拉伸对非晶态聚醚醚酮结晶取向行为的影响

借助差示扫描量热仪(DSC)和广角X射线衍射仪(WAXD),研究了不同拉伸工艺对非晶态聚醚醚酮(PEEK)结晶取向行为的影响。结果表明:在较高的温度、较低的拉伸速率及拉伸比下,拉伸后样品为非晶体;样品拉伸后的冷结晶温度向较低温度移动。     

聚醚醚酮纤维的拉伸定形后处理研究

通过熔融纺丝制得聚醚醚酮(PEEK)纤维,并采用差示扫描量热仪(DSC)、声速取向测量仪、热重分析仪、单纱电子强力仪分别研究了干热拉伸及热定形处理对PEEK纤维结晶和取向、热稳定性及力学性能的影响。结果表明:随着热拉伸倍数增大,PEEK纤维取向度、结晶度增加,纤维的断裂强度增加,断裂伸长减小;PEEK纤维的热拉伸温度应选在200～240℃,热定形温度应为220～260℃;PEEK纤维的重结晶主要是在热拉伸过程中完成,热定形则进一步完善纤维的结晶结构;经过后处理,PEEK纤维的断裂强度可达到6.12cN/dtex;且具有优异的热稳定性能,热分解温度高达505℃,后处理几乎不影响PEEK纤维的热稳定性。     

PP和PS拉伸性能测试的影响因素研究

研究了不同拉伸速率及不同制样方式对PP和PS材料拉伸强度和断裂伸长率的影响.结果表明随着拉伸速率的增大,以上两种材料的拉伸强度均有所增加,而断裂伸长率却呈现出不同的变化;PS注塑成型试样的拉伸强度和断裂伸长率都明显高于压制成型的,PP注塑成型试样的断裂伸长率比压制成型的增加了69%,而拉伸强度几乎没改变,制得了"强而韧"的试样.     

聚醚醚酮薄膜的性能研究

采用挤出流延法制备了一系列聚醚醚酮（PEEK）薄膜,通过拉力机、差示扫描量热仪、紫外分光光度计、透光率雾度仪等对PEEK薄膜的基本性质、光学性能、力学性能进行了研究。结果表明,PEEK薄膜的透光率随结晶度的升高而降低;拉伸速率对拉伸强度、断裂伸长率的影响不大,拉伸速率快,屈服强度明显提高;拉伸强度随流延辊速度的增加而提高;双向拉伸的方法可使薄膜拉伸强度达到203 MPa;增加薄膜厚度、提高结晶度的方法可以提高薄膜的抗紫外性能。     

拉伸方式对聚醚醚酮纤维结构和性能的影响

采用进口聚醚醚酮(PEEK)树脂为原料,熔融纺丝制备了PEEK初生纤维,研究了一次拉伸和二次拉伸对PEEK纤维结构和力学性能的影响。结果表明:在150～270℃内,随着拉伸温度的提高,PEEK初生纤维的最大拉伸倍数增大,纤维的取向因子和力学性能提高;一次拉伸和二次拉伸时纤维的最大拉伸倍数相同,纤维的取向度、结晶度和力学性能基本相当,但二次拉伸纤维干热收缩率较低。二次拉伸时,总拉伸倍数相同,随着一段拉伸倍数的增大,纤维取向因子增大,力学性能提高;随着二段拉伸温度的提高,纤维结晶度增大,干热收缩率减小,取向因子基本相同,力学性能更优。     

汽车前挡玻璃夹层PVB膜厚度及含水率对性能的影响

通过对国内外4家企业生产的聚乙烯醇缩丁醛（PVB）膜进行测试,观察PVB膜厚度、含水率、拉伸性能与表面纹路对其使用性能造成的影响。结果表明,厚度稳定性好且含水率低的PVB膜具有更高的拉伸强度和断裂伸长率,这对提高玻璃的耐撞及吸能防护性能具有重要意义;厚度稳定性好的PVB膜表面纹路分布也相对更均匀。     

壳聚糖膜的制备及性能测定

以醋酸(HAc)为溶剂溶解原料壳聚糖(黏均分子量117万),流延烘干,经氢氧化钠溶液浸泡,洗涤干燥制得壳聚糖膜。详细考察了HAc浓度、原料浓度、NaOH浓度、碱液浸泡时间、增塑剂用量等因素对膜拉伸性能的影响。确定了最佳反应条件,即HAc浓度3%,原料浓度1.5%,NaOH浓度6%,碱液浸泡时间3 h,甘油加入量8%。在此条件下,壳聚糖膜的拉伸强度为88.74 MPa,断裂伸长率14.3%。     

PVC和CPE不同配比对干混料性能的影响

测定了PVC和CPE不同用量配比对制得的干混料性能指标的影响,结果表明:随着CPE用量的增加,干混料的硬度呈现下降的趋势,断裂伸长率急剧上升,拉伸强度急剧下降,塑化性能增加。     

