sergio antonio salvi, laminar flexible materials (lecture extract)

LAMINAR FLEXIBLE MATERIALS

Sergio Antonio Salvi

PRODUCT DEVELOPMENT

AND MANUFACTURING

TECHNOLOGIES

LAMINAR FLEXIBLE MATERIALS:

“LAMINAR FLEXIBLE MATERIALS” CLASSIFICATION

PRODUCT DEVELOPMENT AND MANUFACTURING TECHNOLOGIES


As “laminar flexible materials” in this conference can be meant those semifinished materials who present the “dimension Z” (namely the thickness) estremely reduced, so that they are very flexible, so flexible to be considered “functional materials”, since they are not properly “structural” ones; because of their main characteristic, they are mostly used as coating and for containing.

Hence in this class can be mentioned the following:

■ leather;

■ fabrics;

■ “non-woven” fabrics;

■ polymeric films and correlated “multilayer” films.

LAMINAR FLEXIBLE MATERIALS :

LEATHER: definition, importance in the past and criticity of contemporary application Semifinished materials of “leather industry”, related to the so

called “leather goods” sector, “furs” included, are tecnically all defined “leather”.

In this conference, even if the importance of leather in the human history and evolution it is recognized, this raw material, and its derivatives, is not eligible as “reference material”, considering the consequences that the use of leather determines in terms of “sensitive” animal sacrifice; this point of view has been widely discussed in the contexts of “animalist” and “ecosofy” cultures (cf., among others, the writings of Singer and Naess respectively).

Because of the above mentioned notes, leather in this conference is not treated.




TEXTILE FIBERS: classification

Textile fibers are foundamental to produce fabrics, “non-woven” fabrics and sometimes “reinforced” polymeric films.

Generally, they can be classified into four great categories, depending on their origin, who can be:

■ animal;

■ vegetal;

■ mineral;

■ artificial and synthetical.




TEXTILE FIBERS: ANIMAL ORIGIN fibers

Animal origin textile fibers principally are wool and silk. As known the former is got by the animals fur, especially ovines (from a point of view, this production origin is the same of the leather one), and the latter is derived by the silkworm.

These fibers, in spite of the concurrency of the vegetal ones as well as the advent of synthetic, preserve a certain market. Surely their production strongly depends on the breeding of the animals who generate them (think of the mullberry tree colture, whose leaves is the nutrition of silkworm, so flourishing in north Italy until the middle of the last century).




TEXTILE FIBERS: ANIMAL ORIGIN fibers

The silkworm at the larval state and its cocoon




TEXTILE FIBERS: VEGETAL ORIGIN fibers

Industrially used vegetal origin fibers are much many than the animal origin ones. Their raw materials are pratically extracted by any vegetal organism. The most common are cotton (got by its pod), flax (bark), hemp (bark), jute (bark), raffia (leaves), ramié (bark), nettle (bark), hibiscus (bark), broom (bark), manila (leaves), sisal (leaves), coconut tree (fruit), rubber tree (latex) and others are plants coltivated for the purpose.Also vegetal origin fibers suffer from synthetic ones concurrency, anyway their market is much more wide. It is important to note that their production concerns the soil exploiting and strongly depends on their coltures, so that they compete with other productions, often related to the human feeding...






TEXTILE FIBERS: VEGETAL ORIGIN fibers

a cotton field

Mineral origin textile fibers are basically the ones who can be derived by metals (aluminium, silver, gold), glass –and silicates–, carbon –graphite included– etc. Asbestos fiber, due to its toxicity, is unused.

Metals, glass and carbon, together with their similar, by means of special “spinning” procedures can be reduced into “threads”. These fibers are used in special applications, like in the “composite materials” field where both glass and carbon fibers are far important.




TEXTILE FIBERS: MINERAL ORIGIN fibers




TEXTILE FIBERS: MINERAL ORIGIN fibers

a glass fiber “strand”

These textile fibers are divided into two categories: the artificial origin fibers are those “chemically” transformed by “natural” polymers (already existing in nature; for example viscose, derived by cellulose as well as many other of either animal proteins or vegetal proteins origin); the synthetic origin fibers instead are based on the chemistry of polymeric materials (the typologies are uncountable and coincide with the polymers families: PET, PA, PP, PUR etc. in the various trademarks like, respectively, Terital, Nylon, Meraklon, Elastane etc.).




TEXTILE FIBERS: ARTIFICIAL AND SYNTHETIC ORIGIN fibers

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Polymers for their nature are macromolecules who can have a very high molecular weight –such as “length”– so that they can be “molecular fibers”. While considering the historical role of the artificial fibers, synthetic ones present the enormous advantage to be designed at molecular scale, furthermore in their fiber “section” (like in “hollow fibers”); the result is the adaptability to many applications; moreover they do not need any dyeing (they are coloured “in mass”) and can be modified with infinit additives; because of that potential the so called “technical suits” are almost always made by means of synthetic fibers; in the future “nano-fibers” could allow amazing characteristics.





