Functionalization of high density polyethylene in melt state through ultrasonic initiation and its effect on mechanical properties of glass fiber reinforced composites

Summary Functionalization reaction of high density polyethylene (HDPE) with γ-methacryloxy-propyltrimethoxysilane (MAS) or with MAS and MAH performed in melt state through ultrasonic initiation by a laboratory-scale ultrasonic extruding reactor was studied in this paper. The effect of ultrasonic intensity on the percentage of grafting and melt flow rate of the functionalized products was investigated. The results show that by imposing ultrasonic vibration during melt-extruding process, the scission of HDPE chain bonds can be caused to form macroradicals, the functionalization reaction of HDPE with MAS or with MAS and MAH can be realized. The percentage of grafting and the melt flow rate of the functionalized products depend upon the ultrasonic intensity and reaction temperature. The fuctionalization reaction of HDPE with MAS can be promoted by adding a second grafting monomer MAH. The ultrasonic-induced products have a higher reactivity with the coupling agents coated on the surface of glass fibers, the mechanical properties of the composite improved by the ultrasonic induced product are higher than that of by peroxide initiated product and the mechanical properties of HDPE/GF composite modified by HDPE-g-MAH-MAS are higher than that of by HDPE-g-MAH. The SEM experimental results indicate that an oriented crystal layer exists between the interface of glass fiber and the HDPE matrix, the interfacial bonding strength is the determining factor of the formation of the oriented crystal layer.     

Functionalization of high density polyethylene with maleic anhydride in the melt state through ultrasonic initiation

Grafting of maleic anhydride (MAH) onto high density polyethylene (HDPE) performed in the melt state through ultrasonic initiation by a laboratory‐scale ultrasonic extrusion reactor was studied in this paper. The effect of sonic intesity on the amount of grafted MAH, viscosity‐average molecular weight and melt flow index of the grafted product was investigated. The results show that the ultrasonic waves can obviously decrease the molecular weight of the grafted product and cause the increase of the amount of grated MAH, implying that the grafting reaction consists of the chain scission and the grafting reaction of the produced macroradicals with MAH. The percentage of grafting of the product amounts to 0.6%; its melt‐flow index is between 0.5 and 2.0 g/10 min, depending upon ultrasonic intensity, MAH content and grafting temperature. Compared with the method of peroxide initiation, in this method the crosslinking reaction can be prevented easily through the allocation of ultrasonic intensity. The mechanical properties of the improved HDPE/GF composite produced by ultrasonic initiatives are higher than in those produced by peroxide initiatives.     

HDPE functionalization via high shear stress‐induced initiation and its effects on HDPE/GF composite

The functionalization reaction of high density polyethylene (HDPE) with maleic anhydride (MAH) or with MAH and γ‐methacryloxy‐propyltrimethoxysilane (MAS) performed in melt state through a high shear stress‐induced initiation by increasing the screw rotation speed of twin‐screw extruder and through a compounded initiation by adding some initiator and increasing the screw rotation speed was investigated in this article. The results show that by increasing the screw rotation speed during melt‐extruding process, the scission of HDPE chain bonds can be caused to form macroradicals, the functionalization reaction of HDPE with MAH or with MAH, and MAS can be realized. The percentage of grafting and the melt flow rate of the functionalized products depend on the screw rotation speed and reaction temperature. The crosslinking reaction during melt extrusion can be suppressed by increasing the screw rotation speed and the reaction of HDPE with MAH can also be promoted by adding a second grafting monomer MAS. The high shear stress‐induced reaction products have a higher reactivity with the coupling agents coated on the surface of glass fibers and can obviously increase the mechanical properties of HDPE/GF composite. The SEM experimental results indicate that an oriented crystal transition layer exists between the interface of glass fiber and the matrix, the interfacial bonding strength is the determining factor of the formation of the oriented crystal layer. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