聚醚醚酮的FDM工艺参数与结晶行为研究

采用熔融沉积成型技术(FDM)制备了聚醚醚酮(PEEK)试样,并应用试验设计(DOE)方法分析研究了打印层高、热台温度和打印速度对PEEK试样拉伸强度和结晶行为的影响。结果表明:当打印层高、热台温度和打印速度分别为0.10 mm、160℃、30 mm/s时试样的拉伸强度最大(82 MPa)。3个打印参数从试样的层间结合、缺陷与结晶行为等方面不同程度地影响着PEEK试样的拉伸强度;随着热台温度的提升,试样的结晶度提高。而在同一热台温度下,由于打印过程中存在的温度分布差异,试样存在着明显的结晶不均匀现象,从试样的中心到边缘、沿厚度增加方向,结晶度逐步降低。     

ABS树脂拉伸性能及形变机理的研究

研究了丙烯腈丁二烯苯乙烯共聚物（ABS）树脂在不同温度和不同拉伸速率时的拉伸行为以及物理老化对其拉伸行为的影响。结果表明,屈服强度随测试温度的升高而下降,断裂伸长率并不随着测试温度的升高而提高,直到测试温度升高到接近ABS树脂塑料相的玻璃化转变温度时,断裂伸长率才显著提高;断裂伸长率随拉伸速率的增加而降低,在不同的拉伸速率下,ABS的形变区内均可观察到银纹现象;在较高的拉伸速率下,形成的银纹数量较多,但银纹较短,银纹的扩展得到了有效抑制;ABS树脂经物理老化后断裂伸长率明显降低,银纹数量增加并出现了空洞成串现象。     

Morphological, Thermal, Barrier and Mechanical Properties of LDPE/EVOH Blends in Extruded Blown Films

We have investigated the morphological, thermal, barrier, and mechanical properties of low-density polyethylene/ethylene–vinyl alcohol blend (LDPE/EVOH; 85/15 wt%) in highly and biaxially oriented blown films. Maleic anhydride-grafted linear low-density polyethylene (LDPE-g-MAH) in various concentrations (from 0 to 10 phr) was used as the compatibilizer for the immiscible system. Thermal analysis of the blend films shows that their melting temperatures, crystallization temperatures, and heats of fusion stay almost constant upon varying the amount of compatibilizer. The addition of the compatibilizer did not adversely affect the inherent properties of the blends, especially their barrier properties, through constraint effects of the grafted EVOH (EVOH-g-LD). The heat of fusion of EVOH obtained during the first heating is much higher than that of the second as a result of stress-induced crystallization during the blown film process. Oxygen permeation measurements show that the oxygen barrier properties of both highly and biaxially oriented blown films decrease upon increasing the amount of compatibilizer, although morphological analysis showed that the blends exhibit better laminar dispersion of the EVOH phase in the LDPE matrix when LDPE-g-MAH is added. The increase in oxygen permeability results from the presence of microvoids at the interface between the two phases during the process. Mechanical measurements showed that there exists an optimal amount of LDPE-g-MAH for maximizing both the tensile and tear properties in both the machine and transverse directions.     

Tensile Properties of Extruded Zein Sheets and Extrusion Blown Films

Zein‐based plastic sheets and films were formed by extrusion through a slit‐die or blowing head. Zein was plasticized with oleic acid and formed into a wet moldable mass (resin) to feed the extruders. Both single‐ and twin‐screw extruded sheets showed higher elongation at break, lower tensile strength, and lower Young's Modulus than non‐extruded samples. Stress‐strain plots for extruded samples showed evidence of plastic behavior. Observed necking of samples under tensile stress was also taken as evidence of plastic behavior. Small differences in tensile strength and elongation at break between single‐ and twin‐screw extruded samples were attributed to the effect of small voids observed by SEM in single‐screw extruded samples. Blown film extrusion was affected by feed moisture content and barrel temperatures. Optimal moisture content was determined at 14–15% while temperature at the three extruder zones was maintained at 20–25, 20–25, and 35 °C, respectively. Temperature at the blowing head was 45 °C. Film samples blown after either single‐ or twin‐screw extrusion showed similar tensile properties to those of slit die extruded samples.

Blown extrusion of zein film with single‐screw extruder.     

聚醚醚酮/多壁碳纳米管复合材料力学及阻燃性能研究

通过熔融共混法将聚醚醚酮（PEEK）与多壁碳纳米管(MWCNT)混合,利用模压法制备了MWCNT增强型PEEK复合材料,研究了MWCNT对PEEK性能的影响。结果表明,添加一定比例的MWCNT能够提高PEEK的力学和阻燃性能;当MWCNT含量为5%（质量分数,下同）时,PEEK的弯曲强度提高了53%;当MWCNT含量为1%时,锥形量热法测得的热释放速率峰值最低,燃烧性能指数值最大,热重分析显示初始分解温度较纯PEEK提高了13℃,表明MWCNT有效地提高了PEEK的阻燃和热稳定性能。     

Electromagnetic and Dynamic Mechanical Properties of Extruded Cobalt Ferrite-Polypropylene Composites

Cobalt ferrites of 0–45 wt% were incorporated in polypropylene by the extrusion technique. With increasing magnetic loading, the magnetizations were linearly increased according to the rule of mixture and the electrical permittivity was also proportional to the loading as described by Wagner's equation. The magnetic permeability may be increased but was reduced to minimal at high frequencies because of the substantial coercive field of cobalt ferrites after the extrusion. Without considerable adsorption of polymer matrix on magnetic fillers, the storage and loss modulus from 30 to 180°C of polypropylene were decreased by cobalt ferrites additions.     

