Brentwood Plastics blog

Developing Custom Plastic Films

Posted by Joel Longstreth on Mon, Sep 26, 2016 @ 12:11 PM

Product development is a rough, bumpy ride with no certain outcome.


It's always a bracketing process which requires many iterations no matter how methodical the approach.
Sir James Dyson thrives on failure.  His vacuum cleaner has been through 5,126 versions.  Well tested products often result in recalls.  


What replaces a bad idea ?  A better one, of course.  De Havillands' culture was that if something
didn't look right, it probably wasn't right.  The reason airplane windows are rounded is that the Comet broke up in flight because the square windows cracked in the corners.

Thomas Edison famously went through 940 filament candidates before he hit on tungsten.  In retrospect
he was more alchemistic than methodical.   Failures did not discourage him.  Instead, he viewed 
failures as data about what did not work.


Today's short attention span is not conducive to perseverance.  By the third iteration, many prospective customers figure we are guessing and dismiss us as incompetent after we are unsuccessful at solving a problem nobody else has been able to solve.  Group think kicks in when the big boss gets the super compressed zip file executive thumbnail version.  Plastic film is a lot simpler than molding, so we rarely need more than three attempts and there are no molds.  

Unlike automotive, our customer's plant is the proving ground and beta test site.


We can't run tests at our facility before presenting a version. With each failed iteration, our credibility erodes.

Suppliers who initially appear discouraging or negative are often the best to work with in the long haul.  These seasoned veterans already know what will work and what won't.  Contrast this approach with a company whose positive-minded sales rep makes promises the company can't deliver.  Like so many things in life, it's not complicated entering relationships; it's extricating oneself which is difficult.  In injection molding, molds are the ties that bind.  Sadly, the empty promises often lead to ugly lawsuits.

It's intuitive that the more complex the problem, more perseverance and revisions are required.   After nearly sixty years, you might think launches would be old hat for rocket scientists.  Everybody except NASA has not given up.  Elon Musk said the last disaster was Space-X's most complex undertaking.


" Design creep" is a plot twist which always sends the process into overtime.  Design creep is introduced in two ways.  Most often, it's after the first or second iteration despite our efforts to capture all the performance parameters up front ( see contact us tab ).  

                                             "Oh, we forgot to tell you we need the film to ______________ ".
For example, we just found out that a film needs to unroll easily after being stored in a desert warehouse all summer.  After the third iteration.  Had this requirement been disclosed in the beginning, we could have saved a lot of time, money and plastic.  Design creep is also introduced when marketing gets into the act and imposes new features often without thinking through the ramifications.  The scary bit is this is America; one must always be thinking of how one could get sued despite best intentions.

It's important to know if the project is ready for prime time.  In the words of one of my former bosses, " you need to be realistic about whether you are in the development stage or in the commercial phase."  Disasters often occur with wishful thinking when on the cusp of going from development to commercial.  And in the words of another of my former bosses, " there's only one thing worse than not having a product - it's having a product that's not fully baked." 

Much has been written about inventions, the tenuous path to commercialization and accidental discoveries. What we do is relatively simple.  If you want us to solve a problem for you, just tell us what you want.  The long form on the contact us page is not best practice for capturing leads.  In lieu of finding out the performance parameters over the course of literally months, we are trying to capture all the performance parameters up front.


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Topics: custom PE film, custom LDPE film

Poly Film Industry Consolidation

Posted by Joel Longstreth on Wed, Sep 14, 2016 @ 03:19 PM

Like any industry which matures, there is first a dynamic growth curve followed by the inevitable consolidation wave.  The blown PE film business is both consolidating and contracting.


By the 1920's, there was a proliferation of automobile manufacturers in the thousands.  Aerospace didn't have
thousands of airplane manufacturers, but maybe hundreds.  An early map of the Kimberley mine was complex
with stakes by numerous colorful characters.  They are all whittled down to a handful of players.

Back in the 1950's, the commercial viability of blown PE film was uncertain.  Before our founder Joe Longstreth
established Brentwood Plastics in 1961, he sold PE resin by setting up companies from scratch to make LDPE film to take away market share from old fashioned true cellophane.  

Cut to present day.  The number of PE film outfits worldwide is certainly in the thousands.  "Turn-Key" film lines are ubiquitous.  Back in the early days, we bought the components separately and made some of the parts ourselves.  My grandfather designed a surface winder for narrow width tubing from scratch which is still in service.

In the US, the consolidation phase has been going on for decades.  The largest instituional trash can liner manufacturer is actually an amalgamation of formerly regional players.  You can't argue with the success of Sigma group's strategy of expansion by acquisition of financially distressed extruders.  By contrast, the largest manufacturer of private-label trash bags is Poly-America who has grown dramatically mostly by organic growth. 

