Heat sealability of laminated films with LLDPE and LDPE as the sealant materials in bar sealing application

The heat sealability of laminated films with linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) as the sealant materials was investigated. A laboratory heat sealer was used to study the response of laminated films to temperature, time, and pressure. Platen temperature was confirmed as primary factor in controlling heat‐seal strength. Dwell time must be sufficiently long to bring the interfacial temperature to a desired level. When the desired heat‐seal strength has been achieved, further increase of dwell time did not improved heat‐seal strength. Platen pressure had little effect above the level required to flatten the materials for good contact. Bar sealing process window for each sample were developed. The optimum combination of platen temperature and dwell time for each laminated film can be obtained in the respective process windows. Strength of heat‐seal and its failure modes are closely related. Plateau initiation temperature closely corresponds to the final melting point of sealant materials. Relatively higher platen temperature was required to seal laminated films with lower thermal conductance. Required dwell time corresponds closely to the heat flow rate of bar sealing process. Laminated films made from extrusion lamination process provided lower level of achievable heat seal strength when compared with the laminated films made from dry‐bond lamination process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3736–3745, 2007     

Rheology of LLDPE,LDPE and LLDPE/LDPE blends and its relevance to the film blowing process

The relevance of polymer melt rheology in film blowing process for linear low‐density polyethylene (LLDPE) and its blends with three different low‐density polyethylenes (LDPEs) has been discussed. The effect of different LDPE components as well as their concentration on shear and elongational viscosity has been investigated. A good correlation has been observed between the extensional rheological parameters of LDPEs measured by different experimental techniques. The molecular structure of parent polymers as well as blend composition play an important role in the rheology of these blends and consequently their performance in the film blowing process. © 2000 Society of Chemical Industry     

Melt strength and film bubble instability of LLDPE/LDPE blends

The relevance of measuring the melt strength of low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and their blends to their performance in terms of bubble stability in the film blowing process has been investigated. A good correlation between the melt strength values for two series of LLDPE/LDPE blends and the size of the operating window for stable film bubble formation has been established. Both the macromolecular structure of the parent polymers, and melt morphology play an important role in the performance of these blends in the film blowing process. © 1999 Society of Chemical Industry     

薄膜用LLDPE树脂QLLF30的加工应用

针对线型低密度聚乙烯(LLDPE)树脂DFDA7042制备的薄膜雾度较大,且该树脂不能制备厚度8μm以下地膜的不足,开发了LLDPE树脂QLLF30,对其进行了加工应用研究,并与同类产品进行了对比。研究表明:用QLLF30制备的薄膜具有较好的光学性能,同时可制备厚度6μm左右的地膜,性能满足相关标准使用要求。与同类产品相比,QLLF30加工性能良好,具有较低的剪切黏度、螺杆扭矩、加工电流和较高的临界剪切速率,在加工过程中可以降低能耗。     

冷凝态操作下LLDPE高强度棚膜专用树脂开发

在线型全密度聚乙烯装置上开发和生产了高强度棚膜专用树脂DFDA-9085,并对工业化产品进行了性能测试和结构表征。DFDA-9085在冷凝态操作模式下实现稳定生产以及熔体流动速率、密度等指标的精确控制,工业化产品的重均分子量为1．54×105,各项性能指标达到进口专用树脂水平。加工的薄膜制品力学性能和耐老化性能良好,尤其是纵、横向直角撕裂强度达到118．1,123．5 kN／m。     

