Composition and Content of High-Molecular-Weight Glutenin Subunits and Their Effects on Wheat Quality

Sedimentation values, flour glutenin macropolymer (GMP) contents, composition and contents of high-molecular-weight (HMW) glutenin subunits (GS) of 233 flour samples were determined. Our data indicated that subunit 1 occurred more frequently at Glu-A1 , subunit pair 7 + 8 at Glu-B1 and 2 + 12 at Glu-D1. The significant relationships between Glu-1 quality score and total HMW glutenin content, sedimentation value and GMP content suggested that the composition of HMW-GS affects wheat quality strongly. Moreover, the total content of HMW-GS was correlated with certain quality parameters more significantly. Relationship between subunit 5 + 10 content and breadmaking quality was better than others, but 2 + 12, 7 + 8, 7 + 9 and 4 + 12 also correlated with certain quality parameters significantly. The contents of total HMW-glutenin, x-type subunits and y-type subunits related with sedimentation value, flour GMP content, and Glu-1 quality score more strongly than that of individual subunit or subunit pair. The flour GMP content, with excellent correlation to sedimentation value, total contents of HMW glutenin, x- and y-type subunits and many other quality parameters, could be an ideal indicator of breadmaking quality at earlier generations for breeding purpose for its simple procedure and small scale.

Attenuation of corneal neovascularization by topical low-molecular-weight heparin-taurocholate 7 without bleeding complication

AIM：To investigate the antiangiogenic effects and safety of topically administered low-molecular-weight heparintaurocholate 7（LHT7） on corneal neovascularization（CoNV）.METHODS：Twenty-four Sprague-Dawley rats were randomly distributed into four groups of six rats each.The central corneas were cauterized using a silver/potassium nitrate solution.From 2d after cauterization,12.5 mg/mL（low LHT7 group） or 25 mg/mL（high LHT7group） LHT7 was topically administered three times daily;12.5 mg/mL bevacizumab was topically administered as positive control（bevacizumab） group,with normal saline（NS） administered as negative control（NS group）.The corneas were digitally photographed to calculate the CoNV percentage from the neovascularized corneal area at 1 and 2wk.RESULTS：The 4 study groups did not have different CoNV percentages at 1wk after injury（P〉0.05）.However,the low LHT,high LHT,and bevacizumab groups had significantly lower CoNV percentages than the NS group at 2wk（all P〈0.05）.No significant differences in CoNV percentage were found among the low LHT,high LHT,and bevacizumab groups（all P〉0.05）.All groups except the NS group had lower CoNV percentages at 2wk postinjury than the levels observed at 1wk（all P〈0.05）.CONCLUSION：Topically-administered LHT7 inhibited CoNV without complication after chemical cauterization in the rat.

High-Molecular-Weight Glutenin Subunit Composition of Chinese Wheat Germplasm

The objective of the present study was to characterize the high molecular glutenin subunits （HMW-GS） composition and the presence of 1B/1R translocation in newly developed wheat （Triticum aestivum L.） germplasm, which have one or more traits that are useful in wheat improvement. Sodium dodecyl sulphate polyacrylamide-gel electrophoresis （SDS-PAGE） and acid polyacrylamide-gel electrophoresis （A-PAGE） were used to detect HMW-GS composition and the presence of 1B/1R wheat-rye （Secale cereale L.） chromosome translocation in the wheat germplasm. Bread-making quality scores of these lines were determined. A high level of variations in HMW-GS encoded by Glu-1 locus was observed. Sixteen major HMW-GS, with 30 combinations, were detected. The percentage of cultivars with more than two desirable subunits was 38.7%. Thirteen cultivars had bread-making quality scores of 10 in combination with one or two desirable agronomical traits, such as high-yield potential, dwarfing stem, resistance to diseases, and/or tolerance to abiotic stress. Sixty-eight （36.6%） cultivars possessed 1B/1R translocation. The newly developed germplasm with HMW-GS for good quality can be promising resources for improving bread-making quality of wheat.

