Graft polymerization of vinyl acetate onto starch. Saponification to starch–g–poly(vinyl alcohol)

Graft polymerizations of vinyl acetate onto granular corn starch were initiated by cobalt-60 irradiation of starch-monomer-water mixtures, and ungrafted poly(vinylacetate) was separated from the graft copolymer by benzene extraction. Conversions of monomer to polymer were quantitative at a radiation dose of 1.0 Mrad. However, over half of the polymer was present as ungrafted poly-(vinyl acetate) (grafting efficiency less than 50%), and the graft copolymer contained only 34% grafted synthetic polymer (34% add-on). Lower irradiation doses produced lower conversions of monomer to polymer and gave graft copolymers with lower % add-on. Addition of minor amounts of acrylamide, methyl acrylate, and methacrylic acid as comonomers produced only small increases in % add-on and grafting efficiency. However, grafting efficiency was increased to 70% when a monomer mixture containing about 10% methyl methacrylate was used. Grafting efficiency could be increased to over 90% if the graft polymerization of vinyl acetate-methyl methacrylate was carried out near 0°C, although conversion of monomers to polymer was low and grafted polymer contained 40-50% poly(methyl methacrylate). Selected graft copolymers were treated with methanolic sodium hydroxide to convert starch–g–poly(vinyl acetate) to starch–g–poly(vinyl alcohol). The molecular weight of the poly(vinyl alcohol) moiety was about 30,000. The solubility of starch–g–poly(vinyl alcohol) in hot water was less than 50%; however, solubility could be increased by substituting either acid-modified or hypochlorite-oxidized starch for unmodified starch in the graft polymerization reaction. Vinyl acetate was also graft polymerized onto acid-modified starch which had been dispersed and partially solubilized by heating in water. A total irradiation dose of either 1.0 or 0.5 Mrad gave starch–g–poly(vinyl acetate) with about 35% add-on, and a grafting efficiency of about 40% was obtained. A film cast from a starch–g–poly(vinyl alcohol) copolymer in which homopolymer was not removed exhibited a higher ultimate tensile strength than a comparable physical mixture of starch and poly(vinyl alcohol).     

Amphiphilic poly(vinyl chloride)‐g‐poly[poly(ethylene glycol) methylether methacrylate] copolymer for the surface hydrophilicity modification of poly(vinylidene fluoride) membrane

In this study, a comblike amphiphilic graft copolymer containing poly(vinyl chloride) (PVC) backbones and poly(oxyethylene methacrylate) [poly(ethylene glycol) methylether methacrylate (PEGMA)] side chains was facilely synthesized via an atom transfer radical polymerization method. Secondary chlorines in PVC were used as initial sites to graft a poly[poly(ethylene glycol) methylether methacrylate] [P(PEGMA)] brush. The synthesized PVC‐g‐P(PEGMA) graft copolymer served as an efficient additive for the hydrophilicity modification of the poly(vinylidene fluoride) (PVDF) membrane via a nonsolvent‐induced phase‐inversion technique. A larger pore size, higher porosity, and better connectivity were obtained for the modified PVDF membrane; this facilitated the permeability compared to the corresponding virgin PVDF membrane. In addition, the modified PVDF membrane showed a distinctively enhanced hydrophilicity and antifouling resistance, as suggested by the contact angle measurement and flux of bovine serum albumin solution tests, respectively. Accordingly, the PVC‐g‐P(PEGMA) graft copolymer was demonstrated as a successful additive for the hydrophilicity modification, and this study will likely open up new possibilities for the development of efficient amphiphilic PVC‐based copolymers for the excellent hydrophilicity modification of PVDF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Graft copolymers from modified ethylene–vinyl acetate (EVA) copolymer. I. Synthesis of poly(ethylene-co-vinyl acetate-g-styrene) using EVA modified by mercaptoacetic acid as chain transfer agent

The modification of the poly(ethylene-co-vinyl acetate) (EVA) by direct esterification of its ethylene—vinyl alcohol copolymer with mercaptoacetic acid was carried out. The amount of the mercaptan group was controlled to avoid gel formation during the graft polymerization with styrene by chain transfer. The chain transfer constant (Cs) of the SH groups and graft efficiency were measured. These graft copolymers were evaluated as a blend compatibilizer. © 1993 John Wiley & Sons, Inc.     

