Melt grafting of glycidyl methacrylate onto polypropylene and reactive compatibilization of rubber toughened polypropylene

Free radical melt grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) was studied. The extent of GMA grafting and the molecular weight of the functionalized PP copolymers were controlled by carefully manipulating various reaction factors, such as monomer concentration, initiator concentration, reaction temperature, and molecular weight of the starting PP homopolymer. The use of a second monomer, styrene, in the grafting process helped to increase GMA grafting further and reduce chain scission. The GMA modified PP copolymer was found to be able to reactively compatibilize PP/acrylonitrile-co-butadiene-co-acrylic acid rubber (NBR) blends. Up to an eight-fold increase in the impact energy of the PP/NBR blend was obtained. The compatibilizing capacities of the reactive copolymers, in terms of impact energy improvement of the PP/NBR blend, were found not to be exclusively dependent on the total concentration of reactive functionalities in the matrix of the blend. The characteristics of the reactive copolymers, i.e., the extent of functionalization and the molecular weight, were found to have significant influences on the compatibilizing capacity. A large amount of moderately functionalized copolymer offers better compatibilization performance than a small amount of highly functionalized copolymer. A significant drop in impact energy was observed with declining molecular weight of the copolymer.     

Reactive grafting of glycidyl methacrylate onto polypropylene

This work explored the melt‐phase grafting of glycidyl methacrylate (GMA) onto polypropylene on a closely intermeshing corotating twin‐screw extruder (16‐mm screws, 40 : 1 length/diameter ratio). The modification of the base polypropylene to produce GMA‐grafted polypropylene was achieved via peroxide‐induced hydrogen abstraction from the polypropylene followed by the grafting of the GMA monomer or by the grafting of styrene followed by copolymerization with the GMA. In this study, both the position and order of the reactant addition were investigated as a route to improving graft yields and reducing side reactions (degradation). For the peroxide–GMA system, adding GMA to the melt before the peroxide resulted in significant improvements in the graft levels because of the improved dispersion of GMA in the melt. The addition of a comonomer (styrene) was explored as a second route to improving the graft yield. Although the addition of the comonomer led to a considerable rise in the level of grafted GMA, altering the order of the reactant addition was not found to contribute to an increase in the grafted GMA levels. However, variable levels of grafted styrene were achieved, and this may play an important role in the development of grafted polymers to suit specific needs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solid-phase grafting of glycidyl methacrylate onto polypropylene

Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) powder was studied in a batch mixer. The reaction temperature was below the melting point of PP so that PP was modified in the solid phase. The graft yield of GMA obtained under various experimental conditions allowed for a good appreciation of the effects of chemical parameters (the concentration of monomer, initiator, and interfacial agent) and those of processing parameters (reaction time and temperature). Toluene was used as an interfacial agent to etch the surface of PP powder to provide more sites for reaction. Quantitative determination of the graft level was performed by wet chemical methods. The results showed that the solid-phase grafting could take place over a temperature range of 100–140°C in the initiation of benzoyl peroxide (BPO). The ultimate GMA grafting level achieved was higher than that obtained in the melt state with dicumyl peroxide (DCPO) as a radical initiator. The grafting of GMA affected the crystalline morphology of PP and speeded up the crystallization process. The energy of activation and initial decomposition temperature of grafted samples were higher than those of ungrafted PP. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1905–1912, 1997     

Free radical grafting of glycidyl methacrylate onto polypropylene in a co-rotating twin screw extruder

