Graft copolymerization of methacrylic acid onto isotactic polypropylene by radiochemical methods

Graft copolymerization of methacrylic acid onto isotactic polypropylene has been studied in water–methanol medium using γ-rays as the source of initiation. Graft copolymerization has been conducted by (1) mutual irradiation, (2) preirradiation, and (3) double irradiation methods. All of the reaction parameters that seem to influence grafting have been studied, and the optimum conditions leading to maximum percentage of grafting have been evaluated. A plausible mechanism for radiation-induced grafting of methacrylic acid onto polypropylene has been suggested, and the results have been explained on the basis of the proposed mechanism. A comparative study of graft copolymerization by different radiation methods has been made, and it was observed that the preirradiation method affords the best results. Evidence of grafting has been obtained from differential scanning calorimetric analysis and the dyeing behavior of the grafted material. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 143–152, 1998     

Study of modified polypropylene nonwoven cloth. I. graft copolymerization of 4‐vinylpyridine onto polypropylene nonwoven cloth by preirradiation method

Polypropylene (PP) nonwoven cloth was grafted with 4‐vinylpyridine (4‐VP) by a preirradiation method. The effects of preirradiation conditions on the mechanical properties of preirradiated PP nonwoven cloth and the percentage of grafting (Pg) of 4‐VP onto the preirradiated PP nonwoven cloth were systematically investigated. The results indicated that the mechanical properties of preirradiated PP nonwoven cloth decreased with increasing irradiation dose and that the Pg was greatly affected by the concentration of monomer, irradiation dose, grafting reaction temperature, and the addition of inhibitor and inorganic acid in the grafting reaction system. The grafted nonwoven cloth samples were characterized using IR spectroscopy and SEM. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1861–1868, 2000     

等规聚丙烯-丙烯酸接枝共聚

详细研究了等规聚丙烯细粒子在丙烯酸水溶液中,以过氧化苯甲酰为引发剂的液－固相接枝共聚反应和十氢化萘乙醇溶液对等规聚丙烯的膨化预处理作用,检测了等规聚丙烯－聚丙烯酸的某些性质,发现随接枝率提高,其吸湿性和碱性染料染色性均提高,熔点略有降低,但熔体流动性下降,按本研究获得的最佳膨化预处理条件和最佳接枝共聚反应条件,接枝产物等规聚丙烯－聚丙烯酸的接枝率可超过13％。     

Study of electron beam preirradiation-induced graft copolymerization of acrylic acid onto powdered isotactic polypropylene

In order to obtain required polymer materials, acrylic acid was grafted onto powdered isotactic polypropylene by an electron beam preirradiation technique. All processes (including irradiation, storage of the samples, and grafting polymerization) were carried out in air. The effects of irradiation dose, storage time, reaction temperature, morh's salt, acid, and monomer concentration were investigated and discussed in detail. The results show that the grafting can be achieved well without purging oxygen, and morh's salt is indispensable for initiating grafting reaction and decreasing the homopolymerization. Optimal reaction conditions can be generalized for large-scale production of the desired polymer materials. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1357–1362, 1999     

聚丙烯纤维共辐射接枝苯乙烯的研究

以60Co γ射线为辐射源,在氮气保护下对聚丙烯(PP)纤维和苯乙烯-二乙烯苯在甲醇介质中进行共辐射接枝。结果表明,当接枝液中苯乙烯质量分数为20％-30％,辐射总剂量为25-50 kGy时,PP纤维的接枝率高。二乙烯苯相对苯乙烯的质量分数为2％时,纤维的接枝率和玻璃化转变温度最高,分别为701％和161.5℃。接枝反应离开辐射源后存在一定程度的后效应,放置一定时间和接枝液中加入适量无机酸均可有效提高PP纤维的接枝率。在相同条件下,用乙醇替代甲醇可以达到相近的接枝率。     

Structure and mechanism of functional isotactic polypropylene via in situ chlorination graft copolymerization

This paper discusses the structure and mechanism of maleic anhydride (MAH) grafted onto isotactic polypropylene (iPP) via in situ chlorination graft copolymerization (ISCGC). The molecular structure of the grafted iPP was characterized using ¹H NMR and ¹³C NMR spectroscopy, viscosity‐average molecular weight and gel content. The structure of un‐grafted MAH present in the reaction system was investigated using Fourier transform infrared spectroscopy in order to explore the grafting of MAH on iPP. The main side‐reactions, including iPP chain scission and crosslinking, during the grafting reaction were explored. From the experimental results obtained, the reason for controlled macromolecular chain degradation and crosslinking of grafted iPP in ISCGC is proposed. Based on the structural characterization of the grafted polymer, the mechanism of grafting onto iPP obtained via ISCGC was deduced. Mechanical properties, both static and dynamic, of grafted iPP were also investigated and the results showed that the properties of the material changed due to grafted MAH. Copyright © 2011 Society of Chemical Industry     

