Radiation-induced graft polymerization of vinyl benzyltrimethylammonium chloride onto polyethylene film

An attempt was made to introduce a strong base anion-exchange group by radiation-induced grafting of vinyl benzyltrimethylammonium chloride (VBTAC) onto polyethylene film. Both two-step grafting and comonomer grafting techniques were tried owing to the difficulty of direct graft polymerization of VBTAC onto polyethylene. 2-Hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA), having the same backbone structure except that the hydroxyl group of HEMA was grafted onto the polyethylene film and then VBTAC was grafted to examine the reactivity of VBTAC with each grafted polyethylene film. Co-grafting of the binary mixtures of VBTAC and HEMA, or EMA, onto polyethylene film was also carried out. © 1994 John Wiley & Sons, Inc.     

Thermally induced solid-state polymerization in nylon 66

The thermally induced solid-state polymerization of 66 nylon was investigated. It was found that the rate-controlling step in the process is chemical reaction. A mechanism of the form, rate = ktⁿ was shown to hold. The reaction rate constant was found to be k = 1.53 × 10¹⁰ exp [ ? 12,960/RT]. Units of k are (hours)^?0.51. Activation energy determined in this work compared closely to that determined for nylon 6 solid-state polymerization.     

Surface graft polymerization onto silicone

A method was developed for surface graft polymerization onto silicone. A silicone prepolymer carrying vinyl groups, which can be cured by a free-radical mechanism, was used. Acrylamide can be easily graft polymerized by simply heating the films made of a mixture of the silicone prepolymer and peroxide in an acrylamide monomer solution using an autoclave. Any complicated procedures, such as thorough degassing of the silicone films and the monomer solution, and sealing them into a glass ampoule, are not necessary. The grafted layer uniformly covered the silicone surface. The surface properties of the silicone become hydrophilic and slippery after grafting of the poly(acrylamide). © 1993 John Wiley & Sons, Inc.     

The cupric sulphate-hydrazine hydrate system as an initiator for vinyl graft polymerization onto wool

The ability of the cupric sulphate-hydrazine hydrate redox system to induce vinyl graft polymerization onto wool fibres was studied under different conditions. The magnitude of grafting is governed by concentrations of cupric ions, hydrazine hydrate and monomer as well as pH and temperature of the polymerization medium. Detailed studies were carried out on grafting of wool with methyl methacrylate though ethyl acrylate and styrene were also used. Cupric ions were also replaced by ferric ions in some experiments. Main conclusions arrived at from these studies are: (a) there are optimal concentrations of cupric ion and hydrazine hydrate, (b) the grafting reaction is more favoured at higher (pH higher than 7) than that at lower pH's (pH less than 5), (c) 70°C constitutes the optimal temperature for grafting, (d) the graft yield increases by increasing methyl methacrylate concentration, (e) replacement of cupric ion by ferric ion lowers the rate of grafting and (f) the highest graft yield is obtained with methyl methacrylate and the lowest with styrene.     

尼龙66连续聚合耗热量分析

分析了五大器式尼龙66连续聚合中各单元设备的耗热量,主要是工艺热量消耗和热损失。计算表明每吨产品的工艺耗热量为3．78×106kJ／h,其中蒸发水分所消耗的热量约70％以上。提出了节能措施: 提高设备保温层的保温质量,采用热阻大的保温材料;对蒸发盐液产生的蒸汽回收利用;采用新的盐液蒸发方式,可大大降低盐蒸发的蒸汽消耗量。     

Graft polymerization of vinyl acetate onto silica

A method is reported for the surface grafting of polyvinyl acetate (PVAc) onto modified, nonporous silica. The silica surface was modified by silylation with vinyl(triethoxy) silane followed by graft polymerization of vinyl acetate. The graft yield was measured by thermogravimetric analysis and the monomer conversion was monitored by UV spectral analysis. The rate of the graft polymerization and the graft yield were proportional to the initial monomer concentration. Vinyl acetate conversion followed first-order kinetics and displayed a trend of increasing initial rate with increasing monomer concentration.     

