Plastics Mould Technology

Plastic sheets and raw materials useful for industrial and business purposes

2011-04-25T21:38:00.000-07:00

Although the hue and cry from environmentalists is getting louder by the day, human kind is yet to find a replacement for plastics. Especially when it comes to manufacturing and packaging, polyethylene sheets and Acrylic plastic sheets seem to be unbeatable. Not only do plastics form the best protective covering but also are very cheap, when compared with other equivalent packaging materials.

Environmentalists and the people around the world should realize the plastics when handled with proper care can be as useful as nuclear energy. If the citizens understand their responsibility and act accordingly and help recycling of plastics then there will be no need for the slogans against plastics. Plastic bag manufacturers on their part have the duty to maintain the standards prescribed by the governments. In most cases governments of the world have been able to make manufactures of plastic bags comply with the international standards.

If you are involved in manufacturing and or packaging then it would be wise to have at hand a database of the suppliers, dealers, and agents so that you could procure your requirements at competitive rates. Thomasnet.com is a very useful website that provides a comprehensive list of suppliers ranging from Actuators to Zirconium. Check out the website for your industrial and business needs.

Surprise your kids with elegant gifts

2011-03-17T08:12:00.000-07:00

Wondering what to present to your little angels on their birthday? You don’t have time to shop around and yet you love to compare quality and cost of kid’s products? Yes you have rightly guessed! Online shopping can provide you with the luxury of purchasing good quality stuff at competitive rates. But then how to be sure about the quality? Well it is always wise to go for branded items and when it comes to kid’s products the name you will remember for life is Stephen Joseph.

You got visit the website to check out the variety of cute products designed especially for children. Every one of the product in the website is simply amazing to look at. Not only are they articles of beauty they are also highly useful for day-to-day purposes. Take for example the toddlers backpack available for sale in the website. It is made out of 100% quilted cotton and comes with awesome designs embroidered on it. The features such as magnetic swaps on the front flap, carry straps and shoulder straps are designed with an eye for perfection.

One other must view product on the website the personalized laundry bag. These laundry bags are very stylish and comfortable. Surprisingly the price range starts at a very low price ranging from $8. Apart from the regular designs available on display, you can also place custom orders of designs of your liking. Is it that a great boon! After all you avoid spending your precious time and money while you can pick your favorite items at competitive pricing. Any of the products including the nap mats or plastics moulded lunch boxes available at the website could be a great present to your toddler.

One other aesthetic website to visit is the Dallas landscaping services, which offers landscaping products and services at affordable prices. Do visit the websites by clicking the respective links and share your experience with us.

Plastic Moulding Innovation for The Smaller Company

2010-05-21T10:13:00.000-07:00

Everywhere you look in the world you can see and feel plastic. Its pivotal to our lives – it is hard to imagine life without plastic fantastic. No wonder plastic mouldings is a massive global business.

Approximately 30% of all plastic materials are manufactured by injection moulders. A very large proportion of this percentage is made through custom injection moulders technologies. The process of custom injection moulding is quite complicated to the uninitiated and requires a large amount of specialised machinery to make it happen. That is before the consideration of the selection of the raw materials which must be chosen for its quality and elasticy that depends on the end product being developed.

Given the wide-spread utilisation of plastic, there are many smaller companies that could benefit massively from plastic injection moulders as a way to produce parts. Given that the equipment needed is expensive, the overheads for developing new products is preventing companies from innovating.

Thankfully, for these smaller companies, there are organisations that specialise in custom plastic injection moulders. They will make a mock up mould to the exact specifications, run it through the complete process and present the completed product to the customer for analysis.

One such company serving the UK is Iota Sigma. If you are looking at developing cost effective plastic mouldings through the utilisation of injection moulders then Iota Sigma, a Wales based Plastic Mouldings manufacturer, can provide friendly and constructive advice. They can help develop products from the very first sketch through to custom rapid prototyping making a new concept for the enterprising company a low-cost reality.