Berry Plastics' mega merger with AEP is the latest chapter in consolidation of companies with roots going back to the 1970's.  Armin Kaufman, founder of Armin Films sold out to Tyco who unloaded their film maker portfolio to Berry in 2005. Berry merged with another large bankrupt player who had gone bankrupt in 2009 - Pliant.  

Where is Armin Kaufman now ?  In Hillside, NJ where he founded Hillside Plastics with the proceeds from the Tyco sale in direct competition.

To take stock, we compiled a list of US operations which include polyethylene blown film extrusion with apologies to anyone we overlooked ( call us if you want to be included ).  There was no clear trend.  A lot of old names were gone either due to buyouts or going out of business ( this is a capital-intensive business; the tripling of resin cost since the mid 90's has weeded out players with inadequate working capital ).  Many have vertically integrated blown film in their operations.  Some niche players were unchanged, some have developed into giants. Next Generation films is an extreme example.

We have been there / done that selling out thing back in 1984, probably not going back there for a while.  We believe there is enough demand for an old school, handcrafted monolayer operation.

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Topics: pe film

PE Film Make / Buy Decision

Posted by Joel Longstreth on Thu, Aug 04, 2016 @ 03:25 PM

It's cliche but true - when milk is cheap, why buy a cow ?  Peter Drucker said it is better to integrate upstream than downstream.  The case for vertical integration play involves payback analysis and other factors.  Henry Ford made his own power mainly because he was fed up with dirty intermittent power.  I can relate.

The most common fallacy of vertically integrated PE film supply is not treating it as a stand-alone P & L.  


Many companies opt to buy film even though they consume enough film to feed a grass roots film plant.
Procter and Gamble Clopay have had a symbiotic relationship for generations.  When P & G puts up a diaper operation, a Clopay embossed film plant will pop up in close proximity.  It's only one item.  

Custom flexible packaging has more moving parts.  There are good reasons to buy PE film on the outside:
1.  Lead time     Using multiple extruders increases the likelyhood of finding a line which needs work.  The New York tri-state area is the best example in the US.

2.  Painless rejection   Rejecting film which comes from an outside source does not generate the acrimony resulting from an internal rejection.  Gotta keep the prima donna pressmen happy, right ?  Finding another film source is easy.  Finding a reliable pressman is not.  If you don't reject film outright, specious claims are a time-tested means to shaving a few cents off raw matierial costs.  The extruder would rather take a discount than see the film show up on his dock.

3.  Cash flow and turns   Most bag makers do not understand the concept of borrowing to pay invoices timely.   Line of credit ?   What's that ?   It's simpler to buy from multiple sources and string out your accounts payable.  If you do hit your credit limit, buy from a different extruder.  

Buying resin is more complex.  
You have to:
forecast 90 days rolling
wait sometimes five weeks for the railcar to show up
pay bills timely
provide quarterly financial statements to the resin companies

If you're on the wrong side of the market, every penny you're off =  $ 2,000.   Film prices drop shortly after CDI comes out.  Whatever is in the silos gets devalued.  Why bother ?   It's much less risky to order film for each job.

4.  Lowest cost   Overcapacity in blown film is a time-honored tradition.  Don't just keep your supplier honest.  Constant reverse auctions give new definition to keeping a supplier honest.

One of our successful alumni - Dave Frecka, founder of Next Generation Films - is betting big on yet another expansion literally the size of two homesteads.  He's betting that his customers will not make their own film.

Flexible packaging converters see making film as much simpler than their complicated processes which involve inks, plates, solvent recovery, adhesives, people, bag and pouch making.  They visit a blown film plant, see an operator sitting down reading a book or taking a smoke break.  The operator is sitting down because he's exhausted from all hell breaking loose over the last two hours.

In theory making blown film is a simple, continuous process.  If it was really difficult and complex, there would not be over 27,000 known blown film shops on the planet. The truth is making blown film is an art despite what equipment manufacturers proffer as "turn-key" lines.  There is a learning curve. 

Let's look at how seemed to be a good idea at the time that led to a salvage play.

The same schedulers who won't schedule a print job until the plates and film are both present hate to wait for film.  The reason the printer has to wait is that a properly run film backlog prioritizes minimal scrap. When the backlog is set up on a first-in-first-out basis or disrupted by the printing plant manager who succumbs to an ultimatum from the cutomer who has threatened to cancel ( sticking the converter with the cost of the film and plates ), excessive transition scrap is the result.   Scrap factors which are not captured in the in the justification for going vertical are transition scrap, internally rejected film, startup and shutdown scrap.  The boffins pick up on the higher than projected cost of goods sold first.  Until the day of accounting reckoning arrives, it's a myopic free-for-all.  Everybody feels good about percieved free film, controlling their destiny and not getting ripped off by their film supplier.

Of course, there are many successful vertically integrated operations.  If the end product has ample gross margin, allocation of the cost burden is moot.  I'm not making this up - many lucrative operations have an internal transfer cost of a penny over resin.   

