Posts Tagged ‘plastic’

The Progress of Biopolymers

Sunday, July 11th, 2010

For any reader who isn’t aware, most of the world’s plastic is currently made from crude oil. The process involves several steps, depending on the polymer that one is creating, but the total cost is still a fraction of the cost needed to create biopolymers of the same quality. Biopolymers are created by having a culture of bacteria consume large amounts of biomass. When the bacteria are mature, the culture is sterilized and the biopolymer is extracted directly. Many factors are now causing chemical and plastic companies to consider possible ways to reduce their reliance on crude oil, so reducing the cost of biopolymer production has become a greater priority. Since the polymer-using world cannot simply pay double or triple for things like plastic bags, plastic bottles, and plastic tubing, achieving this cost reduction is the missing critical factor to wide scale use of biopolymers.

The difference in cost between standard polymer production and biopolymer production is not caused by any one factor. Since the world uses such a large amount of plastic, existing polymer production facilities are huge, whereas biopolymers are mainly produced by small specialty groups and laboratories. Several companies are now considering the construction of large scale biopolymer factories, but they are waiting on the researchers to bring down the other areas of cost first. At present, it requires 3 times the weight in biomass to create a unit of biopolymer. This is because the bacteria being used are only able to consume certain nutrients from the biomass, leaving the rest behind as unusable waste material. Efforts are underway to find or engineer a more efficient bacteria for this task. The other side of the coin is to more effectively process the biomass such that a greater portion of it is consumable by the bacteria. Many different areas of research are currently being conducted toward this achieving this end, because labs and universities know the impact of these discoveries will be felt for centuries to come and the shorter-term breakthroughs could easily lead to a Nobel prize.

Plastic’s Place in the Biosphere

Tuesday, March 16th, 2010

Since it first came into wide-scale industrial use in the mid 1930s, polyethylene has been chosen as the preferred material for many applications. Most of these applications came about because polyethylene is low-cost, heat resistant, acid resistant, insulant and slow to biodegrade in nature. Among these properties, the last has proven to be more of a double-edged sword as each year we continue to produce 80 metric tons and the environment breaks down far less. Recent progress on biodegradable polyethylene has presented a partial solution, but many of the most common applications simply weren’t intended to rot under natural conditions. Most forms of tubing and cables only function effectively so long as they remain completely intact. The same can be said for most plastic car parts, electronic casings, food and drug containers, and many others.

Until recently, recycling remained our first and only effective strategy for sustainable use of “non-biodegradables”, but in 2008 it was discovered that a variety of bacteria called Sphingomonas can degrade polyethylene molecules. Since polyethylene does biodegrade very slowly in nature, a Canadian science fair student named Daniel Burd was able to isolate and eventually concentrate the specific microorganism(Sphingomonas) responsible for the breakdown. Though the right concentration does not exist in nature, high volume Sphingomonas can break down plastic in a few months instead of the 1000 years it takes now. It should also be noted that this organism is unaltered at present, though many companies are now proficient at bioengineering bacteria for specific purposes. In the future it may be possible to breed varieties of Sphingomonas that are even more effective at breaking down polyethylene and other types of plastic.

The Most Widely Used Plastic in the World

Tuesday, March 16th, 2010

With so many varieties of plastic tubing to choose from, a design engineer has many difficult choices to make when prototyping a new medical device. Of all the materials used for such applications, polyethylene most often leads the way.

Introduced to the world of manufacturing at the time of FDR, polyethylene has since made many applications easier to manage, safer for consumers(compared to earlier metal counterparts), and cost-effective enough to mass-produce.

When choosing a type of polyethylene, mechanical factors always come first, because they are the basic requirements needed for a design to function. Fortunately, polyethylene is extremely versatile and most mechanical requirements can be met with many possible formulas. Cost must also factor into the decision, as all consumer products have a price point which limits their allowable manufacturing cost. Understanding the properties of the different grades can assist a design engineer in the selection of thermoplastic materials for products that use custom plastic tubing.

LDPE(Low Density Polyethylene) – The first invented grade of polyethylene, LDPE remains the most commonly used density. In addition to being useful for plastic tubing, LDPE is also used for plastic bags, food storage, computer/car components, general purpose containers, and many other things. While it has a lower tensile strength than the higher density grades, it has a higher resilience(maximum energy per unit volume that can be elastically stored) which makes it very flexible.

