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3 posts from March 2009

March 29, 2009

PVC Processing Problems---Plateout

                                     Conical twin screws                                           


One perplexing problem that occasionally arises during long extrusion and calendering runs, especially with opaque, pigmented or filled compounds, is plateout - a term used to describe the buildup or deposit of incompatible material on the screw, in the die, on embossing rolls,roll take-up equipment or sizing sleeves.  In time this deposit affects the surface finish of the product, and also provides sites for sticking - leading to degradation.  Production down-time for clean-up is then necessary. All the factors responsible for causing plate-out are not fully understood.  It is believed that minor incompatibilities of additives are partly responsible but not the whole cause.  Changes in type and use levels of lubricants, fillers, pigments and stabilizers, as well as changes in processing conditions (speed, temperature) can affect the severity of plateout - for better or worse. Even the weather (high humidity) has been known to aggravate plateout!  Although plateout may occur in a clear formulation, most plateout incidents seem to happen with opaque, pigmented or filled compounds. Invariably, a combination of two classes of metals are usually present in plateout - prone compounds - alkaline earths (calcium, magnesium from the filler or barium from the stabilizer) and heavy metals (most commonly titanium from  titanium dioxide pigment, also lead and cadmium from stabilizers or pigments).                                


Several empirical approaches to the control of plateout have evolved over the years, which have shown varying degrees of effectiveness:

           1.  Stabilizers based on organotin derivatives have not been shown to contribute to plateout, mainly due to their very high compatibility or solubility in the PVC melt.  On the other hand, salts of barium, cadmium, calcium, zinc and lead are either insoluble or less compatible with the PVC melt and can aggravate plateout if other conditions are right.

           2.  Compounds based on emulsion polymerized PVC resins (E-PVC) normally cannot be induced to show plateout.  In some cases, replacing a small amount (10-20%) of suspension (S-PVC) resin with E-PVC will reduce plate-out.  This may be due to the presence of trace amounts of emulsifier present on the resin, for the addition of either cationic or anionic surfactants in very small amounts (0.1 phr) has also been shown to reduce plateout.

           3.  A mechanical approach to plateout control which has worked successfully involves the use of a small amount (0.5 phr) of a silicate filler to contribute mild abrasive or scrubbing action on metal surfaces.

           4.  A small container of mineral spirits mounted above the sizing sleeve of a vacuum cooling tank so as to permit a slow, dropwise addition of mineral spirits on the hot vinyl profile just before entering the vacuum sizer will often  keep sizing sleeves clean.


Lab Test for Plateout---



Skip's PVC Charts 026 

The test compound, containing DuPont's Wachtung Red pigment(notorious for showing plaeout) is processed on a two roll mill, and the sheet discarded, leaving any plateout deposit on the rolls. A high TiO2 containing white "scrubbing" compound with abrasive silicate filler is then processed on the same two roll mill, removed, and the degree of "pink" indicates the degree of plateout in the test compound. The picture shows how PVC resins and stabilizers can affect plateout.

March 24, 2009

"The Invisible Killer"

For those who express concern about Carbon Dioxide and their carbon footprints, here is an even more dire issue that should make even Al Gore quiver in his boots!!

Ban Dihydrogen Monoxide!


Dihydrogen monoxide is colorless, odorless, tasteless, and kills uncounted thousands of people every year. Most of these deaths are caused by accidental inhalation of DHMO, but the dangers of dihydrogen monoxide do not end there. Prolonged exposure to its solid form causes severe tissue damage. Symptoms of DHMO ingestion can include excessive sweating and urination, and possibly a bloated feeling, nausea, vomiting, and body electrolyte imbalance. For those who have become dependant, DHMO withdrawal means certain death.


* is also known as hydroxyl acid, and is the major component of acid rain.

* contributes to the “greenhouse effect”

* may cause severe burns

* contributes to the erosion of our natural landscape

* accelerates corrosion and rusting of many metals

* may cause electrical failures and decreased effectiveness of automobile


* has been found in excised tumors of terminal cancer patients


Quantities of DHMO have been found in almost every stream, lake, and reservoir in America today. But the pollution is global,and the contaminant has even been found in the Antarctic ice. Dihydrogen monoxide has caused millions of dollars of property damage in the midwest, California, and recently in Latin America.

Despite the danger, Dihydrogen Monoxide is often used :

* as an industrial solvent and coolant * in nuclear power plants

* in the production of styrofoam * as a fire retardant

* in many forms of cruel animal research

* in the distribution of pesticides. Even after washing, produce remains

contaminated by this chemical.

* as an additive in certain “junk foods” and other food products.

Companies dump waste DHMO into rivers and the ocean, and nothing can be done to stop them because this practice is still legal. The impact on wildlife is extreme, and we cannot afford to ignore it any longer!


The American government has refused to ban the production, distribution, or use of this damaging chemical due to its “importance to the economic health of this nation”.

In fact, the U.S. Navy and other military organizations are conducting experiments with DHMO, and designing multi-billion dollar devices to control and utilize this material during warfare situations. Hundreds of military research facilities receive tons of DHMO through a highly sophisticated underground distribution network. Many of these facilities store very large quantities for later use!

IT’S NOT TOO LATE! (See video at http://www.youtube.com/watch?v=yi3erdgVVTw

Act now to prevent further contamination. Find out more about this dangerous chemical. What you don’t know can hurt you and others throughout the world!

Gunfighter toon

March 23, 2009

A Few Old Companies from the PVC Industry

Here's a partial list of companies that made PVC resins, and stabilizers-- that either no longer exist or were swallowed up by bigger fish! Anyone remember the "good old days"?---(or care?):

PVC Resins: (Monomer at $0.05/lb, PVC at $0.10/lb)
Diamond Shamrock
General Tire
Keysor Century

Stabilizers: (Ba/Cd/Zn liquids at $0.30/lb, Tins at $1.00/lb.)
Advance Solvents & Chemicals
M&T Chemicals
Synthetic Products
Harshaw, and R.T.Vanderbilt

PVC Molecule


Partnerships :: click for details

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