稀土化合物参与的聚丙烯反应挤出接枝马来酸酐

将多种稀土化合物用于等规聚丙烯(iPP)与马来酸酐(MAH)的接枝反应, 对接枝共聚物的结构、 接枝率和加工行为等进行了表征和研究. 结果表明, 稀土氧化物CeO2和Nd2O3的加入促进了iPP熔体接枝MAH的反应, 与未加入稀土化合物的接枝体系相比, MAH单体接枝率最大值分别提高了14%和25%, 同时接枝共聚物的熔体流动速率(MFR)也分别增大了34%和56%. 根据实验条件下接枝共聚物的MFR与MAH单体接枝率间的关系, 并结合熔体接枝反应机理, 提出了采用MFR来表征接枝率的方法, 并建立了工作曲线. 同时, 对不同稀土化合物抑制或促进熔体接枝反应发生的机理进行了初步探讨.     

Grafting of glycidyl methacrylate onto polypropylene using supercritical carbon dioxide

Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studied using supercritical carbon dioxide (SC-CO₂) as a solvent and a swelling agent. As the reaction temperature was below the melting point, PP was modified in the solid phase. The PP film was first soaked with the monomer GMA and benzoyl peroxide (BPO) as an initiator using SC-CO₂ at different experimental conditions of pressure, temperature, and thermal treatment time. After releasing CO₂, film GMA molecules were grafted onto PP in different times. Using this method, the degree of grafting and the morphology could be controlled through the combination of pressure, temperature, and soaking time. FTIR spectra confirmed that GMA had been grafted onto PP and that polypropylene-graft-glycidyl methacrylate (PP-g-GMA) presented a high surface reactivity for conductive polyaniline anchoring. DSC measurements and TG analyses showed that the thermal profiles of the graft copolymer and virgin PP are quite similar and that the graft PP does not exhibit changes in terms of thermal degradation profile and melting temperature, respectively. X-ray data showed that a high degree of grafting leads to a lower degree of crystallinity of polypropylene.     

聚丙烯与马来酸酐在超临界CO2中的接枝聚合

聚丙烯(PP)以其强度高、耐热性好、密度小、易加工和价廉等特点成为重要的通用塑料。但由于非极性的分子结构,其亲水性、染色性、抗静电性、粘接性和印刷性并不理想,难以与极性聚合物和填料共混、复合。PP通过接枝引入极性基团是最常用的化学改性方法。常用的接枝单体有马来     

In situ FT-IR spectroscopic study on the conformational changes of isotactic polypropylene in the presence of supercritical CO2

The conformational changes of isotactic polypropylene (iPP) under supercritical CO₂ condition with different pressure and temperature have been carefully studied by in situ Fourier-transform infrared spectroscopy (FT-IR). Analysis of the corresponding spectra shows that the conformational ordering by supercritical CO₂ results in the intensity enhancement of the regularity bands of iPP. Due to the high CO₂ concentration and strong intermolecular interaction, iPP can reach an equilibrium state in a short time at high CO₂ pressure. The equilibrium time increases with soaking temperature. After supercritical CO₂ treatment, two mechanisms, the formation of short helix from amorphous phase and the extension of short helix into long one, happen simultaneously. The latter mechanism undergoes quickly at the beginning of induced conformational changes and then slows down, resulting in the slight increase of crystallinity. At the same time, the conformational ordering in amorphous phase happens continuously until a thermodynamic equilibrium. In summary, in the presence of supercritical CO₂, the conformational ordering of iPP chains occurs exclusively in the amorphous region, with no impact on the crystal part.     

马来酸酐-苯乙烯多组分单体熔融接枝高密度聚乙烯机理及性能研究

用单螺杆挤出机制备了马来酸酐-苯乙烯(MAH-St)多单体熔融接枝高密度聚乙烯(HDPE)体系,研究发现添加St共同接枝,可以显著提高接枝物的接枝率.随着St的增加,接枝率先增大后有所降低.当两种单体物质的量比约为1:1时,接枝物的接枝率最高,此时接枝物的熔体流动速率(MFR)最小.即MAH接枝率越高,接枝物的MFR越...     