Iota’s Sigma’s involvement early on in the development of a project can be a distinct advantage to the final finished product. They claim their professional approach in ensuring customer quality, materials, process to meet specific goals and their plastic mouldings knowledge utilising Injection Moulders are second to none. They are fully quality-driven and covered in the scope of their ISO9000 quality accreditation.

Article Source: http://www.articlesbase.com/industrial--articles/plastic-moulding-innovation-for-the-smaller-company-1445870.html

About the Author

Visit http://www.iotasigma.co.uk for complete details.

Plastic as a Source of Environmental Pollution What is the Solution?

2010-05-20T05:46:00.000-07:00

Plastic as a source of environmental pollution what is the solution?
Dr.Kedar Karki
Background:
Plastics are synthetic substances produced by chemical reactions. Almost all plastics are made from petroleum, except a few experimental resins derived from corn and other organic substances.

"Plastics" derived their name from their properties to be molded, cast, extruded or processed into a variety of forms, including solid objects, films and filaments. These properties arise from their molecular structure. Plastics are polymers, very long chain molecules that consist of subunits (monomers) linked together by chemical bonds. The monomers of petrochemical plastics are inorganic materials (such as styrene) and are not biodegradable.

Plastic has many properties which has made it a raw material of choice for Manufactures of plastic Bags and packing materials. Cost of production, light weight, strength, easy process of manufacture, and availability are few of the properties. There is nothing wrong with plastic as a material. Man has simply not put the plastic to the right use/ or using it without taking proper care of other related norms of usage.

PLASTIC AS PACKING MATERIAL:

Plastic has replaced the traditional material (paper/cloth etc) as packing and carry bags because of cost and convenience which is possibly a wrong choice of material for such use. Even though plastic bags can preserve food and can be used for growing vegetables in a controlled environment, their method of disposal has creates unprecedented pollution problem.

Plastic has many more uses other than Plastic Bags and Packing material. It is used for manufacturing of protective covers and parts for many machines, which should be the preferred utility for plastic.

SHOPPING CULTURE IN EARLIER DAYS:
Before the advent of poly-bags, people did shop, buy things, bring eatables from the market, and did the same marketing as is done now. How did they do it? The raw material for the bag was decided by its usage. Cloth bags for lighter items, Gunny bags/Jute bags for voluminous and heavier goods. The cost did not justify use and discard attitude. These bags were washable and reusable lasting for six months to a year.

Plastic and its Environmental Hazards:

The hazards plastics pose are numerous. The land gets littered by plastic bag garbage presenting an ugly and unhygienic seen. The "Throw away culture" results in these bags finding their way in to the city drainage system, the resulting blockage cases inconvenience, difficult in maintaining the drainage with increased cost, creates unhygienic environment resulting in health hazard and spreading of water borne diseases. This littering also reduces rate of rain water percolating, resulting in lowering of already low water levels in our cities. The soil fertility deteriorates as the plastic bags form part of manure remains in the soil for years.

It has been observed that the animals eating the bags sometimes die. Plastic goes into the ocean which is already a plastic infested body of water. Fish and other marine species in the water ways, misunderstanding plastic garbage as food items swallow them and die.

SHOULD PLASTIC BE TOTALLY BANNED?

Many household utility items like needle, scissors, and blades can heart if not handled properly. Children need to be trained in their proper handling. These utility items are not banned. But because of throw away culture and no objection from passer by, the advice on sensible disposal of plastic bags are not heeded by general public forcing the government to consider banning of plastic bags all together.

