低熔指PE粉拉伸流变加工特性与制品性能分析

利用拉伸流变挤出机研究了低熔指PE粉挤出造粒和直接挤出吹膜的特性。采用凝胶渗透色谱(GPC)、核磁共振、动态流变等方法,分析了低熔指PE粉经拉伸流变挤出造粒前后结构与性能的变化,并与双螺杆挤出机进行对比,了解了拉伸流变挤出技术在挤出能力、加工性能、制备原料性能等方面的优势。结果表明,转子直径为40 mm的拉伸流变挤出机最大挤出能力为67 kg/h,与直径相同的双螺杆相比,提高了190%;造粒后树脂的重均分子量均有下降,采用拉伸流变挤出造粒、螺杆造粒得到的树脂的重均分子量分别下降了7.8%、23.8%。利用拉伸流变挤出机对低熔指PE粉直接吹膜,成功制备2种不同型号的低熔指PE薄膜,其落镖冲击强度分别能达到240和137 g,综合性能较好。     

辐照改性聚丙烯拉伸流变行为及其挤出发泡的研究

通过在线形聚丙烯中加入双官能团丙烯酸酯类单体,经小剂量γ射线高能辐照,制备了高熔体强度聚丙烯,研究了其拉伸流变行为及其在挤出发泡方面的应用。Rheotens拉伸流变测试表明,辐照改性后由于形成了长支化分子结构,聚丙烯的熔体强度、拉伸黏度显著提高,具有明显的应变硬化特征。实验表明,ZnO可明显降低AC发泡剂分解温度,缓和分解放热;在辐照改性制备的高熔体强度聚丙烯中加入AC／ZnO复合发泡剂,可挤出发泡得到泡孔尺寸较为均一、分布均匀、具有闭孔结构的发泡材料。     

增感辐照改性聚丙烯及其表征

以两官能度丙烯酸酯单体为辐照敏化剂,在氮气保护下,通过60Co γ射线的引发作用将普通线性聚丙烯进行增感辐照改性。研究了辐照聚丙烯的熔体流动速率、熔体强度、分子量及其分布,结晶度以及结晶温度随辐照敏化剂含量的变化规律,探讨了增塑剂和抗氧剂对辐照体系的影响。结果表明:在普通聚丙烯中加入1.0%的两官能度辐照敏化剂,在氮气氛围中,在1kGy剂量,6kGy/h剂量率条件下辐照,可以显著提高辐照聚丙烯的熔体强度;GPC测试结果表明:辐照聚丙烯的重均分子量和Z均分子量在辐照敏化剂含量为1.0%时达到最大值,分子量分布最宽;DSC分析显示:聚丙烯增感辐照后结晶温度明显提高,但结晶度未有明显变化;增塑剂的加入改善了辐照聚丙烯的流动性;抗氧剂使辐照聚丙烯的熔体强度、分子量及其分布,以及结晶温度都明显提高。     

辐照改性制备长支链型高熔体强度聚丙烯流变性能(Ⅱ)拉伸流变

通过辐照法制备了长支链型高熔体强度聚丙烯(LCB-HMSPP)，采用Rheotens熔体拉伸流变仪研究了辐照改性PP的熔体强度和拉伸流变行为，讨论了敏化剂含量、辐照剂量、高分子量物质和温度对PP拉伸流变行为的影响。研究结果表明：PP的熔体强度、拉伸应力、拉伸黏度等拉伸流变物理量随敏化剂增加而显著增强，并随辐照剂量呈先上升后下降的趋势，辐照剂量为5kGy时，熔体强度和拉伸黏度到达最大。添加极少量高分子量物质(UHMWPE)也能有效提高PP的熔体强度。LCB-HMSPP的熔体强度活化能显著降低，熔体强度温度敏感性下降，可在较宽的温度范围内表现出较高的熔体强度。     

微波辐照对PP/纳米TiO2复合材料拉伸行为的影响

首先采用傅里叶红外光谱仪(FT-IR)表征微波辐照前后PP/纳米TiO2母粒的表面特征,然后经二次熔融挤出制备了微波辐照PP/纳米TiO2复合材料.通过力学性能测试、拉伸曲线分析和SEM照片观测,对微波辐照前后PP/纳米TiO,复合材料的拉伸过程和断裂机理进行了研究.结果表明:微波辐照后复合材料的冲击韧性、抗拉强度和弯曲模量基本保持,但断裂伸长率比辐照前的提高了100%,拉伸曲线的位移由18 mm变为36 mm;微波辐照还使复合材料由脆断变成韧断,主要是聚丙烯基体塑性的增加和界面相的增厚避免了团聚体的形成.     