A blown film operation is capital intensive with inherent high operating leverage.  It makes or loses money incrementally on either side of break-even.  When volume falls short of the break-even, the "prisoner's dilemma" follows.  Running at a loss is better than shutting the line down.  The penultimate desperate phase is scrambling for cheap work to maintain cash flow.  Over the years, I have been to many industrial funerals known as auctions.    We get notifications of liquidations every 6 weeks or so.  We hear from leasing companies who ask if we are interested in lines they have "carved out" of a converting operation.  When the line was first up and running, there was a party atmosphere - " whooopee !  free film !  on demand ! "

So if you are contemplating making your own film either financed or with a few extra millions of extra cash, our advice is to be sure you have:

1.  sales to feed the fixed cost beast
2.  lots working capital and a line of credit
3.  a strong plant manager
4.  commitment to a 24 / 7 operation

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Topics: LDPE film, PEfilm

Buy American / Hire American ? - as if !

Posted by Joel Longstreth on Wed, Apr 06, 2016 @ 05:44 PM

When George W. Bush asked the premier of China what kept the premier up at night, the response was "finding jobs for 25 million people a year."  Products in the mature life-cycle stage are imported everyday to the US at artificially low prices.  Why does the U S government let this happen ?  Why is there no anti-dumping outrage ?


In retrospect, Smoot-Hawley was a causative factor of the depression.  Today's supply chain is interdependent and complex, so tariffs aren't the solution for complicated products.  

Simpler items are imported in large volume to the US at bargain-basement prices.  We're seeing a common thread.  The cost of the finished product mostly from China, is at the price of raw material here in the US, even in a capital-intensive industry such as plastics. Before getting into specific examples, let's look at why. 

( Personally, my cynical opinion is the U S government likes cheap goods to show lower inflation rates and lower COLA  )

My guess is it's a combination of factors.  The two biggest advantages for manufacturers in certain countries are currency manipulation and raw material subsidies.  American manufacturers have the disadvantages of higher wages and the not so hidden costs of regulations and taxes.  Ocean freight is cheap.  Inland freight is equal.

Taxes are a factor of production.  Much has been written about the additional burden of regulation and how it puts U S manufacturers at a disadvantage.  

" One of the single biggest areas we should see some immediate relief 
is from some of the regulations that have stifled our industry
and curtailed some of the growth. "

- William Carteaux, CEO of the Plastics Industry Association

Here is a summary:

  Factor of Production   Advantage   Comments
  direct labor   China  plentiful labor compliment but hard to train  
  freight    none  ocean freight is cheap
  regulations   China

fewer restrictions on solvent inks or disposal.  No OSHA.  No EPA, etc.

  taxes   China  
  resin cost   China US is low cost producer, but China gets big subsidies
  currency manipulation   China  
  electricity     ???  
   logistics   U S   China 
  X files factor   U S    

We have swerved into a few cases in our microcosm which just might be indicative of what's going on on a macro-scale.  Here are a few anecdotes:

                                                              Drawstring stock ice bags              

                                                                    drawstring ice bagstock ice bags
One of our customers does not understand why the cost of drawstring ice bags made in China is literally 1/4 the cost of US made.  The resale price of the finished bag is practically the cost of U S - manufactured. That's the resin pellets before being extruded into unprinted rollstock.   With UPS charges, the convenience store pays $0.04 each. American-made bags would cost about $ 0.09.  Let's face it - who wants to pay 6 cents more for a bag of ice ?  The convenience store operator would rather give up two pints of blood. 

                                                    Red and Yellow barricade tapes


We make heavy metal free red and yellow rollstock, sell it to customers who print, slit and box, often untouched by human hands.  Our customers cannot compete with Chinese goods which contain 1% lead ( contact us if you want to see the test results )  printed slit and boxed at the same price as rollstock.  The imports are not constrained by HMF heavy metal free resins or water-based inks.  American consumers don't care about continual dermal exposure to lead, so everybody's happy.

shower curtains


We have recieved several inquiries from manufacturers of shower curtains in China.  They see the handwriting on the wall.  Chinese labor and electricity are going to approach the costs here at some point.  They are also looking into complying with WalMart's P R ploy - U S made ( the reality is WalMart will only pay 5 to 7% more for American made because that's the maximum upcharge consumers will pay ).  They are incredulous about costs of production here vis-a-vis China.  They go into sticker shock about the price of resin and don't believe us when we go so far as to tell them what EVA resin costs. Everything - resin, ink, labor, electicity, payroll taxes, OSHA, etc. is more here.  Until the factors of production lines cross, they will continue operations in China.

There's no telling how many millions of pounds of plastic these 3 examples add up to, let alone how many U S jobs ( " American carnage" according to Donald Trump ) are at stake.

So there you have it.  Reality is the consumer is conditioned to paying lower prices.

