Acrylate based copolymers glass transition temperature

This type of adhesive is generally useful in the temperature range where the material is either leathery or mbbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mosdy uncompounded state. 

Various substituted styrene-alkyl methacrylate block copolymers and all-acrylic block copolymers have been synthesized in a controlled fashion demonstrating predictable molecular weight and narrow molecular weight distributions. Table I depicts various poly (t-butylstyrene)-b-poly(t-butyl methacrylate) (PTBS-PTBMA) and poly(methyl methacrylate)-b-poly(t-butyl methacrylate) (PMMA-PTBMA) samples. In addition, all-acrylic block copolymers based on poly(2-ethylhexyl methacrylate)-b-poly(t-butyl methacrylate) have been recently synthesized and offer many unique possibilities due to the low glass transition temperature of PEHMA. In most cases, a range of 5-25 wt.% of alkyl methacrylate was incorporated into the block copolymer. This composition not only facilitated solubility during subsequent hydrolysis but also limited the maximum level of derived ionic functionality. 

Supriyatno H., Yamashita M., Nakagawa K., and Sadaoka Y., Optochemical sensor for HCl gas based on tetraphenylporphyrin dispersed in styrene-acrylate copolymers Effects of glass transition temperature of matrix on HCl detection. Sens. Actuators B, 85, 197-204, 2002. 

This paper reports on the synthesis, characterisation, and applications of novel flame retardant dibromostyrene-based latexes. They are copolymers of dibromostyrene with butadiene, alkyl acrylates and methacrylates, vinyl acetate, styrene and unsaturated carboxylic acids, which form a wide variety of flame retardant latexes via an emulsion polymerisation technique. Choice of monomer or monomer blend is based upon the final glass transition temperature of the copolymer desired. Other criteria include desired physical properties and chemical resistance. Dibromostyrene-based butadiene and acryUc latexes are shown to possess the desired physical properties for use in coatings, adhesives and sealants, and the bromine content of the latexes has enabled the material to pass six different flammability requirements for the end uses such as textile backcoating, latex-based paint, contact adhesive, latex sealant, nonwoven binder, and carpet backing. 18 refs. 

The typical approach in synthesizing an acrylic polymer useful as a PSA is to use a variety of comonomers to control the glass transition temperature and the cohesive strength of the material. One can estimate the glass transition temperature of a copolymer based on the Tg values of the homopolymers produced by the individual monomers using the well known Fox equation. This empirical relationship states that... 

These empirical relationships along with the glass transition temperature data estabhshed for homopolymers (Table 9.1) allow polymer chemists to determine the optimal position of the glass transition temperature and then design adequate emulsion polymer compositions to fulfill end-users requirements. n-Butyl acrylate (T = -54°C) and 2-ethylhexyl acrylate (Tg = -85°C), for example, are widely used as the major components of water-based pressure-sensitive adhesives. Vinyl acetate and n-butyl acrylate copolymer latexes with a weight ratio of about 80 20 Tg = 8°C) are a primary choice for inte-... 

Acrylic ester homopolymers or statistical copolymers, whose annual world production is higher than 1 million tons, are used in the fields of paints in emulsion, adhesives, textile fiber processing, and paper industry. These applications are in close relationship with their glass transition temperature, which is relatively low. Poly(methyl acrylate) is much more stable against hydrolytic attack by acids and bases than its isomer poly(vinyl acetate). The poly(butyl acrylate) exhibits an elastomeric character which induces multiple applications. 

Up to now, poly(methyl methacrylate) and methyl methacrylate copolymers e.g. with styrene, butyl acrylate and dodecyl methacrylate) have been the most widely used acrylic polymers for nanocomposite preparation by emulsion and suspension polymerization. Less research has been based on other acrylic polymers, such as polyacrylonitrile, poly(butyl acrylate), " poly(butyl methacrylate), poly(2-ethylhexyl acrylate), poly(2-hydroxyethyl methacrylate), polyacrylamide, poly(lauryl acrylate)," poly(butyl acrylate-co-styrene)," " poly(acrylonitrile-co-styrene), poly(acrylonitrile-co-meth-acrylate)," poly(ethyl acrylate-co-2-ethylhexyl acrylate)" and poly(2-ethylhexyl acrylate-co-acrylic acid)," and sometimes small amounts of hydophilic acrylic monomers, such as hydroxyethyl methacrylate, methacrylic acid and acrylic acid, have been used as comonomers. " Therefore, it may be stated that, so far, the preparation of acrylic-clay nanocomposites has been based mainly on high glass transition temperature polymers, although nanocomposite materials with lower glass transition temperatures with improved or novel properties, which exhibit a balance of previous antagonistic properties, can also be achieved and are very desirable. Regarding nanocomposites of low glass transition temperature polymers, such as poly(butyl acrylate), poly(ethyl acrylate) and poly(2-ethylhexyl acrylate), which have been utilized as the main components of acrylic pressure-sensitive adhesives, little information is available. 

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