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.     

线性低密度聚乙烯反应挤出接枝马来酸酐的研究

以过氧化二异丙苯(DCP)为引发剂,在双螺杆挤出机中进行了马来酸酐(MAH)熔融接枝线性低密度聚乙烯(LLDPE)的研究,用红外光谱表征了接枝反应的存在。考察了引发剂用量、单体用量、螺杆转速以及温度对接枝反应的影响,并探讨了苯乙烯(St)作共单体对接枝反应的影响。研究表明:在引发剂含量较低时,用苯乙烯作共单体能够显著提高接枝率。     

LLDPE熔融接枝MAH功能化研究

以双螺杆挤出机为反应器 ,在自由基引发剂过氧化二异丙苯 (DCP)存在下 ,加入添加剂 ,采用熔融法对线型低密度聚乙烯 (LLDPE)进行马来酸酐 (MAH)接枝 ,对产物的接枝率 (Gx)、凝胶含量 (gel)以及溶体流动速率(MFR)的影响因素进行了系统的研究 ,并测试了接枝共聚物与铝片的粘接强度     

Study of multi‐monomer melt‐grafting onto polypropylene in an extruder

Free‐radical melt‐grafting of the dual‐monomer systems glycidyl methacrylate–styrene (GMA‐St) and hydroxyethyl methacrylate–styrene (HEMA‐St) onto polypropylene (PP) has been studied using a single‐screw extruder. For single monomer grafting systems, degradation of PP was unavoidable and deterioration of the mechanical properties of the grafted PP subsequently occurred because of β‐scission of PP chains during the free‐radical melt‐grafting process. However, for the dual‐monomer systems, it is shown that the addition of styrene as a comonomer can significantly enhance the GMA or HEMA grafting levels on PP and reduce the extent of β‐scission of PP backbone. It has been found that the grafting degree of dual‐monomer melt‐grafted PP, such as PP‐g‐(GMA‐co‐St) or PP‐g‐(HEMA‐co‐St), is about quadruple that of single‐monomer grafted PP for the same monomer and dicumyl peroxide concentrations. Moreover, the melt flow rate of the dual‐monomer grafted PP is smaller than that of the unmodified PP. Hence, PP not only was endowed with higher polarity, but also kept its good mechanical properties. © 2000 Society of Chemical Industry     

羟甲基丙烯酰胺熔融接枝聚丙烯亲水性的研究

分别以羟甲基丙烯酰胺（NHA）、苯乙烯（St）为接枝单体,过氧化二异丙苯（DCP）为引发剂,用双螺杆挤出机制备了聚丙烯（PP）的接枝共聚物PP-g-NHA和PP-g-NHA/St。红外分析表明,NHA和St接枝到PP链上形成接枝共聚物。探讨了NHA用量、St用量、DCP用量及加工温度、螺杆转速对接枝率及接触角的影响。结果表明,NHA的最佳用量是3 %,此时接枝率达到最大值为1.6 %,接触角最小为83 °;随着DCP用量的增加,接枝率先增大后下降;加工温度不能太高,螺杆转速一定要大于40 r/min。     

马来酸酐及苯乙烯同时接枝聚丙烯的研究

用过氧化二异丙苯(DCP)作为引发剂，采用双螺杆反应挤出的苯乙烯、马来酸酐2种单体同时接枝聚丙烯．研究了单体总浓度、单体比例、引发剂浓度对PP的接枝率、接枝效率和熔体流动速率的影响。通过实验发现苯乙烯的加入使接枝率和接枝效率比单独的马来酸酐接枝都有很大的提高。     

Graft copolymerisation of N‐vinyl pyrrolidone onto polypropylene copolymer in melt: Effect of grafting on thermomechanical properties and paint adhesion