The good news is there is a whole lot of "re-shoring" going on.  It started long before Donald Trump threatened to slap an import tax on companies who move operations outside the U S.  The low prices from China come at a price.  I have talked to many people who are animated when they say they are "through with China ! "  They have paid for the low prices with their sanity.  If they find one of a few suppliers who are not out to rip off the the importer ( with no concern for repeat customers ), the execution is slap-dash and the parts are sloppy.  It's like the X-files.  Nothing is as it seems.


Injection molders are pulling molds wholesale and telling customers to take or leave the domestic price.  To be fair, logistics from the producer to the port have improved.  Not so long ago, you didn't know where your container was until it got scanned in to the ship.  

When it gets to the point that Fox Conn gets serious about migrating operations to the US, somebody is getting frustrated.  

There's plenty of good news to go around these days especially in automotive, about domestic investment in manufacturing.   Who could have imagined that Mike Lindell would invent a pillow and employ 1,500 people in Chaska, MN ?  Then there's other news about labor-intensive industries mostly garments, moving operations to Africa for lowest cost " cut & sew".  


                                     Africa has been called the last frontier for cheap labor.

Can you blame the management of globocorps ?  It's nothing new and it's basic econ.  Factors of production flow to the most favorable environment.  Management has a fiduciary to maximize shareholder return.  Barry Bluestone wrote about it back in 1982 in the book " The De-Industrialization of America".  It's not enough to be profitable.  The profit center which is the least cost producer is going to stay open and get the CAPEX.  The higher cost plants get shuttered.   The Economist says the multinationals may be over the hill.

Since the 2008 downturn, US manufacturers have automated extensively, but there are limits. Consumers are not williing to pay $ 4,500 for a US -made iphone yet.

Trump's persuading Carrier to stay in Indianapolis is a great story, but could whipsaw into the government dictating labor costs.  The most labor-intensive industries would be most affected.  Only time will tell how unwinding trade agreemens will play out. 

In any case, American businessmen just want a level playing field.  Good luck with that.

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Topics: reshoring, buyamerican

Factors Determining Shelf Life

Posted by Joel Longstreth on Tue, Apr 05, 2016 @ 06:39 PM

Shelf life is subjective.   The definition of "use by" or "sell by" date depends on criteria and varying degrees of emphasis.   These dates are understandably conservative.  


Let's look at both the judging criteria and interdependent factors affecting shelf life.

The judging criteria are:

odor and taste      appearance      texture
Obviously the most common sense must-haves for consumer satisfaction, these criteria do not pick up on other factors which have the potential to sicken or kill the customer.

weight loss
Package must not dissipate moisture to comply with weight and measures.

micro loads  
Micro loads are the most critical criterion whether it's fresh, refrigerated or frozen.   Judging by total micro load is an oversimplification and puts the processor in an impossible position.  Something is going to grow on the surface of the product, either friendly aerobic
( in the presence of oxygen ) or anaerobic ( no oxygen present ).   It's a zero sum game microbiologists call competition.  The battle between these types of bacteria dates back to pre-Cambrian times.  Aerobic = good, friendly.  Anaerobic = bad.  Anaerobic is where emerging pathogens such as shigella, campylobacter jejuni and classic clostridium botulinum thrive.  What's scary is listeria mycocytogenes  grows in both conditions and is undetectable to odor and taste.  A bag of salad which has been stored at 38 degrees for 25 days may look good, feel crunchy and taste fine while fraught with stealth populations of listeria.  You think frozen food is exemptOr refrigerated boiled eggs ?

Think petri dish.  The product is a growth medium for cultures of friendly and dangerous bacteria.  Microbiologists talk about " logs " of micro loads.  This is short for "logarithmic" growth starting with "seed" populations.  Fresh cut fruit has taken longer to catch on due to the higher amount of sugar vis-a-vis vegetables. 

Agricultural and Agri Food Canada ( AAFC ) for short usually picks up on listeria contamination in salad first.  No real surprize there.  The bags have a week to incubate in transport from California with greater chance of temperature abuse.  

headspace analysis
Tracking headspace gases interpolates when the package will go anaerobic.  The biggest mistake in headspace analysis is not getting enough data.  Simply checking one or two packages every few days does not provide a true picture.  The right way is to sacrifice a lot of product, check several packages every day then graph the results after throwing out the highs and lows.

processing factors

Think table with 3 legs which are the raw food, processing conditions and packaging.


raw material  
This refers to either the animal or vegetable and how it was handled not just in transport to the processing facility. In the case of vegetables, it's smart to look at conditions before the seed was put in the ground.  If manure was used to fertilize, Escherischia Coli has a way of finding it's way into the processing plant as seed populations.  Avoiding cross contamination requires close attention to HACCP.

processing conditions  
Before personnel set foot on the production floor, it is best practices to educate them about sanitation.  Seed populations of pathogens often enter the plant on the hands of employees.

Packaging cannot make an inferior product into an acceptable product.  OTR is key.  For meats, fish and cheese, a barrier is essential.  For fresh produce the proper barrier or lack thereof is the lynchpin.  A lot of emphasis is put on OTR.  An overlooked factor is the CO2 transmission rate - about four times the OTR.  So the highest OTR without spoiling prevents the dnagerous anaerobic CO2 buildup.

