Vinyl Acetate Content Research Articles

Effect of Vinyl Acetate, Glass Fibers Contents, and Buffer Space on EVA's Mechanical Property and Shock Absorption Ability.

The aim of the study was to evaluate the mechanical properties and impact absorption capacity of prototype materials comprising ethylene vinyl acetate (EVA) of different hardness reinforced using different amounts of glass fibers (GFs), considering a buffer space. Six prototype materials were made by adding E-GFs (5 and 10 wt%) to EVA with vinyl acetate (VA) contents of 9.4 wt% ("hard" or HA) and 27.5 wt% ("soft" or SO). Durometer hardness and tensile strength tests were performed to evaluate the mechanical properties of the materials. Moreover, an impact test was conducted using a customized pendulum impact tester to assess the impact absorption capacity (with or without a buffer space) of the specimens. The mechanical properties of the prototypes, namely, durometer hardness, Young's modulus, and tensile strength, were significantly higher in the HA group than in the SO group, regardless of the presence or added amount of GFs. The addition of GFs, particularly in a large amount (10 wt%), significantly increased these values. In terms of the impact absorption capacity, the original hardness of the EVA material, that is, its VA content, had a more substantial effect than the presence or absence of GFs and the added amount of GFs. Interestingly, the HA specimens with the buffer space exhibited significantly higher impact absorption capacities than the SO specimens. Meanwhile, the SO specimens without the buffer space exhibited significantly higher impact absorption capacities than the HA specimens. Moreover, regardless of the sample material and impact distance, the buffer space significantly improved impact absorption. In particular, with the buffer space, the impact absorption capacity increased with the added amount of GFs. The basic mechanical properties, including durometer hardness, Young's modulus, and tensile strength, of the EVA prototype were significantly increased by reducing the amount of VA regardless of the presence or added amount of GFs. Adding GFs, particularly in large amounts, significantly increased the values of aforementioned mechanical properties. Impact absorption was significantly affected by the hardness of the original EVA material and enhanced by the addition of the buffer space. The HA specimen had a high shock absorption capacity with the buffer space, and the SO specimen had a high shock absorption capacity without the buffer space. With the buffer space, impact absorption improved with the amount of added GFs.

An alternative filament fabrication method as the basis for 3D-printing personalized implants from elastic ethylene vinyl acetate copolymer

In this work, a novel tool for small-scale filament production is presented. Unlike traditional methods such as hot melt extrusion (HME), the device (i) allows filament manufacturing from small material amounts as low as three grams, (ii) ensures high diameter stability almost independent of the viscoelastic behavior of the polymer melt, and (iii) enables processing of materials with rheological profiles specifically tailored toward fused filament fabrication (FFF). Hence, novel materials, previously difficult to process due to HME limitations, become easily accessible for FFF for the first time. Here, we showcase the production of highly flexible drug-free, and drug-loaded filaments based on ethylene-vinyl acetate polymers with a vinyl acetate content of 28 w% (EVA28) and unprecedented high melt flow rates of up to 400 g/10 min. Owing to their low viscosity, FFF with low print nozzle sizes of 250 μm was achieved for the first time for EVA28. These small nozzle diameters facilitate 3D-printing of high-resolution structures in small-dimensional dosage forms such as subcutaneous implantable drug delivery systems, which can later be used for personalization. Consequently, the material portfolio for FFF is tremendously broadened, allowing material and formulation optimization toward FFF, independent of a preliminary extrusion process.

EVA implants for controlled drug delivery to the inner ear

This study evaluated the potential of poly(ethylene vinyl acetate) (EVA) copolymers as matrix formers in miniaturised implants, allowing to achieve controlled drug delivery into the inner ear. Due to the blood-cochlea barrier, it is impossible to reliably deliver a drug to this tiny and highly sensitive organ in clinical practice. To overcome this bottleneck, different EVA implants were prepared by hot melt extrusion, altering the vinyl acetate content and implant diameter. Dexamethasone was incorporated as a drug with anti-inflammatory and anti-fibrotic activity. Its release was measured into artificial perilymph, and the systems were thoroughly characterised before and after exposure to the medium by optical and scanning electron microscopy, SEM-EDX analysis, DSC, X-ray powder diffraction, X-ray microtomography and texture analysis. Notably, the resulting drug release rates were much higher than from silicone-based implants of similar size. Furthermore, varying the vinyl acetate content allowed for adjusting the desired release patterns effectively: With decreasing vinyl acetate content, the crystallinity of the copolymer increased, and the release rate decreased. Interestingly, the drug was homogeneously distributed as tiny crystals throughout the polymeric matrices. Upon contact with aqueous fluids, water penetrates the implants and dissolves the drug, which subsequently diffuses out of the device. Importantly, no noteworthy system swelling or shrinking was observed for up to 10 months upon exposure to the release medium, irrespective of the EVA grade. Also, the mechanical properties of the implants can be expected to allow for administration into the inner ear of a patient, being neither too flexible nor too rigid.

