Synthesis and reaction kinetics model of suspension phase grafting polypropylene with dual monomers

The grafting polymerization of maleic anhydride (MAH) and styrene (St) onto PP was carried out in suspension phase. Infrared (IR) spectra and ¹H-NMR spectra confirmed that MAH and St were successfully grafted onto the PP backbone. The influences, such as monomers concentration, reaction temperature, initiator concentration and reaction time, on the grafting polymerization rate were also studied, and then the polymerization model was obtained to describe the polymerization regularities. The results showed that the model was adequate to reflect the courses, and diffusion and equilibrium adsorption played an important role in suspension polymerization.     

PP固相接枝GMA微观聚合动力学研究

基于聚丙烯(PP)固相接枝聚合的终止反应主要是自由基单基终止反应的假设提出相应的接枝聚合机理,并建立聚合速率模型。实验考察了PP接枝甲基丙烯酸缩水甘油酯(GMA)体系单体浓度、引发剂浓度、聚合温度与聚合初期接枝速率的依赖关系。结果表明:初始聚合速率与单体浓度呈1.57次方、与引发剂浓度呈0.48次方关系,与聚合温度关系服从Arrhenius方程,并求得接枝反应的表观活化能Ea为86.63kJ/mol。     

聚丙烯固相接枝丙烯酸聚合动力学及其接枝聚合速率模型

基于自由基固相接枝聚合的终止反应主要是自由基单基终止反应的假设提出了相应的聚合机理,并建立了聚合速率模型,聚合速率与引发剂浓度呈1次方、与单体浓度呈小于1次方关系,与聚合温度服从Arrhenius关系.实验考察了聚丙烯固相接枝丙烯酸体系聚合温度、引发剂浓度、单体浓度与初始接枝聚合速率的依赖关系,这一关系与上述速率模型十分吻合.采用无约束非线性优化方法得到了各参数的全局最优解：频率因子为6.868×10⁹,表观活化能为58.89 kJ•mol^-1,单体浓度的幂为0.78.     

Kinetics of graft polymerization of styrene on cis-1,4-polybutadiene

By measurements of polymerization rate, grafting efficiency and number-average molecular weight of free and grafted polystyrene, the α-dicumyl peroxide initiated polymerization of styrene on cis-1,4-polybutadiene at 100°C and at low extents of reaction was studied. The polymerization rate and the polystyrene molecular weights decreased with the rubber content of the solution. The grafting efficiency was found to be substantially independent of the peroxide concentration, but to increase with rubber content. A rigorous mathematical model of the reaction was developed, from which it has been possible to confirm the proposed mechanism and to establish the value of many kinetic constants.     

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.     

高温本体聚合合成ACS树脂的接枝率研究

研究了聚合条件、配方组成及氯化聚乙烯(CPE)的氯化度对高温本体聚合合成丙烯腈(AN) CPE苯乙烯(St)接枝共聚物（ACS）树脂接枝率的影响。结果表明,本体聚合合成ACS树脂过程中接枝反应主要发生在聚合转化率低于50 %的低转化率阶段;反应温度、引发剂及链转移剂用量是影响本体聚合合成ACS接枝率的主要因素;提高聚合反应温度、增加引发剂和链转移剂浓度均会导致接枝率显著下降;St/AN的质量比、CPE橡胶的含量及氯化度对接枝率的影响较小。     

ABS乳液接枝聚合反应中影响接枝率的因素

采用乳液聚合法合成ABS接枝聚合物,通过改变反应过程中聚丁二烯、引发剂和分子量调节剂的用量,改变反应温度及增量反应时间,考察ABS接枝聚合物接枝率的变化。结果表明：在实验范围内,接枝率随着聚丁二烯或分子量调节剂用量的增加迅速减小;随着引发剂用量的增加或增量反应时间的增长而增大;随着反应温度的升高而增大,但变化不大。     

Kinetics and mechanism of free radical grafting of methyl acrylate onto sago starch

The graft copolymerization was carried out by methyl acrylate with sago starch in which ceric ammonium nitrate was used as an initiator. It has been found that the rates of graft polymerization and grafting efficiency were dependent upon the concentration of ceric ammonium nitrate (CAN), methyl acrylate (MA), sago starch (AGU, anhydro glucose unit), mineral acid (H₂SO₄), and as well as reaction temperature and period. A rate equation of polymerization was established from the proposed reaction mechanism, and the rate of polymerization (R_p) was the first‐order dependence of the MA monomer concentration and square root of the CAN concentration. A new kinetic model of the grafting reaction has been proposed, and a normal kinetics of methyl acrylate polymerization was observed. An equation of a predicted model relating the graft fraction of poly(methyl acrylate) with the sago starch has been derived, and validity of the predicted model was verified by the experimental results. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 784–791, 2000     

