Guide ultime du plastique étiré : Révolution de la science des polymères à l'emballage haute performance

PETG container

Have you ever picked up a crystal-clear, durable PET water bottle and wondered: why is this bottle so strong, yet so thin and light? How can it withstand the internal pressure of a carbonated beverage and survive an accidental drop?

The answer isn’t magic, but a sophisticated manufacturing science centered around a technology known as “Stretched Plastic”.

Hello, I’m Slany Cheuang, the Technical Sales Manager at Leka Machine. With years of experience in this industry, I’ve found that many potential partners are not fully clear on the fundamental principles of plastics molding, which often leads to confusion when selecting equipment. The purpose of this guide is to completely demystify stretched plastic.

In simple terms, the essence of “Stretched Plastic” is the physical process of transforming the chaotic, tangled polymer chains within the plastic into a highly oriented, aligned state. This alignment bestows the plastic with unprecedented physical properties. Through this technology, we achieve three core advantages:

1. Enhanced Mechanical Strength: Stretched plastic containers possess amazing top-load strength, drop resistance, and creep resistance.
2. Superior Clarity: The orderly alignment of polymer chains reduces light scattering, giving the product a glass-like transparency.
3. Excellent Barrier Properties: The neatly arranged molecular chains form a denser barrier, effectively preventing the escape of carbon dioxide (CO₂) and the ingress of oxygen (O₂), making it the ideal choice for preserving beverages and food.

The core process that makes all of this possible is Stretch Blow Moulding (SBM).

In this ultimate guide, we will take you on a journey from microscopic polymer science to macroscopic industrial production. Whether you are a manufacturer seeking packaging solutions, an engineer curious about material science, or a manager making equipment purchasing decisions, this guide will provide you with a comprehensive, one-stop resource.

Table of Contents

1. The Science Behind It: The Principles of Stretched Plastic
2. The Core Process Explained: Stretch Blow Moulding (SBM)
3. A Manufacturer’s Perspective: Stretched Plastic vs. Other Processes
4. Core Material Selection
5. Applications: How Stretched Plastic is Transforming Industries
6. B2B Purchasing Guide: How to Choose the Right Stretch Blow Moulding Machine
7. Future Trends and Sustainability
8. Conclusion: Your Reliable Partner in Stretched Plastic Manufacturing
9. Frequently Asked Questions (FAQ)

Part 1: The Science Behind It: The Principles of Stretched Plastic

The Magic of Polymer Orientation

To understand why stretching makes plastic stronger, we must dive into the molecular level. Plastics are composed of thousands of long-chain polymer molecules. In their raw, unprocessed state, these chains are randomly entangled, much like a plate of cooked spaghetti. It’s this disordered state that limits the material’s macroscopic performance. The magic of “polymer orientation” is the process of combing through this messy plate of spaghetti, aligning the strands to unlock their maximum potential.

Amorphous vs. Crystalline Polymers

Let’s continue with the spaghetti analogy.

• Amorphous Polymer: This is like a plate of cooked spaghetti where the molecular chains are randomly entangled with no fixed structure. Materials in this state are typically transparent but have average physical strength. The PET preforms we use for stretch blow moulding are a classic example of an amorphous structure in their initial state.
• Crystalline Polymer: This is more like a box of uncooked spaghetti, where the molecular chains are tightly packed and arranged in an orderly, parallel fashion. This structure gives the material higher rigidity, strength, and opacity (due to light scattering at the boundaries between crystalline and amorphous regions).

The wonder of stretched plastic is that it transforms an amorphous polymer, through mechanical force, into a highly “oriented” state that is not fully crystalline, thereby achieving both transparency and high strength.

The Critical Glass Transition Temperature ($T_g$)

This is the most critical physical parameter in the entire stretching process. Every polymer has a specific temperature point known as the Glass Transition Temperature ($T_g$).

• Below $T_g$: The material is in a hard, brittle “glassy state.” If you try to stretch it, it will shatter like glass.
• Above $T_g$: The material transitions to a soft, elastic “rubbery state.” In this state, the molecular chains can be stretched and realigned without breaking. This is the ideal temperature window for our stretching operation.