HDPE/LLDPE/POE薄膜性能的研究

采用线型低密度聚乙烯（LLDPE）和热塑性弹性体乙烯-辛烯共聚物（POE）对高密度聚乙烯（HDPE）薄膜进行改性,研究了LLDPE和POE对共混体系薄膜力学性能、加工性能的影响,探讨了LLDPE增强HDPE的机理。结果表明,加入一定量LLDPE,使HDPE／LLDPE薄膜的拉伸强度较纯HDPE薄膜有所增加,而单位冲击破损质量则有所下降。当w（LLDPE）为15％时,HDPE／LLDPE薄膜的拉伸强度提高21．6％,薄膜的单位冲击破损质量降低23．0％。在HDPE／LLDPE/POE三元体系中,当w（POE）,w（LLDPE）分别为10％,15％时,薄膜的拉伸强度、单位冲击破损质量、断裂伸长率比纯HDPE薄膜分别提高2．3％,113％。36．0％,综合性能良好。     

降低LLDPE DFDA7042薄膜雾度的研究

考察了添加剂B、C、D在不同加入量时对线型密度聚乙烯DFDA7042薄膜雾度的影响，找出了主要影响因素，提出了新的工艺配方为：添加剂B0．040％，添加剂C0．100％，添加剂D0．250％，该新工艺配方降低了薄膜雾度，提高了透明性，同时不影响薄膜的其他性能。     

硅烷接枝交联HDPE、LLDPE及其共混物的结构研究

利用红外光谱、差示扫描量热法等方法研究了高密度聚乙烯(HDPE)、线性低密度聚乙烯(LLDPE)及其共混物的乙烯基三乙氧基硅烷(VTEOS)接枝及交联产物的分子结构、熔融行为。结果表明,VTEOS接枝交联PE能力为:LLDPE>HDPE/LLDPE共混物>HDPE;接枝和交联使HDPE、LLDPE及其共混物的结晶度和熔点降低,晶粒变得不均匀。     

Preparation and physical properties of LLDPE grafted with novel nonionic surfactants

Copolymers of linear low‐density polyethylene (LLDPE) grafted with two novel nonionic surfactants, acrylic glycerol monostearate ester (AGMS) and acrylic polyoxyethylenesorbitan monooleate ester (ATWEEN80), containing hydrophilic and hydrophobic groups and 1‐olefin double bond were prepared by using a plasticorder at 190°C. To evaluate the grafting degree, two different approaches based on ¹H‐NMR data were proposed, and FTIR calibration was showed to validate these methods. The rheological response of the molten polymers, determined under dynamic shear flow at small‐amplitude oscillations, indicated that crosslinking formation of the chains could be decreased with increasing the monomer concentration. Their thermal behavior was studied by DSC and polarization microscope (PLM): The crystallization temperature (T_C) of grafted LLDPE shifted to higher temperature compared with neat LLDPE because the grafted chains acted as nucleating agents. Water and glycerol were used to calculate the surface free energy of grafted LLDPE films. The results indicated that the novel polyoxyethylene surfactant ATWEEN80 could greatly improve the hydrophilicity of LLDPE and the surface free energy varied from 33 mN/m of neat LLDPE to 106 mN/m of the grafted LLDPE film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

LLDPE装置粉料输送系统安全性论证

对中国石油大庆石化分公司线性低密度聚乙烯装置粉末输送系统进行了安全性论证。通过模拟装置的试验和现场测试,考察了粉末输送了粉末输送管线、粉末储仓在正常生产过程和模拟装置试验过程中产生的静电量、测试分析了粉料仓中电场强度、电位、可燃气体含量,对粉料输送管道内的最大电场强度和料仓内混合物的最小点火能进行了计算,并对危险性进行了理论和实际分析,对危险部位提出了改进意见和建议。     

Development of nanofibrous morphology in LDPE/LLDPE/PP blends and its effect on mechanical properties of blend films

