Q. FROTH-PAK SR? & FROTH-PAK QC?

FROTH-PAK Slow Rise (SR) , foam used to fill cavities at a slower expansion rate and cure time. Unlike its counterpart FROTH-PAK Quick-Cure, which is intended for surface applications, FROTH-PAK SR allows the foam to flow throughout the cavity and fill the entire void prior to the foam curing. Standard quick cure polyurethane foams will cure in seconds, limiting the flow time.

Product Attributes and Advantages

FROTH-PAK SR is designed to be applied into pre-assembled moulds and panels, and is specially formulated with a slower reactivity time that allows it to pack in place between multiple cavity facings. This can increase the structural strength because the foam becomes tightly packed together and increases the in-place density of the foam, thus creating a composite structure.

This method of injecting foam insulation into a pre-assembled panel is less time consuming and much cleaner than spraying foam onto an open surface and attaching other panels.

FROTH-PAK SR also cuts down on wasted foam by reducing both the need for trimming and the mess from overspray

FROTH-PAK SR
*Inject-in-Place *Not intended for overhead or vertical application due to the slower cure time

Recommended for enclosed (multi-faced) cavity fill applications
Tack free and rise time of 60-90 seconds
Flows to fill cavity more efficiently due to a slower expansion rate
Primarily recommended for cavity fill applications, rather than spray-on-surface applications


FROTH-PAK QC
Spray-in-place Intended for overhead or vertical spraying due to the quick-cure time

Recommended for surface (one-faced) applications
Tack free and rise time of 30-45 seconds
Fast expansion rate ideal for vertical applications (non-sag characteristics)
Primarily recommended for spray-on-surface applications, rather than cavity fill applications

FROTH-PAK SR
Inject-In-Place Foam - SR

Intial Inject 0-10 seconds
Slow Cure Allows foam to flow 30-60 seconds
Foam is flowing to fill entire cavity 60-80 seconds
Foam has filled cavity and is tack free After 90 seconds

FROTH-PAK QUICK-CURE
Spray Foam - QC

Initial Spray 0-10 seconds
Quick-Cure does not allow foam to flow 10-20 seconds
Foam expands outwards 20-30 seconds
Foam is expanded and tack free After 30 seconds

Polyurethane foam is one of the most efficient insulating materials available because of its closed cell structure and rigid monolithic make-up. On the graph below "Alternative Insulation Material" shows the comparison (in insulation efficiency) of polyurethane foam to other common building materials, and the advantage of FROTH-PAK.

ALTERNATIVE MATERIAL COMPARISON

REQUIRED THICKNESS OF ALTERNATIVE BUILDING MATERIAL NEEDED TO ACHIEVE THE SAME INSULATION VALUE AS POLYURETHANE FOAM.


Product Usage and Filling

Detailed instructions for using FROTH-PAK Two-Part Polyurethane Foam systems are contained in the Operating Instructions, which are included with the shipment of each system. The Operating Instructions contain important information on the proper set-up, use and storage of the chemical systems and the patented INSTA-GUN dispensing gun. In addition, you can find valuable application and troubleshooting notes, as well as safety and warranty information, which should be read prior to use.

FROTH-PAK SR is designed for unique "pour-in-place" applications where a slower curing foam is desired. This may involve additional product usage requirements, such as mould filling and shot time considerations. These are general recommendations and guidelines to assist in the use of the product, but do not describe the procedures to be used in any specific application. Qualification of these products in any specific application must be approved, verified and controlled by the end-user.

In-Place Density / Yield
Q: WHAT IS THE DIFFERENCE BETWEEN "IN-PLACE" AND "FREE-RISE" DENSITY??

In-place density refers to the apparent cured density of the foam as it exists in the final form, or part, into which it is dispensed. This will generally be higher than the free-rise density of the foam, and will vary depending on the actual amount of foam that is dispensed into a cavity of fixed volume.
In-place density is important because the final strength and physical properties of the foam will be improved and optimized by increasing the in-place density of the foam.
The in-place density may be increased by dispensing a higher amount of foam into the cavity than what is theoretically needed to fill the cavity, based on the free-rise density calculations. This process is referred to as "packing" the foam.
Proper mould venting can reduce mould pressure and help keep densities lower by allowing the gasses and products to exhaust and flash.

Q: HOW DOES IN-PLACE DENSITY AFFECT PRODUCT YIELD??

FROTH-PAK SR is recommended to be dispensed to an in-place density of 2 pounds per cubic foot (32 kg/m3) in order to achieve the optimum physical properties, as shown on the Technical Data Sheet.
It is possible, of course, to fill to slightly higher or lower in-place densities, depending on the specific application requirements, mould strength and orientation, etc. (See more information on mold considerations. Section 2.2.)
Product yield is affected by in-place density, in that a higher apparent density will yield less volume of foam. The Froth-Pak SR Technical Data lists comparison product yields based on recommended 2 lbs/ft3 in-place density.

ESTIMATE FOAM QUANTITIES FOR DESIRED IN-PLACE DENSITY BY CALCULATING:

Desired in-place density X Volume of Cavity = Amount of Chemical* required

Ex: 2.0 lb/ft3 X 2.0 ft3 = 4.0 lbs required

32 kg/m3 X .057 m3 = 1.8 kg required

* See below to estimate what shot time length is needed to provide the required amount of chemical. To determine the size of your cavity, simply multiply the length times the width times the height to get the cubic volume (irregular sized cavities may require other calculation, but this may be used as a starting estimate.)

MOULD PRESSURE

General considerations

Mould Pressure is difficult to predict and guideline, however, there will be mould pressure exerted by any pour-in-place foam in nearly all applications.

