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。     

马来酸酐熔融接枝LDPE的性能

采用熔融接枝法制备了低密度聚乙烯(LDPE)与马来酸酐(MAH)接枝物,通过调整反应物的用量及反应条件控制接枝率。随着MAH及引发剂用量的增加,接枝率呈先增大后降低的趋势。低剪切速率时,接枝物的最大初始剪切黏度达4750 Pa·s,远高于纯LDPE;高剪切速率时,接枝物的剪切黏度与纯LDPE趋于相同,约500 Pa·s。接枝物的拉伸强度在8 MPa左右,同纯LDPE接近,断裂伸长率略有下降。     

不同聚乳酸切片的流变性能比较及其对熔融纺丝性能的影响研究

利用毛细管流变仪对四种不同聚乳酸切片的流变行为进行了对比分析,并探讨了流变性能差异对熔融纺丝性能的影响。结果表明:四种聚乳酸熔体均呈现剪切变稀现象,具有非牛顿流体的流动特征;随着温度升高,聚乳酸熔体的非牛顿指数n增大;四种聚乳酸熔体的粘流活化能E_η较小,粘度随温度的变化小,有利于纺丝成型;四种聚乳酸熔体的结构粘度指数△η介于0.8~1.4,可纺性和稳定性较好。     

LDPE熔融接枝丙烯酸的研究

本文选择丙烯酸作为接枝单体与过氧化二异丙苯、低密度聚乙烯混合，在单螺杆挤出机中进行熔融接枝反应。实验研究了挤出条件、ＤＣＰ用量以及丙烯酸单体用量对熔融接枝的影响。     

超细纤维用LDPE 1I60A的流变和加工应用性能

研究了低密度聚乙烯(LDPE)1I60A的流变性能,聚酰胺(PA)6/LDPE共混纤维的开纤剥离性能及其剥离前后形貌的变化。结果表明:LDPE 1I60A熔体黏度低,PA 6/LDPE熔体黏度比大,有利于提高PA 6/LDPE中PA 6的含量;LDPE 1I60A与PA 6共混后加工性能优良,岛相分布均匀,LDPE 1I60A更易从PA 6/LDPE共混纤维中被溶解抽出,有利于得到PA 6含量较高的超细纤维。     

mPE/LDPE交联物的流变性能研究

采用动态黏弹仪研究了不同配比的茂金属聚乙烯(mPE)/低密度聚乙烯(LDPE)交联物流变性能,发现因为mPE/LDPE二者之间可能存在的物理交联结构和交联物的网络结构,其微观结构具有更强的多分散性。     

聚乙烯树脂熔体拉伸流变性能研究

选取了3种不同分子链结构的聚乙烯树脂,采用SER(sentmanat extensional rheometer)夹具旋转流变仪、熔体拉伸流变仪分别研究了其熔体瞬态拉伸黏度、熔体拉伸强度和拉伸黏度等流变性能.结果表明,随Hencky形变的增大,高密度聚乙烯(PE-HD)100N的熔体瞬态拉伸黏度的增长趋势逐渐放缓;低密...     

熔融纺丝法制备UHMWPE/MMT复合纤维的研究

以超高相对分子质量聚乙烯/蒙脱土(UHMWPE/MMT)纳米复合材料为原料,采用熔融纺丝法,在自行设计制造的实验纺丝机上制备出纤维,利用DSC、XRD、SEM等手段对其结构进行了表征,并对其性能进行了测试。拉伸条件试验表明,水浴温度85℃、拉伸倍率14倍,是纤维最佳拉伸温度与倍率;纤维在拉伸过程中存在一个最佳的甬道停留时间。微观结构分析表明,拉伸后得到的纤维熔点、取向度都得到了提高,并在一定条件下出现了正交晶形到六方晶形的转变。     

