正交设计用于LDPE/LLDPE/β沸石复合膜的热封性能优化

采用正交设计方法研究了β沸石填充低密度聚乙烯(LDPE)/线型低密度聚乙烯(LLDPE)复合膜的热封性能,详细探讨了β沸石用量、热封温度、热封时间和热封压力等条件对复合膜热封强度的影响情况。结果显示,β沸石用量对β沸石填充LDPE/LLDPE复合膜热封强度的影响最大。β沸石的添加改变了复合膜的配方组成,对薄膜热封强度的影响程度明显超过了热封工艺条件的影响。在热封温度、热封时间和热封压力三因素中,热封时间对复合薄膜的热封性能影响非常显著,远高于热封温度和热封压力的影响程度;热封温度和热封压力对复合膜热封强度的影响不太显著。     

中国专利

正一种用于果蔬包装的高低温防雾透气聚乙烯热封膜及其制备方法本发明公开了一种果蔬包装用高低温防雾透气聚乙烯热封膜,自上而下包括面层、芯层和热封层,三层共挤结构为:低密度聚乙烯(LDPE)+线型低密度聚乙烯(LLDPE)/LDPE+LLDPE+高低温复配防雾剂/LDPE+LLDPE+丙烯基弹性体+高低温复配防雾剂+超细硅藻土。通过在热封层和芯层中添加高低温复配防雾剂,使薄膜同时具有高低温防雾性能;在热封层中添加的超细硅藻土具有吸附功能,可以延缓防雾剂的析出,延长薄膜的防     

茂金属线型低密度聚乙烯的结构与性能

利用傅里叶变换红外光谱、凝胶渗透色谱、差式扫描量热法和力学性能测量等手段表征了茂金属线型低密度聚乙烯(mLLDPE)和传统线型低密度聚乙烯(LLDPE)的结构及性能,用热分级法表征了LLDPE的片晶厚度多散性,测试了mLDPE薄膜的相关性能。结果发现,mLLDPE的片晶厚度分布指数为1.1347,小于传统LLDPE,表明其具有更好的支化均匀性,但其相对分子质量分布窄；mLLDPE薄膜具有较高的落镖冲击强度、撕裂强度、热封强度和突出的光学性能。     

中国合成树脂工业分析（五）

(1)聚乙烯类 聚乙烯是目前薄膜生产的主要材料。我国低密度聚乙烯和线型低密度聚乙烯是薄膜生产的主要材料,用于薄膜生产的产量分别占其总产量的68.82％和68.51％。目前低密度聚乙烯生产薄膜一般采用挤出吹塑工艺,产品透明性好、柔韧、防水、阻气、易于热封及粘合、耐腐蚀且无毒无味,但存在阻氧性较差、不耐油脂和软化点低等缺点。一般厚度在0.02～0.1mm的薄膜用于仪器袋及日用品包装袋,0.2～0.3mm厚的薄膜适用于重物品包装。     

浅析线型低密度聚乙烯(LLDPE)树脂及工艺技术

文章以线型低密度聚乙烯树脂为分析对象,阐述其分子结构、应用分类、聚合机理等基础知识。通过比较不同专利商的线型低密度聚乙烯工艺技术和工艺特点,并结合多年来的生产经验及新建线型低密度聚乙烯装置的选型经历,提出关于线型低密度聚乙烯树脂应用及工艺技术选型的想法,期望可以为线型低密度聚乙烯工艺技术的选型和产品方案的选择提供指导和借鉴。     

聚乙烯流延薄膜性能的影响因素分析

介绍了流延工艺及其所用聚烯烃材料的种类。以低密度聚乙烯(LDPE)、线型低密度聚乙烯(LLDPE)为基料,制备了不同配方的聚乙烯流延薄膜并对比了其性能,研究了不同流延工艺条件对流延薄膜性能的影响。结果表明:LLDPE含量的增加能够提高薄膜力学性能,而LDPE能改善薄膜的光学性能;提高模头温度可以使薄膜横向拉伸断裂应力增加,纵向性能相反,薄膜光学性能提高,热封温度降低;增加牵伸比,薄膜光学性能降低;提高流延辊温度,流延薄膜横向拉伸断裂应力下降,纵向拉伸断裂应力增加,光学性能下降,热封温度提高。     

