The Three R’s of Injection Molding

By: Brent Borgerson

July 16, 2009

Plastics have long been associated with environmental unfriendliness and wastefulness of crude oil and petroleum byproducts. The advent of bioplastics (biodegradable and biocompostable plastics) which are derived from renewable sources, such as corn starch or vegetable oil, is helping to improve the image of plastics among those concerned with the environment, carbon footprints, sustainability, and being “green.” Bioplastics are slowly but steadily being improved, and in some cases their abilities to process and end-use properties can mimic or even surpass those of traditional petroleum based materials.

Bioplastics, aside from being derived from renewable resources, have the advantage of not releasing harmful toxins during their production, processing or degradation. Many conventional plastics can release known or suspected carcinogens such as formaldehyde or benzene during production, processing or destruction.

Growing the sources for bioplastics also reduces carbon dioxide in our atmosphere. Since the production of conventional plastics produces so much CO2 the use of bioplastics in place of a conventional plastic has a cumulative effect, with the substitution of just one ton of bio for conventional plastic having the net effect of reducing multiple tons of CO2 in the atmosphere. This not only takes into account the production methods for each type of plastic, but also the photosynthesis process in growing biomass or raw material for bioplastics. Bioplastics show great promise in reducing both our industry’s carbon footprint and impact on rising global warming.

What can plastics processors do until bioplastics are perfected in properties and reduced enough in costs to truly compete on a large scale with conventional thermoplastics? This is where the 3 R’s apply in injection molding. The 3 R’s in molding don’t stand for “reading, riting and ‘rithmetic,” but rather: reduce, reuse, and recycle. At Matrix Tooling / Matrix Plastic Products, we have been molding with bioresins, including bioabsorbables for a number of years, but as responsible members of the environmental community, we also have been practicing the 3 R’s.

Reduce: Scrap (and resin usage) is reduced through cold runner and sprue size reduction where possible without affecting moldability. In many cases we have reduced sprues and runners to the prescribed percentage of regrind allowed in the product specification. Hot runners and hot sprue bushings also have been used wherever possible. We have also thinned out wall stocks on parts where the product integrity wouldn’t suffer.

Reuse: We reuse what regrind we can and have come up with applications to use up to 100% in-house regrind. We utilize returnable/reusable packaging where possible and where allowed by the customer. We also have a closed circuit water system to reduce consumption and also filter, monitor and analyze hydraulic oil to avoid indiscriminate unneeded oil changes.

Recycle: Where we can’t reuse in-house regrind, we try to find it a good home. We sell the regrind where possible or even give it away for free if it can be used but there isn’t a paying market. Packaging is recycled also. We even collect our soda pop cans!

Matrix is serious about being environmentally responsible, using bioresins, and abiding by the 3 R’s. It not only makes environmental sense, but favorably affects the bottom line.