Nanofibrous morphology has been observed in ternary blends of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and isotactic polypropylene (PP) when these were melt‐extruded via slit die followed by hot stretching. The morphology was dependent on the concentration of the component polymers in ternary blend LDPE/LLDPE/PP. The films were characterized by wide angle X‐ray diffraction (XRD), scanning electron microscopy (SEM), and testing of mechanical properties. The XRD patterns reveal that the β phase of PP is obtained in the as‐stretched nanofibrillar composites, whose concentration decreases with the increase of LLDPE concentration. The presence of PP nanofibrils shows significant nucleation ability for crystallization of LDPE/LLDPE blend. The SEM observations of etched samples show an isotropic blend of LDPE and LLDPE reinforced with more or less randomly distributed and well‐defined nanofibrils of PP, which were generated in situ. The tensile modulus and strength of LDPE/LLDPE/PP blends were significantly enhanced in the machine direction than in the transverse direction with increasing LLDPE concentration. The ultimate elongation increased with increasing LLDPE concentration, and there was a critical LLDPE concentration above which it increased considerably. There was a dramatic increase in the falling dart impact strength for films obtained by blow extrusion of these blends. These impressive mechanical properties of extruded samples can be explained on the basis of the formation of PP nanofibrils with high aspect ratio (at least 10), which imparted reinforcement to the LDPE/LLDPE blend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of silicone oil and polymeric modifiers on the mechanical properties of highly filled LLDPE

The effects of coupling agents, silicone oil, and three types of polymeric modifiers on the mechanical properties of linear low density polyethylene (LLDPE) composites highly filled with aluminium hydroxide [Al(OH)₃] were studied. Polymeric modifiers that contain polar groups, such as silane‐grafted polyethylene (Si‐g‐PE) and acrylic‐acid‐grafted ethylene‐vinyl acetate copolymer (AA‐g‐EVA), improve the mechanical properties dramatically, while nonpolar modifiers improve them to some extent. When Al(OH)₃ was treated using a titanate coupling agent, the silicone oil increased the impact strength and elongation at break of the LLDPE/Al(OH)₃ composites. Introduction of a polymeric modifier containing polar groups destroys the beneficial effects of silicone oil on film mechanical properties, while the introduction of a nonpolar elastomeric polymeric modifier retains the high impact strength and elongation at break. SEM analyses provide the indirect evidence of the encapsulation of silicone oil around the filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 121–128, 2002     

不同氢氧化镁对LLDPE性能的影响

采用气泡液膜法制备了疏松型纳米氢氧化镁（LN-MH）,将其和不同氢氧化镁分别填充到线型低密度聚乙烯（LLDPE）中制得复合材料。通过常规力学性能测试、TG、极限氧指数（LOI）和锥形量热仪（CONE）研究了疏松型氢氧化镁（LN-MH）和普通氢氧化镁（C-MH）对LI。DPE性能的影响。结果表明：LN-MH／LLDPE复合材料的拉伸强度、弯曲强度和氧指数均比C-MH／LLDPE有显著的提高;与C-MH相比,LN-MH对LLDPE有更好的阻燃效果和成炭作用,但热稳定性稍差。     

氟弹性体加工助剂对LLDPE薄膜性能的影响

在线型低密度聚乙烯(LLDPE)树脂中添加一定量的氟弹性体加工助剂(PPA)进行造粒、吹膜,考察薄膜的力学性能和光学性能等。结果发现:添加少量PPA后,薄膜的光学性能得到改善,雾度由不添加PPA时的14.0%降低至11.3%,加工能耗也有所降低,但是力学性能受到影响,薄膜的拉伸屈服强度(纵向/横向)由13.4/11.6 MPa降至12.5/10.7 MPa,拉伸断裂强度(纵向/横向)由45.1/40.0 MPa降至40.0/37.6 MPa,落镖冲击破损质量由75.0 g降至59.5 g。     

LLDPE装置负荷波动对反应系统的影响及措施

针对气相法线型低密度聚乙烯(LLDPE)装置的生产特点,分析指出生产负荷波动的主要原因有:催化剂、原料组分、反应温度控制参数以及与反应相关的其他系统设备故障的影响。并提出相应措施:控制催化剂活性、控制催化剂的加入量、优化反应温度的控制参数。从而确保了气相法LLDPE装置的平稳运行。     

