{"id":5708,"date":"2016-12-30T08:20:59","date_gmt":"2016-12-30T14:20:59","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=5708"},"modified":"2018-02-09T14:06:04","modified_gmt":"2018-02-09T20:06:04","slug":"pe-plastic-surface-plasma-processing","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/5708\/pe-plastic-surface-plasma-processing\/","title":{"rendered":"Plasma Processing of Plastic Surfaces"},"content":{"rendered":"\n

Many engineering polymers have characteristically low surface energy and therefore exhibit intrinsically poor adhesion characteristics. The incorporation of oxygen into the surface of a polymer creates a higher surface energy, allowing the substrate to be more readily coated. Poor adhesion is also an important obstacle in achieving reliable glue joints for print adhesion applications onto materials widely used in the medical device industry, for example.<\/p>\n

Plastic surfaces can be treated by three methods which rely on surface oxidation: plasma processing, corona treatment, and flame treatment. All involve cleavage of polymer chains in the material and the incorporation of carbonyl, and hydroxyl functional groups.<\/p>\n

The characteristics, advantages and limitations of the three methods are summarised in Table 1.<\/p>\n

\"TABLE:<\/a>
Click image to view PDF<\/strong><\/figcaption><\/figure>\n

Plasma processing has been an essential production tool for more than 30 years in the fabrication of microelectronic devices for example. Over this period, plasma processes have also permeated a much broader range of industries, including automotive, medical, textiles and plastics.<\/p>\n

Today, plasmas are routinely used to clean and surface treat plastic automotive bumpers, performance textiles and filter media, stainless steel syringe needles, angioplasty balloon catheters, plastic lenses, golf balls, and many other diverse products.<\/p>\n

Some plastics, including polypropylene<\/a> (PP), polytetrafluoroethylene<\/a> (PTFE), polyetheretherketone<\/a> (PEEK) and acetal<\/a> (POM) are homopolar and do not bond easily. Plasmas afford an effective surface activation pre-treatment prior to printing, lacquering or gluing. Glass and ceramics can similarly be plasma activated. It is a reliable and effective technique for increasing print adhesion and bond strength.<\/p>\n

Parts remain active for a few minutes up to several months, depending on the particular material that has been plasma treated. For example, polypropylene can still be reprocessed several weeks after treatment.<\/p>\n

Henniker Plasma is a leading UK-based manufacturer of plasma treatment equipment and processes, from low-cost benchtop plasma cleaners and plasma etchers for R&D applications, to industrial scale plant machines for high throughput processes.<\/p>\n

Several of the company’s clients use in-line atmospheric plasma surface treatment to successfully increase the surface energy of PEEK from 35mN\/m to more than 72mN\/m, ensuring permanent PAD print adhesion. The treatment remains active on PEEK for several weeks and so parts can be stored until needed.<\/p>\n

\"Engineering
PAD Printing machine and plastic bottle lids which have been plasma treated before printing (SOURCE: Henniker Plasma, UK)<\/figcaption><\/figure>\n

In another example, vacuum plasma treatment of PTFE has been adopted for printing and gluing steps in catheter manufacture, where a PTFE surface is modified to produce a permanent change in surface energy from 18mN\/m to more than 72mN\/m.<\/p>\n

Coating Plasma Industrie (CPI) is a pioneering company in cold plasma surface treatment located in the south of France. This process can be operated at atmospheric pressure or under vacuum in applications in packaging, printing, polymer transformation and textiles.<\/p>\n

CPI is one of few companies capable of offering complete roll-to-roll turnkey atmospheric plasma systems, as stand-alone equipment or fully integrated into a production line.<\/p>\n

What is plasma?<\/em><\/h4>\n

Solid, liquid and gas are the three states of matter we are all familiar with. We can move between the states by adding or removing energy (e.g. heating\/cooling). If we continue to add enough energy, gas molecules will become ionised (lose one or more electrons) and so, carry a net positive charge. If enough molecules are ionised to effect the overall electrical characteristics of the gas, the result is called a plasma.<\/em><\/p>\n

Plasmas are often referred to as the fourth state of matter. A plasma contains positive ions, electrons, neutral gas atoms or molecules, UV light and also excited gas atoms and molecules, which can carry a large amount of internal energy. In fact, plasmas glow because light is emitted as these excited neutral particles relax to a lower energy state.<\/em><\/p>\n

Common examples of plasmas include:<\/em><\/p>\n