渔用自增强HDPE单丝的取向结构及力学性能

采用自增强技术制备了渔用自增强高密度聚乙烯(HDPE)单丝,通过广角X-射线衍射(WAXD)、声速法等比较了渔用自增强HDPE单丝和普通HDPE单丝的取向结构及力学性能。结果表明,渔用自增强HDPE单丝比普通HDPE单丝的晶面间距、晶胞参数和微晶尺寸稍大,结晶度、取向度、声速取向因子、断裂强度、结节强度和结强损失率增加。     

挤出比对固态挤出成型自增强木塑复合材料性能的影响

采用稳定、连续的固态挤出成型装置制备了高度取向的自增强木塑复合材料棒材,考察了其性能及结构。力学性能测试结果表明,随着挤出比的增大,复合材料的弯曲弹性模量从2400 MPa提高到5800 MPa,拉伸强度从20.7 MPa提高到81.6 MPa。扫描电子显微镜观察发现,复合材料内部形成了大量沿挤出方向有序排列的微纤结构。差示扫描量热分析结果表明,与常规挤出的复合材料相比,自增强复合材料的熔融峰向高温方向漂移,结晶度随挤出比的增大而明显上升。     

振动塑化挤出对聚烯烃片材性能的影响

利用塑料电磁塑化挤出机挤出聚烯烃片材，系统研究了挤出机螺杆轴向振动对聚乙烯挤出制品结构与性能的影响。采用DSC对挤出试样的结晶结构及形态进行分析。结果表明，振动塑化挤出使聚合物挤出试样结晶度提高，结晶完善，晶片之间的连接分子数量增加，因而制品的力学性能有所提高，特别在横向上表现明显。在适当的振动条件下，高密度聚乙烯（HDPE）试样的横向拉伸强度和冲击强度分别从22．68MPa和12．7kJ／m^2提高到了25．55MPa和23．5kJ／m^2；而聚丙烯（PP）试样横向拉伸强度和冲击强度则分别提高了20％和64％。     

自增强HDPE棒材的制备与结构形态

采用普通挤出设备,通过流动诱导结晶的方法制备了自增强HDPE棒材(直径5mm)。分析了自增强棒材的制备过程,并采用SEM观察与DSC分析,对其结构形态进行了研究。结果表明,流动条件、挤出压力与熔体温度是由聚合物熔体连续挤出方法成型自增强体型制品的重要影响因素;自增强棒材内形成了具有较高耐热性能的微纤结构,尤其是较高挤出压力(如60MPa)下制备的棒材。     

动态保压注射成型HDPE/Nano-OMMT复合材料的结构与性能

聚合物/黏土纳米复合材料是近几年聚合物材料改性的热点。为了进一步理解复合材料性能与结构的关系,利用自行研制的动态保压装置,借助WAXD、DSC、SEM等测试方法,研究了高密度聚乙烯(HDPE)/纳米有机蒙脱土(nano-OMMT)复合材料的结构与性能。结果表明,动态保压使OMMT纳米粒子在基体中的分散性提高,并形成插层结构。与此同时,动态剪切力场使HDPE/nano-OMMT复合材料的HDPE基体结构形态亦发生变化,试样中生成串晶结构,相比常规注塑试样,动态保压试样结晶度最大提高15%,结晶形态的变化和结晶度的提高均有利于HDPE/nano-OMMT复合材料强度的提高。力学性能试验显示,拉伸强度和冲击强度同时得到提高,HDPE/nano-OMMT复合试样的拉伸强度最大提高了119%,冲击强度最大提高430%。     

高密度聚乙烯/纳米纤维素纤维复合材料的制备及表征

用挤出成型法制备了高密度聚乙烯/纳米纤维素纤维(HDPE/NCF)复合材料,利用FE-SEM、DSC、XRD等方法考察了复合材料的微观结构、晶态结构、力学性能以及热性能。结果表明:NCF能均匀地分散在HDPE基体中,对HDPE有良好的增强效果,当NCF用量为12%时,复合材料的拉伸强度可达37.4 MPa,与纯HDPE相比提高了44.7%,但复合材料的脆性提高;NCF可提高HDPE的熔点和结晶度,但随着NCF用量的增加,HDPE的熔点与结晶度又会下降;NCF的引入并未改变HDPE的晶型。     

振动挤出HDPE管材的结构与力学性能

使用自制的电磁动态塑化挤出机和螺旋芯棒式机头挤出高密度聚乙烯(HDPE)管材.采用爆破压力测试,拉伸性能测试,差示扫描量热法分析等研究振动频率和振幅对HDPE管材结构与力学性能的影响.振动挤出的HDPE管材周向强度显著提高,实现了管材的双向自增强.与稳态相比,振动挤出的HDPE管材结晶度提高,熔点升高,结晶完善;爆破压力最大提高了34.2%,轴向拉伸屈服应力最大提高了5.3%.     