Solid‐state NMR and morphological studies of poly(ethylene‐co‐vinyl acetate)/poly(vinyl acetate) blends

To obtain a correlation among structure–morphology–mobility–compatibility properties of poly(ethylene‐co‐vinyl acetate) (EVA)/poly(vinyl acetate) (PVAc) blends, we have used scanning electron microscopy and solid‐state nuclear magnetic resonance in our investigations. The results are discussed in terms of blends, component dispersion, plasticization effect, and domain mobilities to acquire a response of the correlation between structural properties. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2990–2996, 1999     

Effect of dehydrochlorination of PVC on miscibility and phase separation of binary and ternary blends of poly(vinyl chloride), poly(ethylene-co-vinyl acetate) and poly(styrene-co-acrylonitrile)

The enhancement of miscibility at the lower critical solution temperature (LCST) of the blends poly(vinyl chloride)/poly(ethylene-co-vinyl acetate) (PVC/EVA), poly(vinyl chloride)/poly(styrene-co-acrylonitrile) (PVC/SAN) and poly(vinyl chloride)/poly(ethylene-co-vinyl acetate)/poly(styrene-co-acrylonitrile) (PVC/EVA/SAN) was observed at the micron level. Such miscibility is attributed to the dehydrochlorination and formation of hydrogen bonds between blend components. However, macrolevel immiscibility of these blends heated to the LCST was observed. Such microdomain compatibility of these blends gives a synergistic character. Brittle-type failure observed for LCST samples testifies to the synergism in treated blends. ©1997 SCI     

Surface photocrosslinking of ethylene–vinyl acetate copolymer films

Surface photocrosslinking of ethylene–vinyl acetate (EVAc) copolymer films containing benzophenone (BP) was investigated for the purpose of replacing a poly(vinyl chloride) floor. The photogelatin in the EVAc films was effectively observed after UV radiation in the presence of oxygen. The crosslinking reaction was initiated from the surface of the irradiated film, which was mainly due to the dehydrogenation and generation of macroradicals of polymer by the light absorption of BP. The experiments of polyethylene–VAc with BP showed that the VAc‐rich amorphous part in the EVAc copolymer works as a crosslinking site. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1741–1745, 2000     

Thermal modification of poly(vinyl chloride) and formation of dehydrochlorinated poly(vinyl chloride)–poly(methyl methacrylate) polymer blend in the process of foaming: Identification and application

Impact resistant plastic foam of dehydrochlorinated poly(vinyl chloride) (DHPVC)—poly(methyl methacrylate) (PMMA) was prepared for cryogenic insulation in space vehicle by the method of compression molding and chemical blowing. Impact resistance was achieved by the formation of the polymer blend, dehydrochlorinated poly(vinyl chloride)-poly(methyl methacrylate), during the process of foaming the mold at the temperature of 200°C. The polymer blend was separated from the plastic foam and the compatibility was investigated by ultraviolet, infrared spectral studies and differential scanning calorimetry (DSC). The compatibility of dehydrochlorinated poly(vinyl chloride) and poly(methyl methacrylate) was highlighted on the basis of allylic activation introduced in the thermally modified poly(vinyl chloride). The thermodynamic views were also correlated. The versatility of the present method for impact-resistant foam was pointed out.     

Hydrogen‐bonding interaction of an alternating maleic acid–vinyl acetate copolymer with poly(ethylene glycol), polyacrylamide and poly(N‐isopropylacrylamide): a comparative study

The hydrogen‐bonding interaction and interpolymer complex formation between an alternating maleic acid–vinyl acetate copolymer, (MAc‐alt‐VA) and poly(ethylene glycol) (PEG), polyacrylamide (PAM) or poly(N‐isopropylacrylamide) (PNIPAM) in aqueous solution was potentiometrically and viscometrically investigated. MAc‐alt‐VA formed with PEG a strong hydrogen‐bonding interpolymer complex with a compact structure, and while its interaction with PAM seems to be very weak, if any, the complex formed with PNIPAM is even stronger than that with PEG. This indicates a very important contribution of hydrophobic interaction to the formation of such hydrogen‐bonding interpolymer complexes. Copyright © 2003 Society of Chemical Industry     

