Study of Commercial Additive Effects on the Poly(methyl methacrylate) Exposed to Gamma Irradiation by Viscosimetric Analysis

Aquino, Kátia Aparecida da Silva; Oliveira, Dandara Luz Souza de; Santos, Renata Francisca da Silva; Araújo, Elmo Silvano

doi:10.1590/1980-5373-MR-2023-0382

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Article • Mat. Res. 26 • 2023 • https://doi.org/10.1590/1980-5373-MR-2023-0382 copy

Study of Commercial Additive Effects on the Poly(methyl methacrylate) Exposed to Gamma Irradiation by Viscosimetric Analysis

Authorship SCIMAGO INSTITUTIONS RANKINGS

Poly(methyl methacrylate) (PMMA) is a polymer with applications in the medical and aerospace industries that require resistance to gamma radiation. However, the effects caused by gamma radiation on PMMA properties may make its application in situations of exposure to gamma radiation unfeasible. In this study, the impact of commercial additives on the radiolytic stabilization of PMMA will be studied through viscosimetric assays. In a preliminary trial, additives with different mechanisms of action were tested, and the efficacy of two additives (Tinuvin 770 and Tinuvin 622) hindered amine stabilizers (HAS) types were registered. PMMA films with the additives at different concentrations were exposed to gamma radiation and studied through viscosimetric molar mass and G-value. The Tinuvin 622 at 0.3 wt% showed the best performance in the radiolytic stabilization of p PMMA films at the 20-50 kGy range. Antagonism was observed when Tinuvin 700 and Tinuvin 622 mixture was studied in different proportions. These results show the potential of commercial additives, initially produced for other purposes, in the radiolytic stabilization of PMMA.

Keywords:
PMMA; Tinuvn 770; Tinuvin 622; radiolitic stabilization

Viscosity	Relation	Unit	definition
relative (η_r)	$η_{r} = \frac{η}{η_{0}} \approx \frac{t}{t_{0}}$	dimensionless	Measures how much higher the viscosity of the solution is than the viscosity of the pure solvent. In this case, the densities of the solution and solvent are considered very closed.
specific (η_sp)	$η_{s p} = η_{r} - 1$	dimensionless	Indicates the gain in viscosity caused by the presence of the polymer.
reduced (η_red)	$η_{r e d} = \frac{η_{s p}}{C}$	C^-1 (dL g^-1 for example)	Indicates the gain in viscosity promoted per unit of polymer concentration
inherent (η_inh)	$η_{i n h} = \frac{\ln η_{r}}{C}$	C^-1 (dL g^-1 for example)	It allows both minor and considerable variations in the viscosity of the solution, about that of the solvent, can be expressed on the same axis.

Name	Mathematical model	Intrinsic viscosity[η] from graphic obtention	Ref.
Huggins	η_red = [η]_h + k_h[η]_h^2.C	[η]_h =lim _C→0 (η_red)	Huggins³¹31 Huggins ML. The viscosity of dilute solutions of long-chain molecules. IV. Dependence on concentration. J Am Chem Soc. 1942;64(11):2716-8. http://dx.doi.org/10.1021/ja01263a056. http://dx.doi.org/10.1021/ja01263a056...
Kreamer	η_inh = [η]_k + k_k[η]_k² C	[η]_k=lim _C→0 (η_inh)	Kraemer³²32 Kraemer EO. Molecular weights of celluloses and cellulose derivates. Ind Eng Chem. 1938;30(10):1200-3. http://dx.doi.org/10.1021/ie50346a023. http://dx.doi.org/10.1021/ie50346a023...
Martin	ln(η_red) = ln[η]_m + k_m[η]_mC	[η]_m=lim _C→0 (ln(η_red))	Martin³³33 Martin AF. Toward a referee viscosity method for cellulose. TAPPI. 1951;34:363-6.
Schulz-Blaschke	η_red = [η]_sb + k_sb[η]_sb η_sp	[η]_sb=lim _C→0 (η_red)	Schulz and Blaschke³⁴34 Schulz G, Blaschke F. Eine Gleichung zur Berechnung der Viscositätszahl für sehr kleine Konzentrationen, [Molekulargewichtsbestimmungen an makromolekularen Stoffen, IX. J Prakt Chem. 1941;158(1-8):130-5. http://dx.doi.org/10.1002/prac.19411580112. http://dx.doi.org/10.1002/prac.194115801...

