含氟弹性体/聚乙烯蜡复合润滑剂对HDPE流变性能的影响

为了改善高密度聚乙烯(HDPE)熔体的流动不稳定性,在HDPE中添加了不同份数的含氟弹性体/聚乙烯蜡复合润滑剂。试验结果表明:在HDPE5000S加入0.125份含氟弹性体/5份聚乙烯蜡复合润滑剂,熔体不稳定流动现象在低剪切速率下明显改善。     

A new processing aid for the extrusion of polyolefins

The influence of a new processing additive (a composition of fine particles of boron nitride) on the rheology and processability of molten polymers is studied. The equipment used includes both an Instron capillary rheometer with special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer and a parallelplate rheometer. Two metallocene polyethylenes with several types of boron nitride powders varying in particle size distribution are tested at various concentration levels. The powder having the finest particle size was found to have the greatest influence in the processing of polyolefins using crosshead dies and tips. As a result, its use eliminates surface melt fracture and postpones the critical shear rate for the onset of gross melt fracture to significantly higher values depending on the additive concentration. The performance of the boron nitride in eliminating melt fracture is compared with that of a typical fluoroelastomer. It is shown that boron nitride is a superior processing aid.     

纳米粉体在聚合物熔体中的分散理论

综述了纳米粉体在聚合物熔体中的分散理论,包括纳米粉体聚集体中聚集力的模型及影响因素、纳米粉体聚集体在流场中所受外力的模型及影响因素,介绍了纳米粉体聚集体分散的破裂机理和剥蚀机理,评述了各个模型及相关机理的优点和局限性,建议要将更多的影响因素如表面能等引入模型中,要考虑破裂分散与剥蚀分散之间的竞争关系,注重分散结构在加工过程中的演变过程,以强化分散模型的动力学特征。     

The effect of nanoclays on the processibility of polyolefins

The influence of a new processing additive (particles of organically modified nanoclays) on the processibility of polyolefins in extrusion is studied. The equipment used includes an Instron capillary rheometer with two types of dies, namely capillary dies and special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer. Ziegler Natta and metallocene polyethylenes and one polypropylene were tested using these two pieces of equipment. It was found that the nanoclay additive had a significant effect on the extrudate appearance of polyethylene. It eliminates surface melt fracture and postpones the critical shear rate for the onset of gross melt fracture to significantly higher values depending on resin type, temperature, and additive concentration (typically 0.05 to 0.5 wt%). To explain the possible mechanism for the effect of the additive on the processibility of the resins, shear and extensional rheological measurements were carried out for the pure resins as well those loaded with the nanoclay additives. It seems that the presence of nanoclays suppresses the development of extensional stresses to such high levels that can cause melt fracture phenomena. Finally, it was found that the combination of nanoclays with traditional processing aids such as fluoropolymers produce an enhanced processing aid that can increase the critical shear rates for the onset of melt fracture to levels much higher than the individual constituents when they are used independently. POLYM. ENG. SCI., 45:1098–1107, 2005. © 2005 Society of Plastics Engineers     

Effect of combining boron nitride with fluoroelastomer on the melt fracture of HDPE in extrusion blow molding

Boron nitride (BN) is a new polymer processing aid which not only eliminates surface melt fracture in the extrusion of molten polymers, but also postpones the critical shear rate for the onset of gross melt fracture to significantly higher values that depend on resin type and additive concentration. In this work, the influence of BN as a polymer processing additive is first examined in the extrusion blow molding of high‐density polyethylene (HDPE) resins in order to evaluate its usefulness and performance in operations other than continuous extrusion. The equipment used includes both a Battenfeld/Fisher 50‐mm extrusion blow molding machine and a parallel‐plate rheometer. Two types of HDPE, which are blended with boron nitride at various concentration levels, are tested accordingly. It is found that the degree of BN dispersion, characteristics of the HDPE resins, extrusion temperature, and induction time play an important role in eliminating melt fracture. Finally, the influence of combining BN with fluoroelastomer, as an enhanced and potentially better processing aid on the melt fracture of a third HDPE is examined. It is found that such a combination is a superior processing aid that allows extrusion blow molding at very high shear rates.     