HDPE(High Density Polyethylene) – While it has many of the same applications as LDPE, it is harder, more opaque, and somewhat more resistant to heat and chemicals. It is often used for outdoor scenarios where there is a large temperature range as well as containment scenarios where chemicals need to be isolated from the environment over a wide area.

LLDPE(Linear Low Density Polyethylene) – Slightly harder to process than normal LDPE, LLDPE has higher tensile strength, impact resistance and puncture resistance. Basically this means that a thinner layer of plastic can remain intact under flexibility testing. Its primary use is in flexible tubing, but it is also used for plastic wrap, toys, lids, cable coverings and more.

UHMWPE(Ultra High Molecular Weight Polyethylene) – More expensive than most other grades of polyethylene, UHMWPE has the highest impact strength of any thermoplastic presently made. It is often referred to as high performance polyethylene and is typically reserved for “unbreakable” scenarios like artificial bone replacements, bulletproof vests, etc.

VLDPE(Very Low Density Polyethylene) – Because VLDPE is characterized by even lower heat resistance than LDPE, it is often used in packaging for frozen food and ice. Some tubing and stretch wrap is also made from VLDPE and it is commonly blended with other polymers as an impact modifier.

PEX(Cross-linked High Density Polyethylene) – PEX is almost exclusively used for long-term tubing scenarios. Many thermal properties of the plastic are improved by the cross-linking process. It maintains strength at a higher temperature and reduces flow. Under low temperatures, impact resistance, tensile strength and scratch resistance are improved. Cross-linking also improves the chemical resistance.

Have it your way—but can it be manufactured?

Tuesday, March 16th, 2010

Unless you’re a design engineer of custom made tubing you may not be as curious as to how custom tubing is made, or why it is important to consider custom tubes specifications closely before embarking on the manufacturing process.

More often times than not, tube designers push the manufacturing envelope when they design custom made tube with requirements that are not necessarily advantageous for the products intended use. It’s not intentional to make the manufacturing process of custom tube more difficult, rather a goal of developing the perfect end product.

But what they should be asking themselves during the design phase is, “what are our critical requirements for this product?” Otherwise, what is often realized too late can be costly and also cause delays in production of the custom made tube. To avoid such stumbling blocks, there are several criteria that tube designers should consider during the custom tubing planning process:

  • Material specification – have you considered the best thermoplastic suited to the application of the custom made tube?
  • Configurations – are your design specifications realistic so that the custom tubes can be manufactured?
  • Manufacturability – is your design dimensions and tolerances feasible and would you consider re-evaluating your tolerances to facilitate the process of making a high quality custom made tube more efficiently?

From the time that plastic was first introduced into mass production, custom tubing companies have been afforded the opportunity to create a myriad of products from extruded plastic rods to single-lumen tubing. And like the world of imagination, custom made tubes have endless possibilities—but proper planning will make it a success.

The Reliability Factor of Custom Tubing

Tuesday, March 16th, 2010

The importance of small diameter custom tubing can be as easily overlooked as the necessity of a pen cap—unless you’re the end user in a life-saving capacity who depends upon the custom tube to function reliably to help you do your job.

While a pen cap is obviously less mission-critical than that of custom tubing, of course, the principals are the same. For a product to perform properly, it is imperative that all the components are of the highest quality to ensure it meets those standards of performance.

For equipment that requires custom tubing–whether it’s a custom tube utilized in a cardiac catheter packaging that may later be inserted into a patient’s heart to keep him alive or custom tubes used in pharmaceutical lab equipment to dispense liquid. The custom tube must meet numerous quality standards, in this case, to be puncture and wear-resistant, flexible, and act as a protective barrier to outside elements that could compromise its function.

People would be surprised to learn about how much design, planning and quality control goes into manufacturing these perfectly cylindrical, small diameter custom tubing; and how each custom tube is manufactured to maximize performance depending on the specific application.

Is the custom tube for a one-time use? Will it be exposed to heat? Which type of thermoplastic should the custom tube be manufactured in – PVC, Nylon, or Tecoflex™?

From medical facilities to electronic companies– numerous industries depend upon manufacturers who specialize in small diameter custom tubing, companies like A.P. Extrusion who work with their customers to ensure quality is never compromised.