热收缩包装薄膜的最新发展

热收缩包装是一种新颖和有效的包装方法,发展时间较短但发展前景很好,最早应用于食品包装方面,近来在其他包装方面亦取得了长足的发展。近来有热收缩包装来代替纸箱包装的动向。 热收缩薄膜的种类较多,有聚乙烯、聚丙烯、聚氯乙烯、聚偏二氯乙烯、聚酯、尼龙等热收缩薄膜。 这些热收缩薄膜一般为单组分结构,收缩包装后能紧紧贴合在被包装物表面,没有绉纹,具有光泽。而随着社会经济和生活水平的提高,以及生产技术的发展,对热收缩包装提出了更高更新的要求,人们也能研究和生产出各种具有特殊功能的热收缩薄膜。下面介绍几种最新研究开发的热收缩特种薄膜。 1.具有凹凸绉纹的热收缩薄膜     

POF热收缩薄膜的包装应用性能研究

以线性低密度聚乙烯(LLDPE)作为中间层,共聚丙烯(PP)作为内、外层,采用3层共挤的方法制成的POF复合热收缩薄膜,可弥补单一材料制成的热收缩薄膜所不能满足的收缩包装需要.研究了POF热收缩薄膜的包装应用性能,包括在不同温度下的热收缩率、薄膜的厚度随收缩温度的变化、不同热收缩温度处理后的拉伸性能和透湿性能.这些性能的研究为POF的热收缩包装应用,提供了有价值的参考依据.     

有源矩阵液晶显示玻璃基板的热收缩研究

对于有左阵液晶显示玻璃基板，热尺寸收缩量是一个重要参数，本研究用模拟热循环处理工艺过程中的热收缩量来衡量。介绍了测定热收缩量的原理和方法；讨论了影响玻璃热收缩的主要因素。热收缩随着玻璃基板处理的升高而增大；退火后玻璃的上缩量小于未退火玻璃；基板的热收缩玻璃应变点的增高而降低。     

低能电子束辐射交联改性PP/LLDPE五层共挤POF热收缩膜的性能

通过低能电子束辐射改性聚丙烯(PP)/线型低密度聚乙烯(LLDPE)五层共挤聚烯烃(POF)热收缩膜,制备耐温性强、收缩温度窗口宽的POF交联热收缩膜。文中研究了辐照气氛和吸收剂量对POF热收缩膜结构、力学性能和热收缩性能的影响。结果表明,在氮气和空气气氛辐照后,POF热收缩膜的结构、力学性能和热收缩性能未有明显差别。POF热收缩膜交联度和耐温性均随着吸收剂量增加而增加。POF热收缩膜的断裂伸长率随吸收剂量增加无明显变化;拉伸强度随吸收剂量增加先增加再降低。低能电子束辐照交联改善了POF热收缩膜低温收缩性能,增宽了热收缩温度窗口。     

低能电子束辐射交联改性PP/LLDPE五层共挤POF热收缩膜的性能EI北大核心CSCD

通过低能电子束辐射改性聚丙烯(PP)/线型低密度聚乙烯(LLDPE)五层共挤聚烯烃(POF)热收缩膜,制备耐温性强、收缩温度窗口宽的POF交联热收缩膜。文中研究了辐照气氛和吸收剂量对POF热收缩膜结构、力学性能和热收缩性能的影响。结果表明,在氮气和空气气氛辐照后,POF热收缩膜的结构、力学性能和热收缩性能未有明显差别。POF热收缩膜交联度和耐温性均随着吸收剂量增加而增加。POF热收缩膜的断裂伸长率随吸收剂量增加无明显变化;拉伸强度随吸收剂量增加先增加再降低。低能电子束辐照交联改善了POF热收缩膜低温收缩性能,增宽了热收缩温度窗口。     

热收缩试验仪校准方法的研究

热收缩试验仪是当今检验部门以及化工产品生产企业广泛使用的试验仪器之一。它广泛应用于化工、药品、电子仪表等行业。为了确保热收缩试验仪的量值准确可靠,为该仪器提供校准的依据,对热收缩试验仪的校准方法进行了研究,并完成了《热收缩试验仪》广西地方校准规范的起草准备工作。     

BOPP薄膜热收缩性能的时效性

研究了生产时间和存储时间对BOPP薄膜热收缩率和热收缩率稳定性的影响。结果表明:夏季温度高,薄膜的纵向热收缩率低,而且衰减速度快,冬季温度低,薄膜的纵向热收缩率高,而且衰减慢;夏季和冬季的横向热收缩率差异不大,而且衰减也比较缓和。分析了氢化石油树脂、拉伸比、温度等配方和工艺因素对薄膜热收缩率衰减的影响,提出了一些可行的改进措施。     