Influence of vinyl acetate content on the performance of alkyl fumarate copolymers as crude oil flow improvers

Paraffin deposition during waxy crude oil transportation may obstruct the effective flow and pose serious flow assurance issues. Therefore, copolymers are used as flow improvers (FIs) and pour point depressants (PPDs) during chemical treatment programs. The performance of the copolymers is affected by their structure, particularly by the proportion of polar and non-polar segments. Fumarate copolymers are promising PPDs and FIs for waxy crude oils. However, research on the impact of different molar ratios of polar to non-polar units is limited. In this study, dialkyl fumarate–vinyl acetate copolymers with similar molar weights but different comonomer ratios were synthesized. Rheological tests of Akshabulak crude oil doped with the prepared additives and pour point measurements revealed that the efficiency of the synthesized FIs depended on the vinyl acetate content. The most effective performance was achieved from the copolymer with 58–59% (mol) of vinyl acetate. Thus, the efficiency of crude-oil FIs based on alkyl fumarate copolymers can be improved by changing the monomer ratio.

Molecular dynamics study of free volume coalescence around nonyl ethoxylate in polyethylene with vinyl acetate‐modified branches

AbstractPolyethylene (PE) is susceptible to environmental stress cracking (ESC). In the presence of an amphiphilic compound and subjected to stress, ESC starts with cavitation followed by slow crack growth and ends with brittle fracture. In this study, we used molecular dynamics simulation to study how branch ends which were chemically modified with vinyl acetate groups affect free volume coalescence around an amphiphilic compound, nonyl ethoxylate (NE), dispersed in branched PE models. Branch ends modified with vinyl acetate significantly impact the free volume coalescence dynamics around NE. Compared with methyl branch ends, vinyl acetate branch ends show a much higher affinity, as quantified by the corresponding radial distribution functions, for the hydrophilic ethylene oxide‐segment of NE. However, this is not the case for the hydrophobic ethylene‐segment. Interestingly, vinyl acetate branch ends tend to reduce the power (amplitude) of the free volume size fluctuations around both the ethylene oxide‐ and ethylene‐segments. Indeed, the powers of the fluctuations with different PE branching characteristics decrease with increasing vinyl acetate concentration. We believe that free volume coalescence leads to cavitation and that vinyl acetate branches could inhibit cavitation, thereby crack propagation in PE. The power results seem to be consistent with the experimental observation that the addition of copolymer ethylene vinyl acetate to low‐density polyethylene improves the ESC resistance of the blend.Highlights Vinyl acetate branches reduce free volume coalescence activities. Vinyl acetate branches are attracted to the hydrophilic segment of NE. Cavitation likely starts from the free volume coalescence around NE.

Characteristics and Challenges of Poly(ethylene-co-vinyl acetate) Solution Electrospinning.

Poly(ethylene-co-vinyl acetate) (PEVA) is a versatile elastic, durable, and biocompatible copolymer, which can be processed by melt extrusion or solvent casting, while electrospinning has been reported as challenging. Here, a spinnability window should be identified using a total of 10 different PEVA materials with increasing vinyl acetate content (∼12-40 wt %) and molecular weights (∼60-130 kDa). Based on the solubility predictions by calculating Hansen solubility parameters, candidate solvents were experimentally evaluated. Spinning experiments with systematic alteration of solution composition and processing parameters revealed the causes of material deposition at the spraying nozzle and multijet spinning characteristics. By introducing a spinnability score that accounts for product characteristics and reproducibility, the spinnability of PEVA could be rationalized. Overall, it was demonstrated that PEVA solutions with an apparent viscosity of 920-3500 mPa·s can be spun to bead-free fibers of ∼10 μm. This size may allow suspension electrospinning of composite fibers in the future.