未来的挤出:线型和多层

现在,线型低密度聚乙烯的挤出都是由一些机器临时代替的。一些挤出机在线型低密度聚乙烯混合率达30%时还可以勉强应付,但当线型低密度聚乙烯单独使用时也就无能为力了。因此,挤出机的螺杆必须进行改进,使之能适应线型低密度聚乙烯的挤     

利用高密度聚乙烯装置生产线型低密度聚乙烯的相关研究

随着我国经济实力的飞速发展,对线型低密度聚乙烯的需求也有了很大的提升,相关部门必须对高密度聚乙烯装置生产线型低密度聚乙烯工艺给予足够的重视,并且加大对催化剂的研究力度。因此,主要对高密度聚乙烯装置生产线型低密度聚乙烯工艺进行了简要分析,阐述了相关催化系统,并且对生产工艺装置与主要生产流程进行了研究分析。     

聚乙烯泡沫塑料的研制

将线型低密度聚乙烯和低密度聚乙烯结合后，选用化学交联法生产闭孔软质泡沫塑料。     

聚乙烯泡沫塑料的研制

将线型低密度聚乙烯和低密度聚乙烯结合后，选用化学交联法生产闭孔软质泡沫塑料。     

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。     

Influence of branching characteristics on thermal and mechanical properties of Ziegler–Natta and metallocene hexene linear low‐density polyethylene blends with low‐density polyethylene

The effect of the branch content (BC) and composition distribution (CD) of linear low‐density polyethylene (LLDPE) on the thermal and mechanical properties of its blends with LDPE were studied. All blends and pure resins were conditioned in a Haake PolyDrive blender at 190°C and in the presence of adequate amounts of antioxidant. Two metallocene LLDPEs (m‐LLDPE) and one Ziegler–Natta (ZN) hexene LLDPE were melt blended with the same LDPE. The effect of the BC was investigated by blending two hexene m‐LLDPEs of similar weight‐average molecular weights and molecular weight distributions but different BCs with the same LDPE. The effect of the CD was studied by using a ZN and an m‐LLDPE with similar weight‐average molecular weights, BCs, and comonomer type. Low‐BC m‐LLDPE blends showed separate crystallization whereas cocrystallization was observed in the high‐BC m‐LLDPE‐rich blends. However, ZN‐LLDPE/LDPE blends showed separate crystallization together with a third population of cocrystals. The influence of the crystallization behavior was reflected in the mechanical properties. The BC influenced the modulus, ultimate tensile strength, and toughness. The addition of a small amount of LDPE to a low‐BC m‐LLDPE resulted in a major improvement in the toughness, whereas the results for the high‐BC pair followed the additivity rule. ZN‐LLDPE blends with LDPE blends were found to be more compatible and exhibited superior mechanical properties compared to m‐LLDPE counterparts with the same weight‐average molecular weight and BC. All mechanical properties of ZN‐LLDPE blends follow the linear rule of mixtures. However, the CD had a stronger influence on the mechanical properties in comparison to the BC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2488–2498, 2005     

Rheological study of the influence of branch content on the miscibility of octene m‐LLDPE and ZN‐LLDPE in LDPE