Radiation‐induced GMA/DMAA graft copolymerization onto porous PE hollow‐fiber membrane

Radiation‐induced graft copolymerization is a powerful technique to prepare a grafted chain with the desired properties pending onto the trunk material. In this work, a polyethylene hollow‐fiber membrane was modified by this technique. The monomers glycidyl methacrylate (GMA) and N,N‐dimethylacrylamide (DMAA) were cografted onto macroporous polyethylene hollow fiber with a grafting degree in the order of 200%. DMAA/GMA cografted membranes were compared to GMA grafted ones for the introduction of an amino acid as a specific ligand. Grafted membranes with a copolymer composition between 0 and 2 DMAA/GMA were prepared by soaking them in solutions of different mixtures of monomers. Copolymers were characterized by FTIR and their composition was estimated by the analysis of the ratio of carbonyl signals. Copolymers with a higher proportion of DMAA showed improved hydrophilic properties and higher conversion rates of epoxy groups on phenyalanine ligands than those of the GMA grafted ones. However, copolymers with a DMAA/GMA ratio higher than 1 showed a detrimental effect on the pure water flux. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1646–1653, 2003     

Morphology,crystallization, and thermal behavior of isotactic polypropylene/propylene‐g‐styrene blends

Optical microscopy, differential scanning calorimetry, and small angle X‐ray scattering techniques were used to study the influence of the crystallization conditions on morphology and thermal behavior of samples of binary blends constituted of isotactic polypropylene (iPP) and a novel graft copolymer of unsaturated propylene with styrene (uPP‐g‐PS) isothermally crystallized from melt, at relatively low undercooling, in a range of crystallization temperatures of the iPP phase. It was shown that, irrespective of composition, no fall in the crystallinity index of the iPP phase was observed. Notwithstanding, spherulitic texture and thermal behavior of the iPP phase in the iPP/uPP‐g‐PS materials were strongly modified by the presence of copolymer. Surprisingly, iPP spherulites crystallized from the blends showed size and regularity higher than that exhibited by plain iPP spherulites. Moreover, the amount of amorphous material located in the interspherulitic amorphous regions decreased with increasing crystallization temperature, and for a given crystallization temperature, with increasing uPP‐g‐PS content. Also, relevant thermodynamic parameters, related to the crystallization process of the iPP phase from iPP/uPP‐g‐PS melts, were found, composition dependent. The equilibrium melting temperature and the surface free energy of folding of the iPP lamellar crystals grown in the presence of uPP‐g‐PS content up to 5% (wt/wt) were, in fact, respectively slightly lower and higher than that found for the lamellar crystals of plain iPP. By further increase of the copolymer content, both the equilibrium melting temperature and surface free energy of folding values were, on the contrary, depressed dramatically. The obtained results were accounted for by assuming that the iPP crystallization process from iPP/uPP‐g‐PS melts could occur through molecular fractionation inducing a combination of morphological and thermodynamic effects. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2286–2298, 2001     

Radiation‐induced graft copolymerization of methylmethacrylate onto poly(tetrafluoroethylene‐co‐ethylene) film

Modification of poly(tetrafluoroethylene‐co‐ethylene), Tefzel (ETFE), film has been carried out by grafting methylmethacrylate (MMA) by radiation method including preirradiation and double‐irradiation methods. Percentage of grafting has been determined as a function of the (i) total dose, (ii) monomer concentration, (iii) amount of liquor ratio, (iv) reaction time, and (v) temperature.The effect of different alcohols such as methanol, ethanol, 2‐propanol, n‐butanol, n‐pentanol, and 2‐ethoxy ethanol on percentage of grafting of MMA was also studied. The graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis (TGA). Methylmethacrylate produces higher percentage of grafting by preirradiaton method than double‐irradiation method. MMA‐grafted ETFE films (S_irr), i.e., prepared by preirradiation involving single irradiation show better thermal stability than MMA‐grafted ETFE films (D_irr), i.e., prepared by double irradiation and unmodified ETFE film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nitroxide‐mediated homopolymerization and copolymerization of 2‐vinylpyridine with styrene

Homopolymerization and copolymerization of 2‐vinylpyridine (2VP) with styrene (S) at 125°C in the presence of 2,2,6,6‐tetramethyl piperidin‐1‐yloxyl (TEMPO) radicals have been studied. The homopolymerization was carried out with 2,2′‐azobis(isobutyronitrile) (AIBN) as a thermal initiator or without AIBN in the initial reaction mixture. In the copolymerization initiated with AIBN, the molar fraction of 2VP in the feed, F_2VP, varied in the range of 0.1–0.9; F_2VP = 0.65 was found to be the azeotropic composition. The linear semilogarithmic time–conversion plots demonstrated a pseudoliving nature of the polymerizations under study. The molecular weight–conversion dependences indicated the participation of side reactions, diminishing the number of TEMPO‐terminated polymer chains. The synthesized homopolymers and copolymers were characterized using size‐exclusion chromatography (SEC), nitrogen analysis, and NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2024–2030, 2001     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. II. Characterization of sulfonated graft copolymer membranes