Free radical grafting of glycidyl methacrylate (GMA) onto molten polypropylene (PP) was studied in a co-rotating twin screw extruder. Grafting yields of GMA obtained under various experimental conditions along the screw length allowed for a good appreciation of the effects of chemical parameters (the presence of styrene and the concentrations of peroxide and monomers) and those of processing parameters (feed rate, screw speed, and specific throughput). Similar to the results obtained in a batch mixer,¹ free radical grafting of GMA carried out in the extruder in the presence or absence of styrene proceeded rapidly, as it was virtually completed half-way down stream of the extruder. Additionally, the presence of styrene as a second monomer increased the GMA grafting yield reatly with reduced PP chain degradation. The ultimate GMA grafting yield increased with increasing concentration of peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene. This similarity between the batch mixer and the extruder is related to the fact that in both cases it is the concentration of the peroxide and its half lifetime that determine the grafting rate and the ultimate grafting yield. On the othe hand, the GMA grafting yield decreased with increasing screw speed or feed rate. For a particular specific throughput (the ratio of throughput to screw speed), an increase in throughput with a concomitant increase in screw speed brought about a decrease in GMA grafting yield. It was concluded that the GMA grafting yield is affected primarily by the residence time in the zone in which free radicals are not depleted. The effects of screw speed, feed rate, and specific throughput manifest mainly through this local residence time distribution. Specific energy is not a good measure of the performance of the extruder with respect to the free radical rafting of GMA onto PP. © 1995 John Wiley & Sons, Inc.     

Reconsideration on the mechanism of free-radical melt grafting of glycidyl methacrylate on polyolefin

The styrene (St) assisted melt grafting of glycidyl methacrylate (GMA) on polyolefin was carried out by Haake mixer, and the grafting mechanism was investigated and reconsidered. It was revealed that there is equilibrium of grafting of GMA and depolymerization of grafted PGMA chains in the GMA/polyolefin grafting process, which was affected by both of the temperature and GMA concentration. It was found that the depolymerization of PGMA grafted on polyolefin occurred at the temperature above ceiling temperature of PGMA and dominated the grafting process before the addition of styrene monomer, which induced the decrease in grafting ratio of GMA. Adding styrene as co-monomer could promote the equilibrium moving forward to form the St-GMA chains so that the grafting ratio was greatly improved. It is proved that either controlling the reacting temperature below the ceiling temperature or changing the feeding order of styrene and GMA is effective to attain high grafting ratio of GMA on polyolefin.     

Melt grafting of a long-chain unsaturated carboxylic acid onto polypropylene

The melt grafting of a long-chain unsaturated carboxylic acid such as oleic acid (OA) and undecylenic acid (UA) onto polypropylene (PP) in a Haake Rheocord RC90 mixer was studied. The influence of initiator concentration, monomer concentration and reaction temperature on grafting was investigated. The experimental results show that a higher degree of grafting was obtained using mixed initiators (DCP/BPO=1:1). Increasing the monomer concentration leads to an initial rapid increase in the degree of grafting. The addition of styrene reduced the degradation of PP as well as the degree of grafting. The monomer chain length influenced grafting significantly, the degree of grafting decreasing with increasing chain length of the grafting monomer. The results of differential scanning calorimetry (DSC) indicated that the crystalline properties of PP grafted with OA and UA were different from those of PP grafted with acrylic acid (AA), which may be attributed to the nucleation effect of the grafted long chain of OA and UA.     

Sulfonation of (glycidyl methacrylate) chains grafted onto nonwoven polypropylene fabric

Sulfonation of polyglycidyl methacrylate (PGMA) chains grafted onto nonwoven polypropylene fabric is investigated in detail. Sulfonation reaction consists in implantation of sulfonate groups via epoxy ring‐opening of PGMA chains grafted onto nonwoven polypropylene fabric by reaction between the GMA‐grafted sample and sodium hydrogensulfite in water–dimethylformamide solution. On the basis of analyses of IR spectra of the appropriate samples and data of backward titration, two simultaneous processes are demonstrated to take place during the sulfonation reaction. These processes are the implantation of sulfonate groups via opening of the GMA epoxy rings and hydrolysis of the GMA epoxy rings with α‐glycol groups formation. The main peculiarities of the sulfonation reaction in depending on the GMA grafting degree are reported. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Grafting of glycidyl methacrylate onto gelatin

