Many clients throughout the San Mateo area have heard the term vacuum forming, but they do not know what it really means, and they don’t know what it does or how it can help them in their business. Vacuum forming is a procedure that can shape performance plastic sheet materials into many different forms, and it is one of the best ways to make a host of different plastic products.
How Does it Work?
A type of thermoforming, vacuum forming, is a process by which a plastic sheet or thin sheet of plastic, such as a PVC sheet, is heated up so that it becomes malleable. The heating process includes the use of aluminum plates and infrared heaters. The heat application will come from the top and the bottom so that it is uniform and will provide the best results.
Once the heat finally reaches the proper temperature (which can differ based on the thickness of the sheets in use) the vacuum will mold the sheets to form the product. The vacuum is able to provide an airtight environment, which is going to be better for the overall molding process.
Products from Vacuum Forming
With this type of thermoforming, one could create countless types of products, and you may find that your company could benefit greatly from the process. One of the most common products using vacuum forming today are children’s plastic toys, but that’s just one of the possibilities. Product packaging is another option, and it is one most companies that create, manufacture, package and sell products could use. Most of the plastic items that you see around the home and office have gone through some type of thermoforming, and it’s often the vacuum process.
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Plastics cover a broad field of organic synthetic resin and may be divided into two main classifications - aerospace thermoplastics _ and aerospace thermosetting plastics. Thermoplastics may be softened by heat and can be dissolved in various organic solvents.
Thermoplastics may be softened by heat and can be dissolved in various organic solvents. Two kinds of transparent thermoplastic materials are commonly employed in windows, canopies, etc. These are known as acrylic plastics and cellulose acetate plastics. Cellulose acetate was used in the past but since it is dimensionally unstable and turns yellow after it has been installed for a time, it has just about passed from the scene and is not considered an acceptable substitute for acrylic. Acrylic plastics are known by the trade names of Lucite or Plexiglas and by the British as Perspex and meet the military specifications of MIL-P-5425 for regular acrylic, MIL-P-8184 -~ 184 for craze-resistant acrylic.
Aerospace Thermosetting Plastics.
Thermosetting plastics do not soften appreciably under heat but may char and blister at temperatures of 240 to 260 'C (400 to 500 °F). Most of the moulded products of synthetic resin composition, such as phenolic, urea-formaldehyde, and melamine formaldehyde resins, belong to the thermosetting group. Once the plastic becomes hard, additional heat will not change it back into a liquid as it would with a thermoplastic.
Storage and handling.
Because transparent thermoplastic sheets soften and deform when they are heated, they must be where the temperature will never be excessive.
Transparent acrylic plastics get soft and pliable when they are heated to their forming temperatures and can be formed to almost any shape. When they cool, they retain the shape to which they were formed. Acrylic plastic may be cold-bent into a single curvature if the material is thin and the bending radius is at least 180 times the thickness of the sheet. Cold bending beyond these limits will impose so much stress on the surface of the plastic that tiny fissures or cracks, called crazing, will form.
Simple Curve Forming. Heat the plastic material to the recommended temperature, remove it from the heat source, and carefully drape it over the prepared form. Carefully press the hot plastic to the form and either hold or clamp the sheet in place until it cools. This process may take from ten minutes to one-half hour. Do not force-cool it.
This type of forming is normally used for such parts as canopies or complex wingtip light covers, and it requires a great deal of specialized equipment. There are four commonly used methods, each having its advantages and disadvantages.
Stretch forming. Preheated acrylic sheets are stretched mechanically over the form in much the same way as is done with the simple curved piece. Special care must be taken to preserve uniform thickness of the material, since some parts will have to stretch more than others.
Male And Female Die Forming. This requires expensive matching male and female dies. The heated plastic sheet is placed between the dies which are then mated. When the plastic cools, the dies are opened.
Aerospace Vacuum Forming Without Forms. Many aircraft canopies are formed by this method. In this process a clamp with an opening of the desired shape is placed over a vacuum box and the heated sheet of plastic is clamped in place. When the air in the box is evacuated, the outside air pressure will force the hot plastic through the opening and form the concave canopy. It is the surface tension of the plastic that shapes the canopy.
Aerospace Vacuum Forming With A Female Form. If the shape needed is other than that which would be formed by surface tension, a female mould, or form must be used. It is placed below the plastic sheet and the vacuum pump is connected. When air from the form is evacuated, the outside air pressure will force the hot plastic sheet into the mould and fill it.
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If you're shopping around for plastic tableware, you've no doubt seen that plastic glasses and dishes come in a vast array of styles, types and even qualities these days. Since each promises a different set of features and benefits, choosing the right plastic tableware may seem a daunting task. But don't despair! Here are a few tips to help you decide which type of plastic best meets your needs, and how to know exactly what you're buying.
Tip 1 - Don't just shop for "plastic," because not all plastics are created equal:
So true! Ever had indestructible plastic glasses that last from year to year, while others break the first time they're dropped? How about plastic dishes that scratch like crazy after a few uses? What about plastic plates that overheat after just seconds in the microwave -- or glasses that clouded in the dishwasher?
Though frustrating, these common issues aren't really defects in the plastic, they're just differences. More than a half-dozen types of plastic are used to make tableware - from unbreakable Tritan and budget-friendly SAN, to scratch-resistant Melamine and decorative Acrylic. Each offers its own benefits and drawbacks.
Knowing how different plastics perform and how to tell them apart when shopping can ensure that the plastic dishes, glasses and serving pieces you choose best meet your needs. Tips two and three will help you do just that.
Tip 2 - Decide on the features that matter to you before shopping:
Shopping for plastic tableware would be a cinch if a single plastic offered it all -unbreakable, scratchproof, dishwasher and microwave-safe. Unfortunately, that plastic is not yet invented. So of the plastics that do exist, which option is right for you?