Blends and interpenetrating polymer networks of polypropylene and polystyrene-block-poly(ethylene-stat-butylene)-block-polystyrene. 2: Melt flow and injection molding properties

Injection molding and melt flow properties of a set of blends prepared by mixing the triblock thermoplastic elastomer polystyrene-block-poly(ethylene-stat-buty-lene)-block-polystyrene with polypropylene and a processing oil are reported. Despite the high viscosity of the thermoplastic elastomer, the melt viscosity of the blends was similar to or lower than that of the pure polypropylene. The rheological behavior of the molten blends seems to be dominated by a low-viscosity melt phase containing mainly polypropylene and oil. The surface of solidified extrudates from the capillary rheometer was rich in polypropylene and free from large domains of the thermoplastic elastomer. Injection molded plates had a similar surface morphology, although in this case, larger domains of the elastomeric phase were found in narrow, band-shaped surface regions. These local surface heterogeneities were probably caused by flow-induced phase segregation during mold filling. Weld lines in injection molded test pieces prepared from blends within the composition range giving interpenetrating network structures had no noticeable effect on either stress-strain behavior or falling dart impact strength.     

Interfacial interactions and the properties of filled polymers: I. Dynamic-mechanical responses

The dynamic mechanical responses of rutile-filled, chlorinated polyethylene (CPE) were studied as a function of temperature, of filler loading, and of filler surface condition. An objective was to establish the influence of matrix-filler interactions on mechanical properties. Necessary information on potential interactions between matrix and filler was obtained from inverse gas chromatographic data, in the form of an acid-base interaction parameter, Ω. The damping peak in filled CPE compounds was depressed by the pigment, as called for by theoretical models. The magnitude of the effect exceeded expectations, however, and clearly depended on the strength of interfacial interactions. These were consistent with the acid-base ranking of CPE and the various rutiles, as given by Ω. It has been postulated that in the presence of acid-base interactions, an immobilized layer of polymer in the vicinity of solid particles increases the effective particle dimension, thereby accounting for the observed variations in relative damping. Additional effects of matrix-filler interaction were noted in the variation of storage moduli with loading and temperature. Again, the effects tend to be more pronounced when significant specific interactions between matrix and solid are operative. These observations point to the inadequacy of existing models as interpretative bases for dynamic mechanical properties in systems with significant specifie interactions among their components.     

Modifying polyester surfaces with incompatible polymer additives

Surface modification of amorphous PET in incompatible blends is demonstrated using fluorocarbon end-functional polystyrenes. Contact angles with water and decane were consistent with high levels of surface fluorocarbon, even for spin-cast films with no further processing required. Hydrophobicity and lipophobicity were further increased by annealing above the glass transition temperature. High resolution depth profiling using complementary ion beam analysis and specular neutron reflectometry has enabled accurate characterisation of the composition profile of the additive including the minimum in additive concentration found just below the surface enriched layer. This analysis quantified the very low compatibility between the modifying polymer and the amorphous PET and was consistent with the highly segregated nature of the adsorbing species and its sharp interface with the subphase. For these incompatible polymer blends, surfaces enriched with the surface active polymer could coexist at equilibrium with extremely low (∼0.4%) bulk loadings of the additive. This suggests that for thicker films at even lower additive concentrations than the minimum 1% that we studied, it may be possible to achieve efficient surface modification. However, at this concentration, the efficiency of surface modification is limited by the processing conditions. Finally we note that in higher loadings of surface active additive there is clear evidence for lateral phase separation into patterned domains of differing composition. The enhancement in surface properties is due to local reorganisation rather than bulk redistribution of the components within the film, as the composition versus depth distributions of the polymer blend components was observed to be relatively unaffected by annealing.     