Gelatin was graft copolymerized with poly(glycidyl methacrylate) using potassium peroxydisulfate in aqueous medium. Effect of temperature, time, initiator, monomer, and backbone concentrations were studied. The percent grafting was found to increase initially and then decrease in all the cases except with variation of monomer concentration. The rate of grafting, grafting efficiency, and percent of grafting were calculated. The grafting results have been discussed in the light of the rate of grafting. Mechanical properties, FT IR spectra, percent swelling, and percent dye uptake were carried out on the graft copolymerization and the results discussed.     

Gamma preirradiation and grafting of 2N-morpholino ethyl methacrylate onto polypropylene fabric

The radiation-induced grafting of 2N-morpholino ethyl methacrylate (MEMA) in aqueous solution onto polypropylene fabric by a preirradiation technique has been investigated. Among the most important factors affecting the graft yield are monomer concentration, irradiation dose, reaction temperature, and time. It was found that the graft yield increased with increasing monomer concentration, grafting temperature, and preirradiation dose. The kinetic studies showed that the dependence of the grafting rate on monomer concentration is of 1.1 order. Moreover, the calculated overall activation energy was 14.2 kcal/mol. The grafted PP fabric shows an increase in moisture regain with increasing graft yield. Also, the dyeability with acid dye was significantly increased due to grafting with MEMA. © 1995 John Wiley & Sons, Inc.     

Graft-copolymerization of glycidyl methacrylate onto cotton cellulose

Glycidyl methacrylate was graft-copolymerized onto cotton cellolose using both photo-and chemical-initiation techniques using different initiators. The photoinitiators used were uranyl nitrate, ceric ammonium nitrate, and benzoin ethyl ether, whereas the chemical initiators used were ceric ammonium nitrate and potassium persulfate. Optimization of various parameters of grafting, viz., time, temperature, initiator, and monomer concentrations, was carried out. Ceric ammonium nitrate gave the maximum and almost identical values of graft add-on, by both grafting techniques, at equivalent cocentration of the monomer. Use of optimized conditions of ceric ammonium nitrate-photoinitiated grafting for sodium hydroxide-swollen substrate as well as for grafting baths incorporating acids enhanced the graft level. © 1994 John Wiley & Sons, Inc.     

Free radical grafting of itaconic acid and glycidyl methacrylate onto PP initiated by organic peroxides

Comparative analysis was conducted to learn the grafting of itaconic acid (IA) and glycidyl methacrylate (GMA) onto polypropylene (PP) in the course of reactive extrusion. Seven organic peroxides, which satisfactorily dissolve in PP, but do not dissolve in the monomer, were used to initiate free‐radical reactions. The grafting of IA and GMA onto PP initiated by certain peroxides gave approximately equal amounts of grafted product. It was learned that the nature of peroxide initiators is decisive for grafting efficiency and degree of macromolecular degradation. To ensure a high yield of grafted product, it is advisable to use peroxides, which have thermodynamic affinity with PP and the temperature range of decomposition of which corresponds to the thermal regime of reactive extrusion. Di(tert‐butyl peroxy‐isopropyl)‐benzene (P‐14) appeared to meet for the most these requirements for grafting both GMA and IA. Grafting is accompanied by β‐decomposition of the chains irrespective of the type of peroxide and monomer used; hence, the MFI increases. A considerable rise in MFI was observed at a minimum peroxide concentration (0.1wt %). Degradation of PP during modification eases its crystallization from the melt. In this case the crystallization temperature is 5 to 8.5°C higher than of the original PP, and the crystallinity degree increases by 20 to 60%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 64–72, 2002     

Nondegradative melt functionalization of polypropylene with glycidyl methacrylate

