Primary chemical and physical characteristics of the materials used in manufacturing Kartell products. Plastics are organic materials created by man. Their technological and physical characteristics are determined by polymers, in which one or more types of monomers are joined to form a molecule. Plastics can be divided into two major groups based on their chemical and technological performance: Thermoplastic and thermosetting In recent years, technological research has made it possible to create increasingly sophisticated materials, whose performance and physical appearance are unlike that of what we generally consider as being “plastic”. These types of plastic contain not only polymers, but also additives, fillers and reinforcements which give them better physical, chemical, mechanical or processability properties. These are called composite materials or technopolymers.
Thermoplastics are formed by resins which can be made more elastic through heating or harder through cooling. The temperature values depend on each individual resin. They are composed of numerous interwoven independent molecular chains. When heated, these chains slide, enabling the plastic to flow. When cooled, they become hard again. Many thermoplastics are used in the production of Kartell products, and are almost always mixed with other materials to enhance their performance, thereby becoming thermoplastic technopolymers. The main thermoplastics used are Polyolefins, the best known of which are PE (Polythene or Polyethylene) and PP (Polypropylene), ABS (Acrylonitrile, Butadiene, Styrene), PS (Polystyrene), PMMA (Polymethylmethacrylate), PA (Polyamide) and PC (polycarbonate). Their main characteristics:
Polypropylene and polyethylene are thermoplastic polymers belonging to the family of polyolefins: Polyolefins are high molecular weight hydrocarbons. They include low-density (LDPE), linear low-density (LLDPE) and high-density polyethylene (HDPE), polypropylene (PP) and polymethylpenthene (PMP or TPX). Polyolefins are break-resistant, non-toxic and non-contaminating materials These are the only plastics lighter than water. They easily withstand exposure to nearly all chemicals. They are easy to color and modify to create specific alloys, using minerals like talc, as required for the product. Polypropylene (PP) is lightweight, translucent and strong. It has excellent mechanical and chemical resistance (it has no known solvent at room
temperature). It’s weather resistant, so it can be used to create products for outdoor use. Thanks to its features and its warm and soft physical appearance, polypropylene is particularly suitable for manufacturing chairs. Polyethylene (PE) is a chemically inert plastic. It has no known solvent at room temperature; aggressive solvents will cause softening and swelling, but these effects are usually reversible.
ABS polymers are a single technopolymer family. The name comes from the first letter of the three monomers composing them:
• Acrylonitrile (A) provides thermal resistance to aging;
• Butadiene (B) helps maintain properties at low temperatures, technical resistance, and impact resistance;
• Styrene (S) gives shine, solidity and ease of processing.
By varying the proportions of the three components, a wide variety of types of ABS can be created for a wide variety of uses: in the automobile sector, office equipment, electrical and electronic products, appliances, and naturally, furniture. ABS are resistant to high temperatures, chemical compounds and ageing, and are solid and impact resistant. They can be given high, medium and low (matte) gloss surface finishes and are easy to color. However, some types of ABS are sensitive to certain chemical compounds and solvents. Therefore, the anti-cracking properties need to be assessed for each application. ABS aren’t generally weather resistant. If the material is not protected, it may fade and become brittle. They are used for most traditional Kartell articles, such as round and square elements and modular bookshelves.
PS is the result of styrene polymerization. It is a rigid and non-toxic polymer with excellent dimensional stability and good chemical resistance to water-based solutions but limited resistance to solvents. It is ideal for products such as waste baskets and office articles. It is used in its so-called “aesthetic” version for its good surface appearance. It is also used as HIPS (scratchresistant polystyrene), with added rubber to make it scratch resistant.
Polymethylmethacrylate has high aesthetic and functional qualities. It is transparent, solid and weather resistant. Acrylic resins are used to make all transparent products, including in the furniture sector. So-called “plastic rubbers” can be added to improve their resistance properties, making it impact resistant. Antonio Citterio’s Mobil drawers are made of this special combination.
Polyamide Nylon Resins (PA6)
This is a group of linear polymers with repeated amide linkages along the back-bone. These are produced through the polymerization of amino acids. Nylon is strong and tough, abrasion, impact and wear resistant. Numerous fillers can be added
to improve its features. It is used for clothes stand bases or Oxo trolley supporting frames, parts which support weights.
Polycarbonate refers to a thermoplastic polymer. When producing objects using this material, the polycarbonate is melted and injected under high pressure into a mold, to give it the desired shape. There are two principal processes for producing articles with polycarbonate:
• Extrusion: here, the polymer is heated, then injected into a die with the shape of the final product. This process is used to manufacture pipes, sheets and profiles.
