浅析影响纸张含水量的主要因素

在印刷中纸张是最基本,使用在印刷中纸张是最基本,使用最多的承印材料。纸张的性质和形状会因各种情况而发生变化,而纸张含水量的过多或过少就是其中之一。纸张含水量的正确分析及处理,对于提高纸张的印刷适性,提高彩色印刷品的色彩和阶调的再现,提高细微层次的清晰度等都起到重要的作用。一、纸张含水量的大小对印刷的影响由于纸张本身化学性质和周围环境的相对湿度、温度影响,其含水量会发生变化,胶印车间的相对湿度应控制在55%～60%为宜。纸张的含水量过大,使纸张的抗强能力减弱,塑性增强,易变形,套印误差较大。当紧度过大时…     

纸张含水量对印刷及覆膜的影响

印刷用纸是以植物纤维为主交织而成的胶片。在纤维交织中,纤维间又形成许多毛细孔隙,使纸张具有很敏感的吸水性和脱水性。1．纸张含水量与纸张变形纸张的含水量是一个可变量,是决定纸张形变的第一要素。当纤维吸收水分时,会发生膨胀．使纸张直线尺寸增加,面积也增大;纤维脱水时．纸张含水量相应减少,纸张直线尺寸和面积缩减。因此‘纸张在印刷过程中。会吸收版面的水分．同时也会随空气湿度变化吸收或释放出水分。在吸收或释放水分过程中,纸张会发生以下变形。（1）在印刷过程中．纸张吸收水分后整体膨胀变形,但仍保持纸张原有的平…     

手把手教你设计纸张含水量测定仪

正纸张含水量是纸张的重要特性之一,其对纸张的印刷过程有很大影响。含水量过高,不仅会影响纸张的表面强度,导致纸张在印刷过程中出现脱粉、掉纸屑等现象,还会影响油墨的干燥速度;含水量过低,纸张则容易因发脆而破损。此外,纸张含水量控制不好,还会引起印刷机前规和侧规定位不准,影响套印精度。因此,准确测量纸张含水量对顺利完成     

浅析纸张含水量对印刷的影响

纸张是印刷叶,使用最多的承印材料,纸张的特性在很大程度上影响着印刷品的质量,而含水量是其重要的性质之一,含水量的大小与印刷产品有着直接的关系。因此正确分析纸张的含水量对印刷的影响尤为重要 一、影响纸张含水量的因素 1.纸张的主要组分是植物纤维和其它主要用作填料的亲水物质、如粘土、高岭士、石膏粉等,它们的物理     

纸张变形及控制方法

在印刷过程中,根据引起纸张变形的因素的不同,纸张变形主要分为以下两种：纸张受力变形（纸张受外力作用引起的变形）和纸张自然变形（纸张由于自身含水量变化引起的变形）。纸张变形不但影响正常的输纸工作,还会影响印刷套印精度,以及导致印刷故障产生。下面我们就分别针对上述两种纸张变形及控制方法进行简要分析。     

网点在纸张上会增大

纸张的印刷适性是决定于其表面特性,如对油墨的吸收份量及接受程度,此会影响网点在纸张表面的增大值。表面吸收性强,印刷品网点增大的程度就越大,故纸张对油墨的吸收速度是其中一个影响网点增大的关键。纸张表面平滑度的高低,都对网点增大起作用。平滑度高的表面,网点增大值小;相反,平滑度低的表面,网点增大值大。 在印刷纸张中,涂布纸的吸收性比非涂布纸强,而高吸收性的结果是网点增大的程度高。因不同造纸厂有自行内部的纸     

纸张含水量及酸碱性对印刷的影响

就纸张的含水量及酸碱性对印刷效果的影响进行分析,力求为纸张制造工艺和印刷企业提供应用方面的参考依据,并提出控制纸张含水量和酸碱性相应的改进措施。     

细小纤维对于纸张呈色的影响

纸张的呈色效果主要与纸张平滑度和白度有关。细小纤维对纸张结构、纤维结合程度以及纸张孔隙率产生较大影响,进而影响到纸张的表面平滑度。本文通过提高打浆转数来增加细小纤维含量,通过改变细小纤维含量来探究细小纤维对于纸张平滑度以及对撕裂度、抗张等印刷适性的影响。在纸页上输出不同色密度的C/M/Y/K色块,分析表征纸张的表面平滑度以及呈色性能。通过实验发现:当细小纤维的含量逐渐减少的时候,纸张的撕裂度、平滑度、耐折度和表面强度随之增大;细小纤维含量较高的纸张色密度要高于普通纸张。     