The melt grafting of glycidyl methacrylate (GMA) onto powdered isotactic polypropylene (PP) in a Haake Rheocord RC90 mixer was studied. Grafting degrees were determined by nonaqueous back titration of trichloroacetic acid with sodium hydroxide. The extent of degradation and crosslinking of PP during grafting was indicated by the melt-flow rates (MFR) of the grafted samples. The influences of GMA concentration, initiator type and concentration on grafting degree, reaction efficiency, and degradation were evaluated. A novel method was developed to obtain a high grafting degree with little degradation of PP using acrylamide (AM) as the initiating agent. The grafting process occurred before or during the melting of PP (i.e., solid-state grafting), at which temperature crosslinking is preferred over chain scission. Primary free radicals generated from the rapid decomposition of AM have a higher tendency to attack GMA molecules than PP chains. At the same estimated amount of primary radicals, both grafting degree and grafting efficiency increase with decreasing decomposition temperature of the initiator (for the same decomposition half-life) in the order of AM > benzoyl peroxide (BPO) > 2,5-di(t-butylperoxy)-2,5-dimethyl-3-hexyne (LPO). FunctionalizedPP with the desired grafting degree and little degradation of PP could be obtained by the use of mixed initiators. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1957–1963, 1998     

Styrene‐assisted melt free radical grafting of glycidyl methacrylate onto an ethylene and propylene rubber

This article deals with the efficiency of using styrene (St) as a comonomer to promote the melt free radical grafting of glycidyl methacrylate (GMA) onto an ethylene and propylene rubber (EPR) in a batch mixer and a corotating self‐wiping twin screw extruder. The addition of St to an EPR/GMA/peroxide system increases not only GMA's grafting yield but also its grafting rate. The time required for the EPR/GMA/peroxide system without St to reach a given amount of grafted GMA is at least 10 times that needed for the same system in the presence of an equimolar amount of St. For example, about 60 min are required for the EPR/GMA/dicumyl peroxide (composition: 100/3.0/0.3 by weight) to reach 1.5 phr (parts per hundred resin) GMA (i.e., 1.5 g grafted GMA per 100 g EPR). The same amount of grafted GMA is reached in < 3 min when 3.0 phr St is charged to the system. This significant reduction of reaction time is crucial for a successful free radical grafting of GMA on EPR in a corotating twin screw extruder, because the residence time in such a machine is typically on the order of 0.5–5 min. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 125–133, 1999     

Structurally bound stabilizers: Melt grafting of UV stabilizers onto polypropylene,polyethylene, and polystyrene

Monomeric ultraviolet stabilizers, 2-hydroxy-4-methacryloyloxy benzophenone and 2-hydroxy-4-acryloyloxy benzophenone were synthesized by a modified process. These reactive UV stabilizers were grafted onto the backbone of polypropylene (PP), low-density polyethylene (LDPE), and polystyrene (PS) by melt processing in the mixer of Brabender Plasticorder. An infrared spectroscopic method was standardized for the quantitative determination of the extent grafting of these additives on the polymer backbone. Grafting of both the additives occurred in the order PS > LDPE > PP. Methacryloxy derivative of benzophenone was found to be more reactive towards the polymers studied than the acryloxy derivative.     

利用反应挤出的聚丙烯熔融接枝改性

系统简介了聚丙烯熔融接枝体系的组成、机理及实现熔融接枝的反应挤出技术。介绍了聚丙烯接枝物的表征和应用状况，并指出了熔融接枝体系中存在的问题。     

Tributylborane-initiated grafting of methyl methacrylate onto chitin

The grafting of methyl methacrylate (MMA) onto chitin initiated by tributylborane (TBB) was investigated at ordinary temperature. It was found that water was essential to the grafting. No grafting was observed in the usual organic solvents such as n-hexane, tetrahydrofuran, and cyclohexanone. The total conversion and the percentage and efficiency of grafting increased with increasing chitin content. The extent of homopolymer formation also increased with increasing chitin content. The optimum concentrations of TBB and MMA for the grafting were determined. Activation energies were estimated to be about 22.8 and 27.4 kcal/mole for the grafting and homopolymerization, respectively. On the basis of these results the mechanism of the grafting onto chitin was discussed.     

