Wood–plastic composite

Some things are made of wood and plastic.

We mix ground wood with heated plastic. This makes a new material. It can be used for many things.

It is used for decks and fences. It is also used for park benches. This material does not need paint. It can be made in many colors. It can even be made to look like real wood.

It is a very useful material.

Some materials are made by mixing wood and plastic. We call these wood-plastic composites.

They are made of wood fiber and plastic. The plastic can be many kinds. Polyethylene is a very common type.

To make them, workers mix ground wood with heated plastic. They use a way called extrusion. This pushes the mix through a shape. They can also use injection molding. This makes parts like cell phone covers.

These materials are very useful. They are used for outdoor decks and fences. People also use them for park benches. They do not need paint. They can come in many colors. They also do not rot like real wood.

These composites can be sustainable. They often use recycled plastics. They also use waste from the wood industry. However, they can be hard to recycle again. This is because of the glues used. They also have a higher fire risk than wood. This is because the plastic can melt.

Wood-plastic composites, or WPCs, are special materials made by mixing wood with plastic.

These materials combine wood fiber or wood flour with a thermoplastic. A thermoplastic is a type of plastic that melts when heated. Common types include polyethylene, polypropylene, and polyvinyl chloride. Some WPCs also include other fillers to change how they work. These materials are part of a larger group called natural fiber plastic composites.

Because they use both wood and plastic, they have unique strengths.

Making WPC is a step-by-step process of mixing and shaping. First, workers mix ground wood particles with heated thermoplastic resin. Most companies use a method called extrusion to make the material. In extrusion, the warm mix is pushed through a shape to make long pieces. Some makers use injection molding to create smaller, specific parts.

Some factories even make small pellets of the material first. These pellets are then melted again to reach their final shape. Because of the wood, these materials are processed at lower temperatures than pure plastic.

The history of these materials began in Italy. A company called Covema was founded in Milan by the Terragni brothers, Dino and Marco. In 1960, they invented and patented the process to create WPC. They sold their product under the name Plastic-Wood. Later, a company named Icma San Giorgio patented a way to add wood fiber to thermoplastics. By the early 1990s, WPC was first introduced to the decking market. This helped change how people build outdoor spaces.

Today, WPCs are used for many different things. In North America, they are most common for outdoor deck floors.

You can also find them in fences, park benches, and even window frames. Some WPCs are used to make car door panels or cell phone covers. They can be made in many colors like grays and earth tones. This means they do not need to be painted like real wood. They are also resistant to rot and decay from water.

Using WPC is a bit like using a hybrid tool. It takes the best parts of wood and plastic to solve problems. For example, they can be molded into curved shapes that real wood might struggle with. They are often sustainable because they use recycled plastics and wood waste. However, they do have some downsides to consider. The plastic parts can melt in a fire, which is a higher risk than plain wood. They can also be heavy if they are made as solid sheets.

Wood-plastic composites, often called WPCs, are engineered materials created by combining wood elements with plastics.

These materials consist of wood fiber or wood flour mixed with a thermoplastic. A thermoplastic is a type of plastic that becomes soft and moldable when heated. Common examples include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polylactic acid (PLA). WPCs belong to a larger category known as natural fiber plastic composites (NFPCs). While WPCs specifically use wood, NFPCs can include other materials like bamboo, straw, or coffee husks. To ensure the wood and plastic bond together well, manufacturers often add chemical coupling agents.

The production of WPC involves a precise sequence of heating and mixing. First, ground wood particles are thoroughly mixed with heated thermoplastic resin. Most manufacturers use a process called extrusion to create the material. In extrusion, the warm mixture is forced through a shaped opening to create long, continuous profiles. Some manufacturers prefer injection molding to create smaller, more complex parts. In some facilities, the ingredients are first processed in a pelletizing extruder to create small pellets. These pellets are then re-melted and formed into a final shape. Because of the organic wood content, WPCs are processed at lower temperatures than pure plastics. If the temperature becomes too high, the wood can burn or discolor.

Different types of WPC can be categorized by their structure and composition. Most WPCs are made from a 50/50 mix of wood and plastic, though they can contain up to 70 percent cellulose. Some are produced as solid or hollow profiles through extrusion. Others are made as injection-molded parts, such as automotive door panels or cell phone covers. A specialized version is the WPC sandwich board. These boards use WPC skins paired with a low-density polymer core. This design creates a panel that is much more rigid and lighter than a solid sheet. These sandwich structures are frequently used in the transportation and building industries.

The history of WPC began in Milan, Italy, during the mid-20th century. In 1960, the Terragni brothers, Dino and Marco, founded the company Covema. They invented and patented the first process to create WPC, selling it under the name Plastic-Wood. Later, the company Icma San Giorgio patented a specific process for adding wood fiber to thermoplastics. While the technology was developed decades ago, WPC only entered the decking market in the early 1990s. Since then, it has grown from a new material into a widespread alternative to natural lumber.

Today, WPC is highly significant in the construction and manufacturing sectors. In North America, its most common use is for outdoor deck floors.

It is also used for railings, fences, park benches, and window frames. Because WPCs can be molded into almost any shape, they can even form strong arching curves. These materials are also popular because they do not require paint. They are manufactured in various colors, such as grays and earth tones, to look like natural wood. This makes them a low-maintenance choice for many homeowners.

While WPC offers many benefits, it also has specific physical properties to consider. The material is highly resistant to rot, decay, and marine borer attacks. However, the wood fibers inside can still absorb water. This water absorption is more common in WPCs using a hydrophilic matrix like PLA. If the material gets too wet, its mechanical stiffness and strength may decrease. The mechanical behavior of WPC is actually most similar to neat polymers, which are plastics made without extra solvents. This means WPCs generally have lower strength and stiffness than solid wood. They are also susceptible to fungal attacks and UV degradation from sunlight.

Understanding the environmental and safety profile of WPC is essential for its use. WPCs are often considered sustainable because they utilize recycled plastics and wood industry waste. However, the polymers and adhesives used make them difficult to recycle once they reach the end of their life. They can, however, be recycled back into new WPC material. One safety concern involves fire hazards. Because plastics have a higher chemical heat content than wood, WPC can melt and may pose a higher fire risk than natural timber. This has led some code officials to study the fire performance of these composite materials closely.