LLDPE 注塑专用树脂的开发

根据线型低密度聚乙烯注塑专用树脂的特点,确定了TJZS-9023的技术指标熔体流动速率为23g/10min,密度为0.922g/cm3。研究了TJZS-9023的添加剂配方体系及其性能,并考虑了热氧稳定体系的协同效果,最终筛选出最佳添加剂配方。试生产的专用树脂的屈服拉伸强度达到11.0MPa,拉伸弹性模量达到362MPa。生产厂家的加工应用表明,TJZS-9023与同类进口树脂性能相当。     

Tribological performance of self-lubricating polyurethane elastomer compounding with the modified ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) powder was modified by surface treatment technology, then its wettability, dispersibility, mechanical, and tribological properties in polyurethane elastomer were studied. The testing results showed that after surface treatment, UHMWPE powder could infiltrate and disperse evenly in polyurethane, and build micro cross-link with the contact surface of polymer substrate, which is conducive to enhancing the internal stress of polymer and improving the mechanical properties. With a small amount of modified UHMWPE being added into the casting polyurethane (CPU) elastomer, the right-angled tearing strength increases and the abrasion loss decreases. Moreover, the elastomer surface self-lubricating performance of CPU compounding with modified UHMWPE is enhanced: compared with the neat CPU sample, the average friction coefficient of the CPU samples with 5%, 10%, and 15% of modified UHMWPE is reduced by 46.3%, 41.5%, and 39.0%, respectively, and the surface wear resistance is improved; under the high-load working condition, the CPU elastomer with 5% of modified UHMWPE has the optimal tribological performance.     

Surface modification strategies for multicomponent polymer systems. V. Interaction states and mechanical properties of LLDPE/PVC blends with corona-modified rutile pigment

Rutile pigment with preadsorbed monomers of acrylamide (AM) or acrylic acid (AA) has been treated in air corona discharges at various input power levels for times from 30–120 s. Inverse gas chromatographic data showed that the treatments reduced dispersive surface energies and significantly altered the acid/base interaction potential of the surfaces. Inferred is the corona-activated synthesis of oligomeric or polymeric structures anchored to the pigment surface. XPS analyses report modifications in the chemical structure of pigment surfaces, which are consistent with the suggested consequence of corona treatment. When incorporated into LLDPE and PVC host polymers, compounds with the corona-modified rutiles have better mechanical properties than analogues with untreated pigment, notable being improved elastic moduli, yield stresses, and stress/strain relationships at break. AM-modified rutiles were preferable to AA-modified versions in this regard. The addition of treated pigments to immiscible LLDPE/PVC (75/25) blends resulted in similar benefits to mechanical properties, AM pretreatment again being preferred. Stronger acid-base interaction at contacts between corona-modified rutiles and the PVC component is an apparent reason for improved mechanical properties. Speculatively also, AM pretreatments lead to attached chains of sufficient length to entangle with the LLDPE, further strengthening the interphase and relevant bulk properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1597–1604, 1998     

氟弹性体类加工助剂改性双向拉伸薄膜用PP

采用氟弹性体加工助剂母粒(简称母粒)对聚丙烯(PP)进行改性,考察了双向拉伸薄膜用PP(BOPP)的光学性能、力学性能和加工性能。结果表明:母粒对PP结晶度有一定影响,可提高结晶速率,且助剂质量分数为0.06%时对PP结晶度的影响最大;母粒会降低BOPP薄膜雾度,与只在BOPP薄膜的芯层加入母粒相比,在芯层和表层同时加入母粒,更易降低BOPP薄膜雾度;仅在BOPP薄膜芯层加入母粒,薄膜的光泽度更好;薄膜纵向的力学性能有所下降,但都能满足标准要求,母粒还能降低PP熔体表观黏度及剪切应力,改善加工性能。     