木粉的碱化处理对木塑复合材料性能的影响

采用木粉填充高密度聚乙烯（HDPE）制备复合材料。为增强亲水性的木粉和憎水性的HDPE基质之间的化学亲和力,对木粉碱化处理。研究了相容剂用量和木粉的碱化处理对复合材料力学性能的影响。结果显示,马来酸酐接枝HDPE可明显提高复合材料的力学性能．表现出很好的增容效果：与用未碱化处理的木粉填充的复合材料相比,木粉的碱化处理使复合材料的弯曲强度和弯曲模量分别下降20．4％和36．2％：在不使用相容剂的情况下,木粉的碱化处理也会使复合材料的拉伸强度下降．但在使用适量相容剂后．则可使复合材料的拉伸强度从未处理时的30．3MPa提高到36．5MPa,与纯HDPE相比,拉伸强度提高了44.8％。     

动态保压注塑成型中少量HMWPE的诱导对HDPE结晶的影响

探讨了在动态保压注射成型中少量高摩尔质量聚乙烯(HMWPE)的诱导作用对高密度聚乙烯(HDPE)结晶行为的影响.通过扫描电子显微镜(SEM)可观测到HDPE在HMWP诱导下生成了一种类似网状的串晶结构.该结构沿流动方向高度取向,垂直流动方向的片晶相互连接.实验结果证明,该结构可以同时大幅度提高试样的强度和韧性,其结构大大优于一般的串晶结构.差示扫描量热法(DSC)测试结果表明,少量HMWPE诱导的HDPE动态成型试样(B4)结晶度明显高于普通成型试样(SO)和未加高分子诱导的动态成型试样(BO).广角X射线衍射(WAXD)结果显示B4内部晶体沿着流动方向的取向度也明显高于SO和BO.本研究可得到如下结论:少量HMWPE确实能有效诱导HDPE的结晶和取向,使HDPE的结晶行为得到明显改善.     

复合应力场下挤出HDPE增强管材性能的研究

用自行研制的能产生先剪切后拉伸的复合应力场挤出成型装置，挤出高密度聚乙烯（HDPE）管材，对管材周向、轴向力学性能进行了初步的研究。与一般牌号为DGDA6098的HDPE比，在HDPE中添加高相对分子质量高密度聚乙烯（HMWHDPE）后，发现HMWHDPE能够诱导HDPE沿应力场方向产生大分子取向和结晶。利用差示扫描量热仪（DSC）和扫描电镜（SEM）检测手段对试样的凝聚态结构进行分析，证实了复合应力场下制备的自增强管材双向力学性能都提高了。     

Effect of annular expansion pipe extruder head on mechanical properties of pipes

With polymer pipes being used more commonly, performance requirements are increasing. Studies on the enhancement of mechanical properties of polymer pipes are particularly important. In this study, a self-designed annular expansion pipe extruder head was used to enhance the mechanical properties of HDPE pipes. Different morphologies of the HDPE pipes were produced under different processing conditions. When the extrusion angle was 30° (P30), the best mechanical properties were obtained. The hoop tensile strength and axial tensile strength were 14.5% and 41.0% higher, respectively, compared with the specimen without expansion (P0). This improvement of mechanical properties can be attributed to several reasons. First, the processing parameters of P30 reached the threshold shear rate and strain for shish-kebab formation, as shown by scanning electron microscopy. Second, P30 has the highest orientation parameter and crystallinity of 0.679 and 67.27%, respectively, from 2D wide-angle diffraction (WAXD). Polarized FTIR shows the same trend as 2D-WAXD. Third, the outer bamboo-like self-reinforced structure is formed inside the pipe at 30° expansion angle while the core layer has a well-formed crystal structure; the special structure improves the overall performance of HDPE pipe. This method can be utilized in large-scale industrial production.     