Advanced analysis of ethylene vinyl acetate copolymer materials for photovoltaic modules

Ethylene vinyl acetate (EVA) copolymers are commonly used as encapsulation material and as adhesive layer for backsheet laminates of photovoltaic (PV) modules. While Fourier-Transform Infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) are well established to analyse EVA encapsulants in PV modules, X-ray Photoelectron Spectroscopy (XPS) is seldomly used. Hence, the objective of this paper was to evaluate the potential and limitations of XPS for advanced analysis and testing of EVA encapsulants. Consequently, EVA grades of different vinyl acetate (VA) comonomer content were characterized and evaluated systematically by XPS, FTIR and DSC. Independent on the analytic technique linear relationships between the obtained values and VA contents were confirmed. Slightly higher VA contents on the surface deduced by XPS were attributed to a surface layer rich of amorphous phase material. In addition, XPS analysis of peroxide modified encapsulants with a VA comonomer content of 30.2 wt% revealed a higher carbon content on the surface after crosslinking. Hence, it is proposed that peroxide crosslinking is associated with deacetylation and the subsequent release of low molar mass decomposition products. Overall, the exceptional surface sensitivity of XPS was clearly confirmed for analysis and testing of EVA grades, highlighting the potential of the method for further degradation and interaction studies of components of PV modules.

Enhanced physico-mechanical properties of EVA/PA blends via electron beam irradiation and vinyl acetate content

Enhanced physico-mechanical properties of EVA/PA blends via electron beam irradiation and vinyl acetate content

Segmental interactions, interfacial polarization, and gigantic dielectric permittivity in ethylene vinyl acetate copolymer‐carbon nanotube composites

AbstractThis study reports copolymer composition tailored wrapping of carbon nanotubes, leading to a gigantic dielectric permittivity and peculiar nonlinear rheological response in a nonfluoro copolymer/carbon nanotube (CNT) hybrid system. Specifically, we observed a strong interfacial polarization effect in ethylene vinyl acetate (EVAc) copolymer/CNT nanocomposites, resulting in a dielectric permittivity of approximately 4000 at 10 Hz and 450 (dielectric loss <1) at 1 kHz, with only 1% volume fraction of CNTs and 40% vinyl acetate (VAc) content. No such effect was observed in EVAc with 12% VAc. Extensive amplitude oscillatory rheology studies prompted us to propose a novel hook‐wrap‐type mechanism, wherein polar interactions act as hooks and nonpolar segments allow wrapping, depending on the optimal interactions between the CNT and copolymer. Raman spectroscopy, small‐angle x‐ray scattering, and relaxation studies also revealed a significant change in segmental dynamics and mass fractal compactness with a change in the VAc content. This work provides a melt processing‐based scalable route to develop polymer dielectrics while advancing the fundamental understanding of polymer‐CNT interactions and the underlying mechanisms of dielectric behavior in nanocomposites.

Performance analysis of a hyper-compressor for vinyl acetate and ethylene mixture using real-fluid properties

The ethylene and vinyl acetate (VA) mixture must be compressed to a high pressure of over 100 MPa in a hyper-compressor system to initiate the polymerization. This paper presents a numerical and experimental investigation into the effects of VA concentration on the performance of a hyper-compressor. To this end, an equation of state in the form of Helmholtz free energy was developed to calculate the real thermodynamic properties of VA–ethylene mixture. The average absolute deviations of density and compressibility factor for VA-ethylene compared with experimental values were 1.82% and 1.46%, respectively. Additionally, a three-dimensional (3D) computational fluid dynamics (CFD) model was constructed considering real-fluid thermodynamics, incorporating the motion of the central valve and upstream and downstream pressure pulsations. The predicted [Formula: see text] diagram and pressure pulsation were compared with experimental data to validate the accuracy of the 3D-CFD model. The results demonstrated that a higher VA weight fraction results in a shorter expansion and compression phase; higher indicated power, suction, and discharge losses; and greater pressure fluctuation. The increment of power loss during the discharge process accounted for 73.27% of the indicated power growth 35.96 kW as the VA weight fraction increased from 0% to 40%. The increment of pressure pulsation in the suction and discharge pipe were mainly attributed to high-frequency pulsations above 10 orders and low-frequency pulsations below 10 orders, respectively.