For PET, its $T_g$ is approximately 70-80°C (158-176°F). In the SBM process, the preform is precisely heated to a temperature above this (typically 95-115°C or 203-239°F) to ensure it is malleable enough for stretching but not so hot that it loses its shape. Precise temperature control is an absolute prerequisite for successful biaxial stretching and the qualité of the final product.

Uniaxial vs. Biaxial Stretching: Core Differences & Applications

• Uniaxial Stretching: As the name implies, the material is stretched in only one direction, like pulling on a rubber band. The polymer chains align along the direction of the stretch. This process is mainly used for products where strength is required in a single direction, such as strapping tapes, fibers, and certain types of films.
• Biaxial Stretching: This is the core technology for manufacturing high-performance hollow containers. The material is stretched in two perpendicular directions, either simultaneously or sequentially. For a bottle, these two directions are:
  • Axial Direction: The stretch produced by a stretch rod moving down the length of the bottle.
  • Radial Direction: The stretch produced by high-pressure air inflating the bottle outwards, along its circumference.

Through biaxial stretching, the polymer chains form an interlocking, “net-like” structure. This structure gives the container superior strength and toughness in all directions, enabling it to perfectly handle challenges from both internal pressure (like carbonation) and external forces (like dropping and stacking). Nearly every PET bottle you see in daily life is a masterpiece of biaxial stretching technology.

Part 2: The Core Process Explained: Stretch Blow Moulding (SBM)

Now that we understand the science, let’s look at how these principles are put into practice on an industrial scale. Stretch Blow Moulding (SBM) is the stage where theory becomes reality.

What is Stretch Blow Moulding? An Authoritative Definition

Stretch Blow Moulding (SBM) is a manufacturing process for producing hollow plastic parts (primarily bottles and jars). It combines mechanical force (a stretch rod) and pneumatic force (high-pressure air) to biaxially stretch a pre-molded polymer piece (a “preform”) that has been heated above its glass transition temperature ($T_g$), shaping it into the final form defined by a mold.

In short, you first injection mold a small “test tube” (the preform), and then you heat it and blow it up into a bottle. The SBM process is the global gold standard for producing high-quality, high-performance PET bottles.

The Two-Step SBM Process: The Industry Gold Standard

Within the world of SBM, the Two-Step process dominates the market due to its unparalleled efficiency, flexibility, and stability. It’s estimated that over 95% of all PET bottles worldwide are made this way. As the name suggests, it divides the entire operation into two independent steps.

Step One: Injection Moulding the Preform

This is the starting point of the entire value chain. In this stage, dried PET resin pellets are melted and injected under high pressure into a precision, multi-cavity mold. After cooling, they form the “preforms,” which resemble small, thick-walled test tubes with a finished neck.

The qualité of the preform is the cornerstone of the final product’s success. A high-quality preform must have:

• Precise Weight: Directly determines the final bottle weight and cost.
• Uniform Wall Thickness: Ensures even material distribution during blowing, preventing weak spots.
• Perfect Clarity: Free from bubbles, black specks, or any other defects.
• High-Precision Neck Finish: The neck and threads are fully formed during moulage par injection, and their dimensional accuracy is critical for a perfect seal.

Because preform production can be separated from the bottle blowing stage, this process offers tremendous flexibility. Manufacturers can purchase standardized preforms from specialized suppliers or produce them in-house, depending on market demand.

Step Two: Reheat Stretch Blow Moulding (RSBM)

This is where the magic happens, as the preform is transformed into the familiar bottle. This process is carried out on a machine like the fully automatic PET stretch blow moulding machine offered by Leka Machine, and involves several key stages:

1. Preform Feeding & Unscrambling: Preforms are loaded into a hopper, automatically sorted, and fed onto the heating conveyor.
2. Reheating: The preforms rotate as they travel through a heating oven composed of multiple banks of infrared (IR) lamps. This heating process is meticulously controlled to ensure the body of the preform is evenly heated to the ideal stretching temperature (around 100°C / 212°F), while the already-formed neck area is kept cool to maintain its shape. Advanced machines allow for zone-by-zone temperature control to accommodate the demanding material distribution requirements of different bottle shapes.
3. Stretching & Blowing: This is the heart of the process.
   • The heated preform is quickly transferred into a cool blow mold, which then closes.
   • A stretch rod descends into the preform at high speed, stretching it vertically (axial stretch).
   • Almost simultaneously, a low-pressure “pre-blow” of air is introduced, slightly inflating the preform to ensure it doesn’t touch the cold mold walls prematurely.
   • Immediately following, high-pressure “final blow” air (up to 40 bar / 580 psi) is injected, forcing the stretched preform to expand and conform tightly to the inner contours of the mold, completing the horizontal (radial stretch) and forming the bottle’s final shape and details.
4. Refroidissement et Éjection : The high-pressure air is held for a short period to allow the newly formed bottle to cool and solidify against the cold mold walls. The mold then opens, and the finished bottle is ejected. A perfect PET bottle is born.

