Heat of mixing in polymer blends based on poly(vinyl acetate)

Knowledge of the heat of mixing is very important in order to evaluate the interaction parameter, according to the Patterson theory. In this work we illustrate the results regarding some polymer blends, based on poly(vinyl acetate) and some polyacrylates with different substituent groups. In this way it is possible to understand the effect of the lateral group hindrance, as it will be illustrated in the paper.     

Poly(hydroxy ether sulfonamides). A new class of epoxy-based thermoplastics

Base-initiated polymerizations of N,′N-dimethyl-1,3-benzenedisulfonamide or other N,′N-dialkyldisulfonamides with various arylene-diglycidyl ethers afford a broad range of poly(hydroxy ether sulfonamides) (2). Polymers 2, which represent a new family of epoxy-based thermoplastics, are moldable, amorphous materials characterized by moderate T_g (58–127°C) and by good barrier to oxygen, reflected by oxygen transmission rates of 0.45–2.89 cc-mil/100 in²-atm (O2)-day at 234 °C and about 60% relative humidity. In addition to a discussion of how structural changes in the backbones of 2 influence their barrier properties, details of the synthesis, thermal analysis and mechanical evaluation of the polymers are described. © 1996 John Wiley & Sons, Inc.     

Thermal and photochemical stability of poly(methyl methacrylate) and its blends with poly(vinyl acetate)

An investigation of the thermal stability of poly(methyl methacrylate) (PMMA) blends with poly(vinyl acetate) (PVAc) revealed that PVAc acts as a stabilizer as concerns thermal and photochemical degradation when the processes take place in air. The temperatures of decomposition of these blends are higher than that of pure PMMA. The efficiency of photodegradation and photooxidation in the blends is lower than that of pure PMMA.     

Grafting reactions of vinyl acetate onto poly[(vinyl alcohol)-co-(vinyl acetate)]

The grafting preference of vinyl acetate onto the methine carbon of poly(vinyl alcohol) (PVOH) versus the acetate group of poly(vinyl acetate) (PVAc) was determined as part of an attempt to prepare novel branched PVOH from partially hydrolyzed PVAc. The results showed long chain grafting on the acetate groups of the PVAc units rather than the methine carbons of the PVOH or PVAc units. Decreasing the monomer or initiator concentration decreased the molecular weight of the graft copolymer formed. Of the initiators studied, ammonium persulfate gave the largest increase in copolymer molecular weight. Both hydrolysis and reacetylation combined with gel permeation chromatography (GPC) and ¹³C-NMR of the fully hydrolyzed material were used to estimate the number and location of grafts. © 1996 John Wiley & Sons, Inc.     

Photocatalyst‐Free and Blue Light‐Induced RAFT Polymerization of Vinyl Acetate at Ambient Temperature

Vinyl acetate is polymerized in the living way under the irradiation of blue light‐emitting diodes (LEDs) or sunlight without photocatalyst at ambient temperature. 2‐(Ethoxycarbonothioyl)sulfanyl propanoate is exclusively added and acts as initiator and chain transfer agent simultaneously in the current system. Poly(vinyl acetate) with well‐regulated molecular weight and narrow molecular weight distribution (Đ < 1.30) is synthesized. Near quantitative end group fidelity of polymer is demonstrated by nuclear magnetic resonance (NMR) and matrix‐assisteed laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS).

     

Effect of unmodified kraft lignin concentration on the emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid to produce polymer hybrid latex

The introduction of non‐modified kraft LignoBoost® lignin (KL) to produce polymer hybrid latex has received much attention in recent years because it is derived from renewable resources. The focus of this work is to develop a polymer hybrid latex by emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid in the presence of different concentrations of KL furnished by the pulp and paper industry. The study intends to substitute a styrene in the system to understand the effect of non‐modified KL on the properties not only of the latexes, but also on the copolymers themselves. Each polymerization was carried out by shot‐process of tertbutyl hydroperoxide and sodium formaldehyde sulfoxylate as the redox system. The polymer latexes were characterized in relation to overall conversion, particle diameter, particle morphology, coagulum formation, surface tension, zeta potential, and atomic force microscopy. The polymers were evaluated through gel permeation chromatography, water absorption, and thermal properties. The results show that the addition of non‐modified KL results in inhibition of the polymerization and that KL acts as a colloid stabilizer. Small particles were generated in the initial stages of the polymerizations. The presence of the KL altered the color of the latexes; the increase in KL concentration resulted in increase in the absorption of water of the polymer films; the increase in KL concentration resulted in decrease of the molar mass of the copolymers.     