PVA热收缩包装薄膜的研究与应用

PVA热收缩薄膜具有优异的水溶性和生物降解性能,目前其生产方法主要有流涎法(湿法)和挤出吹塑法(干法),其热收缩工艺可分为一步法和两步法。PVA薄膜通过增塑改性可以降低结晶度,从而增加热收缩性能。其中,增塑改性工艺中的主要影响因素为增塑剂,拉伸工艺中的主要影响因素是拉伸温度和拉伸倍数,骤冷工艺中的主要影响因素是冷却温度及受冷均匀,收缩工艺中的主要影响因素是热收缩温度。PVA热收缩薄膜的市场应用空间较大,其研究方向主要为新型绿色可降解热收缩包装薄膜。     

新型潜艇作战系统TMA功能设

文章在新型潜艇全综合、分布式作战系统的体系结构下,以声纳信息作为主要信息源,综述了纯方位TMA、多信息融合TMA、方位-多普勒TMA、噪声能量-方位联合估距、与匹配场声源定位相结合等几种实现TMA的方法,在此基础上对TMA功能提出了新设想,初步提出了一种TMA的功能设计。该功能设计从作战系统的角度出发开发TMA功能,充分利用了多传感器获得的信息,以及人的主观判断,增强了TMA的能力,使它能够更好地为指挥员战术决策服务,为武器的发射控制提供更加精确的目标运动要素解算结果。与通常的TMA设计相比,该项设计能够识别目标机动,增加了人机交互功能,并设计了便于观看TMA结果、监视目标机动和执行交互式跟踪改进的TMA显示画面。     

聚乳酸单轴拉伸膜的包装特性研究

目的研究了不同拉伸比的PLLA薄膜的热学性能、阻隔性能和热收缩性能。方法采用双螺杆挤流延试验机单轴拉伸制备了不同拉伸比的PLLA热收缩膜和定向拉伸膜,采用差示扫描量热分析仪(DSC)、透湿仪和透氧仪对不同拉伸比的PLLA薄膜的热学性能和阻隔性能进行了评估,并对PLLA膜的热收缩性进行了测定。结果热收缩膜的拉伸比由1增大到6.5时,PLLA的结晶度由0.2%增加到41.8%,结晶速率明显提高,阻隔性得到了一定的改善。随着拉伸比例的增大,热收缩率随之增大。定向拉伸膜的结晶度得到了大幅度提高,其阻隔性也得到了改善,但不呈现热收缩性。结论通过单轴拉伸可以有效地提高PLLA薄膜的结晶速率和结晶度,经过中等拉伸比例的PLLA薄膜,其阻湿阻氧能力相对较强。     

The thermal behaviour of glass fibre investigated by thermomechanical analysis

A thermomechanical analysis (TMA) procedure has been developed with the capability of probing the thermal behaviour of glass fibre. A single glass fibre was successfully mounted into TMA fibre configuration and several thermomechanical programmes were carried out over a wide temperature range from 20 to 900 °C. It was found that measured coefficient of linear thermal expansion of boron-free E-glass fibre remained constant below 300 °C and the values had an excellent agreement with that found in the literature. At higher temperatures an abrupt length change in glass transition region allowed for the determination of glass transition temperature. The results from isothermal measurement showed significant fibre length shrinkage, which was a function of both temperature and time. It follows that there exist two mechanisms, thermal expansion and structural relaxation, which together account for overall thermomechanical responses of glass fibre. The former is related to the decrease of Young’s modulus at elevated temperatures and the latter is considered responsible for the observed increase of room-temperature Young’s modulus after thermally conditioning glass fibre at various temperatures.     

PAN纤维热松弛行为控制与聚集态结构调控EI北大核心CSCD

聚丙烯腈(PAN)纤维在纺丝过程中会形成受迫高弹形变,在受热条件下会出现物理收缩为代表的热松弛行为,发生解取向。通过热力学分析仪(TMA),动态力学分析仪(DMA),广角X射线衍射法(WAXD)等手段研究PAN纤维的热松弛行为,并且通过张力和温度对其进行控制。结果表明:PAN纤维纺丝过程形成的高弹形变约占10%以上,在高温下会迅速回复发生解取向。通过施加适当的张力和提高温度可以在不损失取向结构的同时将高弹形变转化为塑性形变。在张力和温度的作用下,纤维内部聚集态结构重排,分子链取向进一步提高,晶态结构进一步完善,纤维尺寸稳定性提高50%以上。研究表明经此方法处理的碳纤维微晶沿分子链排列更加规整,性能得到了有效提升。     

高分子量聚苯硫醚的热分析

用ＤＳＣ和ＴＭＡ测定了高分子量聚苯硫醚树脂的玻璃化转变温度,结果温主、熔点等热转变参数,研究了热退火处理对这些转变参数的影响,结果表明,两种方法测定的ＰＰＳ的热转变温度是一致的。     

Stabilization of exotic minority phases in a multicomponent self-assembled molecular network