On a fully automatic machine, this entire cycle repeats at incredible speeds, with outputs ranging from a few thousand to tens of thousands of bottles per hour (BPH).

The One-Step SBM Process: Advantages for Niche Applications

As a complementary process, One-Step SBM, also known as Injection Stretch Blow Moulding (ISBM), holds its own in specific market segments.

As the name implies, the one-step process completes both preform injection and stretch blow moulding on a single machine in a continuous sequence. Molten plastic is first injection molded into a preform, which is then transferred—without being fully cooled—to the stretch-blowing station for forming.

Advantages:

• Energy Savings: It uses the residual heat from the injection process, eliminating the need for a reheat oven.
• High-Quality Finish: The preform is untouched throughout the process, preventing scratches that can occur during transport and storage, making it ideal for high-end cosmetic bottles.
• Good for Non-Standard Necks: Offers greater flexibility for custom neck designs.

Disadvantages:

• Longer Cycle Times: The overall cycle time is limited by the slower injection molding step.
• Less Flexibility: The number of injection cavities must match the number of blowing cavities, making production schedule changes difficult.
• Higher Capital Cost: For the same output, one-step machines are often more complex and expensive than their two-step counterparts.

Typical Applications: Low-volume production, non-PET materials (like PC, Tritan), irregularly shaped containers, wide-mouth jars, and cosmetic/pharmaceutical packaging with extremely high demands on surface finish.

Part 3: A Manufacturer’s Perspective: Stretched Plastic vs. Other Processes

One of the most common questions you face as a manufacturer or purchasing manager is: “Which technology should I choose? Stretch Blow Moulding or Extrusion Blow Moulding?” These two technologies are fundamentally different and are suited for entirely different products and markets. As a company that provides both Machines de moulage par soufflage bi-orientation et le Machines de moulage par soufflage de corps creux, Leka Machine can offer an unbiased, expert comparison to help you make the most informed decision.

Stretch Blow Moulding (SBM) vs. Introduction au Moulage par Soufflage 3D (EBM): A Critical Decision Matrix

Let’s summarize the core differences in a clear table.

Diving Deeper into the Comparison:

• Principle & Materials: This is the most fundamental difference. SBM’s “stretching” gives PET its unparalleled properties, making it the undeniable choice for pressure-holding and transparent applications. EBM’s “extrusion” process is more like blowing up a plastic balloon; it demands materials with high melt strength, making flexible HDPE its perfect partner.
• Clarity & Strength: Do you want consumers to see the product inside the bottle? If yes, SBM is your answer. Do you need packaging that can withstand the internal pressure of carbonation? The biaxially oriented structure from SBM provides the necessary strength. Conversely, if your product is milk or detergent, an opaque package can protect the contents from light, making EBM a better fit. HDPE’s toughness also makes it ideal for packaging hazardous chemicals.
• Neck Precision: Think of a bottle of soda. If the cap doesn’t seal perfectly, the CO₂ will leak out. SBM uses injection-molded preforms where the threads are formed with extremely tight tolerances, ensuring a perfect seal every time. The necks of EBM containers are typically cut or pinched off by the mold during the process, and they cannot match the precision of SBM.
• Design Freedom – The Importance of Handles: This is a major advantage for EBM. Do you need an easy-to-grip handle for a 5-liter motor oil container or laundry detergent bottle? The EBM process can easily form a handle as an integral part of the container by manipulating the shape of the parison. SBM starts with a fixed, tube-like preform and cannot achieve this. This is why you will never see a PET cola bottle with an integrated handle. If your goal is to learn how to make plastic jerry cans, EBM is the only correct technology.
• Investment Decision: Generally, the initial investment for a fully automatic SBM line is higher than for an EBM machine of similar output. However, for mass-produced, standardized products like bottled water, SBM’s extremely high production speed and efficient material usage result in a highly competitive unit cost.

