水蒸汽在软包装薄膜中的传递行为

在不同温度和相对湿度(RH)条件下,对代表不同亲水性能的三种常见软包装膜——聚乙烯(PE)膜、聚乙烯醇(PVA)膜、大豆分离蛋白(SPI)膜的水蒸汽透过率(WVTR)进行了一系列测定,并在此基础上计算了其水蒸汽透过系数(WVP)。实验结果表明,随温度升高,三种膜的WVTR均呈指数上升趋势。湿度对三种膜WVTR的影响表现出一定差异,对PVA膜和SPI膜,其WVTR与RH之间满足指数方程y=A*exp(x/B)+C,而PE膜的WVTR与RH间表现为线性关系。PVA膜和SPI膜的WVP受湿度影响大于温度对其影响,相反,PE膜的WVP受温度影响程度显著于环境湿度。     

针孔现象对聚对苯二甲酸乙二醇酯薄膜透湿性能影响的研究

采用物理方式模拟聚对苯二甲酸乙二醇酯(PET)薄膜的"针孔现象",然后对其进行透湿性能测试,研究3种温湿度条件下针孔个数、温度、针孔有无毛边对PET薄膜渗透性能的影响规律,基于最小二乘法探讨了针孔率与水蒸汽透过率之间的经验关系。结果表明:在不同温湿度条件下,PET薄膜水蒸汽透过率均随着针孔个数的增加呈线性趋势上升,在38℃、相对湿度90%的高温高湿状态下,针孔个数对薄膜水蒸汽透过率的影响最大;针孔无毛边时的薄膜水蒸汽透过率明显大于有毛边时的水蒸汽透过率,且随着针孔数量的增加,针孔无毛边相对有毛边时的水蒸汽透过率增长率逐渐增大;在38℃、相对湿度90%的高温高湿度条件下针孔率与薄膜水蒸汽透过率之间为二次函数关系,另外两种温湿度条件下为一次线性比例关系。     

湿度对聚乙烯醇膜阻隔性能的影响

采用美国Mocon公司的3/33MG透湿仪和2/21MH透氧仪在不同相对湿度(RH)下对聚乙烯醇(PVA)膜的水蒸汽透过率(WVTR)、氧气透过率(OTR)进行了一系列测量,并在此基础上分析了RH变化对PVA膜阻隔性能的影响规律。实验结果表明,湿度越大,聚乙烯醇膜的WVTR、OTR越大,且聚乙烯醇膜的氧气和湿气透过率与相对湿度间存在指数关系。     

流延聚丙烯薄膜生产工艺及国内现状

聚丙烯薄膜按制法、性能和不同用途可分为流延聚丙烯(CPP)薄膜、吹胀聚丙烯(IPP)薄膜和双向拉伸聚丙烯(BOPP)薄膜三种。聚丙烯薄膜占世界PP总消费量的20％，是仅次于注塑、纤维(包括扁丝)的第三大应用产品，我国PP薄膜占PP消费结构份额相对低，仅为10％左右。     

蒙脱土与MFC涂层对聚丙烯膜阻隔性能的影响

目的为了提高聚丙烯薄膜的阻隔性,利用涂布的方法研究蒙脱土与微纤化纤维素(MFC)含量对涂布膜阻隔性能的影响。方法以蒙脱土和MFC为主要原料,加入胶黏剂、增稠剂、分散剂制备成涂料,并涂布在双向拉伸聚丙烯薄膜上,以薄膜的氧气透过率、水蒸气透过率、红外光谱分析、XRD分析和热稳定性分析作为评判标准,对薄膜性能进行表征与分析。结果在添加的蒙脱土质量分数为2%,MFC质量分数为0.5%时,双组分涂布膜的氧气透过系数达到最低,较聚丙烯薄膜氧气透过系数下降了97%,水蒸气透过系数在添加蒙脱土质量分数为2%,MFC质量分数为0.3%时达到最低,较聚丙烯薄膜水蒸气透过系数下降了22%,XRD显示当MFC质量分数为0.5%时,插层结构最优,通过热稳定性分析得出,双组分涂布膜在蒙脱土质量分数为2%,MFC质量分数为0.5%时热稳定性最好。结论通过综合分析得出,涂布蒙脱土与MFC双组分涂层可有效提高聚丙烯薄膜的阻隔性能。     