PFA‐g‐polystyrene sulfonic acid membranes were prepared by simultaneous radiation‐induced graft copolymerization of styrene onto poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA) film followed by sulfonation. The membrane physico‐chemical properties such as swelling behavior, ion exchange capacity, hydration number, and ionic conductivity were studied as a function of the degree of grafting. Thermal as well as chemical stability of the membranes was also investigated. The membrane properties were found to be mainly dependent upon the degree of grafting. The water uptake, ion exchange capacity, hydration number, and ionic conductivity of the membranes were increased, whereas the chemical stability decreased as the degree of grafting increased. The membranes showed reasonable physico‐chemical properties compared to Nafion 117 membranes. However, their chemical stability has to be further improved to make them acceptable for practical use in electrochemical applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1–11, 2000     

Studies on graft copolymerization of 4‐vinylpyridine onto guar gum

Graft copolymerization of 4‐vinylpyridine (4‐VP) onto guar gum (GOH) using potassium monopersulfate (PMS)/thioacetamide (TAA) as a redox pair was studied in an aqueous medium under inert atmosphere. The concentration of potassium monopersulfate and thioacetamide should be 1.0 × 10^?2 and 5.0 × 10^?3 mol dm^?3, respectively, for highest grafting ratio and efficiency. Efficient grafting was observed at 19.25 × 10^?2 and 4.87 × 10^?2 mol dm^?3 concentration of 4‐vinylpyridine and sulfuric acid, respectively. The optimum temperature for grafting is 30°C. As the time period of reaction is increased, the grafting ratio increases, whereas efficiency decreases. The plausible mechanism of grafting has been suggested. A sample of guar gum and guar‐ g‐4‐vinylpyridine were subjected to thermogravimetric analysis with the objective of studying the effect of grafting 4‐vinylpyridine on the thermal stability of guar gum. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2380–2385, 2002     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. IV. Morphological investigations using X‐ray photoelectron spectroscopy

Morphological investigations of poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA)‐g‐polystyrene sulfonic acid membranes prepared by radiation‐induced graft copolymerization of styrene onto PFA films followed by sulfonation were performed by X‐ray photoelectron spectroscopy. The analyzed materials included grafted film and sulfonated membrane samples having various degrees of grafting. Original PFA film was used as a reference material. The results of the X‐ray photoelectron spectral analysis show that PFA film undergoes changes in terms of chemical compositions and binding energies of its basic elemental components under the influence of membrane preparation procedure, i.e., grafting and sulfonation. The chemical compositions of the surfaces of the membranes were found to be dependent on the degree of grafting unlike the binding energies of their elemental components (C, F, O, and S), which were found to be independent of the degree of grafting. The atomic ratio of F/C was found to decrease drastically with the increase in the degree of grafting and the membranes were found to have almost pure hydrocarbon structure at the layers close to their surfaces where degradation is suggested to be concentrated. The results of these investigations suggest that the morphology of the membranes plays an important role in the chemical degradation of the membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2455–2463, 2000     

Modification of polypropylene fiber by radiation-induced graft copolymerization of acrylonitrile monomer

Modification of polypropylene fiber was carried out by graft copolymerization of acrylonitrile monomer using the preirradiation method. The influence of synthesis conditions (preirradiation dose, monomer concentration, temperature, draw ratio, and storage) on the degree of grafting was investigated. For all preirradiation doses, the degree of grafting was found to increase with the reaction time. The higher the preirradiation dose, the higher the degree of grafting was. The dilution of monomer with DMF showed peak maxima for the degree of grafting at 80% monomer concentration. Both the initial rate of grafting and the final degree of grafting were found to increase with an increase in the reaction temperature. An activation energy of 31.2 kJ/mol was found for the grafting reaction. The degree of grafting in the drawn fiber showed different behavior as compared to the undrawn fiber. The storage of the irradiated fiber at −4°C prior to the grafting showed a decrease in the degree of grafting initially for a period of 8 days, beyond which the degree of grafting remained constant. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1343–1348, 1998     

