Effects of LiCl on crystallization, thermal, and mechanical properties of polyamide 6/wood fiber composites

Abstract

In the presented study, lithium chloride (LiCl) was used as a modifier to reduce the melting point of polyamide 6 (PA6) and low melting point PA6/wood fiber composites (LPA6/WFC) were prepared with a hot‐press machine. Non‐isothermal crystallization analysis revealed that as little as 3 wt% LiCl decreased the crystallinity of LPA6/WFC from 21.43% to approximately 10% and reduced the melting point of composites from above 220°C to below 200°C, hence the composites can be produced industrially as well as severe degradation of wood fibers can be avoided. Both LiCl and wood fibers increased the glass transition temperature (Tg) of LPA6/WFC, and the Tg of the composites can reach up to 83.2°C, indicating that composites subjected to high temperature circumstances can still retain good dimensional stability and rigidity. In addition, the composites exhibited good mechanical properties, revealed by a flexural strength of the composites of up to 92 MPa. POLYM. COMPOS., 39:E1574–E1580, 2018. © 2017 Society of Plastics Engineers

Preparation and characterization of wood‐fiber‐reinforced polyamide 6–polypropylene blend composites

“…Poplar wood fiber with a high aspect ratio suffered from the heavy shear stress of the composites. Thereby, the poplar wood fiber with high aspect ratios of 15–20 in this study had a reinforcing effect on the composites instead of the filler . This explained the significant increase in the flexural strength.…”

“…The degradation peak temperature ( T p ) of wood fiber decreased from 349.51 to 335.98 °C in the LiCl content range of 0–3.0% [Figure (a)]. This indicated that as a Lewis acid, LiCl promoted the acidolysis of wood at high temperatures . MAPP had no obvious effect on the thermal stability of the composites [Figure (b)].…”

Impact of lithium chloride on the performance of wood fiber reinforced polyamide 6/high‐density polyethylene blend composites

“…The ends of wood fiber with a high aspect ratio can suffer from heavy shear stress of the composites. Therefore, the wood fiber with high aspect ratios of 15 to 20 in this study had a reinforcing effect on the composites rather than the filler . The composites showed an opposite trend in the impact strength in comparison with the flexural properties (Figure D).…”

Impact of lithium chloride and in‐situ grafting on the performance of microcrystalline cellulose‐filled composites based on polyamide 6/high‐density polyethylene

“…In the presence of trace amount of water, lithium cation complexed with O and/or N of PA6, and O of wood fibers, while chloride anion and the adjacent hydrogen gave rise to volatile HCl at high temperature. Then PA6 and wood fibers were further degraded via acidolysis [19]. The increase of T p of PA6 and HDPE in the LiCl content range from 2.0 to 3.0% may be due to the following two reasons: (1) The processing temperature decreased gradually (from 215 to 200 C), suppressed the oxidation and thermal degradation; (2) The higher content of LiCl complexed with not only aforementioned O and N of PA6 and MCC but also O of anhydride groups and DCP, may offset the chain scission of PA6 and HDPE resulting from the grafting side reaction.…”

“…Further increasing the LiCl content from 1.0 to 2.0%, the impact strength sharply decreased. The thermal degradation of MCC promoted by LiCl could reduce the molecular weight of MCC, where could not bear abundant external energy, and give rise to little volatiles in the composites, which acted as the plasticizer [1,19]. Therefore, the degradation of MCC (the peak temperature of thermal degradation decreased by 16 C) (Table 3) may prevail over the positive effect of increasing compatibility.…”