聚丁二烯橡胶接枝苯乙烯本体自由基聚合机理

采用傅里叶变换红外光谱法和碘值法分析了在热引发和化学引发方式下,低顺式和高顺式聚丁二烯橡胶接枝苯乙烯聚合物的双键结构和含量,确定了橡胶接枝苯乙烯本体自由基聚合机理。结果表明,热引发时,接枝机理主要是自由基夺取橡胶链上α氢原子;而化学引发时,同时存在自由基与橡胶双键加成的机理。橡胶的结构不同导致接枝点的位置差异,在低顺式聚丁二烯橡胶体系中,自由基以夺取反式-1,4-结构和1,2-乙烯基结构为主,而在高顺式聚丁二烯橡胶体系中。自由基以夺取顺式-1,4-结构为主。     

Melt grafting of maleic anhydride onto polypropylene with 1‐decene as a second monomer

The influence of 1‐decene as the second monomer on the melt‐grafting behavior of maleic anhydride (MAH) onto polypropylene (PP) was studied with differential scanning calorimetry and Fourier transform infrared spectroscopy. We found that the value of the grafting degree increased from 0.68% for pure MAH‐g‐PP to 1.43% for the system with a 1‐decene/MAH molar ratio of 0.3, whereas the maximum value with styrene (St) as the second monomer was 0.98% under an St/MAH molar ratio of 1.0. Compared with the contribution of St/MAH‐g‐PP to the peeling strength between the PP and polyamide (PA) layer for a PP/PA laminated film, the introduction of 1‐decene/MAH‐g‐PP increased the peeling strength from 180 g/15 mm to 250 g/15 mm. 1‐Decene inhibited the chain scission behavior of PP. 1‐Decene reacted with MAH to form a 1‐decene/MAH copolymer or the Alder‐ene reaction product before the two monomers grafted onto PP. The grafting of the reactive product onto PP greatly improved the grafting degree of MAH. What is more, because of the similar chemical structures of 1‐decene and PP, the affinity of 1‐decene with PP was higher than that of St. Compared with St, the introduction of less 1‐decene led to a higher grafting degree and higher peeling strength. Therefore, we concluded that 1‐decene was more effective for improving the grafting degree of MAH onto PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reactive processing of polymers: Melt grafting of glycidyl methacrylate on ethylene propylene copolymer in the presence of a coagent

Glycidyl methacrylate (GMA) was grafted on ethylene–propylene copolymer during melt processing with peroxide initiation in the presence and absence of a more reactive comonomer (coagent), trimethylolpropane triacrylate (Tris). The characteristics of the grafting systems in terms of the grafting reaction yield and the nature and extent of the competing side reactions were examined. The homopolymers of GMA (Poly‐GMA) and Tris (Poly‐Tris) and the GMA‐Tris copolymer (GMA‐co‐Tris) were synthesized and characterized. In the absence of the coagent, high levels of poly‐GMA, which constituted the major competing reaction, was formed, giving rise to low GMA grafting levels. Further, this grafting system resulted in a high extent of gel formation and polymer crosslinking due to the high levels of peroxide needed to achieve optimum GMA grafting and a consequent large drop in the melt index (increased viscosity) of the polymer. In the presence of the coagent, however, the grafting system required much lower peroxide concentration, by almost an order of magnitude, to achieve the optimum grafting yield. The coagent‐containing GMA‐grafting system has also resulted in a drastic reduction in the extent of all competing reactions, and in particular, the GMA homopolymerization, leading to improved GMA grafting efficiency with no detectable gel or crosslinking. The mechanisms of the grafting reactions, in the presence and absence of Tris, are proposed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1401–1415, 2001