The influences of branch content on the miscibility of octene LLDPE made by metal‐locene catalyst (m‐LLDPE) and by Ziegler‐Natta LLDPE (ZN‐LLDPE) in LDPE were investigated with rheological methods. Dynamic and steady shear measurements were carried out in a Rheometrics Mechanical Spectrometer 800. Here, m‐LLDPEs were used to isolate interaction of molecular parameters. Blends of octene m‐LLDPE and ZN‐LLDPE with LDPE were mixed at 190°C in the presence of an adequate amount of antioxidant. The miscibilities of blends were revealed by the dependence of their measured η_o, η′ and G′ on blend composition as well as on agreement with predictions of different emulsion models. Blends of m‐LLDPE with LDPE were found to be almost miscible in the LLDPE branching range 10–30 branches/1000 C. However, immiscibility was found to develop at lower LLDPE branch contents. For ZN‐LLDPE/LDPE systems, branch content plays a significant role especially at low branch contents. The comparison of m‐LLDPE and ZN‐LLDPE systems suggest the strong influence of branch distribution (uniform and random, respectively). Palierne, Bousmina, and Scholz models fitted the loss and storage moduli data well with a value of α/R in the range 10³?10⁴ N/m². Polym. Eng. Sci. 44:660–672, 2004. © 2004 Society of Plastics Engineers.     

气相法mPE的性能剖析

茂金属聚乙烯（mPE)具有优越的力学性能和光学性能，这与茂金属催化剂的催化性能及其聚合物特殊的链结构形式密切相关。对国内开发的mPE进行了结构表征，结果表明：mPE薄膜的力学性能和光学性能明显优于线型低密度聚乙烯产品，其耐穿刺性能明显好于其他聚乙烯产品。     

Co‐crystallization in ternary polyethylene blends: tie crystal formation and mechanical properties improvement

Understanding the co‐crystallization behavior of ternary polyethylene (PE) blends is a challenging task. Herein, in addition to co‐crystallization behavior, the rheological and mechanical properties of melt compounded high density polyethylene (HDPE)/low density polyethylene (LDPE)/Zeigler ? Natta linear low density polyethylene (ZN‐LLDPE) blends have been studied in detail. The HDPE content of the blends was kept constant at 40 wt% and the LDPE/ZN‐LLDPE ratio was varied from 0.5 to 2. Rheological measurements confirmed the melt miscibility of the entire blends. Study of the crystalline structure of the blends using DSC, wide angle X‐ray scattering, small angle X‐ray scattering and field emission SEM techniques revealed the formation of two distinct co‐crystals in the blends. Fine LDPE/ZN‐LLDPE co‐crystals, named tie crystals, dispersed within the amorphous gallery between the coarse HDPE/ZN‐LLDPE co‐crystals were characterized for the first time in this study. It is shown that the tie crystals strengthen the amorphous gallery and play a major role in the mechanical performance of the blend.© 2016 Society of Chemical Industry     

Implications of melt compatibility/incompatibility on thermal and mechanical properties of metallocene and Ziegler–Natta linear low density polyethylene (LLDPE) blends with high density polyethylene (HDPE): influence of composition distribution and branch content of LLDPE

In this paper, the implications of melt compatibility on thermal and solid‐state properties of linear low density polyethylene/high density polyethylene (LLDPE/HDPE) blends were assessed with respect to the effect of composition distribution (CD) and branch content (BC). The effect of CD was studied by melt blending a metallocene (m‐LLDPE) and a Ziegler‐Natta (ZN) LLDPE with the same HDPE at 190 °C. Similarly, the effect of BC was examined. In both cases, resins were paired to study one molecular variable at a time. Thermal and solid‐state properties were measured in a differential scanning calorimeter and in an Instron mechanical testing instrument, respectively. The low‐BC m‐LLDPE (BC = 14.5 CH₃/1000 C) blends with HDPE were compatible at all compositions: rheological, thermal and some mechanical properties followed additivity rules. For incompatible high‐BC (42.0 CH₃/1000 C) m‐LLDPE‐rich blends, elongation at break and work of rupture showed synergistic effects, while modulus was lower than predictions of linear additivity. The CD of LLDPE showed no significant effect on thermal properties, elongation at break or work of rupture; however, it resulted in low moduli for ZN‐LLDPE blends with HDPE. For miscible blends, no effect for BC or CD of LLDPE was observed. The BC of LLDPE has, in general, a stronger influence on melt and solid‐state properties of blends than the CD. Copyright © 2004 Society of Chemical Industry     