The bottom line: Your product dictates the technology.

• If your products are water, beverages, edible oils, sauces, or high-end cosmetics, and you prioritize clarity, strength, and a high-quality seal, then a Stretch Blow Moulding Machine is your ideal choice.
• If your products are milk, detergents, chemicals, or automotive fluids, or if you require irregular shapes, integrated handles, and superior chemical resistance, then an Extrusion Blow Moulding Machine will be the more suitable solution.

Part 4: Core Material Selection

While several thermoplastic materials can theoretically be stretched, two have come to dominate commercial applications.

PET (Polyethylene Terephthalate): The King of Stretched Plastics

If SBM is the stage, then PET is the undisputed star performer. It is so popular because its properties are a perfect match for the SBM process:

• Excellent Stretch Performance: PET has a wide and stable processing window, making it easy to form uniform and strong biaxially oriented structures.
• Unmatched Clarity: Stretched PET has a crystal-like gloss and transparency that maximizes product visibility on the shelf.
• Superior Barrier Properties: Its resistance to CO₂ and O₂ is far superior to other general-purpose plastics, making it ideal for carbonated beverages and products with a sensitive shelf life.
• Lightweight & Strong: A PET bottle weighs only about 10% of a glass bottle of the same volume, significantly reducing transportation costs and carbon footprint.
• Extremely Safe: PET is chemically stable and approved by major food safety agencies worldwide (like the FDA and EFSA) for direct contact with food and beverages.
• 100% Recyclable: PET is one of the most recycled plastics in the world. Recycled PET (rPET) can be used to make new bottles, playing a key role in the circular economy.

From 500ml water bottles to 5L edible oil containers, PET’s applications are ubiquitous.

PP (Polypropylene): The Champion for Hot-Fill Applications

Polypropylene (PP) is another important player in the SBM field, especially in niche markets requiring heat resistance.

Stretched PP (often called OPP, Oriented Polypropylene) has significantly improved clarity and rigidity compared to standard PP, though it typically cannot match the crystal clarity of PET. Its single greatest, irreplaceable advantage is its excellent heat resistance.

• High-Temperature Resistance: PP has a higher melting point and can withstand hot-fill processes up to 120°C (248°F) without deforming. This is crucial for products that require pasteurization or hot filling, such as functional drinks, sports drinks, jams, and certain syrups.

However, processing stretchable PP presents challenges. Its processing window is narrower than PET’s, and its molecular structure is more complex, meaning it requires more precise process control and machinery specifically designed for the task.

Part 5: Applications: How Stretched Plastic is Transforming Industries

Thanks to its superior performance, stretched plastic technology has deeply integrated into every aspect of our daily lives. It is more than just packaging; it is a value-added solution for a wide range of industries.

The Beverage Industry: The Clear Choice for Carbonated Drinks, Water, and Juices

This is the largest application field for SBM technology. For carbonated drinks, the excellent CO₂ barrier of stretched PET means the fizz stays in the bottle longer, guaranteeing product taste and shelf life. For pure water, PET’s clarity and pristine appearance convey health and safety. This is the core technology behind every 5L water bottle manufacturing – la plus adaptée à vos produits spécifiques, n'hésitez pas à me contacter chez Leka Machine. Nous sommes là pour vous aider à trouver la.

Food & Edible Oil Packaging: The Perfect Union of Preservation and Shelf Appeal

Large-volume edible oil bottles are another classic application. The excellent oxygen barrier prevents the oil from oxidizing and going rancid, extending its shelf life. The crystal-clear bottle showcases the oil’s color and purity, directly influencing consumer purchasing decisions.

Cosmetics & Personal Care: Uniting Exquisite Appearance with Functionality

Think of the shampoo or body wash bottle on your shower shelf. SBM technology, especially with PET, can create beautifully designed containers that rival the look and feel of glass while offering the lightweight and shatterproof benefits of plastic. A successful shampoo bottle production line is often powered by high-quality SBM equipment.

Pharmaceuticals & Healthcare: Safe, Clean, and Precise Containers

In the medical field, safety, cleanliness, and precision are paramount. Stretched plastics (mainly PET) are widely used for their chemical inertness and high purity to make items like eye drop bottles, oral liquid containers, and disinfectant bottles. The high-precision necks produced by the SBM process also ensure a perfect fit with functional closures like droppers and spray pumps.