Name	Mathematical model	Ref.	Conditions
Deb-Chatterjee	$[η] = \frac{\sqrt[3]{3 \ln (η_{r}) + 1.5 {(η_{s p})}^{2} - 3 η_{s p}}}{C}$	Deb and Chatterjee³⁵35 Deb PC, Chatterjee SR. Unperturbed dimension of polymer molecules from viscosity measurements. Makromol Chem. 1968;120(1):49-57. http://dx.doi.org/10.1002/macp.1968.021200106. http://dx.doi.org/10.1002/macp.1968.0212...	Equations have been derived under the supposition of the validity of the relationship k_h + k_k = 0.5
Solomon-Ciuta	$[η] = \frac{\sqrt{2 [η_{s p} - \ln (η_{r})]}}{C}$	Solomon and Ciutǎ³⁶36 Solomon OF, Ciutǎ IZ. Détermination de la viscosité intrinsèque de solutions de polymères par une simple détermination de la viscosité. J Appl Polym Sci. 1962;6(24):683-6. http://dx.doi.org/10.1002/app.1962.070062414. http://dx.doi.org/10.1002/app.1962.07006...	The equation is suitable for the polymer/solvent systems with a K_h ≈0.3–0.4
Quian-Qi-Cheng	$[η] = \frac{η_{r s p}}{C \sqrt{η_{r e d}}}$	Qian et al.³⁷37 Qian JW, Qi GR, Cheng RS. Association of ethylene-vinyl acetate copolymer in dilute solutions-i. solvent, concentration and annealing temperature effect. Eur Polym J. 1997;33(8):1263-5. http://dx.doi.org/10.1016/S0014-3057(96)00264-9. http://dx.doi.org/10.1016/S0014-3057(96)...	The equation is suitable for the polymer/solvent systems with a K_h>0.5

Commercial name	Chemical structure	Action mechanism
Tinuvin 328		UV absorber (benzotriazole)
Tinuvin 405		UV absorber (triazine)
Tinuvin 622		Radical Scavenger (HAS Oligomeric)
Tinuvin 770		Radical Scavenger (HAS monomeric)
Irganox 245		Radical Scavenger (hindered phenol stabilizers)
Irgafos 168		secondary antioxidant (phosphites)

Concentration (g/dL)	t(s)	t₀ (s)	η_r	η_sp	η_red (dl/g)	η_inh (dL/g)
0.6	65.74 ±0.02	53.23 ±0.01	1.235 ±0.02	0.235 ±0.02	0.392 ±0.02	0.352 ±0.02
0.8	70.21 ±0.03	53.23 ±0.01	1.319 ±0.03	0.319 ±0.03	0.399 ±0.03	0.346 ±0.03
1.2	79.90 ±0.01	53.23 ±0.01	1.501 ±0.01	0.501 ±0.01	0.417 ±0.01	0.338 ±0.01

Mathematical model	[ƞ] (dL/g)	The slope of the line	R²	Constant value
Huggins	0.368±0.03	0.044	0.99	0.33
Kreamer	0.364±0.02	-0.022	0.99	-0.17
Schultz-Blaschke	0.364±0.01	0.099	0.99	0.27

Dose (kGy)	PMMA
Dose (kGy)	[η] (dL/g)	M_v (g/mol)
0	0.364±0.01	152,526 ±328
10	0.360±0.01	149,994±448
20	0.356±0.03	147,785±427
30	0.331±0.02	133,736±381
40	0.318±0.03	126,356±609
50	0.315±0.01	124,523±726
60	0.309±0.02	121,481±518

dose interval (kGy)	R²	G value
0-20	1.00	0.180
20-50	0.95	0.755

Commercial additive	M_vo (g/mol)	M_v (g/mol)	DI	status
Without (control)	152,526 ±421	138,427±531	0.102	-
Tinuvin 328 (UV)	151,435±538	137,834±328	0.099	disapproved
Tinuvin 405 (UV)	150,354±432	135,896±513	0.106	disapproved
Tinuvin 770 (HAS)	146,368±311	137,043±422	0.068	approved
Tinuvin 622 (HAS)	142,290±486	140,351±326	0.014	approved
Irganox 245 (hindered phenol stabilizers)	149,876±413	135,876±389	0.103	disapproved
Irgafos 168 (secundary antioxidant)	148,679±529	134,569±345	0.105	disapproved

