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Designing with Plastics

This issue of
Designing with Plastics
has been brought to you by:

Polymer Industries

An ePublication of the International Association of Plastics Distribution

March 2009 | Focus: Food Processing

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Food industry opportunities

REPRINTED FROM THE IAPD MAGAZINE

UNIPET® PET from Nytef Plastics is used extensively in the food processing industry due to its inherent FDA compliance, dimensional stability and resistance to strong cleaning solutions.

UNIPET® PET from Nytef Plastics is used extensively in the food processing industry due to its inherent FDA compliance, dimensional stability and resistance to strong cleaning solutions.

Engineering grade thermoplastic stock shapes offer food industry engineers and maintenance personnel performance advantages that are not available from traditional food grade metals. Polymers like acetal, nylon, polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) meet all of the requirements of food industry standards, provide excellent chemical resistance and, even running unlubricated, offer resistance to wear that exceeds that of virtually all metals. In applications involving rotating or reciprocating parts, the low weight of these plastics reduces the power required to drive the machinery and lowers the vibration and wear caused by non-symmetric or out-of-balance components.

Equipment components machined from thermoplastic stock shapes are ideally suited to the food industry because most food equipment manufacturers usually produce less than 100 copies per year of any given piece of processing machinery. Because machined plastic parts do not require expensive manufacturing tools, the cost per part for machined components stays relatively uniform and economical at volumes down to even a few pieces. Injection-molded parts require expensive custom-made part molds regardless of how many parts are made. Prices for these molds often exceed $10,000 and can make the cost of even small parts prohibitive as part volumes drop under a few hundred pieces.

In addition, unlike the high costs involved in making changes to injection-molding tools, changes to the design of machined components can be rapidly incorporated into the part at minimal cost. Components machined from stock shapes can also be designed with dimensions and features that are larger than what is available from injection molders and the tolerances on machined parts can be held tighter than what is typically available from molding technologies.

Metals vs. thermoplastics
When you visit any food processing plant, the one aspect of the manufacturing equipment that is immediately obvious is the wide use of metals. No matter what type of food product is produced or the manufacturing processes that are employed, the machines doing the work have been fabricated primarily out of metals. Most of the applications for engineering plastics are inside the machines where friction, abrasion and cleaning chemicals act to degrade many commonly used metals. In these applications, engineering thermoplastics provide value and benefits that are not available from the traditional metal construction materials.

The metals most commonly used to manufacture food processing equipment are 304 and 316 stainless steel. These steels have a high content of nickel and chromium that allow them to resist corrosion and oxidation. 316 stainless steel also has 2-3 percent molybdenum added to it to provide added resistance to corrosion and pitting caused by exposure to common cleaners that contain chlorine and sulfuric acid.

While stainless steel alloys provide superb strength, dimensional stability and resistance to high temperatures and chemicals, they have very poor resistance to wear. If not properly lubricated, stainless steel surfaces will quickly wear down and gall when they are run in contact against other metals. Lubricants present quality problems in food processing equipment because they have the potential to contaminate and discolor the food products being manufactured. For this reason, food industry engineers strive to minimize, and, if possible, eliminate the use of lubricants in all food equipment applications.

Thermoplastic stock shape materials like nylon, acetal, PET and PBT offer excellent wear resistance even when they are run without lubrication. By replacing either of the two contact surfaces of a metal wear interface with one of these thermoplastic materials, the wear, galling and the need for lubrication are simultaneously eliminated from the application. As an additional benefit, these thermoplastic materials are six times lighter in weight than stainless steel. As previously mentioned, the lower weight of the plastic materials provides substantial benefits in terms of lower power requirements and lower vibration levels.

Summary
While metals have traditionally been the material of choice for the designers of food processing equipment, the performance benefits of engineering grade thermoplastic stock shapes are allowing them to be used in an increasing number of food equipment applications. The rapidly growing number of successful food processing applications have solidly proven that thermoplastic shapes offer exceptional cleanliness, wear resistance and chemical resistance properties that are not available from most metals.

In addition, thermoplastic shapes offer increased manufacturing flexibility and material and fabrication costs that are significantly lower than comparable food grade metals. By learning more about plastics, designers can be sure they've made the right choice.

View the complete article online.

This article was written by Jeff Warren, Nytef Plastics, Ltd.

In This Issue:
Food industry opportunities
Food grade thermoplastic shapes offer significant advantages over metals.

Engineered polymer compounds mean reduced expenses
Polymers not only meet higher standards of sanitation and hygiene in the food processing industry, but they are also often more economical.