Therefore, all moulds need to be clamped or braced in some way. The amount of clamping required is dependent on the application and the desired in-place density (the higher the density the higher the pressure).

In general, the more foam that is put into the mould, the higher the mould pressures, and subsequently, the stronger the fixturing that is required. Remember, all systems will develop mould pressure.

Three major considerations which will affect mould pressure and how efficiently a mould is filled are application shot time, mould size and orientation, and mould venting. These are discussed briefly on this page.

Application Shot Time

The term "shot time" refers to the length of time necessary to dispense the desired amount of foam into the cavity or mold fixture.

The shot time can be roughly estimated by first knowing the volume of the cavity (cavity size), and the desired in-place density of the foam. Once this information is known, consult the relevant chart in this User Manual which shows the average output of the various Froth-Pak SR systems, in order to calculate approximately how many pounds (or kilograms) of chemical is dispensed in a given time period.
The following calculation shows how this information can be used to determine the approximate shot time in seconds.
(Cavity Size X In-Place Density) / Weight dispensed in one minute = Shot time in minutes

The actual shot time will also depend on other factors such as chemical temperature, application temperature, amount of chemical remaining in the system, etc., and can best be determined by trial application.
Mould Size and Orientation

Mould orientation refers to the position of the mould and the direction that the foam will be poured into and rise within the mould.

There are two basic positions used to describe mould orientation; the first is horizontal pour, and the other is vertical pour. Vertical pour describes a panel that is longer in its height, or vertical direction, than its thickness (i.e. think of a door standing on edge where the foam would have to flow to the top to fill completely). A horizontal pour is orientated where the longest dimensions are in the horizontal direction (i.e. the same door laying on a table with the thickness in the vertical direction).
Most mould types, other than panels, will follow similar principles as this simple example. As a general rule, the foam does not have to work as hard when the mould is oriented horizontally, which makes this the preferred mould position in many applications. This is because the foam will only need to rise a shorter distance, and the cell structure will then tend to be stronger, since the foam cells are less elongated in the direction of rise.

Cavity size and mould orientation are among the most important considerations to know when determining the specific requirements for applying foam in a "pour-in place" application. Your best results, of course, are dependent on this and other factors mentioned, and can best be determined by trial application.
⇒ Proper mould venting can reduce mould pressure and help keep densities lower by allowing the gasses and products to exhaust and flash. Always provide sufficient air escape holes to allow the rising foam to push
out any trapped gasses as the mould is filled.


POST SHRINKAGE OR EXPANSION PREVENTION


All materials will exhibit some expansion or contraction according to temperature changes. Polyurethane (PU) foam systems, in particular, are subject to volume changes under extreme conditions due to the cellular structure and closed cell nature of the product, in addition to the normal expansion/ contraction caused by temperature differences.

Dimensional stability tests are performed according to standard ASTM test methods, in order to determine how the foam will behave under normal and extreme anticipated conditions. This data is shown on the FROTH-PAK SR Technical Data Sheet (TDS). In order to insure that the foam will perform as expected, it is important to consider the various factors in the application stage that can affect the product's ultimate strength, namely the in-place density, temperature, mould orientation and on-ratio dispensing.

The in-place density is a property which will greatly affect the strength properties, since the higher the density, the higher the strength of the foam, or the more resistant the foam is to environmental changes. The in-place density may vary, but is tested at a nominal 32 kg / m3 (2 lb / ft3) density for comparison and specification purposes. Higher in-place densities may increase physical properties, but at the same time will reduce the cost-effectiveness of the product, as well as produce higher mould pressures and reduce flowability. While lower in-place densities may increase the likelihood of volume changes under extreme conditions.

Also, as discussed elsewhere in this technical literature, a mould orientation which forces the foam to rise a long distance will tend to elongate and stretch the cells, which can also weaken the ultimate strength of the foam. Proper ratio of chemicals is, of course, critical to achieving optimum performance, and must be assured for success in any application.

Effects of Temperature

Proper temperature plays a critical role in the performance of any two-component polyurethane foam system, including Froth-Pak SR. Both the liquid chemical temperature and the ambient temperature (i.e. mould temperature) will affect system performance.
The chemical temperature must be stabilized to a temperature above 24° C (75° F). Recommended chemical temperature is 24°C - 29°C (75° - 85°F). If the chemicals are not the proper temperature, then they may dispense in an improper ratio, thereby leading to poor quality foam.
NOTE: It may take from several hours to several days, in the case of the larger systems, for the chemical temperature to reach the proper temperature. This is especially true if the product has been recently shipped or stored in colder temperatures.
For best results, it is advantageous to heat the mould substrate temperature to 27° - 37° C (80° - 100° F), as this will improve both the adhesion of the foam and the flowability of the dispensed chemical. A colder substrate will act as a heat sink, taking away the heat that is generated from the exothermic reaction of the chemicals during cure. This may reduce expansion, flowability and performance.

Chemical Ratio

A ratio is the chemical weight of the "A" component divided by the chemical weight of the "B" component. With any two component polyurethane foam system, if the proper chemical ratio is not maintained, then poor quality foam will result, in addition to a loss of yield.
An "A-rich" mixture may produce foam that is crispy or friable, slower reacting and higher in density.
A "B-rich" mixture will result in softer foam, with possible shrinkage of the cured foam.
The quickest way to periodically check that the proper chemical ratio is being maintained is to dispense the product into a box or paper bag to insure that the reactivity time, appearance and density of the foam is consistent. (See the Technical Data Sheet for specified reactivity and density).