均聚聚丙烯锂电池膜专用料性能研究

以国外进口和国产三种均聚聚丙烯树脂为原料,采用凝胶渗透色谱(GPC)、差示扫描量热仪(DSC)、扫描电镜(SEM)、电子万能试验机等测试手段考察了树脂专用料分子量及其分布对产品性能的影响。通过熔体挤出拉伸法以三种聚丙烯为原料制备锂电池微孔膜,并通过退火处理、冷热拉伸进一步考察了分子量及其分布对最终锂电池微孔膜结构的影响。结果表明:聚合物树脂中高分子量级分含量是影响预制膜中片晶取向度、冷热拉伸成孔分布和尺寸均匀度的重要因素。     

含少量高分子量组分的HDPE共混物在复合应力场中成型管材的性能研究

将少量相对高分子量的高密度聚乙烯(HDPE)加入到相对低分子量的通用级HDPE中,在复合应力场作用下挤出制成管材。通过力学性能测试、SEM、WAXD及DSC分析对制品的性能及结构进行了表征,结果表明:在剪切或拉伸应力场中,高分子量HDPE的大分子链会成为初级晶核,促进诱导体系生成大量倾斜排列的串晶和串晶互锁结构,明显改善了管材试样周轴两向的力学性能。     

紫外老化对聚甲基丙烯酸甲酯结构和性能的影响

通过人工加速老化试验,研究了聚甲基丙烯酸甲酯(PMMA)在不同紫外辐照条件下的性能变化规律。利用力学试验、凝胶渗透色谱(GPC)、傅里叶红外光谱(FTIR)等表征技术,分析了紫外老化对PMMA力学性能、分子结构、分子量及分子量分布的影响。结果表明,随着紫外老化的环境温度提高、老化时间延长,样品的拉伸强度、冲击强度均呈现下降趋势。样品在环境温度100℃条件下,老化280 min后,冲击强度下降最明显。老化后,红外光谱的羰基吸收带加宽,并且在1615 cm^-1处和1640 cm^-1处出现了包含不饱和键和羰基生色团的新吸收峰,样品的分子量微分分布宽度变宽,分子量移向低分子端的趋势明显,分子量多分散性增加。     

γ射线辐照交联改性超高相对分子质量聚乙烯的研究

采用单螺杆挤出机制备了超高相对分子质量聚乙烯(PE-UHMW)板材,并用不同剂量的γ射线对其进行辐照交联,分析不同辐照剂量和辐照后处理对其力学性能、耐热性能、摩擦磨损性能等的影响。结果表明,在一定的辐照剂量下,γ射线辐照交联可以提高PE-UHMW的凝胶率、熔点、结晶度、拉伸强度、表面硬度、热变形温度和耐磨性能;当辐照剂量为150kGy时,PE-UHMW的热变形温度提高了近40℃;但辐照交联降低了PE-UHMW的塑性,使材料的断裂伸长率降低;重新熔融后处理可以进一步提高材料的凝胶率,改善其塑性,但材料的熔点、结晶度、表面硬度、拉伸强度有所降低。     

超声振动在PS挤出发泡中的作用研究

研究了在ＰＳ挤出发泡中引入高强度超声振动对制品微观形貌和性能的影响。结果表明在ＰＳ挤出发泡的机头熔体中加入超声波可提高发泡率，降低发泡制品的密度，螺杆转速越低时更为明显，泡孔形貌由原椭园变为园形，从而补偿由密度降低引起的拉伸强度下降，在机头熔体中加入超声波能降低挤出压力，提高挤出产量，但不如超声振动加入到模具和熔体界面时明显，在螺杆转速较高时，总消耗功率比低转速时有所降低     

Ultrasonic improvement of weld line strength of injection‐molded polystyrene and polystyrene/polyethylene blend parts