Do unbreakable, dishwasher-safe products top your list? If so, spending a little more on unbreakable Tritan or Polycarbonate plastic items is well worth the years of use you'll enjoy. For a little less, SAN plastic products are almost as durable, and casual looks in Polypropylene are equally durable and very inexpensive. Avoid anything in Acrylic or Polystyrene.
Are scratched dishes your pet peeve? Then Melamine dishes are your best choice for long-term satisfaction. But you'll have to forego the convenience of microwave heating.
Are microwave-safe dishes a must? The selection is slimmer, but there are some choices in plastics made specifically for the microwave. Look for dishes under the brand names Nordic Ware, Miracleware and ExtremeWare - and avoid products made from Melamine, Acrylic and Polystyrene.
Are you drawn to decorative or themed dishes? Trendy designs and seasonal themes are widely available in plastic tableware. Very decorative glasses are generally crafted in Acrylic, but be prepared to hand wash to keep them looking their best. You'll also find plenty of decorative and themed designs in durable easy-care Melamine dinnerware.
Is cost more important than longevity? Inexpensive seasonal Acrylic and Polystyrene tableware is plentiful on store shelves. But with plastics, you do get what you pay for. These low-cost styles won't hold up under impact or in the dishwasher for much more than a season or two.
Tip 3 - Know what you're buying - even if the label doesn't tell you:
You now know that the plastics used to make tableware vary indeed, and which type best meets your needs. So how do you tell if a plastic glass is made of SAN or Acrylic? How do you spot Melamine dishes? And what the heck is Polypropylene, anyway?
If shopping online with a reputable seller, product information will include plastic types, features and care. If it doesn't you may want to shop a different site as the seller may not know, or stand behind, their product. In-store shopping can be a bit trickier because not all plastic products are clearly labeled by type. There you'll need to know a bit more than the label tells you.
Unbreakable products in Tritan and Polycarbonate plastic are easy to identify because they're generally labeled as "Unbreakable" and "Dishwasher-safe" to offset their higher price tag. Tritan items are also labeled "BPA-free." Both plastics are generally found in glass-like clear or tinted drinkware and dishes.
Unbreakable, dishwasher-safe products in Polypropylene plastic are easy to identify, too. They're always opaque or semi-opaque, think Tupperware, and have a rubbery feel unlike any other plastic. These products also tend to be low-priced.
Labeling on Melamine dishes varies, but that's not a problem if you know what to look for. All melamine dishes are opaque - never see-through - and have a rigid feel. Because of melamine's durability and scratch-resistance, it's the most common plastic used to make dishes and can be found in a huge variety of colors and decorative designs. Melamine dishes are dishwasher-safe, but not microwave-safe, so melamine dishes are almost always marked "Not Intended for Microwave Use."
Plastic dishes and cookware made from microwave-safe plastics are always clearly labeled "Microwave-safe" because that's their major selling point. These items are always dishwasher-safe and sometimes oven-safe, too.
Glasses and dishes made from Acrylic, Polystyrene and SAN plastics are rarely labeled by type, but you can tell them apart. Though shatterproof, they're not truly unbreakable, so you won't see that on the label. The major difference is the care. SAN plastic products are dishwasher- and microwave reheat-safe, and usually labeled as such. Polystyrene products are generally labeled "Top Rack Dishwasher-safe," while Acrylic products are almost always "Hand Wash."
Tip 4 - Care matters! Enjoy your plastic tableware for years:
As plastics differ so does their care, but you can extend the life and looks of even the least expensive products if you treat them right.
In the dishwasher, a good rule of thumb for any plastic glasses - even those marked "Dishwasher-safe" - is to wash on a normal, unheated cycle. Some dishwashers heat water excessively in certain cycles, so a normal setting is always the best bet.
Items labeled "Top Rack Dishwasher-safe" should be placed in the top rack, away from the heating element at the bottom - with one exception. Some Melamine dishes are labeled "Top Rack Dishwasher-safe," but they won't fit in the top rack. These are fine to wash in the bottom rack on an air-dry setting.
Items labeled "Hand Wash" really should be washed by hand. These products will quickly crackle or cloud if exposed to dishwasher heat and detergents.
Abrasive cleaners or scrubbers should not be used on any clear plastic glasses or plates as they will, without exception, scratch. Melamine plates hold up to most scrubber sponges.
Tip 5 - Ignore the #7 recycling symbol - it doesn't identify specific plastics:
Last, save yourself some shopping frustration. Don't rely on recycling numbers - those little numbers in a triangle on some plastic items - to identify plastics. In fact, these numbers don't even appear on many plastic tableware items. Why? It's simple, they're not disposable.
Recycling numbers, officially known as SPI codes, are intended to identify commonly disposed plastics so they can be efficiently recycled - that's all. The #7 code is a catchall number used for the non-recyclable plastics - and that includes many plastics used to make long-lasting tableware.
Contrary to some media stories, the #7 code does not denote an unsafe plastic. Anyone suggesting that all plastic items with the #7 code are unsafe because they contain the chemical BPA simply did not do their homework. Most good-quality plastics, including Melamine, Acrylic, SAN, Tritan and even biodegradable Eco-plastics all fall under the #7 code, and not one of them contains BPA.
Polycarbonate is the only tableware plastic that contains BPA. If media reports on BPA concern you, just avoid polycarbonate products. Products made from Tritan plastic offer the same benefits as polycarbonate, without BPA.
So whatever your tableware needs, from unbreakable plastic glasses for outdoors, to durable dishes for everyday, to decorative styles inspired by the season, there's surely a plastic available that meets your needs. Armed with these tips, you shouldn't have any problem finding it.