"Should plastic carry bags and bottles be banned in totality?" - is a heated issue today. World annual average is a alarming 18 kg. But too many do it as our cities have huge population. The country yet to take a serious view of the issue and have a uniform nation-wide law for indiscreet disposals of plastic bags. People should be educated on the proper ways of plastic bag usage and the disposal. The teaching should start right from the primary schools. Plastic is an eco-friendly material. The real problem is littering, some claim. But there is hardly anybody who agrees with such viewpoint.
Thinking rationally, the whole idea of educating people about plastic bags, although very ambitious, and it is as difficult as banning smoking The conventional older and tested alternatives offers an easy, if not fully equitable and practical solution.
And all the hype that poly-bags pollute is not totally false. It is not that poly-bags are responsible for the ills, of course not, it is the humans. It is ignorance (or who cares attitude). We have not banned sewing needles they pierce through the skin. It's a stupid idea. Whether it is the common citizen, the government official or the hard-hit plastic bag manufacturer, all of them agree on one point - firm steps are required to be taken against littering of plastic bags and bottles all around.

THE GLOBAL DIMENSION:

More than a 100 million tonnes of plastic is produced world-wide each year. Though plastics have opened the way for a plethora of new inventions and devices it has also ended up clogging the drains and becoming a health hazard. Many countries, including India, are trying to increase the amount of plastic that is recycled. But commercial interests create hindrance for effective legislation to remove plastics from goods where they can threaten public health. Also there is a clear trend of shipping off the plastic waste of developed countries to under developed and developing countries.
FUTURE ALTERNATIVE - ECO-FRIENDLY PLASTICS:

However newer technology is also being developed in this regard. This entails the use of DEGRADABLE PLASTICS. The principal is to incorporate into the plastic some chemical that is photodegradable/biodegradable or chemically treatable.

By adding starch, biodegradable plastics are generally made. On burial such plastics are attacked by bacteria feeding on starch, which breaks these down into tiny particles that disappear harmlessly into the soil. Some common examples of biodegradable plastics are the use of "non-removable" suture materials in surgery or capsules for drugs, which dissolve slowly in body fluids.

Chemically degradable plastics can be broken up by spraying them with a solution that causes them to dissolve. For example such material can be used as a protective wax covering for new cars that wash off at the dealer's garage by a specially formulated spray. This spray reacts with one of the components of the plastic and causes it to dissolve into harmless materials which can be flushed down the drain.

Photo-degradable plastics contain chemicals that slowly disintegrate when exposed to light. In France, strips of photo-degradable plastic about 3 ft (1mtr) wide are used to retain heat in the soil and produce early crops. They last for about 1 to 3 years before rotting into the soil. But they have to be used in places with consistent amount of sunshine so that they decay at a predictable rate. In the USA, about one quarter of the plastic yokes that link beer cans in a six pack are made of plastic called Ecolyte, which is photo-degradable. But to stop them decaying too early, they must be stored away from direct sunlight, which can be of some inconvenience to the retailer.

However degradable plastic can have a few other problems. For example, it cannot be recycled because there is no easy way to measure its remaining life span. The biggest drawback is the cost of its production. Japanese scientists however claim that they will soon be able to produce much cheaper multipurpose biodegradable plastic. In order to obviate the disposal problems and to prevent

Environmental pollution caused by routinely used polythene packaging materials; it would be prudent, for the present, to use eco-friendly paper packaging. The manufacturers of plastic packaging like soft drink bottles/mineral water bottles etc must come forward and develop appropriate methods of disposal/own responsibility for disposal.

Plastic bags are so light and strong that they can carry normal weight, cheap and is used in all types of shops in our daily life. For example: bakeries, medical shops, grocery stores, hotels, etc. People are so accustomed to it, that they find it very difficult to part with it. Plastic bags have made it possible for people to go without bags to market or work place as these bags are availably for asking and can be thrown without a second thought.

People who go on picnics, visiting historic places, hill stations etc., to enjoy their holidays or just for a change carry with them eatables in containers, plastic bags, mineral water bottles (plastic), plastic plates and plastic cups and generally leave it in the open air after consuming the contents. One can find this in tourist centres scattered all over. Road-side vendors also use plastic cups to serve coffee or tea. The customers throw these cups on foot paths or near drains after consuming the contents.

