Study on Moisture Absorption and Water Absorption of PMMA Wood-plastic Composites Based on TD-NMR

doi:10.11938/cjmr20233054

Abstract

Abstract:

In this study, time-domain nuclear magnetic resonance (TD-NMR) technology was employed to explore the moisture state and spin-spin relaxation (T₂) characteristics of polymethyl methacrylate (PMMA) wood-plastic composites during the moisture absorption and water absorption process. The moisture resistance and water repellency of PMMA wood-plastic composites were compared and analyzed. The experimental samples were PMMA wood-plastic composite material produced by impregnated methyl methacrylate (MMA) monomer polymerization. Firstly, the NMR T₂ test was carried out on the dry PMMA wood-plastic composite, and then the moisture absorption and water absorption experiments were carried out respectively, and the mass of the specimen and its T₂ signal were measured at intervals. The results showed that the moisture absorption rate and water absorption rate of PMMA wood-plastic composite were lower than those of untreated wood, and PMMA had good moisture resistance and water resistance. When the impregnation concentration of MMA was 100 % and the impregnation time reached 24 h, the moisture absorption rate of wood-plastic composites was lower than 15% under the constant temperature of (40±0.2)℃ and relative humidity of (96.4±0.4)%, and the water absorption rate of water-absorbing specimens at room temperature was lower than 30%. At the same impregnation time, with the increase of impregnation concentration of MMA, the moisture absorption rate and water absorption rate of PMMA wood-plastic composites decreased significantly, and the T₂ peak area decreased gradually. This indicates that the PMMA inside the wood-plastic composite material contributes to preventing water from entering.

Key words: wood-plastic composites, PMMA, TD-NMR, relaxation characteristics, moisture absorption of wood

CLC Number:

ZHAO Wanlei, ZHAO Zhihong, ZHANG Minghui, LIU Wenjing. Study on Moisture Absorption and Water Absorption of PMMA Wood-plastic Composites Based on TD-NMR[J]. Chinese Journal of Magnetic Resonance, 2023, 40(4): 448-461.

Figures/Tables 10

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试件编号	吸湿率/%	T₂(1)/ms	T₂(2)/ms	峰面积A(1)	峰面积A(2)	总面积A(总)
PM#0	19.30	0.36	2.68	0.12	29.52	29.64
PM#6-25	13.23	0.30	2.49	0.23	24.21	24.44
PM#6-50	12.58	0.60	2.47	0.37	22.94	23.31
PM#6-100	8.74	0.20	1.96	0.37	21.37	21.74
PM#12-25	13.03	0.30	2.60	0.22	23.46	23.68
PM#12-50	9.90	-	2.21	-	22.44	22.44
PM#12-100	7.42	0.20	1.95	0.31	18.60	18.91
PM#24-25	13.53	-	2.60	-	24.58	24.58
PM#24-50	9.51	-	1.85	-	17.82	17.82
PM#24-100	6.07	-	1.82	-	17.26	17.26

试件编号	吸水率/%	T₂(2)/ms	T₂(3)/ms	峰面积A(2)	峰面积A(3)	总面积A(总)
PM#0	130.73	4.50	102.34	69.90	13389.10	13459.60
PM#6-25	96.68	3.65	89.09	56.75	10254.02	10310.77
PM#6-50	81.65	3.40	89.07	58.44	8295.25	8353.69
PM#6-100	34.48	2.76	33.70	47.73	4237.27	4280.99
PM#12-25	89.35	3.41	89.07	45.92	7672.14	7718.06
PM#12-50	59.67	3.40	155.52	50.78	5154.88	5205.66
PM#12-100	31.70	2.96	77.53	51.60	2316.82	2368.42
PM#24-25	90.03	3.65	135.10	50.51	7688.59	7739.10
PM#24-50	47.81	2.58	64.47	32.74	5035.80	5068.54
PM#24-100	20.79	2.40	31.14	38.36	2098.09	2136.45