ASK SOUTHERN - Help us Evaluate a New Fence Material - Polypropylene

10.26.09

To:  Our customers, the Building Material Professionals, who make this industry work. And all the rest who enjoy reading 'The Southern Blog':
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You know Southern for our PVC materials. Today we have a rather long Blog, because we need to ask: what do you think about polypropylene as a fence material?  Southern is asking you, the Building Materials Professional, to help Southern evaluate a new application for a different plastic material:  polypropylene.  Take a look at the video below. Would this new fence product have a fit in your business? How do you think it would install?  Would it save you time?  Any issues or concerns this brings to mind?  Let us know at svm@svmllc.com.

From time to time, Southern is asked to evaluate alternate plastic materials. 

This week, we were asked to look at some polypropylene fence test materials. 

Polypropylene (C3H6) is a high volume commodity thermoplastic polymer with a melting point of 320 degrees F (compared to 450 degrees F for PVC) and a softening point of 210 degrees F (compared to 150 degrees F for PVC).  It has a variety of uses, including food packaging, textiles, plastic parts and reusable containers.

While polypropylene is liable to chain degradation from exposure to UV radiation such as that present in sunlight, with the addition of carbon black and other UV-absorbing additives, highly color-fast materials can be produced in colors much darker than PVC allows. see  http://en.wikipedia.org/wiki/Polypropylene; and http://www.lenntech.com/polypropylene.htm

The material is very resistant to fatigue.  Look at the hinge of a Tic-Tac breath mint box. The hinge is an example of where polypropylene materials are seen in every day use, because the materials can take a significant amount of wear and tear.

Southern obtained some low gloss wood grain cedar color polyproplyene privacy fence materials recently.  The manufacturer asked us to evaluate the product.  We were provided with several components that we assembled into a completed privacy fence, similar to how our customers would assemble a PVC fence:

        - 7 lb polypropylene rails, 1-1/2” x 4-3/8” x 95-3/8” long (specs indicated 94”), complete with galvanized metal inserts. The metal inserts were 3 lbs of the 7 lbs.
                the throat of the rail measured 7/8” deep, allowing a channel for the acceptance of the panel

        - 4-7/8” x 4-7/8” x 106” fiberglass reinforced polypropylene posts with 3/8” radius corners (specs indicated 108”).  Each post weighed ~9 lbs.

        - 5/8” x 63” high x 91” wide single sheet extruded polypropylene panel (specs indicate 90”).  Each panel weighed ~22 lbs and has 5 reinforcing galvanized metal channel inserts

        - post caps, made from alternate plastic materials

        - no plastic drop in brackets were provided, requiring a typical routed system

The manufacturer’s literature discusses fadeless dark colors, with tolerance to heat at up to 210 degrees F. The manufacturer claimed the ability to pass Dade County wind load tests up to 110 mph for a 6x6 system.  However, Southern received a 6x8 system to install. No Dade County information for a 6x8 system was available.

Passing the wind load test requires installation techniques that differ significantly from the test Southern ran, including using wood inserts in the blank posts, use of post/rail plastic drop in brackets rather than post routs and mechanical fastening of the rails to the panel. 

According to the manufacturer, the material is ~36% lighter than comparable PVC materials.

Our observations (please let us know yours):

        - the materials arrived with some damage.  Is this material more susceptible to handling than PVC?

        - Posts were very flexible and easy to compress

        - Posts routed more easily than PVC, despite the fiberglass reinforcement imbedded in the post material.  Southern did not have the MSDS sheet on the safety of routing this material, given the shavings produced during the routing process.  We would also like to know more about the wear and tear on the router bits, given the fiberglass reinforcements affect on a router bit.

        - We believe posts would normally be 108” long and not 106” as supplied, in order to allow 36” in the ground (about a foot deeper than typical PVC post installation in NC conditions)

        - Post corner radii at 3/8” were more severe than the 1/8” radius we are accustomed to with PVC. This is a way to reduce material from the post.  Does this have any effect on post performance?

        - Post routs were 69-5/8” apart, from top of top rout to bottom of bottom rout, made to accept the rail.

        - No u-channel included with this system, making gaps more visible between the posts and the panel

        - The panel was a one-piece panel, making installation simpler

        - The wind load tests provided with the documentation were performed on a bracketed system, not the typical installation Southern offers.

        - Likewise, the wind load tests required wood inserts in the posts, an additional step and expense not needed with PVC

        - The rails arrived un-notched and were installed that way. We were unsure how this system would remain intact without notching, given the inherent flexibility of the posts.  Our test system will remain standing for a period of time to see how it performs.