These plastic materials are so light that they are carried away by the speed of the moving vehicle, wind etc., scattered all over, making the surroundings look ugly. There are instances wherein these materials have clogged the underground drains. People are in the habit of throwing things they don't need wherever they like irrespective of the final result. People should be specially educated regarding the use of plastic in our daily life, as it is environment unfriendly. Boys and girls, men and women with bags on their backs and a stick in one hand walking long distances, picking up plastic waste, paper, bottles etc., from dust bins, road sides, is a common sight in our cities. These rag pickers sell the waste collected, to the collection centre to earn their livelihood. These materials are recycled.

The waste materials collected are of all types including plastic materials, such as plastic bags, plastic cups, plastic bottles etc. Instead of carrying these wastes away, they are burnt on the road side polluting the area with thick smoke which produce toxic gases (because of burning of plastic material) posing a health hazard. Inhaling of such gases causes lung diseases and even cancer. They resort to burning of waste material with the main intention of reducing the number of trips a lorry has to take. Plastic being non-degradable, when buried under the ground, arrest the percolation of water into the ground. Animals grazing in the field consuming this plastic waste along with grass cannot be ruled out. Now-a-days, in almost all functions, it has become a practice to use thin plastic sheets to cover the dining tables to give it a good look and also so that it is easy to clean the table, as left over can be removed by rolling the sheet at a stretch. These are thrown near the dust bin.

Besides this, thin plastic cups are also used for drinking water, which also finds a place in the dust bin. One can find near the dust bin, waiting slum children, crows, stray cows, dogs to share the leftovers. In this process, they fight amongst themselves and stray cows in majority of cases have consumed thin plastic sheets along with left over, leading to untold sufferings and also found dead on many occasions. It is therefore, suggested that a ban be placed on the use of plastic sheets, plastic cups, along with plastic bags. Plastic industries manufacturing plastic bags (below 20 microns) thin sheets, thin cups and thin bottles, should be informed about its ill-effects on the environment and advised not to manufacture such items. If the industry is located in a residential area, action should be taken to shift it immediately. The factory management should take all measures to control the pollution created, within the stipulated norms.

THE SOLUTION.

The solution lies in finding out:

1. Alternative suitable for making Bags and packing material at competitive rate and convenience without having any negative aspect.

2. Reaserch&Develpoment to make plastic more environments friendly.
3. Educate users to the right disposal methods.

4. Reduce the no of users by reducing the population in the long run.

5. Process vegetable, etc to higher density so as to reduce the no of bags required to pack and carry.

6. Encourage reusable bags from traditional materials by suitable advertisements to make it fashionable.

7. Cost of mfg bags with traditional material can be subsidized by printing advertisement on the bags.

Article Source: http://www.articlesbase.com/plastic-surgeries-articles/plastic-as-a-source-of-environmental-pollution-what-is-the-solution-610752.html

About the Author

Dr.Kedar Karki.M.V.St. Preventive Veterinary Medicine CLSU Philippines

Senior Veterinary Officer

Central Veterinary Laboratory

Tripureshwor

Kathmandu Nepal

Biodegredable Plastics - Transgenic Plants Providing a Solution

2010-02-08T09:58:00.000-08:00

Author: G.S.L.Susmitha, Namrata Sengupta

BIODEGRADABLE PLASTICS

- TRANSGENIC PLANTS PROVIDING A SOLUTION

Almost every product we buy most of the food we eat and many of the liquids we drink come encased in plastic packaging, which provides excellent protection for the product. It is cheap to manufacture and seems to last forever. Lasting forever, however, is proving to be a major environmental problem. Plastics are manufactured from numerous non-renewable resources like natural gas, coal, and oil. Plastics cannot be degraded easily in the natural environment due to their long polymer molecules which are too large and too tightly bound.

A type of sturdy and hard plastic is made with a molecule known as Bisphenol A, BPA. BPA like many other man made chemicals is now detectable in most people’s blood streams and could cause dangerous hormonal changes in children. BPA may tend to cause cancer, early puberty, obesity and even attention deficit disorder.

