By Alan Jaenecke, Taber Industries
A typical consumer is only aware of the aesthetic aspect of decorated plastic parts. What they see are the visual traits of the product, such as the color scheme or if artwork was included to reinforce a brand image. There are other reasons beyond aesthetics for decorating plastics, but the consumer will overlook most of them. Perhaps the decoration was formulated to provide additional value, such as increased protection against abrasion, scratch/mar damage or resistance to cleaners, hand cream, suntan lotion, gasoline and other chemicals.
If the product is expected to provide a desired “performance” over its average lifespan, there are two questions that producers must ask: What is the desired performance? And what is the average lifespan? Besides operating as intended, customers expect the product will withstand the rigors of everyday use. However, not all products need to perform the same, so it is essential to know what the customer considers important and the customer’s expectations. For example, color and gloss retention may be essential for outdoor products exposed to UV in sunshine states like Florida, Arizona or Texas.
The ability to last over time, resisting wear and deterioration, is the product’s durability. How long is the product expected to last? While many products last longer than their “average” lifespan, knowing a minimum threshold provides a starting point for determining if the product will meet this requirement. This is especially important for products that are used in high-touch traffic areas, such as elevators, airports and public transportation, or for products that have an expected life cycle (such as a cell phone, which is projected to last two to three years, a laptop computer three to five years, television four to seven years, or an automobile that lasts approximately 12 years). It is essential to understand what the customer’s expectations are and what value the decoration offers. Knowing what is important to the customers is vital to ensure that the product will perform as desired.
The value of testing
It has been close to two years since pandemic-related supply chain issues started having a negative impact on manufacturers. The most commonly reported complications include longer lead times, higher costs, labor challenges, difficulty obtaining raw materials and business closures. In today’s changing environment, unprecedented cost increases have forced many companies to consider alternative solutions to remain competitive. While these changes may ensure the business can continue selling its product, are manufacturers certain the alternatives will not have unintended consequences at some point in the future?
If looking for a lower-cost decorating solution, understand that coating formulas play a critical role in durability performance. Not all coatings are the same nor will they offer the same performance. The combination of binders, additives, pigments and resins will influence the durability of the coating formulation. Therefore, if customers have an expectation the decoration will offer a specific property, it may be months or even years after a change is made before a problem is discovered. This highlights the value of testing to measure product durability. Whether contemplating cost savings initiatives or changes to the supplier base/manufacturing process, laboratory testing is necessary to ensure the product will perform as expected. This also applies to companies looking to implement a new technology or a more environmentally friendly decorating solution.
Over the past 20-plus years, there has been a shift for manufacturers to delegate material testing to a third party. If the company had relationships with established suppliers, who were already testing for their own quality control purposes, this made sense. Shifting the testing to a third party allowed many manufacturers to realize cost reductions and improve efficiencies, streamline operations and concentrate on their core competencies. Unfortunately, the recent supply chain concerns have exposed that many companies no longer have the in-house testing knowledge or expertise to evaluate the different options they are considering. How does a company’s purchasing department determine if the finished product will be durable and perform as expected when it’s evaluating new vendors? If durability is important, it certainly is not advisable to “wait and see” or cross one’s fingers and hope there are no problems. Rather, the preferred solution is to have the parts tested. If suppliers were relied upon to help make these critical decisions, who now should be trusted when a company is trying to evaluate its choices?
Provided a knowledgeable person established the test plan, they likely based the required tests on industry standards. If the company is like other companies that outsourced testing, chances are that historical solutions were specified to evaluate the product. This is good news because there should be other independent labs that will be able to perform the tests. Nevertheless, just because one has years of data does not mean that the situation should not be re-evaluated. If the supplier was conducting the testing for the company, it may be time to speak to another expert to determine if the established methodology is still applicable to the product and if the data is meaningful for how the product is used. With material advancements and changing technologies, this also presents an opportunity to ask what other testing options should be considered.
Do you know what is important?
How does one identify what properties should be evaluated? If customers have told the company what is important, most of the work is already completed. However, if one is unsure, a good starting point is to review recent warranty claims and customer complaints. Understanding the problems customers have reported gives the company an opportunity to expose potential issues that might need to be tested. Another approach is to research what the competition is doing and what claims they make. If the competitor claims its product offers “excellent resistance to wear and scratch,” the company should conduct benchmark tests to determine if its product is comparable and as durable.
The company’s sales team can provide a wealth of information regarding the intended use of the product and the features customers consider important. Knowing how the product is used also can help to develop a list that identifies the most important attributes the product should have. Think about answering the basic questions of who, what, where and how. It is not feasible to test every single condition the product might be exposed to during its life, so the list does not need to be all-encompassing. Rather, concentrate on developing a list that addresses the most common uses. Testing the most important properties is a good starting point to ensure the decorating process will be appropriate for the application.