LDPE熔融接枝的研究

本文介绍了马来酸酐（MAH）、丙烯酸（AA）、乙烯在三乙氧硅烷（A151）与LDPE的挤出熔融接枝工艺以及枝物与氢氧化铝（ATH）配合后填充体系的力学性能。研究了挤出温度、DCP用量和MAH用量对接枝物分子结构的影响，得出温度在210－230℃的范围内挤出物的接枝及MFI变化不大，当温度升到250℃后接枝率及MFI均不下降，DCP用量达到0．10phr以后，接枝率渐趋平衡而物料的MFI却迅速下降，表明有严重的交联反应；随MAH用量的增加，接枝率相应增加，当用量达0．5phr后接枝率基本稳定，不随MAH用量增加而继续提高。由接枝物－ATM填充体系的拉伸强度（σ拉）表明，虽然三种不同单体接枝的LDPE自身的σ拉与纯LDPE基本相同，但填充体系的σ拉均明显高于未接枝的。PE与ATH以1：1双例配合时，测得PE接枝MAH和枝A151的σ拉分别为15．3MPa和14.9MPa，比相同配比下未接枝的7．4MPa提高一倍以上。     

PLA与PP,LDPE流变性能比较

采用毛细管流变仪考察了温度、剪切速率、预热时间对聚乳酸(PLA)、聚丙烯(PP)、低密度聚乙烯(LDPE)流变性能的影响。结果表明:PLA属切力变稀流体,在210℃时的非牛顿指数为0.68,而该温度下PP的非牛顿指数为0.56,LDPE为0.49;在剪切速率为100~2000s-1时,PLA的黏流活化能为61.51~141.52kJ/mol,PP为14.6~31.92kJ/mol,LDPE为13.89~36.47kJ/mol;在低剪切速率时,增加预热时间不仅使PLA的黏度明显下降,而且使其非牛顿指数和黏流活化能增加,当预热时间从150s增加到300s时,PLA在210℃的非牛顿指数从0.44增加到0.68,剪切速率为100~5000s-1的黏流活化能从32.99~91.67kJ/mol增加到50.40~141.52kJ/mol。     

纺丝用可熔性聚四氟乙烯的流变性能研究

采用毛细管流变仪,对PFA熔体的流变性能进行研究。讨论了温度、剪切速率对纺丝用PFA熔体的非牛顿指数、表观粘度、结构粘度指数等方面的影响。结果表明,PFA熔体非牛顿指数随温度上升而升高。在不同温度下,PFA熔体的粘度均随着剪切速率的增大而减小,表观粘流活化能随剪切速率增加而减小。PFA熔体的结构粘度指数Δη随熔体温度的增高而逐渐减小。     

Influence of molecular architecture and melt rheological characteristic on the optical properties of LDPE blown films

A systematic investigation on the origin of the haze of LDPE blown films was conducted, aiming to correlate the film haze with the molecular architecture and melt rheological properties. First of all, the haze measurement indicated that the surface haze, rather than the bulk haze, is the dominating factor for the total haze of the investigated films. No spherulitic crystals or other superstructures were observed for the LDPE blown films, implying that the crystallites formed in the film-blowing process are too small to be responsible for the optical haze. Rheological study revealed that the surface roughness was originated from the irregular flow of LDPE melt during the extrusion process. NMR, GPC and parallel-plate rheology were applied to study the molecular architecture of the LDPE resins. It was found that the LDPE sample with higher haze value exhibits distinctly larger portion of higher molecular weight component, broader molar mass distribution, significantly higher side chain branch density.     

PP/PET共混熔体的流变性能研究

以PP-g-AA作增容剂,研究了PP/PET共混熔体的流变行为。讨论了温度、剪切速率以及PET和增容剂含量对熔体表观粘度、非牛顿指数等方面的影响。结果表明,PP/PET共混物熔体表观粘度随剪切速率的增大而降低,随PET及增容剂含量的增加而下降,随温度的升高而下降。PET和增容剂的加入,在共混熔体中起到了增塑剂的作用。     

Non-isothermal rheological response in melt spinning and idealized elongational flow

Almost all polymer processing operations involve moving and shaping the polymer as a melt and then cooling it, usually quite rapidly, to a solid state. In order to develop models for such processes we have begun systematic studies in non-isothermal rheology; here we interpret the results in the context of melt spinning. Theoretical predictions of stress vs distance from the spinneret were calculated from generalized (non-isothermal) viscoelastic theory and compared with Dees' melt spinning data on high density polyethylene. Despite certain experimental and theoretical difficulties, the agreement is good. Surprisingly, an additional theoretical curve, based on a simple Trouton viscosity, also gave a reasonable approximation over much of the distance, despite the transient nature of the flow. To understand this phenomenon further, a more tractable theoretical problem was studied in detail; the problem, of constant elongational flow (? = constant) in the presence of a constant rate of temperature change (dT/dt = constant). The results depend on two dimensionless groupings; the first is the usual product of a relaxation time and ?; the second involves the ratio of normalized dT/dt to ?. When the second group is large, a quasi-viscous state exists. The melt spinning data for the HDPE may be near this state.     