The effect of melt temperature, ultrasonic oscillations, and induced ultrasonic oscillations modes on weld line strength of polystyrene (PS) and polystyrene/polyethylene (PS/HDPE) (90/10) blend was investigated. The results show that the increase of melt temperature is beneficial to the increase of weld line strength of PS and PS/HDPE blend. Compared with PS, the increase of melt temperature can greatly enhance the strength of PS/HDPE blends. For PS, the presence of ultrasonic oscillations can enhance the weld line strength of PS at different melt temperatures. But for PS/HDPE blends, the presence of ultrasonic oscillations can improve the weld line strength when the melt temperature is 230°C, but when the melt temperature is 195°C, the induced ultrasonic oscillations hardly enhance the weld line strength. Compared with Mode I (ultrasonic oscillations were induced into the mold at the whole process of injection molding), the induced ultrasonic oscillations as Mode II (ultrasonic oscillations were induced into the mold after injection mold filling) is more effective at increasing the weld line strength of PS and PS/HDPE blends. The mechanism for ultrasonic improvement of weld line strength was also studied. POLYM. ENG. SCI., 45:1666–1672, 2005. © 2005 Society of Plastics Engineers     

Studies on high density polyethylene (HDPE) functionalized by ultraviolet irradiation and its application

The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m^?2 and 45 W m^?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m^?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m^?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m^?1 to 30.2 MPa and 158 J m^?1, respectively. Copyright © 2003 Society of Chemical Industry     

Functionalization of polyolefins with maleic anhydride in melt state through ultrasonic initiation

The functionalization reaction of high-density polyethylene (HDPE), linearly low-density polyethylene (LLDPE), polypropylene (PP) and EPDM rubber with maleic anhydride (MAH) in melt state through ultrasonic initiation was studied. The effect of ultrasonic intensity on the percentage of grafting, viscosity-average molecular weight, melt flow rate and gel content of the functionalized products were investigated by means of chemical titration, Fourier-transform infra-red spectroscopy (FT-IR), intrinsic viscosity and melt flow rate, etc. The molecular structures of the functionalized products prepared via ultrasonic initiation and via peroxide initiation were characterized by ¹H NMR spectroscopy. The results show that the functionalization reaction of HDPE, LLDPE and EPDM with MAH can be realized by ultrasonic initiation. This reaction mainly consists of the chain scission under ultrasonic irradiation, the end chain reaction of the produced macroradicals with MAH, and the terminated reaction of the produced succinyl radicals with the macroradicals or H* radicals through recombination or dismutation. The functionalized product through ultrasonic initiation mainly consists of the products containing an anhydride ring attached to the chain terminus. And the products prepared through peroxide initiation mainly contain an anhydride ring grafted on the side chain.     

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.     

The comparison of the behaviors of polymer/clay nanocomposites based on high density polyethylene and polypropylene in exposure of electron‐irradiation

The effect of irradiation on thermal and mechanical properties of high density polyethylene (HDPE) and polypropylene (PP)/clay nanocomposites in the presence of polyethylene glycol (PEG) and polypropylene glycol (PPG) for enhancing the clay dispersion into the polymer matrices is considered. The morphology studies show that clay layers satisfactorily expand in the presence of compatibilizers. The irradiation improves the mechanical properties of HDPE nanocomposites at 500 kGy, but it decreases the tensile strength of PP nanocomposites. The addition of PEG markedly ameliorates the mechanical properties of HDPE nanocomposites at 500 kGy, while this improvement is not deduced for PP nanocomposites. The thermogravimetric analysis data show that the irradiation increases the thermal stability of HDPE nanocomposites at the clay content of 5 wt% with and without compatibilizer. The thermal stability of PP nanocomposites descends with the irradiation dose, and the presence of PPG into the PP matrix intensifies this reduction. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Effect of ultrasonic oscillations on the rheological behavior and morphology of Illite‐filled high‐density polyethylene composites

The effects of ultrasonic oscillations on the rheological and viscoelastic properties and morphology of high‐density polyethylene (HDPE)/Illite (70/30) composites were studied. The experimental results showed that the die pressure and apparent viscosity of the HDPE/Illite (70/30) composites were reduced greatly, and so the mass‐flow rate significantly increased in the presence of ultrasonic oscillations during the extrusion. Scanning electron microscopy and linear viscoelasticity tests showed that ultrasonic oscillations improved the dispersion of the Illite particles into the HDPE matrix. The aggregation of the Illite particles disappeared on the fractured surfaces of HDPE/Illite (70/30) composites extruded in the presence of ultrasonic oscillations, and this indicated that ultrasonic oscillations promoted the homogeneous dispersion of Illite particles into the HDPE matrix. Ultrasonic oscillations caused the permanent reduction of the dynamic viscosity and zero‐shear viscosity of HDPE/Illite (70/30) composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 379–384, 2005     

