熔融纺丝法研究聚乙烯熔体的拉伸流变性能

采用熔融纺丝法研究了低密度聚乙烯（PE-LD）、线形低密度聚乙烯（PE-LLD）和高密度聚乙烯（PE-HD）熔体的拉伸流变性能。结果表明,PE-LD、PE-LLD和PE-HD熔体的熔体强度都随温度的升高而下降;随着拉伸应变速率和温度的升高,PE-LD、PE-LLD和PE-HD熔体的拉伸黏度下降;随着挤出速率的提高,相同应变速率下,PE-LD、PE-LLD和PE-HD熔体的拉伸应力和拉伸黏度都有所降低。     

不同颜料浓度时添加高熔体流动速率PE-LLD的色母粒性能研究

以高熔体流动速率的线形低密度聚乙烯（PE-LLD）与低密度聚乙烯（PE-LD）混合作为载体,不添加任何分散剂制成不同颜料浓度的蓝色母粒。研究了该体系的加工流变性能、母粒的着色性能以及分散性能,并与以低相对分子质量聚乙烯蜡作为分散剂的PE-LD色母粒进行了对比。结果表明,当颜料浓度为30 %（质量分数,下同）时,以PE-LLD/PE-LD作为载体,不用添加任何分散剂,制品的力学性能和色彩性能都可达到使用要求;但当颜料浓度达到40 %及以上时,以PE-LLD/PE-LD为载体和添加聚乙烯蜡2种加工方法都不能得到合格的制品。     

高强度茂金属线型低密度聚乙烯HPR1018HA的开发与应用

开发了高强度茂金属线型低密度聚乙烯(mLLDPE)HPR1018HA,测试了HPR1018HA的基础物性、相对分子质量及其分布,并与用齐格勒-纳塔催化剂生产的线型低密度聚乙烯(LLDPE)、进口mLLDPE进行了对比。结果表明:mLLDPE的冲击破损质量均大于700 g,而LLDPE的冲击破损质量仅132 g;mLLDPE的相对分子质量分布小于2.30,LLDPE的相对分子质量分布大于3.03;HPR1018HA与进口mLLDPE的各项性能相当。HPR1018HA在重包装膜、三层共挤复合包装膜中的加工应用表明,HPR1018HA薄膜与进口mLLDPE薄膜的力学性能、光学性能等相当,满足用户需求。     

茂金属线形低密度聚乙烯／普通聚乙烯共混体系非等温结晶行为的研究

用DSC和X-射线衍射法研究了茂金属线形低密度聚乙烯(m-PE-LLD)与高密度聚乙烯(PE-HD)、低密度聚乙烯(PE-LD)、线形低密度聚乙烯(PE-LLD)共混时PE-HD、PE-LD、PE-LLD不同加入量对m-PE-LLD非等温结晶行为和结晶动力学的影响。研究结果表明：PE-HD与m-PE-LLD共混使样品结晶峰变窄，结晶度和结晶速率有所提高，说明两者有较好的相容性与共结晶行为；PE-LD的加入使共混物结晶峰变宽，说明PE-LD与m-PE-LLD共结晶行为较差，存在部分相分离，但在PE-LD含为20％时有最大结晶度，结晶速率有所提高；PE-LLD的加入对m-PE-LLD非等温结晶和动力学影响较小。X-射线衍射结果证明共混使球晶粒径减小。     

POE/mPE/PE-HD改性PE-LD热封薄膜性能研究

采用热塑性弹性体乙烯辛烯共聚物(POE)改善低密度聚乙烯(PE-LD)薄膜的热封性能和拉伸强度,使用茂金属线形低密度聚乙烯(mPE)提高PE薄膜的热封强度,使用高密度聚乙烯(PE-HD)对PE-LD改性,提高其拉伸强度。结果表明,与未改性的PE薄膜相比,在外层为PE-LD、中层为PE-LLD(7042)∶PE-HD=70∶30、内层PE-LLD(7050)∶PE-LD∶POE(9361)∶mPE(M4707EP)=10∶80∶5∶5时,其纵、横向拉伸强度和热封强度分别提高了2973、1721 MPa和1611 N/15 mm。     