Inhibitory effects and mechanisms of high molecular-weight phlorotannins from Sargassum thunbergii on ADP-induced platelet aggregation

We evaluated the effects of high molecular-weight phlorotannins from Sargassum thunbergii(STP) on ADP-induced platelet aggregation and arachidonic acid(AA) metabolism in New Zealand white rabbits and Wistar rats.The inhibition of STP on platelet aggregation was investigated using a turbidimetric method,and the levels of the terminal products of AA metabolism were measured using the corresponding kits for maleic dialdehyde(MDA),thromboxane B2(TXB2) and 6-keto-prostaglandin F1α(6-keto-PGF1α) by colorimetry and radioimmunoassay,as appropriate.We found that STP could inhibit ADP-induced platelet aggregation,and the inhibitory ratio was 91.50% at the STP concentration of 4.0 mg/mL.Furthermore,STP markedly affected AA metabolism by decreasing the synthesis of MDA(P<0.01) and increasing the synthesis of 6-keto-PGF1α,thus changing the plasma TXB2/6-keto-PGF1α balance when the platelets were activated(P<0.01).Therefore,STP altered AA metabolism and these findings partly revealed the molecular mechanism by which STP inhibits ADP-induced platelet aggregation.

Combined effect of Traditional Chinese Medicine decoction and low-molecular-weight heparin calcium on the postoperative deep venous thrombosis in patients with lower limb fracture

OBJECTIVE: To investigate the combined effect of Traditional Chinese Medicine(TCM) decoction and low-molecular-weight heparin calcium on deep vein thrombosis(DVT) induced by surgery in patients with lower limb fracture.METHODS: Totally 86 hospitalized patients with DVT after surgery of lower limb fracture between September 2012 and January 2015 were recruited and randomly divided into control group and observation group, 43 cases in each group. The patients in the control group were treated with subcutaneous injection of low-molecular-weight heparin calcium, and those in the observation group were additionally given Danshen Injection and TCM decoction. The differences between two groups in occurrence rate, medication time, therapeutic effects,recurrence rate of thrombosis, activated partial thromboplastin time(APTT), and prothrombin time(PT) were compared.RESULTS: The occurrence rate of DVT in observation group(4.65%, 2/43) was lower than that in control group(27.91%,12/43)(P<0.05). The medication time of observation group was(6.15±2.94) d, shorter than(9.76±3.12) d in the control group(P<0.05). In observation group, 2 cases of DVT were cured(2/2); in the control group, 9 cases presented therapeutic effects and the total effective rate was 75.00%(9/12). The improvement of APTT and PT in the observation group was better than that in the control group(P<0.05).CONCLUSION: Integrative TCM decoction plus low-molecularweight heparin calcium is superior to applicaton of low-molecularweight heparin calcium alone in reducing and treating DVT in the postoperative patients with lower limb fracture.

Utilizing Water Treatment Residuals for Phosphorus Removal:Batch Trials,Column Trials and Effects of Three Low-Molecular-Weight Organic Acids

Phosphorus( P) has been recognized as a major limited nutrient responsible for the eutrophication of surface waters. Water treatment residuals( WTRs) are safe by-products of water treatment plants and are cost-efficient adsorbents. In this study, batch experiments and column experiments based on WTRs were employed to study the characteristics of P adsorption and the effects of lowmolecular-weight organic acids( LMWOAs)( citric acid, oxalic acid,and tartaric acid) on P adsorption. Different models of adsorption were used to describe equilibrium and kinetic data. The adsorption data were fitted well by a pseudo-second order kinetic model. The adsorption process was determined to be controlled by three steps of diffusion mechanisms through the intra-particle model.The adsorption equilibrium was well described by the Langmuir,Freundlich,Redlich-Peterson,and Sips isotherm models. Batch and continuous flow experiments indicated that the LMWOAs exhibited inhibitory action,and as pH increased,the inhibitory action became weaker for all the three acids. The effect of LMWOAs concentration was not significant on inhibition. The effects of LMWOAs were closely related to reaction time.