废PSF接枝改性物的粘接性能

用溶液接枝的方法研究了回收的废聚苯乙烯泡沫塑料的接枝工艺,其包括:引发剂量、反应温度、单体浓度、单体种类、多单体共接枝的影响。作者还研究了增粘剂与PS接枝物的相容性,从而配制了粘接性能良好的粘合剂,这种粘合剂还有优良的耐水性。     

Photochemical reactions of high polymers. XIII. Photografting of methyl methacrylate onto the polymers bearing thiosulfate groups

Polymers bearing pendent thiosulfate groups, that is, sodium poly(vinyl benzyl thiosulfate) (PVBB) and the sodium salt of poly(vinyl hydrothiosulfatoacetate)(PV AcB), were prepared. The photograft polymerization of methyl methacrylate onto these polymers was carried out. The relationships between irradiation time and conversion, degree of grafting, and grafting efficiency were investigated in the photograft polymerization. It was ascertained that the pendent thiosulfate groups acted as effective initiators for the graft polymerization. From the number of endgroups in the homopolymer formed along with the graft polymer, the mechanism of the graft polymerization was discussed and it was verified that the graft polymerization was initiated by the thiyl radical formed by scission of the sulfur–sulfur bond of the pendent thiosulfate group. An unusually high degree of grafting and extremely rapid polymerization rate observed in the graft polymerization suggested the dual functions of thiosulfate-bearing polymer as initiator and emulsifier. It was found that addition of FeCl₂ to this polymerization system increased the rate of polymerization and the degree of grafting but decreased the grafting efficiency. The effect of FeCl₂ was interpreted by assumption of a photo-redox reaction between thiosulfate group and Fe²⁺.     

Benzoyl peroxide-induced graft polymerization of 2-methyl-5-vinylpyridine onto polyester/wool blend

Graft polymerization of 2-methyl-5-vinylpyridine (MVP) onto polyester/wool blended fabric was carried out using benzoyl peroxide as initiator. The graft polymerization reaction was conducted under a variety of conditions. The graft yield increased by increasing benzoyl peroxide concentration from 0.559 mmole/l. to 1.657 mmole/l. Further increase in benzoyl peroxide concentration (i.e., up to 2.795 mmole/l.) decreased grafting. Increasing the MVP concentration from 4% to 10% caused a significant enhancement in grafting. The same held true for raising the polymerization temperature within the range of 65°–85°C. The grafting reaction proceeded initially at a fast rate and decreased with time to a slower rate. The grafted samples showed improved dyeability toward acid dye, increased density, and decreased moisture regain as compared with the untreated blend. Furthermore, a tentative mechanism for initiation of grafting was suggested.     

高抗冲聚苯乙烯(HIPS)连续生产的模拟

根据热引发连续本体聚合生产高抗冲聚苯乙烯 (HIPS)的动力学机理 ,建立了苯乙烯 /顺丁二烯橡胶本体聚合过程的多釜串联 (CSTR)数学模型 ,并由两个不同品牌的实际工业生产数据对模型进行了验证。得到了各釜出口苯乙烯单体的转化率、HIPS的接枝效率、接枝率以及自由PS的重均分子量及其分布     

The Synthesis of Chitin-g-Poly(vinyl acetate) Copolymers with a Redox Initiator

Vinyl acetate monomer was graft polymerized onto chitin with a redox initiator, cerium ammonium nitrate. Both the graft copolymerization and emulsion polymerization of pure poly(vinyl acetate) (PVAc) were observed during the reaction and a stable dispersion solution was obtained after the reaction. After the PVAc homopolymer was removed by acetone extraction, the grafting efficiency and grafting percentage were calculated from the weight balance. Transmission and scanning electronic microscope were used to observe the morphologies of the reaction product. Experimental results indicated that at initial stage of reaction, graft copolymerization, which occurred on the surface of chitin particles, dominated over the emulsion polymerization. After that, the rate of emulsion polymerization increased greatly and became dominant. The existence of chitin not only provided the stability of the emulsion particles, but also increased the polymerization rate. Structures of copolymers were evidenced with the techniques of Fourier transform infrared and differential scanning calorimeter.     

丙烯酸接枝改性环氧树脂的研究

用溶液聚合法制备环氧树脂，丙烯酸类接枝改性物，研究了酸量、MAA/AA的比、引发剂BPO的用量、环氧树脂型号、反应时间等对接枝率和环氧值的影响。最后研究发现：酸量与环氧树脂的质量比为1：1，MAA：AA物质的量比为0．12：0．42，环氧树脂型号为E-20，反应时间为3．5h，该条件下制备出来的接枝改性物接枝率最大，且环氧基发生开环的量较少。     

The graft copolymerization of styrene and lignin. III. Chain transfer reactions of lignin and lignin model compounds

The effect of addition of lignin model compounds on the polymerization rate and molecular weight of polymer in the radiation-induced polymerization of styrene was studied. Guaiacol, a model for softwood lignin, reacted slowly with styrene radicals, while 2,6-dimethoxyphenol, a hardwood lignin model, was a much more efficient chain transfer agent. Studies with isoeugenol indicate that allylic or phenoxy radical stability in a conjugated system may terminate polymerization quite effectively. The results are discussed in the light of new and previous data with isolated lignins; they are consistent with the previously presented grafting scheme.     