Different engineering plastics in food processing equipment
Plastics materials have different properties that make them best suited for a variety of applications.

Applications in food processing
Food processing applications for plastics are varied.

Test your knowledge
What do you know about plastics in the food processing industry?

Online plastic resources
IAPD offers many online search resources at www.iapd.org and www.theiapdmagazine.com, including distributor, processor, trade name and fabrication capability searches.

Find an IAPD Plastics Distributor or Processor

Search for Suppliers by Trade Name or Material and Shape

Search for Plastics Fabrication Capabilities

Search Other Plastics Articles Published by IAPD

View Past Issues of Designing with Plastics

About IAPD
The International Association of Plastics Distribution, founded in 1956, is an international trade association comprised of companies engaged in the distribution and manufacture of plastics materials.

Members include plastics distributors, processors, manufacturers, resin manufacturers, manufacturers’ representatives and associated products and services, all of whom are dedicated to the distribution channel.

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Engineered polymer components bring reduced expenses

REPRINTED FROM THE IAPD MAGAZINE

Polymer cutting surfaces, such as the one shown here made from Quadrant’s Sanalite® material, are used in a wide array of applications, from homes to commercial food preparation and in some of the largest packing plants in the United States.

Polymer cutting surfaces, such as the one shown here made from Quadrant’s Sanalite® material, are used in a wide array of applications, from homes to commercial food preparation and in some of the largest packing plants in the United States.

From breakrooms to boardrooms, the battle cry sounded over the past few years has been “reduce expenses!” But even with every pen, pencil and paper clip accounted for, expense reduction hasn’t occurred as quickly as many food processors need in order to retain financial stability. Using bearings, gears, prep tables, sprockets, guide rails and wearstrips manufactured from engineered polymers instead of metals could have a very positive impact on expense reduction efforts already instituted by these companies.

Food producers/processors face challenges today that are greater than at any other time in history:

  • Increased hygiene/sanitation standards.
  • Tighter specifications on weights, shapes and sizes.
  • Constant demand for new products.
  • Increased potential for cross-contamination in non-single use equipment.

To overcome these challenges, producers/processors are looking at equipment enhancements that bring more automation into the plant, equipment that is both economical and flexible, and investments that result in immediate payback efficiencies. Polymer components are designed with those exact results in mind — and the additional benefits polymer components provide when compared to their metal counterparts, such as noise and vibration reductions, are significant.

Meeting higher standards
In order to meet higher standards of sanitation/hygiene, processing equipment must be able to withstand frequent chemical and high impact water washdowns. In addition, the equipment and all its “parts and pieces” must meet stringent FDA/USDA standards. In many cases, compliance with NSF, 3-A Dairy and Ag Canada guidelines are also required. Several of today’s polymers meet all those requirements, such as proprietary UHMW-PE formulations. Bearings, gears, guide rails, etc., fabricated from this and other food grade polymers not only meet all the aforementioned standards and guidelines, but they are also abrasion, corrosion, chemical, moisture, impact and wear resistant.

In addition, the extremely low coefficient of friction of these UHMW-PE formulations means that food being processed won’t stick — even before the washdowns. This property, combined with zero moisture absorption, make the sanitation process more thorough and quicker, reducing the potential for cross-contamination — a benefit particularly prized today as processors use equipment for more than one product. Another benefit of using polymer components instead of metal is the fact that polymers don’t “add” anything to the food being processed. Metals rust and break off in extremely corrosive environments such as those found in meat and poultry processing plants; polymers don’t.

At the end of the day, the processor is able to meet the demands of end-users for consistent, high quality products by utilizing polymer components.

View the complete article online.

This article was written by Quadrant Engineering Plastic Products.

Different engineering plastics in food processing equipment

REPRINTED FROM THE IAPD MAGAZINE

Components made of ZL 900 (acetal) in a sausage processing machine. Photo: Poly-Clip GmbH, Germany.

Components made of ZL 900 (acetal) in a sausage processing machine. Photo: Poly-Clip GmbH, Germany.

Plastics have been used for a long time to pack food — even in direct contact with the contents. Materials such as polyethylene (PE), polypropylene (PP), nylon or polyethylene terephthalate (PET) are made into diverse packaging and films and are constantly replacing traditional packaging materials. But in the area of “machinery for food processing,” the advantages of engineering plastics over conventional materials are known and used to advantage.