Part 6: B2B Purchasing Guide: How to Choose the Right Stretch Blow Moulding Machine

Once you’ve decided to invest in SBM technology, selecting the right machine is critical to your success. This is more than just buying a piece of equipment; it’s choosing a long-term partner who can grow with you.

As the Technical Sales Manager at Leka Machine, I, Slany Cheuang, frequently discuss these points with clients. Based on my years of experience, here are the key factors to consider.

Key Factors to Consider Before Buying an SBM Machine

1. Product Requirements:
   • Bottle Volume: Are you producing small 300ml bottles or large 5L containers?
   • Bottle Shape: Is it a standard round bottle, or a more complex square or oval shape? Complex shapes require more advanced process control.
   • Output Requirements: What is your target production capacity? 2,000 bottles per hour (BPH) or 10,000 BPH? This will determine whether you need a linear or rotary machine and the number of mold cavities.
2. Material Type: Will you be running primarily PET, or do you have a need for hot-fill PP bottles? As mentioned, PP requires a more specialized machine configuration.
3. Degree of Automation:
   • Fully Automatic Stretch Blow Moulding Machine: The entire process, from preform loading to bottle discharge, is automated. It is ideal for large-scale, high-efficiency production. While the initial investment is higher, it significantly reduces long-term labor costs and ensures consistent quality.
   • Semi-automatic Machine: Requires an operator to manually load preforms into the heater and then transfer the heated preforms to the blowing station. It’s suitable for start-ups, small-scale operations, or businesses with a diverse range of products and limited budgets.
4. Budget and Return on Investment (ROI): Don’t just look at the machine’s price tag. You must consider the total cost of ownership:
   • Consommation d'énergie : Advanced machines use servo drives and optimized heating systems for lower power usage.
   • Mold Costs: Molds are a significant investment, and their quality directly impacts product quality and efficiency.
   • Maintenance Costs: Consider the machine’s durability and the availability and price of spare parts.

Understanding Machine Specifications: The Meaning Behind the Numbers

• Number of Cavities: Directly determines how many bottles are produced per cycle. A key indicator of output.
• Max. Container Volume: Defines the largest bottle size the machine can produce (e.g., 2L or 5L).
• Neck Diameter Range: Shows the range of preform neck sizes the machine is compatible with.

Why Choosing a Reliable Manufacturer is Crucial (The Leka Machine Advantage)

1. Technical Expertise and Experience: Leka Machine has been deeply involved in the blow moulding industry for years. We don’t just sell equipment; we provide complete solutions, from bottle design to process optimization.
2. Machine Quality and Stability: We use world-class components, such as Siemens PLCs and Festo pneumatic parts, to ensure our machines operate stably and efficiently for the long term.
3. After-Sales Service and Technical Support: Purchasing a machine is just the beginning of our partnership. We provide comprehensive support, including installation, training, 24/7 technical assistance, and a reliable supply of spare parts.
4. Transparent Delivery Time: A reliable delivery schedule is crucial for industrial projects. We operate with integrity and state clearly that our standard delivery time is 60-90 days. This transparency helps you plan your project with confidence.

If you are looking for the right SBM solution for your project, I would be delighted to assist you. As the Technical Sales Manager at Leka Machine, I, Slany Cheuang, can provide you with a customized technical proposal and quotation based on your specific needs. Please feel free to visit our website at www.lekamachine.com ou contact us directly.

Part 7: Future Trends and Sustainability

As members of this industry, we are focused not only on current production efficiency but also on future sustainability. Stretched plastic technology is continuously evolving to become more environmentally friendly and efficient.

The Driving Force of the Circular Economy: The Use of rPET

The application of recycled PET (rPET) is a key step for the packaging industry toward a circular economy. Modern SBM machines, like those from Leka Machine, are already well-equipped to handle high percentages (even 100%) of rPET material, helping you add a “green” label to your products.

Lightweighting: Doing More with Less

Lightweighting is a perpetual theme in the packaging industry. It means reducing the amount of plastic used without sacrificing bottle performance. This not only lowers material costs but also reduces transportation energy and final waste.