Synthesis of poly(vinyl acetate) containing diblock copolymer by DPE method

Diblock copolymer poly(methyl methacrylate)‐b‐poly(vinyl acetate) (PMMA‐b‐PVAc) was prepared by 1,1‐diphenylethene (DPE) method. First, free‐radical polymerization of methyl methacrylate was carried out with AIBN as initiator in the presence of DPE, giving a DPE containing PMMA precursor with controlled molecular weight. Second, vinyl acetate was polymerized in the presence of the PMMA precursor and AIBN, and PMMA‐b‐PVAc diblock copolymer with controlled molecular weight was obtained. The formation of PMMA‐b‐PVAc was confirmed by ¹H NMR spectrum. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to detect the self‐assembly behavior of the diblock polymer in methanol. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

可逆加成-断裂链转移聚合制备聚氯乙烯-b-聚乙二醇-b-聚氯乙烯共聚物

合成了含黄原酸酯端基的聚乙二醇（X-PEG-X）大分子链转移剂,并以其为可逆加成-断裂链转移试剂调控氯乙烯（VC）溶液和悬浮聚合,合成聚氯乙烯-b-聚乙二醇-b-聚氯乙烯（PVC-b-PEG-b-PVC）三嵌段共聚物。X-PEG-X调控VC溶液聚合得到的共聚物的分子量随聚合时间增加而增大,分子量分布指数小于1.65。X-PEG-X具有水/油两相分配和可显著降低水/油界面张力的特性,以X-PEG-X为链转移剂和分散剂,通过自稳定悬浮聚合也可合成PVC-b-PEG-b-PVC共聚物,共聚物颗粒无皮膜结构,分子量随聚合时间增加而增大;由于VC悬浮聚合具有聚合物富相和单体富相两相聚合特性,共聚物分子量分布指数略大于溶液聚合共聚物。通过乙酸乙烯酯（VAc）扩链反应进一步证实了PVC-b-PEG-b-PVC的“活性”,并合成PVAc-b-PVC-b-PEG-b-PVC-b-PVAc共聚物。水接触角测试表明PVC-b-PEG-b-PVC的亲水性优于PVC。     

Fourier transform infrared studies of poly(vinyl chloride) blends with ethylene Co- and terpolymers

The miscibility of poly(vinyl chloride) (PVC) with various ethylene copolymers and terpolymers were investigated using FT-IR spectroscopy. All blends reported were 50/50 by weight. In blends of PVC with ethylene/dimethyl acrylamide copolymer (E/DMA), frequency shifts were observed in the amide carbonyl (proton acceptor) and the α-hydrogen of PVC (proton donor) characteristic bands. In blends of PVC with ethylene/ethyl acrylate/carbon monoxide terpolymer (E/EA/CO), both the ester carbonyl and the ketone carbonyl characteristic frequencies showed mutual shifts and appeared as if they merged together. Small frequency shifts were also observed in the α-hydrogen of PVC characteristic bands. In blends of PVC with ethylene/vinyl acetate/carbon monoxide terpolymer (E/VA/CO), the ester carbonyl frequency showed a shift while that of the ketone carbonyl was essentially unchanged. On the other hand, in PVC blends with ethylene/vinyl acetate copolymer (E/VA), the ester CO frequency did not show any shift, which is consistent with their observed immiscibility. Thus, it is clear that incorporating a ketone ? C?O in ethylene/ester copolymers to form the corresponding terpolymers enhances their miscibility with PVC as earlier proposed on the basis of dynamic mechanical studies. Similar results were shown for blends of PVC with ethylene/2 ethyl hexyl acrylate/carbon monoxide terpolymer (E/2EHA/CO). Frequency shifts imply specific interactions which suggest polymer-polyer miscibility on a molecular scale.     