The Safety and Feasibility of Low-Molecular-Weight He-parin Prophylaxis in Major Abdominal Surgery Combined with Neuraxial Anesthesia

Background: Global guidelines for venous thromboembolism (VTE) prophylaxis of patients undergoing major surgery are well established. However, their applicability and safety in patients receiving neuraxial anesthesia is unproven. We sought to evaluate the safety and feasibility of chemical VTE prophylaxis in a prospective group of patients undergoing major foregut procedures under a combination of epidural and general anesthesia. Methods: A prospective database of all patients undergoing major foregut surgery from 2004-2009 was maintained and analyzed. Epidural catheters were placed pre-operatively and used for post-operative analgesia for three days in all patients. Factors evaluated included age, ethnicity, sex, length of stay, duration of epidural placement, complications of epidural placement and post-operative management, and VTE events. A uniform protocol was followed regarding the timing of low-molecular-weight heparin (LMWH) administration with epidural catheter insertion/removal. Results: A total of 237 patients formed the study group. The mean age was 57 years (range, 19 - 88) among 121 (51.1%) women and 65 years (range, 20 - 95) among 116 (48.9%) men. One hundred and sixty-six patients were Caucasian (70%), 37 Black (15.6%), 15 Hispanic (6.3%), 12 Asian/Pacific (5.1%), and 7 other (3%). All epidural catheters were removed on the third post-operative day. There were a total of five VTE (2.1%) events postoperatively. No peri-operative or post-operative epidural catheter associated complications occurred. Conclusions: Concomitant epidural catheterization and LMWH anticoagulation is safe and feasible in major abdominal surgery patients, including those undergoing major hepatic resection. Guidelines for VTE prophylaxis and LMWH administration in the setting of neuraxial anesthesia are well established and applicable to this unique patient population.

Impact of Pharmaceutical Care on Self-Administration of Outpatient Low-Molecular-Weight Heparin Therapy

Outpatient subcutaneous (s.c.) therapies are becoming more and more common in the treatment of different diseases. The effectiveness of community-pharmacy-based interventions in preventing problems that arise during s.c. self-injections of low-molecular-weight heparins (LMWH) is unknown. Our objective was to provide a standard operating procedure (SOP) for community pharmacists and to compare pharmaceutical vs. standard care in both clinical and daily life settings. We hypothesized that: pharmaceutical care results in improved adherence, safety, and satisfaction, and in fewer complications;the interventions used are feasible in daily life;and the results achieved in clinical and daily life settings are comparable. In the clinical setting (randomized controlled trial), patients were recruited sequentially in hospital wards;in the daily life setting (quasi-experimental design with a comparison group), recruitment took place in community pharmacies by pharmacists and trained master students during their internship. Interventions were offered according to patient needs. Data were collected by means of a monitored self-injection at home and structured questionnaire-based telephone interviews at the beginning and the end of the LMWH treatment. The main outcome measures were: scores to assess patient’s skills;syringe count to assess adherence;and frequency, effectiveness, and patient’s assessment of received interventions. The results show a median age of the 139 patients of 54 years. Interventions resulted in improved application quality (p p = 0.03). Oral instructions were pivotal for improving patients’ application quality. We found no significant score differences between the intervention groups in the clinical and daily life settings. Patients’ baseline skills were high, with the lowest score being 0.86 (score range ?2.00 to +2.00). Adherence rate was high (95.8%). In conclusion, our SOP for pharmacist interventions was of good quality, adequate, appreciated, and feasible in daily life. Patients are capable of managing s.c. injection therapies if adequate assistance is provided.

