Re-Creation of Historical Chrysotile-Containing Joint Compounds

Figures & data

TABLE 1  Joint system cement ingredients

Ingredient	Function	Mass used in reformulation (grams)	% by weight	Supplier
Limestone^a	Filler	3640	73	Science Stuff
Mica^b	Anti-cracking agent	800	16	Zemex Industrial Minerals
Casein	Adhesive	225	4.5	Science Laboratories; Sigma Aldrich
Borax	Alkaline source	7.5	0.15	Van Dyke Supply Co.
Soda ash	Alkaline source	20	0.4	Jacquard
Zinc oxide	Viscosity stablizer	5	0.1	Science Laboratories
Natrosol	Water retention	15	0.3	Aqualon (Hercules)
Alkanol XC (Petro AD)	Wetting agent	5	0.1	Sigma Aldrich/ DuPont
Vancide 51Z^c	Fungicide	—	—	—
Dimethyldithiocarbamate, zinc salt	Substitute for Vancide 51Z	1.875	0.038	Sigma Aldrich
Nalco 71-D5^c	Anti-foaming agent	—	—	—
Chrysotile 7RF9^c	Bulk	—	—	—
Chrysotile 7RF3	Substitute for 7RF9	275	5.5	Johns Manville

Note.^a100% calcium carbonate natural chalk (CAS# 471-34-1).

^bMuscovite mica.

^cIngredient substituted or eliminated – see text.

TABLE 2  Ready-mix ingredients

Ingredient	Function	Mass used in reformulation (grams)	% by weight	Supplier
Filler
Limestone^a	Filler	5255	81	Science Stuff
Mica^b	Anti-cracking agent	845	13	Zemex Industrial Minerals
Natrosol	Water retention agent	42.25	0.65	Aqualon (Hercules)
Gelvatol 20–30 BP (Polyvinyl alcohol)	Adhesive	52	0.8	Science Laboratories; Alfa Aesar
Troysan CMP-10-Sep^c	Fungicide	—	—
Dowicil	Substitute for Troysan CMP-10-Sep	9.75	0.15	ET Horn Co.
Nalco 71-D5^c	Anti-foaming agent	—	—	—
Chrysotile 7RF9^c	Bulk	—	—	—
Chrysotile 7RF3	Substitute for 7RF9	292.5	4.5	Johns Manville
Ready-mix
Filler	Body	5485	57	—
Elvacet 81–900 (Polyvinyl acetate emulsion)^c	Adhesive	—	—	—
Playamul 104	Substitute for Elvacet 81–900	482	5	Forbo
Benzoflex 50	Plasticizer	31.2	0.3	Velsicol
Nalco 71-D5^c	Anti-foaming agent	6	0.06	Nalco
Water	Solvent	3602.5	37.5	Municipal supply

Note.^a100% calcium carbonate natural chalk (CAS# 471-34-1).

^bMuscovite mica.

^cIngredient substituted or eliminated—see text.

TABLE 3  Distribution of sizes of primary fibers and bundles in historical joint system cement and three samples of Grade 7 chrysotile

Historical joint system cement primary fibers and bundles
	< 5 μ m	5–10 μ m	10–40 μ m	> 40 μ m	all lengths
< 0.25 μ m	0.444	0.041	0.050	0.003	0.537
0.25–0.4 μ m	0.180	0.012	0.018	0.001	0.212
> 0.4 μ m	0.187	0.041	0.024	0.000	0.251
all widths	0.811	0.094	0.092	0.004	1
JM 7RF3 primary fibers and bundles
	< 5 μ m	5–10 μ m	10–40 μ m	> 40 μ m	all lengths
< 0.25 μ m	0.476	0.040	0.020	0.001	0.536
0.25–0.4 μ m	0.162	0.004	0.005	0.001	0.172
> 0.4 μ m	0.268	0.013	0.010	0.001	0.292
all widths	0.906	0.057	0.035	0.002	1
JM 7R05 primary fibers and bundles
	< 5 μ m	5–10 μ m	10–40 μ m	> 40 μ m	all lengths
< 0.25 μ m	0.345	0.026	0.005	0.000	0.377
0.25–0.4 μ m	0.125	0.008	0.002	0.000	0.135
> 0.4 μ m	0.465	0.015	0.008	0.000	0.488
all widths	0.935	0.049	0.016	0.001	1
Brazilian CB7RP primary fibers and bundles
	< 5 μ m	5–10 μ m	10–40 μ m	> 40 μ m	all lengths
< 0.25 μ m	0.364	0.025	0.008	0.000	0.397
0.25–0.4 μ m	0.137	0.007	0.003	0.000	0.146
> 0.4 μ m	0.421	0.025	0.009	0.000	0.456
all widths	0.922	0.057	0.021	0.001	1

FIG. 1  Comparision of chrysotile fiber size distributions for historical joint compound material and fiber from three commercial sources (a) all fiber lengths [above]; (b) fibers longer than 5 um [below].

TABLE 4  Results of performance testing of re-created products

	Joint System Cement		Ready-Mix
Test	Specified	Measured	Specified	Measured
Working consistency (estimated amount of water as a percentage of dry ingredients)	63−67	65	53−56	60
Alkalinity	8.8−9.2	9.1	NS	8.9
Working properties	Plastic, buttery working and free of grit or coarse particles	Smooth, plastic, buttery, no grit or particles, feathers well, sheers well	(M-971) Filler shall be very heavily bodied and possess fair plasticity. It shall be free of any coarse, gritty or undispersed particles.	Heavy-bodied with fair plasticity
			(M971/974) Compound shall be plastic, buttery working and free of any coarse, gritty or undispersed particles	Very smooth, plastic, buttery, little grit or particles, feathers well
Bonding properties	After compound has dried, tape shall delaminate when peeled back	Minimal delamination, approximately 5%−10%	Tape shall show at least 75% fiber tear when delaminated	Minimal delamination, approximately 5%−10%
Crack resistance	At most, only a couple of small cracks in the wedge	No cracks	There shall be no large fissure cracks in the wedge, and no cracks in the thin section	One deep fissure in wedge, no cracks in thin section
Color	Neutral	Off-white	White	White
Viscosity (BU)	NS	565	580 ± 20	580

Note. NS = not specified, BU = Brabender units.