Synthesis and crystallization behavior study of syndiotactic polystyrene‐g‐isotactic polypropylene (sPS‐g‐iPP) graft copolymers

Based on coordination polymerization mechanism only, novel stereoregular graft copolymers with syndiotactic polystyrene main chain and isotactic polypropylene side chain (sPS‐g‐iPP) were synthesized via two steps of catalytic reactions. First, a chain transfer reaction was initiated by a chain transfer complex composed of a styrene derivative, 1,2‐bis(4‐vinylphenyl)ethane, and hydrogen in propylene polymerization mediated by rac‐Me₂Si[2‐Me‐4‐Ph(Ind)]₂ZrCl₂ and MAO, which gave iPP macromonomer bearing a terminal styryl group (iPP‐t‐St). Then the iPP‐t‐St macromonomers of varied molecular mass were engaged in syndiospecific styrene polymerization over a typical mono‐titanocene catalyst (CpTiCl₃/MAO) under different conditions to produce sPS‐g‐iPP graft copolymers of varied structure. With an effective purification process, well‐defined sPS‐g‐iPP copolymers were obtained, which were then subjected to differential scanning calorimetry (DSC) and polarized optical micrograph (POM) studies. The graft copolymers were generally found with dual melting and crystallization temperatures, which were ascribable respectively to the sPS backbone and iPP graft. However, it was revealed that the two segments displayed largely different melting and crystallization behaviors than sPS homopolymer and the precursory iPP‐t‐St macromonomer. Consequently, the graft copolymer exhibited much distinctive crystalline morphologies when compared with their individual components. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

1,6-己二醇二丙烯酸酯和苯乙烯多单体熔融接枝制备长支链聚丙烯研究

采用哈克转矩流变仪制备了1,6-己二醇二丙烯酸酯(HDDA)和苯乙烯(St)多单体熔融接枝聚丙烯(PP)体系.红外测试结果表明St的加入能够促进HDDA接枝到PP主链,提高接枝率.动态流变行为研究结果也表明采用多单体熔融接枝PP更有利于体系在熔融接枝中生成长支链(LCB).随着St单体添加量的增加,HDDA的接枝率增大...     

ABS的MAH/St多单体熔融接枝及其对PA6/ABS共混体系相形态和力学性能的影响

通过多单体熔融接枝的方法制备出了具有较高接枝率的ABS接枝物 (ABS g (MAH co St) ) ,并对其接枝机理进行了初步探讨 .研究表明 ,MAH、St接枝ABS时 ,反应主要发生在ABS中聚丁二烯的双键部位 .同时 ,当MAH与St的用量比约为 1:1时接枝率达到最高 .ABS g (MAH co St)作为尼龙 6 (PA6 ) ABS共混体系相容剂起到了良好的增容效果 .实验证明 ,相容剂使用前后 ,共混物的相区尺寸由几十 μm减小到 1μm以下 ,且分布更加均匀 ;共混物的拉伸强度和冲击强度等力学性能也同时得到均衡改善 .     

Control of degradation of polypropylene during its radical functionalisation with furan and thiophene derivatives

The traditional melt radical functionalisation of isotactic polypropylene (iPP) with maleic anhydride (MAH) and peroxide affords functionalized samples with a severe decrease of the average molecular weight (MW) due to the β-scission reaction. In this work new push-pull unsaturated molecules were investigated, consisting of a heterocyclic ring conjugated with a double bond bearing an electron attracting group. These molecules were specifically designed as MAH substitute able to limit the iPP degradation, while providing functionalisation through grafting. Butyl 3-(2-furanyl) propenoate (BFA) and butyl 3-(2-thienyl) propenoate (BTA) were comparatively tested. The analysis of the reaction products indicated that both molecules are able to graft onto the iPP backbone by prompt reaction with the macro-radicals formed through H-abstraction from iPP chains, thereby significantly limiting the MW decrease, as the functionalized macro-radicals are stabilized by resonance. Nonetheless, some of iPP macro-radicals can give a parallel chain scission before reacting with the new molecules. In the case of BFA, coupling reactions of the formed macro-radicals can lead to the formation of branched high MW architectures, whereas in the case of the thiophene derivative (BTA) only a partial retaining of polymer chain fragmentation was observed due to the reduction of β-scission.     

Grafting copolymerization of styrene and maleic anhydride binary monomer systems induced by UV irradiation