To overcome this problem BIODEGRADABLE PLASTICS have been developed which are made from renewable resources, such as plants. Biodegradable plastics are made with plant-based materials and result in 15% less carbon emission. Infact biodegradable plastics have not been successful in replacing the wide spread use of traditional petrochemical plastics.

The following are few items and the time required for their decomposition,

Tin cans- 50 to 100 years

Aluminum Cans- 80 to 100 years

Glass Bottles- 1 million years

Newspapers- 25 to 50 years

Polystyrene- 1000's of years

Plastic bags- 400 years

So now we know the raising alarm being caused in the environment by the use of plastics. But a solution is always there,

"Green Film" Plastic Bags and Products- 9 months to 5 years .

The plastics that are decomposed in the natural environment are known as the “biodegradable plastics”. (‘Biodegradable’ means that a substance can naturally decompose with the help of micro organisms and will not persist in the environment beyond a certain period of time). The chemical bonds of biodegradable compounds are easily destroyed by a variety of bacteria over a small period of time to facilitate their decomposition. As early as in the year 1926, Lemoigne managed to isolate the first of the polyhydroxyalkanoates – polyhydroxybutyrate (a homopolymer whose building unit is the 3-hydroxybutyric acid) from the Bacillus megaterium bacterium. At the end of the 1950s, the presence of the polyhydroxybutyrate was confirmed as an energy and carbon source and storage in many other bacteria. Many species of bacteria accumulate polyhydroxyalkonoates as energy storage compounds, some of the PHA polymers are commercially valuable as biodegradable plastics.

Polyhyroxybutyrate is a PHA produced in Ralstonia eutropha via three enzyme bio synthetic pathway consisting of ? – ketothiolase, aceto acetyl Co-A reductase, and PHB synthase. PHB synthase production in plants was first demonstrated in transgenic Arabidopsis thaliana. Polyhydroxy alkanoates (PHAs), e.g., polyhydroxybutyrate (PHB), are synthesized from acetyl-CoA used as precursor, and are used for the synthesis of biodegradable plastics with thermoplastic properties. At present, PHAs are produced by bacterial fermentation, and the cost of biodegradable plastic is substantially higher than that of synthetic plastics.

Attempts are being made to produce PHAs in transgenic plants to reduce the cost. Genes encoding the two enzymes, aceto-acetyl-CoA reductase (PhbB) and PHB synthase (phbC), involved in the PHB synthesis from the precursor acetyl-CoA have been transferred from the bacterium Alcaligenes eutrophus and expressed in Arabidopsis thaliana. When the two enzymes were targeted into the plastids, PHB accumulated in leaves. PHB production by transgenic plants provides an example of a novel compound synthesized in plants.

Standards that certify biodegradability and compostability,

Following international organizations have established standards and testing methods for compostability: American Society for Testing and Materials ASTM ASTM 6400-99

European Standardization Committee (CEN) EN13432

International Standards Organization (ISO) ISO14855 (only for biodegradation)

German Institute for Standardization (DIN) DIN V49000

The ASTM, CEN and DIN standards specify the criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable. While ISO 14855 makes no stipulations regarding disintegrations or toxins remaining.

Dealing with plastic wastes has taken on significance not far short of ultimate redemption. Developing biodegradable plastics is just one of the solutions to the existing problem. Its our responsibility to remember that by the uncontrolled use of plastics we are contributing our share to a deadly pollution whose ill effects are irreversible and capable of reaching out to numerous generation to come.

REFERENCES

1. Nature journal, Nature Biotechnology.

2.Crop science journal.

3. India Together, Science and environment and environmental plastics.

4. Australian Academy of Science.

5. Eco Greenwares.

6. abc NEWS – Health

7. Institute of science and society

Article Source: http://www.articlesbase.com/science-articles/biodegredable-plastics-transgenic-plants-providing-a-solution-602078.html

About the Author

Plastics Are The Best

2009-07-28T19:26:00.000-07:00

Plastics is one of the more commonly used materials for prototyping. Product development engineers, production consultants, inventors, special project leaders, and retail and production prototype specialist turn to plastics to create their moldings and prototypes.