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experimental polymeric “hollow nano-fibers"


FABRICS: fabrics classification

There are many ways to classify fabrics, anyway the most used is that based on the shape of thread “intersections”, that is the result of either the weaving machine “weave”, or the particular production technique type; therefore the following main fabrics can be distinguished:

■ fabrics with rectilinear threads, also known as “woven warp loom” (e. g. the so called “denim”);

■ fabrics with rectilinear “fabrics work” threads, also known as “Jacquard” (e. g. the “damask”);

■ fabrics with curvilinear threads, also known as “knitted fabrics” (e. g. the “jersey”);

■ fabrics with knotted threads, (e. g. the “nets”).



Fabrics with rectilinear threads are also known as “woven warp loom”, because they are produced by means of the classic weaving machine. In this machine the “heddles” are fundamental organs whose aim is the separation of the different “warps”, so that the “weft” can be inserted. They are constructed with at least two “sets” of threads –”weft” and “warp”– and present simple “patterns”; examples among these semifinished materials are represented by the “canvas”, the “denim” –the fabric of jeans–, and the “pied de poule”.




FABRICS: fabrics with rectilinear threads (“woven warp loom”)





“denim”





“pied de poule”

Fabrics with rectilinear “fabrics work” threads are also known as “Jacquard”, from the name of the inventor of the special weaving machine with which they are produced: they are fabrics in which the weave pattern presents a certain complexity (e. g. the “damask”); in these weaving machines each thread of warp is controlled by a single “mesh” of heddle, sometimes driven by the hole of a punched card who houses the correlated counterweight; these fabrics often are constructed onto a simple canvas, who is the base of the fabric structure.


TESSUTI: fabrics with rectilinear “fabrics work” threads (“Jaquard”)






TESSUTI: fabrics with rectilinear “fabrics work” threads (“Jaquard”)

“damask”

The fabrics with curvilinear threads are the so called “knitted fabrics”: they are constructed with special machines (they are called “knitting machines”), even with a single thread row. Often the production plants are dedicated to a single kind of final product , as it happens for example with socks production. Depending on the process flow direction, it is used to classify knitted fabric into two types: “weft knitting” and “warp knitting” (these terms come from the traditional weaving technology, since in this process “weft” and “warp” are not defined). An example among these products is the “jersey”.


FABRICS: fabrics with curvilinear threads (“knitted fabrics”)





artisanal production of a sock





“jersey”



Fabrics with knotted threads are produced by means of special machines, and can be got even with a single row of thread: to these category belong any kind of “net”, whose applications are numberless, often extended to technical fields.


FABRICS: fabrics with knotted threads




FABRICS: weaving machine weaving

A fabric produced by means of a weaving machine is the weaving product of a fiber who is previously subject to “carding” and “spinning”, if necessary; the former is mainly the orientation of the fiber; the latter is the reduction of it either to “yarn” or “thread”; the goal of those operations is to create a thread intersection who is called “weave”. In the geometric configuration produced by the weaving machine, the threads aligned alongside the weaving flow are called “warp”, while the ones (if necessary just in one “set”) aligned orthogonally are called “weft”. The semi finished fabric can be subjected to “dyeing” (in case either the yarn or the thread would have not been already coloured in mass) or “printing”, and sometimes they can be “laminated” and “coupled” with other flexible semi finished materials, mostly polymeric. In the classification of weaving machined fabrics it is important to indicate the “type of weave”.




FABRICS: “weave” scheme of a fabric made by means of weaving machine (rectilinear thread fabrics); the “weave” is always got by the intersection of “warp” and “weft”




FABRICS: “weave” scheme of a “knitted” fabric (curvilinear thread fabrics); the thread (if necessary just in one “set”) is connected by means of “meshes”




FABRICS: weaving machine for artisanal weaving




FABRICS: weaving machine scheme for artisanal weaving with “canvas weave” (note that the industrial machine is based on the same kinematic principles)




FABRICS: weaving machines for industrial production




FABRICS: the concept of the fabric weave itself can determine the creative effect (Missoni)




FABRICS: type of weaves of weaving machined fabrics (rectilinear threads fabrics)

“Rectilinear threads” fabrics can be produced creating different kinds of “weaves”. The fundamental weaves are three: “canvas weave”, “twill weave” (also known as “diagonal”), “satin weave”; from these weaves others like “gauze”, “panama”, “hedgehog” etc. are derived. As already said, when it is necessary to design complex patterns, special weaves, so called “Jacquard” are prepared.




