牛奶包装黑白膜的设计及性能研究

论文标题:牛奶包装黑白膜的设计及性能研究
Design and Performance Study on the Black & White Film for Milk Packaging
论文作者
论文导师 许文才；曹国荣,论文学位 硕士,论文专业 材料物理与化学
论文单位 北京印刷学院,点击次数 22,论文页数 56页File Size709k
2006-03-20论文网 http://www.lw23.com/lunwen_427838007/
black and white film;uniform design methods;co-extrusion compound;regression model
本论文在确定材料结构和各层原料及其比例范围的基础上,采用均匀设计法设计实验方案,通过三层共挤复合工艺制备黑白膜,测试分析黑白膜的黑度均匀性、白度均匀性、拉伸强度、热封性、摩擦系数、透气性和透湿性等,为黑白膜配方和结构提供一种具有指导意义的设计方法。黑白膜的材料结构设计为外、中、内三层,材料组成为“聚乙烯+白母料/聚乙烯+白母料/聚乙烯+黑母料”。各层功能设计为:外层(印刷层)为白色,起阻湿、阻光作用;中间层为白色,起遮盖内层黑和阻湿的作用;内层为黑色,起避光和热封作用。设计实验时,将外、中、内三层的线性低密度聚乙烯含量作为三个影响因素,含量范围在 30%～80%内变化,每个因素取六个水平。研究结果表明:当外层和中间层的白母料含量大于或接近内层黑母料的含量时,薄膜的白度值较高,阻隔光线的能力最强;影响薄膜力学性能的主要因素是原料树脂中线性低密度聚乙烯的添加量,应用二次回归法求得其回归方程,并给出了线性低密度聚乙烯的最佳含量和薄膜的最佳力学性能;热封压力为 0.25MPa时封口强度最稳定;薄膜表面摩擦系数在 0.2～0.4 范围内,可满足自动包装机要求;薄膜的氧气透过量随线性低密度聚乙烯含量的增加而减少,适当增加碳黑层也能降低氧气透过量,这主要是与碳作用以及多层共挤薄膜的氧气通过不同材料时的界面扩散行为有关,增加碳黑层能对乳品起到避光作用,能减少光敏度的影响;聚乙烯本身是很好的阻湿材料,加入少量的黑母料或白母料,对薄膜的阻湿性能影响不大。
Based on the decision of the structure of the black and white film and theproportion span of raw material, adopted uniform design method to design theexperiment program, the film is manufactured with the tri-co-extrusion machine andits performances are analyzed such as black and white uniform, tension intensity, heatsealing, friction coefficient, permeability and so on.The performance of the film is researched in detailed on some testing equipment,such as universal testing machine, penetrating gas apparatus, penetrating moistureapparatus. The aim of the paper is to offer an instructed design method of the film.The structure design of the film is the three layers, in which the materialcomposition is PE+ white matrix/ PE+ white matrix/ PE+ black matrix. The outerlayer, also called printing layer, is white and acts as the role of inhibiting luminousbeam and moisture. The middle white layer masks the inner black and inhibitsmoisture. The inner layer is black and acts as light barrier and heat sealing.The experiments are arranged on the base of uniform design method. Taked thepercentage of LLDPE in the each layer of the film as three factors, the span of theLLDPE percentage is from 30% to 80% . For each factor there are six levels. Research suggests that light barrier is acquired effectively when thepercentage of the white matrix in the outer layer and the middle layer is larger than orequal to that of the inner layer. The percentage of LLDPE is the major effected factoron mechanics performance of the film and a regression equation can be achieved byregression analysis.In the condition of 118 ℃ and 0.25MPa, the sealing intensity mostlyapproximates to 1.4mPa. The friction coefficient of the film is within the permissionof the auto-packaging machine. The O2 permeability is reduced with the addedpercentage of LLDPE in the layer, however, proper quantities of black matrix addedin the film can also decrease the O2 permeability. This is relevant with interfacediffusion because the black layer reduced the effect of light sensation.PE is an excellent material of barrier moisture, and when a small amount ofmatrix is added in the film, there is little impact on the performance of barriermoisture.
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