With the LOCTITE® wood construction adhesive range, customers have a wide choice of application methods in order to meet the different requirements of their operations. Primary applications include finger jointing, face gluing, and I-Beam construction. Henkel’s long history and experience has contributed to the exceptional performance of LOCTITE® wood adhesive products in these application fields.
LOCTITE® Adhesives for Engineered Wood
Engineered wood can be used for a broad range of applications. Binding wood particles, fibers, and strands with wood adhesive products creates a strong and durable glued laminated timber construction material. These materials are used for engineered wood laminate, as well as load bearing wood applications and structural supports such as engineered wood joists and trusses.
Engineered wood products are also used to make glued laminated timber beams. Glued laminated timber, or glulam for short, is extremely efficient to produce compared to steel or concrete and engineered glulam beams offer excellent structural support and fire resistance. LOCTITE® wood adhesive products are used in a variety of different engineered wood applications, including:
- Cross Laminated Timber (CLT)
- Glued Laminated Tiber and Glued Solid Timber (GST)
- Finger Joining Timber (KVH)
- Edge Glued Panels (EGP)
- Laminated Veneered lumber (LVL)
- Plywood (PLW)
- I-Joints (LIT)
- Engineered Wood Products made from Strands, Chips, Particles and Fibers (OSB, LSL, OSL, MDF/HDF, LDF)
- Structural Insulated Panels (SIP)
- Ground Protection Systems (GPS)
Finger joints make it possible to manufacture glulam boards and solid timber products of any desired length from short boards or solid timber pieces. By finger jointing wood together a high-strength longitudinal bond is created between shorts to yield a high-quality semi-finished timber product that can either be used directly in construction or further processed into engineered wood products such as glued laminated timber, etc.
LOCTITE® wood adhesive products are the ideal solution for manufacturing high strength and durable finger joints. Customers have a wide choice of application methods that meet the specific conditions and requirements of their operation, including finger jointing plywood. LOCTITE® adhesives are high performance systems that react rapidly and lend themselves to fully automatic, continuous production under a broad range of manufacturing concepts.
Applications of finger-jointed timber include:
- Boards for the production of CLT, glulam laminated beams, as well as glued solid timber (duo and trio beams)
- SST (finger-jointed solid sawn timber)
- Flanges in I-joists and formwork joists
- Finger-jointed components for wood construction (e.g. posts, studs, rafters, and joists)
For manufacturing finger joints, two fundamentally different application methods can be used:
- Comb application
- Contactless application KEBA (Keilzinken Berührungsloser Auftrag)
KEBA was developed in co-operation with application system manufacturers with the aim of offering the user greater precision, cleanliness, flexibility, and process reliability in production environments.
Today, KEBA is used in a variety of versions (depending on the manufacturing process), some of which include integrated continuous application monitoring. Application monitoring is based either on an opto-electronic system (camera solution) or on the PSS (Purbond-Safety-System). The PSS currently represents the state of the art in adhesive process monitoring.
The new PSS provides the greatest possible process reliability in finger joint production at the lowest possible expenditure.
Face gluing is used to either make a thicker or taller piece of wood depending on how you join the wood together. Gluing wood face to face is an easy way to make custom wood thicknesses or panels for a variety of woodworking applications.
Surface gluing refers to the joining of wood pieces and boards either on the broadside or the edge to manufacture multi-layer laminated timber products.
Edge gluing is used among other applications in the manufacture of single-ply panels that are subsequently processed into cross-laminated timber products.
LOCTITE® adhesives are applied in a suitable application process. After application of the adhesive, the adhesive-coated parts are pressed for a defined period of time in a cold process - no additional energy (heat) is required.
The following products can be manufactured with the face gluing application process:
- Glued laminated timber
- Duo and trio beams
- Special structural elements
- Cross-laminated timber
- Layers for cross-laminated timber
- Box beams
- Edge beams
I-Joists and I-Beams are used as formwork in concrete construction and as rafters or posts in wood construction to provide structural support. Due to the particular process conditions, adhesives in the production of I-joists and engineered wood I-beams must meet stringent requirements. The production of an I-joist and I-beam construction basically involves three gluing steps:
- Bottom and top flange finger joints
- Web-to-web joint
- Flange-to-web joint
In the specific production process, adhesive application at each individual gluing station (finger joints, web-to-web, flange-to-web) is accomplished either via a needle-valve or a comb system. The use of LOCTITE® wood adhesive products makes it possible not only to reduce cycle times but also to achieve very high strengths.
Many years of development and experience have consistently demonstrated the excellent performance of LOCTITE® wood construction adhesives in this field of application.
Cross Laminated Timber: Evaluating Building Material Options
Building materials continue to evolve to meet ever-changing demands from regulators, owners, and consumers. Reducing environmental impact while keeping people safe is the goal. Each material – wood, steel, and concrete – have advantages and unique characteristics. While concrete and steel have historically been viewed as the most robust and durable materials, CLT brings new options to designers, contractors, and owners. Substantial benefits of CLT use include the following:
- Offers high strength, structural simplicity, and a lighter environmental footprint than concrete or steel in construction – CLT is carbon negative and uses wood exclusively from sustainably managed forests
- Enables quicker installation, reduces waste, and improves thermal performance for buildings
- Adapts to the project demands – thickness and length can be adjusted, as well on-site construction duration is a few days versus weeks and months with concrete and steel construction
- Generates very little waste – CLT components are shipped for just-in-time scheduling and arrive on-site as a kit, which results in minimal storage requirements
Given the variety of CLT dimensions, it offers flexible design options. The key is the adhesive and how it bonds with the wood panels to produce prefabricated elements. The adhesive also contributes to the structural performance to deliver compressive strength similar to concrete. As the industry continues to adopt CLT, owners want to understand more about the performance and protection it provides to large structures.
Increasing Adoption of Engineered Wood for Large Structures
With the increased demand for sustainable design, building materials have evolved to reduce the direct and indirect impact on the environment. During the construction lifecycle, buildings use energy, water, and raw materials; generate waste and give-off emissions. Cross-laminated timber is gaining in popularity because it is easy to install and generates almost no waste on site. It offers high strength and structural simplicity necessary for cost-effective buildings, as well as a lighter environmental footprint than concrete or steel.
Constructed of several layers of kiln-dried lumber, CLT is stacked in alternating directions, bonded with structural adhesives and compressed to create a panel. The adhesive used in CLT applications needs to meet stringent product standards and must be certified to ANSI standard. These adhesives are designed to balance the ratio between open time and pressing time and provide maximum flexibility for the manufacturer.
There are three manufacturing methods for CLT – Cold Press with Formaldehyde Adhesive, Radio Frequency (RF) press and Cold Press with Formaldehyde Free Adhesive. Each method can support three- to seven-layer panels. The primary differences between each method involve:
- Manufacturing set up and resources
- Adhesive type
- Energy use
As CLT manufacturers continues to transition to more efficient manufacturing processes, adhesive is critical to adopting more efficient and sustainable processing. Henkel’s LOCTITE® HB X Purbond is a one-component polyurethane adhesive. It is free of solvents and formaldehyde and meets the most rigorous strength and emissions guidelines for CLT. Henkel’s LOCTITE® HB X Purbond is designed to work with Cold Press manufacturing without the need for respirators and the moisture curing process does not require heat and reduces energy use.
LOCTITE® HB X Purbond is designed with variable open times between two and 70 minutes. The CLT manufacturer can select the open time – the interval between adhesive application and jointing – that best fits their operation. The formaldehyde-free formulation meets the latest specifications in mass timber construction for healthy indoor air quality in residential premises.
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