OMMT和EG/MH协同阻燃LLDPE的研究

采用氢氧化镁(MH)、膨胀石墨(EG)和有机蒙脱土(OMMT)为阻燃剂制备了无卤阻燃线性低密度聚乙烯(LLDPE),研究了OMMT对LLDPE/EG/MH阻燃性能和力学性能的影响。结果表明:少量OMMT的加入,可以有效改善LLDPE/EG/MH的力学性能、阻燃性能和热稳定性。当OMMT质量分数为3.0%时,LLDPE/EG/MH/OMMT的拉伸强度和冲击强度分别为1.4 MPa和26.5 kJ/m~2;极限氧指数为35.0%,符合UL-94 V-0级;其热释放速率峰值、平均热释放速度、生烟速率和总生烟量比LLDPE/EG/MH的低。     

A comprehensive investigation of the origins of surface roughness and haze in polyethylene blown films

In an earlier publication we showed that the optical haze properties of blown and cast polyethylene (PE) films were adversely affected (i.e., haze increased) as a result of enhanced surface roughness caused by the formation of distinct optically anisotropic “spherulitic‐like” superstructures. In this report we have found that for a very wide variety of PE blown films, the total haze percent exhibited a complex parabolic relationship with the logarithm of the recoverable shear strain parameter, γ_∞. At low values of γ_∞, superstructures were developed (as discussed in our previous report) that increased surface roughness and hence total haze. As γ_∞ increased, such superstructures were either significantly diminished in size or altogether absent, giving rise instead to an oriented, row‐nucleated, stacked lamella texture that decreased surface roughness and hence total haze. However, at even higher γ_∞ values, representing highly melt elastic behavior, fine‐scale surface roughness due to high melt elastic instabilities was induced, thereby increasing surface roughness and consequently total haze as well. It was demonstrated in this work that two PE resins could exhibit the same level of total haze as a consequence of two completely different mechanisms or origins. Furthermore, we believe that this is the first time that both very low and very high melt elasticity have been shown as primary causative factors in yielding high haze in PE blown films, albeit for fundamentally very different reasons. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2396–2411, 2002     

光屏蔽剂与其填充LLDPE耐光老化性能的关系

研究了光屏蔽剂TiO2和ZnO填充线性低密度聚乙烯(LLDPE)体系光老化性能与光反射性能之间的关系。研究发现,光反射性能较好的TiO2与较差的ZnO分别加入LLDPE中后,光反射性良好的TiO2有促进LLDPE老化的现象。通过光在填充材料内部实际通量分析,我们认为这种现象是由于TiO2与ZnO不同程度的光内反射致使紫外光在聚合物中实际通量和光降解作用有差异的缘故。紫外光在TiO2/PE复合材料中的内反射剧烈,实际通量大,光老化显著,而ZnO对紫外光反射作用较弱,紫外光在ZnO/PE复合材料中的实际通量小,光老化程度小。     

The effect of heat sealing temperature on the properties of OPP/CPP heat seal. I. Mechanical properties

The effect of heat sealing temperature on the mechanical properties and morphology of OPP/CPP laminate films was investigated. The laminated films were placed in an impulse type heat sealing machine with both CPP sides facing each other. The temperatures investigated ranged from 100 to 250°C. T‐peel and tensile tests in combination with SEM were used to characterize the heat seals. A minimum seal initiation temperature of 120°C was identified for OPP/CPP laminate heat sealing. Peel strength increased sharply from zero at 110°C to maximum at 120°C, after which a gradual decrease was observed. Tensile strength initially increased until 120°C, after which it gradually decreased until 170°C and assumed a constant value beyond that. The initial rise has been associated to cold crystallization, while the reduction between 120°C and 170°C was due to relaxation in molecular orientation. Beyond 170°C, all the orientation in the laminate has been lost so orientation effects are nullified. Morphological studies with SEM revealed that seals were partially formed at lower temperatures, while the laminates were totally fused together at high temperatures, with intermediate temperatures showing properties that lie in between. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 753–760, 2005