As an example, Figure 1 shows a field failure on a control panel that includes light switches, electrical outlets and USB ports. Two of the covers display poor adhesion, as evidenced by the missing paint. For the NEMA-type outlet, the paint adhesion likely failed when the outlet cover was secured. The paint chipped and flaked off the plastic substrate when an electrical plug was inserted into the receptacle. There also are visible scratches that could indicate the coating is not scratch resistant.
Figure 2 illustrates a field failure where the paint has worn and exposed the substrate. Although the functionality of the fire alarm pull box was not compromised, the durability of the paint may not satisfy the manufacturer’s desired life. This particular example was found in a tourist attraction where departing guests walked by and touched the letters before leaving. It is doubtful the manufacturer would have been made aware of this installation, so the coating was probably not formulated for a high-touch environment. Also, the molded cover includes raised letters that were painted, which helped concentrate abrasion to this area.
In either example, it is possible these failures could have been predicted if the parts were tested. Recognizing there are many different conditions that coatings could be exposed to, will translate to a wide variety of physical property tests that may need to be considered. The most common include testing the resistance to:
- Weathering
- Corrosion
- UV
- Chemicals
- Adhesion
- Abrasion
- Scratch and mar
- Humidity/water
In a recent issue of Plastics Decorating¹, Akriti Agarwal, global project manager of Mercury Marine, was asked to give some insight on how Mercury Marine ensures the plastic components used in its outboard engines will stand up to extreme situations.
To ensure any decorative element will hold up, managers ask their suppliers a number of questions. For example, can you paint Class A surface finishes? Class A finishes typically offer the most consistent color and gloss, so the parts will look the best they can. Also, what paint chemistry is needed to achieve the desired look and performance? The performance of the coating is critical, and Mercury has found that some shops are more experienced working with acrylics while others have more experience with urethanes. Talking with the supplier helps to understand their recommendations and abilities.
The third question is, are you ISO certified for quality control purposes?
According to Agarwal, the objective is to “ensure coatings can live and thrive in water just like Mercury engines do.” To achieve this, the physical properties that are important to Mercury Marine include color, gloss, orange peel, coating thickness, methyl ethyl ketone (MEK) solvent rub, cross hatch adhesion, pencil hardness scratch, impact resistance and chip resistance.
Testing challenges facing businesses
During the pandemic, a tremendous amount of knowledge was lost as employees changed positions or left the workforce due to retirement. If a company does not have the expertise in-house to help determine a path forward, where does it go for help? While suppliers historically have been a tremendous resource, the company may find that it is in a similar situation and no longer has the knowledge base it once had. Despite the initial up-front cost, speaking with a consultant that has industry expertise and can target a solution for the specific application has worked well for many organizations and ultimately saved money. Other sources to consider include industry organizations or standards committees that provide a forum to discuss concerns with other companies. In addition, instrument manufacturers typically have sales engineers available that can offer advice.
No matter who is advising the company, the testing selected is attempting to simulate real-life damage that involves a complex combination of interrelated properties. The ideal solution would be to analyze the product in actual use, under the intended use conditions. The disadvantage to this approach is the time required to obtain results, the cost, and the inability to identify (or control) what the product is exposed to.
Although accelerated laboratory techniques may not exactly duplicate the mechanics seen in real life, they are an approximation that allows operators to establish an approach that is easy to follow and can provide meaningful and reliable data. Laboratory tests should control the test parameters and compress the life span of a product, allowing materials to be evaluated using the same set of criteria. Having greater control over individual influences during the testing improves an understanding of physical properties, allowing real-world damage to be recreated. The resulting information can then be used to predict field performance.
It is interesting to note that most coatings test methods were developed for metal substrates and may require modification to evaluate today’s coatings and decorating techniques. Recognizing this, an ISO subcommittee on General Test Methods for Paints & Varnishes has begun work on identifying how plastic substrates differ from metal substrates. In a presentation to ISO/TC35/SC9/WG31, the following differences were identified and a proposal was submitted to develop technical reports for coatings on plastics that address each of these:
- Thermal conductivity
- Specific heat capacity
- Substrate deformation
- Phase transitions (softening and melting temperatures)
- Substrate aging
- Additive migration
- Barrier effect of the substrate
- Thermal expansion
- Volume changes due to water absorption
- Adhesion
- Weight
- Elasticity
Laboratory testing is essential to ensure the product will be durable enough to hold up to everyday use. It also helps ensure the company is producing a quality product, that the manufacturing process is in control and that the chosen decorating technique will perform to expectations.
Alan Jaenecke is vice president of marketing, materials test & measurement/press divisions, at Taber Industries. Having previously operated Taber’s in-house test facility, Jaenecke has a wealth of experience conducting wear and durability tests. He continues to share his expertise in material testing by participating with standards organizations, including ASTM, ISO, NEMA, Tappi and SAE. In addition to coordinating test method reviews, Jaenecke has written numerous ASTM standards.
References
- Paintings and Coatings for Plastic Parts – Plastics Decorating magazine, 05/04/2021