N‐vinyl pyrrolidone (NVP) was grafted onto a polypropylene copolymer (PP) in melt in a Brabender Plasticorder and single screw extruder. The effect of variation of dicumyl peroxide (DCP) and lupersol (LUP) concentrations alone and with 20 wt % NVP concentration in the Brabender Plasticorder on Melt Flow Index (MFI) and final torque values was studied. Variation of NVP concentration (1–10 wt %) at a fixed DCP concentration on percent grafting (G) and MFI was also studied in the single screw extruder. The graft copolymers (PP‐g‐NVP) obtained by reaction of PP with NVP were soxhlet extracted with isopropanol to remove homopolymer, dried, and finally characterized by Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The PP‐g‐NVP (0–30 wt %) was used as an additive with PP, extruded in the single screw extruder, molded, and the mechanical properties and paint adhesion was measured. MFI values increased and torque values decreased with an increase in initiator concentration, indicating the dominance of the peroxide‐initiated scission reaction over grafting. DCP gave higher grafting compared to LUP. When NVP concentration was increased, MFI values increased initially due to more scission, and then decreased, indicating more graft copolymer formation. Mechanical properties increased by incorporation of PP‐g‐NVP as an additive than PP‐g‐NVP alone. Paint adhesion increased by the presence of PP‐g‐NVP as additive especially with polyurethane primer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2173–2180, 2003     

山梨醇类成核剂对改性聚丙烯发泡性能的影响

以过氧化苯甲酰（BPO）为引发剂,经熔融挤出过程将苯乙烯（St）接枝到等规聚丙烯（iPP）上,同时加入山梨醇类成核剂［1,3:2,4二（对甲基卞叉）山梨醇,MDBS］,制备可发泡的iPP,并考查MDBS在其发泡过程中所起的作用。结果发现,St接枝到iPP上,降低了iPP的熔体流动速率,即提高了其熔体强度;在发泡过程中,MDBS起固定泡孔和泡孔成核的作用,使iPP泡沫具有规则完整的泡孔结构,且泡孔密度从纯iPP的1.1×10^7个/cm3增加到1.2×10^8个/cm3,适宜发泡温度范围拓宽至150~160 ℃。     

A study of radical graft copolymerization on polypropylene during extrusion using two peroxide initiators

Functionalization of polypropylene (PP) during melt extrusion has been explored extensively. In this study, two different radical initiators were employed and compared in grafting acyclic halamine precursors to PP. 2,4‐Diamino‐6‐diallylamino‐1,3,5‐triazine (NDAM) was grafted onto PP during a melt‐extrusion process using either 2,5‐dimethyl‐2,5‐(tert‐butylperoxy)hexyne (DTBHY) or dicumyl peroxide (DCP) as initiator. The results confirmed the radical graft copolymerization of the monomer onto the PP backbone during the reactive extrusion process. It was revealed that, at low monomer concentration, when peroxide initiator concentration was increased, polymer chain scission became dominant. DCP was more efficient than DTBHY as an initiator in the graft polymerization. After exposure to chlorine bleach, the grafted structures could be easily transformed into N‐halamines, which provided powerful, durable and regenerable antibacterial activities against Escherichia coli and Staphylococcus aureus. It is concluded that both DCP and DTBHY could be used as radical initiators in reactive extrusion to graft certain vinyl monomers to PP. The NDAM‐grafted PP could provide expected antibacterial function after chlorination of the grafted product in a chlorine bleach solution. The modified PP showed great potential for use in medical devices and non‐woven textiles. Copyright © 2009 Society of Chemical Industry     

Gel formed during the solid‐state graft copolymerization of styrene and spherical polypropylene granules. I. Influence of reaction conditions on the gelation and its mechanism

Graft copolymers of polystyrene (PSt) with spherical polypropylene (PP) granules were synthesized by solid‐state reaction. In the copolymerization as a by‐product some gel was formed. The effects of the amount of free radical initiator, feed ratio of St monomer, species of free radical initiator, and composition of the spherical polyolefin granules on the grafting degree of PSt and the gelation were studied. It is found that larger amount of initiator used, and higher feed ratio of St monomer lead to a higher grafting degree and higher content of gel. During the cross‐link reaction process, both styrene and free‐radical participate in the reaction that discloses the reason of the increment of gel with the increment of styrene consumption or initiator consumption. Using PPR, which is a random copolymer of 95.1 mol % propylene units and 4.9 mol % ethylene units, as grafting matrix, higher grafting degree and higher content of gel can be reached than that using isotactic PP as grafting matrix. Using tert‐butyl peroxy benzoate (TBPB) as initiator, under the same conditions there were more PSt grafted to the spherical PP granules and more gel formed than that using benzoyl peroxide (BPO) as initiator. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3682–3687, 2007     