Photografting copolymerization of maleic anhydride (MAH) and styrene (St) onto LDPE film was investigated by using a one-step method, and further thermally induced grafting copolymerization of them was carried out by using a two-step method. Regarding the photografting copolymerization of MAH/St binary monomer system, both conversion percentage (CP) and grafting efficiency (GE) increased with raising the content of MAH in the monomer feed. In addition, the content of MAH in the grafted copolymers also increased with increasing the fraction of MAH in the monomer feed. The formation of LDPE-g-P(MAH-co-St) grafted film was identified by FTIR and ESCA spectroscopy. In the case of grafting copolymerization of MAH/St by the two-step method, grafting copolymerization proceeded slowly compared with the non-grafting copolymerization. The apparent activation energy (E_a) for the non-grafting copolymerization in the solution and the grafting copolymerization on LDPE film was 24 and 82 kJ/mol, respectively, which were noticeably lower than those of MAH/vinyl acetate (MAH/VAC) binary monomer system under the similar grafting conditions. These data of E_a explained why the grafting copolymerization of styrene/MAH took place faster than that of MAH/VAC binary monomer system. The composition of the grafted copolymer chains was largely affected by the composition of the monomer feeds; however, the composition of the non-grafted copolymers nearly remained at 1/1 even in systems with largely different MAH/styrene ratios in monomer feeds. It is indicated that the non-grafting copolymerization proceeded predominantly following alternating copolymerization, but the grafting copolymerization performed random copolymerization.     

Neodymium oxide‐assisted melt free‐radical grafting of maleic anhydride on isotactic‐polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd₂O₃), ‐assisted melt free‐radical grafting of maleic anhydride (MAH) on isotactic‐polypropylene (i‐PP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd₂O₃ into reactive system leads to an enhancement of the grafting degree of MAH, along with an elevated degradation of i‐PP matrix. When Nd₂O₃ content is 4.5 mmol %, the increment of the grafting degree of MAH (maximally) is up to about 30% compared with that of the related system without adding Nd₂O₃, while the severest degradation of i‐PP matrix simultaneously occurs. On the basis of the reaction mechanism of PP‐g‐MAH proposed before, the sequence of β‐scission and grafting reaction is discussed in detail. It is found that, for the reactive system studied, most tertiary macroradicals first undergo β‐scission, and then, grafting reaction with MAH takes place at the new radical chain ends. The imported Nd₂O₃ has no effect on the aforementioned reaction mechanism, whereas it enhances the initiating efficiency of the initiator, dicumyl peroxide (DCP). We tentatively explain the experimental results by means of synergistic effect between DCP and Nd₂O₃. It is calculated that the synergistic effect is maximal when the molar ratio of DCP to Nd₂O₃ is approximately 1:6. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 134–142, 2006     

Solvothermal process for grafting maleic anhydride onto poly(ethylene 1-octene)

Solvothermal process was developed to graft maleic anhydride (MAH) onto poly(ethylene 1-octene) (POE). Fourier transform infrared spectra (FT-IR) and ¹H NMR spectra confirmed that maleic anhydride was successfully grafted onto the POE. The influences of MAH content, initiator concentration, POE concentration, reaction temperature, reaction time and solvents on the graft copolymerization were investigated through both of the grafting degree (GD) and gel content (GC). The results demonstrated that high grafting degree (up to 10.85%) could be obtained while the gel content was still low. Further studies revealed that POE-g-MAH could also be achieved in poor solvents of POE through this method.     

CO2‐delayed crystallization of isotactic polypropylene: A kinetic study

The effect of CO₂ on the nonisothermal crystallization of isotactic polypropylene (iPP) was studied with high‐pressure differential scanning calorimetry at cooling rates of 0.2–5 °C/min. CO₂ significantly delayed the melt crystallization of iPP, and both the crystallization temperature and the heat of crystallization decreased with increasing CO₂ pressure. The crystallization rate of iPP, as characterized by the half‐time, was also prolonged by the presence of CO₂. With a modified Ozawa model developed by Seo, the Avrami crystallization exponent n of iPP was calculated. This value was depressed by the addition of CO₂ and was strongly dependent on the CO₂ pressure at low cooling rates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1518–1525, 2003     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Grafting of maleic anhydride onto linear polyethylene: A Monte Carlo study

Monte Carlo simulation was used to study the graft of maleic anhydride (MAH) onto linear polyethylene (PE‐g‐MAH) initiated by dicumyl peroxide (DCP). Simulation results revealed that major MAH monomers attached onto PE chains as branched graft at higher MAH content. However, at extremely low MAH content, the fraction of bridged graft was very close to that of branched graft. This conclusion was somewhat different from the conventional viewpoint, namely, the fraction of bridged graft was always much lower than that of branched graft under any condition. Moreover, the results indicated that the grafting degree increased almost linearly to MAH and DCP concentrations. On the other hand, it was found that the amount of grafted MAH dropped sharply with increasing the length of grafted MAH, indicating that MAH monomers were mainly attached onto the PE chain as single MAH groups or very short oligomers. With respect to the crosslink of PE, the results showed that the fraction of PE‐(MAH)_n‐PE crosslink structure increased continuously, and hence the fraction of PE‐PE crosslink decreased with increasing MAH concentration. Finally, quantitative relationship among number average molecular weight of the PE, MAH, and DCP contents was given. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5714–5724, 2004     