双组分改性聚氨酯水工防腐涂层性能研究

采用柔性材料防护水利过流部件解决其运行过程中气蚀、磨蚀及其联合作用导致的破坏问题。以化学改性的方式在聚氨酯侧链上引入氟碳链及疏水性基团,合成兼具聚氨酯弹性体、氟碳化合物双组分性能的涂层材料。通过对涂层制备过程中喷涂压力、温度等喷涂工艺参数优化制备性能最佳涂层。对材料进行疏水性、冲蚀磨损、人工老化等测试,采用扫描电镜对涂层微观形貌进行观察,分析磨蚀机理对涂层性能及防护效果影响。结果表明：所制备涂层可有效提升过流部件的防腐耐磨性能。     

耐刮擦、高流动PP/SEBS热塑性弹性体的研制

采用熔融共混法制备了聚丙烯(PP)/氢化苯乙烯–丁二烯–苯乙烯嵌段共聚物(SEBS)热塑性弹性体,研究了乙烯丙烯酸酯共聚物润滑偶联改性剂(YY–503和YY–5031)、芥酸酰胺和高分子量硅酮(E525)4种改性剂对PP/SEBS弹性体的加工性能、力学性能和耐刮擦性能的影响。结果表明,4种改性剂的加入能显著提高弹性体的熔体流动速率(MFR),添加YY–503和E525的弹性体MFR提升更为显著,分别为12.6 g/10 min和13.5 g/10 min,比未添加时提高了2 471.4%和2 655.1%;添加芥酸酰胺的弹性体拉伸强度和断裂伸长率最低,比未添加改性剂时分别下降了58.5%和63.2%,添加YY–503和YY–5031的弹性体拉伸强度分别为10.6 MPa和9.8 MPa,比未添加改性剂时分别提高23.2%和19.5%;未添加改性剂弹性体的色差值(ΔL)为18.5,而添加YY–503和YY–5031的弹性体ΔL仅为1.3和1.5;扫描电子显微镜测试发现,添加YY–503和YY–5031的弹性体中没有出现明显孔洞,碳酸钙良好分散,与基体结合力良好。添加质量分数为2%的YY–503可获得力学性能、加工性能和耐刮擦性能优异的PP/SEBS弹性体。     

Additives to prevent the formation of surface defects during poly(vinyl chloride) calendering

Gas checks are visible fleck-shaped defects that occur on the surface of poly(vinyl chloride) (PVC) films during industrial calendering. Films containing these surface defects often do not meet minimum product specifications and therefore must be disposed of or recycled, resulting in increased cost and material waste. Currently, gas checks are controlled by keeping film gauge low and through trial-and-error modifications of processing parameters by calender operators. In this work, our group developed a series of chemical additives that can be blended with PVC to prevent the formation of gas check defects. We found that a series of poly(caprolactone) (PCL)-based compounds with diester linkers and alkyl chain cappers were all effective at preventing the formation of gas checks during calendering, with additive concentrations as low as 8 phr producing films with no gas checks. We found that the blends produced with our additives had higher melt viscosities than those produced with additives that do not remove gas checks, suggesting that viscosity plays an important role in preventing gas check defects.     

生物质燃油碳烟颗粒的分散特性

碳烟分散性能是柴油机油的一项重要性能指标,采用黏度法、斑点实验法及粒径分布法考察了生物质燃油碳烟(BS)和0^#柴油碳烟(DS)在液体石蜡(LP)中的分散性能及商用分散剂聚异丁烯丁二酰亚胺(T154)对其分散性的影响,并借助X射线光电子能谱仪和傅里叶红外光谱仪分析其分散机理。结果表明,BS和DS表面均带有一些含氧官能团且BS氧含量高于DS;DS对体系增稠作用大于BS,T154对BS和DS在LP中的分散性均有良好的作用,但对BS的分散效果更好。T154亦可作为BS在润滑油中的分散剂使用,因为BS表面含有羧基、酚羟基等含氧酸性基团,可与T154中丁二酰亚胺依靠酸碱作用吸附分散剂。同时,BS表面的极性基团与N-H单元产生氢键而吸附T154。     