CPP热封薄膜低温热封层性能研究

筛选不同聚丙烯低温热封材料与适量茂金属聚乙烯（mPE）、滑爽剂共混作为热封层,通过3层共挤流延法研制备了流延聚丙烯（CPP）低温热封薄膜,探讨了聚丙烯低温热封材料、热封温度、薄膜厚度、冷却辊温度等对薄膜热封性能的影响。结果表明,热封层中采用40份TF400、60份SFC-750M作为热封层,薄膜厚度控制为30 μm,冷却辊温度为22.6 ℃条件下,制备薄膜的各项性能均达到指标要求,其中热封强度可达16.44 N/15 mm,初始热封温度可降至105 ℃。     

Customizing the comonomer incorporation distribution in Ziegler–Natta-based LLDPE: Harnessing the influences of the titanation temperature during catalyst synthesis and of polymerization process parameters

The microstructure of linear low-density polyethylene (LLDPE) is strongly influenced by short-chain branches (SCBs) incorporated into the polymer backbone. Varying the number, distribution, and length of SCBs allows the properties of the resulting polymer to be tailored to meet specific requirements. Using Ziegler–Natta (ZN) catalysts for synthesis has disadvantages in terms of the comonomer incorporation distribution (CID) compared to, for instance, metallocene and post–metallocene catalysts. Nevertheless, ZN catalysts continue to be widely used, as many of the new generations of catalysts are more difficult to handle and cannot match the cheap cost of ZN catalysts. To improve this aspect of ZN catalysts, we investigated the influence of catalyst titanation temperature and polymerization process parameters on the CID. Our results show that it is possible to manipulate the process parameters of the present ZN catalyst system to yield a desired comonomer amount and CID in the polymer. Varying the titanation temperature clearly influenced the titanium content of the catalyst. Molecular-weight distribution analysis and deconvolution results indicate that changes in the amounts of comonomer incorporated and in the CID are directly related to the catalyst's active site that produces the lowest-molecular-weight fraction.     

Distributions of Crystal Size from DSC Melting Traces for Polyethylenes

Melting curves, obtained by differential scanning calorimetry, are used to estimate crystal size distributions. The proposed theoretical analysis is applied to different types of polyethylene, including high‐density polyethylene (HDPE), metallocene catalyzed linear low‐density polyethylenes (m‐LLDPE), blends of m‐LLDPEs, and Ziegler‐Natta catalyzed LLDPEs (ZN‐LLDPE). Theoretical predictions are in agreement with experimental results. A generalized melting temperature equation successfully predicts the melting temperatures of all the LLDPEs, although it was initially proposed for homogeneous copolymers with excluded comonomers. A new definition of the heat of fusion for pure crystals is proposed. This heat of fusion can be calculated from the average crystal size or the crystal size number distribution.     

PTT/mPE共混物的制备和性能研究

研究了聚对苯二甲酸丙二酯(PTT)/茂金属聚乙烯(mPE)共混体系的流变性能、结晶熔融行为、力学性能以及增容剂对共混物相形态的影响。结果表明：PTT/mPE共混物熔体为假塑性流体,熔体表观黏度随PTT含量的增加而迅速降低,PTT含量高于40％时共混物表观黏度迅速下降,PTT含量越多对温度变化的敏感性越强。PTT和mPE可分别结晶,但PTT组分的结晶峰温度Tpc和结晶熔融峰温度Tm均比纯PTT的明显提高,而mPE组分的Tpc和Tm与纯mPE的相近,mPE可以促进PTT熔体结晶,但已经形成的PTT晶体不影响mPE的结晶,mPE的结晶行为主要发生在mPE微相区内。增容剂马来酸酐接枝乙丙橡胶提高了PTT与mPE间的相容性,共混物的冲击强度随着增容剂的增加而提高,mPE和增容剂共同发挥了增韧作用。