纸张伸缩的解决方法

纸张含水量是一个可变量：是决定纸张形变的第一要素。当纤维吸收水分时,就会发生膨胀,使纸张直线尺寸增加,面积增大,印到纸张上的图文随之尺寸增加,面积增大。纸张后梢由于湿度的影响而伸长,给下一色套印带来了麻烦,在前规和侧规没有改变的情况下。我们用80g／m2铜版纸折了一个领带式的纸模型,用胶粘在输纸板中间,使进入）－－k印的第一张纸后梢凸起2－3mm进行压印,效果比后梢没l－－］－;’）J起的纸张套印得准。在纸张伸缩太严贵的消况1二．川］半面套印的方法,可以取得较好的印刷效果。按照常规：半！h会印时要光清除印版L…     

浅析纸张的力学性能及其对印刷的影响

纸张,作为印刷这个系统工程中几种重要的耗材之一,对之进行有效控制是保证印刷顺利进行的必要条件.所以我们非常有必要了解一些纸张的性能,而在这些性能中又以纸张的力学性能对印刷的影响最大,以下将简要介绍一下纸张的力学性能.     

Resistance of packaging against infestation by Sitophilus zeamais

The results of infestation by maize weevil, Sitophilus zeamais (Coleoptera, Curculionidae), in different packaging filled with pasta are presented in this research. Three different types of packaging were used, that is, two paper tubes (one novel, laminated with bio-based polyethylene and one without lamination) and commercial polypropylene, pillow pouch packaging. Material properties such as grammage, thickness, surface analysis, moisture and water resistance, tensile and compressive strength were analysed. Improved compressive strength, moisture and water resistance were detected at the bio-polyethylene laminated tube packaging (approx. 30%), compared to the non-laminated sample. The obtained results demonstrated that adult maize weevils revealed significant preferences to enter the pasta packages through the already existing holes which were in the polypropylene packaging, while no infestation was observed inside the packages at the paper tube packaging. The study revealed that the shape and construction, for example, tube packaging with an innovative bio-polyethylene film, are very effective regarding insect infestation and mechanical overloads.     

Biopolymer Coatings on Paper Packaging Materials

ABSTRACT: Increased environmental concerns over the use of certain synthetic packaging and coatings in combination with consumer demands for both higher quality and longer shelf life have led to increased interest in alternative packaging materials research. Naturally renewable biopolymers can be used as barrier coatings on paper packaging materials. These biopolymer coatings may retard unwanted moisture transfer in food products, are good oxygen and oil barriers, are biodegradable, and have potential to replace current synthetic paper and paperboard coatings. Incorporation of antimicrobial agents in coatings to produce active paper packaging materials provides an attractive option for protecting food from microorganism development and spread. The barrier, mechanical, and other properties of biopolymer‐coated paper are reviewed. Existing and potential applications for bioactive coatings on paper packaging materials are discussed with examples.     

不同塑料包装材料对坛紫菜贮藏期间吸湿特性的影响

研究不同塑料包装材料(LDPE、HDPE、PET、PA/PE、尼龙、PET/PE)对坛紫菜贮藏期间水分含量、水分活度的变化,探讨包装材料对坛紫菜吸湿特性的影响。结果表明,随着贮藏时间延长,不同包装材料的坛紫菜水分含量及水分活度Aw增加,其等温吸湿曲线呈"反S型"特点,等温吸湿曲线拟合方程的相关系数均大于0.9595,可较好预测其水分活度与干基含水量的关系;同时,根据等温吸湿曲线预测不同包装材料的坛紫菜干基含水量控制在7.5%-9.8%时可较好防止其吸水霉变。     

Effect of Type and Content of Modified Montmorillonite on the Structure and Properties of Bio-Nanocomposite Films Based on Soy Protein Isolate and Montmorillonite

Abstract: The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na⁺). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.     

添加沉析纤维增强对位聚芳酰胺纸性能

采用间位沉析纤维对对位聚芳酰胺纸进行增强,研究沉析纤维的添加对芳纶纸机械性能和电气绝缘性能的影响,并使用扫描电子显微镜研究芳纶纸表面微观结构。研究表明,沉析纤维的添加对对位聚芳酰胺纸具有显著的增强效果,可以明显增强其机械性能;同时又可使其保持较高的绝缘性能。当沉析纤维添加量为20%时,对位聚芳酰胺纸可以达到理想的增强效果,与不添加沉析纤维相比,成纸的抗张指数、伸长率和撕裂指数分别增加55.3%,49.5%和22.1%。     