Strength retention of self-reinforced,absorbable polyglycolide rods in hydrolytic environment

Absorbable polyglycolide suture fibers were sintered with the compression molding techniques to cylindrical rods at temperatures between 205°C and 232°C for 3–5 min with final pressures of 50–80 N/mm². The cylindrical rods had nominal diameters between 1.5–4.5 mm and a length of 50 mm. The initial bending moduli and the initial bending strengths of the rods were between 9–15 GPa and 220–430 MPa, respectively. The shear strengths of the rods were between 165–255 MPa. The hydrolytic loss of mechanical strength of the above self-reinforced, absorabable polyglycolide rods were studied in phosphate buffer at 37°C and 77°C. It was found that the rate of strength loss decreases with the increasing diameter of the rods. On the other hand, the rate of strength loss increases when the temperature of the buffer solution is raised. The strength, retention time at 37°C was between 7–10 weeks showing that the loss of mechanical strength of self-reinforced polyglycolide rods occurs more rapidly in vivo than in vitro.     

双向自增强PE-HD管材的制备及其增强效果的研究

利用自行设计制造的剪切拉伸双向复合应力场挤管装置制备了轴、周向同时获得自增强的高密度聚乙烯管材。采用万能电子拉力试验机和差示扫描量热仪（DSC）对增强效果及其原因进行了研究。结果表明,剪切拉伸双向复合应力场不仅能明显改善管材轴、周向的力学性能,而且能提升管材的结晶度,其轴向拉伸强度最高提高到30.56 MPa,提高了36.6 %,周向拉伸强度最高提高到33.5 MPa,提高了54.6 %,轴向拉伸模量最高提高到180.3 MPa,提高了47.4 %,周向拉伸模量最高提高到529.8 MPa,提高了140.7 %,结晶度提高了13.51 %,熔点提升了1.5 ℃。DSC测试结果表明,管材性能改善的原因是其结晶度的提高所致。     

单向拉伸流场中挤出双向自增强透明HDPE管材

采用普通的工业用挤出设备，通过对加工参数的特殊控制，在单向拉伸流场中制得透明双向增强高密度聚乙烯管材，其轴向拉伸强度比普通高密度聚乙烯管材提高了3．2倍，周向拉伸强度提高了1．4倍。利用SEM，DSC等测试手段对管材的微观结构进行了表征，揭示了管材双向自增强的原因是形成了串晶互锁结构，管材透明的原因是晶粒尺寸比可见光的波长小。     

Continuous extrusion of self-reinforced high density polyethylene

Continuous extrusion was studied of self-reinforced high density polyethylene (HDPE) sheets from flow-induced crystallization at die pressures varying from 30 to 60 MPa. Their morphology, thermal behavior, tensile strength, and light transmittance were tested. Flow fields of a polymer melt through a converging wedge channel were also investigated by direct visual observations in conjuction with a theoretical analysis. The extensional strain rate increased abruptly as the melt approached the exit of the converging channel, this resulting in a higher crystallization rate. So, achieving the crystallization of molecular chains just in front of the exit of the converging channel may favor to extrude the bulk polymeric materials having high properties under lower pressures (e.g., 40 MPa or lower), this having been realized in the present work. The tensile strength of the self-reinforced HDPE sheet prepared at a 40 MPa pressure was enhanced by a factor of 8.     

复合应力场中HDPE诱导系的配比对管材结构与性能的影响

将质量分数分别为2%、6%和10%的相对高分子量高密度聚乙烯(HMWPE)加入相对低分子量高密度聚乙烯(HDPE)中组成诱导体系,并通过双向复合应力场挤管装置制得了双向自增强HDPE管材。结果表明,HM-WPE质量分数为6%的诱导体系所成型的双向自增强管材的力学性能最好、分子取向度最大、结晶度最高,晶片厚度较大。     

Studies on high density polyethylene (HDPE) functionalized by ultraviolet irradiation and its application

The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m^?2 and 45 W m^?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m^?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m^?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m^?1 to 30.2 MPa and 158 J m^?1, respectively. Copyright © 2003 Society of Chemical Industry     

振动挤出对HDPE/碳纤维复合材料流变行为和性能的影响

通过在挤出成型过程中引入振动场,研究了加工过程中HDPE/碳纤维(CF)复合材料在振动场中的流变行为,并借助拉伸性能检测以及差示扫描量热分析(DSC)、扫描电镜(SEM)等测试方法,分析了HDPE/CF复合材料的结构与性能。结果表明:振动挤出可以显著降低熔体的表观黏度,最大降幅为56.95%,同时还可改善制品的力学性能,拉伸强度最大增幅为15.1%;材料力学性能的提高可归因于其微观形态结构的变化,振动使HDPE/CF复合材料基体晶粒细化、晶体排列更加规整、结晶度略有提高,并增强了CF与基体间的界面黏合作用。