熔融法制备分散型黏度指数改进剂及其对增黏性能的影响

以具有较低门尼黏度的三元乙丙橡胶(EPDM)为原料,通过添加引发剂与提高双螺杆挤出机螺杆转速的应力诱导复合引发方法,研究EPDM与马来酸酐(MAH)的官能化反应,表征官能化产物胺化反应后作为分散型黏度指数改进剂的性能。结果表明:官能化反应主要是由引发剂引发和应力诱导引发共同作用所完成;所得分散型黏度指数改进剂的增稠能力都随着螺杆转速的增加而增大,当螺杆转速为800 r/min时,黏度指数达218,稠化能力最强为14.47 mm2/s。当胺化物加入量为0.24%时,黏度指数改进剂的黏度指数达223,稠化能力达到最大值14.74 mm2/s。     

Functionalization of ethylene–propylene–diene monomer rubber with maleic anhydride in the melt state through high‐shear stress‐induced initiation

The functionalization reactions of ethylene–propylene–diene monomer rubber (EPDM) with maleic anhydride (MAH) in melt state through high‐shear‐stress‐induced initiation by an increase in the screw rotation speed of the twin‐screw extruder and through compounded initiation by the addition of some initiator and an increase in the screw rotation speed were investigated. The results show that, with increasing screw rotation speed and reaction temperature, the percentage grafting and melt flow rate of the functionalized products (EPDM‐g‐MAH) were noticeably increased, and the viscosity‐average molecular weight decreased, which implied that the grafting reaction consisted of the chain scission and grafting reaction of the produced macroradicals with MAH. In the presence of a certain peroxide initiator, the crosslinking reaction during melt extrusion was suppressed by an increase in the screw rotation speed. The percentage grafting of EPDM‐g‐MAH amounted to 1.1%, its melt flow rate was between 0.3 and 4.0 g/10 min, and its gel content was less than 1.0%, depending on the screw rotation speed and reaction temperature. Impact testing and scanning electron microscopy showed that the functionalized product prepared through the high shear stress‐induced initiation had a higher blocking activity with the amide terminated of PA66 than that prepared through the peroxide initiation or through the compound initiation, and the impact strength of the PA66/EPDM blends, improved by the high‐shear‐stress‐induced product was noticeably higher than those of the peroxide‐initiated product or the compound‐initiated one. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

高剪切应力诱导引发马来酸酐官能化三元乙丙橡胶

在熔融挤出过程中,采用提高双螺杆挤出机螺杆转速所产生的高剪切应力诱导引发的方法及添加引发剂与提高螺杆转速的复合引发方法,研究了三元乙丙橡胶(EPDM)与马来酸酐(MAH)的官能化反应.结果表明,双螺杆挤出机的高螺杆转速所产生的高剪切应力作用可诱导EPDM的断链反应,引起官能化产物黏均相对分子质量的明显减小及接枝率与熔体流动速率的明显增大;在适量过氧化物类引发剂存在的条件下,此种高剪切应力作用可抑制EPDM官能化过程中的交联副反应,使产物的凝胶含量明显下降,接枝率及熔体流动速率明显增大;此种官能化反应过程易于控制,可制得接枝率0.80%～1.13%、熔体流动速率0.11～0.28 g/min及凝胶质量分数不大于1.0%的MAH官能化EPDM.     

聚烯烃弹性体与马来酸酐的熔融接枝

以双螺杆挤出机作为反应器，比较了聚烯烃弹性体（POE），线性低密度聚乙烯（LLDPE）与马来酸酐（MAH）的熔融接枝反应。尽这两种树脂具有相近的支化度，但由于POE树脂的大支链对大分子自由基之间的偶合反应具有抑制作用，所以，POE/MAH接枝体系的接枝率明显高于LLDPE／MAH接枝体系，而且接枝产物保持了较好的流动性；酸酐在POE树脂上的接枝率随过氧化物和接枝单体用量的增加而增大。接枝树脂可以明显提高PE与铝之间的粘接强度。     

