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标题：Ｗhat is Polyurethane Foam? And How is It Made?
内容：
What Is modified MDI?
As a derivative of the Pu
Systems MDI series products, modified MDI is currently commonly
used as a technical extension of pure MDI and polymeric MDI, which
could be widely used in such sectors as slab polyols, elastomers,
coatings and adhesives by providing its special properties of usage
and processing due to differences of product structure design and
synthesis process. There are various kinds of modified MDI, and
several MDI manufacturers giants have also been stepping up the
research and development of modified MDI, which has enriched modified
MDI types. And the products that have been produced and used in a
large scale.
The two major components of polyurethane formulations are a polyol
component and an isocyanate component.
Polyols for
Polyurethanes and polyester polyols have been used as the
polyol component in polyurethane formulations for many decades. They
remain the most commonly used polyols. Vast numbers of polyether
polyols and polyester polyols, optimized to provide different
combinations of behavior during fabrication processes and performance
characteristics of fabricated articles, are available from many
different manufacturers.
More recently, polycarbonate polyols have been gaining increasing
interest and use in polyurethane formulations, either by themselves
or more often in mixtures with selected polyether polyols or
polyester polyols, because of their many attractive attributes.
These attributes include performance benefits resulting from the
high-density polycarbonate backbone. Furthermore, polycarbonate
polyols are based on carbon dioxide (CO2), and sequester CO2 directly
in their backbones, enhancing the sustainability of polyurethanes.
The images shown in this post are reproduced from product literature
by Novomer which is a leading supplier of polycarbonate polyols.
The following reaction scheme shows how CO2 is sequestered in the
backbone of a polycarbonate polyol by reaction with an epoxide during
synthesis. Many different “R” groups can be used, to provide a
broad range of polycarbonate polyol molecular structures.
The functionality of a polycarbonate polyol can also be chosen as
desired, by using any one of many different possible starting
molecules. For example, the choices of the following three starting
molecules produce, from left to right, a diol, a triol, and a tetrol.
Rigid polyisocyanurate panel foams with better blowing efficiency
(and hence smaller density when using the same concentration of the
blowing agent pentane) and smaller cell sizes were obtained, while
keeping the formulation viscosity manageable, by mixing 25% to 70% by
weight of a polycarbonate polyol with a polyester polyol.
Ｗhat is Polyurethane Foam? And How is It Made?
What is Polyurethane Foam?
Consumers and manufacturers alike may want to know the answer to this
question. Are you a polyurethane foam technician, a plant manager, or
the owner of the foaming plant itself? Do you want a stronger
foundational understanding of how polyurethane flexible foaming
actually works?
This article will detail the fundamental elements of polyurethane
foaming, particularly as it applies to continuous flexible foaming.
At its most basic, polyurethane foam does two things in the factory.
From the liquid stage it:
expands and gels
The liquid first expands as air bubbles are introduced, then a
secondary reaction gels, or hardens the material at some point in
that expansion.
Let’s break down PU foaming Additives for Polyurethane by function. One
of the most important additives is the catalyst, which can affect the
basic reactions in several ways. It can speed the expansion, speed
the gelling, cool the reaction (so you have less of a fire hazard on
your hands), etc. There are also curing agents, which include chain-
extenders and cross-linking agents. Chain-extenders, like their name
suggests, extend polymer chains, which increases material
flexibility. Cross-linking agents promote and strengthen cross-
linkages, increasing structural integrity for more rigid foams.
Remember that CO2 gas from the reaction with water acts as a blowing
agent? Well, other blowing agents may also be used or added. The main
inconvenience of water blowing in the high temperature of the
reaction, making PU foaming a fire hazard. Physical blowing agents
(additives that physically encourage the expansion of cells instead
of that initial CO2, which is chemically blown) reduce that fire
hazard.
A similar class of additives is fillers. They come as particles or
fibers. Particulate fillers can reduce flammability and add weight to
foam (good for cushioning Flexible Foams). Fibrous fillers reinforce cell
structure. All fillers function to 1) add physical properties like
tensile or compressive strength to foam, and 2) save on costs by
reducing the amount of liquid chemicals used per batch.