Trimesic acid (TMA) and alcohols were recently shown to self-assemble into a stable, two-component linear pattern at the solution/highly oriented pyrolytic graphite (HOPG) interface. Away from equilibrium, the TMA/alcohol self-assembled molecular network (SAMN) can coexist with pure-TMA networks. Here, we report on some novel characteristics of these non-equilibrium TMA structures, investigated by scanning tunneling microscopy (STM). We observe that both the chicken-wire and flower-structure TMA phases can host 'guest' C(60) molecules within their pores, whereas the TMA/alcohol SAMN does not offer any stable adsorption sites for the C(60) molecules. The presence of the C(60) molecules at the solution/solid interface was found to improve the STM image quality. We have taken advantage of the high-quality imaging conditions to observe unusual TMA bonding geometries at domain boundaries in the TMA/alcohol SAMN. Boundaries between aligned TMA/alcohol domains can give rise to doubled TMA dimer rows in two different configurations, as well as a tripled-TMA row. The boundaries created between non-aligned domains can create geometries that stabilize TMA bonding configurations not observed on surfaces without TMA/alcohol SAMNs, including small regions of the previously predicted 'super flower' TMA bonding geometry and a tertiary structure related to the known TMA phases. These structures are identified as part of a homologic class of TMA bonding motifs, and we explore some of the reasons for the stabilization of these phases in our multicomponent system.     

Thermal expansion of composites with shape memory alloy inclusions and elastic matrix

Incorporation of shape memory alloy (SMA) inclusions into a continue matrix can make composites with various thermal dilatation behavior, and this depends sensitively on the microstructural parameters of the composite. A micro-mechanical method is proposed to relate quantitatively the overall thermal dilatation with the microstructures and the transformation characteristics of SMA materials. Composites with aligned and with two populations of perpendicularly oriented SMA inclusions are analyzed in detail in this paper. It is found that the composite with SMA fibers can have a large transformation temperature range during the heating process, and a linear shrinkage may take place during the cooling because of the large difference between the austenite finish and martensite start temperatures of the composite. Design aspects to minimize the overall thermal dilatation during a full thermal cycle are also discussed.     

Thermomechanical Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

The thermomechanical analysis (TMA) of Cu 0.5 Tl 0.5 Ba 2 Ca 2 x R x Cu 3 O 10 δ,where R=Pr and La,with 0.0≤x≤0.15,was carried out in temperature range from 450 to 1145 K.The samples were prepared by singlestep solid state reaction technique.The prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).The superconductivity of the prepared samples was investigated by electrical resistivity measurement.The results showed that low substitution content enhanced the (Cu 0.5 Tl 0.5)1223 phase formation,while the higher substitution content degraded this phase.The higher superconducting transition temperatures T c were found to be 114 K and 109 K at x= 0.025 for Pr-and La-substitutions,respectively.The average linear thermal expansion coefficient increased as x increased,while the shrinkage temperature decreased as x increased.Those results were emphasized by porosity and Vickers microhardness calculations.Debye temperature θ D was calculated from the linear thermal expansion coefficient data and correlated to T c to estimate the electron-phonon coupling λ ep.     

塑料热收缩膜的发展

主要从热收缩膜用树脂、热收缩膜工艺、热收缩膜设备3个方面进行了阐述.介绍了热收缩的工艺原理及性能要求,重点论述了热收缩膜用的新树脂品种、新成型工艺及新成型设备.并预言热收缩膜将是塑料工业未来发展的热点之一.     

TMA4000在电子工业领域中使用标准测试方法的应用

电子线路板的主要破坏原因之一是由热膨胀引起的问题。要防止这种情况发生,电子工程师采用热导体来发散热量,用低膨胀性材料来配合低膨胀率的硅片和陶瓷绝缘体的使用。热机械分析（TMA）长期以来应用于测量线路板、电子元件和组成材料（CTE）。针对玻璃化转变温度、热膨胀系数变化的点、样品软化和应力释放效应的发生,已经建立起成熟可靠的标准测试方法。对于层状复合产品,TMA相应的测试方法可以确定在评估升温过程中材料的分层所需时阃。TMA4000的设计大大简化了上述测试过程,非常适用于测量低膨胀率的小器件的膨胀。本应用文章提供了这些标准方法的一些案例。     

Thermal expansion behavior and microstructure in bulk nanocrystalline selenium by thermomechanical analysis

Thermal expansion behavior of bulk nanocrystalline (NC) Se samples with a grain size range of 16–46 nm was studied by thermomechanical analysis (TMA) in the temperature range 290–373 K. Bulk NC Se samples were prepared by isothermally crystallizing the as-quenched bulk amorphous solid at 373–478 K. The glass transition and crystallization of the remaining amorphous Se in the partially crystallized samples were studied by TMA, and compared with the results of differential scanning calorimetry (DSC). The glass transition temperature, as determined from the thermal expansion behavior, was 308 K, 11 K lower than the value by DSC analysis. A structural densification phenomenon was observed in a grain growth process of an as-crystallized NC Se sample by TMA. It was found that the linear thermal expansion coefficient of the bulk NC Se sample increased with a reduction of grain size, from which the deduced thermal expansion coefficient of the interface decreased with the refinement of the grain size.