        - Panels were very flexible and had a somewhat waxy feel to them.  Their light weight made a panel very easy for two installers to handle. It is possible one installer could have handled, given the weight.  Could one installer handle the panel in a sustaining wind, given the panel’s wide surface area?

        - Since these panels sat in the 7/8” rail channel without any notching or mechanical fastening, we were concerned the panel would act as a sail in higher winds. Will the panels remain seated in the rail channel? More tests needed.

        - Southern offers stainless steel fasteners and aluminum inserts in our PVC systems in order to minimize rust.  What issues might galvanized inserts raise?

        - The fence Southern installed was not easily rackable and was most appropriate for flat terrains.

        - Pyramid post caps were a custom size to fit the posts and made from an unidentified plastic material.  Slight color and gloss variation from the posts. Listed as a nominal 5”x 5”, these fit a post measuring 4-7/8” x 4-7/8”

        - We are working on how to convert a panel of this material into a functioning gate system

        - The last time we were approached by a company with alternate plastic materials, Eon/CPI Plastics Group Limited, we passed on the project.  Eon subsequently went into receivership, voiding all their warranties, making our decision wise in hindsight.

        - These materials come with a manufacturer’s lifetime warranty to the original homeowner, as long as the homeowner registers within 30 days of purchase. Warranted that the product is free from defects (imperfections that impair the use of the product for its intended purpose) that result in rotting, corroding, flaking, peeling , blistering and abnormal discoloration of surfaces.  Remedy is usually product replacement. Manufacturer also might offer a pro-rata refund.  Color change due to weathering is not covered by the warranty.  Also means non-uniform fading is not covered. No other expenses covered, like the installers replacement time.

        - Manufacturer claims 50% labor savings due to the fact panels are manufacturered as complete units and not assembled onsite. Would you experience this drop in labor savings?

        - Cost: 5%-15% more than PVC, based on Southern’s audited costs. Manufacturer claims a 22% to 63% material cost saving over PVC.  We could not corroborate their math. Also, polyproplyene raw material pricing has been increasing recently, since a higher per centage of polypropyline’s raw materials are carbon-based, as compared to PVC (roughly 98% carbon-based for polypropylene versus roughly 48% for PVC).  Polypropylene is made from oil or hydrogen. The article below mentions that lately polypropylene tends to be made from oil, which has had greater price volatility lately.  PVC in the U.S. is typically made from hydrogen. We are concerned whether Southern could maintain prices on products built from polyproplyene. Here is an extract from the 10.12.09 Plastics News regarding the volatility of polyproplyene pricing:
“PP pricing also went absolutely haywire in 2009, mainly due to tight supplies of propylene mon-omer.
That tightness was the result of less propylene being produced from low-priced natural gas feedstock — instead of those based on crude oil — and of some unexpected production outages as well.
“I think volatility in polypropylene is here to stay for some time,” Dow’s Wright said. “It’s driven by monomer. Lighter feeds are preferred right now, and it doesn’t look like the oil-to-gas ratio is going to change.”
As a result, average North American PP prices are up 70 percent since Jan. 1, after falling 55 percent in the last four months of 2008.
The regional PP market also continues to grapple with excess capacity, in spite of recent shutdowns.
“The market is more in balance now than it was, but not all of the excess capacity has been taken out,” Wright said. “Higher-cost facilities are likely to be taken out and rationalized.”
Newell added: “There’s about 3 billion pounds of excess capacity, but producers have throttled so far back on production that you can’t really say the market’s oversupplied. Producers realize that if they lose their grip on production, they can’t pass on price increases.”
At the CMAI event, PP analyst Esteban Sagel said that regional PP makers “showed discipline by only producing what was going to be consumed, limiting inventory buildup and controlling their feedstock purchases.”
As a result, days of PP inventory at the producer level fell from an average of 39 days to 30 during 2009, he said. Sagel added that North A-merican PP operating rates could remain around 80 percent through 2010, a level that he described as “unhealthy.” Higher PP prices caused by high monomer prices also could diminish PP’s status as an inexpensive resin, he said, and create more competition from polystyrene and PET.
“North America is moving to the top of the PP price chain,” he said. “That’s going to be a difficult issue for the industry to face in the next couple of years.”
 

Southern Vinyl. Setting the Standards.
 
Questions? Comments? e-mail Southern at svm@svmllc.com