplastic polyvinyl alcohol ecocomposites with enhanced physicochemical properties

The focus of this work is to study the influence of mechanochemical treatment of cellulose on the physicochemical properties of its polyvinyl alcohol (PVA) composites. Cellulose fibers subjected to pan-milling could be mechanochemically activated by breaking up the intra- and inter-molecular hydrogen bonds through shearing and compressing forces. Reactive hydroxyl groups were exposed on the cellulose surface, which could establish new hydrogen bonds with PVA. Moreover, the simultaneous reduction of particle size and large increment of specific surface area of pan-milled cellulose would benefit its dispersion as well as the interfacial adhesion with polymer matrix. PVA/cellulose composites were successfully processed by the melt in the presence of plasticizers containing formamide and water. Tensile tests demonstrated positive results from mechanochemical treatment. As pan-milling cycles of cellulose increased, the tensile strength of PVA/cellulose composites increased from 8.8 MPa to 16.4 MPa, while elongation at break increased from 76.8% to 374%. The composite materials also exhibited enhanced thermal stability and better biodegradability.

Shear and elongational flow properties of thermoplastic polyvinyl alcohol melts with different plasticizer contents and degrees of polymerization

In this paper, thermoplastic polyvinyl alcohol (TPVA) was prepared by plasticization using glycerin which has good thermo-resistance and outstanding compatibility with polyvinyl alcohol (PVA). First, the measurements of shear flow properties of TPVA with different plasticizer contents and degrees of polymerization were performed, and the analysis and evaluation of the rheological parameters including non-Newtonian index and flow activation energy were carried out. Results show that both the higher plasticizer contents and the lower degrees of polymerization of TPVA lower the melt viscosity and led to an increase in non-Newtonian index and flow activation energy. Moreover, the change in the plasticizer contents of TPVA had a larger effect on the variation in non-Newtonian index. There was also an obvious variation in the flow activation energy between the samples with different degrees of polymerization. Furthermore, the melt spinning method was used to test the elongational flow properties of TPVA. Test results indicate that the TPVA melts with higher plasticizer contents or lower degrees of polymerization were higher in fiber velocity and elongation rate, but lower in elongational resistance. Moreover, the elongational resistance increased with an increasing elongation rate. Also, it reached a plateau value exhibiting a downward concave curve except the sample with the lowest degree of polymerization that exhibited a slight sigmoid curve.

Shear Flow Properties and Melt Spinning of Thermoplastic Polyvinyl Alcohol Melts

Polyvinyl alcohol (PVA) is a water-soluble polymer, which is difficult to process in melt form owing to its poor processability and thermoplasticity. The thermoplastic polyvinyl alcohol (TPVA) prepared in this study is a brand new material for use in melt spinning. Satisfactory processability of TPVA can be obtained efficiently by using the plasticization method. First, the shear flow properties of TPVA made with various compositions were investigated. The experimental results indicate that, besides decreased viscosity, increased plasticizer loading and decreased degrees of polymerization of TPVA caused a decrease in the non-Newtonian property and increased the temperature sensitivity of the viscosity. Additionally, under the given experimental conditions, all the TPVA melts with various compositions demonstrated satisfactory flowability and spinnability and no melt fracture occurred. With regard to spinability, the TPVA melts displayed decreasing spinnability as the plasticizer loading was increased or the degree of polymerization was decreased. Moreover, the failure of TPVA melts is mainly attributed to ductile rupture. Observation of the WAXD patterns of the TPVA as-spun fibers indicates difficulty in improving the crystallinity and orientation of TPVA, which was due to the addition of plasticizer and the use of partially hydrolyzed PVA. Furthermore, processing under appropriate spinning conditions and avoiding excessively high temperature can maintain considerable water solubility of TPVA, benefiting its application in conjugate spinning

Rheological Properties of Thermoplastic Polyvinyl Alcohol and Polypropylene Blend Melts in Capillary Extrusions

A single screw extruder with a static mixer was used to prepare molten blends of thermoplastic polyvinyl alcohol (TPVA) and polypropylene (PP). The effects of shear rate, blending ratio and temperature on rheological properties for the blends in capillary extrusions were investigated, and ends correction was also carried out. Rheological parameters such as non-Newtonian index and activation energy were also calculated and evaluated. It was found that the viscosities of the blends were lower than those of TPVA and PP; moreover, the non-Newtonian indices and the activation energies of the blend melts were higher than those of the homopolymers. In particular, the blend with 60 wt% TPVA had the highest non-Newtonian indices and activation energies among blend melts. These results indicate that TPVA and PP blends are negative deviation blends. Furthermore, at a blending ratio of 60 wt% of TPVA, the shear-sensitivity of the viscosity was the lowest and the temperature dependence of the viscosity was the highest. In addition, an increase in temperature led to an increase in non-Newtonian index, therefore the shear-rate dependence of the blend viscosities decreased with a rise in temperature. As the shear rate was increased, the variation of the viscosity over blending ratios decreased while the activation energy of the blends decreased. Thus the effects of temperature and blending proportion on flow behavior were diminished by increasing shear rate.