Cellulose acetate, solvent cementing

Most thermoplastic foams can be solvent cemented. However, some solvent cements will collapse thermoplastic foams. The best way to determine if such a problem exists is to try it. In cases where the foam collapses due to softening of the foam cell walls it is desirable to use water-based adhesives based on SBR or polyvinyl acetate, or 100%-solids adhesives. In general, the relatively amorphous thermoplastics, such as the cellulosics, polycarbonate, and polystyrene are easier to solvent cement than the crystalline materials, but there are exceptions. 

Cellular Cellulose Acetate A number of solvents can be used by themselves in cementing cellulose acetate. The following formulations involve mixtures of several solvents, including bodying resins (dope-type cements) (5). 

Acetone and mixture of acetone and methyl cellosolve are commonly used as solvent cements for cellulose acetate. Acetone is a strong solvent for the plastic, but evaporates rapidly. The addition of methyl cellosolve retards the evaporation, prevents blushing, and permits more time for handling the... 

Other cellulosics, cellulose acetate butyrate and propionate are cemented in accordance with the technique described for cellulose acetate. In the case of dope cements, the plastic to be dissolved in solvents is cellulose propionate. Similarly for ethyl cellulose plastic, the strongest bonds are made by solvents or by solvents bodied with ethyl cellulose plastic. 

Natural and synthetic rubber and synthetic resins are soluble in organic solvents resulting in cements, resin solutions, or lacquers. In addition, there are many cellulose derivatives, such as nitrocellulose, ethyl cellulose, and cellulose acetate butyrate, used in preparing solvent-based adhesives. Solvent-hased adhesives are also prepared from cyclized rubber, polyamide, and polyisobutylene. Low-molecular-weight polyurethane and epoxy compounds can be used with or without solvent. On the other hand, high-molecular-weight types or prepolymers require solvent to make application possible. 

These plastics (cellulose acetate, cellulose acetate butyrate (CAB), cellulose nitrate, cellulose propionate, and ethyl cellulose) are ordinarily solvent cemented, but for bonding to non-solvent-cementable materials, conventional adhesives must be used. Adhesives commonly used are polyurethanes, epoxies, and cyanoacrylates. Cellulosic plastics may contain plasticizers that are not compatible with the adhesive selected. The extent of plasticizer migration should be determined before an adhesive is selected. Recommendations for conventional adhesives for specific cellulosic types are as follows ... 

These plastics include cellulose acetate, cellulose acetate butyrate (CAB), cellulose nitrate, cellulose propionate, and ethyl cellulose. These materials are most commonly bonded by solvent cementing. Adhesive bonding is used to a minor extent. 

The solvents listed in Table 9.3 may be used alone in cementing cellulose acetate. 

CAB may be cemented with the solvents listed for cellulose acetate above in addition to those listed in Table 9.4. ... 

CAB should not be solvent cemented to cellulose acetate. A nitrocellulose-based adhesive should be used for such joints. ASTM D2560, a specification of CAB pipe, tubing, and fittings, calls for a solution of CAB in one of the three thinners as follows... 

American Society for Testing and Materials (ASTM), ASTM D2560-80, Standard specification for solvent cements for cellulose acetate butyrate (CAB) plastic pipe, tubing, and fittings. Standard withdrawn 1986. 

Hexafluoroacetone trihydrate n. A solvent cement, active at room temperatures, for bonding acetal resin articles to themselves and to other polymers such as nylon, acrylonitrile-butadiene-styrene, styrene-acrylonitrile, polyester, cellulosics, and natural or synthetic rubber. It is also a toxic irritant, so it must be handled with care. 

CAB should not be solvent cemented to cellulose acetate. A nitrocellulose-based adhesive should be used for such joints. ASTM... 

The largest use of cellulose nitrate is as a base for lacquers and cements. Butyl acetate is used as a solvent. Plasticizers such as dibutyl phthalate and tritolyl phosphate are necessary to give films of acceptable flexibility and adhesion. 

Isopropyl ocetote is a wofer-whife pleosont-odored liquid with properties intermediote between ethyl and butyl acetates. It is miscible with most of the common organic solvents such os alcohols, ketones, esters, oils, hydrocarbons, etc., and it is a solvent for nitrocellulose, cellulose ocetate (of low viscosity) and a wide ronge of oils, fats, waxes, gums ond notural and synthetic resins. Like n-propyl ocetote, its solvent power for cellulose esters is increosed when lower aliphatic alcohols are added. It is largely used in the lacquer industry where its slow evaporation rate and blush resistance ore of importance. It is also used in the monufacture of plastics, artificial leather, dopes, films, cements, and in the recovery of acetic ocid from aqueous solutions. 

For a bodied cement, a suggested formulation is to use solvent solutions of the polymer ethyl cellulose in ethyl acetate/ethyl cellulose (80/20). 

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