PP-g-GMA的制备及其改性PP/PA6合金性能

采用双螺杆熔融接枝的方法,在引发剂过氧化二异丙苯(DCP)作用下,将甲基丙烯酸缩水甘油酯(GMA)和共单体苯乙烯(St)接枝到聚丙烯(PP)上。通过傅立叶变换红外光谱仪确定了接枝物的生成,采用酸碱滴定法测定了接枝率。探讨了GMA,St,DCP不同用量对PP接枝物的接枝率和熔体流动速率的影响,并将接枝产物PP–g–(St–co–GMA)加入PP/尼龙6(PA6)的合金中,通过注塑成型样条,测定其力学性能,并观察微观结构。结果表明,St的加入能够提高接枝率,抑制副反应的发生。在PP/PA6合金中加入接枝物PP–g–(St–co–GMA),其拉伸强度可提高46.45%,弯曲强度可提高32.47%,但对冲击强度影响不大。     

季铵盐类阳离子单体接枝聚丙烯及其性能研究

以甲基丙烯酞氧乙基三甲基氯化铵 ( DMC)、苯乙烯(St),聚丙烯(PP)为原料,采用多单体熔融接枝的方法,制备了含季铰盐基团的功能化的聚丙烯。考察了几种反应因素对接枝反应的影响,测试了接枝物的力学性能,利用示差扫描量热仪、偏光显微镜研究了接枝产物的结晶性能。结果表明:引发剂过氧化二异丙苯(DCP)用量为0.6份时,DMC与St的物质的量之比为1:1时,DM《的接枝效果最佳,与纯PP相比,其拉伸强度、冲击强度基本不变,晶核密度大幅增加,总结晶速率加快,半结晶时间((tm)缩短,结晶温度(Tc)提高。     

铝塑复合管硅烷交联聚乙烯专用料的研究

研究了高密度聚乙烯（HDPE）／线性低密度聚乙烯（LLDPE）硅烷接枝交联体系。分析了过氧化二异丙苯（DCP），乙烯基三乙氧基硅烷（VTES），加工设备及工艺条件（温度，螺杆转速）对体系熔体流动速率（MFR）和凝胶含量的影响。并用Buss混炼设备制备出高流动性的铝塑复合管硅烷接枝交联PE专用料。     

新型引发剂DMDPB在LLDPE熔融接枝MAH中的应用

采用熔融接枝的方法,在双螺杆挤出机中用2,3－二甲基－2,3－二苯基丁烷（DMDPB）和过氧化二异丙苯（DCP）两种不同的引发剂将马来酸酐（MAH）接枝到线形低密度聚乙烯（LLDPE）上。用二甲苯溶解－丙酮抽提（或沉淀）法处理接枝物,用红外光谱证实了在新型引发剂DMDPB的引发下,马来酸酐成功地接上了PE。用化学实验方法定量测定了接枝率的大小和凝胶含量,结果发现DMDPB引发的接枝物无凝胶现象。通过溶体流动速率的测定说明了接枝物加工性能的优劣。并对两种引发剂做进一步的比较。     

Modification of isotactic polypropylene by the free‐radical grafting of 1,1,1‐trimethylolpropane trimethacrylate

The chemical modification of isotactic polypropylene was performed by the free‐radical‐promoted grafting of 1,1,1‐trimethylolpropane trimethacrylate (TMPTMA) in the presence of dicumyl peroxide (DCP) as the initiator. The reaction was carried out both in a batch internal mixer and in a corotating twin‐screw extruder; the effects of the peroxide and monomer concentrations on the extent of modification in terms of the grafting efficiency and polymer chain structure variations were investigated. The modified samples were characterized with Fourier transform infrared to determine the structure of the grafted groups and the degree of functionalization, with gel permeation chromatography and the melt flow index to evaluate changes in the molecular weight, and with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis to measure the final thermal properties. In addition, solvent extraction with xylene was performed to highlight the presence of gel and its extent. The structure of the grafted groups was determined, and the number of grafted groups was quantitatively evaluated. The degree of functionalization increased with an increasing TMPTMA/DCP molar ratio. Thermal analysis results hinted at the presence of grafted chains with an increased percentage of TMPTMA. Although degradation reactions predominated at high amounts of peroxide, grafting and branching processes became competitive at high levels of TMPTMA. The balance between competing β‐scission and grafting/branching reactions could be adjusted on the basis of feed conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 950–958, 2007     

Crosslinkable polypropylene composites made by the introduction of silane moieties