Ultrasound initiated functionalization of SEBS with maleic anhydride

The functionalization of styrene‐b‐(ethylene‐co‐1‐butene)‐b‐styrene tri‐block copolymer with maleic anhydride (MAH) in melt state through ultrasound initiation was studied in this article. The effects of plasticizer content and types, MAH content, ultrasound power, and die temperature on grafting ratio of MAH were investigated by means of acid–base titration. Functionalized products were confirmed by new absorption bands in Fourier‐transform infrared spectroscopy. The experimental results showed that the ultrasound initiated products had lower complex viscosity (η^*), lower gel content as well as lower molecular weight than peroxide initiated products, indicating that the ultrasound could cause chain scission and suppress the crosslinking side reaction to gain functionalized products, which have less gel content and high grafting ratio. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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。     

Preparation and characterization of high melt strength polypropylene with long chain branched structure by the reactive extrusion process

The reactive extrusion of maleic anhydride grafted polypropylene (PP‐g‐MAH) with ethylenediamine (EDA) as coupling agent is carried out in a corotating twin‐screw extruder to produce long chain branched polypropylene (LCBPP). Part of PP‐g‐MAH is replaced by maleic anhydride grafted high‐density polyethylene (HDPE‐g‐MAH) or linear low‐density polyethylene (LLDPE‐g‐MAH) to obtain hybrid long chain branched (LCB) polyolefins. Compared with the PP‐g‐MAH, PE‐g‐MAH, and their blends, the LCB polyolefins exhibit excellent dynamic shear and transient extensional rheological characteristics such as increased dynamic modulus, higher low‐frequency complex viscosity, broader relaxation spectra, significantly enhanced melt strength and strain‐hardening behaviors. The LCB polyolefins also have higher tensile strength, tensile modulus, impact strength and lower elongation at break than their blends. Furthermore, supercritical carbon dioxide (scCO₂) is constructively introduced in the reactive extrusion process. In the presence of scCO₂, the motor current of the twin extruder is decreased and LCB polyolefins with lower melt flow rate (MFR), higher complex viscosity and increased tensile strength and modulus can be obtained. This indicates that the application of scCO₂ can reduce the viscosity of melt in extruder, enhance the diffusion of reactive species, and then facilitate the long chain branching reaction between anhydride group and primary amine group. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

热引发官能化HDPE、PP、EPDM及其增韧PA66研究

采用热引发熔融接技方法研究了不同反应条件下马来酸酐（MAH）接枝HDPE、接枝共聚PP及接枝EPDM弹性体的接枝反应。结果表明：本热引发接枝法可避免接枝过程中的交联副反应，制得具有较高接枝率（接枝率在0.3%以上），较好熔体流动性能，较少凝胶含量的马来酸酐接枝HDPE、接枝共聚PP及接枝EPDM。采用机械共混法对已官能化的聚烯烃弹性体和聚烯烃塑料分别和混合增韧PA66的情况进行了比较，结果显示：采用PA66／改性聚烯烃弹性体／改性聚烯烃塑料三元共混体系，可以在较少用量的改性橡胶条件下使PA66的缺口冲击强度达到原材料的10倍以上，并且材料弯曲模量损失减少。SEM对PA66／EPDM－g-MHA/PP-g-MAH三元共混体系脆韧转变的研究结果表明：体系分散相中的EPDM－g-MAH向PA66基体扩散、渗透或形成嵌段共聚物的部分是增韧PA66中的有效成分。     

应力诱导引发MAH官能化PE-LD及其对铝箔/PET复合薄膜层间剥离强度的影响

采用提高双螺杆挤出机螺杆转速的应力诱导引发方法和添加引发剂与提高螺杆转速的复合引发方法,研究了高剪切应力作用下马来酸酐(MAH)与低密度聚乙烯 (PE-LD)的官能化反应,并且考察了官能化产物PE-LD-g-MAH对铝萡/PET薄膜（Al/PET）热熔胶的T型黏合接头剥离强度的影响。结果表明,高剪切应力作用可直接引起大分子链的断链,形成大分子自由基,引发PE-LD的接枝反应;通过改变螺杆转速可有效抑制交联副反应,制得具有较高接枝率、较好熔体流动速率和较低凝胶含量的官能化产物,当螺杆转速为800 r/min时,产物的接枝率为0.71 %,熔体流动速率为0.87 g/10 min,凝胶含量0.40 %;高剪切应力诱导引发法所得官能化产物可明显提高Al/PET热熔胶T型黏合接头的剥离强度,当反应温度为310 ℃,螺杆转速为600 r/min,三元乙丙橡胶（EPDM）含量为80 %（质量分数,下同）时,可使Al/PET的T型黏合接头的剥离强度达3.87 N/mm。     