mLLDPE与LDPE共混改善mLLDPE加工性能的研究

主要进行了茂金属线性低密度聚乙烯(mLLDPE)与低密度聚乙烯(LDPE)共混改善mLLDPE的加工性能的研究。通过实验验证了mLLDPE与LDPE共混可以降低mLLDPE的表观粘度,提高剪切敏感性;提高临界剪切速率,防止熔体破裂;增大熔体流动速率,改善流动性能;增大熔体强度,促进膜泡的稳定性,降低膜泡破裂的可能性。另外,还验证了通过迅速冷却膜泡可以提高熔体强度,从而提出了采用膜泡的内部冷却方式更适合mLLDPE的加工。     

mPE及mPE／LDPE共混物性能的研究

测试茂金属聚乙烯（ｍＰＥ）的基础性能，包括密度、熔体流动速率、熔流比、挥发份、熔点、结晶速率、结晶度、屈服强度、断裂强度、断裂伸长率、冲击强度等，并进行分析比较；使用单、双螺杆挤出机研究ｍＰＥ ３５０Ｄ６０及３５０Ｄ６０／ＬＤＰＥ共混物的挤出加工性能；使用吹膜机研究３５０Ｄ６０／ＬＤＰＥ共混物的吹膜性能，了解共混物中３５０Ｄ６０含量与力学性能与光学性能的关系，了解落镖冲击强度、雾度、透光率与薄膜厚     

茂金属聚乙烯与通用聚乙烯共混物熔体的流变行为研究

用茂金属线型低密度聚乙烯(mLLDPE)与通用聚乙烯(LDPE、LLDPE)进行共混,测定了共混物的熔体质量流动速率(MFR);研究了共混物熔体的熔体强度和剪切敏感性.结果发现:当质量分数超过20%的mLLDPE与高熔体质量流动速率(MFR)的通用聚乙烯共混时,或者质量分数小于40%的mLLDPE与低MFR的通用聚乙烯共混时,共混物熔体的流动性会小于单一共混组分,除了在与一种LDPE共混时mLLDPE加入质量分数为10%的一种共混物外,其他共混物的熔体强度都超过单个共混组分.mLLDPE/LLDPE共混物熔体的剪切敏感性高于LLDPE.     

改性回收PET在吹塑薄膜方面的应用

采用扩链剂苯乙烯-丙烯腈-甲基丙烯酸缩水甘油酯三元共聚物(SAG)对回收聚酯(r PET)瓶料进行熔融改性,并与甲基丙烯酸缩水甘油酯(GMA)接枝的高密度聚乙烯(HDPE)共混以提高其熔体强度,将改性后的r PET吹塑成薄膜制品。结果表明:rPET经双螺杆熔融挤出进行扩链改性后,分子链线性结构受到破坏,形成了具有球形结构的大分子树脂,其结晶度降低;扩链后的rPET与接枝HDPE相容性良好,共混后熔融温度降低至238.74℃,熔体流动速率由38.00 g/10min降至7.38 g/10min。制得的吹塑薄膜外观和性能均良好,拉伸强度达到44 MPa,直角撕裂强度达到188.96 k N/m。     

淀粉基生物可降解薄膜的制备及性能研究

将环氧氯丙烷(EDH)改性玉米淀粉与线形低密度聚乙烯(PE-LLD)、低密度聚乙烯(PE-LD)、马来酸酐接枝聚乙烯(PE-g-MAH)共混,以环氧大豆油作为增塑剂,加入少量三元乙丙橡胶(EPDM)增弹成分,并通过不同吹膜成型方法制备了厚度为0.012mm的可降解薄膜,采用红外光谱分析、扫描电子显微镜等测试手段对该薄膜的性能进行了研究。结果表明,当改性淀粉含量达到70%时,薄膜仍具有优良的力学性能;用旋转模头吹膜有助于提高降解薄膜的淀粉含量。     

Crystallization,structure, morphology,and properties of linear low-density polyethylene blends made with different comonomers

Linear low-density polyethylene (LLDPE) 7042, which has a butene comonomer, is widely used but has poor tear and dart strengths. For practical applications, small amounts of other materials can be blended with 7042 to effectively improve its properties. In this study, four blend resins and films (cast and compressed films) were prepared by blending 7042 with four LLDPEs (2045G, 9030, 23F, and 9085) in 8:2 ratios. The results indicated that after blending 2045G, 23F, or 9030 with 7042, the crystallization ability of the three blends was significantly suppressed and crystal size decreased. Moreover, the molecular chain can pass though more lamellar stacks in the blends, leading to an increased tie-chain concentration. Therefore, the tear and dart impact strength of the blend films improved. In contrast, the crystallization ability of the 7042/9085 blend was only slightly suppressed and did not significantly impact its properties. These findings contribute to our understanding of the relationship between material structures and properties, demonstrating that LLDPE blends can be used to improve the tear and dart strengths of 7042.     