Plastification of poly(vinyl chloride) by polymer blending

Blends of poly(vinyl chloride) (PVC) with different copolymers have been studied to obtain a plasticized PVC with improved properties and the absence of plasticizer migration. The copolymers used as plasticizers in the blends were acrylonitrile butadiene rubber, ethylene vinyl acetate (EVA), and ethylene-acrylic copolymer (E-Acry). Blends were studied with regard to their processing, miscibility, and mechanical properties, as a function of blend and copolymer composition. The results obtained were compared with those of equivalent compositions in the PVC/dioctyl phthalate (DOP) system. Better results than PVC/DOP were obtained for PVC/acrylonitrile butadiene rubber blends. The plasticizing effect on PVC of EVA and E-Acry copolymers was similar to that of DOP. It is shown that crosslinking PVC/E-Acry blends or increasing the vinyl acetate content in PVC/EVA blends, are alternatives that can increase the compatibility and mechanical properties of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1303–1312, 2000     

Miscibility of poly(vinyl chloride) with ethylene-ethyl acrylate-carbon monoxide terpolyrners

Ethylene/ethyl acrylate/carbon monoxide ter polymers (E/ EA/CO) can exhibit a very high degree of miscibility with poly(vinyl chloride) as determined from dynamic mechanical measurements. The blends yield transparent films and show a large amorphous phase which exhibits only one major glass transition. However, some crystallinity can be detected and has been measured by differential, scanning calorimetry. Residual crystallinity is at least partially due to the somewhat non-uniform nature of the terpolymerization. The acrylate monomer exhibits faster polymerization rates than the other two constituents. By contrast, ethylene/ethyl acrylat copolymers are not miscible with poly(vinyl chloride). The addition of carbon monoxide to the termpolymer structure is believed to yield miscibility with poly(vinyl chloride) via specific interaction of the ketone carbonyl of the terpolymer (proton acceptor) and the tertiary hydrogen of poly(vinyl chloride) (proton donor). This specific interaction allows for a broad range of terpolymer compositions which retain miscibility with polyvinyl chloride. Similar results are also observed with ethylene/vinyl acetate/carbon monoxide (E/VA/CO) as well as ethylene/2-ethylhexyl acrylate/carbon monoxide termpojymers. The vinyl acetate terpolymers (and their blends) display a lower degree of crystallinity than the E/EA/ CO. This is consistent with the more uniform nature of the E/VAJCO terpolymerization.     

Polyblends of poly(vinyl chloride) with ethylene/vinyl acetate copolymers: Practical properties and morphology

Five to 15 percent of ethylene/vinyl acetate copolymers was compounded into rigid polyvinyl chloride, with the copolymers dispersed as discrete micro-domains, produced very efficient synergistic improvement of impact strength; as the vinyl acetate content of the copolymer increased from 28 to 60 percent, the synergistic peak moved to higher copolymer content and became higher and broader. Copolymer content correlated directly with melt flow and thermal stability, and inversely to modulus, strength, and heat-deflection temperature. The vinyl acetate content of the copolymer correlated directly with elongation, impact strength, and thermal stability, but inversely to modulus, heat-deflection temperature, low-temperature flexibility, and melt flow. When the copolymer content reached 25 percent, it formed a second continuous-phase, interpenetrating the polymer network structure and acting as a polymeric plasticizer, producing thermoplastic elastoplastics.     

Compatibility of nylon 6 with poly(vinyl alcohol), hydroxylated poly(vinyl acetate) and poly(vinyl acetate)

Summary The compatibility of nylon 6 with poly(vinyl acetate)(PVAc) and poly(vinyl alcohol)(PVA) was investigated in terms of the melting-temperature depression. In order to vary the compatibility systematically, a hydroxylated poly(vinyl actate)(m-PVAc) was prepared by hydrolyzing PVAc with KOH in CH₃OH. It was found that the compatibility with nylon 6 is better in the systematic order PVA> m-PVAc> PVAc.     