Evaluation of a Dose-Monitoring Method for Prophylactic Anticoagulant Therapy with Low-Molecular-Weight Heparin

Objective: In the present study, we report on the results of our investigation of optimum dose monitoring using coagulation and fibrinolytic system indicators during obstetric prophylactic anticoagulant therapy with enoxaparin. Study Design: Of 103 cases of cesarean section performed at our hospital, 37 cases were selected for this study after obtain ing their consent for blood collection. Variables of the coagulation and fibrinolytic systems [anti-factor Xa activity, endogenous thrombin potential (ETP), prothrombin time (PT) or international normalized ratio (INR), activated partial thromboplastin time (APTT) and D-dimer levels] were determined. Results: In the 5-day administration group, the anti-factor Xa activitywas 0.0 U/ml on the postoperative day 1, increased to 0.05 U/ml ± 0.04 U/ml on the postoperative day 3, and mildly increased to 0.06 U/ml ± 0.05 U/ml on the postoperative day 5. On the other hand, the anti-factor Xa activity in the 3-day administration group was 0.0 U/ml on the postoperative day 1 (before enoxaparin administration), increased to 0.06 U/ml ± 0.05 U/ml on the postoperative day 3, and significantly decreased to 0.02 U/ml ± 0.03 U/ml on the postoperative day 5 (p = 0.003);thus, the pattern of change was significantly different from that in the 5-day administration group (p = 0.004). Enoxaparin administration did not result in any significant fluctuation of the ETP, and no significant difference was observed between the 5-day and 3-day administration groups. Conclusion: Enoxaparin administration was associated with increase of the anti-factor Xa activity, and prolonged administration led to more sustained increase of the activity.

Hot-Drawing of Ultrahigh-Molecular-Weight Polyethylene Gel Films

The three stages in the hot-drawing process of ultrahigh-molecular-weight polyethylene gel films can be detected by x-ray diffraction, infrared spectroscopy, birefringence and scanning electron microscopy. In the first stage of the drawing process, the lamellae in the gel films rotate and/or slip with the b-axis preferentially perpendicular to the drawing direction. With increased drawing, the c-axis of the lamellae become parallel to the stretching direction while unfolding of the chain begins, and the chains of the amorphous phase also orient along the drawing direction in the strain-chain domain. When the draw ratio is large enough, the lamellar structure is transformed into a fibrillar structure in a two-dimensional fashion.

引进美国小麦种质资源抗病性及品质性状鉴定

为了挖掘新的种质资源,本研究对引自美国的442份小麦材料对白粉病和条锈病的抗病性、蛋白含量以及高分子量麦谷蛋白(HMW-GS)亚基组成进行了鉴定分析。抗病性鉴定结果显示,153份材料抗白粉病,27份抗条锈病,6份兼抗两种病害。蛋白质含量达到GB/T 17892-1999《优质小麦强筋小麦》一等(粗蛋白质含量≥15.0%)的样品有143份。高分子量麦谷蛋白检测发现,供试材料共含18种HMW-GS亚基和100种不同亚基组合类型,其中N,7+9,5+10出现次数最多,优质亚基1、2*、7^(oe)、17+18、5+10的材料分别占总材料数的25.6%、5.2%、27.8%、7.7%和25.6%,含7^(oe),5+10亚基的有36份,含2*,5+10亚基的有1份,含2*,7^(oe)亚基的有7份。综合抗病性及品质分析结果显示,PI 17738等11份材料至少抗1种病害,且蛋白含量≥15.0%,湿面筋含量≥35.0%,同时含有稀有优质亚基。以上11份材料可作为我国优质、抗病小麦培育亲本,为我国小麦抗病和品质遗传改良提供优异基因源。