Assessment of the effect of accelerated ultraviolet aging on mini‐PV modules encapsulated with different poly(ethylene‐co‐vinyl acetate) formulations

AbstractOne of the hindering issues for the long‐term reliability of the photovoltaic (PV) modules is the degradation of poly(ethylene‐co‐vinyl acetate) (PEVA)—a popular encapsulant material. As a globally accepted practice, PEVA is required to have the vinyl acetate (VA) content between 28–33% by weight for encapsulation application in the PV modules. Recent studies have indicated stability improvements in the bare encapsulant layer when the VA content is reduced up to 18%. However, effect of UV aging on the PEVA films encapsulated using these VA contents have not been studied at the module level. Therefore, in this work, we have fabricated mini‐modules containing PEVA films that contain 18, 24 or 33% VA content and have subsequently been subjected to UV aging (1000 hours at 340 nm wavelength and 65C). The assessment of the durability at both the mini‐module and materials level has been made using various characterization techniques such as current–voltage characteristics, adhesion strength measurement, fluorescence imaging and spectra, FTIR, Raman spectra, volume resistivity and TGA. YI for the free‐standing films of PEVA18, PEVA24 and PEVA33 after 1000 hours of UV aging was slightly less than the YI values for the corresponding laminated films of PEVAs in mini‐PV modules after similar hours of aging. This work shows for the first time that increasing the VA content in PEVA increases the fluorescence intensity and contour size in the encapsulated polymer after UV aging. FTIR analysis indicates deacetylation of PEVA33 which resulted in discoloration (increased ΔYI) and has adversely affected the adhesion strength and power output after UV aging. Compared to PEVA33, the modules containing PEVA18 and PEVA24 are resilient against UV aging for all the properties. Hence, this study recommends using PEVA with 24% VA content as an encapsulant as it presents best combination of the adhesion strength and the environmental stability.

Personalization of Complex Vaginal Inserts of Ethylene Vinyl Acetate via 3D‐Printing

AbstractEthylene vinyl acetate (EVA) with a vinyl acetate (VA) content of 28 wt.% (EVA28) is frequently used in vaginal inserts and subcutaneous implants due to its biocompatibility and drug‐releasing properties. Traditionally being processed via hot melt extrusion, its processibility via filament‐based 3D‐printing was reported to be impossible. Consequently, no applicable customization concepts for vaginal inserts exist. For the first time, the fabrication of 3D‐printed vaginal inserts (urethra pessaries) of EVA28 is demonstrated by optimizing its viscosity, employing 3D‐printer adaptations, and carefully selecting printing parameters. The infill pattern of fully filled mono‐material pessaries (determining the number and orientation of weld lines) significantly affects the in vitro release of the model drug progesterone (P4), while other critical parameters (the pessary's mechanical properties and appearance) remain unaffected. Weld lines act as diffusion barriers for dissolved P4 molecules. Hence, a high number of weld lines to be crossed reduces the overall P4 diffusivity in EVA28, decreasing the P4 release rate. To further control the P4 release, innovative multi‐material pessary designs (additionally comprising EVA with a VA content of 9 wt.% that is also used in vaginal inserts) allow to tailor the in vitro drug release and the mechanics individually. Thereby, this work highly improves the mechanistic understanding on drug release modifications from 3D‐printed non‐biodegradable devices. The findings build the basis for the first application of customized vaginal inserts, as they are based on polymers used in corresponding marketed products for more than 20 years.

Tailoring the performance of poly(lactic acid)‐based reactive blends: The effect of vinyl acetate and dicumyl peroxide content

AbstractPoly(lactic acid) has been gaining prominence in academia and industry, mainly due to being a biopolymer and biodegradable material. Nevertheless, mainly due to its high fragility, work has been carried out in order to seek alternatives to improve this drawback. Hence, this work aims to evaluate the effect of the vinyl acetate content using two types of EVA (EVA1 with 28% and EVA2 with 19%) in dynamically vulcanized PLA/EVA blends, using several dicumyl peroxide (DCP) contents, that is, 0.3, 0.5, and 0.7 phr. Blends were produced using an internal mixer, and the tensile, impact and HDT specimens were injection molded. By FTIR and torque rheometry, it was verified that, upon DCP addition, there was evidences of reticulation, resulting in crosslinked PLA, crosslinked EVA, as well as PLA‐g‐EVA. Through tensile and impact strength tests, it was observed substantial increases in the elongation at break, and in impact strength, mainly for the compounds with higher content of vinyl acetate (EVA1). Impact specimens made with PLA/EVA120 0.7 DCP, PLA/EVA130 0.5 DCP, and 0.7 DCP, did not completely break, due to the probable development of the in situ PLA‐g‐EVA compatibilizer among the present phases. Therefore, it is believed that a more homogeneous microstructure was obtained, as observed by SEM images, highlighted upon the DCP content increase. It was verified that the highest vinyl acetate content is of paramount importance for obtaining PLA/EVA blends with better compatibility as well as EVA1 being more susceptible to crosslinking using DCP, resulting in blends with greater toughness.