H2O2-induced graft polymerization of acrylic acid on poly(ethylene terephthalate) fibers

Graft polymerization of acrylic acid to poly(ethylene terephthalate) fibers using H₂O₂ as initiator was only possible in benzyl alcohol as reaction medium. The effect of initiator and monomer concentrations, reaction time, and temperature as well as addition of metallic salts to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing H₂O₂ concentrations up to 100 mequiv/L and then decreased upon further increase in initiator concentration. The same held true for acrylic acid concentration of up to 10%, but above this concentration grafting leveled off. Raising the polymerization temperature from 85 to 115°C favored grafting at lower H₂O₂concentration. The reverse was the case at higher H₂O₂ concentration (more than 25 mequiv/L). Addition of copper sulfate to the polymerization medium decreased the rate of grafting, and no leveling off of grafting could be achieved even after 5 h. The ferrous ammonium sulfate functioned similarly but to lesser degree, and leveling off of grafting occurred after 4 h. This contrasted with grafting in the absence of metallic salts where grafting leveled off after 1 h. Action of initial graft formation as diffusion barrier is believed to account for this.     

A comparative study on effects of two kinds of polymerization methods on grafting of polymer onto silica surface

In this article we present the result of a comparative study of two kinds of polymerization methods—solution polymerization (sol. poly.) and dispersion polymerization (dis. poly.) for grafting polymer onto silica. As a model for the grafting polymerization reaction, styrene was chosen as the monomer and azo diisobutyronitrile (AIBN) as the initiator. The study aims at supplying theoretical reference for better selecting polymerization method to graft polymer on the silica particle surface. First, monolayers of 3‐methacryloylpropyl trimethoxysilane were chemically bonded onto the surfaces of micrometer‐sized silica gel particles, and so double bonds were immobilized onto the silica surface. Second, the copolymerizations between the immobilized double bonds and the monomer styrene were carried out, homopolymerizations of styrene followed, and finally polystyrene was grafted to the silica surfaces. Two kinds of polymerization methods, sol. poly. and dis. poly., were adopted respectively, and the effects of polymerization methods on grafting process were examined mainly. At the same time, the effects of different polymerization conditions on the grafting degree were researched. It was found that in the dis. poly. system the grafting degree is obviously higher than that in the sol. poly. system under the same polymerization conditions, and the grafting degree can go up to 47%, i.e. 47g/100g. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5808–5817, 2006     

Graft copolymerization of acrylonitrile onto bagasse and wood pulps

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.     

Graft copolymerization of gelatin with poly(methyl methacrylate) in aqueous medium

The grafting of poly(methyl methacrylate) onto gelatin in aqueous medium has been studied experimentally. The polymerization system is heterogeneous and the temperature and the initial concentration of gelatin charged in the reactor have been found to be extremely important. It is found that the amount of graft polymer increases rapidly and the formation of homopolymers is suppressed for large times. The predominantly graft polymer for the large times is essentially free from homopolymers and needs no separation. A theoretical model has been proposed which accounts for the heterogeneity in the reaction mass. The numerical solution of mass balance equations and its validation against experimental data suggests that graft copolymers react at the waterdroplet interphase at considerably higher rate.     

The kinetics of two-phase bulk polymerization. I. Monomer and initiator distribution

Rubber-reinforced thermoplastics are produced commercially by dissolving a rubber in the monomer of a glassy polymer and commencing polymerization with a free-radical initiator. Beyond a few per cent conversion, the incompatibility of the two polymers causes a phase separation, with each phase containing one nearly pure polymer. Subsequent polymerization occurs in each phase. The heterogeneous nature of the reaction can influence both the kinetics of the reaction and the amount of grafting in the product. The fact that only monomer which polymerizes in the rubber phase can possibly graft establishes an upper limit to the amount of grafting and hence influences the mechanical properties of the product. It is shown theoretically how unequal partitioning of monomer and initiator between the phases can influence the extent of grafting, and can also explain the kinetic rate reductions which have been observed in such systems. The distributions of monomer and benzoyl peroxide and azobisisobutyronitrile initiators between the phases have been determined experimentally for a styrene–polystyrene–polybutadiene system. They cannot account for the rate reduction observed in such systems.