FABRICS: CANVAS weave of a fabric

It is the simplest weave: weft and warp alternate each other; threads can assume both different colour and shape, even grouped, creating very simple textures, like “checkered”




FABRICS: TWILL weave (also known as DIAGONAL) of a fabric

It is very common: weft thread passes over two, maximum four, warp threads, creating the characteristic “diagonal texture”; “denim” (jeans) and “pied de poule” are made with this weave




TESSUTI: HEDGEHOG weave of a fabric

This important weave can be based both on the canvas weave and twill one: it is added a weft thread that, extracted in shape of rings, can be used this way (woven “sponge” effect) or, in case these “rings” were opened, either a “fur effect” is reached (“peluche”) or “velvet” is got.




TESSUTI: JAQUARD weave of a fabric

Complex textures –better to say “art work”– need to be prepared with dedicated weaving machines, in which even each single thread can be controlled along the weaving process




FABRICS: special fabrics

Glass fiber fabric for composite materials







Fire proof gloves with wrist and back made in aramidic fiber (Kevlar) fabric, aluminium coated, with palm in PBI polymer fiber fabric





Carbon fiber fabric “impregnated” by resin in composite material products





Three-dimensional fabric with structural properties for assembly purpose


“NON-WOVEN” FABRICS: definition and characteristics

A “non-woven” fabric, that is a “non-fabric”, is a semi finished flexible laminar material similar to a fabric but got by means of different intersection techniques in which thread is almost always discontinuous and randomly worked. The peculiar characteristic of these materials is that the “third dimension”, that is the thickness, is not depending on the thickness of the thread, so that it can be remarkable; this is possible because the cohesion of the fibers does not depend on the intersection itself (like in the fabrics weaves) but is correlated to other principles (simple adhesion, thermal processes, adhesive substances etc.). Felt, wadding, fiberglass mat, many glass fiber semi finished materials for composites are example of this typology. Often they are used in combination with fabrics and polymeric films.




“NON-WOVEN” FABRICS: felt

This ancient material is produced by means of the so called “felting” process, where the main cause of the fibers cohesion is the friction induced by the animal fur hair scales (“adhesion”)

TECNOLOGIA DELLA PRODUZIONE

Arch. Sergio Antonio Salvi




“NON-WOVEN” FABRICS : cotton wadding

It is a widely used non-woven material, especially applied in the health sector (above all cotton wool) and for paddings




“NON-WOVEN” FABRICS : non-woven polypropylen fiber

These semi finished materials characteristics are related to their polymers

TECNOLOGIA DELLA PRODUZIONE

Arch. Sergio Antonio Salvi




“NON-WOVEN” FABRICS : glass fiber strand mat”

These semi finished materials are fundamental for composite materials production




“NON-WOVEN” FABRICS : glass fiber strand mat”

“Dar” armchair with seat and backrest made of glass fiber reinforced polyester (des. Eams, prod. Herman Miller Collection, USA 1948)




POLYMERIC FILMS AND “MULTILAYER” FILMS: production sector and characteristics

Polymeric films, above all “multi-layers”, are among the most important products of the plastic materials industry. Thermoplastic materials can be easily reduced into films and, thanks to their phisical peculiarity, present the possibility to be coupled in layers to every laminar flexible material (fabric, non-woven, metal thin sheet, wood veneer etc.). In multilayers the fundamental technological concept is that the functionality of the semi finished material is the sum of the single layer function (s). Polymeric based multi-layers are applied in almost all industrial sectors, such as: building and civil works; boating; furnishing; technical suits; footwear; toys; food and drinks packaging; packaging in general etc.






POLYMERIC FILMS AND “MULTILAYER” FILMS: thermoplastics calendering

This technology one of the most important process to get thick multilayers

Scheme of the process




POLYMERIC FILMS AND “MULTILAYER” FILMS: film extrusion

Film extrusion is one of the most important process to get thin multilayer films

Plant scheme and detail of extrusion die




POLYMERIC FILMS AND “MULTILAYER” FILMS: products examples

“Dune” (Mandarina Duck) and “Relife” (Superga)





“Inflatable” raft and technical membrane





Matress “Transformer”, who can be “shaped” by means of a hand operated vacuum pump, and seat “Torso”, inflatable by means of a vacuum cleaner whose flow must be inverted (respectively: des. Arad, prod. One Off, 1983; des. Deganello, prod. Cassina, 1982)





Multilayers made of aramidic fibers (Kevlar) and polymeric films aimed to get flexible composite materials





Thermochromic multilayer





Electroluminescent multilayers

“Foglia” (leaf) designed by Branzi

OMITTED

sergio antonio salvi, laminar flexible materials (lecture extract)

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