内容：
What Is modified MDI?
As a derivative of the Pu
Systems MDI series products, modified MDI is currently commonly
used as a technical extension of pure MDI and polymeric MDI, which
could be widely used in such sectors as slab polyols, elastomers,
coatings and adhesives by providing its special properties of usage
and processing due to differences of product structure design and
synthesis process. There are various kinds of modified MDI, and
several MDI manufacturers giants have also been stepping up the
research and development of modified MDI, which has enriched modified
MDI types. And the products that have been produced and used in a
large scale.
The two major components of polyurethane formulations are a polyol
component and an isocyanate component.
Polyols for
Polyurethanes and polyester polyols have been used as the
polyol component in polyurethane formulations for many decades. They
remain the most commonly used polyols. Vast numbers of polyether
polyols and polyester polyols, optimized to provide different
combinations of behavior during fabrication processes and performance
characteristics of fabricated articles, are available from many
different manufacturers.
More recently, polycarbonate polyols have been gaining increasing
interest and use in polyurethane formulations, either by themselves
or more often in mixtures with selected polyether polyols or
polyester polyols, because of their many attractive attributes.
These attributes include performance benefits resulting from the
high-density polycarbonate backbone. Furthermore, polycarbonate
polyols are based on carbon dioxide (CO2), and sequester CO2 directly
in their backbones, enhancing the sustainability of polyurethanes.
The images shown in this post are reproduced from product literature
by Novomer which is a leading supplier of polycarbonate polyols.
The following reaction scheme shows how CO2 is sequestered in the
backbone of a polycarbonate polyol by reaction with an epoxide during
synthesis. Many different “R” groups can be used, to provide a
broad range of polycarbonate polyol molecular structures.
The functionality of a polycarbonate polyol can also be chosen as
desired, by using any one of many different possible starting
molecules. For example, the choices of the following three starting
molecules produce, from left to right, a diol, a triol, and a tetrol.
Rigid polyisocyanurate panel foams with better blowing efficiency
(and hence smaller density when using the same concentration of the
blowing agent pentane) and smaller cell sizes were obtained, while
keeping the formulation viscosity manageable, by mixing 25% to 70% by
weight of a polycarbonate polyol with a polyester polyol.
Ｗhat is Polyurethane Foam? And How is It Made?
What is Polyurethane Foam?
Consumers and manufacturers alike may want to know the answer to this
question. Are you a polyurethane foam technician, a plant manager, or
the owner of the foaming plant itself? Do you want a stronger
foundational understanding of how polyurethane flexible foaming
actually works?
This article will detail the fundamental elements of polyurethane
foaming, particularly as it applies to continuous flexible foaming.
At its most basic, polyurethane foam does two things in the factory.
From the liquid stage it:
expands and gels
The liquid first expands as air bubbles are introduced, then a
secondary reaction gels, or hardens the material at some point in
that expansion.
Let’s break down PU foaming Additives for Polyurethane by function. One
of the most important additives is the catalyst, which can affect the
basic reactions in several ways. It can speed the expansion, speed
the gelling, cool the reaction (so you have less of a fire hazard on
your hands), etc. There are also curing agents, which include chain-
extenders and cross-linking agents. Chain-extenders, like their name
suggests, extend polymer chains, which increases material
flexibility. Cross-linking agents promote and strengthen cross-
linkages, increasing structural integrity for more rigid foams.
Remember that CO2 gas from the reaction with water acts as a blowing
agent? Well, other blowing agents may also be used or added. The main
inconvenience of water blowing in the high temperature of the
reaction, making PU foaming a fire hazard. Physical blowing agents
(additives that physically encourage the expansion of cells instead
of that initial CO2, which is chemically blown) reduce that fire
hazard.
A similar class of additives is fillers. They come as particles or
fibers. Particulate fillers can reduce flammability and add weight to
foam (good for cushioning Flexible Foams). Fibrous fillers reinforce cell
structure. All fillers function to 1) add physical properties like
tensile or compressive strength to foam, and 2) save on costs by
reducing the amount of liquid chemicals used per batch.