Distribution chain

Temperature during transit is not a factor with pasteurized canned or bottled product.  Wines can be ruined in just a few hours in a hot car.  For fresh products, when measuring headspace it is important to mimic as closely as possible the anticipated temperatures in the " cold chain".  This can be a touchy subject.  Who wants to be the one who has to tell their customer spoilage is due to breaks in the cold chain at  the customer's distribution hub ?  Besides, every Thermo King is at exactly 38 degrees F throughout the entire truck, right  ?   Sending the customer the impartial results from a Ryan often backfires.

I have seen several attempts to quantify the definition of shelf life by assigning a point value to each category adding up to a total of 100.  It never works.  If an item fails in any one of the criteria, it fails.

did you know ?

In the early 1800's there were an estimated 15,000 stills in Kentucky.  Distilling whiskey was a very rational alternative to selling corn.  The reason: practically indefinite shelf life.

The most toxic substance on this planet is not man made.  It is produced by Clostridium botulinum to defend itself against other predatory micro organisms.   Botox anyone ?

Meals Ready to Eat, or MRE's are expected to have a shelf life measured in years.  Exactly how long is time and temperature dependant.  If an MRE is puffy, you now know why it's gone bad.  It has gone anaerobic.

It is estimated that 40% of food in undeveloped countries spoils en route to market.  In the US, consumers pitch about 40% of their food.  Neither one is good from a methane generation standpoint, but no matter.  It's cool virtue signalling to demonize the plastic straw men. 


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Topics: shelf life

High Density HMWDPE Conundrum

Posted by Joel Longstreth on Wed, Mar 30, 2016 @ 12:44 PM

The acronyms HMWHDPE and  UHMWHDPE are confusing.  This discussion breaks down high molecular weight jargon.


Starting with the MW bit -  MW is short for molecular weight.  MWD, or molecular weight distribution is the full name.  Accoring to Handbook of Polyethylene by Andrew Peacock:

     " The size of a polyethylene molecule is normally described in terms of its molecular weight.  All polyethylene resins consist of a mixture of molecules with a range of molecular weights.. The average molecular weight and the distribution of chain lengths comprising a polyethylene resin profoundly affect is ( sic ) properties.  The molecular weights of molecules found in commercial resins may range from a few hundred up to 10 million... Often it is found that those molecules making up the higher molecular weight fractions also display the lowest levels of branching. "

Without getting deep into the five geeky ways to measure MWD, suffice to say that a high molecular weight resin is concentrated, very crystalline ( little short chain brancing ) and very dense. No surprize that by definition the density is high - high density ( HD ), or over .940 gm / cc.

So HMWHDPE = " High Molecular Weight High Density Polyethylene"

As you might expect, these resins are among the strongest polyethylenes pound for pound.  They are so viscous that the ASTM 1238 test for melt index had to be revised when the original Mitsui 7000F came along in the late 1970's.  Melt index is a measure of viscosity.  The test method consists of a cylindrical specimen in basically a heated can with a weight and a hole at the bottom.  The number of grams which come out of the hole in ten minutes is called the melt index.  This provides a crude predictor of the resin's personality.  Garden variety LDPE resins are about 2 grams or the verbal shorthand " 2 melt".   Mitsui 7000 F, American Hoechst GM9255F2 and Conoco / Dupont 5000 had values of + - 0.05.  So the HMW film resins are now tested with a " high load melt index", or "HLMI" which simply means higher weight to get a more meaningful sample.  Some prefer to make it sound more daunting by saying  "HLMIHMWDPE."  The most cotidien examples are single use grocery bags and star- seal trash bags.


Did you know ?  If there is not adequate haul-off speed, thicker HMWHD films will be weaker.  Why ?
the strength is a function of how well the polymer is "knitted" in the transverse direction ( TD ).  Here's how it works:  HMHD is made with a "stalk" or "wine glass" vis-avis "in the pocket" in LDPE.


 When the elastic energy dissipates, the bubble is created.  The tear strength and is a function of how fast the melt is oriented in the TD.  Simply slowing the line speed will create weaker, "splitty" film.

UHMWHDPE as you might guess is an even higher protein version with molecular weights starting around 2,000,000.  Those are long chains.  That said, most grades are in the .928 to .941 range which fall into the category of medium density polyethylene ( MDPE ). You can't make blown film out of it.  It has to be cast, or made with a slot die.  It is very stiff and slippery to the point of having a weird self-lubricating effect.  This trait makes it a popular choice for conveyor belts. I recently had a partial knee replacement.  Instead of a meniscus, I have a stainless steel end of my tibia moving against an insert of HMWHD in my fibula.  ( i have an image, but it's not for the faint of heart ).  There are lots of uses - the most popular is pressure-sensitive tape commonly referred to as "poor man's teflon." 