Dose (kGy)	PMMA + Tinuvin 770
	0.1 (wt%)		0.3 (wt%)		0.6 (wt%)		0.9 (wt%)
	[η] (dL/g)	M_v (g/mol)	[η] (dL/g)	M_v (g/mol)	[η] (dL/g)	M_v (g/mol)	[η] (dL/g)	M_v (g/mol)
0	0.364 ±0.02	152,526 ±569	0.356 ±0.03	147,785 ±432	0.354 ±0.02	146,368 ±356	0.360 ±0.01	149,994 ±329
10	0.354 ±0.03	146,368 ±380	0.361 ±0.02	150,626 ±654	0.352 ±0.01	145,268 ±489	0.356 ±0.02	147,627 ±369
20	0.351 ±0.03	145,111 ±397	0.335 ±0.02	135,904 ±549	0.351 ±0.01	144,954 ±420	0.351 ±0.03	144,954 ±461
30	0.327 ±0.01	131,267 ±534	0.329 ±0.01	132,655 ±452	0.346 ±0.02	141,977 ±674	0.340 ±0.02	138,545 ±539
40	0.323 ±0.01	129,421 ±654	0.328 ±0.02	132037,5 ±389	0.335 ±0.03	135,749 ±691	0.334 ±0.03	135,439 ±371
50	0.321 ±0.01	127,886 ±321	0.324 ±0.01	129,421 ±481	0.332 ±0.02	133,891 ±471	0.326 ±0.02	130,959 ±439
60	0.309 ±0.03	121,481 ±486	0.321 ±0.02	127,733 ±529	0.315 ±0.03	124,523 ±721	0.319 ±0.02	126,814 ±530
Dose (kGy)	PMMA + Tinuvin 622
	0.1 (wt%)		0.3 (wt%)		0.6 (wt%)		0.9 (wt%)
	[η] (dL/g)	M_v (g/mol)	[η] (dL/g)	M_v (g/mol)	[η] (dL/g)	M_v (g/mol)	[η] (dL/g)	M_v (g/mol)
0	0.364 ±0.01	152,526 ±381	0.334 ±0.01	135,284 ±345	0.347 ±0.02	142,290 ±568	0.341 ±0.02	139,012 ±456
10	0.362 ±0.02	151,101 ±345	0.331 ±0.02	133,581 ±412	0.343 ±0.03	140,103 ±498	0.338 ±0.01	137,301 ±356
20	0.328 ±0.02	132,346 ±462	0.325 ±0.02	130,343 ±458	0.338 ±0.03	137,456 ±756	0.335 ±0.02	135,594 ±786
30	0.329 ±0.02	132,192 ±534	0.324 ±0.02	129,728 ±547	0.336 ±0.02	136,059 ±867	0.331 ±0.03	133,736 ±685
40	0.319 ±0.02	126,814 ±314	0.323 ±0.01	129,267 ±467	0.334 ±0.01	135,129 ±345	0.329 ±0.02	132,192 ±698
50	0.318 ±0.02	126,356 ±479	0.323 ±0.02	128,807 ±689	0.334 ±0.02	135,284 ±768	0.323 ±0.02	128,960 ±489
60	0.317 ±0.02	125,744 ±564	0.313 ±0.03	123,305 ±789	0.321 ±0.02	128,040 ±789	0.319 ±0.04	126,661 ±546

PMMA+Tinuvin 770
Concentration (wt%)	Dose range (kGy)	R²	G-value	Protection (%)
0.1	0-20	0.91	0.720	00
0.1	20-50	0.98	0.198	74
0.3	0-20	1.00	0.108	40
0.3	20-50	0.97	0.198	74
0.6	0-20	0.97	0.07	60
0.6	20-50	0.98	0.360	53
0.9	0-20	0.98	0.216	00
0.9	20-50	0.99	0.432	43
PMMA+Tinuvin 622
0.1	0-20	0.89	0.899	00
0.1	20-50	0.91	0.252	60
0.3	0-20	0.98	0.252	00
0.3	20-50	0.99	0.054	91
0.6	0-20	0.99	0.234	00
0.6	20-50	0.90	0.072	88
0.9	0-20	1.00	0.162	10
0.9	20-50	0.98	0.216	66

Dose (kGy)	50:50		70:30		30:70
Dose (kGy)	[ƞ] (dL/g)	M_v (g/mol)	[ƞ] (dL/g)	M_v (g/mol)	[ƞ] (dL/g)	M_v (g/mol)
0	0.348 ±0.01	143,386 ±435	0.351 ±0.02	144,640 ±534	0.352 ±0.01	145,582 ±547
10	0.347 ±0.01	142,290 ±445	0.348 ±0.01	143,073 ±435	0.351 ±0.01	144,640 ±324
20	0.338 ±0.02	137,301 ±569	0.346 ±0.02	141,821 ±476	0.347 ±0.02	142,290 ±657
390	0.337 ±0.02	137,145 ±693	0.342 ±0.01	139,012 ±782	0.345 ±0.02	141,664 ±698
40	0.332 ±0.03	134,045 ±634	0.330 ±0.03	132,963 ±645	0.340 ±0.01	138,701 ±723
50	0.322 ±0.01	128,346 ±458	0.296 ±0.03	114,243 ±367	0.332 ±0.03	134,355 ±534
60	0.307 ±0.02	120,117 ±723	0.288 ±0.01	109,913 ±872	0.307 ±0.02	120,117 ±769

Tinuvin 770:Tinuvin 622 proportions	dose range (kGy)	R²	G value	Protection (%)
50:50	0-20	0.94	0.288	00
50:50	20-50	0.92	0.306	59
70:30	0-20	0.99	0.126	30
70:30	20-50	0.91	0.971	00
30:70	0-20	0.96	0.144	20
30:70	20-50	0.95	0.252	67

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