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。     

Effects of type of polymerization catalyst system on the degradation of polyethylenes in the melt state. Part 1: Unstabilized polyethylenes (including metallocene types)

Several polyethylene resins namely, high‐density polyethylene (HDPE) (Phillips metal oxide catalyst) and linear low‐density polyethylenes (LLDPE) (formed by using Ziegler‐Natta and metallocene catalyst technologies), were used in order to acquire insight into the effect of different polymerization catalyst systems on the production of degradation products during melt processing. Infrared spectroscopy, color measurement, hydroperoxide determination, and melt flow rate measurement were used to monitor the degradation as a function of the number of passes through a twin‐screw extruder. The metallocene PEs were shown to exhibit superior melt stability relative to Phillips HDPE. The latter showed high levels of hydroperoxide formation. The superior thermo‐oxidative stability of the metallocene PEs was attributed to low levels of metallic catalyst residues, together with low vinyl unsaturation content. In all of the PEs examined, the rate of crosslinking was greater than that of chain scission. IR spectroscopy indicated that crosslinking (most prevalent in the Phillips HDPE) proceeded via the addition of macroradicals to vinyl unsaturation. The Ziegler‐Natta LLDPE showed an intermediate tendency for crosslinking but notable formation of trans‐vinylidene and the most noticeable color development. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Melt functionalization of EVA copolymers with maleic anhydride

Ethylene vinyl acetate (EVA) copolymers with different amounts of vinyl acetate were melt‐functionalized with maleic anhydride. The effect of benzoyl peroxide, t‐butyl perbenzoate, and dicumyl peroxide (DCP) as free‐radical initiators on the functionalization performance was studied. The crosslinking reactions occur to a larger extent than in polyethylene, indicating that the vinyl acetate groups favor the formation of free radicals. From all the experiments performed in this study, the recommended initiation system to achieve the best values of the functionalization degree and the lower gel content involves the use of DCP in a concentration of about 0.3 wt % and a maleic anhydride concentration around 5.0 wt %. From FTIR and TGA analyses, it is suggested that the hydrogen abstraction in the EVA copolymers occurs both in the methyl group of the acetate moiety and in the tertiary C—H. The free radicals generated in the tertiary C—H react with maleic anhydride in a higher proportion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1799–1806, 1999     

High density polyethylene-g-maleic anhydride preparation in presence of electron donors

The reaction of molten HDPE with MAH at 215 and 250°C using di-t-amyl peroxide and t-butyl cumyl peroxide as catalysts yielded HDPE-g-MAH accompanied by crosslinked polymer. The formation of the latter, increased by the presence of MAH and insoluble in refluxing xylene, was prevented by the presence of electron donor additives, i.e., dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and tri(nonylphenyl) phosphite (TNPP). A charge containing 0.0625–0.125% catalyst, 5% MAH and 0.5% additive, all based on HDPE and added to the molten HDPE in four portions, resulted in gel-free polymer with an MAH content of 0.7–1.7%. HDPE-g-MAH with the least color was obtained with TNPP, followed by DMAC and DMSO. Notwithstanding the absence of gel in the HDPE-g-MAH prepared from HDPE with a melt flow of 17 g/10 min, the carboxylated HDPE had a melt flow of 0.0–1 g/10 min, indicative of an increase in the molecular weight of the product. This is attributed to a coupling reaction between MAH radicals appended to the HDPE backbone (HDPE–MAH·) and HDPE radicals formed as a result of hydrogen abstraction from HDPE by radicals from the catalyst and/or excited MAH.     