拉伸速度和制样方式对聚苯乙烯和聚丙烯拉伸性能的影响

研究了拉伸速度及制样方式对聚苯乙烯(PP)和聚丙烯(PS)材料的拉伸强度和断后伸长率的影响。结果表明:随着拉伸速度的增大,两种材料的拉伸强度均有所增加,而断后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后伸长率都明显高于压制成型试样,PP注塑成型试样的断后伸长率比压制成型试样的增加了69%,而拉伸强度几乎没有改变。     

聚丙烯流延基膜的硬弹性结构及拉伸成孔性

在不同流延条件下制备聚丙烯(PP)流延基膜,并对基膜施加拉伸使其形成微孔,通过差示扫描量热测试和傅立叶变换红外光谱表征基膜的结晶度、片晶厚度和晶区的取向程度等硬弹性结构参数,使用扫描电镜观察微孔膜的孔形态并测定了微孔膜的透气率,研究了流延工艺条件与基膜的硬弹性结构及拉伸成孔性之间的关系。结果表明,流延辊温度主要影响基膜结晶度和片晶厚度,牵伸比主要影响晶区取向程度。基膜硬弹性结构越完善,弹性回复率越大,拉伸后形成的微孔数量越多,孔形态和孔结构更加均匀,透气率增大。     

聚丙烯流延基膜的硬弹性结构及拉伸成孔性EI北大核心CSCD

在不同流延条件下制备聚丙烯(PP)流延基膜,并对基膜施加拉伸使其形成微孔,通过差示扫描量热测试和傅立叶变换红外光谱表征基膜的结晶度、片晶厚度和晶区的取向程度等硬弹性结构参数,使用扫描电镜观察微孔膜的孔形态并测定了微孔膜的透气率,研究了流延工艺条件与基膜的硬弹性结构及拉伸成孔性之间的关系。结果表明,流延辊温度主要影响基膜结晶度和片晶厚度,牵伸比主要影响晶区取向程度。基膜硬弹性结构越完善,弹性回复率越大,拉伸后形成的微孔数量越多,孔形态和孔结构更加均匀,透气率增大。     

云母/聚丙烯共混物熔体的拉伸流变性能

采用双料筒毛细管流变仪和Haul-off牵伸设备, 研究了云母(Mica)/聚丙烯(PP)共混物在拉伸流场中的流变性能。结果表明: Mica/PP共混物熔体拉伸流动属于拉伸变稀型, 随着云母含量的增加, 熔体的表观拉伸黏度逐渐增大。熔体的拉伸应力和表观拉伸黏度均随温度的升高而下降。随着拉伸应变速率的提高, 熔体的拉伸应力增大, 表观拉伸黏度减小, 熔体拉伸流动活化能呈下降趋势。云母微粒的加入使聚丙烯熔体的拉伸模量明显增大, 但随着拉伸速度的提高, 共混熔体的拉伸模量下降显著。为了提高Mica/PP共混物的纺丝稳定性, 应严格控制好拉伸速度和加工温度。     

TIPS法iPP中空纤维膜的拉伸性能研究

通过熔融共混等规聚丙烯(iPP)/邻苯二甲酸二丁酯(DBP)/邻苯二甲酸二辛酯(DOP)体系,采用热致相分离法(TIPS)制备iPP中空纤维膜,且在不同的拉伸温度及拉伸比下对中空纤维膜进行拉伸研究.对膜结构与透过性能进行了表征.采用环境扫描电子显微镜(SEM)对膜的内、外表面以及截面结构进行观测,发现拉伸后膜外表面的皮层以及膜结构得到有效改善.使用电子式万能试验机对中空纤维膜的拉伸强度进行了测试.随着拉伸温度和拉伸比的增加,膜的孔隙率、纯水通量以及拉伸强度均呈现先增大后减小的趋势.膜的孔隙率最大可提高35.3％,纯水通量提高了286.9％,拉伸强度可提高至6.86 MPa.nano-SiO2(纳米SiO2)添加的杂化膜经过拉伸后,孔隙率增大了46.8％,纯水通量提高了416.1％,拉伸强度提高了181.9％.研究表明:通过对iPP中空纤维膜进行拉伸处理,可以优化膜结构,并改善了膜表面皮层以及透过性能.     