These people know that plastic can be molded, cut and manipulated in any ways conceivable to create prototypes that would benefit the development of their products. Prototypes from plastic can be drop tested, tested for strength, sterilized, tested for consumer preference and durability, and can be put into actual use in no time at all at bare minimum costs.

With plastic prototyping, designers have different options at their disposal. Designers and developers can use rapid prototyping techniques which have tools like stereolithography, deposition modeling, laser sintering, laminated object manufacturing, and three dimensional printing at its forefront.

All these incorporates the basics of rapid prototyping, each technique creates individual parts from 3D-CAR models and joins them as layers until the final prototype is finished.

Using rapid prototyping techniques allows fast reproduction of prototypes regardless of the complexity of shapes.

However, it could be inexpensive at first but since each part is created individually, production costs may go up as the number of parts needed increases. Also, final output always have rough finish which brings the need to polish each part as they come out of their moldings.

An alternative is rapid injection molding techniques which incorporates the use of metal molds. This technique is able to create plastic parts that are fully functional and have a good finish. Since the molds are made of metal, they are able to support a wider range of resins and can come out as a lot cheaper than rapid prototyping or rapid tooling.

Regardless of the technique, the resulting plastic prototype should encompass the qualities of less production costs and more speed in production. The finished part also must adhere to certain standards.

Any prototype part must mimic the shape, size, finish and even color of the final production part. And any prototype part must at least be similar to the production part’s strength, chemical resistance, flexibility, durability and heat tolerance just to name a few.

Plastic is a very good material to create models which can be assembled, tested and used as close as the production parts.

Using the right prototyping techniques can save you time and money and allow you to simplify your production process, both for the prototype and the actual production unit. Remember that if the prototype is good, the final product could be good as well.

About the Author: Low Jeremy maintains http://Prototyping.ArticlesForReprint.com. This content is provided by Low Jeremy. It may be used only in its entirety with all links included.

Source: www.isnare.com

Permanent Link: http://www.isnare.com/?aid=156772&ca=Computers+and+Technology

Plastics Failure & Rubber Failure, Litigation & The Need For Long Term Durability Studies

2009-07-27T09:26:00.000-07:00

In an age of consumer champions, regulatory agencies and alert attorneys the plastics designer, manufacturer, fabricator and ultimate retailer are under drastic pressure to assure themselves, their customers, and the general public that their product can do what it is supposed to do throughout a prolonged life span and furthermore, do it in a safe and trouble-free manner. Whilst it is accepted that nothing lasts forever, the key to performance of plastics products is that it must remain serviceable for a reasonable life cycle, and failure must not occur in a manner that could jeopardise the equipment or individual it services. At the end of a useful service life it should ideally expire peacefully having no detrimental effect on its surrounding environment.

Plastics failure can cause economic and legal problems, as well as contributing to personal injury and death. The ‘owners’ of plastic products that have failed are, for obvious reasons, generally reluctant to publicise the fact. Failure diagnosticians tend to be restricted from doing so by confidentiality agreements and for this reason the activity is predominately covert. As a consequence the potential benefits such as learning from the mistakes and misfortunes of others, and identifying priorities for research and critical issues in product development are far from being fully exploited.

It is clear from the extent of plastic failures received by Rapra that this limited dissemination of plastic failure knowledge within the public domain has resulted in a continual cycle of plastic failure incidents from all industrial sectors. The lessons of good plastic product design are not being learnt even in light of the enormous growth in product liability cases that have imposed an entirely new dimension on the consumer product environment. It is now well established in law that manufacturers are liable for injuries resulting from defective product; for injuries from a hazard associated with a product against which the user should have been warned; or for damages caused by misapplication of a product which could have been foreseen by the manufacturer.