L-Proline catalyzed aldol reactions between acetone and aldehydes in supercritical fluids: An environmentally friendly reaction procedure

The direct asymmetric aldol reaction between various aldehydes and acetone catalyzed by l-proline catalyst was successfully carried out in supercritical CO₂ (scCO₂) and 1,1,1,2-tetrafluoroethane (R-134a) fluids. The enantioselectivity of 84% ee to the targeted product was achieved under 20 MPa, 40 °C, and 15 mol% of the catalyst in supercritical CO₂ (scCO₂) fluid. The effects of reaction parameters, such as temperature, pressure, catalyst loading and different substituted aldehydes on both enantioselectivity and aldol yield were discussed. The titled reaction was also performed in 1,1,1,2-tetrafluoroethane, and the obtained results were compared with those in scCO₂. This new reaction procedure provides an environmental asymmetric aldol reaction system as compared with that in organic solvents.     

等规聚丙烯接枝N-(1-萘基)马来酰亚胺的合成及其结晶形态研究

采用溶液接枝法制备了N-(1-萘基)马来酰亚胺接枝等规聚丙烯,并用红外光谱(FTIR)定量表征了接枝率,用差示扫描量热分析(DSC)和X-射线衍射(XRD)研究了其结晶形态.结果表明,随着引发剂和接枝单体用量增加,接枝率呈现先增加后降低的趋势,这一现象可从反应动力学给与合理解释.此外,还发现当接枝率小于2.1%时,接枝前后聚丙烯的结晶形态未发生明显变化.     

聚丙烯粉料固相光接枝马来酸酐的研究

聚丙烯（ＰＰ）由于其优越的性能价格比而具有广泛的用途，但ＰＰ的非极性、易氧化等缺点使其在一些重要领域中的应用受到限制，因此需采用涂层法、等离子体处理、接枝法等方法对ＰＰ改性．其中ＰＰ表面接枝共聚法可使其脱去主链氢原子，引入极性基团，改善染色性和亲水性...     

Selective permeation of CO2 through poly 2-(N,N-dimethyl)aminoethyl methacrylate membrane prepared by plasma-graft polymerization technique

A membrane having an amine moiety was prepared by plasma-grafting 2-(N,N-dimethyl)aminoethyl methacrylate (DAMA) onto a microporous polyethylene substrate. Permselectivity of the membrane for CO₂ over N₂ was achieved in both dry and water swollen conditions. When the CO₂ partial pressure in the feed gas was 0.047 atm, the selectivity of CO₂ over N₂ reached 130 for the highly swollen water containing membrane. This value was found to agree with that obtained with a mobile carrier membrane (supported liquid membrane) using DAMA as the carrier. The effects of several experimental conditions such as degree of grafting, feed partial pressure and temperature on the membrane performance were studied. It was suggested that the membrane acted as a fixed carrier membrane for CO₂ facilitated transport in under the dry condition and acted as a fixed reaction site membrane in the water swollen condition. The carrier transport mechanism is discussed for dry and aqueous membranes.     

Grafting of methyl methacrylate onto natural rubber in supercritical carbon dioxide

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber (NR) was carried out by supercritical carbon dioxide (scCO₂) swelling polymerization with benzoyl peroxide (BPO) as an initiator. Fourier transform–infrared spectroscopy (FT–IR) was used to confirm the formation of graft copolymers with the characteristic bands of symmetric C?O and C? O? C stretching vibrations at 1728 cm^?1 and 1147 cm^?1, respectively. The effects of the rubber‐to‐monomer ratio, amount of initiator, reaction time, and pressure on the monomer grafting level (GL) and grafting efficiency (GE) were investigated, and the optimum conditions for the preparation of NR‐g‐MMA were found to be 70:30 of the rubber‐to‐monomer ratio, 1.2% of the initiator content, and the reaction pressure of 23 MPa for 6 h. The thermal behavior of the NR and the different NR/MMA molar ratio grafted copolymer samples was studied by differential scanning calorimetry (DSC). The observed glass transition temperature (T_g) was consistent with the GL. The tensile strength, modulus of elasticity, elongation at break, hardness, and oil resistance of graft copolymers were determined and compared with the values of NR and that of polymerization products prepared in traditional toluene solution. The results showed that the tensile strength, modulus of elasticity, hardness and oil resistance were greatly improved after modification in scCO₂. Copyright © 2007 John Wiley & Sons, Ltd.