Silane‐crosslinkable polypropylene (PP) composites containing calcium carbonate (CaCO₃) as a filler have been investigated. The melt grafting of vinyl trimethoxysilane to PP with dicumyl peroxide (DCP) as a radical initiator is demonstrated. The thermal and mechanical properties of the crosslinkable products are also discussed. The results show that two reactions, that is, silane grafting and PP degradation, take place in parallel. The extents of silane grafting and PP degradation strongly depend on the reaction temperature, grafting formulation, and amount of the filler in the systems. Increasing the DCP concentration (up to 0.05 wt %) leads to an increase in the grafting degree. However, when the concentration of radicals is over a certain degree, the dominant reaction is PP chain scission. This results in a drastic decrease in the polymer viscosity. In systems containing both silane and CaCO₃, the viscosity of the polymer is higher than that of a grafted sample without CaCO₃ addition; in other words, the effect of the filler on the polymer viscosity compensates for the effect caused by PP degradation. Differential scanning calorimetry results show that the crystallization starts earlier for grafted samples. The percentage of the crystallinity of grafted PP is higher than that of the pure polymer. The incorporated silane does not have a strong effect on the mobility of the PP chains, as revealed by dynamic mechanical analysis. In comparison with ungrafted composites, the silane‐crosslinkable products show higher tensile stress and modulus. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1476–1483, 2005     

Melt grafting of maleic anhydride onto elastomeric ethylene‐octene copolymer by reactive extrusion

Melt grafting of maleic anhydride onto elastomeric ethylene‐octene copolymer was carried out in a twin‐screw extruder, in the presence of dicumyl peroxide as an initiator. Dimethyl formamide was used as an inhibitor to reduce crosslinking and as a solvent for peroxide initiator. The aim of the work is to produce the copolymer with reactive functionality without the expense of elastomeric characteristics. Particular consideration was, therefore, given to the effects of initiator and monomer concentrations, and of screw speed on the degree of grafting, percentage of conversion, amount of crosslinked products, and on the stress‐strain behaviors of the grafted products. The degree of grafting was found to be dependent mainly on the initiator and monomer concentrations. Increasing the initiator concentration increased the degree of grafting, and at the same time, increased the amount of gel (crosslinking). An increase in gel content of the grafted products resulted in a change of tensile behaviors from uniform deformation followed by strain‐hardening at high strains to low extensibility and fracture at low strains.     

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     

Preparation of polypropylene/acrylonitrile–styrene copolymer alloys by one‐step reactive blending

The compatibilization of polypropylene/acrylonitrile–styrene (PP/AS) blends through the addition of peroxide (DCP) was investigated in this study. The grafting reaction between PP and AS with the addition of peroxide occurred during the reactive‐blending process. The in situ‐formed grafting copolymers of PP‐g‐AS and AS‐g‐PP were then characterized by FTIR. The optimum concentration of the initiator, DCP, was 0.2 wt %, and the reaction temperature should be above 195°C. It was found that, when AS was the major component of the blends, the grafting of AS onto PP was the main process; conversely, when PP was the major component, PP was grafted onto AS. These results can be explained by the main‐chain scission of PP during the reactive‐blending process. With increase of the AS component, the total degree of grafting increased at first and then decreased after the composition of the blends reached 50/50. The maximum degree of grafting was found to be 6 wt % for the 50/50 PP/AS/DCP blend. PP was more degradable than was AS in the presence of peroxide at high temperatures. The MFR values of the PP/AS/DCP blends were slightly greater than were those of the simple PP/AS blends, which means that blending is an effective way to protect PP from degradation. SEM micrographs of the cross section of PP/AS/DCP showed a fine dispersion and a smaller domain size of the dispersed‐phase particles, implying that the in situ‐formed grafting copolymers act as a compatibilizer to reduce the interfacial tension between the PP and AS phases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1284–1290, 2001     

反应挤出法制备高熔体强度聚丙烯

以1,6己二醇二丙烯酸酯（HDDA）为接枝单体,苯乙烯（St）为共聚单体对聚丙烯（PP）进行熔融接枝,并在反应体系中加入β成核剂,从而改变PP晶型,通过接枝长支链提高聚丙烯的熔体强度。研究了螺杆转速、引发剂用量、单体摩尔比及投料量对熔体流动速率和熔体强度的影响。采用傅里叶变换红外光谱仪、热重分析仪及X射线衍射仪等对改性材料的结构和性能进行分析。结果表明,在优化的反应条件下,接枝改性PP的熔体流动速率和熔体强度分别为0.70 g/10 min,10.00 kPa·s;热稳定性也比纯PP有很大程度提高。