生物胶乳对彩喷纸性能的影响

生物胶乳以价格低廉、低碳环保、能够替代石化胶乳制备性能优良的涂料等优势被应用于造纸工业中。将生物胶乳不同比例替代聚乙烯醇并应用于彩喷纸底涂和面涂涂料中,分析了其对彩喷纸物理性能(如白度、不透明度、表面粗糙度、光泽度等)及印刷性能(如油墨吸收性等)的影响。结果表明,生物胶乳的加入可提高彩喷纸的白度、不透明度、光泽度、表面粗糙度、油墨吸收性等,降低紧度、耐破度、表面强度等性能。生物胶乳在底涂和面涂涂料中的替代率分别为60%和40%时,彩喷纸性能最佳。     

影响装饰纸质量的因素

从装饰纸的原纸和印刷两个方面,探讨了装饰原纸的均一性、定量、pH值、干湿强度、水分、透气度、吸液性、平滑度、光泽度以及填料、树脂、印刷油墨对装饰纸质量的影响。指出使用优质原纸、优化树脂配方、选择优质印刷油墨,才能生产出高质量的装饰纸。     

面制品干燥过程中水分迁移机制及影响因素分析

内外水势差是水分迁移的动力。水分由高水势向低水势迁移是机制。通过综述了水势差及差值对水分迁移过程的影响，以确证该机制，为研究低能耗干燥提供数据和理论支撑。内部水势可以用水分活度表征，外部水势可以用环境相对湿度表征。内外水势差越大，水分迁移的动力越大。内部水势会随着水分含量、淀粉占比、孔隙率、外界环境温度的增加而升高；外部水势随着环境相对湿度的增加而升高。不同的水势调控方案可实现相同的水分迁移量，但对面制品的质量和能耗影响不同，为高质量面制品低能耗干燥工艺提供了设计思路。     

紫苏叶保鲜纸袋的研制及其基本性能分析

为延长紫苏鲜叶货架期,保证叶片在贮藏及零售时的贮藏品质,本研究采用新研制涂膜保鲜纸袋对紫苏叶片进行包装处理。试验所用复合涂布液由壳聚糖、D-异抗坏血酸钠、茶多酚及氯化钙按照一定比例溶于乙酸水溶液配制而成,通过单因素及正交试验考察保鲜纸袋复合涂布液中不同组分浓度对紫苏叶感官品质、V_C含量及失重率的影响,确定复合涂布液最佳组分浓度配比:壳聚糖浓度2.0%、D-异抗坏血酸钠浓度2.4%、茶多酚浓度0.25%、氯化钙浓度0.6%。通过物理、化学及抑菌性能分析表明,当涂布量为30 g/m2时,复合涂布液在纸张表面形成均匀涂层,具有较强抑菌能力,且涂料渗入纸张纤维间隙内部,使得纸张重量、厚度、伸长率、水分含量皆有所提升,水蒸气透过系数下降,抗张强度及润湿性能略有下降,符合紫苏叶片包装要求,本研究预计将在果蔬包装领域具有广阔发展前景。     

Water vapour barrier and tensile properties of composite caseinate-pullulan films: Biopolymer composition effects and impact of beeswax lamination

The water sorption, water barrier properties and mechanical behaviour of pullulan (P) and sodium caseinate (SC), as well as their blend and bilayer films plasticized with sorbitol (25% dry basis), were investigated as a function of weight polymer ratio, water content and beeswax lamination. Very similar moisture sorption isotherms were obtained for blend and bilayer films with P/SC weight ratio of 1/3 and 3/1. Neither the type of film (blend or bilayer) nor the different P/SC ratio affected significantly (P > 0.05) the water vapour permeability (WVP) of the films. A mixture-process variable experimental design was applied to evaluate the effect of the proportion of the two polymers in relation with the relative humidity (RH, 53% and 75%) on the mechanical properties of the films. Increasing the P/SC ratio decreased the Young’s modulus (E), the tensile strength (σ_max) and increased the % elongation at break (% EB), suggesting that P imparts flexibility and SC stiffness to the composite films. With moisture content increase from 5% to 8% most of the films exhibited an increase in E and σ_max, whereas a sharp decline in both parameters and an increase in % EB were observed above this moisture level. The brittle to ductile transition of P coincided with its glass to rubber transition, whereas SC exhibited a ductile behaviour within the glassy state. The tensile characteristics of bilayer films at moisture content greater than 8% were dominated by the component present in higher proportion, while films made with the biopolymer blends showed mechanical behaviour closer to that of plain P films. Beeswax lamination of plain, bilayer and blend films resulted in a drastic decrease in water vapour permeance, whereas its effect on E and σ_max and in % EB was related to the mechanical properties of the hydrocolloid layers used and varied according to the moisture content of the films.