Influence of Vinyl Acetate Content and Melt Flow Index of Ethylene-Vinyl Acetate Copolymer on Physico-Mechanical and Physico-Chemical Properties of Highly Filled Biocomposites.

Highly filled biocomposites may be used as biodegradable masterbatches that manufacturers add to traditional polymers for making plastic goods more biodegradable. Biocomposites based on various trademarks of ethylene-vinyl acetate copolymer (EVA) and natural vegetable fillers (wood flour and microcrystalline cellulose) were studied. The EVA trademarks differed both in terms of the melt flow index and in the content of vinyl acetate groups. The composites were created as superconcentrates (or masterbatches) for the production of biodegradable materials based on vegetable fillers with polyolefin matrices. The filler content in biocomposites was 50, 60, 70 wt.%. The influence of the content of vinyl acetate in the copolymer and its melt flow index on the physico-mechanical and rheological properties of highly filled biocomposites was evaluated. As a result, one EVA trademark with high molecular weight that has a high content of VA was chosen because of its optimal parameters for creating highly filled composites with natural fillers.

Investigation of the Rheological Properties and Storage Stability of Waste Polyethylene/Ethylene-Vinyl Acetate-Modified Asphalt with Crosslinking and a Silicone Coupling Agent.

As the market for polyethylene consumption continues to expand, the amount of waste polyethylene is also increasing. Modifying asphalt with waste polyethylene (PE) is economical and environmentally friendly. The low-temperature performance and storage stability of PE-modified asphalt has long been an insurmountable problem. The high vinyl acetate (VA) content of ethylene-vinyl acetate (EVA) and PE blended into asphalt can improve the compatibility of PE and asphalt. It compensates for the high VA content of EVA brought about by the lack of high-temperature resistance to permanent deformation but is still not conducive to the stable storage of PE at high temperatures. The effect of furfural extraction oil, a crosslinking (DCP) agent, a silicone coupling agent (KH-570), and calcium carbonate (CaCO3) on the rheological properties and compatibility of PE/EVA-modified asphalt was investigated in this study. The conventional physical properties of PE/EVA-modified asphalt were tested after introducing furfural extraction oil, DCP, KH570, and CaCO3 to determine the correlations of these materials. In addition, frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS) were utilized to characterize the rheological properties and fatigue behavior. The results reveal that the addition of suitable ratios of furfural extract oil, DCP, KH-570, and CaCO3 to PE/EVA-modified asphalt produces a remarkable improvement in the viscoelastic characteristics and viscosity compared with PE/EVA-modified asphalt. Furthermore, fluorescence microscopy (FM) was utilized to evaluate the modification mechanism, which shows that PE/EVA undergoes significant crosslinking in asphalt, forming a three-dimensional network structure that dissolves in the asphalt. The storage stability of the PE-modified bitumen was fully determined, and its high-temperature rheology was substantially improved.

Thermomechanical Properties of Cross-Linked EVA: A Holistic Approach

Cross-linked ethylene–vinyl acetate (EVA) is used in technically demanding applications ranging from solar cell encapsulants exposed to years of harsh environments to athletic shoes exposed to countless impact recovery cycles. The thermomechanical properties of this versatile material represent the combined responses of semicrystalline and elastomeric components. To fully describe structure–property relations of cross-linked EVA, it is necessary to explore the combined effects of vinyl acetate content, molecular weight, and chain topology on the thermomechanical properties. The interdependent effects of these factors influence both the amount of crystallinity and the size of the crystallites within the material. Subsequent cross-linking of EVA reduces crystallinity relative to the un-cross-linked starting materials. By controlling the properties of the un-cross-linked starting materials and the degree of cross-linking, it is possible to tune the performance properties of the cross-linked EVA. Understanding these effects enables material selection and property adjustment to meet the demands of existing and emerging applications.

Intrinsically Heat Tolerant, UV Resistant EVA/ LDPE thermoplastic elastomeric encapsulant – An alternative for conventional crystalline silicon PV module encapsulant

28% vinyl acetate content Ethylene Vinyl Acetate copolymer (EVA) and Low Density Polyethylene (LDPE) blend is a newly developed thermoplastic elastomeric encapsulating system for silicon Photovoltaic (PV) module. Differential scanning calorimetry (DSC) studies has been revealed the inter-miscibility nature of these two polymers blend in the amorphous zones. Thermogravimetric analysis (TGA) result confirms that the EVA-LDPE blend is more thermal stable than the pristine EVA. Encapsulation provides electrical insulation between the solar cells and the electrical circuit of the PV module. Electrical insulation property in terms of DC surface resistivity (SR) and DC volume resistivity (VR) were studied. Insulation property of EVA-LDPE blends under UV radiation has been explored in this article and the change in insulation property has been correlated with the degradation factors. Accelerated UV ageing was performed as per cycle 2 of ASTM G 154 – 2016 for 1000 hours. The thermal resistance and electrical insulation properties were significantly reduced for pristine EVA after 1000 hours UV ageing while >52% property retention found for EVA-LDPE blend.