It is a practical necessity to understand why plastics fail in order to minimise the failure scenario. Rapra Technology has acquired this knowledge due to 80 years dealing with a diverse clientele providing technical services aimed at problem solving and in particular failure diagnosis.

Failure is a practical problem with a product and implies that the component no longer fulfils its function. Frequently, the ability to withstand mechanical stress or strain (and thereby store or absorb mechanical energy) is the most important criterion in service and consequently mechanical failure is usually a primary concern. However failure may be attributed to loss of attractive appearance or shrinkage etc.

The two main forms of mechanical failure are ductile and brittle failure. Ductile failure is, by definition, failure at high strain. It is relatively straightforward to design plastic components to avoid ductile failure. However, in practice, ductile materials often fail in a brittle manner, which becomes much more difficult to predict from a theoretical standpoint. Brittle fracture is a low energy process characterised by failure at low strain, with little or no deformation. Components contain small, crack like defects which can act as stress concentration features; these micro-cracks grow under load and may eventually lead to rapid catastrophic failure.

When considering the design and development of a plastic product it is imperative that a designer fully understands the fundamental limitations of plastics. A designer must be aware that plastics are:-

· Non-linear, visco-elastic materials

· Temperature dependant

· Materials that physically age

· Susceptible to chemical attack and environmental stress cracking

· They will, under the action of a tensile stress, eventually fail

· The time to fail will diminish as the stress increases

· The time to fail will diminish as the temperature increases

· The time to fail will diminish in the presence of certain environments

· The time to fail will diminish under the action of cyclic loading

· The moulding process can result in significant levels of residual stress in components

· Weld lines are planes of weakness, particularly in fibre filled materials

· Most plastics are highly notch sensitive.

· Mechanical anisotropy due to the alignment of fibre reinforcement

· Moulded articles rarely achieve theoretical material properties

Rapra’s experience has shown that many designers do not consider and / or are aware of these issues when considering the use of plastic materials. We have designers who can design but have no real appreciation for the material they are proposing to use. Rapra has found that Poor product design is endemic to all plastic sectors including the medical, pharmaceutical, automotive, rail, aerospace, packaging, oil / gas, energy, engineering and construction industries.

More than 5,000 failures have been the subject of study at Rapra. Interestingly the number of failures evaluated has increased significantly during the past five years.

Rapra Technology Plastic’s consultancy provides a range of services which allow engineers to prove designs at an early stage, ensuring that their product will be right first time inclusive of finite elemental analysis (FEA - ABAQUS), material selection (Plascams), evaluation of design aspects, injection mould simulation (3D Sigma), long term durability studies (creep, creep rupture, fatigue and actual product endurance testing.

A key to good plastic product validation is the generation of durability long term performance data. It is essential that designers and manufacturers of plastic products understand that short-term data provided by material manufacturers is useful only as a comparative guide between generic and sub-generic groups and cannot be used to gauge material performance in the long term.

In order to provide confidence that a plastic component will perform in the long term a prediction of failure stress in time under simulated in-service conditions i.e. temperature, environment is strongly recommended. Predicted long term data can then be correlated with 3D Sigma / FEA calculated residual and operational in-service stresses to determine a safe working life time for the product. Ideally testing of actual components is preferred so that the effects of possible moulding defects, moulded-in stresses etc can be assessed. However, due to complex component geometries and sizes this is not always feasible and subsequently material test specimens are tested.

Typical long term mechanical failure mechanisms resulting in catastrophic brittle cracking include creep rupture, fatigue i.e. cyclic stressing and environmental stress cracking which are discussed as follows:

Creep Rupture

Over a long period of time at constant load, most polymers will creep, causing failure. An aggressive environment accelerates failure. Creep rupture analysis generates a time to failure data for different constant stress levels. This data can be used to predict the life of a component and can be used in design calculations.

This method generates a time to failure curve for static creep at different stress. The data can be used to predict the effective life of a component where it is continually loaded under static conditions. The test can be carried out in aggressive environments to simulate operating conditions. Each test at an individual stress level is run for a maximum of 1000hrs.