• Injection molding: here, the polymer in granular form is heated, injected into a mold, then cooled, giving it the shape of the final product. This is the most commonly used process for objects in a variety of sectors.
The Advantages of Polycarbonate
• Has excellent mechanical, thermal and electrical properties
• Has high resistance to fire and impacts, and high elasticity
• Easy to recycle and process
These characteristics make this material ideal for a variety of applications: from automobiles to packaging to appliances to consumer products. Kartell was a pioneer in the sector, demonstrating polycarbonate’s many applications in the furniture sector as well.
Polyvinyl Chloride (PVC)
PVC’s structure is similar to polyethylene, but contains atoms of chlorine. The chlorine atom makes PVC vulnerable to some solvents but also more resistant in many applications (PVC has a considerable resistance to oils and a very low permeability to gases). Polyvinyl chloride is transparent with a slightly bluish tint, and can be colored in a vast range of tones.
Styrene Acrylonitrile (SAN)
Styrene Acrylonitrile belongs to the family of styrenes, and is one of the best in terms of mechanical characteristics. SAN is rigid and hard,either transparent or opaque. Pieces made using SAN have a high dimensional stability and can be “easily” injection molded.
These resins can no longer return to their original state after they have been polymerized through heating or other means. Before transformation, thermosetting plastics also have a chain structure. During polymerization, atomic cross links are created between molecules, forming a complex interlinked network. These atomic cross links prevent the plastic from sliding during subsequent heating processes. Excessive heat damages polymers. The thermosetting resins used in Kartell articles are: PUR (polyurethane), SMC (Sheet Molding Compound), BMC (Bulk Molding Compound) and Melamine.
Polyurethanes are formed by two components, polyol and isocyanate, which when combined in different types and percentages form countless materials with differing and contrasting characteristics: from soft polyurethane used by the foam industry to the rigid structural variety, used to make the Battista trolley tops by Antonio Citterio.
Melamine resins–commonly called melamine–are thermosetting resins that are colorless and odorless, resistant to water, chemical agents, abrasion and heat, and are extremely transparent to light. Melamine resins are used primarily for tableware (especially dishes), plastic laminates and kitchen accessories. Melamine resin utensils and bowls are microwave safe, absorbing radiation and heat.
SMC AND BMC
These are thermosetting resins that are mixed with thermoplastic resins and impregnated with fiberglass. The difference between the two resins comes from the method by which they are impregnated: in SMC the resin impregnates a sheet of fiberglass, while in BMC the molding mass is impregnated with glass fibers. Fiberglass fill is used to create an especially resistant material, used in Philippe Starck’s Miss Balù table tops.
Fiberglass Reinforced Polyester (GRP)
GRP belongs to the family of thermosetting resins; it has high mechanical characteristics, so much so that it is also used in the automobile and electronics industries. Over time, two technologies have been developed allowing economical use of this material in mass-produced products: SMC (sheet molding compound), where the resin impregnates a sheet of fiberglass and BMC (bulk molding compound) where the resin impregnates disordered glass fibers. Thanks to these technologies and the material’s high mechanical characteristics (up to ten times greater than thermoplastics), highly technological products can be produced that are capable of replacing sheets and die-casting in many cases.
Natural wood is taken from the plant, either deciduous or evergreen, and is classified commercially as hardwood or softwood. Kartell uses some of the best wood available on the market. It is processed to guarantee long wear and resistance in addition to respect of all environmental standards. Since wood is a natural material, there can be color variations from piece to piece. The plastic laminate that is sometimes combined with wood is created through lamination and is composed of phenolic and melamine plastic resins and thermosetting polymers. It is used in the furniture manufacturing sector as a coating for chipboard, MDF, honeycomb and other wooden panels.
METALS AND PAINTS
In Kartell products, metals are limited mainly to structural parts or to emphasize particular aesthetic details. The technologies used are extrusion and die-casting. Often, to improve the surface and aesthetic quality, metal parts are painted: in this case using powder coatings are used, which can be electrically charged to adhere perfectly to the metal surface. The paints used for metal are usually epoxy polyesters. Thanks to their greater durability and resistance to light, abrasion and weather, the products made using these materials can be used outdoors. Die casting is used primarily to solve certain complex aesthetic issues, such as for the legs of the Battista and Gastone carts designed by Antonio Citterio. The die-cast parts can be used as is or coated with
On many plastic products or parts of products,more traditional paints, such as acrylic or polyurethanes are used. In this case painting serves to enhance the aesthetic quality of the
surface finish and improve durability.