Crystallization behavior of PEO in blends of poly(ethylene oxide)/poly(2‐vinyl pyridine)‐b‐(ethylene oxide) block copolymer

The crystallization behavior of two molecular weight poly(ethylene oxide)s (PEO) and their blends with the block copolymer poly(2‐vinyl pyridine)‐b‐poly(ethylene oxide) (P2VP‐b‐PEO) was investigated by polarized optical microscopy, thermogravimetric analysis, differential scanning calorimetry, and atomic force microscopy (AFM). A sharp decreasing of the spherulite growth rate was observed with the increasing of the copolymer content in the blend. The addition of P2VP‐b‐PEO to PEO increases the degradation temperature becoming the thermal stability of the blend very similar to that of the block copolymer P2VP‐b‐PEO. Glass transition temperatures, T_g, for PEO/P2VP‐b‐PEO blends were intermediate between those of the pure components and the value increased as the content of PEO homopolymer decreased in the blend. AFM images showed spherulites with lamellar crystal morphology for the homopolymer PEO. Lamellar crystal morphology with sheaf‐like lamellar arrangement was observed for 80 wt% PEO(200M) and a lamellar crystal morphology with grain aggregation was observed for 50 and 20 wt% blends. The isothermal crystallization kinetics of PEO was progressively retarded as the copolymer content in the blend increased, since the copolymer hinders the molecular mobility in the miscible amorphous phase. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Thermal characteristics of poly(ethylene terephthalate) fiber grafted with poly(vinyl acetate) and poly(vinyl alcohol)

Poly(ethylene terephthalate) (PET) fibers were grafted with poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVA). The effects of graft copolymers PVAc and PVA on morphological properties of PET were evaluated by differential thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. Melting temperature, heat of fusion, and mass fractional crystallinity of PET was not affected by graft PVAc and PVA. No individual glass transition and melting points corresponding to the graft PVAc and PVA were observed, indicating thereby that graft copolymer mainly exists in the form of free chains inside the PET matrix. Poly(vinyl alcohol) graft copolymer degraded at much lower temperatures than poly(vinyl alcohol) in powder form. Thermal stability of PET fiber was not affected by graft PVAc, where as PET–g–PVA showed an additional degradation point at 360°C.     

Dynamic–mechanical properties of modified poly(ethylene‐co‐vinyl acetate)

To study the relationship among relaxation peaks observed in dynamic mechanical experiments and the structure of poly(ethylene‐co‐vinyl acetate) (EVA), EVA copolymers with different substitution in the carbonyl group were synthesized. EVA was hydrolyzed to obtain poly (ethylene‐co‐vinyl alcohol) and was subsequently reacted with formic, hexanoic, and octanoic acids. The copolymers synthesized were characterized by infrared spectroscopy. Analysis of the DMA spectra of the copolymers showed that their relaxation behavior depends on the vinyl acetate concentration. The α‐ and β‐transitions were observed in EVA copolymers with 8 and 18 wt % of functional groups, and the relationship among relaxation process with the structure of polymer was investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1371–1376, 2005     

Radiation effects on poly(propylene) (PP)/ethylene–vinyl acetate copolymer (EVA) blends

Radiation effects on poly(propylene)/ethylene–vinyl acetate copolymer (PP/EVA) blends are discussed. Increasing the EVA content enhanced the crosslinking effect of radiation in PP/EVA blends. This effect was significant when the EVA content was ≥50% in PP/EVA blends that were exposed to γ‐ray irradiation in air. This phenomenon is discussed in relation to the compatibility, morphology, and thermal properties of PP/EVA blends. The results indicate that the effect is dependent on the compatibility, the increase in the amorphous region content, and the EVA content in PP/EVA blends. The possible mechanism of radiation crosslinking or degradation in irradiated PP/EVA blends was studied quantitatively by a novel method, a “step analysis” process, and thermal gravimetric analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3420–3424, 2002     

Compatibility of Poly(vinyl chloride–vinyl acetate)/Polyester-based Polyurethane Blends

The compatibility of poly(vinyl chloride–vinyl acetate) copolymer (P(VC-VA)) with thermoplastic polyurethane elastomers (TPU) was studied using Fourier transform infrared spectroscopy, optical microscopy and solubility parameters. The Gibbs free energy of mixing for the polymer–solvent system was calculated. The mechanical studies show that decrease in the P(VC-VA)/TPU ratio decreases the tensile strength. © 1997 SCI