Ambient Processing of Polymeric Web: Advanced Diagnostics and Applications

聚合物网材料在当今社会无处不在，在塑料电子和可生物降解或可堆肥包装等不同领域的需求也在增加。然而，对绿色技术、减少能源使用和降低材料使用的需求显然是未来全球制造业要求的最前沿，任何新产品都必须符合这些标准。决定聚合物性质和性能的关键是它的表面功能。对于包装等应用，这些可以包括防止水分和空气进入破坏产品的能力（即屏障性能）或标签信息可以印刷到包装上的便利性（可印刷性）。这些表面功能现在正在许多行业中通过大气压等离子体处理进行修改，特别是使用一系列称为介质阻挡放电（DBD）的放电。简单来说，DBD由一对平行板组成，由一个小间隙隔开，其中至少一个板覆盖有介电材料。DBD等离子体处理技术取代了传统的聚合物网加工方法（如真空技术），为更清洁、更高效的加工提供了机会，并为许多应用指明了前进的方向。DBD的几何结构非常适合web处理，并且显然有可能在该领域产生重大影响。例如，采用DBD技术涂覆的聚丙烯薄膜可以取代目前用于食品包装的氯化聚合物产品。这些材料提供了一个透明的屏障层，但氯化聚合物的使用受到环境立法的压力，现在需要替代品。在工业中，重要的是要在整个聚合物上均匀地进行任何卷材处理，而不会对表面造成有害损害。理想情况下，这需要均匀放电。然而，介质阻挡放电通常以丝状模式运行，经常导致不均匀和小规模的不均匀处理，以及处理膜的部分热降解。然而，直到最近，还没有证明可以实现可靠和可控的等离子体放电，以在大面积上提供所需的表面功能。这部分是由于缺乏对排放的基本过程及其与过程稳定性和结果的关系的理解，这限制了大规模系统的开发。该提案旨在对DBD的物理和化学进行详细研究，该DBD专门设计用于复制工业规模卷对卷大气等离子体处理系统的关键元素。我们将集中讨论两种聚合物基底；聚丙烯和纤维素，它们有广泛的商业应用。我们将只关注可能提供特定表面功能的工艺气体和前体，例如可打印性、阻隔性等。因此，我们将在实验室规模上研究一系列“模型系统”。这些研究的关键新颖元素将是首次使用分子束质谱法探测DBD系统，此外还有新的电源设计，包括用户定义的脉冲波形。这些测量将被补充，时间分辨光学发射光谱OES和二维滤波光学成像将被用来识别和绘制出主要发射物质（离子和中性）。结合表面化学和等离子体组成研究的结果，我们将努力对这种放电中的表面化学路线以及等离子体状态和衬底之间的相互作用产生全面的了解。在这些“模型系统”上获得的信息将通过我们的合作者Innovia Films Ltd.的重新设计，转移到现有的2米长的卷到卷工业规模处理系统。

Polymeric web materials are ubiquitous in today's society, with demand set to increase in areas as diverse as plastic electronics and biodegradable or compostable packaging. However, the need for greener technologies, reduced energy usage and lower material usage is clearly at the forefront of all future global manufacturing requirements, and any new products must meet these criteria. Key to determining the properties and performance of a polymer are its surface functionalities. For applications such as packaging, these can include the ability to prevent moisture and air ingress spoiling the products (i.e. barrier properties) or the ease with which labelling information can be printed onto the packaging (printability). These surface functionalities are now being modified through atmospheric pressure plasma processing in a number of industries, particularly using a family of discharges known as dielectric barrier discharges DBD's. In simple terms DBD's consist of a pair of parallel plates separated by a small gap, with at least one plate covered with a dielectric material.The replacement of conventional polymer web processing methods (such as vacuum-based technologies) with DBD plasma processing provides opportunities cleaner, more efficient processing and points the way ahead for many applications. The DBD geometry is ideally suited to web processing and clearly has the potential to make a major impact in this field. For example, polypropylene film coated by DBD technology could replace the current chlorinated polymer products for food packaging. These materials provide a transparent barrier layer, but the use of chlorinated polymers is under pressure from environmental legislation and alternatives are now required.In industry it is important that any web processing is performed uniformly across the polymer without detrimental damage to the surface. This would ideally require a homogenous discharge. However, dielectric barrier discharges usually operate in a filamentary mode, often resulting in non-uniform and small scale inhomogeneous treatment, and partial thermal degradation of the treated films. However, until very recently it has not proved possible to achieve reliable and controllable plasma discharges to deliver the desired surface functionalities over large areas. This is in part due to a lack of understanding of the fundamental processes of the discharge and their relationships to process stability and outcomes, which has limited large-scale system development. This proposal seeks to undertake a detailed investigation of the physics and chemistry of DBD's specifically designed to replicate key elements of an industrial scale reel-to-reel atmospheric plasma processing system. We will concentrate on two polymer substrates; polypropylene and cellulose, which find a range of commercial applications. We will focus only on process gases and precursors likely to deliver specific surface functionalities e.g. printability, barrier, etc. Thus, we will study a series of 'model systems' on the laboratory scale. Key novel elements of these studies will be the first use of molecular beam mass spectrometry to probe the DBD systems in addition to new power supply designs, incorporating user defined pulsed waveforms. These measurements will be complemented, time-resolved optical emission spectroscopy OES and 2-D filtered optical imaging will be used to identify and map out the key emitting species (ionic and neutrals) in the bulk discharge. Combining the results from the surface chemistry and plasma composition studies we shall endeavour to produce a comprehensive picture of the surface chemical routes in this discharge and the interplay between the plasma state and the substrate during the process. The information gained on these 'model systems' will then be transferred to an existing 2m long reel-to-reel industrial scale processing system through reengineering design at our collaborators, Innovia Films Ltd.