不同类型聚乙烯光氧老化特性比较研究

利用热重分析法、热分解动力学Coats-Redfern方法和力学性能测试研究了不同类型聚乙烯[高密度聚乙烯(PE-HD)、线型低密度聚乙烯(PE-LLD)、低密度聚乙烯(PE-LD)]在氙灯光氧老化条件下的热稳定性、动力学参数和力学性能的变化规律。结果表明,随着老化时间的延长,PE-LD的热稳定性下降幅度最大,且主要集中于老化后期;老化初期PE-HD,PE-LLD和PE-LD的活化能均下降较快,表明此时三者均发生了较为严重的老化现象,分子链断裂较为强烈,而老化后期活化能下降幅度顺序为PE-LDPE-LLDPE-HD,表明这个期间PE-LD的老化最为强烈;PE-LD比PE-HD和PE-LLD的弯曲强度和冲击强度下降更为显著,且主要集中于老化后期,PE-LLD的力学性能下降幅度次于PE-HD。3种聚乙烯光氧老化容易顺序依次为PE-LDPE-LLDPE-HD。     

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。     

茂金属聚乙烯与普通聚乙烯共混研究

用一种双峰分布茂金属聚乙烯(mPE)与普通聚乙烯(LLDPE或LDPE)共混料吹塑薄膜，测定mPE对薄膜力学性能的影响。结果表明，在LLDPE(LDPE)中加入20％mPE制成共混料，其吹塑薄膜的拉伸强度和撕裂强度均提高20％，穿刺强度提高60％(100％)；另外发现，当在LLDPE(LDPE)中加入20％～80％mPE时，薄膜的穿刺强度和撕裂强度几乎没有变化。     

Processing-structure-property investigation of blown HDPE films containing both machine and transverse direction oriented lamellar stacks

A series of blown films were prepared using two high density polyethylene resins of differing molecular weight and molecular weight distribution, using a high stalk process. Both the resins were processed at three frost line heights (FLHs) and three draw down ratios to determine the effect of processing parameters and resin characteristics on final film morphology and mechanical properties. By changing the FLH and the time to initiate transverse direction (TD) expansion, the relative number of lamellae stacked both perpendicular and parallel to the machine direction (MD) could be controlled for a constant blow up ratio (BUR) of 4:1. It was determined that the proportion of lamellae stacked parallel to the MD increased with increasing FLH. This effect was found to be related to the relaxation behavior of the melt and bubble shape. Increasing the stress in the stalk region was observed to lead to a reduction in stalk diameter just prior to bubble expansion, resulting in a greater effective BUR. Film morphology was observed to strongly influence end mechanical properties. Elmendorf tear resistance was found to increase in the MD and decreased in the TD with increasing FLH. The dart impact strength of these films was characterized with the surprising result that for one of the two resins studied, the dart impact increased with decreasing film gauge.     

高熔体强度聚丙烯/低密度聚乙烯共混体系的挤出发泡行为研究

利用熔体流动速率测试仪和转矩流变仪对不同比例的高熔体强度聚丙烯(HMSPP)/低密度聚乙烯(PELD)共混体系的流变行为进行研究,并对共混体系的流变数据进行分析.随后采用超临界CO2作为发泡剂进行了HMSPP/PE-LD共混体系的挤出发泡研究,并通过真密度计和扫描电子显微镜表征了发泡材料的表观密度和泡体结构参数.结果表...     

Tear strength of ductile polyolefin films

A reinforced trouser tear test was developed to evaluate the tear resistance of thin ductile films. Tests with blown film of linear low‐density polyethylene blended with up to 30 wt% of a high melt strength polypropylene (hmsPP) demonstrated that the test differentiated among films based on composition and thickness. Increasing the amount of hmsPP in the film decreased the tear resistance. Also, thinner films were less tear‐resistant than thicker films. Stable crack growth occurred with transformation of a crack tip damage zone into a continuous yielded zone at the fractured edge. The tear energy was directly proportional to the width of the yielded zone. Correspondence between the energy to deform the material in the yielded zone and the measured tear energy demonstrated that yielding in the vicinity of the propagating crack provided the resistance to tearing in these films.