Composites can help achieve sustainability goals in the automotive and aerospace industries through lightweighting, which helps decrease fuel consumption and increase efficiency. However, current production scrap, reject parts and end-of-life components are disposed of in landfills. In conjunction with ACMA’s Green Composites Council Recycling Committee, University of Alabama at Birmingham (UAB) graduate student Kristin Hardin produced a survey and distributed it to a cross-section of ACMA member companies to facilitate data-development for a more sustainable future for composites.
Survey results revealed that companies would be interested in a recycling program through which they would either reuse their own scrap or outsource it to another company. After Hardin’s research was awarded first runner-up of the 2014 CAMX Poster Session, Composites Manufacturing Interviews talked with her to learn more about her research.
What were some key findings or themes you found in your survey?
The survey reinforced some things that we as an industry already know, such as that polyester/vinyl ester and E-glass are the most commonly used resin and reinforcements. The majority of those surveyed produced more than 500 pounds of scrap per day (primarily from trim-offs), which makes up five to 10 percent of total production volume per company (with some as high as 30 percent). With the composites industry projected to make nearly $35 billion in the year 2017 and with an estimated 30 percent total production volume going to scrap, the loss in potential revenue could be as high as $10.5 billion. More than 90 percent of companies surveyed stated that all of their scrap from manufacturing or post-production is sent to landfills; they recycle none of it. The highlights of the survey more than sum up the need and emphasis for finding avenues for recycling composite scrap.
Your poster detailed specific case studies where processing and testing proved the viability of composite scrap (such as trim offs, reject parts, etc.) to make more useful and competitive composite products. Can you describe one of these case studies?
All of the case studies are presented to show that whatever the source of manufacturing scrap, it can be recycled and good properties are possible. The most unique case study, to me, deals with the machining residue of an E-glass/epoxy (70 wt. percent glass fiber) composite from Gordon Composite. Trim offs, reject parts and end-of-life components are obvious options for recycling, but machining and finishing scrap are not so obvious. This residue alone accounts for several million pounds of scrap waste per year at Gordon Composites and other fabricators. The study involved compounding 30 wt. percent of this residue with 5 wt. percent MAPP and 65 wt. percent PP using a Leistritz twin screw extruder to produce pellets that were then extrusion-compression molded into 6-inch by 6-inch plates. Flexure and tensile specimen were cut from these plates and tested in our facilities at UAB. Neat PP plates and test samples were also produced for comparison purposes. The flexural strength and modulus showed an increase of 20 percent and 30 percent respectively, while the tensile strength and modulus of elasticity showed an increase of 15 percent and 50 percent respectively.