SikaForce®-820 and SikaForce®-825: Next Generation Multi-Purpose Polyurethane-Based Adhesives

Next Generation Multi-Purpose Polyurethane-Based Adhesives

Author: Doreen Janke, Head Research & Development TC Hamburg.Research & Development / Specialities

The latest development in the Sika 2C-PUR adhesive technology is used in critical bonding of polycarbonate panoramic glass roof system. The technology is in use for example on the Peugeot 3008, where it enables significant weight saving over a conventional glass roof system.  The SikaForce® product range includes several 2C PUR adhesives for Industry and Automotive. 

One of the top sellers is SikaForce®-7570 HP which is mainly used in Automotive exterior bonding applications, for example bonding of tailgates, spoilers, covers and other attaching parts. Despite its broad adhesion range on numerous substrates, its hydrophobic properties and thus good ageing properties, Sika wanted to optimize some technical properties like the mixing ratio and the sagging behavior: Therefore, the project goal for SikaForce®-820 was to develop a new, improved version of SikaForce®-7570 HP and to keep the good bonding performance. 

Peugeot 3008 panorama roof.
Image: Peugeot 3008: panorama roof.

SikaForce®-820: Bonding of sensitive substrates

The main application area is the manufacture and bonding of roof elements for cars where Polycarbonate (PC) is an important substrate. Bonding of PC has some special requirements – it is sensitive towards environmental stress cracking if plasticizers, solvents or other migrating substances are present in the adhesive. Consequently, SikaForce®-820 must not contain these substances.

An additional goal was to have a flat modulus curve over temperature and to reduce the necessary pretreatment for a better access to the very conservative automotive market. SikaForce®-820 contains no plasticizers or solvents and does not need any pretreatment for bonding PC and PC/blends. The excellent rheologic (“flow”) properties allow flexible application. The new technology cures very fast – after 20 min approx. at room temperature the adhesive reaches the handling strength. The mechanical properties and lap shear strength are nearly unchanged over aging in different climatic conditions. 

The main customer is CIE Automotive (former Inteva Roof). The new Sika technology has been applied for bonding the Peugeot 2008 panorama roof, which is produced in China. The field test was successfully completed with 45 produced batches without any problems. The adhesive was developed in Hamburg, Germany and it is produced in Zurich, Switzerland. Due to excellent cooperation between both sites, the formulation transfer, upscale and ramp up of production could be done smoothly. 

Benefits

  • Cost reduction on the line thanks to faster handling time 
  • Well-suited to just-in-time production
  • Boosted Sika products cure independently of environmental conditions
  • Pretreatment free adhesion to sensitive materials 
  • Complete range of products is plasticizer free

SikaForce®-825 – New Assembly Line Adhesive for Ford Bronco Hard Top 

SikaForce®-825: The new elastic 2C-PU adhesive is designed for bonding thermoplastics and composite materials in exterior applications. Webasto, market leader for roof systems, chose Sika and its new product to bond the hard top for the new Ford Bronco consisting of four SMC parts (Sheet Molding Compound).

Special requirements for this application are a very fast setting due to a maximum of 5min cycle time and fast curing to enable just in time delivery. The adhesive formulation is free of plasticizer to minimize the risk of environmental stress cracking (ESC) and its low modulus prevents undesirable bond-line read-through.
   
SikaForce®-825 is a 2C-PU adhesive, available also available in cartridges. It combines high strength with high flexibility and offers good non-sag behavior. Static mixing is possible. Fastest setting times can be achieved through acceleration by IR heat. A possible process consists of IR heating up to 50°C after application followed by 4min of constant heating. After cooling down 1MPa of shear modulus (60% of final stiffness) is reached.

Success through global teamwork

A key success factor for the project was the global teamwork and cooperation inside of Sika. The project started in R&D Hamburg as a development project for new tailgate bonding adhesives. Local Technical Service then initiated first trials with the corporate Webasto team as the development was in a presentable state.

Operations Zurich enabled scale-up and final production of the adhesive. First application trials and prototyping took place at Webasto Germany as well as line design and material approval. Final line build-up took place at Webasto US with the support of Sika Technical Service Madison Heights. Sales Europe and US managed global and local buying centers respectively.

All activities are supported and coordinated by Global Product Management.Ska’s total business will be close to CHF 10M over the project lifetime of the Ford Bronco. Additional projects at Webasto US are expected, especially as GM and FCA are planning copy and paste projects with SikaForce®-825 most likely to be the adhesive of choice. 

Benefits

  • Plasticizer and tin free
  • TG below service temperature
  • Application at room temperature
  • Good non-sagging behavior
  • High strength at high flexibility
  • Prevents marking/read through
  • Static mixing is possible
 Picture: Accelerated curing process
Image: Accelerated curing process
Ford Bronco hard top bonded with SikaForce®-825
Image: Ford Bronco hard top bonded with SikaForce®-825
Ford Bronco
Image: Ford Bronco