Exploration on the mechanism of failure caused by mold in polyamide materials

doi:10.19491/j.issn.1001-9278.2024.06.015

Abstract

Abstract:

This article focuses on polyamide materials T1 and B1， and uses two types of fungi to conduct anti mold tests on them. It conducts in⁃depth exploration and research on the failure mechanism during the co cultivation process of fungi and polyamide. Through infrared spectroscopy analysis， it was found that mold growth can absorb oxygen from the outside， which can cause the methylene on the polyamide molecular chain to break and react with it to form carbonyl groups， causing changes in the internal structure of the molecule. Through UV spectroscopy and nuclear magnetic resonance analysis， it can be seen that due to the presence of highly reactive methylene structures on the internal molecular chains of polyamide， the color of polyamide and mold will change during the co cultivation process. It will react with the outside world to generate methylene free radicals， further react with oxygen to generate hydrogen peroxide， and then isomerize to generate carbonyl groups. The carbonyl groups then combine with other active groups to produce carbonyl imines. As a result， the conjugated chains on the polyamide molecular chains will increase， and the maximum absorption wavelength will be seen in the visible light region， which is macroscopically manifested as the color change of the polyamide material. Thermogravimetric analysis shows that fungi can obtain nutrients from the surface of polyamide for reproduction， and the surface structure will undergo significant damage and changes. Mechanical performance tests have shown that mold can cause a decrease in the tensile， bending， and impact properties of polyamide materials， and the two types of mold can cause different degrees of attenuation.

Key words: polyamide, mold, chemical reaction, color change, failure mechanism

CLC Number:

TQ322.3

CHEN Ping, LU Dan, LU Guangming, YUAN Chu, YU Ruilei. Exploration on the mechanism of failure caused by mold in polyamide materials[J]. China Plastics, 2024, 38(6): 98-104.

Figures/Tables 10

处理	温度/℃	湿度/%	模拟环境
1^#⁃高温高湿	30	≥95	模拟高温潮湿环境
2^#⁃中温中湿	20	~65	普通环境
3^#⁃低温低湿	10	~35	模拟低温干燥环境
4^#⁃高温低湿	30	~35	模拟高温干燥环境
5^#⁃低温高湿	10	≥95	模拟梅雨季节

Tab.1. Environmental testing conditions and simulated environment for the test setup

样品上霉菌的覆盖情况	等级
不生长	0
痕量生长	1
较少（霉菌数量10 %~30 %）	2
较多（霉菌数量30 %~60 %）	3
很多（霉菌数量60 %~100 %）	4

Tab.2. Growth condition and evaluation of molds on the samples

Fig.1. Mildew situation of polyamide masterbatch T1 and B1 after being cultured with P. funiculosum and A. niger for 21 days under high temperature and high humidity

Fig.2. FTIR of （a） T1 and （b） B1 masterbatch after culturing with P. funiculosum and A. niger for different periods of time

Fig.3. The dissolution of polyamide T1 and B1 in trifluoroacetic acid without yellowing and caused by P. funiculosum and A. niger molds

Fig.4. H1⁃NMR of （a） T1 and （b） B1 masterbatch with P. funiculosum and A. niger cultured for different times；（c） fracture mechanism of polyamide masterbatch structure

Fig.5. UV Visible absorption spectra of （a） T1 and （b） B1 masterbatch cultured with P.funiculosum and A.niger for different times

Fig.6. TG curves of （a） T1 and （b） B1 masterbatch with P. funiculosum and A. niger cultured for different times

Fig.7. Microscopic morphology of the surface of （a） T1 and （b） B1 masterbatch before and after different 21 days with P. funiculosum and A. niger

培养时间/d	测试项目	拉伸强度/MPa		弯曲强度/MPa		弯曲模量/MPa		缺口冲击强度/kJ·m^-2
培养时间/d	测试项目	P.funiculosum	A.niger	P.funiculosum	A. niger	P.funiculosum	A. niger	P. funiculosum	A. niger
0	T1	82	82	118	118	2 812	2 812	9.8	9.8
0	B1	78	78	116	116	2 736	2 736	8.7	8.7
1	T1	76	65	112	105	2 605	2 338	9.1	8.6
1	B1	75	66	113	107	2 623	2 365	8.3	8.2
14	T1	53	47	82	73	1 836	1 675	6.4	5.6
14	B1	61	53	90	84	2 013	1 827	7.2	6.8
21	T1	42	33	71	62	1 608	1 436	4.8	3.7
21	B1	53	41	82	73	1 725	1 665	6.1	5.1

Tab.3. Mechanical properties of T1 and B1 materials cultured for different times with P. funiculosum and A. niger

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