利伐沙班和低分子肝素在老年粗隆间骨折患者围手术期的应用效果分析

目的分析利伐沙班和低分子肝素在老年粗隆间骨折患者围手术期的应用效果。方法选取2020年6月至2021年10月于厦门大学附属中山医院就诊的老年粗隆间骨折围手术期患者130例为研究对象。按随机数字表法分为观察组和对照组,每组65例。对照组采用低分子肝素皮下注射预防血栓,观察组采用利伐沙班口服预防血栓。比较2组患者术前及术后2周的凝血指标,术后2周内下肢深静脉血栓形成(DVT)和肺栓塞的发生率,术中出血量、术后引流量及住院时间,术后1 d炎症相关指标。结果2组患者术前、术后2周组间和组内凝血相关指标差异均无统计学意义(均P>0.05)。术后观察组下肢DVT发生率显著低于对照组[4.6%(3/65)比15.4%(10/65)],差异有统计学意义(χ^(2)=4.188,P=0.041)。观察组与对照组术中出血量、术后引流量及住院时间差异均无统计学意义(均P>0.05)。术后1 d观察组降钙素原和C反应蛋白水平显著低于对照组[(0.17±0.02)μg/L比(0.22±0.01)μg/L、(20.2±2.3)mg/L比(23.9±3.6)mg/L],差异均有统计学意义(均P<0.001)。结论利伐沙班与低分子肝素在老年粗隆间骨折患者围手术期均有良好的抗凝效果及安全性,但利伐沙班预防术后下肢DVT发生的效果更显著且口服用药更方便。

乳腺癌患者外周中心静脉导管相关上肢深静脉血栓形成的抗凝治疗

目的总结分析乳腺癌患者发生外周中心静脉导管(PICC)相关上肢深静脉血栓(DVT)形成的诊治经验。方法收集2021年6月至2023年3月北京市海淀医院收治的发生PICC相关上肢DVT的134例乳腺癌患者的临床资料,根据抗凝治疗方案的不同将患者分为低分子肝素组(n=65)和利伐沙班组(n=69)。比较两组患者的乳腺癌专科信息和启动抗凝治疗后3个月的随访结果。结果两组患者的临床分期、肿瘤部位、手术情况、放疗情况比较,差异均无统计学意义(P﹥0.05)。治疗后3个月随访结果显示,两组患者的导管功能失用率、上肢DVT复发率、出血发生率比较,差异均无统计学意义(P﹥0.05)。两组患者均发生了轻微出血。治疗前,两组患者的D-二聚体水平比较,差异无统计学意义(P﹥0.05);治疗后4、12周,两组患者的D-二聚体水平均较本组治疗前下降,差异均有统计学意义(P﹤0.05),但两组患者的D-二聚体水平比较,差异均无统计学意义(P﹥0.05)。结论低分子肝素与利伐沙班治疗乳腺癌患者PICC相关上肢DVT的疗效与安全性相当,但利伐沙班可能更方便患者出院后使用。

不同分子质量水溶性壳聚糖在纸质文献加固中的应用研究

本研究采用乙酸酐制备了不同分子质量的水溶性壳聚糖(WSC-3、WSC-10、WSC-20、WSC-30和WSC-60)并用作修复液,探究其对纸质文献加固及耐老化的效果。结果表明,与未经加固处理的纸张(原纸)相比,采用不同分子质量的水溶性壳聚糖加固处理后,纸张的强度性能有所提升,白度下降幅度较小,色差变化较小,pH值和碱储量均增加。纸张加速老化后,与原纸相比,加固处理后纸张的强度性能下降幅度明显较小,其中WSC-30加固处理后纸张的抗张指数、撕裂指数、零距抗张强度的保留率分别提升了9.7、7.4、4.5个百分点,外观形貌、白度和色差等相差较小。

低分子肝素钠联合保胎灵在复发性流产患者中的应用价值及对CRP与HO-1的影响

目的探讨低分子肝素钠联合保胎灵在复发性流产患者中的应用价值及对C-反应蛋白(CRP)与血红素加氧酶1(HO-1)的影响。方法选取2020年3月至2022年4月在我院接受治疗的108例复发性流产(RSA)患者作为研究对象,采用随机表法,将患者随机分为联合组(n=54)和传统组(n=54),传统组患者予以低分子肝素(LMWH);联合组患者加用保胎灵。比较两组患者激素水平、凝血功能、细胞相关因子水平、血清水平的变化、妊娠结局及其并发症的发生情况。结果治疗后,两组β-人绒毛膜促性腺激素(β-HCG)、雌二醇(E 2)和孕酮(P)、活化部分凝血酶原时间(APTT)、凝血酶原时间(PT)、转化生长因子-β(TGF-β)和白细胞介素-10(IL-10)、HO-1均升高,且联合组高于传统组(P<0.05);两组纤溶酶原激活抑制剂1(PAI-1)、白细胞介素-17(IL-17)、CRP均下降,且联合组低于传统组;联合组流产率显著低于传统组,活产率则明显高于传统组(P<0.05)。两组患者的足月产率比较差异无统计学意义(P>0.05)。联合组分娩周数显著长于传统组(P<0.05);两组患者妊娠并发症比较差异无统计学意义(P>0.05)。结论LMWH联合保胎灵能有效改善RSA患者妊娠期孕激素水平及凝血功能,提升保胎成功率改善妊娠结局,同时可调节细胞平衡,且对并发症无显著影响。