For the basics of PE, click here.

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Topics: HDPE, HDPE film resin, HDPE resin, UHMWHDPE, HMWHDPE

What Is Polyethylene?

Posted by Joel Longstreth on Wed, Jan 20, 2016 @ 09:07 AM

What is Polyethylene?

Polyethylene is comprised of long chains of the building block ethylene monomer. Ethylene monomer
C2H4 ( or just "C2" for short ) looks like this in English:


Ethylene monomer occurs naturally in both natural gas and as a component of naptha - the portion of a barrel of oil which cannot be refined into gasoline or oil.  So now you know that correlations between zillions of barrels of oil and plastic grocery bags are just more fake news.

                                      Did you know ?  Climacteric plants produce ethylene to induce ripening.


Polyethylene looks like this in English:


How these chains are put together determine the wide variety of resin properties. The fancy name for this is molecular weight distribution, or MWD for short.  MWD influences the 2 main properties which dictate a resins's personaliity - density and melt index.  The variations determine what applications a specific resin will work for.  

Polyethylene is the largest volume thermoplastic resin.  As such, it has a wide variety of uses.  Worldwide, there are probably hundreds of grades just for film alone.

What is Polyethylene?

Polyethylene is very inert.  The prelude to the iconic scene in episode 2 of season 1 of breaking bad illustrates this point.



The character Jesse called Walter from the store asking about what kind of plastic bin to buy.  Walter told him to look for the " LDPE 4 polyethylene " symbol on the bottom.  Jesse pours hydrofluoric acid packaged in a #2 HDPE #2 on the body in the bathtub.  After the bathtub falls through two floors, Walter explains that hydrofuoric acid is so aggressive that it eats through ceramic and metal ( but not polyethylene ).


Melt index (MI) measures viscosity by weighing the amount of plastic resin which extrudes from a cylinder with a hole in the bottom at 300 degrees for 10 minutes. The test method is ASTM D1238. The number of grams is the melt index, or MI.

A low melt index ( under 1 ) is referred to as a fractional melt  or less than a gram / 10 minutes.  Lower MI resins are used for pipe and profile extrusion.   It's common sense that resins with high viscosity (resistance to flow) are inherently strong. In film applications, fractional melt is suitable for shipping sacks and shrink film. Generally there is a trade off between melt index and clarity. The higher the melt index, the clearer the resin.  So a fractional melt is not a good choice when clarity is important and a high clarity "whole melt" or resin with a melt index of over 1.0 is not appropriate for shipping sacks.

By contrast, high melt index resins are used for injection molding.  For injection molding, it is desirable to have a material which flows easily to fill the mold cavity.

This has been a very cursory basic introduction.  To learn about where polyethylene comes from, visit our
post .  Polyethylene is processed by almost every thermoplastic process.

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Topics: polyethylene, LDPE, HDPE

Packaging Film Blame Game

Posted by Joel Longstreth on Tue, Dec 29, 2015 @ 06:59 PM

A plastic film spec properly crafted by a packaging machine manufacturer ensures that the film can always be blamed  That's what an OEM told me last week.


Over the years, we have tried to partner with packaging machine manufacturers with no success.  Now I know why at the tender young age of 63.  We have even cited success stories in which our film has enabled frustrated plant managers to have consistent performance at speeds which exceed the OEM's claims.


To use a military analogy, the machine manufacturers are like the tank corps.  The tanks take the terriority and the infantry follows.  The machinery makers just figure the customer will figure the film out on their own.  When a machine is placed, the distributors find it first and swarm in.   Another set of problems arises from lack of continuity of supply when the distributor "shops" every order.

The setting of this worn out script which happened last week was the last stage of an installation.  The upstream issues were sorted out.  The last tech who was packing up and leaving said all three laminated film candidates were bad. Last remaining problem: good end seals, inconsistent back seams and occasional pinholes.  " FIrst time it ever happened" didn't do the customer much good.

The panicked customer contacted us.  I explained that if they were getting good end seals, they were hitting the optimum combination of heat / pressure / dwell. (The film is the same throughout, therefore the acid test variable is the sealing jaws.)  The heat and dwell time were both too high, resulting in "overcooking".  Turning the heat down - cooler - solved the problem.  Random pinholes in the end seals were the last problem.  

Turns out the packages were dropped three feet to the conveyor.  The molten film did not have enought time to crystallize.  The impact created the pinholes.  The pinholes disappeared when the conveyor was simply elevated.

We didn't get a sale out of it and consulted for a lot less than minimum wage.   

It's a natural human tendency to blame the party who is farthest away from the scene.  In the packaging business, the Napoleonic logic always blames the film first.  


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Topics: packaging machinery, packaging, packaging film

Why Recycled Plastic Content is not Always Practical

Posted by Joel Longstreth on Mon, Nov 30, 2015 @ 03:18 PM

"Recycled Content" must score well in focus groups.  What else could explain why we are getting more requests for recycled content than ever ? 