改性PBT熔体流变性能及其对可纺性影响研究

利用毛细管流变对不同组成的改性聚对苯二甲酸丁二醇酯(PBT)树脂进行了流变行为研究,探讨了流变性能差异对可纺性的影响。结果表明:不同组成的改性PBT熔体均呈现剪切变稀现象,具有非牛顿流体的流动特征;随着温度升高,改性PBT熔体的非牛顿指数n增大;改性PBT熔体的粘流活化能相对较小,对温度敏感度低,有利于纺丝成型;改性PBT熔体的结构黏度指数介于0.7～1.0,预期其可纺性和稳定性较好。     

聚己内酯单丝熔融纺丝工艺技术研究

聚己内酯（PCL）是一种全微生物分解性高分子聚合物,由于其降解产物无毒,在生物医学、纺织服装和环保领域都得到了广泛的关注。在水平牵伸单丝实验设备上进行PCL熔融纺丝试验,通过对切片干燥、螺杆温度、水浴温度、牵伸比等工艺参数的调试和控制。探索了PCL熔融纺丝的工艺参数和关键技术。试验表明,采用切片干燥温度50~55℃、干燥时间13~18 h、纺丝温度150~180℃、牵伸比3.8~4.3等工艺参数,可制得直径为0.14 mm、物理性能指标良好的单丝样品。     

Extrudate swell during the melt spinning of fibers—influence of rheological properties and take-up force

A theoretical and experimental study has been carried out on extrudate swell B, especially the influence of rheological properties and applied take-up force on the emerging melt. The problem is analyzed in terms of (1) dimensional analysis, (2) force–momentum balances, (3) partially constrained elastic recovery. Analyses in terms of force–momentum balances are only able to give extrudate swell B in the asymptote of high Reynolds numbers. For low Reynolds numbers, they simply relate the take-up force to the pressure field in the spinneret. Increasing the take-up force predicts a decrease in the exit pressure. The partially constrained elastic recovery theory yields an expression for B as a decreasing function of applied take-up force. Specifically, this is where B(0) is the extrudate swell in the absence of applied forces, λ_eff is the effective relaxation time, μ is viscosity (both evaluated at the capillary wall), and D is the spinneret capillary diameter. An experimental study of extrudate swell of several rheologically characterized melts (high density polyethylene, low-density polyethylene, polypropylene, polystyrene) has been carried out at 180°C by four different methods (frozen, annealed in hot silicone oil, photographed emerging into air, photographed emerging through 180°C silicone oil) in the absence of applied take-up forces. Extrudate swell for a melt emerging from dies with differing diameters correlates with capillary-wall shear rate. A comparison of extrudate swell with normal stress–shear stress ratio shows the best agreement for frozen extrudates and photographs of melts emerging into air. The data is compared to the Tanner theory of extrudate swell. B has been determined during melt spinning and shown to be a function of take-up force for both a high-density polyethylene and polypropylene melt. B decreases rapidly with applied take-up stresses. The results are compared to the predictions of the partially constrained elastic recovery theory.     

三叶异形聚乳酸纤维的熔融纺丝及其性能研究

以特性粘数1．51 dL／g的聚乳酸(PLA)为原料,采用三叶异形喷丝板一步法熔融纺丝制备出异形度为52％的三叶异形PLA纤维,研究了其热性能和机械性能。结果表明,PLA纤维的断裂强度和初始模量随拉伸倍数的增加而提高,经4倍拉伸,其断裂强度为2．39 cN／dtex,初始模量为17．27 cN／dtex。由于PLA的慢速冷却结晶过程,纤维在成形过程中形成不同晶层厚度的结晶结构。纺丝过程中纤维皮层结构受到更大的拉伸取向作用,并在纤维表面出现一定游离原纤化结构。