不同分子量蛋白质对小麦品质及馒头加工品质的影响

为了解不同分子量蛋白质对小麦品质及馒头加工品质的影响,以石优17、石4366、石麦15等30个石麦系列小麦品种为材料,对不同分子量蛋白质相对含量、品质特性以及馒头加工品质进行了检测与分析。结果表明,UPP(SDS不溶性蛋白大聚体)、LPP(大分子量聚合体蛋白)、LMP(大分子量单体蛋白)的相对含量及LPP/LMP比值与小麦粉的大多数品质指标存在显著或极显著相关性;不同分子量蛋白质相对含量较蛋白质含量更能反映小麦品质;UPP相对含量可作为小麦粉品质性状及面筋特性的预测和评价指标。蛋白质含量显著影响馒头的粘着性,UPP、LPP、LMP相对含量及LPP/LMP比值主要影响馒头质构特性中的硬度、胶着性及咀嚼度。UPP相对含量可以作为评估小麦粉是否适宜馒头加工的重要指标。

7^(OE)+8^(*)亚基对东北强筋小麦品种品质性状影响研究

小麦品质改良是东北春麦区强筋小麦育种的主要目标之一。Glu-B1位点7^(OE)+8^(*)亚基为超强筋小麦品种必备基因。为了明确该亚基在东北春麦区强筋小麦遗传背景下的品质遗传效应,本研究利用分子标记和选择回交相结合的手段,将7^(OE)+8^(*)亚基定向导入到强筋小麦品种龙麦26和龙麦35(Glu-B1位点均为7+9亚基)的遗传背景之中,对BC_(5)F_(1)、BC_(6)F_(1)群体和自交BC6F2鉴定获得的纯合品系进行7^(OE)+8^(*)亚基遗传效应评价。结果表明,在强筋小麦品种龙麦26(7+9)和龙麦35(7+9)遗传背景下转入7^(OE)+8^(*)亚基后,其干面筋、面筋指数、形成时间、稳定时间、断裂时间、拉伸面积、延伸性和最大抗延阻力等品质指标3年平均分别提高1.3%(P=0.82)和1.8%(P=0.49)、6.6%(P=0.59)和4.7%(P=0.37)、55.0%(P=0.24)和35.8%(P=0.56)、44.5%(P=0.43)和32.8%(P=0.73)、41.4%(P=0.31)和30.0%(P=0.66)、28.0%(P=0.05)和23.4%(P=0.37)、6.5%(P=0.47)和5.8%(P=0.42)、19.5%(P=0.31)和18.0%(P=0.38);Zeleny沉降值2年平均分别提高6.8%和11.4%。以上结果表明,在2个强筋小麦品种遗传背景下,Glu-B1位点转入7^(OE)+8^(*)亚基较7+9亚基对各项品质指标改良均存在正向效应,但提高幅度存在差异,对形成时间、稳定时间、断裂时间、最大抗延阻力、拉伸面积等衡量面筋质量的指标提高幅度更大,表明该亚基对面筋质量改良效应显著。综上所述,7^(OE)+8^(*)亚基可作为东北春麦区强筋小麦遗传背景下品质性状进一步改良的优选基因,为超强筋小麦育种的重要基因资源。