For longer-term predictions, tests are carried out at elevated temperature. Then, data is predicted using time-temperature superposition techniques. Time temperature superposition is a well-established technique that is used extensively in the assessment of the long term (50 year) design stress of plastic pipes ISO 1167, BS EN ISO 9080.

These curves are then shifted to fit “by eye”, T5 to T4 and T5 + T4 to T3, etc. and a common shift factor found that can be applied to all of the data generated to produce a long term master curve at the required temperature.

The master curve can then be used to establish the failure stress (sf) of the material in the environment at the service temperature and at the desired life of the component.

Dynamic Fatigue Testing

If the component is subjected to any form of cyclic loading, then fatigue failure will be prominent, especially when there is an aggressive environment. Most plastics undergo a ductile to brittle transition during fatigue. Therefore, after a number of cycles, the fatigue strength dramatically drops. An ESC agent can make the transition more dramatic or occur after less cycles.

Fatigue testing is carried out at a relatively slow cycle rate (typically 0.5-1Hz). The number of cycles to failure (to a maximum of 106 cycles) is determined for different stress levels. The resulting curve can be used to predict the life of a component if the cyclic stress can be measured or calculated. In many cases the maximum permitted stress in a plastic component is significantly lower than expected from FEA calculations. High frequency cyclic loading measurements are erroneous since heat is generated causing the material to be plasticised.

Fatigue testing can be carried out at elevated temperatures and in aggressive environments. For longer-term predictions, tests are carried out at elevated temperature. Then, data is predicted using time-temperature superposition techniques. Samples can be tested in tension or compression and also with a cyclic load on top of a baseline load or a cycle through compression and tension.

Summary

The causation of plastics failure has many forms, most of which would be pre-empted by undertaking a thorough plastic feasibility study to ensure attainment of at least adequate product quality.

This article is free to republish provided the resource information remains intact.

Contact Dr Chris O’Connor (Plastics, Rubber & Design Technical Solutions Manager). Tel. 01939 252423. Email coconnor@rapra.net

http://www.rapra.net/website/Plastics_Consultancy/Plastics_Rubber_Failure_Litigation_need_for_long_term_durability_studies.asp

Article Source: http://EzineArticles.com/?expert=Chris_O’Connor

Injection molding

2009-07-04T01:20:00.000-07:00

Injection molding is one of the many manufacturing processes for producing objects using thermoplastics. In injection molding process thermo plastics pellet form is fed into a heated barrel, mixed, and forced into a mold designed specially for the purpose. Once the mould is filled with the material it is cooled to harden then ejected from the cavity.

This involves various processes from designing a injection mold to processing the plastics to form the required component. There are various forms of injection molding. To learn more about various kinds of injection molding and problems encountered during the process visit the site often.

Two Types of Plastics

2009-05-12T07:23:00.000-07:00

The world of plastics can be broadly classified into two types, thermo plastics and thermosetting plastics.

Thermo plastics are those that can be molded again and again. That is, under heat and pressure these types of plastics can be molded into desired shape any number of times, however, with a slight difference in quality. Good examples of thermo plastics include LDPE, HDPE, PP, and the like. The buckets you use, plastic covers, and plastic balls are all made of thermo plastics. One good quality of this type of plastics is that they can be safely recycled without any major damage to the environment.

Thermosetting plastics on the other hand are those plastics that can be molded to desired shape under pressure and heat but cannot be remolded like thermo plastics. Products made out of thermosetting plastics if damaged or broken can only be dumped in the waste yard. This type of plastics does not degrade easily and cause serious trouble to the environment. Good examples include the melamine ware commonly used as kitchen utensils.

All About Plastics

2009-04-22T13:41:00.001-07:00

This blog is intended to provide useful articles on plastics right from plastics mould design, plastics processing, plastics recycling, plastics testing, and bio-degradable plastics. Watch out of fantastic post on latest technologies.