The effect of molecular weight and hydrolysis degree of poly(vinyl alcohol)(PVA) on the thermal and mechanical properties of poly(lactic acid)/PVA blends

Restrepo, Iván; Medina, Carlos; Meruane, Viviana; Akbari-Fakhrabadi, Ali; Flores, Paulo; Rodríguez-Llamazares, Saddys

doi:10.1590/0104-1428.03117

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Original Article • Polímeros 28 (2) • Apr-Jun 2018 • https://doi.org/10.1590/0104-1428.03117 copy

The effect of molecular weight and hydrolysis degree of poly(vinyl alcohol)(PVA) on the thermal and mechanical properties of poly(lactic acid)/PVA blends

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The effect of molecular weights and hydrolysis degrees (HD) of polyvinyl alcohol (PVA) on thermal and mechanical properties and crystallinity of polylactic acid (PLA)/PVA blends was investigated. Blends were prepared by the melt blending method using PLA/PVA ratios: 80/20, 90/10 and 97/3 wt. %. A single glass transition temperatures was observed for all PLA/PVA blends, suggesting the formation of binary compatible blends at concentration range studied. Thermogravimetric analysis results showed a better thermal stability for PLA/PVA blends containing PVA of higher Mw and HD. According to mechanical properties, low quantities of PVA (3 wt. %) do not affect the tensile strength of blends (irrespective of Mw and HD). However, as the PVA content increases, tensile strength tends to lower values, especially for blends with 20 wt.% of PVA, with 98% of HD.

Keywords:
material testing; melt blending; polylactic acid; polyvinyl alcohol; polymer blend

PVA Code	PVA		Sample code for PLA/PVA blends
PVA Code	Range of Mw (g/mol)	HD (%)	80/20 wt.%	90/10 wt.%	97/3 wt.%
1PVA	13000-23000	87-89	1PVA 80/20	1PVA 90/10	1PVA 97/3
2PVA	13000-23000	98	2PVA 80/20	2PVA 90/10	2PVA 97/3
3PVA	31000-50000	87-89	3PVA 80/20	3PVA 90/10	3PVA 97/3
4PVA	31000-50000	98	4PVA 80/20	4PVA 90/10	4PVA 97/3

Sample code	Tg (°C)	Tcc (°C)	Tm1 (°C)	Tm2 (°C)	ΔHcc (J.g^-1)	ΔHm (J.g^-1)	Xc (%)
Pure PLA	61	98	150	169	38	54	58
1PVA	37	___	167	___	___	20	___
1PVA 80/20	42	96	116	124	13	14	19
1PVA 90/10	43	91	114	133	24	22	26
1PVA 97/3	50	95	142	153	39	41	45
2PVA	40	___	210	___	___	66	___
2PVA 80/20	44	99	118	130	13	14	19
2PVA 90/10	42	91	118	136	28	25	30
2PVA 97/3	53	97	143	157	41	49	54
3PVA	44	___	167	___	___	21	___
3PVA 80/20	55	89	111	132	16	15	20
3PVA 90/10	43	92	121	138	27	23	27
3PVA 97/3	50	94	143	157	45	52	57
4PVA	42	___	212	___	___	61
4PVA 80/20	51	91	112	130	14	16	22
4PVA 90/10	42	88	117	136	32	27	32
4PVA 97/3	54	94	149	159	40	47	53

Sample code	TGA	DTG
Sample code	T_5%	T _{on set-1} (°C)	T_max-1 (°C)	WL-1 (%)	T _{On set-2} (°C)	T_max-2 (°C)	WL-2 (%)
Pure PLA	334	284	364	99	____	____	____
1PVA	241	216	306	77	391	426	12
1PVA 80/20	268	191	301	90	381	425	7
1PVA 90/10	280	232	312	92	392	427	5
1PVA 97/3	301	256	353	97	411	420	1
2PVA	186	216	261	69	351	421	15
2PVA 80/20	272	188	305	93	383	428	4
2PVA 90/10	286	231	330	95	406	419	2
2PVA 97/3	301	251	348	97	411	421	1
3PVA	261	221	314	75	391	426	16
3PVA 80/20	275	218	305	88	388	432	7
3PVA 90/10	285	225	322	93	395	422	3
3PVA 97/3	301	241	345	97	406	427	1
4PVA	215	206	260	71	351	416	14
4PVA 80/20	270	220	380	87	390	435	4
4PVA 90/10	288	240	331	94	393	427	3
4PVA 97/3	311	261	356	98	421	431	1

Sample code	Young’s Modulus (GPa)
Sample code	80/20 wt.%	90/10 wt.%	100 wt.%
Pure PLA			4.7
PLA/1PVA	4.3	4.1
PLA/2PVA	2.1	4.0
PLA/3PVA	4.1	4.0
PLA/4PVA	3.0	4.2

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