Dynamic rheological properties of high‐density polyethylene/polystyrene blends extruded in the presence of ultrasonic oscillations

The linear rheological properties of high‐density polyethylene (HDPE), polystyrene (PS), and HDPE/PS (80/20) blends were used to characterize their structural development during extrusion in the presence of ultrasonic oscillations. The master curves of the storage shear modulus (G′) and loss shear modulus (G″) at 200°C for HDPE, PS, and HDPE/PS (80/20) blends were constructed with time–temperature superposition, and their zero shear viscosity was determined from Cole–Cole plots of the out‐of‐phase viscous component of the dynamic complex viscosity (η″) versus the dynamic shear viscosity. The experimental results showed that ultrasonic oscillations during extrusion reduced G′ and G″ as well as the zero shear viscosity of HDPE and PS because of their mechanochemical degradation in the presence of ultrasonic oscillations; this was confirmed by molecular weight measurements. Ultrasonic oscillations increased the slopes of log G′ versus log G″ for HDPE and PS in the low‐frequency terminal zone because of the increase in their molecular weight distributions. The slopes of log G′ versus log G″ for HDPE/PS (80/20) blends and an emulsion model were used to characterize the ultrasonic enhancement of the compatibility of the blends. The results showed that ultrasonic oscillations could reduce the interfacial tension and enhance the compatibility of the blends, and this was consistent with our previous work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3153–3158, 2004     

Ultrasonic improvement of the compatibility and rheological behavior of high‐density polyethylene/polystyrene blends

The effects of ultrasonic oscillations on the rheological behavior, mechanical properties, and morphology of high‐density polyethylene (HDPE)/polystyrene (PS) blends were studied. The experimental results show that the die pressure and apparent viscosity of HDPE/PS blends are remarkably reduced in the presence of ultrasonic oscillations and that mechanical properties of the blends are improved. The particle size of the dispersed phase in HDPE/PS blends becomes smaller, its distribution becomes narrower, and the interfacial interaction of the blends becomes stronger if the blends are extruded in the presence of ultrasonic oscillations. Ultraviolet spectra and Soxhlet extraction results show the formation of a polyethylene‐PS copolymer during extrusion in the presence of ultrasonic oscillations, which improves the compatibility of HDPE/PS blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 23–32, 2002     

Ultrasonic characterization of phase morphology of high density polyethylene/polyamide 6 blend melts

The high density polyethylene (HDPE) and polyamide 6 (PA6) blend melts with a droplet‐matrix microstructure were investigated using ultrasonic diagnosis system. The blend composition, as well as the particle size of the dispersed PA6 phase controlled by adding various amounts of the reactive compatibilizer HDPE grafted with maleic anhydride (HDPE‐g‐MAH), was, respectively, correlated with the ultrasonic velocity and attenuation. The results showed that ultrasonic velocity was insensitive to the particle size but varied linearly with the blend composition. However, the decrease of ultrasonic attenuation with the increasing content of HDPE‐g‐MAH suggested that the attenuation depended greatly on the particle size. Further investigations revealed that there was a good linear relationship between the excess attenuation and the size of the dispersed phase. Our results present that ultrasonic technique may be served as a promising technique for exploring phase morphology of polymer blends during processing. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

SEM study of the morphologic change of high‐density polyethylene surface grafted with glycidyl methacrylate

Scanning electron microscopy (SEM) study of the morphologic change of high‐density polyethylene (HDPE) surface grafted with glycidyl methacrylate (GMA) was reported. Radiation‐induced grafting of GMA onto HDPE was carried out in acetone and dichloromethane solution, respectively. The effects of irradiation dose, atmosphere, and swelling time on grafting were investigated. Generally, the extent of grafting increased with irradiation dose, but for the grafting carried out in acetone solution, the extent of grafting initially increased with irradiation dose and then remained almost constant. The extent of grafting was higher in acetone solution than in dichloromethane solution at the same irradiation dose. The extent of grafting in nitrogen was higher than that in air. The successful grafting of GMA onto HDPE was confirmed by weighing and FTIR analysis. SEM investigations showed that the morphologies of the PE samples grafted in acetone solution were quite different to those grafted in dichloromethane. The grafting of GMA carried out in acetone was mainly on HDPE surface and that carried out in dichloromethane was mainly in the bulk of HDPE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007