A novel β‐nucleating agent for isotactic polypropylene

The nucleating ability of p‐cyclohexylamide carboxybenzene (β‐NA) towards isotactic polypropylene (iPP) was investigated by differential scanning calorimetry, X‐ray diffraction, polarized optical microscopy and scanning electron microscopy. β‐NA is identified to have dual nucleating ability for α‐iPP and β‐iPP under appropriate kinetic conditions. The formation of β‐iPP is dependent on the content of β‐NA. The content of β‐phase can reach as high as 96.96% with the addition of only 0.05 wt% β‐NA. Under non‐isothermal crystallization the content of β‐iPP increases with increasing cooling rate. The maximum β‐crystal content is obtained at a cooling rate of 40 °C min^–1. The supermolecular structure of the β‐iPP is identified as a leaf‐like transcrystalline structure with an ordered lamellae arrangement perpendicular to the special surface of β‐NA. Under isothermal crystallization β‐crystals can be formed in the temperature range 80–140 °C. The content of β‐crystals reaches its maximum value at a crystallization temperature of 130 °C. © 2012 Society of Chemical Industry     

马来酸酐/苯乙烯多单体接枝低等规聚丙烯

低等规聚丙烯（LIPP）是由等规立构和间规立构组成的嵌段共聚物，具有低的结晶性能，良好的粘接性和加工性能，在胶粘剂领域有着广阔的应用前景。然而LIPP的非极性和低的机械性能限制了它的应用。本文采用溶液法，以过氧化二异丙本（DCP）为引发剂，以苯乙烯（St)作为共聚单体，将马来酸酐（MAH）接枝到低等规聚丙烯（LIPP）大分子链上，采用化学滴定法测定产物（LIPP－g-MAH-St)的接枝率（GR），并系统地研究了加料方式，单体用量，引发剂用量，反应时间等因素对GR的影响，结果表明，采用先加入引发剂的加料方式有利于马来酸酐对低等规聚丙烯的接枝反应，反应的最佳条件是：反应时间7h，MAH的加入量为9份（以100份LIPP计），引发剂DCP的加入量为0．45份。     

Radiation‐induced graft copolymerization of MMA monomer onto UHMWPE: Adhesion improvement

Graft copolymerization of methyl methacrylate monomer onto ultra high molecular weight polyethylene (UHMWPE) and acid‐etched UHMWPE was conducted using preirradiation method in air in the presence of a Mohr salt and sulfuric acid to improve adhesion to the bone cement. The grafted samples were characterized by Fourier transform infrared (FTIR) spectroscopy, gravimetric method, goniometry, and interfacial bonding strength measurements. The FTIR results showed the presence of ether, carbonyl, and hydroxyl groups for grafted films. The gravimetric results showed that the chromic acid etching and graft copolymerization had a synergetic effect so, the irradiated, then chromic acid etched at room temperature and grafted sample (Rad etch25) had the highest grafting degree. The interfacial bonding strength between UHMWPE and poly methyl methacrylate bone cement was considerably improved by graft copolymerization and chromic acid etching. The surface morphology was studied by scanning electron microscopy. The substitution of polar groups into the backbone of UHMWPE by chromic acid etching and graft copolymerization changed its contact angles with water and methylene iodide and increased its surface energy, as evidenced by contact angle measurements. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Radiation‐induced graft copolymerization of α‐methyl styrene and butyl acrylate mixture into polyetheretherketone films

Radiation‐induced graft copolymerization of α‐methyl styrene (AMS), butyl acrylate (BA) monomers, and their mixture was investigated on poly(etheretherketone) films. The graft polymerization was carried out using ethyl methyl ketone as the medium for the copolymerization and the maximum degree of grafting of 27% was achieved. It was observed that the grafting is significantly influenced by the reaction conditions, such as reaction time, preirrradiation dose, monomer concentration, monomer ratio, and the reaction temperature. The degree of grafting increases as the monomer concentration increases up to 30%, beyond which a decrease in the grafting was observed. The degree of grafting showed a maximum at 40% BA content in the monomer mixture. The temperature dependence of the grafting process shows decreasing grafting with the increase in the reaction temperature. The presence of AMS and BA grafts in the film was confirmed by FTIR spectra. The relative change in the PBA/PAMS fraction with respect to the reaction temperature has been found in this study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚丙烯纤维接枝苯乙烯的研究

采用化学接枝法以苯乙烯(St)为接枝单体、过氧化苯甲酰(BPO)为引发剂,1,2-二乙烯苯(DVB)为交联剂、甲醇和正辛醇为溶剂,对聚丙烯(PP)纤维进行接枝改性。研究了原料配比和反应条件对其接枝的影响。结果表明,PP纤维上接枝St,适宜的原料配比和操作条件为:St质量与PP体积比(St/PP)为4,BPO质量与St体积比(BPO/St)为0.025,DVB与St体积比(DVB/St)为0.025,溶剂与St体积比为5,浸渍24～30h,在85℃恒温水浴中反应6～8h。在较佳条件下可得到导入率为110%-160%的接枝纤维。