聚丙烯亲水性微孔膜的制备及在锂电池中的应用

以聚丙烯接枝马来酸酐(PP-g-MAH)为改性剂与聚丙烯熔融共混,通过单向拉伸工艺制备亲水性聚丙烯微孔膜。使用差示扫描量热仪和红外光谱表征流延基膜的取向片晶结构,使用压汞仪和扫描电镜表征微孔膜的孔结构,使用Gurley值、水接触角和水蒸气透过率表征微孔膜的透过性和亲水性,将微孔膜组装成电池并测定电池的性能,研究PPg-MAH含量对微孔膜孔结构、亲水性、透过率及电池性能的影响。结果表明,PP-g-MAH共混含量为2.5%的微孔膜孔隙率和透气性得到提升,进一步增加PP-g-MAH含量会导致微孔膜孔结构变差,透过性能下降。微孔膜表面亲水性随PP-g-MAH含量增加持续改善,水蒸气透过率在PP-g-MAH含量为5%时达到最大值,但由于微孔膜孔结构在较高PPg-MAH含量下受到破坏,使得高PP-g-MAH含量下微孔膜水蒸气透过率下降。PP-g-MAH含量为2.5%和5%的微孔膜由于具有较好的孔结构和一定的电解液浸润性,使得锂电池的电荷转移电阻较低,首次充放电比容量较高。     

Blends of PP/PE co‐octene for modified atmosphere packaging applications

The aim of this work was to obtain films of polypropylene (PP)/polyethylene co‐octene (POE) blends and study the influence of their composition and mixing conditions on final morphology and ultimate properties (thermal, mechanical, oxygen and water vapour transmission rates). Scanning electron microscopy showed segregation of POE domains in the PP matrix. Thermal analysis indicated that the addition of POE modified neither the melting temperature nor the crystallinity of PP in the pressed films. It was found that permeabilities of films were mainly related to POE content rather than morphological features. For the maximum POE concentration used (40%), the oxygen permeability increased up to ∼100% from that of neat PP. A similar trend was found for water vapour permeability. Rigidity of blends dropped significantly with the addition of POE although their ductility slightly increased when compared to pure PP. No significant effect of blend preparation conditions on these properties was found. Mechanical and permeability characteristics of films make them very attractive to be used for MAP of fresh produce such as apple, blueberry and mushroom. Copyright © 2011 John Wiley & Sons, Ltd.     

PCL / 纸板复合膜的包装特性及回收工艺研究

为了提高纸板的力学性能和水蒸气阻隔性,采用热压法制备了聚己内酯(PCL)/纸板双层复合膜。分别使用质构仪、动态力学分析仪、透湿仪对材料的力学性能、动态热力学性能以及阻隔性能进行了评价,并对PCL的热封性能和纸板的回收工艺进行了评估。研究表明,与PCL复合后,纸板的拉伸强度提高了约3倍,弹性模量提高了约5倍,阻湿性也显著提高;PCL的复合量和热封温度对材料的热封强度影响较大;纸板回收速度快,平均回收率可达到99%。     

几种食品包装用塑料膜阻透性能比较

目的研究不同厚度、不同材质的食品包装用塑料膜透氧量、透湿量的变化情况,为食品包装在阻隔性方面的选材提供依据和指导。方法采用压差法和杯式法分别测试塑料膜的透氧量和透湿量。结果单层塑料膜随厚度的增加,透氧量和透湿量均减小,阻隔性能变好。相同厚度的PE,PET,BOPP,PA这4种单层塑料膜中,PA的透氧量最小,PE的透氧量最大,BOPP的透湿量最小,PA的透湿量最大。复合膜厚度增加,其透氧量、透湿量均减小,但减小幅度逐渐变小。塑塑复合膜外层材料厚度不变时,透氧量、透湿量随总厚度变化不太明显,EVOH塑料复合膜的透氧量值和透湿量值较小,通常在5以下,铝箔塑料复合膜的透氧量值和透湿量值均小于1。结论单层塑料膜PA的氧气阻隔性最好,PE的氧气阻隔性最差,BOPP的水蒸气阻隔性最好,PA的水蒸气阻隔性最差。复合膜中,塑塑复合膜的阻隔性主要取决于外层材料,铝塑复合膜的阻隔性最好,含高阻隔材料EVOH的塑料复合膜的阻隔性比普通塑塑复合膜好,其阻隔性可与铝塑复合膜媲美。     

Effects of glycerol and sorbitol on optical,mechanical, and gas barrier properties of potato peel‐based films