CFD modeling of the ethylene–vinyl acetate copolymerization autoclave reactor: Effects of comonomer ratio on reactor dynamics and copolymer properties

Computational fluid dynamics (CFD) modeling of an industrial ethylene–vinyl acetate autoclave copolymerization reactor was conducted to evaluate the effects of comonomer ratios on reactor dynamics and product properties, including the molecular weight distribution (MWD), and copolymer composition. To accurately predict the MWD of copolymer chains under highly nonideal mixing conditions at a reduced computational cost, the CFD-multicompartment model and probability generating function (PGF) transform were applied. The effectiveness of the developed model was validated by the satisfactorily consistent plant data and simulated results. The model revealed that an increase in the vinyl acetate (VA) content significantly decreased the temperature, promoting combinational termination and chain transfer to polymer reaction for a broad copolymer MWD. The pseudo-kinetic-based analysis showed that VA was consumed more slowly than ethylene, resulting in its lower value in the copolymer composition than that of the comonomer ratios. However, despite nonideal mixing, the copolymer composition was maintained to be uniform for the copolymers produced over the entire reactor volume. In conclusion, the proposed model can be used to understand the governing behaviors of copolymerization under nonideal mixing conditions, design commercial copolymerization reactors, and predict copolymer product qualities.

Ethylene-Vinyl Acetate Copolymers as Potential Thermoplastic Modifiers of Photopolymer Compositions.

The possibility of using thermoplastic polymers in photopolymer compositions for SLA and DLP is discussed in this article. The diffusion and mutual solubility of uncured systems based on tert-butyl acrylate (tBA) and ethylene-vinyl acetate copolymers (EVA) or low-density polyethylene (LDPE) were studied. The solubility and diffusion of tBA with EVA containing 7, 20, and 40 wt.% vinyl acetate (VA) and with LDPE in the temperature range 20-75 °C were studied by optical micro-interferometry method. Phase diagrams of LDPE-tBA, EVA-7-tBA, and EVA-20-tBA systems were obtained. It is shown that the compositions are characterized by the phase-state diagrams of amorphous separation with the upper critical solution temperature (UCST). The concentration dependences of the interdiffusion coefficients as well as dependences of the self-diffusion coefficients on VA content and on temperature were plotted. The activation energy of self-diffusion of EVA and LDPE was calculated. It was shown that the most promising tBA modifier is EVA-40, which is completely soluble at all studied temperature ranges. The obtained data on the mixing of the initial components is valuable for further studies of the processes of structure formation during photocuring of compositions, regulation of the phase structure and, as a consequence, the performance characteristics of the 3D printable materials.

Processing Properties and Thermal Stability of Poly(vinyl chloride‐co‐vinyl acetate) by Experiments and Molecular Dynamics Simulations

AbstractThe effects of copolymerized monomer vinyl acetate (VAc) on processing properties and thermal stability of poly(vinyl chloride‐co‐vinyl acetate) (PVCA) are investigated via experiment and molecular dynamics simulation. Experimental results showed that PVCA with higher VAc content has larger loss tangent (tanδ), lower complex viscosity (η*), and glass transition temperature (Tg), which improved the processing properties of PVCA. A series of PVCA models are constructed to study the microstructure on the processing properties of PVCA, and the results showed the PVCA with higher VAc content exhibits larger molecular chain mobility and free volume fraction (FFV), smaller intermolecular interactions, and the mean square end‐to‐end distance (<Ree2>). Furthermore, the IR spectra of gas products indicated that thermal degradation of PVCA mainly generated hydrogen chloride (HCl), carboxylic acid, and aliphatic hydrocarbons between 200 and 500 °C, and the removal of HCl and carboxylic acid is almost simultaneous. The degradation models of PVCA chains demonstrated the CCl bond in vinyl chloride (VC) and CO bond in VAc have similar thermal stability, which corresponded to the experimental results. In a word, the work provides a promising technique to study the structure and property of PVCA at molecular dynamic level.