Synthesis and Characterization of Polyindole/Poly(vinyl acetate) Conducting Composites

Composites of a polyindole (PIN) and poly(vinyl acetate) (PVAc) were prepared chemically using FeCl₃ as an oxidant agent in anhydrous media. The composite compositions were altered by varying the indole monomer during preparation. The composites were characterized by FTIR and UV‐visible spectroscopies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), stress‐strain experiments and conductivity measurements. Moreover, the film of PVAc and PIN/PVAc composites were prepared by casting on glass Petri dishes to examine their stress‐strain properties. PIN/PVAc composites are thermally more stable than PIN. It was found that the conductivities of PIN/PVAc composites depend on the indole content in the composites.     

Dielectric investigation of the glass relaxation in poly(vinyl acetate) and poly(vinyl chloride) under high hydrostatic pressure

Measurements of the complex relative permittivity of poly(vinyl acetate) from 35 °C to 190 °C and poly(vinyl chloride) from 90 °C to 150 °C in the frequency range 10^–2 –10⁷ Hz and the pressure range 1–5000 bar are reported. Details of the pressure generating system and of the dielectric equipment are described.     

FT‐IR Investigation into the miscible interactions in new materials for optical devices

In this article we determine the miscibility of azobenzene derivative (poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)₉₀‐co‐(methyl methacrylate)₁₀)/poly(vinyl acetate) (PVAc) and azobenzene derivative/poly(vinyl chloride) (PVC) blends using Fourier Transform infrared (FT‐IR) spectroscopy. With this method we can clearly identify the exact interactions responsible for miscibility. In the azobenzene derivative 50:50PVAc blend new peaks were evident at 2960, 2890, 1237 and 959 cm^?1, these peaks depict miscible interactions. These wavenumbers indicate that the miscible interactions occurring are from the C? H stretching band, the vinyl acetate C?O, conjugated to the ester carbonyl, the cis‐transformation N?N stretch frequency and the acetate ester weak doublet. The azobenzene derivative 80:20PVC blend display peaks identical in profile to the blend homopolymers, indicating no miscible interactions. However, this could be due to overlapping of peaks within the same wavenumber region, making resolution difficult. This research demonstrates FT‐IR can deduce favorable interactions for miscibility and therefore numerous miscible blends can successfully be calculated if possessing the same groups responsible for miscibility. This paves the way for a new generation of designer optical materials with the desired properties. Copyright © 2003 John Wiley & Sons, Ltd.     

聚醋酸乙烯类梳型分散剂的制备与表征

颜料在工业生产和人们的日常生活中起着重要的作用.由于颜料颗粒具有较大的比表面积和较高的比表面能,是热力学不稳定体系,当分散在介质中时容易发生团聚,影响其特性的发挥[1],因此需加入分散剂使其在分散介质中稳定分散.     

聚苯醚磺酸锂与聚醋酸乙烯酯共混物的导电性能研究

为改善聚苯醚磺酸锂（SPPOLi）的导电性能，将聚酷酸乙烯酯（PVAc）与之共混，X-射线衍射分析表明，PVAc可降低SPPOLi凝聚结构的有序程度；发现共混后电导率有了较大提高，共混物的电导对温度的依赖关系不符合阿仑尼马斯方程；同时，共混物仍保持了单离子传导性．     

Frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole–poly(vinyl acetate)

The frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole (PPy) and poly(vinyl acetate) (PVAc) synthesized by FeCl₃‐impregnated PVAc films being dipped into solutions of pyrrole in water was investigated over a frequency range of 100 Hz to 2 MHz and a temperature range of 110–300 K. For specimens with a PPy content less than the percolation threshold, the quantum mechanical tunneling of electrons was the conduction mechanism. For specimens with a higher PPy content, correlated barrier hopping of electrons appeared to be operative. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1935–1941, 2001     

P(VA-co-DBM)/PVA乳胶IPN阻尼材料的合成及动态力学性能

用种子乳液聚合法合成了聚（醋酸乙烯酯－co-马来酸二丁酯）／聚醋酸乙烯酯乳胶互穿聚合物网络阻尼材料,动态力学谱结果表明,该阻尼材料在较宽的温域具有很高的阻尼因子。     

Kinetic study of the thermal decomposition of poly(vinyl alcohol)/kraft lignin derivative blends