In particular, the design engineers of meat processing equipment utilize the advantages of engineering plastics. The many convenient, variable material properties of modern plastics, which are continuously refined and optimized, have led to their acceptance as a true and innovative alternative to conventional materials. Much better mechanical and thermal properties, along with being non-toxic, have made plastic the first choice in many areas. Therefore, plastics are chosen more and more in the design of sensitive components. This is particularly valid in areas where food comes into direct contact with the machine part. In these areas, the full advantages of the plastics can be utilized.

When can these materials be used, and what advantages are there to using plastics? This question is often asked by the designers of meat processing equipment who are used to working with stainless steel. The next question is “Can it even hold up?” Many times, the questions of the skeptical designer go unanswered. But plastics offer immense advantages over stainless steel. With materials like PET with solid lubricant or polyetheretherketone (PEEK), specialists for highly loaded sliding applications or high temperature applications are ready to help. Nylon, acetal and polyethylene also have many common properties which make all of them convincing alternatives.

Plastics — materials with character
Each plastic has its own, different set of properties. Therefore, not every plastic is suited for all applications.

Nylons, for example, tend to absorb moisture, which can lead to swelling and dimensional changes. This eliminates its use in areas with high humidity. But because cast nylon has good damping properties, extreme wear resistance and can be produced in almost limitless dimensions, it is perfect for knock-out covers and discs for meat cutters.

Acetal, by contrast, has excellent dimensional stability and extremely low moisture absorption. A very smooth surface finish can be achieved during machining without much extra work. Therefore, this material is excellent for complex components that require high dimensional stability and very good surface quality.

PET has very similar properties to acetal but is considerably more wear resistant. It has a good combination of mechanical properties, outstanding dimensional stability and excellent wear resistance. In general, all parts made from acetal can also be made from PET. It is especially suitable for components which have high requirements for wear resistance. Especially suited to this application is PET with solid lubricant, out of which the pictured pump housing is made (pump with stainless steel mixer as sliding partner; contents: hot meat), and which has proven itself in daily use.
In addition to the engineering plastics, the high performance plastics have also secured a place in the food processing industry. These are normally found in applications where temperatures exceed the limits of traditional plastics. Materials such as PEEK can be used in constant temperatures of 480°F/248°C.

View the complete article online.

This article was written by Licharz GmbH.

Applications in food processing

The food processing industry includes meat packing and rendering, dairy, fruits, beer and beverage, ice plants, cold storage plants, bottling plants, bakeries, canning and food products machinery. Application opportunites for plastics are in both OEM and MRO.

While metal has been the standard, food-processing equipment builders and processing plants are looking to replace metal components because of a variety of issues, including chemical resistance, self-lubrication, wear properties, regulatory compliance and others. Additionally, stainless steel, which is used extensively, is very expensive, heavy and difficult to fabricate.

Applications include: sprockets, gears, starwheels, rollers, feed-screws, augers, guards, bushings, rail guides, bearings, wear and slide pads, fill tubes, heat seal insulation, roll covers, hopper liners, process piping and tubing, tanks, chain guides, cutting boards, sneeze guards, wall coverings, wheels, curtain stripping, flexible doors, door handles, packer fingers and manifolds.

For more ideas, there are many food processing application articles online at www.theiapdmagazine.com. Just check "food processing " when you search the archives to find them. There are also many other free resources on the IAPD web site at www.iapd.org.

Test your knowledge

What do you know about plastics in the food processing industry? (Answers are at www.iapd.org/popquiz.html.)

1. Acetal has excellent dimensional stability and extremely low moisture absorption, making it a good choice for applications in the food processing industry. What is another property of acetal?

  1. It is resistant to solvents.
  2. It is resistant to strong acids.
  3. It is resistant to oxidizing agents.
  4. It is resistant to strong caustics.

2. Which product is not available in a food-contact grade?

  1. Industrial laminate
  2. Acetal
  3. Nylon
  4. UHMW-PE

Online plastic resources

Your IAPD distributor is your choice in finding the right material for your application. Go to www.iapd.org to find a distributor in your area. You can search by company name, location or product category.

The IAPD Magazine web site at www.theiapdmagazine.com allows you to search by material, trade name and fabrication process. You can also search for fabrication capabilities.

Polymer Industries

© 2009
IAPD

International Association of Plastics Distribution
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Overland Park, KS 66209 USA
www.iapd.org | iapd@iapd.org
Phone: +913.345.1005 | Fax: +913.345.1006

Designing with Plastics is published by the International Association of Plastics Distribution. While every effort has been made for accuracy, IAPD encourages you to verify information with a plastics distributor to ensure you select the correct plastic products to meet your needs.