Structure SMC / Prepreg Blends: A joint development between Ford Motor Company and the Magna Outer Company to develop an innovative prototype composite frame that is manufactured by compression molding carbon fiber SMC And carbon fiber prepreg, the part is reduced by 34% of the weight, the number of parts reduced from 45 to 6. Among them, the two composite sub-parts and their four metal inserts by adhesive bonding and structure The riveting methods are assembled together and the prototype is said to have undergone Ford's car-level testing
Two typical methods of preparing SMCs are typically one of the more common solvent-based formulations at lower temperatures and the higher temperature hot-melt formulations that require specialized equipment similar to that used by prepreg manufacturers The preparation method.
In response to the latest EU and North American requirements for reducing VOC emissions (specifically for styrene emissions), the current SMC formulation is changing.
Unfortunately, however, as a cost-effective, highly effective diluent, formulators often use styrene in solvent-based formulations to reduce resin viscosity and achieve better wetting of fibers and fillers to improve handling and drive Density, extend the shelf life, reduce auto-polymerization problems, improve UV stability.
As a result, styrene is not easily replaced, leaving resin suppliers and distributors with a difficult choice: either to find styrene-free diluents to ensure that they can continue to use solvent-based formulations or to switch to hot Melting preparation method, which requires a lot of expenses.
No matter what kind of choice, all have their own advantages and disadvantages.
Polynt-Reichhold, the United States company, is at the forefront of SMC and true prepregs in the pursuit of low-VOC or VOC-free resin systems.
Five years ago, 90% of the company's resins for SMC and prepreg were styrene-containing.
Looking for an alternative to producing styrene-free polymers, the company chose a difficult road - creating a cheaper system that does not contain active diluents.
Its strategic focus is on the structural aspects of providing a fast-curing, room-temperature-preservable composite solution that delivers zero-VOC emissions using either glass or carbon fiber with emphasis on molding for SMC and prepreg applications effectiveness.
Fortunately, the new hybrid system uses exactly the same initiator and curing mechanism as conventional styrene-containing SMCs, so the company is able to match the cycle times of traditional SMCs without losing productivity.
The end result is a VOC-free system that eliminates the need for refrigeration, has a longer shelf life, increases yields, is suitable for electrophoretic coating, and costs less.
Commercial applications of the VOC-free vinyl ester resin SMC developed by Polynt-Reichhold include:
➤ Battery box;
➤ Battery case molded from Continental Structural Plastics for use with General Motors 2014 Chevrolet Spark electric vehicles;
➤ Manufactured by Molded Fiber Glass for GM's 2016 Chevrolet Corvette chassis.
Continental Structural Plastics said Dr. Mike Siwajek, vice president of research and development, said that while many systems now meet current requirements, Continental Structural Plastics and others are still studying alternative chemical materials, including thermoplastics. Such changes, including the trend Hot melt system.
'At present, for compounding, molders and OEMs, there is a need to reduce the amount of styrene at the expense of increased costs in hot melt and solvent-based formulations. "Terrence O, Vice President of Marketing, Core Molding Technologies, USA Donovan argues that because of the high costs associated with the currently known methods, molders and OEMs are required to commit themselves to the end result: reducing the residual styrene (and VOCs) in the short run by adding some cost. He predicted: 'If this can be done, commercialization will accelerate.'
"When you remove styrene and use a hot melt system, handling and processing can become challenging." Robert Seats, Ashland North American Technical Director, said, "Because hot melt systems require more than conventional resin pastes At significantly higher temperatures, on the other hand, with hot melt systems, significantly more material can be processed per hour for higher yields.
'When talking about styrene emissions, it's important to remember that we are using a closed mold process for the SMC.' 'Mark Harber, business manager at AOC in the US, said:' This means eliminating styrene emissions for workers A good working environment is relatively easy.
AOC's approach is to use styrene-free diluents, such as vinyltoluene and acrylates.
Referring to the automotive industry, compounding and molder Terrence O 'Donovan of Core Molding Technologies of the United States states: "For medium-volume projects, research has shown that SMC composites are a more economical option than steel and aluminum. Advances in resin and fiber technology have led to lower densities while maintaining or enhancing strength, making SMC composites a logical choice for new applications. "