Potato peel is a by‐product of potato‐based food production and seen as a zero‐ or negative‐value waste of which millions of tons are produced every year. Previous studies showed that potato peel is a potential material for film development when plasticized with 10% to 50% glycerol (w/w potato peel). To further investigate potato peel as a film‐forming material, potato peel‐based films containing the plasticizer sorbitol were prepared and investigated on their physicochemical properties in addition to films containing glycerol. Due to sufficient producibility and handling of casted films in preliminary trials, potato peel‐based films containing 50%, 60%, or 70% glycerol (w/w potato peel) and films containing 90%, 100%, or 110% sorbitol (w/w potato peel) were prepared in this study. Generally, with increasing plasticizer concentration, water vapor and oxygen permeability of the films increased. Films containing glycerol showed higher water vapor and oxygen permeabilities than films containing sorbitol. Young's modulus, tensile strength, and elongation at break decreased with increasing sorbitol concentration, whereas no significant effect of plasticizer content on elongation at break was shown in films containing glycerol. Due to crystallization of films containing sorbitol as a plasticizer, potato peel‐based films containing 50% glycerol (w/w) were identified as the most promising films, characterized by a water vapor transmission rate of 268 g 100 μm m^?2 d^?1 and an oxygen permeability of 4 cm³ 100 μm m^?2 d^?1 bar^?1. Therefore, potato peel‐based cast films in this study showed comparable tensile properties with those of potato starch‐based films, comparable water vapor barrier with those of whey protein‐based films, and comparable oxygen barrier with those of polyamide films.     

Development of a mathematical model for the effect of temperature and relative humidity on the water vapour permeability of plastic films

The water vapour permeability constants of three flexible films (LDPE, PET and a laminate of both films) were determined at 20, 30 and 40 °C and from 55 to 90% relative humidities. The relationship between permeability and temperature followed the Arrhenius model for the three films. The relative humidity also influenced the permeability of the films. A mathematical model describing permeance (P/X - the permeability of laminates or films) as a function of external relative humidity and temperature was developed. The model can be used to predict the permeance of the three films at different temperatures and relative humidities.     

水汽透过量测量不确定度评定

本文简单介绍了水汽透过率测定仪的工作原理,参考GB/T 1037-88《塑料薄膜和片材透水蒸气性试验方法 -杯式法》,[1]利用水汽透过率测定仪对水汽透过量进行测量,并以此建立了测量模型,对水汽透过量的测得值进行了不确定度分析和评定。     

激光化学气相沉积快速生长高取向TiN_x薄膜的研究

采用激光化学气相沉积（LCVD）技术在氧化铝衬底上制备了高取向的TiN_x薄膜,重点研究了激光功率（PL）、衬底预热温度（T_pre）和沉积总压力（P_tot）对薄膜取向和沉积速率的影响,采用X射线衍射（XRD）、俄歇能谱（AES）和场发射扫描电镜（FESEM）对薄膜组成和结构进行了表征.结果表明：所得到的TiN_x薄膜成分均匀,其取向与衬底预热温度有关,随着预热温度的升高,TiNx薄膜的取向由（111）变为（200）,薄膜的取向与其微观结构一致.TiN_x薄膜的沉积速率随着激光功率升高而增大,在P_L=100W时,达到最大值90μm/h（沉积面积为300mm²）,显著高于采用其它方法制备的TiN_x薄膜.     

增塑剂对马铃薯淀粉基复合膜物理机械性能的影响

以马铃薯淀粉、普鲁兰多糖、明胶为成膜物质,氯化钙为交联剂,甘油、山梨醇、聚乙二醇为增塑剂,采用流延法制备了马铃薯淀粉基复合膜,研究了3种增塑剂对复合膜物理机械性能的影响。结果表明:复合膜的抗拉强度和弹性模量均随增塑剂含量的增加而显著减小,断裂伸长率随甘油和山梨醇含量的增加而显著增加,聚乙二醇对其影响不显著;复合膜的水蒸气透过率和水溶性均随增塑剂含量的增加而增加;聚乙二醇能够显著降低复合膜的透光率。     

Heteroepitaxial Growth and Characterization of 3C-SiC Films on Si Substrates Using LPVCVD

3C-SiC films have been deposited on Si (111) substrates by the low-pressure vertical chemical vapor deposition (LPVCVD) with gas mixtures of SiH4, C3Hg and H2- The growth mechanism of SiC films can be obtained through the observations using field emission scanning electron microscope (FESEM). It is found that the growth process varies from surface control to diffusion control when the deposition temperature increases from 1270 to 1350℃. The X-ray diffraction (XRD) patterns show that the SiC films have good crystallinity and strong preferred orientation. The results of the high resolution transmission electron microscopy (HRTEM) image and the transmission electron diffraction (TED) pattern indicate a peculiar superlattice structure of the film. The values of the binding energy in the high resolution X-ray photoelectron spectra (XPS) further confirm the formation of SiC.