Synthesis and characterization of high‐density polypropylene‐grafted polyethylene via a macromolecular reaction and its rheological behavior

High‐density polyethylene grafted isotactic polypropylene (PP‐g‐HDPE) was prepared by the imidization reaction between maleic anhydride grafted polyethylene and amine‐grafted polypropylene in a xylene solution. The branch density was adjusted by changes in the molar ratio between maleic anhydride and primary amine groups. Dynamic rheology tests were conducted to compare the rheological properties of linear polyolefins and long‐chain‐branched polyolefins. The effects of the density of long‐chain branches on the rheological properties were also investigated. It was found that long‐chain‐branched hybrid polyolefins had a higher storage modulus at a low frequency, a higher zero shear viscosity, a reduced phase angle, enhanced shear sensitivities, and a longer relaxation time. As the branch density was increased, the characteristics of the long‐chain‐branched structure became profounder. The flow activation energy of PP‐g‐HDPE was lower than that of neat maleic anhydride grafted polypropylene (PP‐g‐MAH) because of the lower flow activation energy of maleic anhydride grafted high‐density polyethylene (HDPE‐g‐MAH). However, the flow activation energy of PP‐g‐HDPE was higher than that of PP‐g‐MAH/HDPE‐g‐MAH blends because of the presence of long‐chain branches. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

废旧PE-HD/OMMT纳米复合材料热氧老化性能和燃烧性能研究

以废旧高密度聚乙烯（PE-HD）和蒙脱土（MMT）为原料,采用熔融插层法制备纳米复合材料,考查制备工艺对该材料热氧老化性能和燃烧性能的影响。结果表明,PE-HD复合MMT或有机蒙脱土（OMMT）后,抗热氧老化性能显著降低,阻燃性能增强;十六烷基三甲基溴化铵（CTAB）、OMMT、马来酸酐（MAH）和过氧化二异丙苯（DCP）加入量分别增加时,PE-HD/OMMT纳米复合材料的抗热氧老化性能无显著变化,阻燃性能呈现先增强后降低或稳定的趋势;当CTAB加入量为1 %、OMMT加入量为3 %、MAH和DCP加入量为1.5 %时,PE-HD/OMMT纳米复合材料的极限氧指数达到19.4 %,阻燃性能最好。     

LLDPE溶液接枝马来酸酐的研究

研究了在二甲苯溶剂中，以过氧化二苯甲酰（ＢＰＯ）为引发剂，线性低密度聚乙烯（ＬＬＤＰＥ）接酸酐的反应，采用正交实验方法考察了引发剂用量，单体及ＰＥ浓度。反应温度及时间、阻止交联剂的加入量等因素对接枝反应的影响。结果表明，各因素对ＰＥ接枝率影响的大小次序是ＭＡＨ用量，反应温度、阻止交联剂用量、ＬＬＤＰＥ浓度和ＢＰＯ有用量，阻止交联剂的加入可以有铲地防止ＰＥ恶性循环 自由基的交联。     

Preparation of HDPE/SEBS‐g‐MAH and its effect on mechanical properties of HDPE/wood flour composites

In this article, high density polyethylene/styrene‐ethylene‐butylene‐styrene block copolymer blends (HDPE/SEBS) grafted by maleic anhydride (HDPE/SEBS‐g‐MAH), which is an effective compatibilizer for HDPE/wood flour composites was prepared by means of torque rheometer with different contents of maleic anhydride (MAH). The experimental results indicated that MAH indeed grafted on HDPE/SEBS by FTIR analysis and the torque increased with increasing the content of maleic anhydride and dicumyl peroxide (DCP). Styrene may increase the graft reaction rate of MAH and HDPE/SEBS. When HDPE/SEBS MAH was added to HDPE/wood flour composites, tensile strength and flexural strength of composites can reach 25.9 and 34.8 MPa in comparison of 16.5 and 23.8 MPa (without HDPE/SEBS‐g‐MAH), increasing by 157 and 146%, respectively. Due to incorporation of thermoplastic elastomer in HDPE/SEBS‐g‐MAH, the Notched Izod impact strength reached 5.08 kJ m^?2, increasing by 145% in comparison of system without compatibilizer. That HDPE/SEBS‐g‐MAH improved the compatibility was also conformed by dynamic mechanical measurement. Scanning electron micrographs provided evidence for strong adhesion between wood flour and HDPE matrix with addition of HDPE/SEBS‐g‐MAH. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007