A kraft lignin derivative (KLD) obtained by reaction with p-aminobenzoic acid/phthalic anhydride, was blended with poly(vinyl alcohol) (PVA) by solution casting from DMSO. PVA and PVA/KLD films were exposed to ultraviolet radiation (Hg lamp, 96 h) and analyzed by thermogravimetry (TG) in inert and oxidative atmosphere. Typical multi-step decomposition profiles were obtained. The apparent activation energy (E_a) of the thermal degradation of the samples was computed by the Vyazovkin method. The KLD degradation presented only small intervals of decomposition degree with constant E_a values. PVA and blends showed intervals of up to 50% in decomposition degree with nearly constant E_a, and smaller intervals in which E_a varies drastically. The influences of samples irradiation and of surrounding gas in TG analysis on E_a are also shown.     

Viscometric study of poly(vinyl chloride)/poly(vinyl acetate) blends in various solvents

The intermolecular interactions between poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAc) in tetrahydrofuran (THF), methyl ethyl ketone (MEK) and N,N^′-dimethylformamide (DMF) were thoroughly investigated by the viscosity measurement. It has been found that the solvent selected has a great influence upon the polymer-polymer interactions in solution. If using PVAc and THF, or PVAc and DMF to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+THF) or (PVAc+DMF) is less than in corresponding pure solvent of THF or DMF. On the contrary, if using PVAc and MEK to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+MEK) is larger than in pure solvent of MEK. The influence of solvent upon the polymer-polymer interactions also comes from the interaction parameter term Δb, developed from modified Krigbaum and Wall theory. If PVC/PVAc blends with the weight ratio of 1/1 was dissolved in THF or DMF, Δb<0. On the contrary, if PVC/PVAc blends with the same weight ratio was dissolved in MEK, Δb>0. These experimental results show that the compatibility of PVC/PVAc blends is greatly associated with the solvent from which polymer mixtures were cast. The agreement of these results with differential scanning calorimetry measurements of PVC/PVAc blends casting from different solvents is good.     

Thermal degradation of ethylene (vinyl acetate)

Ethylene (vinyl acetate), EVA, is a copolymer which is thermally degraded at high temperatures, with acetic acid release at approximately 620 K. This release can be studied by using thermal methods, and in particular thermogravimetric analysis.The present work was focused on establishing the polymer weight loss with temperature in order to calculate the activation energy of the overall deacetylation process. To obtain the final results, a Mettler TC50 instrument coupled with a Mettler TC11 microprocessor was used.The activation energies of four different industrial EVA formulations were calculated. The results obtained by applying different kinetic methods reported in the literature agreed reasonably well; they were compared in order to select the best method of reporting EVA deacetylation results.The authors wish to express their appreciation to DGICYT (Spain), Project AMB 94-107, for financial support of this study.     

因子分析法和FTIR光谱法研究聚甲基丙烯酸正十八酯和聚醋酸乙烯酯的共混

聚甲基丙烯酸正十八酯[P(n-OMA)]是梳状聚合物,玻璃化温度很低(173K),与其他聚合物共混的热行为的研究需在液氮下进行.本文应用Koenig的因子分析法和FTIR光谱法,在常温下判别了P(n-OMA)与聚醋酸乙烯酯(PVA)的共混相容性,用分峰技术准确定量了它们的相互作用,讨论了影响相互作用的因素。并用DTA谱验证了所得的结论.     

Morphology and permeability of exfoliated PVAc‐MMT nanocomposite films cast from soap‐free emulsion‐polymerized latices

In this study, we exclusively found that the exfoliated poly(vinyl acetate)‐montmorillonite (PVAc‐MMT) nanocomposite latices could be straightforwardly fabricated by soap‐free emulsion polymerization and cast into a film. The as‐fabricated films were transparent with the exfoliated MMT nanoplatelets in flat form uniformly dispersed in the PVAc matrix. Certain bonding of PVAc matrix to the exfoliated MMT nanoplatlets refrained it from removal by acetone in Soxhlet extraction. Exfoliated MMT nanoplatlets (10 wt %) in the film was able to reduce the water vapor permeability coefficient to only 9% that of the neat PVAc. According to the generalized Nielsen's permeability model for the composites containing impermeable fillers in sheet form, the average aspect ratio of exfoliated MMT platelets was calculated as 327, similar to those directly estimated by atomic force microscopy and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5583–5589, 2007