衣架式机头动态挤出PP的力学性能

采用衣架式机头动态挤出PP试样,并对其进行拉伸强度、冲击强度和DSC测试,探讨振动频率和振幅对制品力学性能的影响。结果表明：振动的引入,有利于提高制品纵横两向的拉伸强度和冲击强度,并且存在最佳振动参数范围,当振幅0．1mm时,方向的力学性能改善效果最显著;而当频率为15Hz时．方向力学性能改善效果最为明显;制品熔点向高温迁移,吸热焓与结晶度也得到提高。     

塑料薄膜和片材厚度测量——机械测量法试验方法分析

介绍国际上通用的测量塑料薄膜和薄片厚度的试验方法：机械测量法、从测量点位置、实验精度和实验标准偏差三方面做更深一层的分析。     

PEEK/ZA8复合材料的制备及力学与摩擦学性能研究

采用模压成型法制备了锌铝合金(ZA8)填充聚醚醚酮(PEEK)复合材料,研究了ZA8含量和固体添加剂石墨和聚四氟乙烯(PTFE)对复合材料力学和摩擦学性能的影响。结果表明,复合材料的力学性能随着ZA8含量的增加呈先增加后降低的趋势,冲击强度和拉伸强度在ZA8含量为10%(质量分数,下同)时最大,分别为16.21 kJ/m^2和111.59 MPa,与纯PEEK相比分别增加了10.3%和3.9%;复合材料的摩擦因数随ZA8含量的增加呈持续下降的趋势,在ZA8含量为40%时最低为0.275,与纯PEEK相比降低了38.6%;磨损量呈先减小后增大的趋势,在ZA8含量为10%时最低为7.2 mg,比纯PEEK减小了43.3%;石墨和PTFE的添加能有效减小PEEK/ZA8复合材料的磨损量,其中加入10%的PTFE(未添加石墨)所制得的复合材料的摩擦学性能最好,摩擦因数为0.22、磨损量为4.3 mg,与纯PEEK相比分别降低了50.9%和66.1%。     

Mechanical Properties of Sputter-Deposited Titanium-Silicon-Carbon Films

The effect of SiC additions on the mechanical properties of TiC films was investigated. Ti-Si-C films with varying SiC content were deposited using dual-cathode radio-frequency magnetron sputtering. The nanoindentation hardness of these films increased with SiC content to a maximum of 20–22 GPa for films in the range of 15–30 at.% SiC. The elastic modulus was also measured, and the hardness to modulus ratio ( H / E ) increased with SiC content, indicating that hardness increases were due to microstructural effects. The residual stress was measured in several films, but was low in magnitude, indicating that hardness measurements were not influenced by residual stress. TEM examination of several films revealed that the SiC additions altered the film microstructure in a manner that could account for the observed hardness increases.     

Mechanical and Dynamic Mechanical Properties of Photocrosslinked Norbornene-Thiol Copolymer Films

A number of novel organic norbornene and norbornene siloxane polymer precursors have been synthesized as part of an on-going research project to produce a non-acrylate, UV-curable adhesive system. These precursors (monomers or oligomers) are di-, tri- and tetra-functional. The crosslinking agent is a multifunctional thiol.

The organic norbornene systems, formulated to stoichiometry, have been characterized using thermal, static and dynamic mechanical analysis. We have found that norbornene ester systems have a range of physical properties, with tensile moduli ranging from 820-2300 MPa (118-350 kpsi), tensile strengths of 17-61 MPa (2.5-8.8 kpsi) and elongations of 4-100%. Glass transition temperatures range from 30-71°C for samples cured at room temperature with a dose of 620 mJ/cm².

Norbornene siloxanes crosslinked with thiol siloxanes have been formulated with increasing levels of a high surface area reinforcing agent. Tensile properties of filled films show that filler loading to 30 wt% significantly increases peak stress and elongation to break above that of 25 wt% filler. The addition of filler did not appear to increase the T_g of the films in this series monotonically. Increased levels of filler were found to produce films with a broadened cold crystallization range and an increased melting temperature.     

Mechanical Properties of an Extruded Wood Plastic Composite: Analytical Modeling

Abstract

The focus of this study has been to predict wood plastic composite (WPC) properties using analytical models dedicated to reinforced composites and to define their limits. Experiment tests have been realized to characterize mechanical properties of a commercial WPC. On one hand, good compressive and three points bending performances were observed in agreement with application requirements for this decking product. On the other hand, lower tensile performance and failure appearances revealed a lack of interfacial bonding between wood fiber and matrix despite the presence of a coupling agent in the composite formulation.