Bio-plastics and the Stretching Process

Using renewable resources to make plastics is another important trend. Bio-plastics like PLA (Polylactic Acid), derived from corn starch, can also be moulage par soufflage bi-étiré. Bien qu'ils soient encore confrontés à des défis en matière de résistance à la chaleur et de coût, leur avenir dans ce domaine est prometteur.

Conclusion: Your Reliable Partner in Stretched Plastic Manufacturing

De l'alignement microscopique des chaînes polymères aux solutions d'emballage mondiales macroscopiques, nous avons exploré ensemble le monde extraordinaire du plastique étiré.

Nous avons appris que c'est le principe fondamental de l'étiquetage biaxial qui confère à des matériaux comme le PET leur résistance supérieure, leur clarté et leurs propriétés barrières. Et Stretch Blow Moulding (SBM), en particulier le procédé en deux étapes, efficace et flexible, est la technologie clé qui transforme cette science en des milliards de conteneurs de haute qualité.

Êtes-vous prêt à améliorer votre ligne de de conteneurs, plastique ? Choisir le bon équipement et un partenaire fiable est votre première étape vers le succès.

Contactez dès aujourd'hui l'équipe d'experts de Leka Machine pour une consultation gratuite sur nos solutions avancées de moulage par soufflage bi-étiré. Travaillons ensemble pour façonner l'avenir de votre produit !

Frequently Asked Questions (FAQ)

Q : Quelle est la principale différence entre le plastique étiré et le plastique ordinaire ?

R : La différence principale réside dans l'arrangement moléculaire interne. Le plastique étiré subit un processus d'étirement physique qui aligne ses chaînes polymères de manière ordonnée et orientée. Cette structure lui confère une résistance mécanique, une clarté et des propriétés barrières aux gaz bien supérieures à celles du plastique ordinaire, qui possède une structure moléculaire désordonnée.

Q : Tous les plastiques peuvent-ils être étirés ?

R : Non. Seuls des polymères spécifiques comme le PET et certaines qualités de PP ont de bonnes propriétés d'étirage. Ils doivent être chauffés à une température spécifique (au-dessus de leur température de transition vitreuse, T_g) pour être étirés efficacement sans se briser.

Q : Dois-je choisir une machine de moulage par soufflage bi-étiré en une étape ou en deux étapes ?

R : Pour la grande majorité de la production standard de bouteilles (comme l'eau, les boissons et les bouteilles d'huile) à grande échelle, le procédé en deux étapes procédé en deux étapes est la référence absolue de l'industrie et le meilleur choix en raison de son efficacité, de sa flexibilité et de son coût unitaire inférieur. Le procédé en une étape est mieux adapté pour les formes spéciales à faible volume, ou les applications ayant des exigences extrêmes en matière de finition de surface, comme les cosmétiques haut de gamme.

Q : Une machine de machine de moulage-soufflage par extrusion moulage par soufflage (MS) peut-elle produire des bouteilles en PET claires ?

R : Absolument pas. C'est une idée fausse courante. Le processus de Injection-Soufflage Moulage par Soufflage (MS) ne peut pas étirer le matériau biaxialement. Tenter de traiter le PET avec le MS donnerait un produit trouble, cassant et de très mauvaise qualité. Pour produire la célèbre bouteille en PET haute résistance et haute clarté, vous devez utiliser une machine de Stretch Blow Moulage par Soufflage Bi-étiré (MSB).

Q : Quel est le retour sur investissement (ROI) typique pour une machine MSB entièrement automatique ?

R : Le ROI dépend de nombreux facteurs, notamment la production de la machine, les coûts locaux de main-d'œuvre et d'énergie, les coûts des matières premières et le prix de vente de votre produit. Il n'y a pas de réponse unique. Cependant, notre équipe technique chez Leka Machine peut vous fournir une analyse détaillée du ROI basée sur votre projet spécifique pour vous aider à prendre une décision d'investissement éclairée.

Q : Leka Machine propose-t-elle des services de moule sur mesure ?

R : Oui, c'est le cas. En plus d'équipements de soufflage de haute qualité, nous avons une équipe expérimentée de conception et de fabrication de moules. Nous pouvons travailler à partir de votre concept de produit ou d'un échantillon de bouteille pour fournir une conception de bouteille professionnelle, une modélisation 3D, et la fabrication de moules de soufflage de haute précision pour garantir que votre produit se démarque sur le marché.