Graft polymerization of vinyl acetate onto silica

The free‐radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free‐radical graft polymerization of vinyl acetate in ethyl acetate with 2,2′‐azobis(2,4‐dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer‐grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy–determined topology of the polymer‐grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular‐weight distribution for free‐radical polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 300–310, 2003     

Chemical grafting of polyaniline onto nylon66 fiber in different media

Graft copolymerization of polyaniline (PANI) onto nylon 66 fiber was carried out in two different media, hydrochloric acid and p‐toluene sulfonic acid (PTSA), using peroxodisulfate (PDS) as an initiator. Percentage grafting, percentage efficiency, and rate of grafting were determined. The grafting of PANI onto nylon 66 was confirmed through FTIR spectroscopy, cyclic voltammetry (CV), weight‐loss study, and conductivity measurement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1283–1296, 2001     

Graft polymerization of some vinyl monomers onto acrylic rubber. II. Mechanical properties of graft polymers

Some mechanical properties of styrene and acrylonitrile copolymers grafted onto acrylic rubber are investigated. The impact strength of graft polymers depended upon the nature and the concentration of the catalyst, the composition and the intrinsic viscosity of the rubber, and the acrylonitrile content in the rigid matrix. The most desirable result was obtained when benzoyl peroxide as the catalyst, n-butyl acrylate–acrylonitrile copolymer of 7–10% acrylonitrile content, and about 0–5% acrylonitrile in the rigid matrix were used. Dynamic mechanical tests show the increase in efficiency of rubber modification by the grafted chains. The better weathering resistance of these graft polymers, as compared with commercial ABS plastics, was confirmed.     

Some aspects of graft polymerization of vinyl monomers onto cellulose by use of tetravalent cerium. VI

The state of cellulose as defined by its crystallinity, grinding, and average degree of polymerization (D.P.) highly influences the grafting yield. Grinding of cellulose with a Wiley mill results in decreased grafting, while grinding with a ball mill or treatment with ethylenediamine, both of which lead to decrystallization of cellulose, nearly inhibits the grafting reaction from taking place. On the other hand, decreased D.P. leads to increased grafting yield. The governing factor being attributed to the specific surface of the cellulose. Increased specific surface, as decreased D.P., brings about an increase in the active sites formed on the cellulose and hence an increase in the grafting yield. However, this occurs up to a limit beyond which further increase in the specific surface, respectively, the formed active sites, as grinding with a Wiley mill and decrystallization, brings about termination reactions through disproportionation and coupling of the exceedingly increased free radicals, and hence grafting is decreased or nearly inhibited. Drying of cellulose at 105°C resulted in decreased grafting yield. This was attributed to condensation of the cellulose structure. It has been also found that the grafting yield is influenced by the type and origin of cellulose whose reactivities differ for different monomers.     

Photoinduced graft polymerization of styrene onto polypropylene substrates

The photochemical grafting of styrene onto polypropylene (PP) using benzophenone (BP) and benzoin ethyl ether (BEE) as photosensitizers is described. The effects of various parameters (such as monomer and photosensitizer concentration, reaction time, and solvent) on percent grafting were studied. We found that BP is a very efficient photosensitizer for the grafting of styrene onto PP surfaces. Unlike BEE, BP does not initiate nongrafting homopolymerization reactions in solution which compete with grafting reactions. This is advantageous over other photosensitizers since homopolymer formed in solution can interfere with the grafting reaction as well complicate sample preparation and purification. The graft copolymers obtained using both BP and BEE were characterized by high resolution ¹H-NMR, optical microscopy and swelling studies. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 883–889, 1997     

纳米SiO2表面接枝聚合苯乙烯

通过对纳米SiO2进行表面修饰，引入乙烯基功能基，将其与苯乙烯进行溶液聚合，制备了PS表面接枝纳米SiO2。苯乙烯转化率，接枝率和接枝效率分别为60．7％，24．0％和1．31％。透射电镜表明PS表面接枝纳米SiO2在有机溶剂中具有较好的分散性，可用于制备无机纳米聚合物材料。     

Isothermal crystallization and melting behaviors of nylon 11/nylon 66 alloys by in situ polymerization

Nylon 11/nylon 66 alloys were prepared by in situ polymerization. Analysis of the isothermal crystallization behaviors of nylon 11/nylon 66 alloys was carried out using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The crystallization kinetics of the primary stage under isothermal conditions could be described by the Avrami equation. The crystal morphology observed by means of polarized optical microscope (POM). In the DSC scan after isothermal crystallization process, the multiple melting behaviors were found and each melting endotherm has a different origin. The real-time XRD measurements confirmed that no crystalline transition existed during the isothermal crystallization process. The multiple endotherms were experimentally evidenced due to melting of the recrystallizated materials or the lamellae produced under different crystallization processes. The equilibrium melting point of samples for isothermal crystallization was also evaluated.     