 The economics of recycling is an entirely separate discussion.  Here are a few reasons why it is not always practical to recycle plastics.

" ( Post-consumer resins are) very important to some brand owners"   
-  Pedro Morales, KW Plastics



Problem:  With very few exeptions, recycled content compromises the properties of the virgin resin.  This has many ramifications.  Taking the exception first, let's look at polyethylene terephthalate a/k/a PETE #1.  It is not melted down and mixed back in with the virgin resin.  Instead, it is repolymerized.  The polymer is broken down into pure monomer and water and reassembled into pure polymer.  PETE is the only recycled resin approved for medical devices.  Not so fun fact:  the general public chooses to recycle only 1 in 3 PET bottles.

" We need ( post-consumer) polyethylene to be looked at like recycled PET is...  Recycled PET  is sold at a premium ( to virgin PET ).  ( Post-consumer) polyethylene needs that same kind of attention." 
- John  Picciuto, president of Western Plastics Association

For this to happen, post-consumer PE ( #2  & # 4 ) would have to attain the same FDA-approved status that PETE has.  

Really truly recycled plastic is picked up curbside, sorted, reground, repelletized and extruded again.  Internally generated scrap which is recycled internally does not fit the definition, but nobody cares or checks up.


At every step there is a chance for contamination.  Cross contamination with other polymers is one of the top issues for recyclers.  If the recycler is fortunate enough to have a batch of just one polymer, that's not even half the battle.   There are variations on the theme of each resin.  So contamination from the same polymer can compromise the final product.  With each heat history, the performance of the polymer degrades due to dissipation of the anti-oxidant.  Recycling makes the public feel good.  In reality it is downcycling to a less critical application.

Medical and Clean Room Packaging

Would anyone in their right mind want to use a medical device such as a syringe which might contain even trace amounts of toxins ?   We have made film for ostomy bags ( prolonged direct dermal contact ) for over 15 years. It's tough enough just to get prime virgin resin approved.  The resin has been put through four biotoxicity tests. Only somebody who wants to get sued would consider using partially recycled content.  Same goes for surgical drapes which come in brief contact with surgical instruments.

The same hospital that discards a blood presure cuff ( after charging the patient $25 ) for fear of a MRSA lawsuit will recycle / sterilize sharps because it makes economic sense.

disposable blood pressure cuff

Clean room packaging has a very low parts per million threshold for many chemicals.  Introducing the wild card of recycled content would risk recall of an entire shipment and loss of a customer, not to mention getting charged back for having to repackage.



Food and Water Packaging

PETE is also the only recycled resin approved for prolonged and direct food contact by the FDA.  Same logic applies to food.  Would you feel comfortable with your food being packaged in a container which might contain toxic chemicals picked up as the scrap is transported and processed  ?   Plastics already get enough of a bad rap due to misperceptions and misinformation.

BPA free is an effective greenwash marketing tactic.  Food packaging also gets scrutinized for what is known as leachables and extractables to be sure undesirable flavors are not migrating into food.

cuisinart.jpg images.jpgdreamstime_s_29972885.jpg


Deposit Slip and Coin Packaging


All bags in this category must have a tamper-evident immediate bond.  The three things which prevent tape from sticking are moisture, dirt and grease.  As such, they have a zero tolerance for slip, or erucamides which are commonly added to make bags open easily.  Adding in recycled content which may have trace amounts of slip could prevent the tamper evident tape from sticking.  The center image is fifty pounds of loose coins.  It is very difficult to qualify film made from prime first quality resin.  The bags are put through multiple drop tests.  If the seals fail, the film is always blamed, not the bag maker.  You guessed it - recycled resin would make the bags weaker and possibly keep the tape from sticking.  

There are plenty of other applications, but you get the idea.  The common thread - is it prudent to risk so much just to appease a great idea from the marketing department ?  




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Topics: recycling, recycled content, recycled plastics

Prime vs. Off Grade Plastic Resins

Posted by Joel Longstreth on Fri, Oct 16, 2015 @ 04:48 PM

Plastic resins are made by major petrochemical companies.  The choicest cuts are sold by their direct sales force or through their "prime" distributors.  How do they go to market with the near miss or transitional resins  ?


There is no controlling legal authority which oversees the distribution of off grade resins. 

Resin brokers are like negociants in the french wine business.  They are launderers.  Imagecredit:


Their raison d 'etre is to make excess production or not ready for prime time go away.  Just like the wine business, there are reputable resin resellers and unscrupulous brokers.  The same rule of thumb applies to resin as it does with wine.  If you're not proud of it, you don't put your brand on it. 

Misrepresentation of key properties is common practice with what is known as "the brokers".  Did you know ?  There are no prerequisites for being an off grade resin broker.  

A "major" is short for a major petrochemical company which manufactures plastic resin.  A "broker" is an entity which takes title to the resin which the major deems to be not "prime" resin. The majors sell prime through their direct sales force and prime distributors.