老年冠心病患者低分子肝素皮下注射后按压与出血发生率的效应研究

目的探讨老年冠心病患者皮下注射低分子肝素后是否按压与皮下出血发生率的相关性。方法纳入2019年1月至2021年12月在南京医科大学附属南京医院行经皮冠状动脉介入治疗(percutaneous coronary intervention,PCI)后使用低分子肝素皮下注射的老年冠心病患者131例作为研究对象,按照注射后是否按压分为观察组67例和对照组64例。皮下注射低分子肝素的流程均按照本院已纳入规范的“低分子肝素皮下注射法护理质量督查标准”执行,其中观察组要求注射完毕后按压穿刺点3~5 min,力度以皮肤下陷1cm为准,比较两组患者皮下出血的发生率。结果观察组皮下瘀斑发生率(9.0%)与对照组(7.8%)比较差异无统计学意义(P>0.05),观察组皮下硬结发生率(4.5%)与对照组(1.6%)比较差异亦无统计学意义(P>0.05)。患者的年龄、性别、腹围以及体质量指数(body mass index,BMI)与注射低分子肝素后发生皮下出血没有显著相关性(P>0.05),而腹部皮脂厚度与皮下出血存在显著相关性(P<0.05),是预测注射低分子肝素后发生皮下出血的独立预测因子。结论老年冠心病患者低分子肝素皮下注射后按压与出血发生率无相关性,无需按压。患者的腹部皮脂厚度是预测注射低分子肝素后发生皮下出血的独立预测因子,应通过规范操作来避免皮下出血的发生。

离子改性对宽分子量分布聚丙烯黏弹性能影响

宽分子量分布聚丙烯(BMWDPP)PP1经离子改性剂处理后得到PP4。通过凝胶渗透色谱(GPC)与平板旋转流变、拉伸流变和熔体强度测试研究了PP1和PP4的分子结构与流变性能的变化。离子改性过程中的自由基诱发PP降解会降低BMWDPP的分子量大小及多分散性;虽未形成真正的长支链结构,但由于接枝在PP分子链上的金属盐之间靠离子相互作用造成“类长支链”效果,PP4可产生拉伸应变硬化现象;PP4因大分子量组分的降解削弱缠结及小分子量组分的降解增强塑化,导致黏弹性低于PP1。拉伸应变硬化对熔体强度增高的影响强于分子量降低对熔体强度削弱的影响,故PP4的熔体强度在不同的温度下皆高于PP1;在低温下呈现线形大分子量分子链PP特点,而在高温下呈现长支链PP特点。

硅酮粉改性超高分子量聚乙烯及其熔体纺丝加工性能

针对超高分子量聚乙烯(PE-UHMW)熔体加工性能差的问题,应用硅酮粉,采用熔融共混方法对PE-UHMW进行改性,以提高其熔体加工时的流动性。通过扫描电子显微镜与能量色散谱(EDS)表征了硅酮粉在PE-UHMW中的分布,并采用熔体速率测试、旋转流变测试,分析了硅酮粉含量对PE-UHMW熔体流动速率与流变性能的影响。对改性后的PE-UHMW采用熔体纺丝法制备了PE-UHMW单丝,并进行了拉伸强度测试。实验结果表明,随着硅酮粉的增加,其分散性逐渐变差,PE-UHMW熔体流动速率随硅酮粉含量先增加后降低,当硅酮粉质量分数达到4%,其熔体流动速率最高,复数黏度与储能模量最低,5%质量分数的硅酮粉在PE-UHMW基体中团聚较明显,改性后的PE-UHMW熔体流动性降低。熔体纺丝实验结果表明改性后的PE-UHMW可以通过普通单螺杆挤出机熔融挤出初生丝,经超倍热拉伸可以制备高强度单丝。当拉伸倍率为36时,质量分数3%的硅酮粉改性PE-UHMW单丝拉伸强度最高,可达1565MPa。因此综合考虑加工性能与单丝强度,采用质量分数3%的硅酮粉改性PE-UHMW较合适。