Graft polymerization of some vinyl monomers onto alkali-treated cellulose

Treatment of cellulose by different concentrations of alkali, namely, 5–30% NaOH, changed its fine structure and transferred cellulose I into cellulose II. The decreased crystallinity due to alkali treatment and the transformation of cellulose I into cellulose II lowered the reactivity of cellulose toward the grafting polymerization reactions. Compactness of the structure as a result of the treatment of cellulose with 5% sodium hydroxide concentration decreased the rate of the grafting reaction and the grafting yield. On the other hand, such treatment of cellulose with different concentrations of alkali increased the rate of ceric consumption, i.e., increased the rate of oxidation of cellulose. Thus, the termination reaction of the grafting polymerization process may occur as a result of such oxidation and because of the increase of the active sites onto cellulose, leading to a decrease of the grafting yields and rate of grafting polymerization reaction by using the free-radical grafting process. The use of the ionic-xanthate method of grafting polyvinyl- and polyallyl-on alkali-treated cellulose shows an increase of grafting efficiency and grafting yields. Maximum grafting efficiency and yields were achieved when cellulose was treated with sodium hydroxide concentration below 15%, and maximum crystallinity indices were obtained. Using 15–25% sodium hydroxide lowered the indices of crystallinity, and lower grafting yields and grafting efficiency were achieved. Thus, transformation of cellulose I into cellulose II decreased the reactivity of these treated celluloses toward graft polymerization reactions by the use of the ionic-xanthate method. In our opinion, termination reactions may also occur and affect the results.     

尼龙66聚合反应器排汽回收利用技术改造

介绍了尼龙66连续聚合纺丝生产工艺路线,改造前反应器排放大量的过热蒸汽直接进入大气,造成能源浪费和环境污染。通过技术改造,新增饱和蒸汽塔、过滤器等废汽回收利用装置,根据高压蒸汽减温减压装置原理,将反应器排放的1.85 MPa,245℃过热蒸汽在饱和塔内进行喷淋,经过滤器除杂转换为0.8~1.0 MPa饱和蒸汽,作为浓缩槽热源;浓缩槽排放蒸汽的余热改造后作为第三温水系统和冬季取暖的热源,排汽余热得到充分利用。运行过程中,通过稳定控制反应器压力、保持反应器排汽阀的喷淋水流量和压力稳定等工艺条件,定期清理疏水阀等,可有效预防管路和设备堵塞。改造后,装置运行稳定,能耗降低,尼龙66聚合物相对黏度的均匀性和原丝一等品率均有所提高。     

Thermal induced graft polymerization using peroxide onto polypropylene fiber

Various monomers were grafted onto polypropylene (PP) fiber via thermal cleavage of BPO. The monomers included acrylic acid and 3-(sulfopropyldimethylamino)ethyl-2-methylacrylate. Grafting percentage exceeded 100% in all cases. The grafted PP fiber was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy and thermal analysis.     

Photoinduced acrylamide graft polymerization onto extended hard elastic polypropylene

Hard elastic PP films were graft polymerized with PAAm, using a photoinduction method derived by Tazuke. The graft yield (GY) was measured as a function of extension applied to the PP film during the polymerization. The GY increased stepwise when the extension increased above the yield point. This remarkable increase in GY is due to the fact that the surface of voids created by extension are involved in the graft polymerization. The GY obtained under extensions larger than the yield point was much larger than that ever achieved for the usual PP films. The residual strain after the graft polymerization increased with increase in GY, and the relationship between them changed at about 40% GY, suggesting that some change occurred in the location of grafted PAAm in PP films. The graft ratio, determined after complete extraction of PP and PAAm homopolymers, remained nearly constant with polymerization time, except at the early stage of the polymerization. The effect of extension on the graft ratio implied that the size of the voids may affect the degree of polymerization of graft PAAm when the size is comparatively small.     

Corona-induced graft polymerization of ethyl acrylate onto cellulose film

Ethyl acrylate was readily grafted from an aqueous solution onto cellophane film previously treated in a corona discharge at atmospheric pressure. The effect was found when the corona treatment was carried out not only in air but also in pure nitrogen. The observed grafting was not promoted but depressed by the presence of ferrous ion, which indicated that peroxide radicals were not initiating the graft. A high grafting efficiency was obtained, and the grafted surface was covered with a smooth uniform layer of polymer.     

On the graft polymerization of styrene and acrylonitrile onto polybutadiene in the presence of vinyl acetate. II. Properties of graft polymers

The properties of the graft polymers of styrene, acrylonitrile, and vinyl acetate onto polybutadiene rubber that were prepared for the modification of graft polymers of styrene and acrylonitrile onto polybutadiene (ABS polymers) by emulsion polymerization up to a high degree of conversion have been studied and discussed. Both the impact strength and notched impact strength of the graft polymers have been found to remarkably increase with a rising quantity of vinyl acetate, in particular, in the case of styrene substitution, whereas in the case of acrylonitrile substitution by vinyl acetate, the two characteristics become noticeably poorer. The effects of the vinyl acetate amount and the type of substituted monomers on bending strength, tensile strength, Vicat softening point, and glass transition temperature of the graft polymers are also clearly different. Furthermore, the properties of the above graft polymers blended with styrene/acrylonitrile copolymers have been studied.