Want FDA approval of off grade resin ?  Simple.   The broker just changes a few things on a word doc and voila !
Instant food grade.  

A data sheet lists certain key properties which define the characteristics of a resin. The first - melt index or melt flow - describes viscosity.  This tells the processor the most about how the material will behave and how it will affect the outcome of the part or material.  There are other criteria but going into depth would be too far in the weeds. 

Each of these criteria has a target and acceptable range for what is considered to be "prime".  These are not rigid and fixed.  Rather, they are at the discretion of the product manager at the resin producer.  The parameters change depending on the available supply.  When resin is plentiful, the parameters tighten up.  When resin is "tight", they widen.  It's all a function of what the product managers believe they can get away with.

When a product manager gets a report of fresh lots, she decides which ones are prime and which are considered "off grade" or "near prime".  The prime material gets "certs" and is sold through their direct sales force.  What falls outside the parameters is called "off grade" or euphemistically "near prime", "pencil prime" or "excess prime". Other lots are called "transitional" which means resin made transitioning from one grade to another.  

Off grade, or OG for short, is sold through "brokers ".  By selling to a third party, the origin is obfuscated. Brokers are supposed to be discreet and sell off grade to customers who are not direct customers of the same majors and preferably into a different application than originally intended ( It gets interesting when brokered resin finds it's way to prime customers ).   A business model which relies on somebody's mistakes at first sounds like a scary business model.  When resin is "tight" or when the majors are trying to raise prices, the brokers don't have much to sell.  The truth is there will always be material available which is rejected by processors. ( We reject several prime railcars annually produced by ISO 9000 certified major resin companies. )

The majors each have a designated person who offloads the off grade.  As you might expect, there is high turnover in these positions because a lot of money can be made unethically in a very very short time.  When the broker talks to the contact at the majors, the broker must make the seller's job easier by taking as much material per meeting as possible.  This means the broker has to take the winners and losers both. 

The perspective on customers and brokers is topsy turvy.  Suppliers are valued inversely to customers.   In other words, the mentality is you can always get another customer but establishing a relationship with another major is tough.   Here's an illustration from real life: back in the 1980's I worked for a resin reseller in Los Angeles.  My first large order was for 4 railcars of ostensibly near miss garden variety general purpose polyethylene film grade.  I sold them to 4 different processors.  About 2 weeks later, my phone started ringing at 5 AM Pacific with calls from angry plant managers back east who rejected the cars.  My boss shrugged and said "sell them somewhere else; a broker rejects material maybe twice in his entire career.  We can always get another customer. "  That was just the beginning.  When it got to the point that entire days were spent trying to sell the same material, I left.  

The most ethical and truthful brokers graduate to become what is known as "prime" distributors.  They distribute prime to smaller processors not called on by the major's direct sales force.  

It's easy to spot a newbie resin buyer.  They are too smart by half.  They make the rookie mistake of shoving an invoice from a distributor in the face of the direct sales rep.  " I can buy the exact same thing from your off grade broker for 4 cents a pound less !! " ( invoices are always generic to prevent buyers from shopping )  Maybe so for one car.  After that, their reputation precedes them and they get no more deals.  Experienced buyers know the importance of emptying / returning a car quickly so the direct sales rep does not see the car which came from his own plant. 

Sales reps from major resin companies are kept in the dark about what's really going on. 

In fairness, many brokers misrepresent material while others are ethical and disclose fully the good, bad and ugly about specific lots.  Processors operating on razor thin margins are tempted to save money with resin that's "not exactly" and brokers are tempted to misrepresent to move their inventory ( A penny saved in this business is a lot more than a penny earned.  A ralicar is about 200,000 pounds so every penny = $ 2,000 ).   They hope the processor won't know the difference.  Problem: the processor lives with the material and does know when the raw material is not as advertised.  Here is an example: .   The processor initially believes he has saved, but has net lost money in unforeseen scrap and rejects.  
The ramifications go beyond the relationship between the processor and the resin producer.  The finished properties of the plastic film or plastic part within a lot or lot-to-lot are affected with variability of raw material.
So how can you use this information ?  For starters, this explains in part why poly film is often inconsistent.  If the extruder doesn't start with the same raw materials, what do you think is going to happen ?   When doing the due diligence on a supplier, ask them preferably in person if the resin they use is "prime".  Don't be shy.  Ask to see FDA letters and invoices ( for the resin they use to make your product along with "track and trace" records ) with the price of the resin blocked out. If the letterhead is not from a major or authorized prime distributor, it's circumspect.  There is an exception.  Some brokers distribute "generic prime" which has been tested and sometimes blended to fall within specific ranges.
Many large brokers have what they call " generic prime " which is analogous to private label brands.  This is usually fair quality and does suffice for utility applications.
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Topics: plastic resins, LDPE resins, PE resin, PE, prime plastic resin

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