Interactions between sorbitol-type nucleator and additives for polypropylene

The thermal properties of a sorbitol-type nucleating agent (viz. 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol (TBPMN)) were examined in this study, and the influence of common processing additives assessed. In addition, we describe a novel approach to monitor in situ the self-assembly of the nucleator in presence of additives by optical microscopy. The performance of sorbitol compounds is closely associated to their chemical structure and ability to self-assemble. TBPMN formed elongated fibrils from the melt under inert atmosphere, in molted polypropylene, or in presence of antioxidants. However, calcium stearate (CaSt) and glycerol monostearate hampered growth, and yielded thinner fibrils. In presence of the additives, melting point depression of the nucleator occurred, and resulted in a lower degree of crystallinity upon cooling. Performance evaluation of the nucleator in polypropylene blends revealed an increased crystallization temperature when antioxidants were present, while CaSt inhibited nucleator activity. The effect of mono-glycerides was found highly dependent on the processing conditions. Noteworthy, blends containing all the additives displayed the highest performance. This study highlights the importance of the preparation method of polymer additive blends to achieving the best performance in the final product. Characterization was performed by thermogravimetric analysis, Fourier-transform infrared spectroscopy, optical microscopy, and differential scanning calorimetry.     

The Impact of In‐situ Fabric Surface Energy on Dehydration of Fabrics

Reducing liquid surface tension is widely used to increase the efficiency of the centrifugal dehydration in textile wet processing. However, increasing the dehydration efficiency by decreasing fabric surface energy is seldom studied. In this work, the impact of in situ fabric surface energy on residual moisture content (RMC) of fabrics in the dehydration processes was investigated. Different types of fluorocarbon surfactants including cationic, anionic, nonionic and amphoteric were adopted as additives in this study. The liquid surface tension and RMC were efficiently decreased when fluorocarbon surfactants were used. Notably, a cationic fluorocarbon surfactant displays similar surface tension but distinct dehydration efficiency. The in situ fabric surface energy was evaluated by measuring the n‐octane contact angle on the cotton fabric surface under the surfactant solution using the captive bubble method. It was found that the cationic fluorocarbon surfactant system gave the lowest fabric surface energy, which was probably because cationic fluorocarbon surfactants are easier to adsorb onto the surface of cotton fabric to form a fluorocarbon layer. The chemical composition (¹⁹F, ¹²C and ¹⁶O) analysis of the cotton fabric surface by X‐ray photoelectron spectroscopy confirms the hypothesis.     

Bond Characteristics at Pigment-Polymer Interfaces

An assessment was made of the effectiveness of bonding polymers from solution to dispersed solids by dispersive and non-dispersive forces. The polymers included neutral low density polyethylene (LDPE), a basic ethylene co-vinyl acetate (EVA) and an acidic chlorinated polyethylene (CPE). The solids included surface coated rutiles, an organic colorant and the chromatographic support Chromosorb.^® The quality of polymer-solids bonds was estimated by eluting adsorbed polymers with p-xylene under reflux. The amount of polymer recovered was a function of acid-base forces acting at the polymer-solid interface. LDPE was recovered quantitatively, as were EVA and CPE when these were adsorbed on like (acid or base) solids but recovery was limited when significant acid-base interaction occurred. These results were relevant to the stabilization of solids dispersed in polymer solutions. Sedimentation experiments noted that the absence of acid-base interactions as well as an excess of these non-dispersive forces was detrimental to the stability of dispersions. For the specific systems under study, however, it was possible to define a preferred, intermediate range of acid-base interactions for dispersion stability. The configuration of adsorbed polymer chains was suggested to be an important consideration in this regard.     

聚甲醛纤维的制备与性能

采用熔融纺丝方法,通过调整纺丝工艺参数中的卷绕速度及后牵伸倍数,制备了不同工艺下的聚甲醛(POM)纤维;通过对热性能、取向度和力学性能的测试,分析了POM树脂结晶和降解等热学性能对纺丝过程的影响,同时研究了纺丝工艺参数对POM纤维性能的影响;最后对POM纤维的耐酸碱性能进行了研究。结果表明:POM纤维最佳的纺丝速度为490 m/min,牵伸倍数为7.4。POM纤维的耐碱及耐弱酸性好。